Long-distance weak signal detection system and method based on weak measurement technology enhancement

Abstract

The invention provides a remote weak signal detection system and method based on weak measurement technology enhancement, and can be applied to the technical field of signal detection. The system comprises a light source for providing initial signal light; the first beam splitter is used for splitting the initial signal light into first local oscillator light, second local oscillator light and signal light; the long-distance signal transmission simulation unit obtains intermediate signal light; the second beam splitter divides the intermediate signal light into first sub-intermediate signal light and second sub-intermediate signal light; the first signal action unit modulates the first sub-intermediate signal light into first post-selection signal light, and performs heterodyne detection on the first post-selection signal light and the first local oscillation light to obtain a first heterodyne detection result; the second signal action unit modulates the second sub-intermediate signal light into second post-selection signal light, heterodyne detection is carried out on the second post-selection signal light and the second local oscillator light, a second heterodyne detection result is obtained, and the first post-selection angle and the second post-selection angle are opposite numbers; and the signal processing unit obtains the phase of the signal to be detected.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of signal detection, and more particularly to a long-distance weak signal detection system and method based on weak measurement technology enhancement. BACKGROUND

[0002] Compared with radio frequency integrated communication and sensing systems, optical integrated communication and sensing systems can provide high-speed communication, higher resolution and more detailed environmental information due to excellent monochromaticity and coherence, wide bandwidth and small beam divergence angle. In optical integrated communication and sensing systems, the correlation, security and anti-noise performance of the signal can be improved by encoding the to-be-detected signal as a phase parameter, but long-distance transmission is usually required between the signal sensing unit and the signal processing unit, which can cause significant attenuation of the to-be-detected signal. Therefore, in the case of significant attenuation of the optical signal power under long-distance transmission, how to better extract the weak phase signal of the to-be-detected signal is a problem to be solved. SUMMARY

[0003] In view of this, the present disclosure provides a long-distance weak signal detection system and method based on weak measurement technology enhancement.

[0004] One aspect of the present disclosure provides a signal detection system, comprising: an optical source configured to provide initial signal light; a first beam splitter connected with the optical source and configured to divide the initial signal light into first local oscillator light, second local oscillator light and signal light; a long-distance signal transmission simulation unit connected with the first beam splitter and configured to modulate the signal light into pre-selected signal light, and under the action of a to-be-detected signal, the pre-selected signal light is transmitted for a preset distance to obtain intermediate signal light, wherein the light intensity of the intermediate signal light is less than the light intensity of the signal light; a second beam splitter connected with the long-distance signal transmission simulation unit and configured to divide the intermediate signal light into first intermediate signal light and second intermediate signal light; a first signal action unit connected with the first beam splitter and the second beam splitter respectively and configured to modulate the first intermediate signal light into first post-selected signal light according to a first post-selection angle, and perform heterodyne detection with the first local oscillator light to obtain a first heterodyne detection result; a second signal action unit connected with the first beam splitter and the second beam splitter respectively and configured to modulate the second intermediate signal light into second post-selected signal light according to a second post-selection angle, and perform heterodyne detection with the second local oscillator light to obtain a second heterodyne detection result, wherein the first post-selection angle and the second post-selection angle are opposite numbers; and a signal processing unit connected with the first signal action unit and the second signal action unit respectively and configured to obtain the phase of the to-be-detected signal according to the first heterodyne detection result and the second heterodyne detection result.

[0005] Another aspect of the present disclosure provides a signal detection method, comprising: providing initial signal light by using a light source; splitting the initial signal light into first local oscillator light, second local oscillator light and signal light by using a first beam splitter, wherein the first beam splitter is connected with the light source; modulating the signal light into pre-selected signal light by using a long-distance signal transmission analog unit, and under the action of a signal to be detected, the pre-selected signal light is transmitted through a preset distance to obtain intermediate signal light, wherein the light intensity of the intermediate signal light is less than the light intensity of the signal light, and the long-distance signal transmission analog unit is connected with the first beam splitter; splitting the intermediate signal light into first intermediate signal light and second intermediate signal light by using a second beam splitter, wherein the second beam splitter is connected with the long-distance signal transmission analog unit; modulating the first intermediate signal light into first post-selected signal light according to a first post-selection angle by using a first signal action unit, and performing heterodyne detection with the first local oscillator light to obtain a first heterodyne detection result, wherein the first signal action unit is connected with the first beam splitter and the second beam splitter respectively; modulating the second intermediate signal light into second post-selected signal light according to a second post-selection angle by using a second signal action unit, and performing heterodyne detection with the second local oscillator light to obtain a second heterodyne detection result, wherein the first post-selection angle and the second post-selection angle are opposite numbers, and the second signal action unit is connected with the first beam splitter and the second beam splitter respectively; calculating the phase of the signal to be detected according to the first heterodyne detection result and the second heterodyne detection result by using a signal processing unit, wherein the signal processing unit is connected with the first signal action unit and the second signal action unit respectively.

[0006] According to the embodiments of the present disclosure, the transmission of weak signal is simulated by the preset distance transmission of the signal, so that the signal to be detected can be better encoded into the signal light. In the double-channel signal action unit of the first signal action unit and the second signal action unit, the first intermediate signal light and the second intermediate signal light are symmetrized by the post-selection angles which are opposite numbers, so as to reduce the signal noise, improve the coherence of the signal light, and further amplify the signal to be detected by performing heterodyne detection of the first post-selected signal obtained through the first post-selection angle and the second post-selected signal obtained through the second post-selection angle with the local oscillator light, thereby improving the detection effect of the signal to be detected. BRIEF DESCRIPTION OF DRAWINGS

[0007] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which:

[0008] Figure 1 A block diagram of a long-distance weak signal detection system based on weak measurement technology enhancement according to an embodiment of the present disclosure is schematically shown;

[0009] Figure 2A block diagram of a long-range weak signal detection system enhanced based on weak measurement technique according to yet another embodiment of the present disclosure is schematically shown;

[0010] Figure 3 A structural block diagram of a first quantum heterodyne detector, a first balanced photodetector, and a second balanced photodetector according to an embodiment of the present disclosure is schematically shown.

[0011] Figure 4 A flowchart of a long-range weak signal detection method enhanced based on weak measurement technique according to an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood, however, that the description which follows is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it would be apparent to one skilled in the art that the present disclosure can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring the concepts of the present disclosure.

[0013] The terms used herein are merely used to describe specific embodiments and are not intended to limit the present disclosure. The terms "include", "comprise" and the like used herein indicate the presence of the described features, steps, operations, and / or components but do not preclude the presence or addition of one or more other features, steps, operations, or components.

[0014] All terms used herein, including technical and scientific terms, have the same meanings as commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings that are consistent with the context of the present description, and should not be interpreted in an idealized or excessively formal manner.

[0015] In the case of using expressions similar to "at least one of A, B, and C, etc.", it should generally be interpreted to include at least one of each item enumerated, unless otherwise defined. For example, "a system having at least one of A, B, and C" should be interpreted to include a system having at least one of A, a system having at least one of B, a system having at least one of C, a system having at least one of A and B, a system having at least one of A and C, a system having at least one of B and C, and / or a system having at least one of A, B, and C, etc.

[0016] In the related art, erbium-doped fiber amplifiers are used to amplify optical power, but in the process of amplifying signals, spontaneous emission noise and high power loss are introduced, and high power amplification can cause nonlinear effects in optical fibers, which all lead to a decrease in signal-to-noise ratio, limiting its applicability in detecting weak phase signals. In addition, based on noise suppression and signal enhancement algorithms, digital signal processing or machine learning technology is used to effectively improve the signal-to-noise ratio of weak signals in optical sensing and communication integration, helping the system to extract and reconstruct the attenuated signal from strong background noise, and enhance the signal recognition ability under long-distance transmission. However, this method relies on a large amount of training data or prior models, and the generalization ability is limited, and it requires high computing resources, leading to increased processing delay, making it difficult to meet the real-time requirements of high-speed communication. In view of this, the present disclosure proposes a signal detection system, as shown in Figure 1 .

[0017] Figure 1 A block diagram of a long-distance weak signal detection system enhanced based on weak measurement technology according to an embodiment of the present disclosure is shown schematically.

[0018] As shown in Figure 1 , the long-distance weak signal detection system enhanced based on weak measurement technology 100 includes a light source 110, a first beam splitter 120, a long-distance signal transmission simulation unit 130, a second beam splitter 140, a first signal action unit 150, a second signal action unit 160, and a signal processing unit 170.

[0019] The light source 110 is configured to provide initial signal light.

[0020] The first beam splitter 120 is connected with the light source 110 and is configured to divide the initial signal light into first local oscillator light, second local oscillator light, and signal light.

[0021] The long-distance signal transmission simulation unit 130 is connected with the first beam splitter 120 and is configured to modulate the signal light into pre-selected signal light, and under the action of the signal to be detected, the pre-selected signal light is transmitted for a predetermined distance to obtain intermediate signal light, wherein the light intensity of the intermediate signal light is less than that of the signal light.

[0022] The second beam splitter 140 is connected with the long-distance signal transmission simulation unit 130 and is configured to divide the intermediate signal light into first intermediate signal light and second intermediate signal light.

[0023] The first signal action unit 150 is connected with the first beam splitter 120 and the second beam splitter 140, respectively, and is configured to modulate the first intermediate signal light into first post-selected signal light according to the first post-selection angle, and perform heterodyne detection with the first local oscillator light to obtain the first heterodyne detection result.

[0024] The second signal acting unit 160 is connected with the first beam splitter 120 and the second beam splitter 140 respectively, and is configured to modulate the second sub-intermediate signal light into the second post-selection signal light according to the second post-selection angle, and perform heterodyne detection with the second local light to obtain the second heterodyne detection result, wherein the first post-selection angle and the second post-selection angle are opposite numbers.

[0025] The signal processing unit 170 is connected with the first signal acting unit 150 and the second signal acting unit 160 respectively, and is configured to obtain the phase of the to-be-detected signal according to the first heterodyne detection result and the second heterodyne detection result.

[0026] According to the embodiment of the present disclosure, the light source and the first beam splitter can be connected through an optical fiber, and the first beam splitter can be a fiber beam splitter, which divides the initial signal light into three paths, i.e., the first local light, the second local light, and the signal light.

[0027] According to the embodiment of the present disclosure, the first beam splitter and the long-distance signal transmission simulation unit and the first signal acting unit and the second signal acting unit can also be connected through an optical fiber.

[0028] According to the embodiment of the present disclosure, the long-distance signal transmission simulation unit can be used to simulate the transmission process of the weak signal, so that the to-be-detected signal can be better encoded into the signal light.

[0029] According to the embodiment of the present disclosure, the first sub-signal light and the second sub-signal light are symmetrically processed through the first post-selection angle and the second post-selection angle which are opposite numbers, which can reduce signal noise and improve the coherence of the signal light.

[0030] According to the embodiment of the present disclosure, the transmission of the weak signal is simulated through the preset distance of the signal, so that the to-be-detected signal can be better encoded into the signal light. In the double-path signal acting unit of the first signal acting unit and the second signal acting unit, the first sub-intermediate signal light and the second sub-intermediate signal light are symmetrically processed through the post-selection angle which are opposite numbers, which can reduce signal noise and improve the coherence of the signal light. Moreover, the first post-selection signal obtained through the first post-selection angle and the second post-selection signal obtained through the second post-selection angle are respectively subjected to heterodyne detection with the local light, which can further amplify the to-be-detected signal and improve the detection effect of the to-be-detected signal.

[0031] Figure 2 A block diagram of a long-distance weak signal detection system based on weak measurement technology enhancement according to yet another embodiment of the present disclosure is schematically shown.

[0032] As Figure 2As shown, the long-distance signal transmission simulation unit in the signal detection system 100 can include an optical attenuator 131, a pre-selection subunit 132, and a signal transmission simulation subunit 133. The first signal acting unit includes a first post-selection subunit 151, a first quantum heterodyne detector 152, a first balanced photodetector 153, and a second balanced photodetector 154. The second signal acting unit includes a second post-selection subunit 161, a second quantum heterodyne detector 162, a third balanced photodetector 163, and a fourth balanced photodetector 164.

[0033] The optical attenuator 131 is connected with the first beam splitter and is configured to attenuate the signal light to obtain attenuated signal light in a coherent state. The pre-selection subunit 132 is connected with the optical attenuator 131 and is configured to modulate the attenuated signal light into pre-selected signal light according to a pre-selection angle. The signal transmission simulation subunit 133 is connected with the pre-selection subunit 132 and is configured to encode the to-be-detected signal into the pre-selected signal light and transmit the pre-selected signal light through a preset distance to obtain intermediate signal light.

[0034] The first post-selection subunit 151 is connected with the second beam splitter and is configured to modulate the first intermediate signal light into first post-selected signal light according to a first post-selection angle. The first quantum heterodyne detector 152 is connected with the first beam splitter and the first post-selection subunit 151 respectively and is configured to mix the first post-selected signal light and the first local oscillator light to obtain first beat frequency light, second beat frequency light, third beat frequency light, and fourth beat frequency light. The first balanced photodetector 153 is connected with the first quantum heterodyne detector 152 and is configured to obtain first sub-heterodyne detection results by differentiating the first beat frequency light and the second beat frequency light, wherein the first sub-heterodyne detection results represent detection results of the first local oscillator light in a first phase state. The second balanced photodetector 154 is connected with the first quantum heterodyne detector 152 and is configured to obtain second sub-heterodyne detection results by differentiating the third beat frequency light and the fourth beat frequency light, wherein the second sub-heterodyne detection results represent detection results of the first local oscillator light in a second phase state.

[0035] The second rear selection subunit 161 is connected with the second beam splitter and is configured to modulate the second sub-intermediate signal light into the second rear selection signal light according to the second rear selection angle; the second quantum heterodyne detector 162 is connected with the second beam splitter and the second rear selection subunit respectively and is configured to mix the second rear selection signal light and the second local light to obtain the fifth beat frequency light, the sixth beat frequency light, the seventh beat frequency light and the eighth beat frequency light; the third balanced photodetector 163 is connected with the second quantum heterodyne detector and is configured to obtain the third sub-heterodyne detection result by differentiating the fifth beat frequency light and the sixth beat frequency light, wherein the third sub-heterodyne detection result represents the detection result of the second local light in the third phase state; the fourth balanced photodetector 164 is connected with the second quantum heterodyne detector and is configured to obtain the fourth sub-heterodyne detection result by differentiating the seventh beat frequency light and the eighth beat frequency light, wherein the fourth sub-heterodyne detection result represents the detection result of the second local light in the fourth phase state.

[0036] The initial signal light from the light source can pass through the first beam splitter and be divided into the signal light, the first local light and the second local light, the first local light and the second local light have large intensity and the same amplitude and can be regarded as classical light fields, the light intensity of the local light (the first local light or the second local light) can be expressed as wherein, is the amplitude of the local light (the first local light or the second local light), is the phase of the local light (the first local light or the second local light), is an imaginary unit, is the base number of the natural logarithm function.

[0037] The signal light passes through the optical attenuator for attenuation and is attenuated into the attenuated signal light in the coherent state, and the coherent state is taken as the pointer state, wherein, , is an imaginary unit, and are two regular components of the attenuated signal light in the coherent state, is the amplitude of the attenuated signal light, is the phase of the attenuated signal light, and then the coherent state is modulated into the pre-selection signal light in the pre-selection state by the pre-selection subunit wherein, , is the horizontal polarization state, is the vertical polarization state; the pre-selection subunit can be composed of a polarizer. In the signal transmission simulation subunit, the long-distance transmission of the analog signal, that is, the transmission of a preset distance, and under the influence of the to-be-detected signal, the phase of the pre-selection signal light changes, and the interaction can be expressed as: , is an observable operator , the amplitude is attenuated times, and the intermediate signal light obtained after long-distance transmission is .

[0038] According to the embodiment of the present disclosure, the pre-selected signal light is attenuated by simulating the transmission process of the weak signal, so that it can be better coupled with the to-be-detected signal to obtain the intermediate signal light, and the real-time detection of the weak time-varying signal is realized.

[0039] After the intermediate signal light passes through the second beam splitter, it is projected to the first signal acting unit and the second signal acting unit. A reflecting mirror 180 can be further arranged between the second beam splitter and the second signal acting unit, for reflecting the second sub-intermediate signal light to the second signal acting unit.

[0040] The first sub-intermediate signal light enters the first post-selection sub-unit, and the first post-selection sub-unit can be composed of a half-wave plate, a quarter-wave plate and a polarizer. Under the modulation of the first post-selection angle, the first post-selection signal light is obtained, which can be represented as the first post-selection state . The second sub-intermediate signal light enters the second post-selection sub-unit, and the second post-selection sub-unit can be composed of a half-wave plate, a quarter-wave plate and a polarizer. Under the modulation of the second post-selection angle, the second post-selection signal light is obtained, which can be represented as the second post-selection state , the first post-selection state and the second post-selection state are nearly orthogonal to the pre-selection state, wherein , , is the first post-selection angle, is the second post-selection angle. The first post-selection signal light obtained after passing through the first post-selection sub-unit is , and the second post-selection signal light obtained after passing through the second post-selection sub-unit is . The light intensity of the initial signal light can be represented as .

[0041] According to the embodiment of the present disclosure, the optical signal in the first post-selection sub-unit and the second post-selection sub-unit can be transmitted in free space, reducing the signal error caused by fiber vibration.

[0042] The first post-selection signal light and the second post-selection signal light can also be represented as and .

[0043] ​The first local oscillator light and the first post-selection signal light are mixed in the first quantum heterodyne detector to obtain first beat frequency light, second beat frequency light, third beat frequency light and fourth beat frequency light, which are then detected by the first balanced photodetector and the second balanced photodetector. The basic principle of heterodyne detection is the coherence of two light waves. The local oscillator light is added to the signal light, and the frequency of the local oscillator light is very close to the frequency of the signal light, so that the local oscillator light and the signal light form a beat frequency signal on the light-sensitive surface of the photodetector. Then the detector responds to the beat frequency signal, thereby detecting the modulation signal in the signal light. The principle diagram of the first quantum heterodyne detector, the first balanced photodetector and the second balanced photodetector is shown in Figure 3 .

[0044] Figure 3 The structural block diagram of the first quantum heterodyne detector, the first balanced photodetector and the second balanced photodetector according to the embodiment of the present disclosure is schematically shown.

[0045] As shown in Figure 3 , the first quantum heterodyne detector includes a third beam splitter 1521, a fourth beam splitter 1522, a first polarization controller 1523, a second polarization controller 1524, a fifth beam splitter 1525 and a sixth beam splitter 1526. The first balanced photodetector includes a first sub-detector 1531, a second sub-detector 1532 and a first differential amplifier 1533. The second balanced photodetector includes a third sub-detector 1541, a fourth sub-detector 1542 and a second differential amplifier 1543.

[0046] The third beam splitter 1521 is connected with the first post-selection sub-unit and is configured to divide the first post-selection signal light into first sub-post-selection signal light and second sub-post-selection signal light. The fourth beam splitter 1522 is connected with the first beam splitter and is configured to divide the first local oscillator light into first sub-local oscillator light and second sub-local oscillator light. The first polarization controller 1523 is connected with the fourth beam splitter and is configured to perform polarization control on the first sub-local oscillator light to obtain first sub-polarized light in a first phase state. The second polarization controller 1524 is connected with the fourth beam splitter and is configured to perform polarization control on the second sub-local oscillator light to obtain second sub-polarized light in a second phase state, wherein the first sub-polarized light and the second sub-polarized light are perpendicular to each other. The fifth beam splitter 1525 is connected with the third beam splitter and the first polarization controller and is configured to divide the first sub-post-selection signal light and the first sub-polarized light into first beat frequency light and second beat frequency light. The sixth beam splitter 1526 is connected with the third beam splitter and the second polarization controller and is configured to divide the second sub-post-selection signal light and the second sub-polarized light into third beat frequency light and fourth beat frequency light.

[0047] The first sub-detector 1531 is connected with the fifth beam splitter and is configured to detect the first beat frequency light; the second sub-detector 1532 is connected with the fifth beam splitter and is configured to detect the second beat frequency light; the first difference detector 1533 is connected with the first sub-detector 1531 and the second sub-detector 1532 and is configured to obtain the first sub-heterodyne detection result by differentiating the first beat frequency light and the second beat frequency light.

[0048] The third sub-detector 1541 is connected with the sixth beam splitter and is configured to detect the third beat frequency light; the fourth sub-detector 1542 is connected with the sixth beam splitter and is configured to detect the fourth beat frequency light; the second difference detector 1543 is connected with the third sub-detector 1541 and the fourth sub-detector 1542 and is configured to obtain the second sub-heterodyne detection result by differentiating the third beat frequency light and the fourth beat frequency light.

[0049] According to the embodiments of the present disclosure, the first post-selection signal light is divided into a first sub-post-selection signal light and a second sub-post-selection signal by the third beam splitter, and the first local oscillator light is divided into a first sub-local oscillator light and a second sub-local oscillator light by the fourth beam splitter. The first polarization controller performs polarization control on the first sub-local oscillator light to obtain the first sub-polarized light in the first phase state, and the second polarization controller performs polarization control on the second sub-local oscillator light to obtain the second sub-polarized light in the second phase state. The first polarization controller and the second polarization controller can be respectively set as and , so that the first sub-polarized light and the second sub-polarized light are perpendicular to each other. The first sub-polarized light and the first sub-post-selection signal light pass through the fifth beam splitter, the second sub-polarized light and the second sub-post-selection signal light pass through the sixth beam splitter, and four beat frequency lights are obtained, and the output light field mode corresponding to the annihilation operator of the first beat frequency light, the second beat frequency light, the third beat frequency light and the fourth beat frequency light is , , and , denoted as , , and . Therefore, the light intensity received by the first sub-detector, the second sub-detector, the third sub-detector and the fourth sub-detector can be respectively represented as , , and , wherein , , and are the corresponding creation operators; then, through the first difference detector and the second difference detector, the first sub-heterodyne detection result and the second sub-heterodyne detection result are output. Thus, the light intensity output by the first balanced photodetector and the second balanced photodetector is and .

[0050] According to an embodiment of the present disclosure, the second quantum heterodyne detector comprises a seventh beam splitter, an eighth beam splitter, a third polarization controller, a fourth polarization controller, a ninth beam splitter and a tenth beam splitter. The third balanced photodetector comprises a fifth sub-detector, a sixth sub-detector and a third difference detector. The fourth balanced photodetector comprises a seventh sub-detector, an eighth sub-detector and a fourth difference detector.

[0051] According to an embodiment of the present disclosure, the second quantum heterodyne detector, the third balanced photodetector and the fourth balanced photodetector are similar in structure to the first quantum heterodyne detector, the first balanced photodetector and the second balanced photodetector, and can refer to the description of Figure 3 , which will not be illustrated here.

[0052] The seventh beam splitter is connected with the second post-selection sub-unit and is configured to divide the second post-selection signal light into third and fourth post-selection signal light. The eighth beam splitter is connected with the first beam splitter and is configured to divide the second local oscillator light into third and fourth local oscillator light. The third polarization controller is connected with the eighth beam splitter and is configured to perform polarization control on the third local oscillator light to obtain third polarization light of a third phase state. The fourth polarization controller is connected with the eighth beam splitter and is configured to perform polarization control on the fourth local oscillator light to obtain fourth polarization light of a fourth phase state, wherein the third and fourth polarization light are perpendicular to each other. The ninth beam splitter is connected with the seventh beam splitter and the third polarization controller and is configured to divide the third post-selection signal light and the third polarization light into fifth and sixth beat frequency light. The tenth beam splitter is connected with the seventh beam splitter and the fourth polarization controller and is configured to divide the fourth post-selection signal light and the fourth polarization light into seventh and eighth beat frequency light.

[0053] The fifth sub-detector is connected with the ninth beam splitter and is configured to detect the fifth beat frequency light. The sixth sub-detector is connected with the ninth beam splitter and is configured to detect the sixth beat frequency light. The third difference detector is connected with the fifth and sixth sub-detectors and is configured to obtain third sub-heterodyne detection results after differentiating the fifth and sixth beat frequency light.

[0054] The seventh sub-detector is connected with the tenth beam splitter and is configured to detect the seventh beat frequency light. The eighth sub-detector is connected with the tenth beam splitter and is configured to detect the eighth beat frequency light. The fourth difference detector is connected with the seventh and eighth sub-detectors and is configured to obtain fourth sub-heterodyne detection results after differentiating the seventh and eighth beat frequency light.

[0055] According to an embodiment of the present disclosure, the second post-selection signal light is divided into a third sub-post-selection signal light and a fourth sub-post-selection signal light by the seventh beam splitter, and the second local oscillation light is divided into a third sub-local oscillation light and a fourth sub-local oscillation light by the eighth beam splitter. The third polarization controller performs polarization control on the third sub-local oscillation light to obtain a third sub-polarized light in a third phase state, and the fourth polarization controller performs polarization control on the fourth sub-local oscillation light to obtain a fourth sub-polarized light in a fourth phase state. The third polarization controller and the fourth polarization controller can be set to and , making the third sub-polarized light and the fourth sub-polarized light perpendicular to each other. The third sub-polarized light and the third sub-selected signal light pass through the ninth beam splitter, and the fourth sub-polarized light and the fourth sub-selected signal light pass through the tenth beam splitter, and four beat lights will be obtained. The annihilation operators corresponding to the output light field modes of the fifth beat light, the sixth beat light, the seventh beat light, and the eighth beat light are respectively 、 、 and Denoted as 、 、 and Therefore, the light intensities received by the fifth, sixth, seventh, and eighth sub-detectors can be expressed as 、 、 and ,in and is the corresponding generation operator; then, through the third and fourth differential circuits, the third sub-heterodyne detection result is output and the fourth sub-heterodyne detection results Therefore, the light intensity output by the third balanced photodetector and the fourth balanced photodetector is and .

[0056] According to the embodiments of the present disclosure, by combining weak measurement technology with heterodyne detection, the basic limitation of previous weak measurement systems, that is, light intensity attenuation due to nearly orthogonal front and back selection states, is effectively overcome.

[0057] According to an embodiment of the present disclosure, the signal processing unit can be configured to obtain the first sum of the squares of the light intensities of the first sub-heterodyne detection result and the second sub-heterodyne detection result; obtain the second sum of the squares of the light intensities of the third sub-heterodyne detection result and the fourth sub-heterodyne detection result; obtain the phase change of the signal to be detected during the transmission process based on the first sum of the squares of the light intensity and the second sum of the squares of the light intensity; and obtain the phase of the detection signal based on the phase change.

[0058] The first sub-heterodyne detection result, the second sub-heterodyne detection result, the third sub-heterodyne detection result and the fourth sub-heterodyne detection result are input to the signal processing unit, the first sub-heterodyne detection result and the second sub-heterodyne detection result are subjected to a square sum operation, and a first light intensity square sum is obtained and represented as The third sub-heterodyne detection result and the fourth sub-heterodyne detection result are subjected to a square sum operation, and a second light intensity square sum is obtained and represented as .

[0059] Under the condition of satisfying the weak measurement condition and , the first light intensity square sum and the second light intensity square sum can be approximated as , , wherein , , represents the imaginary part of a complex number.

[0060] According to an embodiment of the present disclosure, in an ideal case, the amount of phase change caused by the to-be-detected signal in the long-distance transmission process is , and thus the phase of the detection signal is .

[0061] According to actual implementation, due to the post-selection angle adjustment error and the device error, the optical powers of the two signal lights will be attenuated differently. Therefore, the signal processing unit is further configured to: obtain a first attenuation coefficient of the first light intensity square sum and a second attenuation coefficient of the second light intensity square sum; obtain a first post-selection angle adjustment error corresponding to the first post-selection angle and a second post-selection angle adjustment error corresponding to the second post-selection angle; determine a light intensity compensation coefficient according to the first attenuation coefficient, the second attenuation coefficient, the first post-selection angle, the second post-selection angle, the first post-selection angle adjustment error and the second post-selection angle adjustment error. The light intensity compensation coefficient is used to compensate the first light intensity square sum to obtain a compensated light intensity square sum; and the compensated light intensity square sum and the second light intensity square sum are used to obtain a compensated phase change amount of the to-be-detected signal in the transmission process; and the compensated phase change amount is used to calculate a compensated phase of the to-be-detected signal.

[0062] According to an embodiment of the present disclosure, the first attenuation coefficient of the first light intensity square sum is , and the light intensity of the first light intensity square sum after considering the transmission attenuation is , the second attenuation coefficient of the second light intensity square sum is , and the light intensity of the second light intensity square sum after considering the transmission attenuation is , wherein and are the errors of the first post-selection angle and the second post-selection angle adjustment, , The relative change of the to-be-detected signal in the long-distance transmission process is , which indicates that there is an additional bias and the amplification coefficient also has an error.

[0063] Therefore, the light intensity compensation can be used for optimization. Specifically, the light intensity compensation coefficient is determined according to the first attenuation coefficient, the second attenuation coefficient, the first back selection angle, the second back selection angle, the first back selection angle adjustment error, and the second back selection angle adjustment error The light intensity compensation is performed on the first light intensity square sum according to the light intensity compensation coefficient, and the first light intensity square sum is multiplied by the light intensity compensation coefficient. In this case, the relative change of the to-be-detected signal in the long-distance transmission process is represented as , the additional bias is eliminated, and the amplification coefficient is changed from to . Then, the phase of the to-be-detected signal is calculated.

[0064] According to the embodiments of the present disclosure, the light intensity compensation is introduced because the attenuation of the light intensity is considered, and the compensation operation is only performed on the light intensity of one path, thereby eliminating the strict requirement of the symmetry of the two back selection paths in the double-path weak measurement system and further improving the detection accuracy.

[0065] Figure 4 A flowchart of a long-distance weak signal detection method based on a weak measurement technology enhancement according to an embodiment of the present disclosure is schematically shown.

[0066] As shown in Figure 4 , the long-distance weak signal detection method based on the weak measurement technology enhancement includes operations S410 to S470.

[0067] In operation S410, an initial signal light is provided by using a light source.

[0068] In operation S420, the initial signal light is divided into a first local oscillator light, a second local oscillator light, and a signal light by using a first beam splitter.

[0069] In operation S430, the signal light is modulated into a pre-selection signal light by using a long-distance signal transmission simulation unit, and the pre-selection signal light is transmitted for a preset distance to obtain an intermediate signal light under the action of a to-be-detected signal.

[0070] In operation S440, the intermediate signal light is divided into a first intermediate signal light and a second intermediate signal light by using a second beam splitter.

[0071] In operation S450, the first intermediate signal light is modulated into a first back selection signal light according to a first back selection angle by using a first signal action unit, and the first back selection signal light is heterodyne detected with the first local oscillator light to obtain a first heterodyne detection result.

[0072] In operation S460, the second signal acting unit modulates the second sub-intermediate signal light into second post-selection signal light according to the second post-selection angle, and performs heterodyne detection with the second local light to obtain a second heterodyne detection result.

[0073] In operation S470, the signal processing unit calculates the phase of the to-be-detected signal according to the first heterodyne detection result and the second heterodyne detection result.

[0074] The first beam splitter is connected with the light source, the light intensity of the intermediate signal light is less than that of the signal light, the remote signal transmission simulation unit is connected with the first beam splitter, the second beam splitter is connected with the remote signal transmission simulation unit, the first signal acting unit is connected with the first beam splitter and the second beam splitter respectively, the first post-selection angle and the second post-selection angle are opposite numbers, the second signal acting unit is connected with the first beam splitter and the second beam splitter respectively, and the signal processing unit is connected with the first signal acting unit and the second signal acting unit respectively.

[0075] According to the embodiments of the present disclosure, operations S410~operation S470 can refer to the description of other embodiments of the present disclosure, which will not be repeated here.

[0076] The flowcharts and block diagrams in the drawings illustrate the possible implementation architecture, function and operation of the system, method and computer program product according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram can represent a module, a program segment, or a part of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in different order from that shown in the drawings. For example, two blocks that are shown in succession can actually be executed substantially in parallel, and sometimes they can be executed in reverse order, depending on the function involved. It should also be noted that each block in the block diagram or flowchart, and the combination of blocks in the block diagram or flowchart, can be implemented by a dedicated hardware-based system that performs the specified function or operation, or can be implemented by a combination of special-purpose hardware and computer instructions. Those skilled in the art can understand that the features described in various embodiments of the present disclosure can be combined and / or integrated in various combinations, even if such combinations or integrations are not explicitly described in the present disclosure. In particular, the features described in various embodiments of the present disclosure can be combined and / or integrated in various combinations without departing from the spirit and teachings of the present disclosure. All these combinations and / or integrations fall within the scope of the present disclosure.

[0077] The above describes embodiments of the present disclosure. However, these embodiments are merely for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above separately, this does not mean that the measures in each embodiment cannot be used advantageously in combination. Those skilled in the art can make various substitutions and modifications without departing from the scope of the present disclosure, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims

1. A long-distance weak signal detection system based on enhanced weak measurement technology, comprising: a light source configured to provide an initial signal light; a first beam splitter, connected to the light source, configured to split the initial signal light into a first local oscillation light, a second local oscillation light, and a signal light; a long-distance signal transmission simulation unit connected to the first beam splitter and configured to modulate the signal light into a pre-selected signal light, and transmit the pre-selected signal light over a preset distance under the action of the signal to be detected to obtain an intermediate signal light, wherein the intensity of the intermediate signal light is less than the intensity of the signal light; a second beam splitter connected to the long-distance signal transmission simulation unit and configured to split the intermediate signal light into a first sub-intermediate signal light and a second sub-intermediate signal light; a first signal processing unit, connected to the first beam splitter and the second beam splitter, respectively, and configured to modulate the first sub-intermediate signal light into a first post-selected signal light according to a first post-selection angle, and perform heterodyne detection with the first local oscillator light to obtain a first heterodyne detection result; a second signal processing unit, connected to the first beam splitter and the second beam splitter, respectively, and configured to modulate the second sub-intermediate signal light into a second post-selected signal light according to a second post-selection angle, and perform heterodyne detection with the second local oscillator light to obtain a second heterodyne detection result, wherein the first post-selection angle and the second post-selection angle are opposite to each other; The signal processing unit is connected to the first signal action unit and the second signal action unit respectively, and is configured to obtain the phase of the signal to be detected according to the first heterodyne detection result and the second heterodyne detection result.

2. The detection system according to claim 1, wherein: The long-distance signal transmission simulation unit includes: an optical attenuator, connected to the first beam splitter, and configured to attenuate the signal light to obtain attenuated signal light in a coherent state; a front selection subunit, connected to the optical attenuator, and configured to modulate the attenuated signal light into the front selection signal light according to a front selection angle; The signal transmission simulation subunit is connected to the pre-selection subunit and is configured to encode the signal to be detected into the pre-selection signal light and transmit it over the preset distance to obtain the intermediate signal light.

3. The detection system according to claim 2, wherein: The first signal action unit includes: a first post-selection subunit, connected to the second beam splitter, configured to modulate the first sub-intermediate signal light into the first post-selection signal light according to the first post-selection angle; a first quantum heterodyne detector, connected to the first beam splitter and the first post-selection subunit, respectively, and configured to mix the first post-selection signal light and the first local oscillator light to obtain a first beat frequency light, a second beat frequency light, a third beat frequency light, and a fourth beat frequency light; a first balanced photodetector, connected to the first quantum heterodyne detector, configured to obtain a first sub-heterodyne detection result after performing a differential operation on the first beat frequency light and the second beat frequency light, wherein the first sub-heterodyne detection result represents a detection result of the first local oscillator light in a first phase state; a second balanced photodetector, connected to the first quantum heterodyne detector, and configured to obtain a second sub-heterodyne detection result after differentiating the third beat frequency light and the fourth beat frequency light, wherein the second sub-heterodyne detection result represents a detection result of the first local oscillator light in the second phase state.

4. The detection system according to claim 3, wherein: The first quantum heterodyne detector comprises: a third beam splitter, connected to the first post-selection sub-unit, configured to split the first post-selection signal light into a first sub-post-selection signal light and a second sub-post-selection signal light; a fourth beam splitter, connected to the first beam splitter, configured to split the first local oscillation light into a first sub-local oscillation light and a second sub-local oscillation light; a first polarization controller, connected to the fourth beam splitter, and configured to perform polarization control on the first sub-local oscillation light to obtain a first sub-polarized light in the first phase state; a second polarization controller, connected to the fourth beam splitter, configured to perform polarization control on the second sub-local oscillation light to obtain a second sub-polarized light in the second phase state, wherein the first sub-polarized light and the second sub-polarized light are perpendicular to each other; a fifth beam splitter, connected to the third beam splitter and the first polarization controller, and configured to split the first sub-post-selected signal light and the first sub-polarized light into the first beat frequency light and the second beat frequency light; The sixth beam splitter is connected to the third beam splitter and the second polarization controller, and is configured to split the second sub-post-selection signal light and the second sub-polarized light into the third beat frequency light and the fourth beat frequency light.

5. The detection system according to claim 3, wherein: The second signal action unit includes: a second post-selection subunit, connected to the second beam splitter, configured to modulate the second sub-intermediate signal light into the second post-selection signal light according to the second post-selection angle; a second quantum heterodyne detector, connected to the second beam splitter and the second post-selection subunit, respectively, and configured to mix the second post-selection signal light and the second local oscillator light to obtain a fifth beat frequency light, a sixth beat frequency light, a seventh beat frequency light, and an eighth beat frequency light; a third balanced photodetector, connected to the second quantum heterodyne detector, configured to perform a differential operation on the fifth beat frequency light and the sixth beat frequency light to obtain a third sub-heterodyne detection result, wherein the third sub-heterodyne detection result represents a detection result of the second local oscillator light in a third phase state; a fourth balanced photodetector, connected to the second quantum heterodyne detector, and configured to obtain a fourth sub-heterodyne detection result after differentiating the seventh beat frequency light and the eighth beat frequency light, wherein the fourth sub-heterodyne detection result represents a detection result of the second local oscillation light in a fourth phase state.

6. The detection system according to claim 5, wherein: The second quantum heterodyne detector comprises: a seventh beam splitter, connected to the second post-selection sub-unit, and configured to split the second post-selection signal light into a third sub-post-selection signal light and a fourth sub-post-selection signal light; an eighth beam splitter, connected to the first beam splitter, and configured to split the second local oscillation light into a third sub-local oscillation light and a fourth sub-local oscillation light; a third polarization controller, connected to the eighth beam splitter, and configured to perform polarization control on the third sub-local oscillation light to obtain a third sub-polarized light in the third phase state; a fourth polarization controller, connected to the eighth beam splitter, and configured to perform polarization control on the fourth sub-local oscillation light to obtain a fourth sub-polarized light in the fourth phase state, wherein the third sub-polarized light and the fourth sub-polarized light are perpendicular to each other; a ninth beam splitter, connected to the seventh beam splitter and the third polarization controller, and configured to split the third sub-post-selection signal light and the third sub-polarized light into the fifth beat frequency light and the sixth beat frequency light; The tenth beam splitter is connected to the seventh beam splitter and the fourth polarization controller, and is configured to split the fourth sub-post-selection signal light and the fourth sub-polarized light into the seventh beat frequency light and the eighth beat frequency light.

7. The detection system according to claim 5, wherein the signal processing unit is configured as follows: Acquire a first light intensity square sum of the first sub-heterodyne detection result and the second sub-heterodyne detection result; Obtaining a second light intensity square sum of the third sub-heterodyne detection result and the fourth sub-heterodyne detection result; Obtaining a phase change of the signal to be detected during transmission according to the square of the first light intensity and the sum of the square of the second light intensity; The phase of the detection signal is obtained according to the phase change amount.

8. The detection system according to claim 7, wherein the signal processing unit is further configured to: Performing light intensity compensation on the first light intensity square sum according to the light intensity compensation coefficient to obtain a compensated light intensity square sum; Obtaining a compensated phase change amount of the signal to be detected during transmission according to the square sum of the compensated light intensities and the square sum of the second light intensities; The compensation phase of the signal to be detected is calculated according to the compensation phase change amount.

9. The detection system according to claim 8, wherein the signal processing unit is further configured to: Obtaining a first attenuation coefficient of the sum of the squares of the first light intensities and a second attenuation coefficient of the sum of the squares of the second light intensities; obtaining a first rear selection angle adjustment error corresponding to the first rear selection angle and a second rear selection angle adjustment error corresponding to the second rear selection angle; The light intensity compensation coefficient is determined according to the first attenuation coefficient, the second attenuation coefficient, the first rear selection angle, the second rear selection angle, the first rear selection angle adjustment error, and the second rear selection angle adjustment error.

10. A method for detecting long-distance weak signals based on enhanced weak measurement technology, comprising: Using a light source to provide an initial signal light; Using a first beam splitter to split the initial signal light into a first local oscillation light, a second local oscillation light, and a signal light, wherein the first beam splitter is connected to the light source; The signal light is modulated into a pre-selected signal light by a long-distance signal transmission simulation unit, and under the action of the signal to be detected, the pre-selected signal light is transmitted over a preset distance to obtain an intermediate signal light, wherein the intensity of the intermediate signal light is less than the intensity of the signal light, and the long-distance signal transmission simulation unit is connected to the first beam splitter; using a second beam splitter to split the intermediate signal light into a first sub-intermediate signal light and a second sub-intermediate signal light, wherein the second beam splitter is connected to the long-distance signal transmission simulation unit; using a first signal action unit to modulate the first sub-intermediate signal light into a first post-selected signal light according to a first post-selection angle, and performing heterodyne detection with the first local oscillator light to obtain a first heterodyne detection result, wherein the first signal action unit is connected to the first beam splitter and the second beam splitter respectively; using a second signal action unit to modulate the second sub-intermediate signal light into a second post-selected signal light according to a second post-selection angle, and performing heterodyne detection with the second local oscillator light to obtain a second heterodyne detection result, wherein the first post-selection angle and the second post-selection angle are opposite to each other, and the second signal action unit is connected to the first beam splitter and the second beam splitter respectively; A signal processing unit is used to calculate the phase of the signal to be detected based on the first heterodyne detection result and the second heterodyne detection result, wherein the signal processing unit is connected to the first signal action unit and the second signal action unit respectively.

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