Measuring device

Abstract

A measurement device that receives quantum entangled light from one or more paths includes: one or more beam splitters that cause interference of quantum entangled light; a plurality of light receiving elements provided corresponding to respective paths branched by a plurality of beam splitters including at least the beam splitter; a branching unit that randomly disperses photons in the plurality of light receiving elements; and a measuring instrument that detects respective detection timings of photons in the plurality of light receiving elements.

Description

Technical Field

[0001] The present disclosure relates to a measuring device. Background Art

[0002] In recent years, research and technological development using the correlation generated between multiple quantum states (called quantum entanglement) are being actively carried out. Fields where the use of quantum entanglement plays an important role include quantum communication and quantum sensing. By using quantum entanglement, it is expected that quantum communication for connecting quantum computers and quantum sensing can be achieved with higher sensitivity than existing technologies. Examples of devices related to quantum entanglement include light detection systems for bell-shaped measurements intended to be applied to quantum communication (for example, Patent Document 1). In order to use quantum entanglement as an asset, it is necessary to detect that multiple quantum states are in an entangled state (bell-shaped state) by measurement. In quantum communication, the light detection system used to perform this measurement (bell-shaped measurement) is an indispensable component.

[0003] Citation List

[0004] Patent Literature

[0005] Patent Document 1: JP 2012-004956 A Summary of the invention

[0006] Technical issues

[0007] When using quantum entanglement, it is required to efficiently generate quantum entangled states. However, current devices cannot efficiently generate quantum entanglement. It is necessary to continuously supply quantum entanglement in order to use it for calculation and sensing. In the supply of quantum entanglement, the number of times entanglement is generated per unit time is important. However, in existing devices, the focus is on the success probability of bell measurement for detecting quantum entanglement, and, for example, there are problems with the number of times entanglement is generated per unit time.

[0008] Therefore, the present disclosure proposes a measurement device that can efficiently generate quantum entanglement.

[0009] It is noted that the above-mentioned problem or purpose is only one of the problems or purposes that can be solved or achieved by the various embodiments disclosed in this description.

[0010] Solution to the problem

[0011] In order to solve the above problems, according to one aspect of the present disclosure, a measuring device for receiving quantum entangled light from one or more paths is provided, and the measuring device includes: one or more beam splitters, which cause quantum entangled light to interfere; a plurality of light receiving elements, which are arranged corresponding to the corresponding paths branched out by a plurality of splitters including at least a beam splitter; a branching unit, which randomly disperses photons in the plurality of light receiving elements; and a measuring instrument, which detects the corresponding detection timing of the photons in the plurality of light receiving elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a diagram illustrating an example of the quantum entangled light detection system of the present embodiment.

[0014] Figure 2 is a flowchart illustrating the method of quantum entangled light detection according to the present embodiment.

[0015] Figure 3 It is a diagram illustrating an example of application of the present embodiment to quantum communication.

[0016] Figure 4 is a diagram illustrating an example of application of the present embodiment to quantum sensing.

[0017] Figure 5 is a diagram illustrating an example of a method for implementing the present embodiment in the case of polarization encoding.

[0018] Figure 6 is a diagram illustrating an example of a method for implementing the present embodiment in the case of path coding.

[0019] Figure 7 is a flow chart illustrating a method for photon introduction in polarization encoding.

[0020] Figure 8 is a flow chart illustrating a method of photon introduction in path encoding.

[0021] Fig. 9 is a flow chart illustrating a method of light detection.

[0022] Fig.10 is a diagram illustrating a specific example of isolation.

[0023] Fig.11 is a diagram illustrating an example of a device that sends a timing clock to the outside of a detector.

[0024] Fig.12 is a diagram illustrating an example of a device that sends a timing clock to the outside of a detector.

[0025] Fig.13 is a flow chart illustrating a method for selecting a method after the diagram.

[0026] Fig.14 is a diagram illustrating a modified example of a photon detector (group) and a post-selection functional unit.

[0027] Fig.15 is a diagram illustrating a modified example of a photon detector (group) and a post-selection functional unit.

[0028] Fig.16 is a diagram illustrating an example of the configuration of the present embodiment in the case of polarization encoding.

[0029] Fig.17 is a flow chart illustrating a method for photon introduction in polarization encoding.

[0030] Fig.18 is a diagram illustrating an example of the configuration of the present embodiment in the case of path encoding.

[0031] Fig.19 is a flow chart illustrating a method of photon introduction in path encoding.

[0032] Fig. 20 is a flow chart illustrating a post-selection method in the case of quantum communication.

[0033] Fig.21 is a diagram illustrating an example of the configuration of the present embodiment in the case of photon presence / absence encoding.

[0034] Fig. 22 is a flow chart illustrating a method of photon introduction in photon presence / absence encoding.

[0035] Fig.23 is a diagram illustrating an example of the configuration of the present embodiment in the case of time encoding.

[0036] Fig.24 is a flow chart illustrating a method of photon introduction in time encoding.

[0037] Fig.25 is a diagram illustrating an example of the configuration of quantum sensing of the present embodiment.

[0038] Fig.26 is a flow chart illustrating a method of post-selection in the context of quantum sensing.

[0039] Fig. 27 is a diagram illustrating a first application example of quantum sensing.

[0040] Fig.28 is a diagram of a second application example of quantum sensing.

[0041] Fig.29 is a diagram of a third application example of quantum sensing.

[0042] Fig.30 is a diagram of a fourth application example of quantum sensing.

[0043] Fig.31 is a diagram illustrating a first configuration example of a light branching unit and a photodetector.

[0044] Fig.32 is a diagram illustrating a second configuration example of the light branching unit and the photodetector.

[0045] Fig.33 is a diagram illustrating another configuration example of the photodetector.

[0046] Fig.34 is a diagram illustrating an example of photodetector performance in a single element.

[0047] Fig.35 is a diagram illustrating an example of the behavior of light detection.

[0048] Fig.36 is a diagram illustrating an example of a case where light can be detected.

[0049] Fig.37 is a diagram illustrating an example of a case where light cannot be detected.

[0050] Fig.38 is a diagram illustrating an example of a model of light detection.

[0051] Fig.39 is a diagram illustrating an example of deriving a light detection rate.

[0052] Fig.40 is a diagram illustrating an example of a model of light detection in a case where a photodetector includes a plurality of elements.

[0053] Fig.41 is a diagram illustrating an example of a model of light detection in a case where a photodetector includes a plurality of elements.

[0054] Fig.42 is a diagram illustrating an example of scattered light and detection by multiple elements.

[0055] Fig.43 is a diagram illustrating an example of calculation of the maximum light detection rate with respect to the number of elements.

[0056] Fig.44 is a diagram illustrating an example of calculation of the maximum light detection rate with respect to the number of elements.

[0057] Fig.45 is a hardware configuration diagram illustrating an example of a computer that realizes the functions of the information processing apparatus. DETAILED DESCRIPTION

[0058] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0059] One or more embodiments (examples and modifications) described below can be implemented independently of each other. On the other hand, at least some of the multiple embodiments described below can be appropriately combined with at least some of the other embodiments. Multiple embodiments may include novel features that are different from each other. Therefore, multiple embodiments can help solve different purposes or problems, and can play different effects.

[0060] Furthermore, the present disclosure will be described according to the order of the following items.

[0061] 1. Example

[0062] 1-1. Overview of this embodiment

[0063] 1-2. Method for realizing quantum entangled light detection

[0064] 1-3. Application examples of this embodiment

[0065] 1-4. Example of a method for implementing the present embodiment due to differences in qubit encoding

[0066] 1-5. Method for implementing photon introduction in polarization encoding

[0067] 1-6. Method for implementing photon introduction in path encoding

[0068] 1-7. Method for realizing photon detection

[0069] 1-8. Methods for achieving isolation

[0070] 1-9. Example of method for realizing photodetector

[0071] 1-10. Methods for implementing post-selection

[0072] 1-11. Configurations that can be taken by the corresponding functional units of light detection and post-selection

[0073] 1-12. Configuration and processing examples in polarization encoding

[0074] 1-13. Configuration and processing examples in path coding

[0075] 1-14. Example of post-selection in quantum communication

[0076] 1-15. Configuration and processing examples in photon presence / absence encoding

[0077] 1-16. Configuration and processing examples in time coding

[0078] 1-17. Configuration examples in quantum sensing

[0079] 1-18. Examples of post-selection in quantum sensing

[0080] 1-19. Application examples of quantum sensing

[0081] 1-19-1. First application example (two-photon excitation / second harmonic generation microscopy)

[0082] 1-19-2. Second application example (near-infrared fluorescence imaging)

[0083] 1-19-3. Third application example (near infrared light brain measurement equipment)

[0084] 1-19-4. Fourth application example (flow cytometer)

[0085] 1-20. Configuration example of optical branching unit and photodetector

[0086] 1-20-1. First Configuration Example (Multiple Elements)

[0087] 1-20-2. Second Configuration Example (Array Element)

[0088] 1-20-3. Another configuration example (single array type detector)

[0089] 1-21-4. Photodetector performance

[0090] 2. Modify the example

[0091] 3. Conclusion

[0092] 4. Effects according to the present disclosure

[0093] 5. Hardware Configuration

[0094] <1. Example>

[0095] <1-1. Overview of this embodiment>

[0096] In recent years, research and technology development using correlations generated between multiple quantum states (called quantum entanglement) are actively underway. As fields where the use of quantum entanglement plays an important role, there are quantum communication and quantum sensing, and both require efficient generation of quantum entangled states.

[0097] One of the problems in the formation of quantum entanglement is the bell measurement using light. This is a measurement used to determine the correlation between quantum states of a quantum system that is expected to form quantum entanglement. Therefore, efficiently obtaining a successful event of bell measurement is a necessary condition for the efficient formation of quantum entanglement. How to encode the quantum state using light affects the |0> or |1> of the quantum bit that determines the success of the bell measurement. Depending on the encoding method, there are the following characteristics and problems.

[0098] Table 1

[0099]

[0100] Efficient generation of quantum entanglement requires the elimination of erroneous measurements. Since the biggest factor leading to erroneous measurements is the loss of photons, the encoding of the desired qubit is a method that can determine the photon loss event with high probability. In the encoding method based on the presence or absence of photons and time, since the absence of photons on the path is assigned to the qubit |0> (for a certain time), there is a problem of distinguishing it from the loss of photons. The path-based method can determine the loss with high accuracy, but since it is necessary to set up a detection element in each path, the method may be limited in scale. Methods using polarized light are also conducive to loss determination, but some photodetectors have polarization dependence, so a device configuration that maximizes detection efficiency is required.

[0101] Depending on which of these encoding methods is adopted, the requirements for the photodetector change. Therefore, it is necessary to construct the measurement system taking into account the characteristics of the encoding method and the photodetector. The superconducting nanowire detector (SNSPD), which is currently regarded as the most practical photodetector, has polarization dependence in detection efficiency, and it is necessary to align the polarization direction of light with the direction of the detector to maximize the detection efficiency. In addition, it is necessary to cool the detection element to a superconducting state, and there are limitations in amplification, such as the use of multiple elements and detectors. Photodiodes, another option for photodetectors, have no polarization dependence in detection efficiency, can be operated at room temperature and are inexpensive, so they have advantages in scalability. However, the detection efficiency is lower than that of the SNSPD, and a large number of measurement attempts are required until the bell-shaped measurement is successful.

[0102] (Means of implementation)

[0103] The quantum entangled light detection system of this embodiment is a two-photon interference detection system capable of using a high-rate quantum entangled light source using quantum bit encoding of polarized light or path, and includes a mechanism for eliminating erroneous measurements ((a) and (b) below).

[0104] (a) a detector comprising a plurality of elements capable of detecting photon detection timing, or a detector system comprising a collection of a plurality of detectors as individual photodetectors included in the system;

[0105] (b) Post-selection is performed by making it possible to perform bell-shaped measurement by detecting photon detection times of all light detection elements currently included and using the photon detection times.

[0106] Figure 1 is a diagram illustrating an example of the quantum entangled light detection system of the present embodiment. Figure 1 A detection system 1 to which polarization qubit encoding is applied is illustrated as an example of the quantum entangled light detection system of the present embodiment.

[0107] (Effect)

[0108] According to the present embodiment, by using a detector including a plurality of elements or a detector system including a collection of a plurality of detectors as each single photodetector, it is possible to increase the number of quantum entanglement attempts per unit time. In addition, by utilizing a quantum bit encoding capable of detecting light loss and post-selection, it is possible to reduce unexpected errors due to optical loss and noise. Therefore, by using the quantum entanglement light detection system of the present embodiment, the efficiency of quantum entanglement formation per unit time can be improved.

[0109] The outline of the present embodiment has been described above, and the present embodiment will be described in detail below. Hereinafter, the quantum entangled light detection system of the standard embodiment is simply referred to as a detection system. Note that the detection system may be referred to as a measurement device or the like.

[0110] <1-2. Method for realizing quantum entangled light detection>

[0111] First, a method for realizing quantum entangled light detection will be described. Figure 2 is a flowchart illustrating the method of quantum entangled light detection of this embodiment. For example, the detection system 1 performs the following steps: Figure 2 The processing shown in steps S1 to S5 in FIG. 10A and 10B are as follows. The outline of each block will be described below.

[0112] (Photon introduction: corresponding to steps S1 to S3)

[0113] The detection system 1 introduces the input quantum entangled light into the photon detector. The photon introduction of this embodiment includes any one of the following quantum bit encoding methods.

[0114] Polarization encoding

[0115] Path encoding

[0116] Configuration examples for implementing each of the above methods will be described in <1-4. Examples of methods for implementing the present embodiment due to differences in qubit encoding>. In addition, each of the above implementation methods is described in <1-5. Methods for implementing photon introduction in polarization encoding> or <1-6. Methods for implementing photon introduction in path encoding>. However, as long as the present embodiment is applicable, other encoding methods of qubits not explicitly described below can be applied to the quantum entangled light detection system of the present embodiment.

[0117] (Photon detection: corresponding to step S4)

[0118] The detection system 1 detects quantum entangled light. Specific implementation methods are described in <1-7. Method for implementing photon detection>, <1-8. Method for implementing isolation>, and <1-9. Example of a method for implementing a photodetector>.

[0119] (Later selection: corresponding to step S5)

[0120] The detection system 1 performs post-selection, that is, only the events in which two light beams are detected simultaneously are selected from the information of photon detection. In addition, when quantum communication is performed, the bell state between the nodes is determined by this box. The specific implementation method is shown in <1-10. Method for implementing post-selection>. The configuration that can be taken by each functional unit of light detection and post-selection is described in <1-11. Configuration that can be taken by the corresponding functional unit of light detection and post-selection>.

[0121] <1-3. Application Examples of the Present Embodiment>

[0122] Figure 3 is a diagram illustrating an example of application of the present embodiment to quantum communication. The present embodiment provides a method for performing bell-shaped measurement when it is desired to form quantum entanglement between quantum memories between remote nodes. Note that a detailed description, examples, etc. of this point will be described later.

[0123] Figure 4 : is a diagram illustrating an example of application of the present embodiment to quantum sensing. The present embodiment provides a two-photon quantum interference method for sensing using a photon pair in a quantum entangled state. Note that a detailed description, examples, etc. of this point will be described later.

[0124] <1-4. Example of a method for implementing the present embodiment due to differences in qubit encoding>

[0125] Figure 5 is a diagram illustrating an example of a method for implementing the present embodiment in the case of polarization encoding. Figure 6is a diagram illustrating an example of a method for implementing the present embodiment in the case of path coding. Note that the description in the diagram is as follows.

[0126] U X： Unitary conversion of the light input from source X

[0127] U X,Y : Unitary transformation of light input from source X and path Y

[0128] BS:beam splitter

[0129] PBS: Polarization Beam Splitter

[0130] Wavelength conversion: wavelength conversion of input light

[0131] Wavelength selection: selectively transmit converted wavelengths

[0132] Photodetectors: single photon or photon count detectors

[0133] Post-selection: simultaneous detection of input photons from two light sources and bell-shaped state determination

[0134] Figure 5 and Figure 6 The detection systems 1 and 1A shown in the figure are systems for receiving quantum entangled light from one or more paths, the systems including one or more BSs for causing interference of the quantum entangled light, light receiving elements arranged corresponding to corresponding paths branched from a plurality of splitters (BS and / or PBS) including at least the above-mentioned BSs, and a measuring instrument for detecting corresponding detection timing of photons in the plurality of light receiving elements.

[0135] Specifically, Figure 5 The detection system 1 shown in is a system for receiving quantum entangled light, which includes a beam splitter that causes quantum entangled light to interfere, a plurality of PBSs that branch the quantum entangled light in polarization states after interference through the BS, light receiving elements arranged corresponding to the corresponding paths branched from the PBS, and a measuring instrument that detects the corresponding detection timing of photons in the plurality of light receiving elements.

[0136] also, Figure 6 The detection system 1A shown in the figure is a system for receiving quantum entangled light from multiple paths, the system including multiple BSs that cause quantum entangled light to interfere, light receiving elements arranged corresponding to the corresponding paths branched from the BSs, and a measuring instrument for detecting the corresponding detection timing of photons in the multiple light receiving elements.

[0137] <1-5. Method for implementing photon introduction in polarization encoding>

[0138] Figure 7 is a flow chart illustrating a method for introducing photons in polarization encoding. For example, the detection system 1 performs the following steps: Figure 7 The processing shown in steps S11 to S15 in the flowchart can be described below. The connection of the components that implement the functions of each block can be achieved through free space, optical cable or optical circuit.

[0139] (Wavelength conversion and wavelength selection: corresponding to step S11)

[0140] The detection system 1 can perform wavelength conversion on the input light at any position before the photon interference only when the polarization state of the input light does not change. Examples of wavelength conversion include wavelength conversion using the secondary nonlinear optical effect of bulk crystals as described below, or methods of performing wavelength conversion in waveguides using these crystals.

[0141] ·LN:LiNbO3

[0142] LT: LiTaO3

[0143] KTP: KTiOPO4

[0144] PPLN: Periodically poled lithium niobate

[0145] PPMgLN: Periodically poled magnesium oxide doped lithium niobate

[0146] (Unitary conversion of input light: corresponding to step S12)

[0147] The detection system 1 performs a unitary transformation to cause two input beams to interfere with each other via a beam splitter (BS). The mechanism for the unitary transformation can be installed on either or both of the two optical paths. For each type of transformation, examples include:

[0148] Phase shift: This is achieved by adjusting the optical path length through a phase shifter, adjusting the length of the optical cable, or adjusting the delay through a mirror.

[0149] • Base conversion: This is achieved by converting the polarization of light from vertical or horizontal to clockwise or counterclockwise (or the reverse) by a wave plate.

[0150] Due to the situation of two-photon interference, the wavelength after conversion can be shorter or longer than the input light. As a method for converting the input light into a short wavelength, there is second harmonic generation (SHG) or sum frequency generation (SFG). As a method for converting the input light into a long wavelength, there is difference frequency generation (DFG).

[0151] After wavelength conversion, a mechanism for selecting the wavelength of the light can be introduced. Examples include implementation through a high pass filter (HPF), a low pass filter (LPF), or a band pass filter (BPF).

[0152] (Interference of input photons: corresponding to step S13)

[0153] The detection system 1 makes two input beams interfere with each other through a two-input / two-output BS and makes it impossible to determine from which input path the beam arrives. Examples include implementations through a BS that randomly divides the light into two paths or a PBS (Polarization BS) that installs wave plates before and after the four inputs and outputs.

[0154] (Branching by polarization: corresponding to step S14)

[0155] The detection system 1 branches two photons that interfered through the previous BS / PBS in terms of polarization state. Examples include implementations using PBS.

[0156] (Branch for input photons: corresponding to step S15)

[0157] The detection system 1 performs this function. Photons branched by polarization are further branched or diffused to branch input photons. Examples include a beam splitter, a lens that diffuses the light, or a combination thereof.

[0158] <1-6. Method for implementing photon introduction in path encoding>

[0159] Figure 8 is a flow chart illustrating a method for introducing photons in path encoding. For example, detection system 1A performs Figure 8 The processing shown in steps S21 to S23 in the flowchart. Unless otherwise specified, the components that perform the functions of the blocks and the connections of the components are similar to the configuration described in <1-5. Method for implementing photon introduction in polarization encoding>. Each block of the flowchart will be described below.

[0160] (Wavelength conversion and wavelength selection: corresponding to step S21)

[0161] Wavelength conversion can be Figure 8 The wavelength after conversion can be shorter or longer than the input light. In addition, a mechanism for selecting the wavelength of light to be input to the photodetector after wavelength conversion can be introduced.

[0162] (Unitary conversion of input light: corresponding to step S22)

[0163] The detection system 1A performs a unitary transformation to make the two input beams interfere with each other at BS. The mechanism for unitary transformation can be installed on either or both of the two optical paths.

[0164] (Interference of input photons: corresponding to step S23)

[0165] The detection system 1A, through a two-input / two-output BS, causes the two input beams to interfere with each other and makes it impossible to determine from which input path the beam arrived. Examples include a BS that randomly splits the light into two paths.

[0166] <1-7. Method for realizing photon detection>

[0167] Fig. 9 is a flow chart illustrating a method of light detection. For example, detection systems 1 and 1A perform Fig. 9 The processing shown in steps S31 to S37 in the flowchart will be described below. Each block of the flowchart will be described below.

[0168] (Wavelength conversion and wavelength selection: corresponding to step S31)

[0169] The detection systems 1 and 1A can perform wavelength conversion on the input light at any position before light detection to improve the detection efficiency of the input light or enable the input light to be detected. Examples include a method for converting light such as a communication wavelength band that cannot be detected by Si into a wavelength that can be detected by Si when the light receiving element of the photodetector is Si. As a wavelength conversion method in this case, there is SHG or SFG described in <1-5. Method for realizing photon introduction in polarization encoding>.

[0170] (Light branching: corresponding to step S32)

[0171] Detection systems 1 and 1A direct input light into multiple spatially separated elements of a photodetector. Examples include methods where multiple optical fibers are spliced ​​or branched through waveguides of an optical circuit.

[0172] (Condensation: corresponding to step S33)

[0173] A mechanism for focusing the light input to the photodetector may be introduced. Examples include lenses that focus the light on multiple elements of the photodetector, or on-chip lenses formed on each element.

[0174] (Isolation: corresponding to step S34)

[0175] An isolation mechanism may be introduced to prevent crosstalk of input light between elements of the photodetector. The implementation method will be described in <1-8. Method for Implementing Isolation> below.

[0176] (Light detection: corresponding to step S35)

[0177] The detection systems 1 and 1A detect input light. At this time, the detection systems 1 and 1A may perform detection using a single photon detection unit or may perform detection using a photon number detection unit. Any of the detection units may be a detector including a plurality of light detection elements, or may be a detector system including a plurality of independent detectors.

[0178] (Photodetection time acquisition: corresponding to steps S35 and S36)

[0179] In the case where the information of light detection is output to the signal processing device selected after execution through digital communication, the detection systems 1 and 1A obtain the time when light is detected. Examples include a method of using a common timing clock in all photodetectors included in the detection systems 1 and 1A and obtaining the time from a counter associated with the clock.

[0180] (Output of light detection information: corresponding to step S37)

[0181] The detection systems 1 and 1A output information of light detection to a signal processing device selected after execution. Examples of the case where information is output by digital signals include a method of outputting the time when light is detected and the address of an element as a data packet. Examples of the case where information is output from analog signals include a method of outputting the intensity of a light reception signal of an element to the outside via an analog cable or the like in a form that can uniquely specify all elements included in the detection systems 1 and 1A.

[0182] <1-8. Methods for achieving isolation>

[0183] Examples include pixel structures for preventing input light from leaking from adjacent elements, and methods of providing light-shielding walls between elements. Fig.10 is a diagram illustrating a specific example of isolation. Fig.10 In the example shown in , a structure is introduced in which a semiconductor substrate on which an avalanche photodiode element is formed is insulated and separated from other adjacent pixels. Note that the meanings of the reference numerals in the drawings are as follows.

[0184] 11: sensor chip, 12: pixel array unit, 13: bias voltage application unit, 21: single photon avalanche diode (SPAD) pixel, 31: SPAD element, 32: p-type metal oxide semiconductor field effect transistor (MOSFET), 33: complementary metal oxide semiconductor (CMOS) inverter, 41: sensor substrate, 42: sensor side wiring layer, 43: logic side wiring layer, 51: N well, 52: P-type diffusion layer, 53: N-type diffusion layer, 54: hole accumulation layer, 55: pinning layer layer), 56: high concentration P-type diffusion layer, 57: avalanche multiplication region, 61: metal film, 62: insulating film, 63: pixel separation unit, 71 to 73: contact electrode, 74 to 76: metal wiring, 77 to 79: contact electrode, 80 to 82: metal pad, 91 to 93: electrode pad, 94: insulating layer, 95 to 100: contact electrode, 101 to 103: metal pad electrode.

[0185] <1-9. Example of method for realizing photodetector>

[0186] Fig.11 and Fig.12 are diagrams each illustrating an example of a device that sends a timing clock to the outside of a detector. Fig.11 is an example of a detector system (hereinafter also simply referred to as a detector) in which a plurality of detectors are integrated, and Fig.12 is an example of a detector comprising multiple elements. Fig.11 and Fig.12 Illustration of how time is synchronized between detectors.

[0187] As a means of synchronizing the time between the detectors, configurations other than the above configurations may also be applied. For example, a function that requires preliminary preparations such as training or calibration before measurement may be introduced.

[0188] The detector or detector element may be configured to detect a single photon or a number of photons. In addition, there may be differences in characteristics (e.g., material, composition, and shape) between multiple detectors. In addition, the detector may have a function for improving or changing the characteristics of the detector (e.g., a cooling function and a bias variable function).

[0189] <1-10. Method for implementing post-selection>

[0190] Fig.13 is a flowchart of the method selected after the diagram is shown. Each block of the flowchart will be described below. For example, detection system 1 and 1A perform Fig. 9 The following processing is performed by a signal processing device (computer) included in the detection systems 1 and 1A.

[0191] (Reception of light detection information: corresponding to step S41)

[0192] The signal processing device selected after execution receives light detection information from the photodetector. Examples include a method of receiving the time of light detection and the address of the element as a data packet through a digital signal, and a method of receiving the intensity of the output signal in a form that can specify the element address through an analog signal.

[0193] (Determination of simultaneous detection of photons: corresponding to step S42)

[0194] The signal processing device determines whether the photons have been detected simultaneously (whether two photons have been detected within the time resolution of the detector). Examples of cases where the photon detection information is received as a digital signal include methods for determining simultaneous detection based on time information of the light detection included in the data packet. Examples of cases where the information is received as an analog signal include methods for performing a balance type measurement to calculate the difference between the outputs of different elements in the signal processing device and determining simultaneous detection.

[0195] (Notification of simultaneous detection: corresponding to step S46)

[0196] Examples of notifying the user of the simultaneous detection information of the success of the simultaneous detection include a method of notifying an external device via the Internet, a local area network (LAN), etc., and a method of notifying software in a signal processing device after execution via an application program interface.

[0197] (Confirmation of bell-shaped state: corresponding to step S44)

[0198] When the present embodiment is used for quantum communication, in order to form a quantum entangled state, a bell state is determined. Examples of implementation methods include a method of determining which of the four bell states exists from the address of the element that detects light. Note that multiple entanglements such as a GZH state and a cluster state can be used as variants of the quantum entanglement to be formed.

[0199] (Notification of bell-shaped state: corresponding to step S45)

[0200] The determined bell state is notified to the node that desires to form quantum entanglement. Examples include notification to external devices via the Internet, LAN, etc.

[0201] <1-11. Configurations that can be taken by corresponding functional units of light detection and post-selection>

[0202] As a functional unit for photon detection and post-selection, various configurations can be adopted. Fig.14 and Fig.15: is a diagram illustrating a modified example of a photon detector (group) and a post-selection functional unit. For example, the photon detector (group) and the post-selection functional unit may be mixed and mounted on the same chip, or may be divided and mounted on different chips and bonded. In addition, the photon detector (group) and the post-selection functional unit may be made into different packages and delivered. In addition, communication may be performed between a plurality of photon detectors (groups). (For example, sharing of correction information, information about detection, etc.)

[0203] <1-12. Configuration and processing examples in polarization encoding>

[0204] The following will refer to Fig.16 and Fig.17 Describes configuration and processing examples in polarization encoding. Fig.16 is a diagram illustrating an example of the configuration of the present embodiment in the case of polarization encoding. Fig.17 is a flow chart illustrating a method of photon introduction in polarization encoding. Note that descriptions of points similar to those described above will be appropriately omitted.

[0205] First, refer to Fig.16 A configuration example of the detection system 1B in polarization encoding is described. Fig.16 The detection system 1B shown in FIG. 1 receives quantum entangled light from one or more paths. For example, the detection system 1B has a Figure 5 In the detection system 1 shown in FIG. 1B , a light branching unit is arranged before each light detection unit and a processing unit for wavelength conversion + wavelength selection is arranged before the beam splitter. In the detection system 1B , a first processing unit 2a and a second processing unit 3a corresponding to a path starting from a quantum entangled light source a and a first processing unit 2b and a second processing unit 3b corresponding to a path starting from a quantum entangled light source b are arranged before the beam splitter 4.

[0206] Note that, without particularly distinguishing the first processing unit 2a, the first processing unit 2b, etc., they are collectively referred to as the first processing unit 2. In addition, without particularly distinguishing the second processing unit 3a, the second processing unit 3b, etc., they are collectively referred to as the second processing unit 3.

[0207] In addition, the detection system 1B includes a beam splitter 4, and the detection system 1B includes two polarization beam splitters 5a and 5b, four light branching units 6a, 6b, 6c and 6d, four photodetectors 7a, 7b, 7c and 7d, and a post-selection 8. Note that, in the case where the polarization beam splitters 5a and 5b, etc. are not particularly distinguished, they are collectively referred to as polarization beam splitters 5. In addition, in the case where the light branching units 6a, 6b, 6c, 6d, etc. are not particularly distinguished, they are collectively referred to as light branching units 6. In addition, in the case where the photodetectors 7a, 7b, 7c, 7d, etc. are not particularly distinguished, they are collectively referred to as photodetectors 7.

[0208] Fig.16 The detection system 1B shown in the figure includes a beam splitter 4, photodetectors 7 arranged corresponding to corresponding paths branched out by the beam splitter 4 and the polarization beam splitter 5, multiple light branching units 6 that branch light to introduce it into each of the multiple photodetectors 7, and post-selection 8 for detecting corresponding detection timing of photons in the multiple photodetectors 7.

[0209] The first processing unit 2 performs processing on the quantum entangled light before branching by the beam splitter 4. The first processing unit 2 performs at least one of wavelength conversion or wavelength selection on the quantum entangled light. The second processing unit 3 performs processing on the quantum entangled light before branching by the beam splitter 4. The second processing unit 3 performs unitary conversion.

[0210] The beam splitter 4 causes quantum entangled light to interfere. For example, the beam splitter 4 is an optical element that divides incident light into two beams at a predetermined division ratio. For example, the polarization beam splitter 5 is an optical element that separates incident light into S-polarized light and P-polarized light. The photodetector 7 is provided corresponding to the corresponding paths branched from the beam splitter 4 and the polarization beam splitter 5. The post-selector 8 detects the corresponding detection timing of photons in the plurality of photodetectors 7.

[0211] The light branching unit 6 branches light to be introduced into each of the plurality of photodetectors 7. The light branching unit 6 is an element that branches or diffuses light to be introduced into the photodetector 7. Note that a detailed example of the configuration of the light branching unit 6 will be described later.

[0212] here, Fig.16The type of line to be connected between the components in indicates the connection mode between the components. The connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by an optical fiber. For example, the solid line between the quantum entangled light sources a and b and the first processing unit 2 indicates that the light from the light source is input (incident) to the detection system 1 through the optical fiber. As described above, in the case where the detection systems 1, 1A and 1B, etc. are applied to quantum communication, the light from the quantum entangled light source is introduced into the system through the optical fiber. It is noted that, without specifically distinguishing between the detection systems 1, 1A and 1B, etc., they are collectively referred to as the detection system 1.

[0213] As described above, in the case where the detection system 1B is applied to quantum communication, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by optical fiber. Note that, in the case where the detection system 1B is applied to quantum sensing described later, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by either optical fiber or free space.

[0214] In addition, the connection corresponding to the dotted line between the first processing unit 2 and the photodetector 7 is realized by any one of an optical fiber, a waveguide in an optical circuit, and free space. As mentioned above, the path for transmitting light between the components in the detection system 1 can be any one of an optical fiber, a waveguide in an optical circuit, and free space.

[0215] In addition, the connection corresponding to the single-dot chain line between the photodetector 7 and the post-selection 8 is realized by any signal transmission path according to the method for realizing the post-selection. As described above, according to the method for realizing the post-selection 8, the path for introducing the detection signal from the photodetector 7 in the detection system 1 to the post-selection 8 can be any signal transmission path.

[0216] Next, we will refer to Fig.17 The following describes a processing example of the detection system 1B. The detection system 1B performs the processing shown in steps S51 to S55. In the introduction of photons in polarization encoding, for example, two quantum entangled light sources a and b are input at Fig.16 The light in the overlapping state of the two pulses is shown below each light source.

[0217] The detection system 1B performs wavelength conversion and wavelength selection (step S51). The processing of step S51 is the same as Figure 7 For example, in the detection system 1B, the first processing unit 2 performs the processing of step S51. Note that, Figure 7 As shown in the brackets of step S11 in FIG. 1 , wavelength conversion and wavelength selection are arbitrary processes and may be performed or not performed as required. In addition, the detection system 1B performs unitary conversion of the input light (step S52). The processing of step S52 is the same as Figure 7For example, the detection system 1B executes the processing of step S52 through the second processing unit 3 .

[0218] Then, the detection system 1B performs interference of the input photons (step S53). The processing of step S53 is the same as Figure 7 For example, the detection system 1B performs the processing of step S53 through the beam splitter 4. Then, the detection system 1B performs branching by polarization (step S54). The processing of step S54 is the same as Figure 7 For example, the detection system 1B performs the processing of step S54 through the polarization beam splitter 5.

[0219] Then, the detection system 1B performs branching of the input photons (step S55). The detection system 1B further branches or diffuses the photons branched by the polarized light and introduces the photons into the photodetector 7. Examples include a spectrometer, a lens that diffuses light, or a combination thereof. For example, the detection system 1B performs the processing of step S55 through the light branching unit 6.

[0220] <1-13. Configuration and processing examples in path coding>

[0221] The following will refer to Fig.18 and Fig.19 Describes configuration and processing examples in path encoding. Fig.18 is a diagram illustrating an example of the configuration of the present embodiment in the case of path encoding. Fig.19 is a flow chart illustrating a method of photon introduction in path encoding. Note that descriptions of points similar to those described above will be appropriately omitted.

[0222] First, refer to Fig.18 A configuration example of a detection system 1C in path coding is described. Fig.18 The detection system 1C shown in FIG. 1 receives quantum entangled light from one or more paths. For example, the detection system 1C has a configuration in which Figure 6 An optical branching unit is arranged before each optical detection unit of the detection system 1 shown in , and a processing unit for wavelength conversion + wavelength selection is arranged before the beam splitter. In the detection system 1C, the first processing unit 2a1 and the second processing unit 3a1 corresponding to the path a-1 starting from the quantum entangled light source a and the first processing unit 2b1 and the second processing unit 3b1 corresponding to the path b-1 starting from the quantum entangled light source b are arranged before the beam splitter 4a. In the detection system 1C, the first processing unit 2a2 and the second processing unit 3a2 corresponding to the path a-2 starting from the quantum entangled light source a and the first processing unit 2b2 and the second processing unit 3b2 corresponding to the path b-2 starting from the quantum entangled light source b are arranged before the beam splitter 4b.

[0223] Note that, as described above, in the case where the first processing units 2a1, 2a2, 2b1, 2b2, etc. are not particularly distinguished, they are collectively referred to as the first processing unit 2, and in the case where the second processing units 3a1, 3a2, 3b1, 3b2, etc. are not particularly distinguished, they are collectively referred to as the second processing unit 3. In addition, in the case where the beam splitters 4a and 4b, etc. are not particularly distinguished, they are collectively referred to as the beam splitter 4.

[0224] Fig.18 The detection system 1C shown in the figure includes a beam splitter 4, a photodetector 7 arranged corresponding to the corresponding path branched out by the beam splitter 4 and the polarization beam splitter 5, a plurality of light branching units 6 that branch light to introduce it into each of the plurality of photodetectors 7, and a post-selector 8 that detects the corresponding detection timing of photons in the plurality of photodetectors 7.

[0225] here, Fig.18 The type of line to be connected between components in dictates the connection pattern between the components. Note that the relationship between the connection pattern of the line type is the same as Fig.16 For example, in the case where the detection system 1C is applied to quantum communication, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by an optical fiber. Note that in the case where the detection system 1C is applied to quantum sensing described later, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by an optical fiber or free space.

[0226] Next, we will refer to Fig.19 The following describes a processing example of the detection system 1C. The detection system 1C performs the processing shown in steps S61 to S64. In the introduction of photons in path coding, for example, two quantum entangled light sources a and b are input at Fig.18 The light in the overlapping state of the two pulses is shown below each light source.

[0227] The detection system 1C performs wavelength conversion and wavelength selection (step S61). The processing of step S61 is the same as Figure 7 For example, the detection system 1C performs the processing of step S61 through the first processing unit 2. Note that, if Figure 7 As shown in the brackets in step S21, wavelength conversion and wavelength selection are arbitrary processes and may be performed or not performed as needed. In addition, the detection system 1C performs unitary conversion on the input light (step S62). The processing of step S62 is the same as Figure 7 For example, the detection system 1C executes the processing of step S62 through the second processing unit 3.

[0228] Then, the detection system 1C performs processing by the beam splitter (step S63). For example, the detection system 1C performs interference of the input photons. The processing of step S63 is the same as Figure 7 For example, the detection system 1C executes the processing of step S63 through the beam splitter 4.

[0229] Then, the detection system 1C performs branching of the input photons (step S64). The detection system 1C further branches or diffuses the photons branched by the polarized light and introduces the photons into the photodetector 7. Examples include a spectrometer, a lens that diffuses light, or a combination thereof. For example, the detection system 1C performs the processing of step S64 through the light branching unit 6.

[0230] <1-14. Example of post-selection in quantum communication>

[0231] From here on, refer to Fig. 20 Describe an example of postselection in quantum communication. Fig. 20 is a flowchart illustrating a method of post-selection in the case of quantum communication. Note that descriptions of points similar to the above points will be appropriately omitted. Note that, Fig. 20 The processing shown in can be executed by any detection system 1 (such as detection systems 1B, 1C, etc.) as long as the processing can be executed.

[0232] The detection system 1 performs the processing shown in steps S71 to S74 in the post-selection in quantum communication. For example, the detection system 1 performs the processing shown in steps S71 to S74 by post-selection 8. The detection system 1 performs reception of light detection information (step S71). The processing of step S71 is the same as that of step S71. Fig.13 Corresponding to step S41 in .

[0233] Then, the detection system 1 performs determination of simultaneous detection of photons (step S72). The processing of step S72 is the same as Fig.13 When it is determined that no photons are detected simultaneously (step S72: No), the detection system 1 ends the post-selection processing without executing the processing of steps S73 and S74.

[0234] When it is determined that photons are detected simultaneously (step S72: Yes), the detection system 1 performs a process of confirming the bell-shaped state (step S73). The process of step S73 is the same as that of Fig.13 Then, the detection system 1 performs the notification of the bell-shaped state (step S74). The processing of step S74 is the same as Fig.13 Corresponding to step S45 in .

[0235] In quantum communication as described above, the detection system 1 can increase the quantum entanglement generation rate by using the photodetector 7 such as an array detector, and can generate a quantum entangled state efficiently.

[0236] <1-15. Configuration and processing example in photon presence / absence encoding>

[0237] Note that the encoding method is not limited to the above-mentioned polarization encoding and path encoding, and any method may be adopted as long as it is applicable. Fig.21 and Fig. 22 Describes the presence / absence of a photon. Fig.21 is a diagram illustrating an example of the configuration of the present embodiment in the case of photon presence / absence encoding. Fig. 22 is a flowchart illustrating a method of photon introduction in photon presence / absence encoding. Note that descriptions of points similar to those described above will be appropriately omitted.

[0238] First, refer to Fig.21 Describe a configuration example of a detection system 1D in photon presence / absence encoding. Fig.21 The detection system 1D shown in FIG. 1 receives quantum entangled light from one or more paths. For example, the detection system 1D has a configuration in which Figure 5 In the detection system 1 shown in , the polarization beam splitter is removed, the light branching unit is arranged before each light detection unit, and the processing unit for wavelength conversion + wavelength selection is arranged before the beam splitter. In the detection system 1D, the first processing unit 2a and the second processing unit 3a corresponding to the path starting from the quantum entangled light source a and the first processing unit 2b and the second processing unit 3b corresponding to the path starting from the quantum entangled light source b are arranged before the beam splitter 4.

[0239] Fig.21 The detection system 1D shown in the figure includes a beam splitter 4, a photodetector 7 arranged corresponding to the corresponding path branched out by the beam splitter 4, a plurality of light branching units 6 that branch light to introduce into each of the plurality of photodetectors 7, and a post-selector 8 that detects the corresponding detection timing of photons in the plurality of photodetectors 7.

[0240] here, Fig.21 The type of line to be connected between components in dictates the connection pattern between the components. Note that the relationship between the connection pattern of the line type is the same as Fig.16, so its detailed description will be omitted. For example, in the case where the detection system 1D is applied to quantum sensing described later, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by optical fiber or free space. Note that in the case where the detection system 1D is applied to quantum communication, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by optical fiber.

[0241] Next, we will refer to Fig. 22 The processing example of the detection system 1D is described. The detection system 1D performs the processing shown in steps S81 to S85. In the photon introduction in the photon presence / absence encoding, for example, two quantum entangled light sources a and b are input in Fig.21 The light in the overlapping state of the two pulses is shown below each light source.

[0242] The detection system 1D performs wavelength conversion and wavelength selection (step S81). The processing of step S81 is the same as Figure 7 For example, the detection system 1D performs the processing of step S81 through the first processing unit 2. Note that, if Figure 7 As shown in the brackets in step S11, wavelength conversion and wavelength selection are arbitrary processes and may be performed or not performed as needed. In addition, the detection system 1D performs a unitary conversion on the input light (step S82). The processing of step S82 is the same as Figure 7 For example, the detection system 1D executes the processing of step S82 through the second processing unit 3.

[0243] Then, the detection system 1D performs interference of the input photons (step S83). The processing of step S83 is the same as Figure 7 For example, the detection system 1D performs the processing of step S83 through the beam splitter 4. Then, the detection system 1D performs branching by polarization (step S84). The processing of step S84 is the same as Figure 7 It corresponds to step S14 in . Note that the detection system 1D does not need to execute step S84. For example, in the case where the detection system 1D includes the polarization beam splitter 5, the processing of step S84 is executed by the polarization beam splitter 5.

[0244] Then, the detection system 1D performs branching of the input photons (step S85). The detection system 1D further branches or diffuses the photons branched by the polarized light and introduces the photons into the photodetector 7. Examples include a spectrometer, a lens that diffuses light, or a combination thereof. For example, the detection system 1D performs the processing of step S85 through the light branching unit 6.

[0245] <1-16. Configuration and processing example in time encoding>

[0246] From here on, as methods other than polarization encoding and path encoding, reference will be made to Fig.23 and Fig.24 Describes the time code. Fig.23 is a diagram illustrating an example of the configuration of the present embodiment in the case of time encoding. Fig.24 is a flow chart illustrating a method of photon introduction in time encoding. Note that descriptions of points similar to those described above will be appropriately omitted.

[0247] First, refer to Fig.23 A configuration example of the detection system 1E in time encoding is described. Fig.23 The detection system 1E shown in FIG. 1 receives quantum entangled light from one or more paths. For example, the detection system 1E has a configuration in which Figure 5 In the detection system 1 shown in , the polarization beam splitter is removed, a reflector and a phase modulator are added, an optical branching unit is arranged before each optical detection unit, and a processing unit for wavelength conversion + wavelength selection is arranged before the beam splitter. In the detection system 1E, the first processing unit 2a and the second processing unit 3a corresponding to the path starting from the quantum entangled light source a and the first processing unit 2b and the second processing unit 3b corresponding to the path starting from the quantum entangled light source b are arranged before the beam splitter 4.

[0248] Fig.23 The detection system 1E shown in the figure includes a beam splitter 4, a photodetector 7 arranged corresponding to the corresponding path branched out by the beam splitter 4, a plurality of light branching units 6 that branch light to introduce into each of the plurality of photodetectors 7, and a post-selector 8 that detects the corresponding detection timing of photons in the plurality of photodetectors 7.

[0249] In addition, the detection system 1E includes reflectors 9a and 9b and a phase modulator 20. Without particularly distinguishing between the reflectors 9a and 9b, etc., they are collectively referred to as reflectors 9. The reflector 9 is a reflector that reflects photons. The reflector 9 is arranged at a position where the light from the beam splitter 4a is reflected and input to the beam splitter 4b. In addition, the phase modulator 20 performs phase modulation on a light beam branched by the beam splitter 4a. The phase modulator 20 is arranged in a path between the beam splitter 4a and the beam splitter 4b.

[0250] here, Fig.23 The type of line to be connected between components in dictates the connection pattern between the components. Note that the relationship between the connection pattern of the line type is the same as Fig.16For example, in the case where the detection system 1E is applied to quantum sensing described later, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by either optical fiber or free space. Note that in the case where the detection system 1E is applied to quantum communication, the connection corresponding to the solid line between the quantum entangled light sources a and b and the first processing unit 2 is realized by optical fiber. Note that only the above Fig.16 , Fig.18 , Fig.21 and 23 The type of lines in the diagram indicates the connection pattern between components, and other diagrams (e.g. Fig.25 ) does not indicate the connection pattern between components.

[0251] Next, we will refer to Fig.24 A processing example of the detection system 1E is described. The detection system 1E performs the processing shown in steps S91 to S96. Note that, unless otherwise specified, the components that perform the functions of the blocks, the connections of the components, etc. are similar to those described in <1-5. Method for implementing photon introduction in polarization encoding>. Each block of the flowchart will be described below.

[0252] In the photon introduction in time coding, light in a temporally overlapping state of two pulses is input from two quantum entangled light sources a and b, as expressed in the following expressions (1) and (2). For example, expression (1) corresponds to quantum entangled light source a, and expression (2) corresponds to quantum entangled light source b.

[0253]

[0254] |E>a in expression (1) and |E>b in expression (2) represent pulses emitted earlier in time from quantum entangled light sources a and b, respectively, |L>a in expression (1) and |L>b in expression (2) represent pulses emitted a certain period of time (equal to or greater than the time resolution of the photodetector 7) later than |E>a and |E>b, respectively, and e iθ Represents the phase difference component of two pulses.

[0255] (Wavelength conversion and wavelength selection)

[0256] The detection system 1E performs wavelength conversion and wavelength selection (step S91). The wavelength conversion can be performed at Fig.24 The wavelength after the conversion may be shorter or longer than the input light. In addition, a mechanism for selecting the wavelength of the light to be input to the photodetector 7 after the wavelength conversion may be introduced. For example, the detection system 1E performs the processing of step S91 by the first processing unit 2.

[0257] (Unitary transformation of input light)

[0258] The detection system 1E performs a unitary conversion on the input light (step S92). For example, the detection system 1E performs a unitary conversion to make the two input light beams interfere with each other at BS. The mechanism for unitary conversion can be installed on either or both of the two optical paths. For example, the detection system 1E performs the processing of step S92 through the second processing unit 3.

[0259] (Beam Splitter #1)

[0260] Detection system 1E is connected via beam splitter #1 (e.g. Fig.23 The detection system 1E performs processing of step S93 by the beam splitter 4a. The detection system 1E branches the light from the light source into two paths, namely, the short optical path E and the long optical path L. For example, the detection system 1E performs processing of step S93 by the beam splitter 4a.

[0261] (Phase Modulation)

[0262] The detection system 1E performs phase modulation (step S94). The detection system 1E modulates the phase iω Applied to one of the paths split by beam splitter #1 ( Fig.23 When a single pulse is input to the beam splitter #1 and this phase modulation is applied, an overlapping state as shown in the following expression (3) is obtained. For example, the detection system 1E performs the processing of step S94 by the phase modulator 20.

[0263]

[0264] (Beam Splitter #2)

[0265] Detection system 1E is connected to the detector 1E through beam splitter #2 (e.g. Fig.23 The detection system 1E performs processing (step S95) on the beam splitter 4b in the detection system 1E. The detection system 1E multiplexes the light beams branched by the beam splitter #1. For example, the detection system 1E performs the processing of step S95 by the beam splitter 4b.

[0266] Here, for example, in the case of photons introduced from the quantum entangled light source a, the multiplexed light is in an overlapping state as shown in the following expression (4).

[0267]

[0268] Here, in the case where the pulse time difference of the light source is the same as the time difference caused by the optical path after the beam splitter #1 and adjustment is performed by phase modulation so that θ=-ω is satisfied, |EE>a and |LL>a can be separated in time and are therefore not in an overlapping state. In addition, in the case where the light sources are two quantum entangled light sources a and b, the overlapping state occurring in the beam splitter #2 is expressed by the following expression (5).

[0269]

[0270] Here, since |EL>a and |EL>b, and |LE>a and |LE>b are inseparable, the above expressions can be normalized and expressed as the following expression (6).

[0271]

[0272] (Branch for input photons)

[0273] The detection system 1E performs branching on the input photons (step S96). The detection system 1E branches or diffuses the photons output from the beam splitter #2 and introduces the photons into the photodetector 7. Examples include a beam splitter, a lens that diffuses light, or a combination thereof. For example, the detection system 1E performs the processing of step S96 through the light branching unit 6.

[0274] <1-17. Configuration Example in Quantum Sensing>

[0275] The above detection system 1 can be used for quantum sensing. Fig.25 A configuration example in the case of quantum sensing is described. Fig.25 : is a diagram illustrating an example of a configuration of quantum sensing of the present embodiment. Hereinafter, a light detection system applied to quantum sensing is referred to as a sensing system. Note that the sensing system may be referred to as a measuring device or the like.

[0276] First, refer to Fig.25 A configuration example of the sensing system 10 in quantum sensing is described. Fig.25 The sensing system 10 shown in FIG. 1 includes a quantum entanglement generator 1F and a quantum entanglement light source 30 that outputs at least two photons in a quantum entangled state. Note that, Fig.25 The quantum entanglement generator 1F shown in FIG. 1 is merely an example of the configuration of the quantum entanglement generator, and any configuration may be employed as the quantum entanglement generator as long as the desired sensing can be performed. A detection system 1 such as the above-described detection systems 1 to 1E may be used as a quantum entanglement generator of the sensing system 10.

[0277] The quantum entanglement generator 1F detects photon detection timing by the photodetector 7 provided corresponding to the path branched by at least one beam splitter 4 that causes quantum entangled light to interfere. Fig.25 The quantum entanglement generator 1F shown in the figure includes a photodetector 7 arranged corresponding to the corresponding paths branched out by the beam splitter 4 and the polarization beam splitters 5a and 5b, a light branching unit 6 that branches light to introduce into multiple photodetectors 7, and a post-selection 8 that detects the corresponding detection timing of photons in the multiple photodetectors 7.

[0278] For example, the quantum entanglement generator 1F has Figure 5 In the configuration shown in the detection system 1, a light branching unit is arranged before each light detection unit. In the quantum entanglement generator 1F, the first processing units 2a, 2b, 2c and 2d are located after the beam splitter 4. Fig.25 In the embodiment, each of the four first processing units 2a, 2b, 2c and 2d is arranged before each of the four optical branching units 6a, 6b, 6c and 6d. Note that, as described above, without particularly distinguishing the first processing units 2a1, 2a2, 2b1, 2b2, etc., the first processing units 2a1, 2a2, 2b1, 2b2, etc. are collectively referred to as the first processing unit 2.

[0279] After being branched by the beam splitter 4, the first processing unit 2 performs processing on the quantum entangled light after interference by the beam splitter 4. The first processing unit 2 performs at least one of wavelength conversion or wavelength selection on the quantum entangled light after interference by the beam splitter 4.

[0280] Among the first light guiding path LP1 that applies one of the two photons to the observation target TG serving as the target (sensing target), the second light guiding path LP2 that guides the photon returned from the observation target TG to the beam splitter 4, and the third light guiding path LP3 that guides the other of the two photons to the beam splitter 4, the quantum entanglement generator 1F receives light from the second light guiding path LP2 and the third light guiding path LP3.

[0281] Fig.25 The sensing system 10 shown in FIG. 1 includes a sum frequency generator 40. The sum frequency generator 40 is arranged in at least one of the second light guide path LP2 or the third light guide path LP3. Fig.25 In the embodiment of the present invention, the sum frequency generator 40 is arranged in the third light guiding path LP3. The sum frequency generator 40 performs processing related to sum frequency generation.

[0282] For example, in the case where the sensing system 10 is used for fluorescence measurement, since the energy of the photon returned from the target (observation target TG, etc.) changes from the time of irradiation, the sum frequency generator 40 is used to equalize the energy of two photons entering the BS. For example, a LiNbO crystal or the like that periodically reverses polarization can be used for the sum frequency generator 40. The sum frequency generator 40 converts two input light beams into one output light beam through a nonlinear optical effect. In this case, for example, the frequency of the output light of the sum frequency generator 40 is the total value of the input light.

[0283] The sensing system 10 implements sensing for detecting reflected light from a target. For example, the sensing system 10 provides a two-photon quantum interference method in sensing using a photon pair in a quantum entangled state. The sensing system 10 projects one of the quantum entangled light pairs onto the target, and detects the reflected or scattered photon and the other photon in the photon pair through two-photon quantum interference, thereby achieving highly sensitive sensing.

[0284] <1-18. Example of post-selection in quantum sensing>

[0285] From here on, refer to Fig.26 Describe an example of post-selection in quantum sensing. Fig.26 is a flowchart illustrating a method of post-selection in the case of quantum sensing. Note that descriptions of points similar to the above points will be appropriately omitted. Note that as long as processing can be performed, Fig.26 The processing shown in can be performed by detection systems 1 and 10, etc.

[0286] The sensing system 10 performs the processing shown in steps S101 to S103 in the post-selection in quantum sensing. For example, the sensing system 10 performs the processing shown in steps S101 to S103 by post-selection 8. The sensing system 10 performs reception of light detection information (step S101). The processing of step S101 is the same as that of step S102. Fig.13 Corresponding to step S41 in .

[0287] Then, the sensing system 10 performs determination of simultaneous detection of photons (step S102). The processing of step S102 is the same as Fig.13 When it is determined that no photons are detected simultaneously (step S102: No), the sensing system 10 ends the post-selection process without executing the process of step S103.

[0288] When it is determined that the photons are detected simultaneously (step S102: Yes), the sensing system 10 performs notification of simultaneous detection (step S103). The processing of step S103 is the same as that of Fig.13 Corresponding to step S46 in .

[0289] <1-19. Application examples of quantum sensing>

[0290] The quantum sensing of the sensing system 10 can be applied to any sensing. For example, the quantum sensing of the sensing system 10 can be applied to the sensing of fluorescent substances. For example, the quantum sensing of the sensing system 10 can be applied to sample analysis. For example, the quantum sensing of the sensing system 10 can be applied to single pixel imaging. For example, the quantum sensing of the sensing system 10 can be applied to imaging systems.

[0291] Hereinafter, specific examples of applying the sensing system described above to quantum sensing are described as first to fourth application examples. Note that the first to fourth application examples described below are merely examples, and the sensing system can be applied to any sensing as long as it is applicable. Note that, without particularly distinguishing the sensing systems 10A to 10D and the like described below, they are collectively referred to as the sensing system 10.

[0292] <1-19-1. First application example (two-photon excitation / second harmonic microscopy)>

[0293] First, as a first application example, a case where quantum sensing of the sensing system 10 is applied to two-photon excitation, second harmonic microscopy, or the like will be described. Fig. 27 is a diagram illustrating a first application example of quantum sensing.

[0294] Fig. 27 The sensing system 10A shown in FIG. 6 includes a quantum entanglement generator 1G, a quantum entanglement light source 30 , an excitation light source 35 , and a lens unit 65 .

[0295] The excitation light source 35 outputs excitation light to the observation target TG1. Fig. 27 , the excitation light source 35 irradiates the observation target TG1 with the target excitation light having the frequency ω2. The lens unit 65 scans the observation target TG1 as a target. For example, the observation target TG1 is an up-conversion probe, a tissue having a structure serving as a harmonic source, or the like.

[0296] In the quantum entanglement generator 1G, Fig.25 In the quantum entanglement generator 1F shown in FIG, a bandpass filter 50a is arranged in the second light guide path LP2, and a phase adjuster 25 and a bandpass filter 50b are arranged in the third light guide path LP3 in addition to the sum frequency generator 40. Note that, in the case where the bandpass filters 50a and 50b described below are not particularly distinguished, they are collectively referred to as the bandpass filter 50.

[0297] The bandpass filter 50 is arranged in at least one of the second light guide path LP2 or the third light guide path LP3, functions as a bandpass filter (BPF), and performs frequency-related processing. The phase adjuster 25 is arranged in at least one of the second light guide path LP2 or the third light guide path LP3. The phase adjuster 25 performs processing related to phase adjustment. Fig. 27 In the embodiment, idler excitation light with frequency f2 is input to sum frequency generator 40.

[0298] For example, in sensing using quantum entangled photon pairs, the sensing system 10A provides a method for measuring specific fluorescent substances with high sensitivity. In the case where the fluorescence emitted from the target changes in at least one of the wavelength, phase, time of fluorescence emission, or polarization relative to the projected quantum entangled light, the sensing system 10A performs an operation corresponding to the above change on the other of the photon pair and detects the two photons by two-photon quantum interference, thereby achieving highly sensitive sensing.

[0299] In the following, Fig. 27 The first application example will be described more specifically by taking the configuration of as an example. As described above, an example in which the sensing system 10A is applied to two-photon excitation or second harmonic microscopy will be described.

[0300] The sensing system 10A irradiates photons of frequency ω1 to an observation target TG1 including a target (imaging target) such as tissue or cells from the quantum entangled light source 30. At the same time, target excitation light of frequency ω2 is irradiated to the observation target TG1 from another light source.

[0301] When the quantum entangled light and the target excitation light interact with each other simultaneously, the observation target TG1 transitions to a higher energy level by a total of two photons, and then, when the observation target TG1 returns to the ground state, the observation target TG1 emits fluorescence with a frequency of F=ω1+ω2. For example, when returning from the two-photon excitation energy level transitioned by the quantum entangled light and the target excitation light to the target ground state, the observation target TG1 emits two-photon excitation fluorescence with the above-mentioned frequency F. The sensing system 10A measures this fluorescence.

[0302] First, the sensing system 10A transmits only light having a frequency F by passing the light received from the observation target TG1 through the bandpass filter 50 (BPF). The light transmitted by the BPF is introduced into the beam splitter 4 (BS). Simultaneously with the fluorescence from the observation target TG1, another light (idler light) from the quantum entangled light source 30 is introduced into the beam splitter 4 (BS). The sensing system 10A can optionally perform phase adjustment through the phase adjuster 25 to perform simultaneous measurement with the fluorescence. In addition, the sensing system 10A can perform sum frequency generation through the sum frequency generator 40 using the idler excitation light to match the frequency of the idler light with the frequency F of the fluorescence. Note that phase adjustment and sum frequency generation can be optionally interchanged.

[0303] In the sensing system 10A, two beams of light simultaneously introduced into the BS generate two-photon interference, and then are branched by the polarization characteristics in the polarization beam splitter 5 (PBS), and further diffused into the sensitive area of ​​the photodetector 7 by the light branching unit 6 and measured. In the sensing system 10A, the post-selection 8 determines that the measured signals are measured simultaneously, and only valid measurement events are selected.

[0304] The sensing system 10A as described above can be applied to a two-photon excitation microscope for microstructural analysis of biological tissues such as the brain. In addition, the sensing system 10A can be applied to a second harmonic microscope for early diagnosis of pathological tissue diagnosis and cancer fibrosis detection.

[0305] The sensing system 10A allows long-term target observation with reduced toxicity and allows reduced toxicity through reduced phototoxicity and reduced probe dose. In addition, the sensing system 10A can obtain information in the depth direction (about 10 mm) of thick samples compared to existing samples (up to about 2 mm).

[0306] <1-19-2. Second application example (near-infrared fluorescence imaging)>

[0307] Next, a case where quantum sensing of the sensing system 10 is applied to near-infrared fluorescence imaging or the like will be described as a second application example. Fig.28 is a diagram illustrating a second application example of quantum sensing. Note that descriptions of points similar to those described above will be appropriately omitted.

[0308] Fig.28 The sensing system 10B shown in FIG. 1 includes a quantum entanglement generator 1H, a quantum entanglement light source 30, and a lens unit 65. The lens unit 65 scans an observation target TG2 as a target. For example, the observation target TG2 is a near-infrared fluorescent material or the like.

[0309] The quantum entanglement generator 1H has Fig. 27In the quantum entanglement generator 1G shown in FIG. 1 , the arrangement of the sum frequency generator 40 is changed from the third light guide path LP3 to the configuration of the second light guide path LP2. Fig.28 In the process, the excitation light with a frequency of ω2 is input to the sum frequency generator 40.

[0310] For example, the sensing system 10B is a system that performs measurement while scanning (alternatively, moving the target) a target (eg, a cell, a tissue, etc.) and performs imaging based on the measurement result.

[0311] In the following, Fig.28 The second application example will be described more specifically, taking the configuration of as an example. As described above, an example in which the sensing system 10B is applied to near-infrared fluorescence imaging will be described.

[0312] The sensing system 10B irradiates an observation target TG2 including a target (imaging target) such as a tissue or a cell with photons from the quantum entangled light source 30. When the observation target TG2 is excited by the quantum entangled light and returns to the base state, the observation target TG2 emits fluorescence with a frequency ω1. For example, the observation target TG2 emits near-infrared fluorescence with the above-mentioned frequency ω1 when returning from the excitation energy level of the quantum entangled light transition to the target base energy level. The sensing system 10B measures this fluorescence.

[0313] When the photodetector fails to detect fluorescence, the sensing system 10B can perform frequency conversion by sum frequency generation in the sum frequency generator 40. When performing frequency conversion, the sensing system 10B transmits only light having a conversion frequency F by passing the photons after conversion through the bandpass filter 50 (BPF). The light transmitted through the BPF is introduced into the beam splitter 4 (BS). Simultaneously with the light obtained from the observation target TG2, another light (idle light) from the quantum entangled light source 30 is introduced into the BS. Phase adjustment for performing simultaneous measurement with fluorescence can be optionally performed by the phase adjuster 25.

[0314] In the sensing system 10B, two beams of light simultaneously introduced into the BS generate two-photon interference, and then are branched by the polarization characteristics in the polarization beam splitter 5 (PBS), and further diffused into the sensitive area of ​​the photodetector 7 by the light branching unit 6 and measured. In the sensing system 10B, the simultaneous measurement of the measured signal is determined by the post-selection 8, and only valid measurement events are selected.

[0315] The sensing system 10B as described above can be applied to deep imaging (about 40 mm) of a living body and observation of tiny parts (such as capillaries, lymphatic vessels or cancer tumor sites). In addition, the sensing system 10B can be applied to polymerase chain reaction (PCR), cell surface, identification of specifically expressed proteins, cancer biomarkers, immunohistochemical staining markers for pathological examination, and high-sensitivity fluorescent label detection of in vitro diagnostic fluorescent particles.

[0316] For example, many near-infrared probes are cytotoxic, such as carbon nanotubes, ceramic nanoparticles, and rare earth ions, but the sensing system 10B can reduce bioburden by reducing toxicity. In addition, the sensing system 10B can obtain information in the depth direction of thick samples (about 40 mm) compared to existing samples (up to about 20 mm).

[0317] <1-19-3. Third application example (near infrared optical brain measurement device)>

[0318] Next, a case where quantum sensing of the sensing system 10 is applied to near-infrared fluorescence imaging or the like will be described as a third application example. Fig.29 is a diagram illustrating a third application example of quantum sensing. Note that descriptions of points similar to those described above will be appropriately omitted.

[0319] Fig.29 The sensing system 10C shown in FIG. 1 includes a quantum entanglement generator 1I, a quantum entanglement light source 30, and a light receiving probe 66. The light receiving probe 66 is a probe for receiving light from an observation target TG3 as a target. For example, the observation target TG3 is a cerebral blood flow, a fluorescent probe, or the like.

[0320] The quantum entanglement generator 1I has a configuration in which Fig. 27 In the quantum entanglement generator 1G shown in FIG. 1 , the arrangement of the phase adjuster 25 and the sum frequency generator 40 is changed from the third light guide path LP3 to the third light guide path LP2. Fig.29 In the process, the signal excitation light is input to the sum frequency generator 40.

[0321] For example, the sensing system 10C is a system that performs in vivo imaging of a specific part of a living body or a small animal such as an organ or a device.

[0322] In the following, we will Fig.29 The third application example will be described more specifically as an example of a configuration of As described above, an example in which the sensing system 10C is applied to a near-infrared optical brain measurement device (near infrared spectroscopy (NIRS)) will be described.

[0323] The sensing system 10C irradiates the head with photons from the quantum entangled light source 30 through an optical fiber (transmission fiber). The assumed target (observation target TG3) includes the following, and the light received by the sensing system 10C differs according to the difference of the observation target TG3.

[0324] For example, when cerebral blood flow is set as the observation target TG3, the light received by the sensing system 10C is reflected light from the cerebral blood flow. In addition, for example, when a fluorescent probe is set as the observation target TG3, the light received by the sensing system 10C is fluorescence from the probe.

[0325] The light emitted from the observation target TG3 is introduced into the quantum entanglement generator 1I of the sensing system 10C through the light receiving probe 66. The sensing system 10C introduces the received light into the beam splitter 4 (BS) so as to be measured simultaneously with the idler light from the quantum entangled light source 30. Before the introduction of the BS, phase adjustment can be optionally performed by the phase adjuster 25. In addition, the sensing system 10C can perform frequency conversion by sum frequency generation so that the received light matches the frequency of the idler light. When performing frequency conversion, the sensing system 10C passes the converted light through the bandpass filter 50 (BPF) so as to select the light with successful sum frequency generation.

[0326] In the sensing system 10C, other light emitted from the quantum entangled light source 30 is introduced into the BS so as to interfere with the light emitted from the observation target TG3. In the sensing system 10C, the two beams of light simultaneously introduced into the BS generate two-photon interference, and then are branched by the polarization characteristics in the polarization beam splitter 5 (PBS), and further diffused into the sensitive area of ​​the photodetector 7 by the light branching unit 6 and measured. In the sensing system 10C, the simultaneous measurement of the measured signal is determined by the post-selection 8, and only valid measurement events are selected.

[0327] The sensing system 10C as described above can be applied to rehabilitation effect determination and pain assessment by evaluating brain activity amount / brain activation site. In addition, the sensing system 10C can be applied to medical diagnosis of dementia, brain tumors, etc. In addition, the sensing system 10C can be applied to brain-machine interface (Brain-machine I / F).

[0328] For example, although the conventional target is only cerebral blood flow, the sensing system 10C enables medical diagnosis by using a near-infrared fluorescent probe. The sensing system 10C can acquire information in a deeper depth direction (about 40 mm) than the existing system (up to about 20 mm). Therefore, the sensing system 10C can measure a part different from the conventional part (white matter, cerebellum, etc.).

[0329] <1-19-4. Fourth Application Example (Flow Cytometer)>

[0330] Next, a case where quantum sensing of the sensing system 10 is applied to a flow cytometer (FCM) or the like will be described as a fourth application example. Fig.30 is a diagram illustrating a fourth application example of quantum sensing. Note that descriptions of points similar to those described above will be appropriately omitted.

[0331] Fig.30 The sensing system 10D shown in FIG. 1 includes a quantum entanglement generator 1J, a quantum entanglement light source 30, a pulsating light source 36, an image sensor 85, and an image processing unit 86. The pulsating light source 36 irradiates an observation target TG4 as a target with light. For example, the observation target TG4 is a cell flowing in a fluid when analyzing a sample or the like in in vitro diagnosis.

[0332] The quantum entanglement generator 1J has a configuration in which Fig. 27 In the quantum entanglement generator 1G shown in FIG. 1 , the arrangement of the sum frequency generator 40 is changed from the third light guide path LP3 to the fourth light guide path LP2. Fig.30 In the process, the signal excitation light is input to the sum frequency generator 40.

[0333] For example, the sensing system 10D is a system for detecting trace amounts of targets in a sample that are difficult to detect using existing analytical methods.

[0334] In the following, we will Fig.30 The fourth application example will be described more specifically as an example of the configuration of. As described above, an example in which the sensing system 10D is applied to a flow cytometer will be described. The sensing system 10D irradiates a liquid in which cells are suspended with light (signal light) from a quantum entanglement light source 30, and generates fluorescence from the cells. The fluorescence is introduced into a beam splitter 4 (BS) included in a quantum entanglement generator 1J.

[0335] The sum frequency generator 40 may optionally perform frequency conversion by sum frequency generation on the fluorescence to cause the fluorescence to interfere with the other (idler light) of the entangled light. When performing frequency conversion, the sensing system 10D passes the converted light through a bandpass filter 50 (BPF) to select the light that has successfully generated the sum frequency.

[0336] In the sensing system 10D, idler light is also introduced into the BS included in the quantum entanglement generator 1J. For the idler light, phase adjustment can be optionally performed by the phase adjuster 25 to interfere with the fluorescence.

[0337] In the sensing system 10D, two beams of light simultaneously introduced into the BS generate two-photon interference, and then are branched according to polarization characteristics in the polarization beam splitter 5 (PBS), and further diffused into the sensitive area of ​​the photodetector 7 through the light branching unit 6 and measured. In the sensing system 10D, the simultaneous measurement of the measured signal is determined by the post-selection 8, and only valid measurement events are selected.

[0338] The sensing system 10D illuminates the cell with light from the pulsating light source 36 during the quantum entangled signal light exposure, and acquires a morphological image of the cell through the image sensor 85. This image is given a timestamp of when the image was acquired, and the sensing system 10D selects an image that is closest to the time of the quantum light measurement event selected in the post-selection 8 of two-photon interference. In the sensing system 10D, the image processing unit 86 performs image processing that overlaps the quantum light measurement event selected so far with the cell morphological image, and visualizes the fluorescent light source located inside the cell.

[0339] The sensing system 10D as described above can be applied to disease diagnosis, analysis of results of gene introduction, cell line separation, and the like.

[0340] The sensing system 10D can directly measure fluorescence emitted from intracellular organs, thereby enabling non-fluorescence / non-staining measurements, fluorescence measurements in the near-infrared (NIR) region, and the like.

[0341] In the quantum sensing as described above, the sensing system 10 can achieve high-sensitivity sensing by selectively measuring signals, and can efficiently generate a quantum entangled state.

[0342] <1-20. Configuration Example of Light Branching Unit and Photodetector>

[0343] Hereinafter, configuration examples of the optical branching unit 6 and the photodetector 7 will be described. Note that the configuration described below is merely an example, and any configuration may be adopted for the optical branching unit 6 and the photodetector 7 as long as it is possible to perform the desired detection. In addition, the optical branching unit 6 and the photodetector 7 having the configuration described below may be included in either the detection system 1 or the sensing system 10, and the case where the detection system 1 includes them will be described below as an example. Since the detection system 1 has a configuration such as the following first configuration example (multiple elements) or the second configuration example (array element), it is possible to improve the sensitivity of simultaneous measurement, reduce the influence of the dead time of the element, increase the measurement rate, and the like.

[0344] <1-20-1. First Configuration Example (Multiple Elements)>

[0345] First, refer to Fig.31A first configuration example of the light branching unit 6 and the photodetector 7 is described. Fig.31 is a diagram illustrating a first configuration example of a light branching unit and a photodetector. Fig.31 and Fig.16 The configuration of the portion in PT1 corresponds to the portion in PT1. Fig.31 Pictured Fig.16 An outline of the configuration of the optical branching unit 6d among the four optical branching units 6, the photodetectors 7d of the four photodetectors 7, and the post-selector 8.

[0346] exist Fig.31 In the embodiment, the photodetector 7 includes five detection units 70a, 70b, 70c, 70d, and 70e. Note that, without particularly distinguishing the detection units 70a, 70b, 70c, 70d, 70e, etc. described below, they are collectively referred to as the detection unit 70. Fig.31 As shown in FIG. 1 , in the first configuration example, the photodetector 7 includes a plurality of detection units 70 that detect light branched by the light branching unit 6. Each detection unit 70 is a light receiving element (light receiver) that detects light branched by the light branching unit 6, for example.

[0347] In addition, the light branching unit 6 is a spectrometer that branches and introduces light into each of the plurality of detection units 70. Fig.31 , the optical branching unit 6 branches light to each of the five detection units 70. For example, the optical branching unit 6 has a plurality of optical paths (e.g., optical fibers, etc.) that branch light to the detection units 70, and the detection units 70 branch light to each of the five detection units 70. For example, the optical branching unit 6 includes a first optical path for branching light to the detection unit 70a, a second optical path for branching light to the detection unit 70b, a third optical path for branching light to the detection unit 70c, a fourth optical path for branching light to the detection unit 70d, and a fifth optical path for branching light to the detection unit 70d.

[0348] As described above, in the first configuration example, the light branching unit 6 as a spectrometer branches and introduces light into a plurality of detection units 70 (elements). In the case of adopting the first configuration example, for example, in the detection system 1, a photodetector 7 including a plurality of detection units 70 (light receiving elements) is used. The light input to the photodetector 7 is branched into a plurality of light paths by the light branching unit 6, and the detection unit 70 (light receiving element) is provided for light detection independently of each light path.

[0349] In the first configuration example, there is a device that sends a timing clock to the outside of the detector (e.g., detection unit 70), and time synchronization is performed between the detectors. As a means for synchronizing the time between the detectors, means other than the above means can be applied. In addition, in the first configuration example, a function that requires advance preparation such as training and calibration before measurement can be introduced.

[0350] Note that in the first configuration example, a detector capable of detecting a single photon or a number of photons may be used. In addition, in the first configuration example, there may be differences in characteristics (such as material, composition, and shape) between multiple detectors. In addition, in the first configuration example, functions (such as cooling or variable bias) for improving and changing the characteristics of the detector may be provided.

[0351] <1-20-2. Second Configuration Example (Array Element)>

[0352] Next, we will refer to Fig.32 A second configuration example of the light branching unit 6 and the photodetector 7 is described. Fig.32 is a diagram illustrating a second configuration example of the light branching unit and the photodetector. Fig.32 and Fig.16 The configuration of the part in PT1 corresponds to the part in PT1. Fig.32 Pictured Fig.16 An outline of the configuration of the light branching unit 6d among the four light branching units 6, the photodetector 7d among the four photodetectors 7, and the post-selector 8 is shown.

[0353] like Fig.32 As shown in , in the second configuration example, the photodetector 7 is an array element. The photodetector 7 includes a plurality of regions AR (eg, light receiving elements) on a light receiving surface of the array element as a plurality of detection units. Fig.32 In FIG. 1 , the photodetector 7 has 16 areas AR.

[0354] In addition, the light branching unit 6 is a lens that branches and introduces light into each of a plurality of regions of the array element. Fig.32 In the embodiment, the light branching unit 6 branches light to each of the plurality of areas AR of the photodetector 7 .

[0355] As described above, in the second configuration example, the light branching unit 6 as a lens disperses and introduces light into the photodetector 7 as an array element. In the case of adopting the second configuration example, for example, in the detection system 1, a single array type detector is used as the photodetector 7. The input light is diffused on the light receiving surface of the photodetector 7 as an array type detector by diffusion at the lens or by the light branching unit 6 as a spectrometer.

[0356] In the second configuration example, in an array type detector (e.g., photodetector 7), the elements are synchronized with each other internally. In addition, in the second configuration example, synchronization between elements (e.g., light receiving elements) can be performed using a timing clock sent from the outside. In the second configuration example, a photodetector or detector element capable of detecting a single photon or a number of photons can be used, but it is preferred that the photodetector or detector element can detect the number of photons. In the second configuration example, a function for improving and changing the characteristics of the detector (such as cooling or variable bias) can be provided.

[0357] <1-20-3. Another configuration example (single array type detector)>

[0358] Not limited to the first configuration example and the second configuration example described above, any configuration may be adopted as the light branching unit 6 and the photodetector 7. Fig.33 This configuration example (also referred to as a "third configuration example") is described. Fig.33 is a diagram illustrating another configuration example of the photodetector. Fig.33 An example of a method for implementing the photodetector 7 is shown. Specifically, Fig.33 In the embodiment of the present invention, all photodetectors may be configured using a single array type detector as the photodetector 7. In this case, the detection system 1 may be a system having one photodetector 7.

[0359] exist Fig.33 In FIG. 1 , the photodetector 7 is an array element. The photodetector 7 includes a plurality of regions AR (eg, light receiving elements) on a light receiving surface of the array element as a plurality of detection units. Fig.33 , the photodetector 7 has 16 areas AR. For example, the photodetector 7 is configured so that the four areas AR on the upper left side detect light from the light branching unit 6a, the four areas AR on the upper right side detect light from the light branching unit 6b, the four areas AR on the lower left side detect light from the light branching unit 6c, and the four areas AR on the lower right side detect light from the light branching unit 6d. As described above, the photodetector 7 can be used as an array type detector that assigns a plurality of light detection elements to each path.

[0360] exist Fig.33 In the third configuration example shown in , the photodetector 7 which is a single array type detector is used to perform all light detections necessary for the detection system 1 and the like.

[0361] For example, in the detection system 1 having the third configuration example, the input light from the entangled light source undergoes unitary conversion, wavelength conversion, and wavelength selection, and is introduced into the beam splitter 4 (BS) to generate interference. In the detection system 1 having the third configuration example, the light undergoing the interference of the BS is introduced into the polarization beam splitter 5 (PBS), branched into four paths, and further introduced into the light branching unit 6.

[0362] In the optical branching unit 6 of the detection system 1 having the third configuration example, input light is diffused relative to a specific area AR of the photodetector 7 which is an array-type detector, and is introduced into the light receiving surface of the photodetector 7. In the photodetector 7 which is an array-type detector of the detection system 1 having the third configuration example, the elements are synchronized internally.

[0363] Note that in the third configuration example, a timing clock sent from the outside can be used to synchronize the elements. In the third configuration example, a photodetector or detector element capable of detecting a single photon or a number of photons can be used, but a photodetector or detector element capable of detecting the number of photons is preferred. In the third configuration example, functions (such as cooling or variable bias) for improving and changing the characteristics of the detector can be provided.

[0364] <1-21-4. Photodetector performance>

[0365] Hereinafter, the performance of the photodetector according to the above configuration will be described. Hereinafter, the relationship between the number of elements of the photodetector and the maximum light detection rate will be described, and a theoretical estimation of the maximum light detection rate by using a plurality of elements as the photodetector will be described. First, Fig.34 is a diagram illustrating an example of photodetector performance in a single element. Fig.34 Light detection efficiency, dark count rate, dead time, light detection time width, etc. are illustrated as examples as indicators indicating the performance of a hypothetical single element of the photodetector.

[0366] First, before describing the relationship between the number of elements of a photodetector and the maximum light detection rate, the premise and the like will be described. First, reference will be made to Fig.35 Describe the behavior of light detection. Fig.35 is a diagram illustrating an example of the behavior of light detection. Fig.35 In the two graphs in FIG. 1 , the horizontal axis corresponds to time t, and the vertical axis corresponds to the state of the detector. The roughly triangular shape in each graph corresponds to the light reaction in the detector.

[0367] like Fig.35As shown in the graph on the left, once a detector with single-photon-level light detection sensitivity (photomultiplier tube (PPMT), SPAD, superconducting single-photon detector (SSPD), transition edge sensor (TES), etc.) detects light, a dead time T occurs during which light detection is temporarily impossible. DT .like Fig.35 As shown in the right graph in , when the rate of light reaching the detector increases, the dead time increases, and the time during which light detection cannot be performed increases. Fig.35 As shown in the graph on the right, events can occur that the detector reacts to but cannot detect.

[0368] like Fig.36 As shown in FIG. , when more than T has passed since the last light detection DT When the time comes, light can be detected. Fig.36 is a diagram illustrating an example of a situation where light can be detected. Fig.37 As shown in FIG. , when the time elapsed from the previous light detection is T DT When the range is less than 100 ms, no light can be detected. Fig.37 is a diagram illustrating an example of a case where light cannot be detected.

[0369] In the following, reference will be made to Fig.38 A light detection model describing light detection. Fig.38 is a diagram illustrating an example of a light detection model. The light detection time of the detector has a width T window , so even if a photon reacts with the detector at a specific time, it is not possible to specify that the reaction occurred at T window Therefore, it is considered that the light is at T window Suppose the instantaneous speed of light is R impulse . Assuming that a photon travels at time T window When the diffusion is uniform, T window The speed of light R impulse It is expressed by the following expression (7).

[0370] R impulse =1 / T window …(7)

[0371] The probability of light detection is given by the detector when it is exposed to R impulse The probability that light detection occurs at time T is obtained as shown in the following expression (8).

[0372] P(T)=1-exp[(η PDE R impulse +R DCR )T] …(8)

[0373] Here, RDCR is the dark count rate of the photodetector in the absence of light input. In the following, the light detection probability expressed by the following expression (9) is used, where time T = T window .

[0374] P D =P(T window )=1-exp[(η PDE R impulse +R DCR )T window ] …(9)

[0375] Will refer to Fig.39 Describes the probability that the detector is ready to detect light and the probability that the detector detects light. Fig.39 is a diagram illustrating an example of deriving a light detection rate. Fig.39 As shown in pulse The probability of detecting light when the photodetector is fed into the photodetector (the detector is DT The probability that the detector detects light is expressed by the following expression (11).

[0376] P ND (R pulse , T DT )=exp[-(η PDE R pulse +R DCR )T DT ] …(10)

[0377] P D =1-exp[(η PDE R impulse +R DCR )T window ] …(11)

[0378] Based on the above, the probability of light detection is expressed by the following expression (12).

[0379] P ND (R pulse , T DT ) D =exp[-(η PDE R pulse +R DCR )T DT ]

[0380] {1-exp[(η PDE R impulse +R DCR )T window ]} …(12)

[0381] The rate of light detection can be obtained simply by multiplying the above expression by the light incident rate. Therefore, it is obtained as the following expression (13).

[0382] R detect =R pulse exp[-(η PDE R pulse +R DCR )T DT ]{1-exp[(η PDE R impulse +R DCR )T window ]} …(13)

[0383] From here on, the probability of light detection occurring in a SPAD with multiple elements will be described. Fig.40 and Fig.31 As shown in , light input to the SPAD is diffused by a plurality of SPADs constituting a photodetector. Fig.40 is a diagram illustrating an example of a light detection model in a case where a photodetector includes a plurality of elements. Fig.41 is a diagram illustrating an example of a light detection model in a case where a photodetector includes a plurality of elements.

[0384] The probability of detection of light scattered in each SPAD occurring is expressed by the following expression (14).

[0385]

[0386] The probability that detection of light scattered by any SPAD occurs once is expressed by the following expression (15).

[0387]

[0388] Due to quantum fluctuations of light and measurement uncertainty, multiple detection events may occur. Since the detection of one photon is expected, multiple detection events are rejected. In this case, for example, Fig.42 As shown in , multiple detection events are rejected because one photon is detected. Fig.42 is a diagram illustrating an example of scattered light and detection of multiple elements.

[0389] Based on the above, the maximum light detection rate relative to the number of elements is calculated. For example, the maximum light detection rate is calculated in the following two steps (step #1 and step #2).

[0390] In step #1, the term (R maxpulse ).

[0391]

[0392] In step #2, replace the term (R max pulse ) is input to the photodetector as the expected value of the light detection rate as the maximum light detection rate R max Obtained as shown in the following expression (17).

[0393]

[0394] Through the above calculation of the maximum light detection rate, we can get Fig.43 and Fig.44 The maximum light detection rate due to the difference in the number of photodetector elements is shown in . Fig.43 and Fig.44 is a diagram illustrating an example of calculation of the maximum light detection rate with respect to the number of elements. Fig.43 is a diagram illustrating, in a table format, an example of calculation of the maximum light detection rate with respect to the number of elements. Fig.44 is a diagram illustrating, in a graph form, an example of calculation of the maximum light detection rate with respect to the number of elements.

[0395] and Fig.43 and Fig.44 As with the maximum light detection rate due to the difference in the number of elements shown in , the maximum detection rate increases roughly in proportion to the number of elements. As described above, with respect to photodetector performance, this rate is calculated as described above, and based on this indicator, it can be seen that performance is improved by increasing the number of detectors.

[0396] <2. Modification example>

[0397] The control device that controls the detection system 1 , the sensing system 10 , etc. (measuring device) of the present embodiment may be implemented by a dedicated computer system or a general-purpose computer system.

[0398] For example, a program for performing the above-mentioned operation is stored in a computer-readable recording medium such as an optical disk, a semiconductor memory, a magnetic tape, or a floppy disk and distributed. Then, for example, by installing the program in a computer and performing the above-mentioned processing, the control device can be configured. At this time, the control device can be a device (for example, a personal computer) outside the detection system 1, the sensing system 10, etc. (measuring device). In addition, the control device can be a device (for example, a processor) inside the detection system 1, the sensing system 10, etc. (measuring device).

[0399] In addition, the above program may be stored in a disk device included in a server on a network such as the Internet, so that the communication program can be downloaded to a computer. In addition, the above functions may be implemented by the cooperation of an operating system (OS) and application software. In this case, the portion other than the OS may be stored in a medium and distributed, or the portion other than the OS may be stored in a server, and downloading to a computer, etc. may be performed.

[0400] In addition, among the processes described in the above embodiments, all or part of the processes described as being automatically performed may be performed manually, or all or part of the processes described as being manually performed may be automatically performed by well-known methods. In addition, unless otherwise specified, the processes, specific names, and information including various data and parameters shown in the above documents and drawings may be optionally changed. For example, the various types of information depicted in each figure are not limited to the depicted information.

[0401] In addition, each component of each device depicted in the figure is conceptual in function and is not necessarily physically configured as depicted in the figure. That is, the specific form of distribution and integration of each device is not limited to the illustrated form, and all or part of it can be functionally or physically distributed and integrated in any unit according to various loads, usage conditions, etc. It is noted that such configuration by distribution and integration can be performed dynamically.

[0402] In addition, in a field where the processing contents do not contradict each other, the above-described embodiments can be appropriately combined. In addition, the order of each step shown in the flowchart of the above-described embodiment can be appropriately changed.

[0403] In addition, for example, the present embodiment can be implemented as any configuration constituting a device or a system, such as a processor as a system large-scale integrated circuit (LSI) or the like, a module using a plurality of processors or the like, a unit using a plurality of modules or the like, a collection obtained by further adding other functions to a unit, etc. (i.e., a configuration of a part of a device).

[0404] Note that in this embodiment, a system refers to a collection of multiple components (devices, modules (parts), etc.), and it is not important whether all components are located in the same housing. Therefore, multiple devices housed in separate housings and connected via a network and one device housing multiple modules in one housing are both systems.

[0405] Furthermore, for example, the present embodiment may adopt a configuration of cloud computing in which one function is shared and processed by a plurality of devices cooperating via a network.

[0406] <3. Conclusion>

[0407] As described above, according to an embodiment of the present disclosure, a detection system is a system for receiving quantum entangled light from one or more paths. The detection system includes one or more beam splitters that cause quantum entangled light to interfere, light receiving elements arranged corresponding to corresponding paths branched from a plurality of splitters including at least a beam splitter, and a measuring instrument for detecting corresponding detection timings of photons in the plurality of light receiving elements.

[0408] In addition, according to an embodiment of the present disclosure, a detection system is a system for receiving quantum entangled light from multiple paths. The detection system includes multiple beam splitters that cause quantum entangled light to interfere, light receiving elements that are arranged corresponding to the corresponding paths branched from the beam splitters, and a measuring instrument that detects the corresponding detection timing of photons in the multiple light receiving elements.

[0409] In addition, according to an embodiment of the present disclosure, the detection system is a system for receiving quantum entangled light. The detection system includes a beam splitter that causes quantum entangled light to interfere, a plurality of polarization beam splitters that branch the quantum entangled light after interference by the beam splitter in a polarization state, light receiving elements that are arranged corresponding to the paths branched from the polarization beam splitters, and a measuring instrument that detects the corresponding detection timing of photons in the plurality of light receiving elements.

[0410] In addition, according to an embodiment of the present disclosure, the sensing system is a system that receives quantum entangled light from one or more paths. The detection system includes one or more beam splitters that cause quantum entangled light to interfere, light receiving elements that are arranged corresponding to the corresponding paths branched from the plurality of splitters including at least the beam splitters, a branching unit that branches the light to introduce into the plurality of light receiving elements, and a measuring instrument that detects the corresponding detection timing of photons in the plurality of light receiving elements.

[0411] In addition, according to an embodiment of the present disclosure, the sensing system includes a quantum entanglement light source that outputs at least two photons in a quantum entangled state, and a quantum entanglement generator that detects the detection timing of the photons through a light receiving element that is provided corresponding to a path branched from at least one beam splitter that causes quantum entangled light interference. Among a first light guide path that applies one of the two photons to an observation target, a second light guide path that guides the photon returned from the observation target to the beam splitter, and a third light guide path that guides the other of the two photons to the beam splitter, the quantum entanglement generator receives light from the second light guide path and the third light guide path.

[0412] Therefore, the number of quantum entanglement attempts per unit time can be increased, and thus the efficiency of quantum entanglement formation per unit time can be improved.

[0413] Although the embodiments of the present disclosure have been described above, the technical scope of the present disclosure is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present disclosure. In addition, components of different embodiments and modified examples can be appropriately combined.

[0414] Furthermore, the effects in the embodiments described in the present description are merely examples and are not limited, and other effects may also be provided.

[0415] <4. Effects of the present disclosure>

[0416] As described above, the measuring device according to the present disclosure (in the embodiment, the detection system 1, etc.) is a measuring device that receives quantum entangled light from one or more paths, and includes one or more beam splitters (in the embodiment, beam splitter 4, etc., and the same applies hereinafter) that cause quantum entangled light to interfere, light receiving elements (in the embodiment, photodetector 7, etc., and the same applies hereinafter) that are arranged corresponding to corresponding paths branched off from multiple splitters including at least a beam splitter (in the embodiment, beam splitter 4, polarization beam splitter 5, etc., and the same applies hereinafter), and a measuring instrument (in the embodiment, post-selector 8, etc., and the same applies hereinafter) that detects the corresponding detection timing of photons in the multiple light receiving elements.

[0417] As described above, the measuring device according to the present disclosure detects the corresponding detection timing of photons in the light receiving element corresponding to the paths branched from the multiple splitters including the beam splitter causing quantum entangled light interference, so that quantum entanglement can be generated and detection can be performed by a simple configuration. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0418] As described above, the measuring device according to the present disclosure (in an embodiment, the detection system 1, etc.) is a measuring device that receives quantum entangled light from multiple paths, and includes multiple beam splitters that cause quantum entangled light to interfere, light receiving elements that are arranged corresponding to the corresponding paths branched from the beam splitters, and a measuring instrument that detects the corresponding detection timing of photons in the multiple light receiving elements.

[0419] As described above, the measuring device according to the present disclosure detects the corresponding detection timing of photons in the light receiving element arranged corresponding to the paths branched from the multiple beam splitters causing quantum entangled light interference, so that quantum entanglement can be generated and detection can be performed with a simple configuration. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0420] As described above, the measuring device according to the present disclosure (in an embodiment, detection system 1A, etc.) is a measuring device for receiving quantum entangled light, and includes a beam splitter that causes quantum entangled light to interfere, multiple polarization beam splitters that branch the quantum entangled light after interference by the beam splitter in a polarization state, light receiving elements arranged corresponding to the corresponding paths branched by the polarization beam splitter, and a measuring instrument that detects the corresponding detection timing of photons in the multiple light receiving elements.

[0421] As described above, the measuring device according to the present disclosure detects the corresponding detection timing of photons in the light receiving element set corresponding to the path branched from the beam splitter and the plurality of polarization beam splitters that cause quantum entangled light interference, so that quantum entanglement can be generated and detection can be performed with a simple configuration. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0422] As described above, the measuring device according to the present disclosure (in an embodiment, detection system 1B, etc.) is a measuring device that receives quantum entangled light from one or more paths, and includes one or more beam splitters that cause quantum entangled light to interfere, light receiving elements arranged corresponding to corresponding paths branched from multiple splitters including at least a beam splitter, a branching unit that branches light to introduce it into multiple light receiving elements (in an embodiment, light branching unit 6, etc. The same applies hereinafter), and a measuring instrument that detects the corresponding detection timing of photons in multiple light receiving elements.

[0423] As described above, the measuring device according to the present disclosure branches light to be introduced into the light receiving element set corresponding to the path branched from the multiple splitters including the beam splitter causing quantum entangled light interference, and detects the corresponding detection timing of the photon in the light receiving element, so that quantum entanglement can be generated and detection can be performed by a simple configuration. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0424] In addition, the measuring apparatus includes a pre-processing unit (in the embodiment, first processing unit 2, second processing unit 3, etc. The same applies hereinafter) that performs processing on the quantum entangled light before being branched by the beam splitter.

[0425] As described above, the measurement device according to the present disclosure performs processing on quantum entangled light before branching by the beam splitter, so that quantum entanglement can be generated and detected by appropriate processing. Therefore, the measurement device can enable efficient generation of quantum entanglement.

[0426] In addition, the pre-processing unit performs at least one of wavelength conversion, wavelength selection or unitary conversion on the quantum entangled light.

[0427] As described above, the measuring device according to the present disclosure performs at least one of wavelength conversion, wavelength selection or unitary conversion on quantum entangled light, so that quantum entanglement can be generated and detected by appropriate processing. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0428] In addition, the measuring apparatus includes a post-processing unit (in the embodiment, the first processing unit 2, etc. The same applies hereinafter) that performs processing on the quantum entangled light after interference by the beam splitter after being branched by the beam splitter.

[0429] As described above, the measuring device according to the present disclosure processes the quantum entangled light after interference by the beam splitter after branching by the beam splitter, so that quantum entanglement can be generated and detected by appropriate processing. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0430] Furthermore, the post-processing unit performs at least one of wavelength conversion and wavelength selection on the quantum entangled light after interference by the beam splitter.

[0431] As described above, the measuring device according to the present disclosure performs at least one of wavelength conversion or wavelength selection on the quantum entangled light after interference by the beam splitter, so that quantum entanglement can be generated and detected by appropriate processing. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0432] In addition, the light receiving element includes a plurality of detection units (in the embodiment, the detection unit 70 , the area AR, etc.; the same applies hereinafter) that detect the light branched by the branching unit.

[0433] As described above, the measuring apparatus according to the present disclosure detects the respective detection timings of photons in the plurality of detection units that detect light branched by the branching unit, and thus can appropriately perform detection.

[0434] In addition, the plurality of detection units are a plurality of elements that detect the light branched by the branching unit.

[0435] As described above, the measuring apparatus according to the present disclosure detects the respective detection timings of photons in a plurality of elements that detect light branched by a branching unit, and thus detection can be appropriately performed.

[0436] In addition, the branching unit is a splitter that branches and introduces light into each of a plurality of elements.

[0437] As described above, the measuring apparatus according to the present disclosure detects respective detection timings of photons in a plurality of detection units that detect light branched by a spectrometer that branches and introduces light into each of a plurality of elements, and thus can appropriately perform detection.

[0438] In addition, the light receiving element is an array element, and the plurality of detection units are a plurality of regions of a light receiving surface of the array element.

[0439] As described above, the measuring apparatus according to the present disclosure detects the respective detection timings of photons in a plurality of regions of the light receiving surface of the array element, and thus the detection can be appropriately performed.

[0440] In addition, the branching unit is an optical member that branches and introduces light into each of a plurality of regions of the array element.

[0441] As described above, the measuring device according to the present disclosure detects the respective detection timings of photons in a plurality of detection units, wherein the plurality of detection units detect light branched by an optical member that branches and introduces light into each of a plurality of regions of an array element, thereby making it possible to appropriately perform detection.

[0442] As described above, the measuring device according to the present disclosure (in an embodiment, the sensing system 10, etc.) includes a quantum entangled light source (in an embodiment, the quantum entangled light source 30, etc.) that outputs at least two photons in a quantum entangled state, and a quantum entanglement generator (in an embodiment, the quantum entanglement generator 1F, etc.; the same applies hereinafter) that detects the detection timing of the photons through a light receiving element arranged corresponding to a path branched from at least one beam splitter that causes quantum entangled light interference, wherein among a first light guiding path that applies one of the two photons to an observation target, a second light guiding path that guides the photon returned from the observation target to the beam splitter, and a third light guiding path that guides the other of the two photons to the beam splitter, the quantum entanglement generator receives light from the second light guiding path and the third light guiding path.

[0443] As described above, the measuring device according to the present disclosure detects the corresponding detection timing of photons in the light receiving element set corresponding to the path branched from at least one beam splitter causing quantum entangled light interference, so that quantum entanglement can be generated and detection can be performed by a simple configuration. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0444] In addition, the measuring device includes a sum frequency generating unit (in the embodiment, sum frequency generator 40, etc. The same applies hereinafter) arranged in at least one of the second light guiding path or the third light guiding path.

[0445] As described above, the measuring device according to the present disclosure performs processing related to generation of the sum frequency in at least one of the second light guiding path or the third light guiding path, and thus can appropriately perform detection.

[0446] In addition, the measuring device includes a phase adjustment unit (in the embodiment, a phase adjuster 25, etc. The same applies hereinafter) arranged in at least one of the second light guiding path or the third light guiding path.

[0447] As described above, the measuring device according to the present disclosure performs the process related to the phase adjustment in at least one of the second light guiding path or the third light guiding path, so that the detection can be appropriately performed.

[0448] In addition, the measuring device includes a bandpass filter (in the embodiment, the bandpass filter 50 , etc. The same applies hereinafter) arranged in at least one of the second light guiding path or the third light guiding path.

[0449] As described above, the measuring device according to the present disclosure performs frequency-dependent processing in at least one of the second light guiding path or the third light guiding path, and thus can appropriately perform detection.

[0450] In addition, the measuring apparatus includes an excitation light source (in the embodiment, the excitation light source 35 or the like. The same applies hereinafter) that outputs excitation light to the observation target.

[0451] As described above, the measuring device according to the present disclosure can perform more sensing related to excitation by outputting excitation light to an observation target, and can appropriately perform detection.

[0452] In addition, the quantum entanglement generator includes one or more beam splitters that cause quantum entangled light interference, light receiving elements arranged corresponding to corresponding paths branched from multiple splitters including at least the beam splitters, and a measuring instrument that detects the corresponding detection timing of photons in the multiple light receiving elements.

[0453] As described above, the measuring device according to the present disclosure detects the corresponding detection timing of photons in the light receiving element corresponding to the paths branched from the multiple splitters including the beam splitter causing quantum entangled light interference, so that quantum entanglement can be generated and detection can be performed by a simple configuration. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0454] In addition, the quantum entanglement generator includes one or more beam splitters that cause quantum entangled light interference, light receiving elements arranged corresponding to corresponding paths branched out from multiple splitters including at least the beam splitters, a branching unit that branches light to introduce it into multiple light receiving elements, and a measuring instrument that detects the corresponding detection timing of photons in the multiple light receiving elements.

[0455] As described above, the measuring device according to the present disclosure branches light to be introduced into the light receiving element set corresponding to the path branched from the multiple splitters including the beam splitter causing quantum entangled light interference, and detects the corresponding detection timing of the photon in the light receiving element, so that quantum entanglement can be generated and detection can be performed by a simple configuration. Therefore, the measuring device can enable efficient generation of quantum entanglement.

[0456] <5. Hardware Configuration>

[0457] Various information processing devices such as a control device and a signal processing device in the detection system 1, the sensing system 10, etc. according to the above-described embodiment and the modified example are composed of, for example, a control device having Fig.45 The invention is implemented by a computer 1000 having the configuration shown in FIG. Fig.45 1000 is a hardware configuration diagram of an example of a computer that implements the functions of an information processing device. The computer 1000 includes a CPU 1100, a RAM 1200, a read-only memory (ROM) 1300, a hard disk drive (HDD) 1400, a communication interface 1500, and an input / output interface 1600. Each unit of the computer 1000 is connected via a bus 1050.

[0458] The CPU 1100 operates based on the program stored in the ROM 1300 or the HDD 1400 and controls each unit. For example, the CPU 1100 develops the program stored in the ROM 1300 or the HDD 1400 in the RAM 1200 and executes processing corresponding to the various programs.

[0459] The ROM 1300 stores a boot program such as a basic input output system (BIOS) executed by the CPU 1100 when the computer 1000 is activated, a program depending on the hardware of the computer 1000 , and the like.

[0460] The HDD 1400 is a computer-readable recording medium that non-transitorily records a program executed by the CPU 1100 , data used by such a program, etc. Specifically, the HDD 1400 is a recording medium that records an information processing program according to the present disclosure as an example of the program data 1450 .

[0461] The communication interface 1500 is an interface for connecting the computer 1000 to an external network 1550 (eg, the Internet). For example, the CPU 1100 receives data from another device via the communication interface 1500 or transmits data generated by the CPU 1100 to another device.

[0462] The input-output interface 1600 is an interface for connecting the input-output device 1650 and the computer 1000. For example, the CPU 1100 receives data from input devices such as a keyboard and a mouse via the input-output interface 1600. In addition, the CPU 1100 transmits data to output devices such as a display, a speaker, or a printer via the input-output interface 1600. In addition, the input-output interface 1600 can be used as a medium interface for reading a program recorded in a predetermined recording medium. The medium is, for example, an optical recording medium such as a digital versatile disk (DVD) or a phase-change rewritable disk (PD), a magneto-optical recording medium such as a magneto-optical disk (MO), a magnetic tape medium, a magnetic recording medium, a semiconductor memory, etc.

[0463] For example, in the case where the computer 1000 is used as a control device in the detection system 1, the sensing system 10, etc., the CPU 1100 of the computer 1000 executes the information processing program loaded on the RAM 1200 to realize the functions of the control unit of the control device, etc. In addition, the HDD 1400 stores the information processing program according to the present disclosure and the data in the storage unit of the control device. Note that the CPU 1100 reads the program data 1450 from the HDD 1400 and executes the program data 1450, but as another example, these programs can be acquired from another device via the external network 1550.

[0464] Note that the present technology may also have the following configurations. (1)

[0466] A measurement device for receiving quantum entangled light from one or more paths, the measurement device comprising:

[0467] one or more beam splitters that cause the quantum entangled light to interfere;

[0468] a plurality of light receiving elements provided corresponding to respective paths branched by a plurality of splitters including at least the beam splitter;

[0469] a branching unit that randomly disperses photons among the plurality of light receiving elements; and

[0470] A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements. (2)

[0472] A measuring device for receiving quantum entangled light from multiple paths, the measuring device comprising:

[0473] a plurality of beam splitters that cause quantum entangled light to interfere;

[0474] light receiving elements provided corresponding to respective paths branched by the beam splitter; and

[0475] A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements. (3)

[0477] A measuring device for receiving quantum entangled light, the measuring device comprising:

[0478] a beam splitter that causes the quantum entangled light to interfere;

[0479] A plurality of polarization beam splitters that branch the quantum entangled light after interference by the beam splitters according to polarization states;

[0480] light receiving elements provided corresponding to respective paths branched by the polarization beam splitter; and

[0481] A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements. (4)

[0483] A measurement device for receiving quantum entangled light from one or more paths, the measurement device comprising:

[0484] one or more beam splitters that cause the quantum entangled light to interfere;

[0485] a light receiving element disposed corresponding to respective paths branched by a plurality of splitters including at least the beam splitter;

[0486] a branching unit that branches light to be introduced into the plurality of light receiving elements; and

[0487] A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements. (5)

[0489] The measuring device according to any one of (1) to (4), comprising:

[0490] A pre-processing unit performs processing on the quantum entangled light before being branched by the beam splitter. (6)

[0492] The measuring device according to (5), wherein

[0493] The pre-processing unit performs at least one of wavelength conversion, wavelength selection or unitary conversion on the quantum entangled light. (7)

[0495] The measuring device according to (5) or (6), comprising:

[0496] A post-processing unit performs processing on the quantum entangled light after being interfered by the beam splitter after being branched by the beam splitter. (8)

[0498] The measuring device according to (7), wherein

[0499] The post-processing unit performs at least one of wavelength conversion and wavelength selection on the quantum entangled light after interference by the beam splitter. (9)

[0501] The measuring device according to (4), wherein

[0502] The light receiving element includes a plurality of detection units that detect the light branched by the branching unit. (10)

[0504] The measuring device according to (9), wherein

[0505] The plurality of detection units are a plurality of elements that detect the light branched by the branching unit. (11)

[0507] The measuring device according to (10), wherein

[0508] The branching unit is a splitter that branches and introduces light into each of the plurality of elements. (12)

[0510] The measuring device according to (9), wherein

[0511] The light receiving element is an array element, and

[0512] The plurality of detection units are a plurality of regions of a light receiving surface of the array element. (13)

[0514] The measuring device according to (12), wherein

[0515] The branching unit is an optical member that branches and introduces light into each of the plurality of regions of the array element. (14)

[0517] A measuring device comprising:

[0518] A quantum entangled light source that outputs at least two photons in a quantum entangled state; and

[0519] A quantum entanglement generator that detects the detection timing of photons by a light receiving element, the light receiving element being arranged corresponding to a path branched by at least one beam splitter that causes quantum entangled light to interfere, wherein

[0520] In a first light-guiding path that applies one of the two photons to the observation target, a second light-guiding path that guides the photon returned from the observation target to the beam splitter, and a third light-guiding path that guides the other of the two photons to the beam splitter, the quantum entanglement generator receives light from the second light-guiding path and the third light-guiding path. (15)

[0522] The measuring device according to (14), comprising:

[0523] A sum frequency generating unit is arranged in at least one of the second light guiding path or the third light guiding path. (16)

[0525] The measuring device according to (14) or (15), comprising:

[0526] A phase adjustment unit is arranged in at least one of the second light guiding path or the third light guiding path. (17)

[0528] The measuring device according to any one of (14) to (16), comprising:

[0529] A bandpass filter is arranged in at least one of the second light guiding path or the third light guiding path. (18)

[0531] The measuring device according to any one of (14) to (17), comprising:

[0532] An excitation light source outputs excitation light toward the observation target. (19)

[0534] The measuring device according to any one of (14) to (18), wherein

[0535] The quantum entanglement generator comprises:

[0536] one or more beam splitters that cause the quantum entangled light to interfere;

[0537] light receiving elements provided corresponding to respective paths branched by a plurality of splitters including at least the beam splitter; and

[0538] A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements. (20)

[0540] The measuring device according to any one of (14) to (18), wherein

[0541] The quantum entanglement generator comprises:

[0542] one or more beam splitters that cause the quantum entangled light to interfere;

[0543] a light receiving element disposed corresponding to respective paths branched by a plurality of splitters including at least the beam splitter;

[0544] a branching unit that branches light to be introduced into the plurality of light receiving elements; and

[0545] A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements.

[0546] Reference numerals list

[0547] 1 Detection system (measurement equipment and quantum entanglement generator)

[0548] 2. First processing unit

[0549] 3 Second processing unit

[0550] 4 Beam Splitter (BS)

[0551] 5 Polarization Beam Splitter (PBS)

[0552] 6 Optical branching unit

[0553] 7 Photodetector

[0554] 8 After selection

[0555] 9. Reflector

[0556] 10 Sensing system (measuring equipment)

[0557] 20 Phase Modulator

[0558] 25 Phase Adjuster

[0559] 30 Quantum entangled light source

[0560] 35 Excitation light source

[0561] 40 Sum frequency generator

[0562] 50 Band Pass Filter (BPF)

Claims

1. A measuring device for receiving quantum entangled light from one or more paths, the measuring device comprising: one or more beam splitters that cause the quantum entangled light to interfere; a plurality of light receiving elements provided corresponding to respective paths branched by a plurality of splitters including at least the beam splitter; a branching unit that randomly disperses photons among the plurality of light receiving elements; and A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements.

2. A measuring device for receiving quantum entangled light from multiple paths, the measuring device comprising: a plurality of beam splitters that cause quantum entangled light to interfere; light receiving elements disposed corresponding to respective paths branched by the beam splitter; as well as A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements.

3. A measuring device for receiving quantum entangled light, the measuring device comprising: a beam splitter that causes the quantum entangled light to interfere; A plurality of polarization beam splitters that branch the quantum entangled light after interference by the beam splitters according to polarization states; light receiving elements provided corresponding to respective paths branched by the polarization beam splitter; and A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements.

4. A measurement device for receiving quantum entangled light from one or more paths, the measurement device comprising: one or more beam splitters that cause the quantum entangled light to interfere; a light receiving element disposed corresponding to respective paths branched by a plurality of splitters including at least the beam splitter; a branching unit that branches the light to be introduced into the plurality of light receiving elements; as well as A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements.

5. The measuring device according to claim 1, comprising: A pre-processing unit performs processing on the quantum entangled light before being branched by the beam splitter.

6. The measuring device according to claim 5, wherein The pre-processing unit performs at least one of wavelength conversion, wavelength selection or unitary conversion on the quantum entangled light.

7. The measuring device according to claim 5, comprising: A post-processing unit performs processing on the quantum entangled light after being interfered by the beam splitter after being branched by the beam splitter.

8. The measuring device according to claim 7, wherein The post-processing unit performs at least one of wavelength conversion and wavelength selection on the quantum entangled light after interference by the beam splitter.

9. The measuring device according to claim 4, wherein The light receiving element includes a plurality of detection units that detect the light branched by the branching unit.

10. The measuring device according to claim 9, wherein The plurality of detection units are a plurality of elements that detect the light branched by the branching unit.

11. The measuring device according to claim 10, wherein The branching unit is a splitter that branches and introduces light into each of the plurality of elements.

12. The measuring device according to claim 9, wherein The light receiving element is an array element, and The plurality of detection units are a plurality of regions of a light receiving surface of the array element.

13. The measuring device according to claim 12, wherein The branching unit is an optical member that branches and introduces light into each of the plurality of regions of the array element.

14. A measuring device comprising: A quantum entangled light source, which outputs at least two photons in a quantum entangled state; as well as A quantum entanglement generator that detects the detection timing of photons by a light receiving element, the light receiving element being arranged corresponding to a path branched by at least one beam splitter that causes quantum entangled light to interfere, wherein In a first light-guiding path that applies one of the two photons to the observation target, a second light-guiding path that guides the photon returned from the observation target to the beam splitter, and a third light-guiding path that guides the other of the two photons to the beam splitter, the quantum entanglement generator receives light from the second light-guiding path and the third light-guiding path.

15. The measuring device according to claim 14, comprising: A sum frequency generating unit is arranged in at least one of the second light guiding path or the third light guiding path.

16. The measuring device according to claim 14, comprising: A phase adjustment unit is arranged in at least one of the second light guiding path or the third light guiding path.

17. The measuring device according to claim 14, comprising: A bandpass filter is arranged in at least one of the second light guiding path or the third light guiding path.

18. The measuring device according to claim 14, comprising: An excitation light source outputs excitation light toward the observation target.

19. The measuring device according to claim 14, wherein The quantum entanglement generator comprises: one or more beam splitters that cause the quantum entangled light to interfere; a light receiving element disposed corresponding to respective paths branched by a plurality of splitters including at least the beam splitter; as well as A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements.

20. The measuring device according to claim 14, wherein The quantum entanglement generator comprises: one or more beam splitters that cause the quantum entangled light to interfere; a light receiving element disposed corresponding to respective paths branched by a plurality of splitters including at least the beam splitter; a branching unit that branches the light to be introduced into the plurality of light receiving elements; as well as A measuring instrument detects respective detection timings of photons in the plurality of light receiving elements.

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