Measurement method and system for quantum weak signal detection

Abstract

The invention discloses a measurement method and system for quantum weak signal detection, and relates to the quantum precision measurement and quantum topology technology, and the method comprises the steps: constructing a dual-mode non-reciprocal SSH lattice model based on a waveguide; measuring an extremely weak optical signal at the position of a cell m, coupling the cell m with an optical fiber, driving laser to enter and couple to a waveguide SSH lattice through the optical fiber, and measuring a reflected signal at a port of the optical fiber; adjusting the specifications of the waveguide units to optimize coupling strength parameters among the waveguide units so as to obtain detection signals with increased single photon signal-to-noise ratio indexes; and at a specified moment, starting the driving laser, and adjusting the phase of the driving laser and the homodyne detection phase to measure the signal-to-noise ratio of the single photon. The invention provides a system scheme for improving the detection sensitivity of local weak signals in an exponential level.

Description

Technical Field

[0001] The present application relates to the fields of quantum precision measurement and quantum topology technology, and in particular to a measurement method and system for quantum weak signal detection. Background Art

[0002] Realizing high-precision sensing and detection is an important research field in modern science and technology. By introducing an external point (EP) in the detection sensor device, the detection accuracy can be significantly improved. EP appears in non-Hermitian systems and brings about the degeneracy of intrinsic energy and eigenstates. When the parameters of the non-Hermitian system are close to EP, the intrinsic energy shows divergent sensitivity to infinitesimal changes in the parameters. However, in the Hermitian system, the intrinsic energy shows only limited sensitivity to small changes in the parameters. At present, a large number of experimental results have verified this phenomenon. However, this improvement in sensitivity is only an increase in the sensor transduction coefficient, and does not improve the accuracy of sensor detection - signal-to-noise ratio (SNR). Many research results show that the increase in the transduction coefficient based on EP sensors will be masked by the reduction in signal-to-noise ratio, thereby limiting the performance of sensor detection. Recent studies have shown that introducing non-reciprocity into dual-mode non-Hermitian systems can greatly improve the accuracy and signal-to-noise ratio of sensor detection. The performance of non-reciprocal sensing detection exceeds the limit of reciprocal sensing detection.

[0003] Non-Hermitian lattices have many novel phenomena, such as topological phases of non-Hermitian lattices and skin effects with modified momentum in the generalized Brillouin zone (GBZ). Recent studies have shown that non-Hermitian lattices can be used to improve the sensitivity of sensor detection. The transduction coefficient of the detection device increases exponentially with the lattice scale. When detecting global weak signals in the parity-time symmetric Su-Schrieffer-Heeger (SSH) lattice, the quantum Fisher information (QFI) of the device also increases exponentially with the lattice size, which also shows that there is a correlation between the signal-to-noise ratio and the QFI. Some studies have suggested that the improvement in the signal-to-noise ratio may be due to the exponential growth of the number of photons, while the sensitivity of sensor detection is still poor. Summary of the invention

[0004] The embodiments of the present application provide a measurement method and system for quantum weak signal detection, and provide a system solution for exponentially improving the sensitivity of local weak signal detection.

[0005] The present application provides a method for measuring quantum weak signal detection, including:

[0006] A dual-mode, non-reciprocal SSH lattice model based on waveguide construction;

[0007] Measuring an extremely weak optical signal at the position of unit cell m, coupling the unit cell m with an optical fiber, driving a laser to be incident through the optical fiber and coupled to the waveguide SSH lattice, and measuring a reflected signal at a port of the optical fiber;

[0008] Adjusting the specifications of the waveguide units to optimize the coupling strength parameters between the waveguide units to obtain a detection signal with an exponentially increased single-photon signal-to-noise ratio;

[0009] At a specified time, the driving laser is turned on, and the driving laser phase and homodyne detection phase are adjusted to measure the single-photon signal-to-noise ratio.

[0010] An embodiment of the present application provides a measurement system for quantum weak signal detection, including a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the steps of the measurement method for quantum weak signal detection as described above are implemented.

[0011] The embodiment of the present application uses a waveguide device to construct a non-Hermitian, non-reciprocal SSH lattice model. By configuring the parameters of the waveguide, drive field, and homodyne detection under the topological phase defined by the generalized Brillouin zone, a system solution is provided for exponentially improving the detection sensitivity of local weak signals.

[0012] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0014] Figure 1 The basic process diagram of the measurement method for quantum weak signal detection in the embodiment of the present application is shown;

[0015] Figure 2 This is a schematic diagram of the system structure of the measurement method for quantum weak signal detection in the embodiment of the present application;

[0016] Figure 3 This is an example of the results in the application example of the measurement method for quantum weak signal detection in this application. DETAILED DESCRIPTION

[0017] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0018] The present application embodiment provides a measurement method for detecting a quantum weak signal, such as Figure 1 As shown, the following steps are included:

[0019] In step S101, a dual-mode, non-reciprocal SSH lattice model is constructed based on a waveguide. In some embodiments, the method specifically includes:

[0020] Two different types of waveguide units are set to correspond to the A and B sub-grid points in the SSH model respectively; by designing the waveguide units with different geometric sizes, materials or structures, different coupling strengths between the waveguide units can be achieved. , that is, non-reciprocity.

[0021] like Figure 2 As shown, the waveguide units are arranged according to the one-dimensional complex lattice structure of the SSH model, so that each unit cell (corresponding to the SSH lattice) contains two waveguide units of different types, which are arranged in an alternating order.

[0022] Connect adjacent cells to achieve coupling between cells, such as using a coupler or waveguide connector to connect adjacent cells to achieve coupling between cells, that is, connect adjacent cells to achieve coupling between cells In a specific example, a dual-mode, non-reciprocal SSH lattice model can be realized through a waveguide platform, and the effect of adjusting the lattice model parameters can be achieved by designing different geometric dimensions, materials or structures.

[0023] In step S102, the extremely weak optical signal at the unit cell m is measured, the unit cell m is coupled to an optical fiber, a laser is driven to be incident through the optical fiber and coupled to the waveguide SSH lattice, and a reflected signal is measured at a port of the optical fiber.

[0024] In step S103, the specifications of the waveguide units are adjusted to optimize the coupling strength parameters between the waveguide units to obtain a detection signal with an exponentially increased single-photon signal-to-noise ratio.

[0025] In step S104, at a specified time, the driving laser is turned on, and the driving laser phase and the homodyne detection phase are adjusted to measure the single-photon signal-to-noise ratio.

[0026] The embodiment of the present application uses a waveguide device to construct a non-Hermitian, non-reciprocal SSH lattice model. By configuring the parameters of the waveguide, drive field, and homodyne detection under the topological phase defined by the generalized Brillouin zone, a system solution is provided for exponentially improving the detection sensitivity of local weak signals.

[0027] In some embodiments, the waveguide-based dual-mode, non-reciprocal SSH lattice model further comprises:

[0028] Based on the operation of waveguide, the corresponding dual-mode, non-reciprocal SSH lattice model is established to satisfy:

[0029]

[0030] in, The coupling strength from sub-grid point A to B is, The coupling strength from sub-grid point B to A is, It represents the coupling strength between adjacent positions, that is, adjacent cells, n represents the cell position, A represents sub-grid point A, and B represents sub-grid point B.

[0031] In some embodiments, measuring the extremely weak optical signal at the unit cell m, coupling the unit cell m with an optical fiber, driving the laser to be incident through the optical fiber and coupled to the waveguide SSH lattice, and measuring the reflected signal at the port of the optical fiber comprises:

[0032] The coupling of the waveguide SSH lattice to the light field is described as:

[0033]

[0034] in, The Hamiltonian representing the coupling between the waveguide SSH lattice and the optical field, represents an imaginary number, represents the photon annihilation operator of sub-grid point A at unit cell m, represents the photon annihilation operator of sub-grid point B at unit cell m, represents the photon generation operator of sub-grid point A at unit cell m, represents the photon generation operator of sub-grid point B at unit cell m, represents the difference in coupling strength between sub-lattice point A to B and sub-lattice point B to A, Indicates the cell location, Represents the total number of cells, represents the average coupling strength between sub-grid point A to B and sub-grid point B to A, represents the coupling strength between neighboring cells.

[0035] The coupling of the extremely weak light signal at the cell m position satisfies:

[0036]

[0037] in Represents a very small quantity that describes an extremely weak light signal.

[0038] In some embodiments, measuring the extremely weak optical signal at the unit cell m, coupling the unit cell m to an optical fiber, driving the laser to be incident through the optical fiber and coupled to the waveguide SSH lattice, and measuring the reflected signal at the port of the optical fiber further comprises:

[0039] According to the standard incidence-exit theory, the exit field of the homodyne measurement at the cell position m satisfies:

[0040]

[0041] in, is the coupling strength between the optical fiber and unit cell m, is the incident driving laser, is the phase of the incident driving laser, Indicates noise.

[0042] At time τ, the outgoing field is , the homodyne measurement field operator is expressed as:

[0043]

[0044] in, represents the measured phase, represents the annihilation operator of the outgoing field at time τ, represents the operator for generating the outgoing field at time τ;

[0045] The detected signal power satisfies:

[0046]

[0047] in, The average field intensity measured for superimposed very weak optical signals, The average field intensity measured when there is no extremely weak light signal and only strong driving field incident;

[0048] The noise power is:

[0049]

[0050] The signal-to-noise ratio is defined as , the single-photon signal-to-noise ratio is , where the total number of photons ;

[0051] Substituting into the above expression, under the zero-order approximation of ε, the detected signal power is:

[0052]

[0053] The total number of photons is:

[0054]

[0055] In some embodiments, adjusting the specifications of the waveguide units to optimize the coupling strength parameters between the waveguide units to obtain a detection signal with an exponentially increased single-photon signal-to-noise ratio includes:

[0056] Adjust the geometrical dimensions, materials, structures and / or connection parameters of the waveguide units to optimize the coupling strength parameters between the waveguide units to meet one of the following conditions:

[0057] ,and ;

[0058] but ;

[0059] To obtain a detection signal with an exponentially increased single-photon signal-to-noise ratio.

[0060] According to the signal optical power in S102 Formula (8), when and hour, As the lattice size N increases, it always increases exponentially. At this time, the system is in the topological phase region defined by the generalized Brillouin zone. but hour, It is also possible to select the measurement phase appropriately. and the driving laser phase , it always increases exponentially with the increase of lattice size N, and the system is still in the topological phase region. In other cases except the above two, it decreases exponentially, and the system is also not in the topological phase region. Therefore, according to the above scheme, by optimizing the coupling strength parameters between waveguide units, an exponentially increasing detection sensitivity can be obtained.

[0061] Further, in S104, for example, at time t=0, the driving laser is turned on, the driving laser phase and the homodyne detection phase are adjusted, and the single photon signal-to-noise ratio is measured.

[0062] The present application also proposes an implementation example of a measurement method for detecting quantum weak signals:

[0063] use The waveguide SSH lattice was measured The extremely weak optical signal at the waveguide unit cell location . The fiber coupling strength is measured as , measuring time .

[0064] Optimization parameters: , .

[0065] Signal-to-Noise Ratio and single photon signal-to-noise ratio The results are as follows Figure 3 As shown, Figure 3 (a) and Figure 3 (b) shows the signal-to-noise ratio and single photon signal-to-noise ratio As the driving laser phase and measure phase , both showed significant improvements, especially the single-photon signal-to-noise ratio was improved to the order of 10^15. Figure 3 (c) shows , When , the single-photon signal-to-noise ratio increases exponentially with the increase of the lattice size N. When N=60, Increased to the order of 10^43.

[0066] The embodiment of the present application proposes a high-sensitivity detection method based on a waveguide system to achieve an exponential improvement in detection sensitivity for extremely weak local signals. The method of the present application uses a waveguide system and a detection method that are both feasible and operable.

[0067] This application optimizes the phase of the incident driving field, the coupling strength between sub-lattice points of the waveguide lattice, the homodyne detection phase and other parameters in an integrated manner, so that the waveguide system enters the topological phase region defined by the generalized Brillouin zone, and the measured single-photon signal-to-noise ratio shows an exponential improvement, and further improves with the increase of the lattice size. The method of this application uses the single-photon signal-to-noise ratio to measure sensitivity, avoiding the interference and influence of the strong incident driving light field when measuring with the signal-to-noise ratio, thereby obtaining a real improvement in detection sensitivity for local extremely weak signals.

[0068] The embodiment of the present application also proposes a measurement system for quantum weak signal detection, including a processor and a memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the steps of the measurement method for quantum weak signal detection as described above are implemented.

[0069] It should be noted that in the various embodiments of the present application, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0070] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0071] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0072] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A measurement method for detecting quantum weak signals, characterized in that: include: A dual-mode, non-reciprocal SSH lattice model based on waveguide construction; Measuring an extremely weak optical signal at the position of unit cell m, coupling the unit cell m with an optical fiber, driving a laser to be incident through the optical fiber and coupled to the waveguide SSH lattice, and measuring a reflected signal at a port of the optical fiber; Adjusting the specifications of the waveguide units to optimize the coupling strength parameters between the waveguide units to obtain a detection signal with an exponentially increased single-photon signal-to-noise ratio; At a specified time, the driving laser is turned on, and the driving laser phase and homodyne detection phase are adjusted to measure the single-photon signal-to-noise ratio.

2. The measurement method for detecting quantum weak signals according to claim 1, characterized in that: The dual-mode, non-reciprocal SSH lattice model based on waveguide construction includes: Two different types of waveguide units are set to correspond to the A and B sub-grid points in the SSH model respectively; The waveguide units are arranged according to the one-dimensional compound lattice structure of the SSH model, so that each unit cell contains two waveguide units of different types, which are arranged in an alternating order; Connect adjacent cells to achieve coupling between cells.

3. The measurement method for detecting quantum weak signals according to claim 1, characterized in that: The dual-mode, non-reciprocal SSH lattice model based on waveguide construction also includes: Based on the operation of waveguide, the corresponding dual-mode, non-reciprocal SSH lattice model is established to satisfy: in, represents the coupling strength from sub-grid point A to B, represents the coupling strength from sub-grid point B to A, represents the coupling strength between adjacent cells, n represents the cell position, A represents sub-grid point A, and B represents sub-grid point B.

4. The measurement method for detecting quantum weak signals as claimed in claim 3, characterized in that: Measuring an extremely weak optical signal at a unit cell m, coupling the unit cell m with an optical fiber, driving a laser to be incident through the optical fiber and coupled to a waveguide SSH lattice, and measuring a reflected signal at a port of the optical fiber comprises: The coupling of the waveguide SSH lattice to the light field is described as: in, The Hamiltonian representing the coupling between the waveguide SSH lattice and the optical field, represents an imaginary number, represents the photon annihilation operator of sub-grid point A at unit cell m, represents the photon annihilation operator of sub-grid point B at unit cell m, represents the photon generation operator of sub-grid point A at unit cell m, represents the photon generation operator of sub-grid point B at unit cell m, represents the difference in coupling strength between sub-lattice point A to B and sub-lattice point B to A, Indicates the cell location, Represents the total number of cells, represents the average coupling strength between sub-grid point A to B and sub-grid point B to A, represents the coupling strength between adjacent cells; The coupling of the extremely weak light signal at the cell m position satisfies: in Represents a very small quantity that describes an extremely weak light signal.

5. The measurement method for detecting quantum weak signals according to claim 4, characterized in that: Measuring an extremely weak optical signal at the position of unit cell m, coupling the unit cell m with an optical fiber, driving a laser to be incident through the optical fiber and coupled to a waveguide SSH lattice, and measuring a reflected signal at a port of the optical fiber further comprises: According to the standard incidence-exit theory, the exit field of the homodyne measurement at the cell position m satisfies: in, is the coupling strength between the optical fiber and unit cell m, is the incident driving laser, is the phase of the incident driving laser, Indicates noise; At time τ, the outgoing field is , the homodyne measurement field operator is expressed as: in, represents the measured phase, represents the annihilation operator of the outgoing field at time τ, represents the operator for generating the outgoing field at time τ; The detected signal power satisfies: in, The average field intensity measured for superimposed very weak optical signals, The average field intensity measured when there is no extremely weak light signal and only strong driving field incident; The noise power is: The signal-to-noise ratio is defined as , the single photon signal-to-noise ratio is , where the total number of photons ; Then, under the zero-order approximation of ε, the detected signal power is: The total number of photons is:

6. The measurement method for detecting quantum weak signals according to claim 5, characterized in that: Adjusting the specifications of the waveguide units to optimize the coupling strength parameters between the waveguide units to obtain a detection signal with an exponentially increased single-photon signal-to-noise ratio includes: Adjust the geometrical dimensions, materials, structures and / or connection parameters of the waveguide units to optimize the coupling strength parameters between the waveguide units to meet one of the following conditions: ,and ; but ; To obtain a detection signal with an exponentially increased single-photon signal-to-noise ratio.

7. A measurement system for detecting quantum weak signals, characterized in that: The method comprises a processor and a memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the steps of the measurement method for detecting quantum weak signals as described in any one of claims 1 to 6 are implemented.

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