Wavelength measurement and feedback method of entangled two-photon source based on wavelength-time mapping

Abstract

The present invention discloses a wavelength measurement and feedback method for an entangled two-photon source based on wavelength-time mapping, which is applied to a wavelength measurement and stabilization device for an entangled two-photon source based on wavelength-time mapping, wherein the measurement device comprises: an entangled two-photon source, a first single-photon detector, a second single-photon detector, a dense wavelength division multiplexer, a dispersion element and a time-correlated single-photon counter; the wavelength measurement and feedback method for an entangled two-photon source based on wavelength-time mapping of the present invention does not require the use of a filter, does not require the acquisition of wavelength information of entangled two photons by wavelength scanning, greatly reduces the measurement time, and meets the demand for real-time wavelength measurement; at the same time, the method is compatible with a quantum optical system, and has the advantages of low cost and easy implementation.

Description

Technical Field

[0001] The present invention belongs to the field of quantum entangled light source characteristic analysis, and specifically relates to an entangled two-photon source wavelength measurement and feedback method based on wavelength-time mapping. Background Art

[0002] Quantum entangled two-photon sources are important resources in quantum optical systems and play an indispensable role in the development of quantum information technology. Among them, energy-time entangled two-photons have attracted more and more attention due to their unique non-local strong time correlation characteristics. After long-distance optical fiber transmission, they can achieve the robustness of two-photon sources to link loss and decoherence effects through the non-local dispersion elimination characteristics. Energy-time entangled two-photon sources in the optical communication band have been applied to a variety of optical fiber-based quantum communications and precision metrology experiments.

[0003] The spontaneous parametric down-conversion process is the most common method for generating entangled two-photon sources. Since nonlinear waveguides have higher nonlinear conversion efficiency than nonlinear crystals and can be well matched with standard single-mode fiber modes to facilitate photon collection, the use of continuous laser pumping of periodically polarized nonlinear waveguides, such as periodically polarized lithium niobate (PPLN) waveguides, to generate energy-time entangled two-photon source pairs has been widely developed and studied. This method uses a temperature controller to adjust the quasi-phase matching. The device is simple and easy to operate, so that the wavelength of the entangled two-photon source can be adjusted. However, due to the process defects in the processing of nonlinear waveguides, different waveguides have different heat treatment residual stresses, which is manifested as long-term irregular drift of the phase matching wavelength of different waveguides even under the above temperature control conditions, which has an adverse effect on the performance of many quantum experimental systems based on energy-time entangled two-photon sources. For example, in quantum time synchronization systems, the stability of the photon wavelength of the entangled source is crucial to the synchronization accuracy. Taking a bidirectional quantum time synchronization system connected by a 100km single-mode optical fiber as an example, if the central wavelengths of the signal photons of the two entangled sources at both ends of the optical fiber link drift by 0.1nm, a synchronization uncertainty of about 170ps will be introduced. At the same time, due to the increase in the asymmetry of the bidirectional link caused by wavelength drift, the time synchronization stability will also deteriorate significantly. In order to obtain higher synchronization stability and accuracy, a screening method is currently generally adopted to select a small number of devices with good wavelength stability from multiple nonlinear waveguides for experiments, resulting in a significant increase in the hardware cost of the system. To overcome this problem, it is crucial to achieve accurate real-time monitoring of the wavelength of the entangled two-photon source and then perform dynamic feedback stabilization through the measured value of the wavelength change.

[0004] In order to measure the wavelength of a single photon of an entangled two-photon source, all the previously proposed methods require a tunable filter to be connected to the optical path of the photon to be measured, and the spectrum intensity distribution of the photon is measured by scanning the wavelength of the filter. This type of frequency domain measurement method is easy to operate and has a wide range of uses, but it requires a long scanning time to obtain complete spectral information, so it cannot meet the above-mentioned application requirements of accurate real-time monitoring of the wavelength of the entangled two-photon source and stable dynamic feedback. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a wavelength measurement and feedback method of an entangled two-photon source based on wavelength-time mapping. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] A wavelength measurement method for an entangled two-photon source based on wavelength-time mapping is applied to a wavelength measurement device for an entangled two-photon source based on wavelength-time mapping, the measurement device comprising: an entangled two-photon source, a first single-photon detector, a second single-photon detector, a dense wavelength division multiplexer, a dispersion element and a time-correlated single-photon counter;

[0007] The method includes:

[0008] Selecting a number of different dense wavelength division multiplexer output channels to obtain a number of corresponding central values ​​of coincidence measurements, fitting the central values ​​of the number of coincidence measurements to obtain a dispersion coefficient value;

[0009] Select two output channels from the plurality of different dense wavelength division multiplexer output channels, adjust the temperature of the entangled two-photon source so that the single photon counts in the central wavelength windows of the two output channels are maximized, and record the corresponding temperature values ​​twice to obtain a temperature tuning coefficient;

[0010] A channel with a central wavelength as a preset wavelength is selected from the several different dense wavelength division multiplexer output channels, and the temperature of the entangled two-photon source is adjusted so that the single photon count in the preset wavelength window is maximized to obtain the center position of the distribution of the entangled two-photon source wavelength at the initial moment.

[0011] In a specific embodiment, the formula for fitting the central values ​​of the plurality of coincident measurements is:

[0012] τ=τ 0 +λ M GDD, where τ 0 is the bias term, GDD is the dispersion coefficient of the fiber Bragg grating, λ M is the central value of several consistent measurements.

[0013] In one embodiment, the temperature tuning coefficient is: Among them, λ M1 and λ M2 are the center wavelengths of the two output channels, T 1 and T 2 They are the temperature values ​​corresponding to the two output channels respectively.

[0014] The present invention also provides an entangled two-photon source wavelength feedback method based on wavelength-time mapping, comprising:

[0015] Obtain the coincident distribution center position of the entangled two-photon source at the initial moment;

[0016] Compare the coincidence distribution center position of the entangled two-photon source at different measurement times with the coincidence distribution center position at the initial moment to obtain the delay difference;

[0017] Obtaining a real-time wavelength change value of the entangled two-photon source at the measurement time according to the dispersion coefficient value and the time delay difference;

[0018] A real-time temperature adjustment amount is obtained according to the real-time wavelength change value, and the temperature of the entangled two-photon source is adjusted according to the real-time temperature adjustment amount to achieve wavelength feedback adjustment.

[0019] In a specific embodiment, obtaining the real-time temperature adjustment amount according to the real-time wavelength change value includes:

[0020] Performing proportional, integral and differential operations on the real-time wavelength change value to obtain a calibration wavelength error;

[0021] A real-time temperature adjustment amount is obtained according to the calibration wavelength error and the temperature tuning coefficient.

[0022] In a specific implementation, the wavelength error calculation formula is: Among them, K p , T i , T d are proportional, integral and differential coefficients respectively, Δλ(t n ) is the current original error, Δλ(t j ) is the real-time wavelength change value, Δλ(t j-1 ) is the wavelength change value at the previous moment, and T is the time difference.

[0023] The present invention also provides an entangled two-photon source wavelength feedback device based on wavelength-time mapping, comprising:

[0024] An initialization unit, used to obtain the coincidence distribution center position of the entangled two-photon source at the initial moment;

[0025] A wavelength change detection unit is used to compare the coincidence distribution center position of the entangled two-photon source at different measurement times with the coincidence distribution center position at the initial moment to obtain a delay difference, and obtain the real-time wavelength change value of the entangled two-photon source at the measurement time according to the dispersion coefficient value and the delay difference;

[0026] The wavelength feedback adjustment unit is used to obtain a real-time temperature adjustment amount according to the real-time wavelength change value, and adjust the temperature of the entangled two-photon source according to the real-time temperature adjustment amount to achieve wavelength feedback adjustment.

[0027] In a specific embodiment, the initialization unit includes: an entangled two-photon source, a first single-photon detector, a second single-photon detector, a dispersion element and a time-correlated single-photon counter; the entangled two-photon source is connected to the first single-photon detector and the dispersion element, the dispersion element is connected to the second single-photon detector, the first single-photon detector and the second single-photon detector are connected to the time-correlated single-photon counter, and the time-correlated single-photon counter is connected to the wavelength change detection unit.

[0028] In a specific embodiment, obtaining the real-time temperature adjustment amount according to the real-time wavelength change value includes:

[0029] Performing proportional, integral and differential operations on the real-time wavelength change value to obtain a calibration wavelength error;

[0030] A real-time temperature adjustment amount is obtained according to the calibration wavelength error and the temperature tuning coefficient.

[0031] In a specific implementation, the wavelength error calculation formula is: Among them, K p , T i , T d are proportional, integral and differential coefficients respectively, Δλ(t n ) is the current original error, Δλ(t j ) is the real-time wavelength change value, Δλ(t j-1 ) is the wavelength change value at the previous moment, and T is the time difference.

[0032] Beneficial effects of the present invention:

[0033] 1. The wavelength measurement method of the entangled two-photon source based on wavelength-time mapping of the present invention does not need to use a filter, and does not need to obtain the wavelength information of the entangled two-photon by wavelength scanning, which greatly reduces the measurement time and meets the demand for real-time wavelength measurement. At the same time, the method is compatible with quantum optical systems and has the advantages of low cost and easy implementation;

[0034] 2. The wavelength feedback method of the entangled two-photon source based on wavelength-time mapping of the present invention can further stabilize the working wavelength of the entangled two-photons. This method not only overcomes the influence of thermal residual stress caused by process defects of nonlinear waveguide on the wavelength stability of the output entangled two-photons, but also provides a means for improving the performance of entangled two-photon sources applied to various quantum information systems, thereby improving the performance of energy-time entangled two-photon sources.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic flow chart of a wavelength measurement method for an entangled two-photon source based on wavelength-time mapping provided by an embodiment of the present invention;

[0037] Figure 2 It is a module block diagram of an entangled two-photon source wavelength measurement device based on wavelength-time mapping provided by an embodiment of the present invention;

[0038] Figure 3 It is a schematic flow chart of a wavelength feedback method for an entangled two-photon source based on wavelength-time mapping provided by an embodiment of the present invention;

[0039] Figure 4a It is the wavelength change monitoring waveform without adding feedback device;

[0040] Figure 4b It is a wavelength change monitoring waveform added with the wavelength-time mapping-based entangled two-photon source wavelength feedback device of the present invention;

[0041] Figure 5 It is a module block diagram of an entangled two-photon source wavelength feedback device based on wavelength-time mapping provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0043] Embodiment 1

[0044] See also Figure 1 and Figure 2 , Figure 1 The present invention provides a method for measuring the wavelength of an entangled two-photon source based on wavelength-time mapping, which is applied to Figure 2An entangled two-photon source wavelength measurement device based on wavelength-time mapping, the measurement device comprising: an entangled two-photon source 1, a first single-photon detector 4, a second single-photon detector 5, a dense wavelength division multiplexer 2, a dispersion element 3 and a time-correlated single-photon counter 6; the entangled two-photon source is an energy-time entangled two-photon source, and its signal photon output port is connected to the first single-photon detector for detection, and the idle photons pass through the dense wavelength division multiplexer (DWDM), and one of the output channels is selected to be connected to the dispersion element based on the fiber Bragg grating (FBG), and the output end of the FBG is connected to the second single-photon detector, and the output ends of the first single-photon detector and the second single-photon detector are respectively connected to the time-correlated single-photon counter for coincidence measurement.

[0045] In implementation, the method includes:

[0046] S11, selecting a number of different dense wavelength division multiplexer output channels to obtain a number of corresponding central values ​​of coincidence measurements, and fitting the central values ​​of the number of coincidence measurements to obtain a dispersion coefficient value;

[0047] Specifically, the central value τ of the entangled two-photon correlation time distribution is obtained by fitting, which is consistent with the central wavelength λ of the DWDM output channel. M Directly corresponding, satisfying the relationship τ=τ 0 +λ M ·GDD. Among them, τ 0 is the bias term, GDD is the group velocity delay value of FBG, that is, the dispersion coefficient of FBG.

[0048] For the convenience of calculation, this embodiment selects three different DWDM output channels (with center wavelengths of λ M1 ,λ M2 ,λ M3 ), we can get three central values ​​τ that meet the measurement 1 , τ 2 , τ 3 . Through the formula τ=τ 0 +λ M GDD performs linear fitting on the measured data to obtain the dispersion coefficient value of FBG. This calibration is the prerequisite for the subsequent measurement of the wavelength of the entangled two-photon source.

[0049] S12, selecting two output channels from the plurality of different dense wavelength division multiplexer output channels, adjusting the temperature of the entangled two-photon source so that the single photon counts in the central wavelength windows of the two output channels are maximized, and recording the corresponding temperature values ​​twice to obtain a temperature tuning coefficient;

[0050] Specifically, two different DWDM output channels are selected, and their central wavelengths are λ M1 ,M2 , by adjusting the temperature controller of PPLN to change the temperature setting value, so that M1 , M2 The single photon counts under the two windows are the largest, and the corresponding temperature values ​​T are recorded twice 1 , T 2 , then the temperature tuning coefficient χ can be obtained from Given.

[0051] S13. Select a channel with a central wavelength as a preset wavelength from the several different dense wavelength division multiplexer output channels, and adjust the temperature of the entangled two-photon source so that the single photon count in the preset wavelength window is maximized to obtain the center position of the distribution of the entangled two-photon source wavelength at the initial moment.

[0052] Specifically, the central wavelength of the DWDM output channel is selected as the preset wavelength λ M0 , by adjusting the temperature controller of PPLN to change the temperature setting value, so that M0 The single photon count under the window is the largest, and the corresponding temperature value is T 0 is the initial operating temperature of PPLN. According to the law of conservation of energy, the central wavelength of the signal photon satisfies the formula This wavelength value is also the working wavelength when the entangled two-photon source is applied to practical systems.

[0053] The present invention also provides an entangled two-photon source wavelength feedback method based on wavelength-time mapping, comprising:

[0054] S21, obtaining the center position of the coincidence distribution of the entangled two-photon source at the initial moment; the center position of the coincidence distribution of the entangled two-photon source at the initial moment can be obtained through steps S11-S13.

[0055] S22, comparing the coincidence distribution center position of the entangled two-photon source at different measurement times with the coincidence distribution center position at the initial time, and obtaining the delay difference;

[0056] Specifically, we compare the entangled two-photon source at different measurement times (e.g., t j ) of the distribution center τ(t j ) relative to the initial time (t 0 ) of the distribution center τ(t 0 ), and obtain the delay difference Δτ(t j )=τ(t j )-τ(t 0 ).

[0057] S23, obtaining a real-time wavelength change value of the entangled two-photon source at the measurement time according to the dispersion coefficient value and the time delay difference;

[0058] Specifically, Δτ(t j ) divided by the dispersion coefficient value GDD, we can get the real-time wavelength change value Δλ(t j ).

[0059] S24. Obtain a real-time temperature adjustment amount according to the real-time wavelength change value, and adjust the temperature of the entangled two-photon source according to the real-time temperature adjustment amount to achieve wavelength feedback adjustment.

[0060] Specifically, according to the real-time wavelength change value Δλ(t j ) After proportional, integral, and differential operations (PID), by setting the proportional, integral, and differential coefficients K respectively p , T i , T d Value, get wavelength error Among them, K p , T i , T d are proportional, integral and differential coefficients respectively, Δλ(t n ) is the current original error, Δλ(t j ) is the real-time wavelength change value, Δλ(t j-1 ) is the wavelength change value at the previous moment, and T is the time difference. λ Divide by the temperature tuning coefficient χ to obtain the real-time temperature adjustment θ T , and serves as the input for temperature control of the entangled two-photon source, thereby controlling the wavelength change.

[0061] During simulation, see Figure 4a-4b Compared with the case where no feedback is added, the wavelength stability of the entangled two-photon source wavelength feedback method based on wavelength-time mapping in this embodiment is significantly improved.

[0062] Figure 5 This is a module block diagram of an entangled two-photon source wavelength feedback device based on wavelength-time mapping provided by an embodiment of the present invention, including:

[0063] An initialization unit, used to obtain the coincidence distribution center position of the entangled two-photon source at the initial moment;

[0064] A wavelength change detection unit is used to compare the coincidence distribution center position of the entangled two-photon source at different measurement times with the coincidence distribution center position at the initial moment to obtain a delay difference, and obtain a real-time wavelength change value of the entangled two-photon source at the measurement time according to the dispersion coefficient value and the delay difference;

[0065] The wavelength feedback adjustment unit is used to obtain a real-time temperature adjustment amount according to the real-time wavelength change value, and adjust the temperature of the entangled two-photon source according to the real-time temperature adjustment amount to achieve wavelength feedback adjustment.

[0066] In a specific embodiment, the initialization unit includes: an entangled two-photon source, a first single-photon detector, a second single-photon detector, a dispersion element and a time-correlated single-photon counter; the entangled two-photon source is connected to the first single-photon detector and the dispersion element, the dispersion element is connected to the second single-photon detector, the first single-photon detector and the second single-photon detector are connected to the time-correlated single-photon counter, and the time-correlated single-photon counter is connected to the wavelength change detection unit.

[0067] In a specific embodiment, obtaining the real-time temperature adjustment amount according to the real-time wavelength change value includes:

[0068] Performing proportional, integral and differential operations on the real-time wavelength change value to obtain a calibration wavelength error;

[0069] A real-time temperature adjustment amount is obtained according to the calibration wavelength error and the temperature tuning coefficient.

[0070] In a specific implementation, the wavelength error calculation formula is: Among them, K p , T i , T d are proportional, integral and differential coefficients respectively, Δλ(t n ) is the current original error, Δλ(t j ) is the real-time wavelength change value, Δλ(t j-1 ) is the wavelength change value at the previous moment, and T is the time difference.

[0071] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0072] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0073] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0074] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0076] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in a claim. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0077] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A wavelength measurement method for an entangled two-photon source based on wavelength-time mapping, characterized in that: The invention relates to an entangled two-photon source wavelength measurement device based on wavelength-time mapping, wherein the measurement device comprises: an entangled two-photon source, a first single-photon detector, a second single-photon detector, a dense wavelength division multiplexer, a dispersion element and a time-correlated single-photon counter; The method includes: Selecting a number of different dense wavelength division multiplexer output channels to obtain a number of corresponding central values ​​of coincidence measurements, fitting the central values ​​of the number of coincidence measurements to obtain a dispersion coefficient value; Select two output channels from the plurality of different dense wavelength division multiplexer output channels, adjust the temperature of the entangled two-photon source so that the single photon counts in the central wavelength windows of the two output channels are maximized, and record the corresponding temperature values ​​twice to obtain a temperature tuning coefficient; Selecting a channel with a central wavelength of a preset wavelength from the plurality of different dense wavelength division multiplexer output channels, adjusting the temperature of the entangled two-photon source so that the single photon count in the preset wavelength window is maximized, so as to obtain the coincident distribution center position of the entangled two-photon source wavelength at the initial moment; The measurement method also includes: obtaining the center position of the coincidence distribution of the entangled two-photon source at the initial moment; comparing the center position of the coincidence distribution of the entangled two-photon source at different measurement times relative to the center position of the coincidence distribution at the initial moment to obtain a delay difference; obtaining a real-time wavelength change value of the entangled two-photon source at the measurement time according to the dispersion coefficient value and the delay difference; obtaining a real-time temperature adjustment amount according to the real-time wavelength change value, and adjusting the temperature of the entangled two-photon source according to the real-time temperature adjustment amount to achieve wavelength feedback adjustment.

2. The wavelength measurement method of entangled two-photon source based on wavelength-time mapping according to claim 1 is characterized in that: The formula for fitting the central values ​​of the several coincident measurements is: τ=τ0+λ M ·GDD, where τ0 is the bias term, GDD is the dispersion coefficient of the fiber Bragg grating, and λ M is the central value of several consistent measurements.

3. The wavelength measurement method of entangled two-photon source based on wavelength-time mapping according to claim 1 is characterized in that: The temperature tuning coefficient is: Among them, λ M1 and λ M2 are the center wavelengths of the two output channels, and T1 and T2 are the temperature values ​​corresponding to the two output channels.

4. A wavelength feedback method for entangled two-photon source based on wavelength-time mapping, characterized in that: include: Obtain the coincident distribution center position of the entangled two-photon source at the initial moment; Compare the coincidence distribution center position of the entangled two-photon source at different measurement times with the coincidence distribution center position at the initial moment to obtain the delay difference; Obtaining a real-time wavelength change value of the entangled two-photon source at the measurement time according to the dispersion coefficient value and the time delay difference; Obtaining a real-time temperature adjustment amount according to the real-time wavelength change value, and adjusting the temperature of the entangled two-photon source according to the real-time temperature adjustment amount to achieve wavelength feedback adjustment; Among them, the center position of the coincidence distribution of the entangled two-photon source at the initial moment is obtained by the following method: select several different dense wavelength division multiplexer output channels to obtain the center values ​​corresponding to several coincidence measurements, fit the center values ​​of the several coincidence measurements to obtain the dispersion coefficient value; select two output channels from the several different dense wavelength division multiplexer output channels, adjust the temperature of the entangled two-photon source so that the single photon counts in the central wavelength windows of the two output channels are maximized, and record the corresponding temperature values ​​twice to obtain the temperature tuning coefficient; select a channel with a central wavelength as a preset wavelength from the several different dense wavelength division multiplexer output channels, adjust the temperature of the entangled two-photon source so that the single photon counts in the preset wavelength window are maximized, so as to obtain the center position of the coincidence distribution of the entangled two-photon source at the initial moment of the wavelength.

5. The entangled two-photon source wavelength feedback method based on wavelength-time mapping according to claim 4 is characterized in that: Obtaining a real-time temperature adjustment amount according to the real-time wavelength change value includes: Performing proportional, integral and differential operations on the real-time wavelength change value to obtain a calibration wavelength error; A real-time temperature adjustment amount is obtained according to the calibration wavelength error and the temperature tuning coefficient.

6. The entangled two-photon source wavelength feedback method based on wavelength-time mapping according to claim 5, characterized in that: The wavelength error calculation formula is: Among them, K p , T i , T d are proportional, integral and differential coefficients respectively, Δλ(t n ) is the current original error, Δλ(t j ) is the real-time wavelength change value, Δλ(t j-1 ) is the wavelength change value at the previous moment, and T is the time difference.

7. An entangled two-photon source wavelength feedback device based on wavelength-time mapping, characterized in that: include: An initialization unit, used to obtain the coincidence distribution center position of the entangled two-photon source at the initial moment; A wavelength change detection unit is used to compare the coincidence distribution center position of the entangled two-photon source at different measurement times with the coincidence distribution center position at the initial moment to obtain a delay difference, and obtain a real-time wavelength change value of the entangled two-photon source at the measurement time according to the dispersion coefficient value and the delay difference; A wavelength feedback adjustment unit, used to obtain a real-time temperature adjustment amount according to the real-time wavelength change value, and adjust the temperature of the entangled two-photon source according to the real-time temperature adjustment amount to achieve wavelength feedback adjustment; Among them, the center position of the coincidence distribution of the entangled two-photon source at the initial moment is obtained by the following method: select several different dense wavelength division multiplexer output channels to obtain the center values ​​corresponding to several coincidence measurements, fit the center values ​​of the several coincidence measurements to obtain the dispersion coefficient value; select two output channels from the several different dense wavelength division multiplexer output channels, adjust the temperature of the entangled two-photon source so that the single photon counts in the central wavelength windows of the two output channels are maximized, and record the corresponding temperature values ​​twice to obtain the temperature tuning coefficient; select a channel with a central wavelength as a preset wavelength from the several different dense wavelength division multiplexer output channels, adjust the temperature of the entangled two-photon source so that the single photon counts in the preset wavelength window are maximized, so as to obtain the center position of the coincidence distribution of the entangled two-photon source at the initial moment of the wavelength.

8. The entangled two-photon source wavelength feedback device based on wavelength-time mapping according to claim 7, characterized in that: The initialization unit includes: an entangled two-photon source, a first single-photon detector, a second single-photon detector, a dispersion element and a time-correlated single-photon counter; the entangled two-photon source is connected to the first single-photon detector and the dispersion element, the dispersion element is connected to the second single-photon detector, the first single-photon detector and the second single-photon detector are connected to the time-correlated single-photon counter, and the time-correlated single-photon counter is connected to the wavelength change detection unit.

9. The entangled two-photon source wavelength feedback device based on wavelength-time mapping according to claim 7, characterized in that: Obtaining a real-time temperature adjustment amount according to the real-time wavelength change value includes: Performing proportional, integral and differential operations on the real-time wavelength change value to obtain a calibration wavelength error; A real-time temperature adjustment amount is obtained according to the calibration wavelength error and the temperature tuning coefficient.

10. The entangled two-photon source wavelength feedback device based on wavelength-time mapping according to claim 9, characterized in that: The wavelength error calculation formula is: Among them, K p 、T i 、T d are proportional, integral and differential coefficients respectively, Δλ(t n ) is the current original error, Δλ(t j ) is the real-time wavelength change value, Δλ(t j-1 ) is the wavelength change value at the previous moment, and T is the time difference.

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