Optical devices, systems, methods, and storage media for quantum computing

Abstract

The application discloses an optical device, system, method and storage medium for quantum computing, and relates to the technical field of quantum computing. The device comprises: a delay generation module for generating different time delays for n photons respectively, so that the n photons arrive at an active optical element at different times; a fiber collimation module for converting light rays of the n photons into n collimated light transmissions; a quasi-space mode generation module for making the light rays of the n photons pass through the same active optical element in sequence, and the active optical element is used for sequentially modulating and processing optical signals of the n photons according to the time sequence of the arrival of the n photons; and a feedforward measurement module for performing polarization measurement on the modulated and processed optical signal of a first photon, and obtaining a measurement result, which is used for feedforward compensation or feedforward error correction on a measurement result of a second photon to be measured. The application can effectively reduce the number of active optical elements and reduce the cost of quantum devices.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of quantum computing, and particularly relate to an optical device, system, method and storage medium for quantum computing. BACKGROUND

[0002] Measurement Based Quantum Computing (MBQC) is a quantum computing method based on a highly entangled cluster state as a quantum computing resource.

[0003] In related technologies, the measurement based quantum computing method measures the polarization state of multiple photons through a light sensing element. Since the quanta of the cluster state have entanglement, each measured quantum measures a random result, which has an impact on the quantum that needs to be measured next. According to the measurement result of the previous quantum, the measurement result of the subsequent quantum is fed forward, and a relatively accurate value can be obtained.

[0004] However, in related technologies, a large number of active optical elements for measuring quanta are needed to implement measurement based quantum computing, and the quantum device is large in volume and high in cost. SUMMARY

[0005] Embodiments of the present application provide an optical device, system, method and storage medium for quantum computing, which can reduce the number of active optical elements for measuring quantum data and reduce costs. The technical solution is as follows:

[0006] According to an aspect of an embodiment of the present application, an optical device for quantum computing is provided, the device comprising: a delay generation module, a fiber collimation module, a quasi-space mode generation module and a feedforward measurement module, the feedforward measurement module comprising an active optical element for modulating and processing an optical signal;

[0007] The delay generation module is configured to generate different time delays for n photons respectively, so that the n photons arrive at the active optical element at different times, n being an integer greater than 1;

[0008] The fiber collimation module is configured to convert the light rays of the n photons into n collimated lights propagating in free space;

[0009] The quasi-space mode generation module is configured to control the light rays of the n photons propagating in free space to pass through the same active optical element in turn, and the active optical element is configured to modulate and process the optical signals of the n photons in turn according to the time sequence of the n photons arriving at the active optical element;

[0010] The feedforward measurement module is configured to perform polarization measurement on the light signal of the first photon after modulation processing to obtain a measurement result of the first photon, and the measurement result of the first photon is used for feedforward compensation or feedforward error correction on a measurement result of a second photon to be measured, wherein the first photon is one of the n photons, and the second photon is a next photon to be measured after the first photon.

[0011] According to an aspect of some embodiments of the present application, there is provided a quantum computing system, the system comprising an optical device for quantum computing as described above.

[0012] According to an aspect of some embodiments of the present application, there is provided an active optical feedforward method of multi-photon mode, the method being applied in an optical device for quantum computing, the device comprising a delay generation module, a fiber collimation module, a quasi-space mode generation module, and a feedforward measurement module, the feedforward measurement module comprising an active optical element for performing modulation processing on a light signal;

[0013] The method comprises:

[0014] The delay generation module generates different time delays for n photons respectively, so that the n photons arrive at the active optical element at different time points, n being an integer greater than 1;

[0015] The fiber collimation module converts the light rays of the n photons into n collimated lights propagating in free space;

[0016] The quasi-space mode generation module controls the light rays of the n photons propagating in free space to sequentially pass through the same active optical element, and the active optical element is configured to sequentially perform modulation processing on the light signals of the n photons according to the time sequence of the n photons arriving at the active optical element;

[0017] The feedforward measurement module performs polarization measurement on the light signal of a first photon after modulation processing to obtain a measurement result of the first photon, and the measurement result of the first photon is used for feedforward compensation or feedforward error correction on a measurement result of a second photon to be measured, wherein the first photon is one of the n photons, and the second photon is a next photon to be measured after the first photon.

[0018] According to an aspect of some embodiments of the present application, there is provided a computer readable storage medium, the computer readable storage medium storing at least one instruction, at least one program, a code set or an instruction set, the at least one instruction, the at least one program, the code set or the instruction set being loaded and executed by a processor to implement the active optical feedforward method of multi-photon mode as described above.

[0019] According to an aspect of the embodiments of the present application, a computer program product is provided, which includes at least one instruction, at least one program, a code set or an instruction set, which is loaded and executed by a processor to implement the active optical feedforward method of the multi-photon mode as described above.

[0020] The technical solutions provided by the embodiments of the present application can bring the following beneficial effects:

[0021] The delay generation module makes the multiple photons in the cluster state entangled with each other have different time delays; and the quasi-space mode generation module makes the multiple photons be in quasi-space modes with very close spatial distances but not overlap, so that the system only needs to use one active optical element to complete several fast feedforward operations, to realize measuring the multiple photons respectively and obtaining the measurement results corresponding to the multiple photons. The different time delays of the multiple photons make the time instants at which the different photons arrive at the feedforward measurement module different, and the feedforward measurement module measures the photons based on the time interval at which the adjacent photons arrive to obtain the measurement results, and adjusts the system based on the measurement results to realize feedforward compensation or correction. Since the same feedforward measurement module can measure the measurement results between the multiple photons in the entangled state, the number of active optical elements used in the calculation process is reduced, which helps to reduce the design difficulty of the quantum device and the cost of the quantum device.

[0022] In addition, because the multiple photons arrive at the feedforward measurement module one by one, the time interval at which the photons arrive is short, the feedforward measurement module can perform fast feedforward operation, and will not reduce the speed and calculation accuracy of quantum calculation and the security in the case of a password protocol, and will not affect the speed or universality of quantum calculation. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 is a structural block diagram of an optical device for quantum calculation provided by an embodiment of the present application;

[0025] Figure 2 is a schematic diagram of the positional relationship between the light rays of the photons provided by an embodiment of the present application;

[0026] Figure 3An embodiment of the present application provides a schematic diagram of three lens modules in a quasi-space mode generation module;

[0027] Figure 4 An embodiment of the present application provides a structural schematic diagram of an optical device for quantum computing;

[0028] Figure 5 An embodiment of the present application provides a schematic diagram of a composition of a feedforward measurement module and a relationship between a Pockels cell angle and light intensity.

[0029] Figure 6 An embodiment of the present application provides a schematic diagram of a relationship between an intensity function measured by a photodiode and a Pockels cell angle. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions and advantages of the present application clearer, the following will further describe the embodiments of the present application in combination with the drawings.

[0031] Before introducing and explaining the embodiments of the present application, first, some terms involved in the present application are explained and described.

[0032] 1. Measurement-based quantum computing: a quantum computation that encodes a computation process in a particular complex entangled state, and is realized by operating and measuring this entangled state in a particular order, including quantum state adjustment. MBQC is based on a highly entangled cluster state as a resource state of quantum computing. The computation itself is realized by continuously measuring adjacent quantum bits from the cluster state. The order of measurement, together with the measurement device, effectively realizes arbitrary single-qubit and two-qubit (or multi-qubit) operations, and defines a computer system that realizes universal quantum computation.

[0033] 2. Electro-optical modulator (EOM): a modulator made of some electro-optic crystals, such as lithium niobate crystal (LiNbO3), gallium arsenide crystal (GaAs) and lithium tantalate crystal (LiTaO3). Electro-optic effect is that when a voltage is applied to the electro-optic crystal, the refractive index of the electro-optic crystal will change, resulting in changes in the characteristics of the light wave passing through the crystal, and realizing the modulation of the phase, amplitude, intensity and polarization state of the optical signal.

[0034] 3. Acousto Optical Modulators (AOM): A kind of modulator that uses external modulation technology to control the intensity change of laser beam. The modulation signal is in the form of an electrical signal (amplitude modulation) acting on the transducer, which is then converted into a wave field that changes in the form of an electrical signal. When the light wave passes through the medium, the optical carrier is modulated to become an intensity-modulated wave "carrying" information.

[0035] 4. Pockels Cells: An electro-optical modulator based on the Pockels effect. The Pockels effect refers to the photoelectric phenomenon that the refractive index of a specific crystal is proportional to the strength of the applied electric field. By controlling the applied electric field, the refractive index in a certain direction is changed, so that the electro-optical modulation Pockels cell can work as a variable half-wave plate, thereby realizing the change of polarization state. When the electro-optical modulation Pockels cell is placed between two pieces of vertical polarizing plates, light intensity modulation can be achieved. According to the voltage application direction, the Pockels effect can be divided into longitudinal Pockels effect and transverse Pockels effect. When the voltage application direction is parallel to the light propagation direction, it is called longitudinal Pockels effect. When the voltage application direction is perpendicular to the light propagation direction, it is called transverse Pockels effect.

[0036] 5. Feed forward operation: Feed forward is an information processing technology used to process data containing errors or incompleteness and provide meaningful answers. When this technology is applied to solve real-world problems, it can improve the speed of processing information.

[0037] 6. Single Photon Detectors (SPD): A kind of ultra-low noise device used to detect the smallest energy quantum of light - photons. Single photon detectors can detect and count individual photons with enhanced sensitivity, especially suitable for emerging applications where the available signal strength is only a few photon energy levels.

[0038] 7. Optical Collimator: Used to convert the transmission light in the optical fiber into collimated light (parallel light), or to couple external parallel (approximately parallel) light into single-mode optical fiber. The optical collimator can be based on the principle of precise positioning of the tail fiber and self-focusing lens.

[0039] 8. Wave plate: An optical device that can produce an additional optical path difference (or phase difference) between two mutually perpendicular light vibrations. Wave plates are usually made of birefringent crystal plates such as quartz, calcite or mica with precise thickness, and their optical axes are parallel to the crystal plate surface.

[0040] 9. Quarter-wave plate: Also known as "quarter retardation plate", it is an optical device that makes the phase difference between the ordinary light and the extraordinary light of a certain wavelength of light 1 / 4 wavelength when the light is normally incident. It is often used in the optical path to make linearly polarized light into circularly polarized light or elliptically polarized light; or vice versa. This wave plate is usually made of birefringent material cut along the direction parallel to the optical axis to form a parallel plane plate, and its thickness should be exactly an odd multiple of the product of the refractive index difference of the two principal axes of the birefringent material and the given wavelength. The wave plate made of optically active material can also be called quarter-wave plate.

[0041] 10. Field Programmable Gate Array (FPGA): It is a programmable logic array, whose basic structure includes programmable input and output units, configurable logic blocks, digital clock management modules, embedded block random access memory (RAM), wiring resources, embedded special hard core, and bottom embedded function unit. FPGA is a further development on the basis of programmable array logic (PAL), generic array logic (GAL) and other programmable devices. It is a semi-custom circuit in the field of application specific integrated circuit (ASIC), which solves the shortcomings of custom circuits and overcomes the limitation of limited gate circuits of original programmable devices. Due to its rich wiring resources, repeatable programming, high integration and low investment, FPGA has been widely used in the field of digital circuit design. The design process of FPGA includes algorithm design, code simulation and design, board debugging. Designers and actual requirements establish algorithm architecture, use electronic design automation (EDA) to establish design scheme or write design code through hardware, ensure that the design scheme meets the actual requirements through code simulation, and finally perform board-level debugging. The relevant files are downloaded to the FPGA chip through configuration circuit to verify the actual running effect.

[0042] ​11. Polarizing beam splitter: A device that uses a combination of polarizing beam splitters instead of a traditional polarizer to make the output of a filter two beams of polarized light vibrating perpendicular to each other and spectrums complementary to each other, i.e. to produce two channels. Using multiple polarizing beam splitters in combination, a multi-channel birefringent filter can be obtained. Adjusting each channel of the multi-channel birefringent filter to pass a band of spectrums distributed continuously around a spectral line, a new type of video spectrometer can be obtained.

[0043] 12. Integrated photonics chip: A chip that combines the light-emitting properties of indium phosphide and the optical routing capabilities of silicon into a single hybrid chip, which can be used in photonic-based computer devices to enable light to enter a silicon waveguide when a voltage is applied to the indium phosphide, producing a continuous laser beam that drives other silicon photonic devices. This silicon-based laser technology can make photonicics more widely available in computers because it can be manufactured using large-scale silicon-based manufacturing techniques, which can significantly reduce costs. Although this technology is still a long way from commercialization, it is believed that in the future, tens or even hundreds of hybrid silicon lasers will be integrated with other silicon photonic components on a single silicon-based chip. This is a sign of the beginning of low-cost mass production of high-integration silicon photonic chips.

[0044] 13. Rayleigh length: In optics and laser science, the Rayleigh length or Rayleigh range is the distance over which the cross-sectional area of a laser beam, or other light beam, along its direction of propagation, changes by a factor of e (approximately 2.71828). It is defined as the distance from the waist of the beam to the position where the beam's radius is times the waist radius.

[0045] 14. Active optical element: An electronic element that changes the properties of photons (such as polarization, amplitude, etc.) by electrical energy. In this application, active optical elements refer to electro-optical modulators or acousto-optical modulators, such as electro-optical modulation Pockels cells.

[0046] In a quantum computing framework based on measurement, quantum in a highly entangled cluster state is used as a computing resource. In a feedforward measurement error correction method, the driving feedforward is realized based on a field programmable gate array driving a super high-speed active optical element (1 MHz), that is, an active optical element is needed for each feedforward operation. In the related art, when measuring multiple photons, the same number of active optical elements as the number of photons is needed to measure the multiple photons respectively to obtain the measurement results of the multiple photons. In the present application, the spatial distance between the light rays of the multiple photons is shortened so that the multiple photons can pass through the same active optical element, and the same active optical element can complete the feedforward measurement of the multiple photons. In order to change the structure of quantum computing, the number of active optical elements used in the feedforward operation is reduced in the present application. By setting different propagation path lengths for the multiple photons, the multiple photons have different time delays. When the photons propagate in the active optical element (such as an electro-optic modulator), the polarization state of the photons will change due to the refraction of the electro-optic crystal. Since the crystal structure in the electro-optic crystal is not completely uniform, reducing the spatial distance of the light rays of the multiple photons in free space can make the multiple photons pass through a certain electro-optic modulator respectively, and after being modulated by the electro-optic modulator, the change amount of the polarization state is basically the same. Therefore, the present application can minimize the influence of the non-uniformity of the electro-optic crystal of the active optical element (such as the electro-optic modulator) on the polarization state of the multiple photons. Since the standard measurement-based quantum computing method also needs to perform feedforward operation and needs to delay the quantum bits, the present application does not cause additional time loss and computing frequency limitation under the condition that the number of photons to be measured is unchanged. The technical solutions of the present application are described below through several embodiments.

[0047] Please refer to Figure 1 which shows a schematic diagram of an optical device for quantum computing provided by an embodiment of the present application. Alternatively, the device can also be referred to as a multi-photon mode active optical feedforward system. The device can include a delay generation module 10, a fiber collimation module 20, a quasi-space mode generation module 30, and a feedforward measurement module 40. The feedforward measurement module 40 includes an active optical element 41 for modulating and processing optical signals.

[0048] The delay generation module 10 is used to generate different time delays for n photons respectively, so that the n photons arrive at the active optical element 41 at different times, and n is an integer greater than 1.

[0049] Photon refers to the medium of electromagnetic interaction. In some embodiments, n photons are in a highly entangled cluster state. In the present scheme, one photon is also referred to as a single photon, and one qubit preferably corresponds to one single photon. In some embodiments, the test is performed using photons with n = 3, which proves that the present system does not introduce other errors, and n can take a larger value, and the present application does not limit the maximum range of n.

[0050] The time delay is caused by the different propagation time lengths (i.e. durations) of the n photons in the delay generation module 10. For example, in the case of n = 3, photon 1, photon 2 and photon 3 are in a highly entangled cluster state. The propagation duration of photon 1 in the delay generation module 10 is about 7.34*10 -7 s, the propagation duration of photon 2 in the delay generation module 10 is about 1.47*10 -6 s, and the propagation duration of photon 3 in the delay generation module 10 is about 2.20*10 -6 s. Due to the different propagation durations of the three photons in the delay generation module 10, the three photons have different time delays. In the embodiments of the present application, the time delay of a certain photon refers to the time difference between the time when the photon enters the delay generation module 10 and the time when the photon exits the delay generation module 10, i.e. the duration of the propagation of the photon in the delay generation module 10.

[0051] The active optical element 41 refers to an electrical element capable of modulating photons, and the active optical element 41 at least includes one of the following: an electro-optic modulator, an acousto-optic modulator.

[0052] In some embodiments, the delay generation module 10 generates different time delays for the n photons, and the difference between the time delays of adjacent photons is the same, i.e. between two adjacent photons, the time delay of the former photon relative to the latter photon differs by one delay factor τ. The size of the delay factor τ depends on the speed of the feedforward operation, and the delay factor τ is greater than or equal to the minimum time required to perform one feedforward operation. Two adjacent photons refer to the two photons with the closest time delays among the n photons, for example, in the case of n = 4, the time delay of photon A is about 1.51*10 -6 s, the time delay of photon B is about 4.56*10 -6 s, the time delay of photon C is about 3.02*10 -6 s, and the time delay of photon D is about 7.15*10 -6 s, photon A and photon C are adjacent photons, photon B and photon C are adjacent photons, and photon B and photon D are adjacent photons.

[0053] The optical fiber collimation module 20 is used to convert the light rays of the n photons into n collimated lights propagating in free space.

[0054] The aforementioned n-path collimated light refers to n parallel light rays that do not diverge. Free space refers to the space in which photons propagate freely. Free space can be an open space or a closed space, such as open spaces like air or outer space, or closed spaces like sealed cavities. In some embodiments, the fiber optic collimation module 20 includes at least: a pigtail and a lens. Optionally, for considerations such as precise alignment and reducing beam divergence, the focal length of the lens is 10mm.

[0055] The quasi-spatial mode generation module 30 is used to control the light rays of n photons propagating in free space to pass through the same active optical element 41 in sequence. The active optical element 41 is used to modulate the light signals of the n photons in sequence according to the time order in which the n photons arrive at the active optical element 41.

[0056] In some embodiments, the quasi-spatial pattern generation module 30 controls the spatial distance between the rays of n photons, enabling the rays of the n photons to pass sequentially through the same active optical element 41. Optionally, the quasi-spatial pattern generation module 30 can also adjust the propagation direction of the aforementioned n photons. In some embodiments, the rays of the photons are referred to as the spatial pattern or photon path of the photons.

[0057] In some embodiments, n=3, meaning there are 3 photons in a highly entangled cluster state. A quasi-spatial mode generation module 30 aligns the rays of the 3 photons in a non-overlapping manner; that is, the 3 photons generate 3 quasi-spatial modes through free-space element combination. The quasi-spatial mode generation module 30 generates 3 quasi-spatial modes from the 3 photons. For example... Figure 2 As shown, the propagation direction of the three photons is perpendicular to the screen and inwards. The cross-sections of the light rays 201, 202, and 203 corresponding to the three photons are arranged in a triangular pattern, that is, the lines connecting the cross-sections of the light rays (especially their center points) form a triangle. Each pair of light rays is parallel and aligned with each other in a non-overlapping manner. This quasi-spatial mode minimizes the difference in the propagation environment of the photons during propagation. Therefore, the quasi-spatial mode generation module 30 can change the spatial position of the light rays of n photons in free space, allowing the n photons to be modulated by the same active optical element. The spatial distance between the light rays is very small (the spatial distance between the light rays can be smaller than the diameter of the light ray), which allows these photons to pass through the same active optical element in a very small area. Because the crystal structure of the electro-optic crystal in the active optical element is not completely uniform, the crystal structure of the electro-optic crystal is basically the same in the same very small area, and the refractive power is similar. Therefore, multiple photons passing through the same active optical element in the same very small area result in the same modulation effect of the active optical element 41 on these photons, helping to avoid the introduction of new systematic errors.

[0058] The feedforward measurement module 40 is configured to measure the light signal of the first photon to obtain a measurement result of the first photon, which is used to feedforward compensate or feedforward correct the measurement result of the second photon to be measured. The first photon is one of the n photons, and the second photon is the next photon to be measured after the measurement of the first photon is started or completed.

[0059] The first photon can be any one of the n photons except the last photon reaching the feedforward measurement module 40. The feedforward measurement module 40 measures the light signal of the first photon to obtain a measurement result of the first photon. In some embodiments, the measurement result includes the polarization information of the first photon.

[0060] The second photon is the next photon to reach the feedforward measurement module 40 after the first photon among the n photons. Because the n photons are in a cluster state of mutual entanglement, the properties of the n photons affect each other, so the measurement result of the first photon has an impact on the measurement result of the second photon. According to the relevant principles of quantum physics, before the measurement result of the first photon is obtained, the first photon has multiple measurement results with different probabilities. Once the feedforward measurement module 40 measures the first photon, the measurement result of the first photon will undergo probability collapse, and the measurement result will change from uncertain to a certain result. Because the first photon and the second photon are in an entangled state, the measurement result of the first photon has an impact on the measurement result of the second photon. Based on the measurement result of the first photon, the feedforward measurement module 40 is adjusted to achieve compensation or correction.

[0061] In some embodiments, the feedforward measurement module 40 is adjusted based on the measurement result of the first photon through an element capable of fast switching. Alternatively, the feedforward measurement module 40 can be adjusted based on the measurement result of the first photon through a wave plate and an active optical element 41 in an open or closed state to feedforward compensate and feedforward correct the measurement result of the second photon to be measured. In some embodiments, the wave plate is a quarter wave plate. In some cases, the polarization state of the photon will be distorted after modulation by the active optical element 41, and the distorted polarization state of the photon can be converted to a sinusoidal polarization state through the quarter wave plate. After the second photon reaches the feedforward measurement module 40, the second photon is measured by the adjusted feedforward measurement module 40 to obtain a measurement result of the second photon.

[0062] In some embodiments, the speed of the feed-forward operation of the feed-forward measurement module 40 is controlled by the active optical element 41 and is preferably related to or further preferably determined by the working speed of the active optical element 41, and the maximum value of the speed of the feed-forward operation is further preferably the working speed of the active optical element 41. In some embodiments, the switching state of the active optical element 41 is controlled by a fast FPGA board.

[0063] In summary, on the one hand, the plurality of photons in the entangled state are given different time delays by the delay generation module; on the other hand, the light rays of the plurality of photons are in quasi-space modes that are very close in space but do not overlap with each other by the quasi-space mode generation module. The system only needs to use one active optical element to complete several fast feed-forward operations, measure the plurality of photons, and obtain a plurality of corresponding measurement results. The plurality of photons correspond to different time delays, so that the plurality of photons arrive at the feed-forward measurement module at different times, and the feed-forward measurement module uses the time interval between the adjacent photons to perform the feed-forward operation on the previous photon. Since the same feed-forward measurement module can measure the measurement results between the plurality of photons in the entangled state, the number of active optical elements required is reduced under the condition that the number of measured photons remains unchanged, which helps to reduce the design difficulty of the quantum device and the manufacturing cost of the quantum device.

[0064] In addition, since the plurality of photons arrive at the feed-forward measurement module one by one, the time interval between the photons is short, the feed-forward measurement module can perform the feed-forward operation at a high speed, and the speed and accuracy of quantum computing and the security in the case of a cryptographic protocol will not be reduced, and the universality of quantum computing will not be affected.

[0065] The optical device for quantum computing is described below through several embodiments.

[0066] In some embodiments, the difference between the time delay of the first photon and the time delay of the second photon is related to the time consumption of the feed-forward operation.

[0067] The feedforward operation is performed in the feedforward measurement module. In some embodiments, the time consumption of the feedforward operation refers to the time length consumed by the feedforward operation on a single photon. The time consumption of the feedforward operation is related to the speed of the feedforward operation, which at least includes the measurement process of the polarization of a certain single photon and the process of adjusting the feedforward measurement module based on the measurement result of the single photon. The time consumption of the feedforward operation is related to the processing time consumption of the active optical element. The time consumption of the feedforward operation at least includes the measurement time of the first photon by the feedforward measurement module and the modulation time of the photon by the active optical element. In order to further reduce the delay generated by the optical device for quantum computing in the process of obtaining the measurement result of n photons, the difference between the time delay of the first photon and the second photon is controlled by the delay generation module to be equal to or slightly greater than the measurement time of the first photon by the feedforward measurement module plus the modulation time of the photon by the active optical element, so that the optical device for quantum computing can continuously obtain the measurement result of the photon and perform the feedforward operation.

[0068] In some embodiments, the quasi-space mode generation module includes at least one lens module, which is used to generate converging effect on the light rays of the n photons and then emit in the form of n collimated lights, so that the spatial distance between the light rays of the n photons is reduced.

[0069] During the process of passing through the quasi-space mode generation module, a certain photon needs to pass through at least one lens module, and the spatial position of the light ray of the photon changes through the refraction effect of the lens module. It should be noted that before the n photons enter the quasi-space mode generation module, they need to pass through the delay generation module first, so the n photons arrive at the quasi-space mode generation module at different times. In some embodiments, when there is more than one lens module in the quasi-space mode generation module, the n photons pass through the lens modules in the order of time sequence in the propagation direction. The n photons pass through the refraction effect of at least one lens module in the quasi-space mode generation module, so that the spatial positions of the light rays of the n photons in the free space are closer, and the light rays still remain parallel. The spatial distance between the light rays corresponding to these photons is very small and does not completely coincide, which makes these photons pass through the same active optical element. Further, these photons can pass through the active optical element from the same small position area, so the modulation effect of the active optical element on the n photons is basically similar, and new calculation errors are not added in the process of measuring the measurement results corresponding to the n photons.

[0070] In some embodiments, each lens module includes a first lens and a second lens; the first lens is used to generate converging effect on the light rays of the n photons; and the second lens is used to convert the light rays of the n photons after passing through the first lens into the form of n collimated lights and emit.

[0071] In one example, in a certain lens module, the first lens is a convex lens and the second lens is a concave lens. As shown in the lens module 310 in Figure 3 , the distance between the center point of the first lens 311 and the center point of the second lens 312 is equal to the focal length of the first lens 311 minus the focal length of the second lens 312. Since the first lens 311 is a convex lens, when a certain photon passes through the first lens 311, the light rays of the photon are deflected towards the optical axis of the first lens 311 due to the converging effect of the convex lens. The photon then continues to propagate and passes through the second lens 312. Since the second lens 312 is a concave lens, the light rays of the photon are redirected due to the diverging effect of the concave lens. In some embodiments, the light rays of the photon are parallel to the optical axis of the first lens 311 (or the second lens 312) before and after passing through the lens module 310. After the photon passes through a certain lens module, the spatial distance between the light rays of the photon and the optical axis of the lenses in the lens module is reduced.

[0072] In another example, in a certain lens module, the first lens is a convex lens and the second lens is a concave lens, as shown in the lens module 320 in Figure 3 , the distance between the center point of the first lens 321 and the center point of the second lens 322 is equal to the focal length of the first lens 321 plus the focal length of the second lens 322. Optionally, the converging effect of the first lens 321 and the second lens 322 causes the spatial distance between the light rays of n photons to be closer to the optical axis of the first lens 321 (or the second lens 322), i.e., the spatial distance between the light rays of the n photons is closer.

[0073] As shown in the lens module 330 in Figure 3As shown, in some embodiments, three lens modules are arranged in the quasi-space mode generation module, which are lens module 310, lens module 320 and lens module 330 respectively. Among them, the first lens 311 in the lens module 310 is a convex lens, and the second lens 312 is a concave lens; the first lens 321 in the lens module 320 is a convex lens, and the second lens 322 is a convex lens; the first lens in the lens module 330 is a convex lens 331, and the second lens 332 is a concave lens. The three lens modules are placed in the propagation direction of the photons in turn. n photons enter the quasi-space mode generation module in chronological order. For any one of the n photons, the photon passes through the lens module 310, the lens module 320 and the lens module 330 in the propagation direction in turn. Through the converging effect of each lens module, the spatial distance (less than the diameter of the light line of the photon) between the light lines corresponding to the n photons respectively reaches a good effect of mutual approach and non-overlapping. Through multiple experiments, in the case of n = 3, the use of the above-mentioned three lens modules can make the light lines of the three photons be at a suitable spatial distance, and the light lines of the three photons are parallel to each other in the quasi-space mode. The three photons can smoothly pass through the same active optical element 41 through the converging effect of the above-mentioned three lens modules.

[0074] In the process of the feedforward measurement model sequentially performing feedforward operation on n photons, the quasi-space modes of the n photons are parallel to each other. Arranging at least one lens module in the quasi-space mode generation module is conducive to increasing the Rayleigh distance and improving the fault tolerance of the optical device for quantum computing.

[0075] In some embodiments, the quasi-space mode generation module further includes other adaptive optical devices, which can optionally include at least an adaptive mirror. As shown, Figure 4 As shown, the adaptive mirror 340 is used to change the propagation direction of the photons. In some embodiments, the adaptive mirror 340 is placed at an angle of 45° with the propagation direction of the photons, and through the refractive effect of the adaptive mirror 340, the propagation direction of the photons is rotated by 90°.

[0076] By changing the propagation direction of the photons through the adaptive mirror 340, the length of the quasi-space mode generation module can be effectively shortened, which helps to reduce the volume of the optical device for quantum computing. The adaptive mirror 340 can generate a large number of high-quality quasi-space modes.

[0077] In some embodiments, the delay generation module includes n optical fiber loops, and the n optical fiber loops correspond one-to-one to the n photons; the n optical fiber loops are used to generate different time delays for the n photons respectively.

[0078] In some embodiments, the n optical fiber loops have different fiber lengths.

[0079] The optical fiber loops corresponding to different photons have different lengths. The longer the optical fiber loop corresponding to a photon, the greater the time delay of the photon. The shorter the optical fiber loop corresponding to a photon, the smaller the time delay of the photon. For example, in the case of n = 3, the delay generation module includes three optical fiber loops. The lengths of the three optical fiber loops are 220 m, 440 m and 660 m, and the time delays t(660) > t(440) > t(220). Taking t(660) as an example, t(660) refers to the time delay of a photon propagating in an optical fiber loop with a length of 660 m. The time delay of the photon can be controlled by changing the length of the optical fiber loop. In some embodiments, the difference between the time delays of the first photon and the second photon is referred to as a delay factor τ. The minimum value of the delay factor τ is related to the working speed of the active optical element. In some embodiments, the delay factor τ is limited to 1 / (1 MHz). If a faster active optical element is used, the delay factor τ can be set smaller. In the current state of the art, the working speed of the active optical element allows to reach the order of tens of megahertz, which can further reduce the value of the delay factor τ. The specific range of the delay factor τ is not limited here. In some embodiments, the lengths of the optical fiber loops can be set according to the range of the delay factor τ. In some embodiments, the time delay of a photon is related to the optical fiber loop corresponding to the photon and the propagation speed of the photon. The optical fiber loop is used to control different photons to have different time delays, and to avoid changing other properties of the photons as much as possible, so that the photons reach the active optical element 1 at different times, and the active optical element can modulate the photons one by one.

[0080] In some embodiments, the optical fiber loop is isolated from the ambient temperature. Since temperature can affect the polarization state of the photon, isolating the optical fiber loop from the ambient temperature can avoid changes in the polarization state of the photon as much as possible during the propagation of the photon in the optical fiber loop, which helps to improve the accuracy of the measurement results of the polarization of the photon by the optical device for quantum computing.

[0081] In some embodiments, the optical fiber collimation module includes n optical fiber collimators, and the n optical fiber collimators and the n optical fiber loops correspond one-to-one. A target optical fiber collimator in the n optical fiber collimators is used to convert the light rays of a photon in a target optical fiber loop into collimated light propagating in free space. The target optical fiber loop is the optical fiber loop corresponding to the target optical fiber collimator in the n optical fiber loops.

[0082] For a photon, the photon propagates in the corresponding optical fiber loop, and after leaving the optical fiber loop, the photon is converted into collimated light by a target optical fiber collimator in the optical fiber collimation module, and the collimated light propagates in free space. The n optical fiber collimators can convert the light rays of n photons into n collimated lights, so that the light rays of any two photons are parallel to each other.

[0083] In some embodiments, the feedforward measurement module comprises: a first polarization beam splitter, an active optical element, a wave plate, a second polarization beam splitter, a detector, and a driver of the active optical element; the first polarization beam splitter is configured to obtain photons in a first polarization state; the active optical element is configured to change the polarization state of the photons in the first polarization state to obtain photons in a second polarization state; the wave plate and the second polarization beam splitter are configured to separate at least one single polarization state of photons from the photons in the second polarization state; the detector is configured to detect the light intensity of the at least one single polarization state of photons.

[0084] The first and second polarization beam splitters are used to filter out photons with specific polarization states. Taking the first polarization beam splitter as an example, which is used to filter out photons with horizontal polarization, the first polarization beam splitter only allows photons in the horizontal polarization state to continue propagating in the original direction of the photons, thereby achieving the effect of filtering out photons with specific polarization states. Alternatively, the first polarization beam splitter can change the propagation direction of photons with other polarization states, or absorb these photons. Alternatively, the first and second polarization beam splitters can filter out photons with the same polarization state, or filter out photons with different polarization states. The active optical element changes the polarization state of the photons passing through it, thereby achieving modulation of the photons. Since the n photons pass through the quasi-space mode generation module, the distance between the n collimated light rays formed by the light rays of the photons is very close, so that the photons undergo the same polarization rotation in the active optical element in the feedforward measurement module. In some embodiments, in the case of quantum encoding based on polarization information, the active optical element can be an electro-optic modulator. By adjusting the voltage on both sides of the electro-optic modulator, the refractive index of the electro-optic crystal in the electro-optic modulator can be changed, thereby affecting the vibration state of the photons passing through the electro-optic modulator. In some cases, when the electro-optic modulator is placed between two mutually perpendicular polarization beam splitters, adjusting the voltage of the electro-optic modulator can achieve light intensity modulation, at which point the electro-optic modulator is equivalent to a half-wave plate. In other embodiments, in the case of quantum encoding based on path information, the active optical element is an acousto-optic modulator. In some embodiments, the wave plate is a quarter-wave plate, and the wave plate is rotated at a step of 5°. In some embodiments, the feedforward measurement module includes two detectors, which are used to detect single photons with different polarization states. Alternatively, the detector includes a photodiode or other device capable of detecting single photons. The initial logical designation of the first detector is "0", and the initial logical designation of the second detector is "1". The logical designation is a number used to distinguish the first detector and the second detector. When the two detectors are in the initial logical designation, when the first detector detects a single photon, the measurement result of the feedforward measurement module is 0, and when the second detector detects a single photon, the measurement result of the feedforward measurement module is 1. After changing the logical designation of the two detectors (equivalent to exchanging the logical designation of the two detectors), the logical designation of the first detector becomes 1, and the logical designation of the second detector becomes 0. After exchanging the logical designation of the two detectors, when the first detector detects a single photon, the measurement result of the feedforward measurement module is 1, and when the second detector detects a single photon, the measurement result of the feedforward measurement module is 0. By exchanging the designation between the first detector and the second detector, a bit rotation gate function is realized on the quantum bit. The quantum rotation gate realized by the above method has a fast running speed and is easy to implement technically.

[0085] In some embodiments, after a certain photon enters the feedforward measurement module, the photon can sequentially pass through a first polarization beam splitter, an active optical element, a wave plate, a second polarization beam splitter, and finally reach a detector.

[0086] The optical device for quantum measurement provided in the present application can realize measurement of the rotation angle of the polarization of a single photon by only a quarter wave plate, an active optical element (such as a Pockels cell), and two detectors with interchangeable logical names. In an embodiment, by opening / closing the active optical element and exchanging the logical names of the first detector and the second detector, four polarization angles of the measured photon can be obtained. The four polarization angles of the measured photon are realized by changing the switch state of the active optical element and exchanging the first detector and the second detector, respectively, and the specific manner is as follows:

[0087] 1. The active optical element 41 is opened, and the initial logical names of the first detector and the second detector are used.

[0088] 2. The active optical element 41 is closed, and the initial logical names of the first detector and the second detector are used.

[0089] 3. The active optical element 41 is opened, and the initial logical names of the first detector and the second detector are exchanged.

[0090] 4. The active optical element 41 is closed, and the initial logical names of the first detector and the second detector are exchanged.

[0091] In some embodiments, by using a more complex active optical element controller, the number of measurable polarization angles can be increased, so that the present system can be closer to universal quantum computing.

[0092] Reference is made to Figure 4 which shows a schematic diagram of the optical device for quantum computing provided in an embodiment of the present application.

[0093] In some embodiments, the three photons in the highly entangled cluster state enter different length fiber loops in a delay generation module (not shown in the figure). The different length fiber loops cause the three photons to have different propagation times in the fiber loops, resulting in different time delays. After the photons exit the delay generation module, they enter the fiber collimation module 20, which includes at least three target fiber collimators 21. The three photons enter the corresponding target fiber collimators and the light rays of the three photons are converted into collimated light by the fiber collimators. The light rays of the three photons propagate in free space parallel to each other and enter the quasi- spatial mode generation module 30 in the order of time. Optionally, the spatial position of the light ray of a photon is changed by the refractive action of the plane mirror 22 in the light ray collimation module, so that the photon can enter the quasi-spatial mode generation module 30. The three photons sequentially pass through three lens modules 310, 320 and 330 in the propagation direction in the quasi-spatial mode generation module 30. The three photons form quasi-spatial modes with close spatial distances and parallel to each other by the converging action of the three lens modules 310, 320 and 330. The spatial distances between the corresponding quasi-spatial modes of the three photons are close and do not overlap. Optionally, the quasi-spatial mode generation module 30 further includes other adaptive optical elements such as an adaptive plane mirror 340. The adaptive plane mirror 340 is used to change the propagation direction of the photons. Since the three photons have different time delays in the delay generation module, the three photons arrive at the feedforward measurement module 40 at different times. The feedforward measurement module 40 performs feedforward operation on the first photon using the difference between the time delays of the first and second photons. In some embodiments, the first polarization beam splitter 42 in the feedforward measurement module 40 only allows photons in the horizontal polarization state to pass through. After a photon passes through the first polarization beam splitter 42, it continues to propagate in the original direction and reaches the active optical element 41. Optionally, the active optical element 41 is an electro-optic modulator. By changing the voltage between the two poles of the electro-optic modulator, the refractive index of the electro-optic crystal in the electro-optic modulator can be changed, thereby changing the polarization state of the photon. The modulated photon passes through the quarter-wave plate 43 with a step of 5° and the second polarization beam splitter 44 for filtering. The detector 45 can detect whether a photon reaches its surface. According to the detection result of the detector 45, the polarization state of the photon can be determined, and the measurement result corresponding to the photon can be generated.

[0094] The key elements in the active optical feedforward system of the multi-photon mode are described below.

[0095] 1. The optical fiber loops in the delay generation module use 780HP optical fibers with FC / PC connectors, which have the minimum loss at a given wavelength (800nm), and the delay factor τ is determined by the speed of the feedforward operation as 1 / (1MHz). In the above embodiment, the lengths of the three optical fiber loops are 220m, 440m and 660m respectively, and the type of optical fiber used in the optical device for quantum computing depends on the wavelength of the quantum bit to be measured, and the length of the optical fiber loop depends on the speed of the feedforward operation of the feedforward measurement module.

[0096] 2. The lenses in at least one lens module in the quasi-spatial mode generation module are all boron-coated ultraviolet silicon lens materials, which can reduce the loss generated during the passage of photons through the lenses. In the above embodiment, the parameters of the lenses in each lens module are shown in Table 1, which is the design table of the lens group in the quasi-spatial mode generation module.

[0097] Table 1 Design table of lens group in quasi-spatial mode generation module

[0098]

[0099] 3. Pockels cell: The system uses a double KTP crystal Pockels cell, which has the following specifications: crystal size: 6x6x10mm, diameter: 25.4mm, length: 42.2mm, CA diameter: 5.5mm, and transmittance >98% @790nm.

[0100] 4. Pockels cell driver: The Pockels cell driver used in the system has the following specifications: operating voltage 2.9kV, repetition rate 1MHz

[0101] 5. FPQA: The FPQA used in the system has the following specifications: 1GB 1800Mbps onboard DDR3, full fill 400-pin FMCH Pockels cell interface, 5 Pmod ports.

[0102] The feasibility of the present application is proved by the experimental data of three photons in a highly entangled and clustered state in the above optical device for quantum computing.

[0103] 1. Characterization of quasi-spatial modes and beam diameters.

[0104] The data of the beam diameters of the photons and the corresponding quasi-spatial modes of the three photons are measured by a laser and a WinCamD (far infrared spot analyzer) produced by DataRay, and the diameters d1, d2 and d3 of the three beams and the distances D12, D23 and D13 between the three beams (the serial numbers corresponding to the three beams and the positional relationship between the three beams are shown inFigure 5 The relevant data for the Pockels cell 500 are as follows.

[0105] The diameter of the light rays of the photons:

[0106] d1 = (219 ± 3) pm

[0107] d2 = (237 ± 3) pm

[0108] d3 = (261 ± 3) pm

[0109] The distance between the light rays:

[0110] D12 = (749.52 ± 0.71) pm

[0111] D13 = (713.81 ± 0.71) pm

[0112] D23 = (1047.53 ± 0.71) pm

[0113] 2. Characterization of the Pockels cell on the change of the angle of the light rays of the photons.

[0114] To align the angle transformation imposed by the Pockels cell on the light rays of the photons, we refer to Figure 5 , we again use a laser and two polarizing beam splitters and a half-wave plate in the feed-forward measurement module. The first polarizing beam splitter 510 before the Pockels cell 520 is used to filter the photons (filtering out photons with a specific polarization state), ensuring that only the initial horizontally polarized photons are part of the characterization. Subsequently, these photons pass through the Pockels cell 520 and the half-wave plate 530, which is rotated in 5° steps. The second polarizing beam splitter 540 filters the photons again (polarization) before the photodiode 550. For each position to which the half-wave plate 530 is rotated, the photodiode 550 measures the intensity of the photons when the Pockels cell is on and off, and the angle set by the Pockels cell 520 is determined by the phase between the two intensity functions. The Pockels cell 520 (KTP (TiOPO4, Potassium Titanyl Phosphate) crystal placed at an angle of 0 = 22.5°) acts as a half-wave plate and transforms the photons from horizontal polarization to diagonal polarization in three different beam paths.

[0115] 0i = (22.569 ± 0.125) °

[0116] 0 2 = (22.581 ± 0.125) °

[0117] 0 3 = (22.597 ± 0.125) °

[0118] The different angles are caused by the possible step size of the PCB motor that controls the half-wave plate.

[0119] 3. Characterization of the 3 different beams (3 photon pairs) angles through the Pockels cell.

[0120] Please refer to Figure 6 which shows the intensity function measured by the photodiode as a function of the Pockels cell rotation angle.

[0121] For a more clear understanding, Figure 6 The intensity measurement fitting function with the Pockels cell in the off state is represented by a dashed line in FIG. 6, the Pockels cell deflects all the beams by the same amount, the Pockels cell behaves as a half-wave plate with an angle of θ = (22.582 ± 0.125)°, the error is due to the possible step of the PCB motor used for the control of the half-wave plate. In order to distinguish the 6 wave functions in FIG. 6, the amplitude of beam 1 is multiplied by 0.7, the amplitude of beam 2 is multiplied by 1.3, and the amplitude of beam 3 is unchanged. Figure 6

[0122] An example embodiment of the present application provides a quantum computing system, which comprises the optical device for quantum computing described in the above embodiments.

[0123] In some embodiments, the system further comprises an entangled photon generation module and a measurement error correction module.

[0124] The entangled photon generation module is configured to generate a photon cluster with n photons in a highly entangled state. In some embodiments, the entangled photon generation module at least comprises an ultraviolet generator and a photon generation crystal. In some embodiments, the ultraviolet generator irradiates the surface of the photon generation crystal to generate four photon clusters in a highly entangled state.

[0125] The measurement error correction module is configured to correct errors in measurement results of the polarization of photons measured by the optical device for quantum computing. In some embodiments, the polarization information of a photon includes three components (quantum states) in a spatial position. In some embodiments, in the case of n = 3, the polarization information of a photon is stored in a certain component of the polarization information of the other two photons. By performing quantum computation on the polarization information of the other two photons, it can be determined whether the measurement result of the photon is incorrect, thereby realizing the error correction process.

[0126] The following is a method embodiment of the present application, which can be implemented by the device provided by the present application. For details not disclosed in the method embodiment of the present application, please refer to the device embodiment of the present application.

[0127] ​An example embodiment of the present application provides an active optical feedforward method of multi-photon mode, which is applied in an optical device for quantum computing, the device comprising: a delay generation module, a fiber collimation module, a quasi-space mode generation module, and a feedforward measurement module, the feedforward measurement module comprising an active optical element for modulating and processing optical signals; the method can comprise the following steps:

[0128] 1. The delay generation module generates different time delays for n photons respectively, so that the n photons arrive at the active optical element at different times, n being an integer greater than 1.

[0129] 2. The fiber collimation module converts the light of the n photons into n collimated lights propagating in free space.

[0130] 3. The quasi-space mode generation module controls the light of the n photons propagating in free space to pass through the same active optical element in turn, and the active optical element is used to modulate and process the optical signals of the n photons in turn according to the time sequence of the n photons arriving at the active optical element.

[0131] 4. The feedforward measurement module measures the modulated and processed optical signal of the first photon to obtain a measurement result of the first photon, and the measurement result of the first photon is used to feedforward compensate or feedforward correct the measurement result of the second photon to be measured; wherein the first photon is one of the n photons, and the second photon is the next photon to be measured after the first photon.

[0132] In some embodiments, the difference between the time delay of the first photon and the time delay of the second photon is related to the time consumption of the feedforward operation.

[0133] In some embodiments, the quasi-space mode generation module comprises at least one lens module, and the lens module reduces the spatial distance between the light of the n photons.

[0134] In some embodiments, the lens module is used to produce a converging effect on the light of the n photons before emitting in the form of n collimated lights.

[0135] In some embodiments, each lens module comprises a first lens and a second lens; the first lens is used to produce a converging effect on the light of the n photons; and the second lens is used to convert the light of the n photons after passing through the first lens into the form of n collimated lights.

[0136] In some embodiments, the first lens is a convex lens, and the second lens is a concave lens or a convex lens.

[0137] In some embodiments, the delay generation module includes n fiber loops, the n fiber loops and the n photons are one-to-one corresponding; the n fiber loops are used to generate different time delays for the n photons respectively.

[0138] In some embodiments, the n fiber loops have different fiber lengths.

[0139] In some embodiments, the fiber collimation module includes n fiber collimators, the n fiber collimators and the n fiber loops are one-to-one corresponding; a target fiber collimator in the n fiber collimators is used to convert the light rays of the photons in a target fiber loop into collimated light propagating in free space; wherein the target fiber loop is the fiber loop corresponding to the target fiber collimator in the n fiber loops.

[0140] In some embodiments, the delay generation module is isolated from the ambient temperature so as to maintain the polarization state of each photon during the delay operation.

[0141] In some embodiments, the feedforward measurement module includes: a first polarization beam splitter, an active optical element, a wave plate, a second polarization beam splitter, a detector, and a driver of the active optical element; the first polarization beam splitter is used to obtain photons with a first polarization state; the active optical element is used to change the polarization state of the photons with the first polarization state to obtain photons with a second polarization state; the wave plate and the second polarization beam splitter are used to separate at least one single polarization state photon from the photons with the second polarization state; the detector is used to detect the light intensity of the at least one single polarization state photon.

[0142] In some embodiments, the active optical element includes an electro-optic modulator.

[0143] The plurality of photons in the cluster state are made to have different time delays by the delay generation module; and the plurality of photons are made to be in quasi-space modes with very close but not overlapping spatial distances by the quasi-space mode generation module, so that the system only needs to use one active optical element to complete several fast feedforward operations, to realize measurement of the plurality of photons respectively and to obtain measurement results corresponding to the plurality of photons respectively. The different time delays of the plurality of photons make the time instants at which the plurality of photons arrive at the feedforward measurement module different, and the feedforward measurement module uses the time interval between the adjacent photons to measure the photons to obtain measurement results, and adjusts the system based on the measurement results to realize feedforward compensation or correction. Since the same feedforward measurement module can measure the measurement results between the plurality of photons in the entangled state, the number of active optical elements used in the calculation process is reduced under the condition that the number of measured photons remains unchanged, which helps to reduce the design difficulty of the quantum device and reduce the cost of the quantum device.

[0144] The embodiment of the present application further provides a computer readable storage medium, which stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, the at least one program, the code set or the instruction set are loaded and executed by a processor to implement the multi-photon mode active optical feedforward method provided by the above method embodiments.

[0145] Optionally, the computer readable storage medium can include a ROM (Read-Only Memory), a RAM (Random-Access Memory), a SSD (Solid State Drives) or an optical disc, etc. The random access memory can include a ReRAM (Resistance Random Access Memory) and a DRAM (Dynamic Random Access Memory).

[0146] The embodiment of the present application further provides a computer program product, which includes at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, the at least one program, the code set or the instruction set are loaded and executed by a processor to implement the multi-photon mode active optical feedforward method provided by the above method embodiments.

[0147] It should be understood that the "multiple" mentioned herein refers to two or more. In addition, the step numbers described herein only exemplarily show a possible execution sequence between steps, and in some other embodiments, the above steps can also be executed in a sequence different from the number, such as two different numbered steps are executed simultaneously, or two different numbered steps are executed in a sequence opposite to the illustration, and the embodiment of the present application does not limit this.

[0148] The above only describes exemplary embodiments of the present application, and does not limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An optical device for quantum computing, characterized by, The device comprises a delay generation module, a fiber collimation module, a quasi-space mode generation module, and a feedforward measurement module, wherein the feedforward measurement module comprises an active optical element for modulating an optical signal; The delay generation module is configured to generate different time delays for n photons respectively, so that the n photons arrive at the active optical element at different time points, and n is an integer greater than 1; The fiber collimation module is configured to convert the light rays of the n photons into n collimated lights propagating in free space; The quasi-space mode generation module is configured to control the light rays of the n photons propagating in free space to sequentially pass through the same active optical element, and the active optical element is configured to sequentially modulate the optical signals of the n photons according to the time sequence of the n photons arriving at the active optical element; The feedforward measurement module is configured to perform polarization measurement on the modulated optical signal of a first photon to obtain a measurement result of the first photon, and the measurement result of the first photon is used for feedforward compensation or feedforward error correction on a measurement result of a second photon to be measured, wherein the first photon is one of the n photons, and the second photon is the next photon to be measured after the first photon.

2. The apparatus of claim 1, wherein, The difference between the time delay of the first photon and the time delay of the second photon is related to the time consumption of the feedforward operation.

3. The apparatus of claim 1, wherein, The quasi-space mode generation module comprises at least one lens module, and the lens module is configured to reduce the spatial distance between the light rays of the n photons.

4. The apparatus of claim 3, wherein, The lens module is configured to generate a converging effect on the light rays of the n photons before emitting them in the form of the n collimated lights.

5. The apparatus of claim 3, wherein, Each lens module comprises a first lens and a second lens; The first lens is configured to generate a converging effect on the light rays of the n photons; The second lens is configured to convert the light rays of the n photons after passing through the first lens into the form of the n collimated lights.

6. The apparatus of claim 5, wherein, The first lens is a convex lens, and the second lens is a concave lens or a convex lens.

7. The apparatus of claim 1, wherein, The delay generation module comprises n fiber loops, and the n fiber loops correspond to the n photons one by one; The n fiber loops are configured to generate different time delays for the n photons respectively.

8. The apparatus of claim 7, wherein, The n fiber loops have different fiber lengths.

9. The apparatus of claim 7, wherein, The fiber collimation module comprises n fiber collimators, and the n fiber collimators correspond to the n fiber loops one by one; A target fiber collimator in the n fiber collimators is configured to convert the light rays of a photon in a target fiber loop into a collimated light propagating in free space; The target fiber loop is a fiber loop in the n fiber loops corresponding to the target fiber collimator.

10. The apparatus of claim 1, wherein, The delay generation module is isolated from the ambient temperature, so as to maintain the polarization state of each photon during the delay operation.

11. The apparatus of claim 1, wherein, The feedforward measurement module comprises a first polarization beam splitter, the active optical element, a wave plate, a second polarization beam splitter, a detector, and a driver of the active optical element; The first polarization beam splitter is configured to obtain a photon with a first polarization state; The active optical element is configured to change the polarization state of the photons of the first polarization state to obtain photons of a second polarization state; The wave plate and the second polarization beam splitter are configured to separate at least one single polarization state of photons from the photons of the second polarization state; The detector is configured to detect the light intensity of the at least one single polarization state of photons.

12. The apparatus of claim 1, wherein, The active optical element comprises an electro-optical modulator.

13. A quantum computing system, comprising: The system comprises the optical device for quantum computing according to any one of claims 1 to 12.

14. An active optical feedforward method in a multi-photon mode, characterized by, The method is applied in an optical device for quantum computing, the device comprising: a delay generation module, a fiber collimation module, a quasi-space mode generation module, and a feedforward measurement module, wherein the feedforward measurement module comprises an active optical element configured to modulate the optical signal. The method comprises: The delay generation module is configured to generate different time delays for n photons respectively, so that the n photons arrive at the active optical element at different time points, n being an integer greater than 1; The fiber collimation module is configured to convert the light rays of the n photons into n collimated lights propagating in free space; The quasi-space mode generation module is configured to control the light rays of the n photons propagating in free space to pass through the same active optical element in sequence, and the active optical element is configured to modulate the optical signals of the n photons in sequence according to the time sequence of the n photons arriving at the active optical element; The feedforward measurement module is configured to perform polarization measurement on the modulated optical signal of a first photon to obtain a measurement result of the first photon, and the measurement result of the first photon is used for feedforward compensation or feedforward error correction of a measurement result of a second photon to be measured; wherein the first photon is one of the n photons, and the second photon is the next photon to be measured after the first photon.

15. A computer-readable storage medium, characterized in that, The computer readable storage medium stores at least one instruction, at least one program, a code set or an instruction set, which are loaded and executed by the processor to implement the method of claim 14.

16. A computer program product, characterised in that, The computer program product comprises at least one instruction, at least one program, a code set or an instruction set, which are loaded and executed by the processor to implement the method of claim 14.

Images