System and method for enhanced long-range weak signal detection based on weak measurement technique

Abstract

The disclosure provides a weak measurement technology enhanced long-distance weak signal detection system and method, which can be applied to the technical field of signal detection. The system comprises: a light source providing initial signal light; a first beam splitter dividing the initial signal light into first local oscillator light, second local oscillator light and signal light; a long-distance signal transmission simulation unit obtaining intermediate signal light; a second beam splitter dividing the intermediate signal light into first intermediate signal light and second intermediate signal light; a first signal action unit modulating the first intermediate signal light into first post-selection signal light, performing heterodyne detection with the first local oscillator light, and obtaining a first heterodyne detection result; a second signal action unit modulating the second intermediate signal light into second post-selection signal light, performing heterodyne detection with the second local oscillator light, and obtaining a second heterodyne detection result, the first post-selection angle and the second post-selection angle being opposite numbers; and a signal processing unit obtaining the phase of the signal to be detected.

Description

Technical Field

[0001] This disclosure relates to the field of signal detection technology, and more specifically, to a long-distance weak signal detection system and method based on weak measurement technology enhancement. Background Technology

[0002] Optical integrated communication and sensing systems, benefiting from excellent monochromaticity and coherence, wide bandwidth, and small beam divergence angle, offer higher-speed communication, higher resolution, and more detailed environmental information compared to radio frequency integrated communication and sensing systems. In optical integrated communication and sensing systems, encoding the signal to be detected as a phase parameter can improve signal correlation, security, and noise immunity. However, long-distance transmission between the signal sensing unit and the signal processing unit typically leads to significant attenuation of the detected signal. Therefore, how to better extract the weak phase signal of the detected signal under the condition of significant optical signal power attenuation during long-distance transmission is a problem that urgently needs to be solved. Summary of the Invention

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

[0004] One aspect of this disclosure provides a signal detection system, comprising: a light source configured to provide initial signal light; a first beam splitter connected to the light source and configured to split the initial signal light into a first local oscillator beam, a second local oscillator beam, 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, wherein, under the action of a 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; 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; and a first signal application unit connected to the first beam splitter. The system is connected to the first beam splitter and the second beam splitter, and is configured to modulate the first sub-intermediate signal light into a first post-selection 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; the system is connected to the first beam splitter and the second beam splitter, and is configured to modulate the second sub-intermediate signal light into a second post-selection 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 opposites of each other; the system is connected to the first signal processing unit and the second signal processing unit, 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.

[0005] Another aspect of this disclosure provides a signal detection method, comprising: providing initial signal light using a light source; dividing the initial signal light into a first local oscillator beam, a second local oscillator beam, and a signal light using a first beam splitter, wherein the first beam splitter is connected to the light source; modulating the signal light into a pre-selection signal light using a long-distance signal transmission simulation unit, and under the action of a signal to be detected, the pre-selection 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; dividing the intermediate signal light into a first sub-intermediate signal light and a second sub-intermediate signal light using a second beam splitter, wherein the second beam splitter is connected to the long-distance signal transmission simulation unit; and using a first signal action unit to divide the signal light into a first post-selection angle. The first sub-intermediate signal light is modulated into a first post-selection signal light and heterodyne-detected with the first local oscillator light to obtain a first heterodyne detection result. The first signal processing unit is connected to the first beam splitter and the second beam splitter, respectively. The second signal processing unit modulates the second sub-intermediate signal light into a second post-selection signal light according to a second post-selection angle and heterodyne-detects it with the second local oscillator light to obtain a second heterodyne detection result. The first post-selection angle and the second post-selection angle are opposites of each other. The second signal processing unit is connected to the first beam splitter and the second beam splitter, respectively. The signal processing unit calculates the phase of the signal to be detected based on the first and second heterodyne detection results. The signal processing unit is connected to both the first and second signal processing units.

[0006] According to embodiments of this disclosure, weak signal transmission is simulated by transmitting the signal over a preset distance, allowing the signal to be detected to be better encoded into the signal light. In the dual-path signal processing unit of the first and second signal processing units, the first and second sub-intermediate signal lights are symmetrically processed by using post-selection angles that are opposite to each other, which can reduce signal noise and improve the coherence of the signal light. Furthermore, the first post-selection signal obtained after the first post-selection angle and the second post-selection signal obtained after the second post-selection angle are heterodyne-detected with the local oscillator light, which can further amplify the signal to be detected and improve the detection effect of the signal to be detected. Attached Figure Description

[0007] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

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

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

[0010] Figure 3 A schematic block diagram illustrating a first quantum heterodyne detector, a first balanced photodetector, and a second balanced photodetector according to embodiments of the present disclosure is shown.

[0011] Figure 4 A flowchart illustrating a long-range weak signal detection method based on weak measurement techniques enhanced according to an embodiment of the present disclosure is shown. Detailed Implementation

[0012] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0013] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude 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 meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0015] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0016] In related technologies, erbium-doped fiber amplifiers are used to amplify optical power. However, this amplification introduces spontaneous emission noise and high power loss. Furthermore, high-power amplification can lead to nonlinear effects in the fiber, all of which reduce the signal-to-noise ratio (SNR) and limit its applicability for detecting weak phase signals. Additionally, noise suppression and signal enhancement algorithms in optical-sensing integration effectively improve the SNR of weak signals through digital signal processing or machine learning techniques, helping the system extract and reconstruct attenuated signals from strong background noise and enhancing signal identification capabilities over long distances. However, this method relies on large amounts of training data or prior models, limiting its generalization ability. It also demands high computational resources, leading to increased processing latency and making it difficult to meet the real-time requirements of high-speed communication. Therefore, this disclosure proposes a signal detection system, such as... Figure 1 As shown.

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

[0018] like Figure 1 As shown, the long-distance weak signal detection system 100 based on weak measurement technology 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 processing unit 150, a second signal processing unit 160, and a signal processing unit 170.

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

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

[0021] The long-distance signal transmission simulation unit 130 is connected to the first beam splitter 120 and is configured to modulate the signal light into a pre-selection signal light. Under the action of the signal to be detected, the pre-selection signal light is transmitted over a preset distance to obtain an intermediate signal light, wherein the light intensity of the intermediate signal light is less than the light intensity of the signal light.

[0022] The second beam splitter 140 is connected to the long-distance signal transmission analog unit 130 and is configured to split the intermediate signal light into a first sub-intermediate signal light and a second sub-intermediate signal light.

[0023] The first signal processing unit 150 is connected to the first beam splitter 120 and the second beam splitter 140 respectively, and is configured to modulate the first sub-intermediate signal light into the first post-selection 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 processing unit 160 is connected to the first beam splitter 120 and the second beam splitter 140 respectively. It 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 oscillator light to obtain the second heterodyne detection result. The first post-selection angle and the second post-selection angle are opposites of each other.

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

[0026] According to embodiments of this disclosure, the light source and the first beam splitter can be connected by optical fiber. The first beam splitter can be an optical fiber beam splitter that splits the initial signal light into three paths: a first local oscillator light, a second local oscillator light, and a signal light.

[0027] According to embodiments of this disclosure, the first beam splitter and the long-distance signal transmission simulation unit, as well as the first signal action unit and the second signal action unit, can also be connected via optical fiber.

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

[0029] According to embodiments of this disclosure, the first sub-signal light and the second sub-signal light are symmetrically processed by using a first post-selection angle and a second post-selection angle that are opposite numbers to each other, which can reduce signal noise and improve the coherence of the signal light.

[0030] According to embodiments of this disclosure, weak signal transmission is simulated by transmitting the signal over a preset distance, allowing the signal to be detected to be better encoded into the signal light. In the dual-path signal processing unit of the first and second signal processing units, the first and second sub-intermediate signal lights are symmetrically processed by using post-selection angles that are opposite to each other, which can reduce signal noise and improve the coherence of the signal light. Furthermore, the first post-selection signal obtained after the first post-selection angle and the second post-selection signal obtained after the second post-selection angle are heterodyne-detected with the local oscillator light, which can further amplify the signal to be detected and improve the detection effect of the signal to be detected.

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

[0032] like Figure 2As shown, the long-distance signal transmission simulation unit in the signal detection system 100 may include an optical attenuator 131, a pre-selection subunit 132, and a signal transmission simulation subunit 133. The first signal processing 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 processing 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 to the first beam splitter and is configured to attenuate the signal light to obtain a coherent attenuated signal light. The pre-selection subunit 132 is connected to the optical attenuator 131 and is configured to modulate the attenuated signal light into a pre-selection signal light according to the pre-selection angle. The signal transmission simulation subunit 133 is connected to the pre-selection subunit 132 and is configured to encode the signal to be detected into the pre-selection signal light and transmit it over a preset distance to obtain an intermediate signal light.

[0034] The first post-selection subunit 151 is connected to the second beam splitter and configured to modulate the first sub-intermediate signal light into the first post-selection signal light according to the first post-selection angle; the first quantum heterodyne detector 152 is connected to the first beam splitter and the first post-selection subunit 151 respectively and configured to mix the first post-selection signal light and the first local oscillator light to obtain the first beat frequency light, the second beat frequency light, the third beat frequency light and the fourth beat frequency light; the first balanced photodetector 153 is connected to the first quantum heterodyne detector 152 and configured to perform differential analysis on the first beat frequency light and the second beat frequency light to obtain the first sub-heterodyne detection result, wherein the first sub-heterodyne detection result represents the detection result of the first local oscillator light in the first phase state; the second balanced photodetector 154 is connected to the first quantum heterodyne detector 152 and configured to perform differential analysis on the third beat frequency light and the fourth beat frequency light to obtain the second sub-heterodyne detection result, wherein the second sub-heterodyne detection result represents the detection result of the first local oscillator light in the second phase state.

[0035] The second post-selection subunit 161 is connected to the second beam splitter and configured to modulate the second sub-intermediate signal light into the second post-selection signal light according to the second post-selection angle; the second quantum heterodyne detector 162 is 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 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 to the second quantum heterodyne detector and configured to perform differential analysis on the fifth beat frequency light and the sixth beat frequency light to obtain the third sub-heterodyne detection result, wherein the third sub-heterodyne detection result characterizes the detection result of the second local oscillator light in the third phase state; the fourth balanced photodetector 164 is connected to the second quantum heterodyne detector and configured to perform differential analysis on the seventh beat frequency light and the eighth beat frequency light to obtain the fourth sub-heterodyne detection result, wherein the fourth sub-heterodyne detection result characterizes the detection result of the second local oscillator light in the fourth phase state.

[0036] The initial signal light from the light source can be split into a signal light, a first local oscillator beam, and a second local oscillator beam by a first beam splitter. The first and second local oscillator beams have relatively high intensities and the same amplitude, and can be considered as a classical light field. The light intensity of the local oscillator beams (the first and second local oscillator beams) can be expressed as... ,in, It is the amplitude of the local oscillator (either the first or second local oscillator). It is the phase of the local oscillator (either the first or second local oscillator). It is the imaginary unit. It is the base of the natural logarithm function.

[0037] The signal light is attenuated by the optical attenuator, becoming a coherent attenuated signal light, and the coherent state is then... As a pointer state, where, , It is the imaginary unit. and These are the two canonical components of the attenuated signal light in the coherent state. It attenuates the amplitude of the signal light. It attenuates the phase of the signal light, and then converts the coherent state... The preselection signal light modulated into a preselection state by the preselection subunit ,in, , It is a horizontal polarization state. It is a vertically polarized state; the pre-selection subunit can be composed of polarizers. In the signal transmission simulation subunit, the long-distance transmission of the simulated signal is performed, i.e., transmission over a preset distance, and the phase of the pre-selection signal light is adjusted under the influence of the signal to be detected. Changes, interactions It can be represented as: , It is an observable operator Amplitude attenuation during long-distance transmission The intermediate signal light obtained after long-distance transmission is times that of the original signal light. .

[0038] According to embodiments of this disclosure, by simulating the transmission process of weak signals, the pre-selection signal light is attenuated, thereby enabling better coupling with the signal to be detected to obtain the intermediate signal light, thus realizing the real-time detection of weak time-varying signals.

[0039] After passing through the second beam splitter, the intermediate signal light is projected onto the first signal action unit and the second signal action unit. A reflector 180 can also be provided between the second beam splitter and the second signal action unit to reflect the second sub-signal light to the second signal action unit.

[0040] The first intermediate signal light enters the first post-selection sub-unit, which 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 intermediate signal light enters the second post-selection sub-unit, which 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. First and last choice state Second post-selection state It is in a nearly orthogonal range to the pre-selected state, where, , , For the first and last choice of angle, This is the second post-selection angle. After passing through the first post-selection sub-unit, the resulting first post-selection signal light is... After passing through the second post-selection sub-unit, the resulting second post-selection signal light is The intensity of the initial signal light can be expressed as: .

[0041] According to embodiments of this disclosure, the optical signals in the first and second post-selection subunits can be transmitted in free space, reducing signal errors caused by fiber vibration.

[0042] The first and second subsequent selection signal lights can also be represented as follows: and .

[0043] The first local oscillator beam and the first post-selected signal beam are mixed in the first quantum heterodyne detector to obtain the first beat frequency beam, the second beat frequency beam, the third beat frequency beam, and the fourth beat frequency beam. These are then detected by the first and second balanced photodetectors. The basic principle of heterodyne detection is the coherence of two light waves. The local oscillator beam is added simultaneously with the signal beam, and its frequency is very close to that of the signal beam, causing a beat frequency signal to form on the photosensitive surface of the photodetector. The detector then responds to the beat frequency signal, thereby detecting the modulation signal in the signal beam. A schematic diagram of the first quantum heterodyne detector, the first balanced photodetector, and the second balanced photodetector is shown below. Figure 3 As shown.

[0044] Figure 3 A schematic block diagram illustrating a first quantum heterodyne detector, a first balanced photodetector, and a second balanced photodetector according to embodiments of the present disclosure is shown.

[0045] like Figure 3 As shown, 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 detector 1533. The second balanced photodetector includes a third sub-detector 1541, a fourth sub-detector 1542, and a second differential detector 1543.

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

[0047] The first sub-detector 1531 is connected to the fifth beam splitter and configured to detect the first beat frequency light; the second sub-detector 1532 is connected to the fifth beam splitter and configured to detect the second beat frequency light; the first differential 1533 is connected to the first sub-detector 1531 and the second sub-detector 1532 and configured to perform differential analysis on the first beat frequency light and the second beat frequency light to obtain the first subheterodyne detection result.

[0048] The third sub-detector 1541 is connected to the sixth beam splitter and configured to detect the third beat frequency light; the fourth sub-detector 1542 is connected to the sixth beam splitter and configured to detect the fourth beat frequency light; the second differential 1543 is connected to the third sub-detector 1541 and the fourth sub-detector 1542 and configured to perform differential analysis on the third beat frequency light and the fourth beat frequency light to obtain the second subheterodyne detection result.

[0049] According to embodiments of this disclosure, the first post-selection signal light is split into a first sub-post-selection signal light and a second sub-post-selection signal light by a third beam splitter, and the first local oscillator light is split into a first sub-local oscillator light and a second local oscillator light by a fourth beam splitter. A first polarization controller performs polarization control on the first sub-local oscillator light to obtain a first sub-polarized light in a first phase state, and a second polarization controller performs polarization control on the second sub-local oscillator light to obtain a second sub-polarized light in a second phase state. The first polarization controller and the second polarization controller can be respectively configured as follows: and This ensures that the first and second sub-polarized beams are perpendicular to each other. The first sub-polarized beam and the first sub-selective signal beam pass through the fifth beam splitter, while the second sub-polarized beam and the second sub-selective signal beam pass through the sixth beam splitter, resulting in four beat frequency beams. The annihilation operators corresponding to the output optical field modes of the first, second, third, and fourth beat frequency beams are respectively... , , and , recorded as , , and Therefore, the light intensities received by the first, second, third, and fourth sub-detectors can be expressed as follows: , , and ,in , , and This corresponds to the generation operator; subsequently, through the first and second differencers, the first subheterodyne detection result is output. Second subheterodyne detection results Therefore, it is known that the light intensity output by the first balanced photodetector and the second balanced photodetector is... and .

[0050] According to embodiments of this disclosure, the second quantum heterodyne detector includes 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 includes a fifth sub-detector, a sixth sub-detector, and a third differential detector. The fourth balanced photodetector includes a seventh sub-detector, an eighth sub-detector, and a fourth differential detector.

[0051] According to embodiments of this disclosure, the second quantum heterodyne detector, the third balanced photodetector, and the fourth balanced photodetector have structures similar to the first quantum heterodyne detector, the first balanced photodetector, and the second balanced photodetector, which can be referred to... Figure 3 The description is not illustrated here.

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

[0053] The fifth sub-detector is connected to the ninth beam splitter and configured to detect the fifth beat frequency light; the sixth sub-detector is connected to the ninth beam splitter and configured to detect the sixth beat frequency light; the third differential is connected to the fifth and sixth sub-detectors and configured to perform differential analysis on the fifth and sixth beat frequency lights to obtain the third sub-heterodyne detection result.

[0054] The seventh sub-detector is connected to the tenth beam splitter and configured to detect the seventh beat frequency light; the eighth sub-detector is connected to the tenth beam splitter and configured to detect the eighth beat frequency light; the fourth differential is connected to the seventh and eighth sub-detectors and configured to perform differential analysis on the seventh and eighth beat frequency lights to obtain the fourth sub-heterodyne detection result.

[0055] According to embodiments of this disclosure, the second post-selection signal light is split into a third sub-post-selection signal light and a fourth sub-post-selection signal light by a seventh beam splitter, and the second local oscillator light is split into a third sub-local oscillator light and a fourth sub-local oscillator light by an eighth beam splitter. A third polarization controller performs polarization control on the third sub-local oscillator light to obtain a third sub-polarized light in a third phase state, and a fourth polarization controller performs polarization control on the fourth sub-local oscillator light to obtain a fourth sub-polarized light in a fourth phase state. The third and fourth polarization controllers can be respectively configured as follows: and This ensures that the third and fourth sub-polarized beams are perpendicular to each other. The third sub-polarized beam and the third sub-selective signal beam pass through the ninth beam splitter, and the fourth sub-polarized beam and the fourth sub-selective signal beam pass through the tenth beam splitter, resulting in four beat frequency beams. The annihilation operators corresponding to the output optical field modes of the fifth, sixth, seventh, and eighth beat frequency beams are respectively... , , and They are respectively denoted as , , and Therefore, the light intensities received by the fifth, sixth, seventh, and eighth sub-detectors can be expressed as follows: , , and ,in and This corresponds to the generation operator; subsequently, through the third and fourth differential circuits, the third subheterodyne detection result is output. and the results of the fourth subheterodyne detection Therefore, it is known that the light intensity output by the third and fourth balanced photodetectors is... and .

[0056] According to embodiments of this disclosure, by combining weak measurement technology with heterodyne detection, the fundamental limitation of light intensity attenuation caused by the near-orthogonal before-and-after selection states in previous weak measurement systems is effectively overcome.

[0057] According to embodiments of this disclosure, the signal processing unit can be configured to acquire a first sum of squared light intensity of a first subheterodyne detection result and a second sum of squared light intensity of a third subheterodyne detection result and a fourth subheterodyne detection result; obtain the phase change of the signal to be detected during transmission based on the first sum of squared light intensity and the second sum of squared light intensity; and obtain the phase of the detection signal based on the phase change.

[0058] The results of the first, second, third, and fourth subheterodyne detections are input to the signal processing unit. A sum-of-squares operation is performed on the first and second subheterodyne detection results to obtain the first sum of squares of light intensity, which is expressed as... The sum of squares of the third and fourth subheterodyne detection results is performed to obtain the second sum of squares of light intensity, which is expressed as follows: .

[0059] Under the condition of weak measurement and Below, the sum of squares of the first and second light intensities can be approximated as follows: , ,in , , It represents the imaginary part of a complex number.

[0060] According to embodiments of this disclosure, ideally, the phase change caused by the signal to be detected during long-distance transmission is: Therefore, the phase of the probe signal .

[0061] In actual implementation, due to back selection angle adjustment errors and device errors, the optical power of the two signal beams will attenuate differently. Therefore, the signal processing unit is further configured to: obtain a first attenuation coefficient of the first sum of squares of light intensity and a second attenuation coefficient of the second sum of squares of light intensity; obtain a first back selection angle adjustment error corresponding to the first back selection angle and a second back selection angle adjustment error corresponding to the second back selection angle; determine the light intensity compensation coefficient based on 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; perform light intensity compensation on the first sum of squares of light intensity based on the light intensity compensation coefficient to obtain the compensated sum of squares of light intensity; obtain the compensated phase change of the signal to be detected during transmission based on the compensated sum of squares of light intensity and the second sum of squares of light intensity; and calculate the compensated phase of the signal to be detected based on the compensated phase change.

[0062] According to embodiments of this disclosure, the first attenuation coefficient of the first sum of squares of the first light intensity is: Then the sum of squares of the first light intensity, after considering transmission attenuation, is: Let the second attenuation coefficient of the second sum of squares of the second light intensity be . Then the sum of squares of the second light intensity, after considering transmission attenuation, is: ,in, and It is the error in adjusting the first and second rear selection angles. , The relative change caused by the signal to be detected during long-distance transmission is: This indicates the presence of an additional bias, and the amplification factor also has an error.

[0063] Therefore, light intensity compensation can be used for optimization. Specifically, the light intensity compensation coefficient is determined based on the first attenuation coefficient, the second attenuation coefficient, the first post-selection angle, the second post-selection angle, the adjustment error of the first post-selection angle, and the adjustment error of the second post-selection angle. By applying light intensity compensation to the first sum of squared light intensities based on the light intensity compensation coefficient, the first sum of squared light intensities can be... Multiplying by the light intensity compensation coefficient, the relative change caused by the detected signal during long-distance transmission in this case is expressed as: Eliminating additional polarization, the amplification factor from Become Subsequently, the phase of the signal to be detected is calculated.

[0064] According to embodiments of this disclosure, since light intensity attenuation is taken into account, light intensity compensation is introduced, and only the light intensity of one path needs to be compensated, eliminating the strict requirement of symmetry between the two subsequent selection paths in a dual-path weak measurement system, and further improving the detection accuracy.

[0065] Figure 4 A flowchart illustrating a long-range weak signal detection method based on weak measurement techniques enhanced according to an embodiment of the present disclosure is shown.

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

[0067] When operating S410, an initial signal light is provided using a light source.

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

[0069] When operating the S430, the long-distance signal transmission simulation unit modulates the signal light into a pre-selection signal light, and under the action of the signal to be detected, the pre-selection signal light is transmitted over a preset distance to obtain the intermediate signal light.

[0070] In operation of S440, the intermediate signal light is split into a first sub-intermediate signal light and a second sub-intermediate signal light using the second beam splitter.

[0071] In operation S450, the first signal action unit modulates the first sub-intermediate signal light into the first post-selection signal light according to the first post-selection angle, and performs heterodyne detection with the first local oscillator light to obtain the first heterodyne detection result.

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

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

[0074] The system includes a first beam splitter connected to a light source, a long-distance signal transmission simulation unit connected to the first beam splitter, a second beam splitter connected to the long-distance signal transmission simulation unit, a first signal processing unit connected to both the first and second beam splitters, a first back selection angle and a second back selection angle that are opposites of each other, a second signal processing unit connected to both the first and second beam splitters, and a signal processing unit connected to both the first and second signal processing units.

[0075] According to the embodiments of this disclosure, operations S410 to S470 can be described with reference to the descriptions of other embodiments of this disclosure, and will not be repeated here.

[0076] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion 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 indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features described in the various embodiments of the present disclosure can be combined and / or combined in various ways, even if such combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments of this disclosure may be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0077] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A long-range weak signal detection system based on weak measurement technology, comprising: The light source is configured to provide initial signal light; A first beam splitter, connected to the light source, is configured to split the initial signal light into a first local oscillator beam, a second local oscillator beam, and a signal light; A long-distance signal transmission simulation unit is connected to the first beam splitter and configured to modulate the signal light into a pre-selection signal light. Under the action of the signal to be detected, the pre-selection signal light is transmitted over a preset distance to obtain an intermediate signal light, wherein the light intensity of the intermediate signal light is less than the light intensity of the signal light. The second beam splitter is connected to the long-distance signal transmission analog unit and is configured to split the intermediate signal light into a first sub-intermediate signal light and a second sub-intermediate signal light. The first signal processing unit is connected to the first beam splitter and the second beam splitter respectively, and is configured to modulate the first sub-intermediate signal light into the first post-selection 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; The second signal processing unit is connected to the first beam splitter and the second beam splitter 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 oscillator light to obtain the second heterodyne detection result, wherein the first post-selection angle and the second post-selection angle are opposite numbers to each other; The signal processing unit is connected to the first signal processing unit and the second signal processing unit respectively, and is configured to obtain the phase of the signal to be detected based on 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, is configured to attenuate the signal light to obtain attenuated signal light in a coherent state; A front selection subunit, connected to the optical attenuator, is configured to modulate the attenuated signal light into the front selection signal light according to the 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: The first post-selection subunit is connected to the second beam splitter and is configured to modulate the first sub-intermediate signal light into the first post-selection signal light according to the first post-selection angle. The first quantum heterodyne detector is connected to the first beam splitter and the first post-selection subunit, respectively, and is configured to mix the first post-selection signal light and the first local oscillator light to obtain the first beat frequency light, the second beat frequency light, the third beat frequency light and the fourth beat frequency light. A first balanced photodetector is connected to the first quantum heterodyne detector and is configured to perform differential analysis on the first beat frequency light and the second beat frequency light to obtain a first subheterodyne detection result, wherein the first subheterodyne detection result characterizes the detection result of the first local oscillator light in a first phase state; The second balanced photodetector is connected to the first quantum heterodyne detector and is configured to perform differential detection on the third beat frequency light and the fourth beat frequency light to obtain a second subheterodyne detection result, wherein the second subheterodyne detection result characterizes the 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 includes: The third beam splitter is connected to the first post-selection subunit and is 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. The fourth beam splitter, connected to the first beam splitter, is configured to split the first local oscillator beam into a first sub-local oscillator beam and a second sub-local oscillator beam; A first polarization controller is connected to the fourth beam splitter and is configured to perform polarization control on the first sub-local oscillator light to obtain the first sub-polarized light in the first phase state. The second polarization controller is connected to the fourth beam splitter and is configured to perform polarization control on the second sub-local oscillator light to obtain the 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. The fifth beam splitter, connected to the third beam splitter and the first polarization controller, is configured to split the first sub-selective signal light and the first sub-polarized light into the first beat frequency light and the second beat frequency light; The sixth beam splitter, connected to the third beam splitter and the second polarization controller, is configured to split the second sub-selective 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: The second post-selection subunit is connected to the second beam splitter 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. The second quantum heterodyne detector is connected to the second beam splitter and the second post-selection sub-unit, respectively, and is configured to mix the second post-selection signal light and the second local oscillator 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 is connected to the second quantum heterodyne detector and is configured to perform differential analysis on the fifth beat frequency light and the sixth beat frequency light to obtain the third subheterodyne detection result, wherein the third subheterodyne detection result characterizes the detection result of the second local oscillator light in the third phase state; A fourth balanced photodetector, connected to the second quantum heterodyne detector, is configured to perform differential analysis on the seventh beat frequency light and the eighth beat frequency light to obtain a fourth sub-heterodyne detection result, wherein the fourth sub-heterodyne detection result characterizes the detection result of the second local oscillator light in the fourth phase state.

6. The detection system according to claim 5, wherein, The second quantum heterodyne detector includes: The seventh beam splitter, connected to the second post-selection subunit, is 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; The eighth beam splitter, connected to the first beam splitter, is configured to split the second local oscillator beam into a third sub-local oscillator beam and a fourth sub-local oscillator beam; The third polarization controller is connected to the eighth beam splitter and is configured to perform polarization control on the third sub-local oscillator light to obtain the third sub-polarized light in the third phase state. A fourth polarization controller, connected to the eighth beam splitter, is configured to perform polarization control on the fourth sub-local oscillator light to obtain the 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; The ninth beam splitter, connected to the seventh beam splitter and the third polarization controller, is configured to split the third sub-selective signal light and the third sub-polarized light into the fifth beat frequency light and the sixth beat frequency light; The tenth beam splitter, connected to the seventh beam splitter and the fourth polarization controller, is configured to split the fourth sub-selective 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: Obtain the first sum of squared light intensities of the first subheterodyne detection result and the second subheterodyne detection result; Obtain the second sum of squared light intensities of the third subheterodyne detection result and the fourth subheterodyne detection result; The phase change of the signal to be detected during transmission is obtained based on the sum of the squares of the first and second light intensities. The phase of the signal to be detected is obtained based on the phase change.

8. The detection system according to claim 7, wherein the signal processing unit is further configured as: The first sum of squared light intensities is compensated for using the light intensity compensation coefficient to obtain the compensated sum of squared light intensities. The amount of phase change compensated during the transmission of the signal to be detected is obtained based on the sum of squares of the compensated light intensity and the second sum of squares of the light intensity. The compensation phase of the signal to be detected is calculated based on the compensation phase change.

9. The detection system according to claim 8, wherein the signal processing unit is further configured as: Obtain the first attenuation coefficient of the first sum of squares of light intensity and the second attenuation coefficient of the second sum of squares of light intensity; Obtain the first back selection angle adjustment error corresponding to the first back selection angle and the second back selection angle adjustment error corresponding to the second back selection angle; The light intensity compensation coefficient is determined based on 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.

10. A long-range weak signal detection method based on weak measurement technology, comprising: The initial signal light is provided by a light source; The initial signal light is split into a first local oscillator light, a second local oscillator light, and a signal light using a first beam splitter, wherein the first beam splitter is connected to the light source; The signal light is modulated into a pre-selection signal light using a long-distance signal transmission simulation unit. Under the action of the signal to be detected, the pre-selection signal light is transmitted over a preset distance to obtain an intermediate signal light. The intensity of the intermediate signal light is less than that of the signal light. The long-distance signal transmission simulation unit is connected to the first beam splitter. The intermediate signal light is divided into a first sub-intermediate signal light and a second sub-intermediate signal light using a second beam splitter, wherein the second beam splitter is connected to the long-distance signal transmission analog unit; The first signal processing unit modulates the first sub-intermediate signal light into a first post-selection signal light according to the first post-selection angle, and performs heterodyne detection with the first local oscillator light to obtain the first heterodyne detection result. The first signal processing unit is connected to the first beam splitter and the second beam splitter respectively. The second signal action unit modulates the second sub-intermediate signal light into a second post-selection signal light according to the second post-selection angle, and performs heterodyne detection with the second local oscillator light to obtain the second heterodyne detection result. The first post-selection angle and the second post-selection angle are opposites of each other. The second signal action unit is connected to the first beam splitter and the second beam splitter respectively. The phase of the signal to be detected is calculated by the signal processing unit based on the first heterodyne detection result and the second heterodyne detection result. The signal processing unit is connected to the first signal processing unit and the second signal processing unit respectively.

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