Quantum interference lidar system and quantum interference method for wind field detection

Abstract

A quantum interference LiDAR system and quantum interference method for wind field detection, which belong to the technical field of LiDARs. The system comprises: a laser device (1), an echo photon processing assembly (100), a reference photon processing assembly (200), a beam splitter (7), an echo photon time-of-arrival determination assembly (300), a reference photon time-of-arrival determination assembly (400) and an upper computer (12). On the basis of the phase randomness of aerosol backscatter signals, phase information of echo photons is eliminated, and a single-photon detector having a large bandwidth and a polarizer are used to eliminate color and polarization information, thereby realizing high-order quantum erasure in which the distinguishability of the degrees of freedom such as frequency, phase and polarization is erased. On this basis, two identical photons undergo high signal-to-noise ratio HOM interference, and the wind speed of a wind field is obtained by means of inversion performed on the basis of the oscillation frequency of interference fringes. Moreover, by means of continuously increasing a cumulative time, ultra-long-distance wind field detection at an extremely low transmission power can be realized.

Description

A quantum interference lidar system and method for wind field detection

[0001] This application claims priority to Chinese patent application 202311339189.2 filed on October 17, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the field of laser radar technology, and in particular to a quantum interference laser radar system and method for wind field detection. Background Art

[0003] The discovery of Hong-Ou-Mandel (HOM) interference in 1987—the phenomenon in which identical photons arrive simultaneously at different inputs of a beam splitter and consistently emerge from the same output—marked the beginning of a new quantum era. This phenomenon, precisely quantum in nature, enabled the separation of classical physics from quantum physics. HOM interference is not only widely used in high-precision time measurement and photon indistinguishability measurements, but also has diverse applications in quantum information processing, including quantum computing, quantum key distribution, and quantum coherence tomography. Furthermore, HOM interference has inspired physicists to conduct extensive research on interparticle interference, such as that between electrons, atoms, and ions.

[0004] A necessary condition for HOM interference is that the two photons are identical in all dimensions. This means that an observer cannot determine the path information of the photons by using information such as their phase, color, and polarization. The concept of quantum erasure makes interference between independent photons originating from different sources possible. Quantum erasure involves erasing the path information carried by the photons, rendering them completely indistinguishable at the detector, thereby restoring the interference fringes. Existing work using quantum erasure has demonstrated interference between sunlight and a ground-based tunable quantum point source approximately 150,000,000 km apart. However, because the backscattering cross-section of soft targets is much smaller than that of hard targets, detection is more challenging. Therefore, existing HOM interferometry methods have been applied to hard target detection. Furthermore, for HOM interferometry, the phases of the two photons are correlated, requiring either a time delay to align them or a time difference small enough for the detector to eliminate phase indistinguishability in order to achieve the famous HOM "dip." Complex synchronization modules are required for situations where the two photons originate from different sources.

[0005] In view of this, the present invention is proposed.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to provide a quantum interference lidar system and method for wind field detection, which does not require a synchronization module, is not affected by electromagnetic interference, has good stability, and can achieve ultra-long-distance wind field detection at extremely low transmission power, thereby solving the above-mentioned technical problems existing in the prior art.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A quantum interference laser radar system for wind field detection includes: a laser, an echo photon processing component, a reference photon processing component, a beam splitter, an echo photon arrival time determination component, a reference photon arrival time determination component and a host computer; wherein,

[0010] The laser is respectively provided with a pulse light output end and a continuous light output end;

[0011] The beam splitter is respectively provided with a first photon incident end, a second photon incident end, a first split photon output end and a second split photon output end;

[0012] The pulse light output end of the laser is connected to the pulse light input end of the echo photon processing component, so that the output pulse light can be emitted into the atmosphere through the echo photon processing component;

[0013] The echo photon processing component is connected to the first photon incident end of the beam splitter, can receive the aerosol backscattering signal of the pulse light in the atmosphere, and output the received aerosol backscattering signal as an echo photon to the beam splitter after polarization processing;

[0014] The continuous light output end of the laser is connected to the second photon incident end of the beam splitter in turn through the reference photon processing component, and the output continuous light can be output to the beam splitter as a local reference photon with a polarization direction consistent with the echo photon after attenuation and polarization processing;

[0015] The echo photons in the beam splitter undergo HOM interference with the local reference photons;

[0016] The first split photon output end of the beam splitter is communicatively connected to the host computer via the echo photon arrival time determination component;

[0017] The second split photon output end of the beam splitter is communicatively connected to the host computer via the reference photon arrival time determination component;

[0018] The upper computer can calculate the normalized coincidence count based on the arrival time of the echo photon determined by the echo photon arrival time determination component and the arrival time of the local reference photon determined by the reference photon arrival time determination component to obtain the HOM interference fringes, extract the Doppler frequency shift from the HOM interference fringes, and invert the Doppler frequency shift to calculate the wind speed of the measured wind field.

[0019] A quantum interference method for wind field detection, using the quantum interference lidar system of the present invention, comprises the following steps:

[0020] Step S1, pulsed light emitted by the laser of the system is emitted into the atmosphere through the echo photon processing component of the system, the echo photon processing component receives aerosol backscattering signals in the atmosphere, and polarizes the aerosol backscattering signals received by the pulsed light and outputs them as echo photons to the beam splitter of the system;

[0021] Step S2, the continuous light emitted by the laser of the system is attenuated and polarized by the reference photon processing component of the system and then output to the beam splitter as a local reference photon with the same polarization direction as the echo photon;

[0022] Step S3, the obtained echo photon and the local reference photon undergo HOM interference in the beam splitter;

[0023] Step S4, obtaining the arrival time of the echo photon by the echo photon arrival time determination component of the system, and obtaining the arrival time of the local reference photon by the reference photon arrival time determination component of the system, and recording the arrival time of the two identical echo photons and the local reference photon by the host computer of the system;

[0024] Step S5, the host computer calculates the normalized coincidence count according to the arrival time of the two photons to obtain HOM interference fringes, extracts the Doppler shift from the HOM interference fringes, and inverts the Doppler shift to calculate the wind speed of the measured wind field.

[0025] Compared with the prior art, the quantum interference lidar system and method for wind field detection provided by the present invention have the following beneficial effects:

[0026] The present invention erases the phase information of the echo photons based on the phase randomness of the aerosol backscattering signal of pulsed light, and adopts an echo photon processing component and a reference photon processing component that can perform polarization processing to make the polarization direction of the echo photons consistent with that of the local reference photons. At the same time, the echo photon arrival time determination component and the reference photon arrival time determination component are respectively used to perform color erasure processing on the echo photons and the local reference photons, realizing high-order quantum erasure that erases the distinguishability of frequency, phase, and polarization degrees of freedom. On this basis, two identical echo photons are obtained and undergo HOM interference with the local reference photon with a high signal-to-noise ratio. The Doppler frequency shift information can be extracted from the HOM interference fringes, thereby inverting the wind speed of the measured wind field, realizing a wind field detection method based on a quantum interference lidar system that is different from existing wind field detection methods. Since the phase randomness of the backscattered signal of aerosols in the atmosphere is utilized, the existing cumbersome phase tuning process can be omitted to achieve phase erasure. It does not require complex time tuning or synchronization circuits, which ensures detection accuracy while reducing the complexity of the system.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] FIG1 is a schematic diagram of the structure of a quantum interference lidar system for wind field detection provided by an embodiment of the present invention.

[0030] FIG2 is a flow chart of a quantum interference method for wind field detection provided by an embodiment of the present invention.

[0031] FIG3 is a specific flow chart of the quantum interference method for wind field detection provided by an embodiment of the present invention.

[0032] Modes for Carrying Out the Invention

[0033] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the specific content of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments, and do not constitute a limitation of the present invention. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] First, the following terms may be used in this article:

[0035] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y includes both “X” or “Y” and “X and Y”.

[0036] The terms "include," "comprises," "contains," "has," or other similar expressions should be interpreted as non-exclusive. For example, "including certain technical features (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products, or manufactured articles, etc.) should be interpreted as including not only the technical features explicitly listed, but also other technical features known in the art that are not explicitly listed.

[0037] The term "consisting of" excludes any technical features not explicitly listed. If used in a claim, this term renders the claim closed, excluding any technical features other than those explicitly listed, except for conventional impurities associated with them. If this term appears only in a clause of a claim, it limits only the elements explicitly listed in that clause; elements listed in other clauses are not excluded from the claim as a whole.

[0038] Unless otherwise specified or limited, the terms "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this document based on specific circumstances.

[0039] When concentration, temperature, pressure, size or other parameters are expressed in the form of a numerical range, the numerical range should be understood to specifically disclose all ranges formed by the pairing of any upper limit, lower limit, or preferred value within the numerical range, regardless of whether the range is explicitly stated. For example, if a numerical range of "2 to 8" is stated, the numerical range should be interpreted as including ranges of "2 to 7," "2 to 6," "5 to 7," "3 to 4 and 6 to 7," "3 to 5 and 7," "2 and 5 to 7," etc. Unless otherwise specified, the numerical ranges stated herein include both their endpoints and all integers and fractions within the numerical range.

[0040] The following is a detailed description of the quantum interference lidar system and method for wind field detection provided by the present invention. Any content not described in detail in the embodiments of the present invention belongs to the prior art known to professionals in this field. Where specific conditions are not specified in the embodiments of the present invention, the conditions are conventional in the art or the conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of the present invention, where the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0041] As shown in FIG1 , an embodiment of the present invention provides a quantum interference lidar system for wind field detection, comprising: a laser 1, an echo photon processing component 100, a reference photon processing component 200, a beam splitter 7, an echo photon arrival time determination component 300, a reference photon arrival time determination component 400, and a host computer 12; wherein,

[0042] The laser 1 is provided with a pulse light output end and a continuous light output end;

[0043] The beam splitter 7 is respectively provided with a first photon incident end, a second photon incident end, a first split photon output end and a second split photon output end;

[0044] The pulse light output end of the laser 1 is connected to the pulse light input end of the echo photon processing component 100, so that the output pulse light can be emitted into the atmosphere through the echo photon processing component 100;

[0045] The echo photon processing component 100 is connected to the first photon incident end of the beam splitter 7, and can receive the aerosol backscattering signal in the atmosphere, and output the received aerosol backscattering signal as echo light to the beam splitter 7 after performing polarization erasure.

[0046] The continuous light output end of the laser 1 is connected to the second photon incident end of the beam splitter 7 via the reference photon processing component 200, and the output continuous light can be output to the beam splitter 7 as a local reference light after attenuation and polarization;

[0047] The echo photons in the beam splitter 7 undergo HOM interference with the local reference photons;

[0048] The first split photon output end of the beam splitter 7 is connected to the host computer 12 via the echo photon arrival time determination component 300;

[0049] The second split photon output end of the beam splitter 7 is connected to the host computer 12 via the reference photon arrival time determination component 400;

[0050] The host computer 12 can calculate the normalized coincidence count based on the arrival times of the echo photons determined by the echo photon arrival time determination component and the local reference photons determined by the reference photon arrival time determination component, obtain HOM interference fringes, extract the Doppler frequency shift from the HOM interference fringes, and invert the Doppler frequency shift to calculate the wind speed of the measured wind field.

[0051] Preferably, in the above system, the echo photon processing component 100 includes:

[0052] circulator 2, telescope 3 and first polarizer 4; wherein,

[0053] The circulator 2 is provided with a pulse light input end, a bidirectional port and an echo photon output end, respectively. The pulse light input end is connected to the pulse light output end of the laser 1, the bidirectional port is connected to the telescope 3, and the echo photon output end is connected to the first photon incident end of the beam splitter 7 via the first polarizer 4;

[0054] The telescope 3 can receive aerosol backscatter signals of pulsed light in the atmosphere and output the received aerosol backscatter signals to the circulator 2;

[0055] The first polarizer 4 can perform polarization processing on the aerosol backscattering signal output by the circulator 2 and output the signal as an echo photon to the beam splitter 7 .

[0056] Preferably, in the above system, the reference photon processing component 200 includes:

[0057] Attenuator 5 and second polarizer 6; wherein,

[0058] The attenuator 5 is connected to the continuous light output end of the laser 1 and can attenuate the continuous light output by the laser 1;

[0059] The second polarizer 6 is connected between the attenuator 5 and the second photon incident end of the beam splitter 7 , and can perform polarization processing on the continuous light attenuated by the attenuator 5 and output the polarization light to the beam splitter 7 as a local reference light.

[0060] Preferably, the polarization directions of the first polarizer 4 and the second polarizer 6 are consistent. That is, the polarization direction of the echo photons polarized by the first polarizer 4 is consistent with the polarization direction of the local reference photons polarized by the second polarizer 6.

[0061] Preferably, in the above system, the echo photon arrival time determination component 300 includes:

[0062] A first single photon detector 8 and a first time-to-digital converter 10 are connected in sequence; wherein,

[0063] The first single-photon detector 8 is connected to the first split photon output end of the beam splitter 7 and can output echo photons after color erasing the echo photons output by the beam splitter 7;

[0064] The first time-to-digital converter 10 can obtain the arrival time of the echo photon;

[0065] The reference photon arrival time determination component 400 includes:

[0066] The second single photon detector 9 and the second time-to-digital converter 11 are connected in sequence; wherein,

[0067] The second single-photon detector 9 is connected to the second split photon output end of the beam splitter 7, and can perform color erasing on the local reference photons output by the beam splitter 7 and then output the local reference photons;

[0068] The second time-to-digital converter 11 can obtain the arrival time of the local reference photon.

[0069] The bandwidth of the first single-photon detector 8 and the bandwidth of the second single-photon detector 9 are both greater than the frequency difference between the echo photon and the local reference photon. This bandwidth can meet the requirements for photon color erasure.

[0070] Preferably, in the above system, the host computer 12 calculates the normalized coincidence count according to the arrival time of the echo photon determined by the echo photon arrival time determination component and the arrival time of the local reference photon determined by the reference photon arrival time determination component to obtain the HOM interference fringes, and extracts the Doppler shift from the HOM interference fringes in the following manner, including:

[0071] The normalized coincidence count of the arrival times of the two photons is calculated, the obtained normalized coincidence count is Fourier transformed to obtain the oscillation frequency of the HOM interference fringes, the Doppler shift is extracted from the oscillation frequency, and the wind speed of the measured wind field is calculated by inversion of the Doppler shift.

[0072] As shown in FIG2 , an embodiment of the present invention further provides a quantum interference method for wind field detection, which uses the above-mentioned quantum interference lidar system and includes the following steps:

[0073] Step S1: The pulsed light emitted by the laser 1 of the system is emitted into the atmosphere through the echo photon processing component 100 of the system. The echo photon processing component receives the aerosol backscattered signal in the atmosphere, performs polarization processing on the received aerosol backscattered signal, and outputs it as an echo photon to the beam splitter 7 of the system;

[0074] Step S2, the continuous light emitted by the laser 1 of the system is attenuated and polarized by the reference photon processing component 200 of the system and then output to the beam splitter 7 as a local reference photon;

[0075] Step S3, the obtained echo photons and the local reference photons undergo HOM interference in the beam splitter 7;

[0076] Step S4, obtaining the arrival time of the echo photon by the echo photon arrival time determination component 300 of the system, and obtaining the arrival time of the local reference photon by the reference photon arrival time determination component 400 of the system, and recording the arrival times of the two identical echo photons and the local reference photon by the host computer 12 of the system;

[0077] Step S5: The host computer 12 calculates the coincidence count based on the arrival time of the two photons to obtain HOM interference fringes, extracts Doppler frequency shift from the HOM interference fringes, and inverts the Doppler frequency shift to calculate the wind speed of the measured wind field.

[0078] Preferably, in step S1 of the above method, the circulator 2 of the echo photon processing component 100 outputs the pulse light output by the laser 1 to the telescope 3 of the echo photon processing component 100, and the telescope 3 emits the pulse light into the atmosphere, and receives the aerosol backscattering signal in the atmosphere and outputs it to the circulator 2, and the circulator 2 sends the aerosol backscattering signal into the first polarizer 4 of the echo photon processing component, and the first polarizer 4 performs polarization erasing on the aerosol backscattering signal and outputs it as echo light to the beam splitter 7.

[0079] Preferably, in step S2 of the above method, the continuous light emitted by the laser 1 is attenuated by the attenuator 5 of the reference photon processing component 200 and then polarized by the second polarizer before being output to the beam splitter 7 as the local reference light.

[0080] Preferably, in step S3 of the above method, the obtained echo light and the local reference light undergo HOM interference with a high signal-to-noise ratio in the beam splitter 7 to form HOM interference fringes.

[0081] Preferably, in step S4 of the above method, the echo light outputted after the beam splitter 7 is split enters the first single-photon detector 8 of the echo photon arrival time determination component 300 to obtain the echo photon, and the echo photon enters the first time-to-digital converter 10 of the echo photon arrival time determination component 300 to determine the arrival time of the echo photon;

[0082] The reference light output after splitting by the beam splitter 7 enters the second single-photon detector 9 of the reference photon arrival time determination component 400 to obtain the echo photon, and the reference photon enters the second time-to-digital converter 11 of the reference photon arrival time determination component 400 to determine the arrival time of the reference photon.

[0083] Preferably, in step S5 of the above method, the oscillation frequency of the HOM interference fringes of the two photons is calculated based on the arrival time of the two photons in the following manner, including:

[0084] Step S51, the arrival time of each photon is divided into segments according to the accumulated time and the range gate;

[0085] Step S52, calculating a normalized coincidence count based on each segment obtained by segmentation;

[0086] Step S53, the oscillation frequency of the normalized coincidence count is used as the oscillation frequency of the HOM interference fringes;

[0087] Step S54 , extracting the Doppler frequency shift from the oscillation frequency, and calculating the wind speed of the measured wind field by inverting the Doppler frequency shift.

[0088] In summary, in the system and method of the embodiments of the present invention, since the echo photon arrival time determination component and the reference photon arrival time determination component both use single-photon detectors, and single-photon detectors have essentially no circuit noise, it is easier to reach the shot noise limit. Furthermore, the present invention can improve the signal-to-noise ratio (SNR) by continuously increasing the accumulation time, thereby achieving ultra-long-range detection. Furthermore, the present invention only records the arrival time of photons, reducing the difficulty of data storage and processing, making it possible to achieve all-fiber signal processing. Furthermore, the present invention does not require filters and frequency discriminators, and the entire detection process is purely digital and single-photon, free from electromagnetic interference, and has excellent stability. The system has a streamlined structure and low transmission power, and is therefore also expected to be used for satellite-borne detection.

[0089] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the quantum interference lidar system and method for wind field detection provided by the embodiments of the present invention are described in detail below with specific embodiments.

[0090] Example 1

[0091] This embodiment provides a quantum interference lidar system for wind field detection. The system schematic diagram is shown in FIG1 , including: a laser 1, a circulator 2, a telescope 3, a first polarizer 4, an attenuator 5, a second polarizer 6, a beam splitter 7, a first single-photon detector 8, a second single-photon detector 9, a first time-to-digital converter 10, a second time-to-digital converter 11, and a host computer 12; wherein,

[0092] The circulator 2, the telescope 3 and the first polarizer 4 constitute the echo photon processing assembly 100;

[0093] The attenuator 5 and the second polarizer 6 form a reference photon processing component 200;

[0094] The first single photon detector 8 and the first time-to-digital converter 10 form an echo photon arrival time determination component 300;

[0095] The second single photon detector 9 and the second time-to-digital converter 11 constitute a reference photon arrival time determination component 400 .

[0096] To ensure the detection effect, the bandwidth of the first single-photon detector 8 and the second single-photon detector 9 are both greater than the frequency difference between the echo photon and the local reference photon.

[0097] Among them, the laser 1 generates two optical signals, one is pulsed light and the other is continuous light. In this embodiment, the preferred operating wavelength of the laser 1 is 1548.5nm; the pulsed light is emitted into the atmosphere by the telescope 3 through the circulator 2, and then the telescope 3 receives the aerosol backscattered signal of the pulsed light in the atmosphere; the received aerosol backscattered signal enters the first polarizer 4 through the circulator 3 for polarization processing, and then enters the beam splitter 7 as an echo photon; the other continuous light output by the laser 1 is attenuated by the attenuator 5 and enters the second polarizer 6 for polarization processing, and then enters the beam splitter 7 as a local reference photon. The echo photon polarized by the first polarizer 4 and the local reference light polarized by the second polarizer 6 are incident on the beam splitter 7. The polarization directions of the photons are consistent, eliminating the difference in polarization directions. Since the aerosol backscattering signal of the pulsed light has phase randomness, that is, no complex time tuning or synchronization circuit is required, this feature is used to eliminate the phase information of the echo photons. Since the polarization difference of the two photons is also eliminated after polarization, HOM interference can be formed in the beam splitter 7; the two photons output by the beam splitter 7 are detected by the first single-photon detector 8 and the second single-photon detector 9 respectively, and then enter the first time digital converter 10 and the second time digital converter 11 respectively to detect the arrival time of the two photons; finally, the arrival time of the two photons output by the two time digital converters enters the host computer 12 for data processing and calculation to obtain the wind speed of the measured wind field. Specifically, the host computer 12 divides the arrival time of each photon into segments according to the accumulated time and the range gate, calculates the normalized coincidence count based on each segment, uses the oscillation frequency of the normalized coincidence count as the oscillation frequency of the HOM interference fringe, extracts the Doppler frequency shift from the oscillation frequency, and inverts the Doppler frequency shift to calculate the wind speed of the measured wind field.

[0098] Example 2

[0099] This embodiment provides a quantum interference method for wind field detection, which adopts the quantum interference lidar system of embodiment 1. The process of this method is shown in Figures 2 and 3. First, the pulse light generated by the laser is emitted into the atmosphere through a telescope and the aerosol backscattered signal of the received pulse light is polarized and processed as an echo photon. The other continuous light is attenuated into a single photon by an attenuator and then polarized so that its polarization direction is consistent with the echo photon as a local reference photon; the phase randomness of the aerosol backscattered signal is used to eliminate the phase information of the echo photon; the polarization information of the echo photon and the local reference photon is eliminated by two polarizers. Then, the photons of the two paths enter the beam splitter, and the photons output by the beam splitter are detected by two single-photon detectors respectively. Since the bandwidth of the single-photon detector used is greater than the frequency difference between the echo photon and the local reference photon, for the detector, there is no frequency distinction between the echo photon and the local reference photon, thereby achieving color erasure. After the detector, a time-to-digital converter records the arrival times of the two photons. After traversing and segmenting the arrival times of the two photons, the coincidence counts of the two data streams are calculated. The Doppler shift information is then extracted from this data to invert the wind speed. Because this process achieves high-order quantum erasure, in which all degrees of freedom are erased, HOM interference fringes with a high signal-to-noise ratio are obtained, enabling ultra-long-range and ultra-precise wind field detection.

[0100] The HOM interference involved in the method of this embodiment refers to the phenomenon that two identical photons arrive at different input ends of a beam splitter at the same time and always exit from the same output end. Taking the polarization state as an example, for a 50:50 beam splitter, if two photons with the same polarization state are incident simultaneously from ends a and b of the beam splitter (end a is the first photon incident end, and end b is the second photon incident end), then the output state can be expressed as:

[0101] in, represents the photon generation operator for quantum states a, b, c, and d with horizontal (vertical) polarization; |0> represents the vacuum state. This output state indicates that when two indistinguishable photons are incident simultaneously from terminals a and b of the beam splitter, they will only be emitted together from terminals c or d. If two single-photon detectors are placed at the two output terminals to simultaneously detect the photon output signals, the coincidence count of the simultaneous detection of photons is zero, which is known as the "HOM dip."

[0102] [Corrected 13.11.2023 according to Rule 91] If the polarization states of the incident photons are perpendicular to each other, the output state can be expressed as:

[0103] This output state indicates that when two distinguishable photons are incident from the a and b ends of the beam splitter at the same time, the two photons will be emitted from the c or d end together (the c end is the output end of the first beam split photon, and the d end is the output end of the second beam split photon), or one photon will be emitted from the c end and the other from the d end, which is the same as the classical situation.

[0104] The above formula also shows that HOM interference only occurs when the two photons are completely indistinguishable. The stronger the indistinguishability of the photons, the higher the visibility of the HOM interference. The visibility V is defined as:

[0105] Among them, C max , C min are the maximum and minimum values ​​of coincidence counts, respectively. If both photons are in the single-photon state, the visibility limit is 1. The closer the visibility is to 1, the better the indistinguishability of the photons. For the case where both photons are in a coherent state, the visibility limit is 0.5. The present invention can achieve HOM interference close to the visibility limit by performing high-order quantum erasure in which all degrees of freedom, such as color, phase, and polarization, of the echo photons and the local reference photons are erased. High visibility means good interference fringe contrast, so a good signal-to-noise ratio can be obtained, thereby providing an accurate basis for detecting the wind speed in the wind field.

[0106] Next, to obtain a wind field distribution with temporal and spatial resolution, the present invention uses different time-to-digital converters to record the arrival times of each photon. The photon arrival times are then traversed and segmented according to the cumulative time and range gate. For each segment, the normalized coincidence count g(τ) is calculated using the following formula:

[0107] Where ncoincidence is the coincidence count of photons detected by both single-photon detectors; n bin is the total length of the data or the number of time windows; n1 and n2 are the total photon counts recorded by the first single-photon detector and the second single-photon detector, respectively.

[0108] Then, the Fourier transform of the coincidence count is calculated to obtain its spectrum distribution, and Gaussian fitting is performed on the spectrum distribution to obtain the peak frequency. The peak frequency is the Doppler shift caused by the measured wind field, and the Doppler shift is inverted to obtain the wind speed of the measured wind field.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A quantum interference laser radar system for wind field detection, characterized in that: include: A laser (1), an echo photon processing component (100), a reference photon processing component (200), a beam splitter (7), an echo photon arrival time determination component (300), a reference photon arrival time determination component (400) and a host computer (12); wherein: The laser (1) is respectively provided with a pulse light output end and a continuous light output end; The beam splitter (7) is respectively provided with a first photon incident end, a second photon incident end, a first split-beam photon output end and a second split-beam photon output end; The pulse light output end of the laser (1) is connected to the pulse light input end of the echo photon processing component (100), so that the output pulse light can be emitted into the atmosphere through the echo photon processing component (100); The echo photon processing component (100) is connected to the first photon incident end of the beam splitter (7), and is capable of receiving aerosol backscattering signals of pulsed light in the atmosphere, and outputting the received aerosol backscattering signals as echo photons to the beam splitter (7) after polarization processing; The continuous light output end of the laser (1) is connected to the second photon incident end of the beam splitter (7) in sequence through the reference photon processing component (200), and the output continuous light can be output to the beam splitter (7) as a local reference photon with a polarization direction consistent with the echo photon after attenuation and polarization processing; The echo photons in the beam splitter (7) undergo HOM interference with the local reference photons; The first split photon emission end of the beam splitter (7) is communicatively connected to the host computer (12) via the echo photon arrival time determination component (300); The second split photon output end of the beam splitter (7) is communicatively connected to the host computer (12) via the reference photon arrival time determination component (400); The host computer (12) can calculate the normalized coincidence count based on the arrival time of the echo photon determined by the echo photon arrival time determination component (300) and the arrival time of the local reference photon determined by the reference photon arrival time determination component (400) to obtain the HOM interference fringes, extract the Doppler frequency shift from the HOM interference fringes, and calculate the wind speed of the measured wind field by inverting the Doppler frequency shift.

2. The quantum interference laser radar system for wind field detection according to claim 1 is characterized in that: The echo photon processing component (100) comprises: A circulator (2), a telescope (3) and a first polarizer (4); wherein: The circulator (2) is respectively provided with a pulse light input end, a bidirectional port and an echo photon output end, the pulse light input end is connected to the pulse light output end of the laser (1), the bidirectional port is connected to the telescope (3), and the echo photon output end is connected to the first photon incident end of the beam splitter (7) via the first polarizer (4); The telescope (3) is capable of receiving aerosol backscatter signals in the atmosphere and outputting the received aerosol backscatter signals to the circulator (2); The first polarizer (4) can perform polarization processing on the aerosol backscattering signal output by the circulator (2) and output the signal as an echo photon to the beam splitter (7); The reference photon processing component (200) comprises: attenuator (5) and a second polarizer (6); wherein, The attenuator (5) is connected to the continuous light output end of the laser (1) and is capable of attenuating the continuous light output by the laser (1); The second polarizer (6) is connected between the attenuator (5) and the second photon incident end of the beam splitter (7), and can perform polarization processing on the continuous light attenuated by the attenuator (5) and output the polarization processed light as a local reference photon to the beam splitter (7).

3. The quantum interference laser radar system for wind field detection according to claim 2 is characterized in that: The polarization directions of the first polarizer (4) and the second polarizer (6) are consistent.

4. The quantum interference laser radar system for wind field detection according to any one of claims 1 to 3, characterized in that: The echo photon arrival time determination component (300) comprises: A first single-photon detector (8) and a first time-to-digital converter (10) are connected in sequence; wherein, The first single-photon detector (8) is connected to the first split-beam photon output end of the beam splitter (7), and can perform color erasing on the echo photons output by the beam splitter (7) and then output the echo photons; The first time-to-digital converter (10) can obtain the arrival time of the echo photon.

5. The quantum interference laser radar system for wind field detection according to claim 4 is characterized in that: The bandwidth of the first single photon detector (8) is greater than the frequency difference between the echo photon and the local reference photon.

6. The quantum interference laser radar system for wind field detection according to any one of claims 1 to 3, characterized in that: The reference photon arrival time determination component (400) comprises: A second single-photon detector (9) and a second time-to-digital converter (11) are connected in sequence; wherein, The second single-photon detector (9) is connected to the second split-beam photon output end of the beam splitter (7), and can perform color erasure on the local reference photons output by the beam splitter (7) and then output the local reference photons; The second time-to-digital converter (11) can obtain the arrival time of the local reference photon.

7. The quantum interference laser radar system for wind field detection according to claim 6 is characterized in that: The bandwidth of the second single photon detector (9) is greater than the frequency difference between the echo photon and the local reference photon.

8. The quantum interference laser radar system for wind field detection according to any one of claims 1 to 3, characterized in that: The host computer (12) calculates the normalized coincidence count according to the arrival time of the echo photon determined by the echo photon arrival time determination component and the arrival time of the local reference photon determined by the reference photon arrival time determination component to obtain the HOM interference fringes in the following manner, including: The normalized coincidence counts of the arrival times of the two photons are calculated, and the obtained normalized coincidence counts are transformed by Fourier transform to obtain the HOM interference fringes.

9. A quantum interference method for wind field detection, characterized in that: The quantum interference laser radar system according to any one of claims 1 to 8 comprises the following steps: Step S1, the pulse light emitted by the laser (1) of the system is emitted into the atmosphere through the echo photon processing component (100) of the system, the echo photon processing component (100) receives the aerosol backscattering signal of the pulse light in the atmosphere, and the received aerosol backscattering signal is polarized and then output as an echo photon to the beam splitter (7) of the system; Step S2, the continuous light emitted by the laser (1) of the system is attenuated and polarized by the reference photon processing component (200) of the system and then output to the beam splitter (7) as a local reference photon with the same polarization direction as the echo photon; Step S3, the obtained echo photons and the local reference photons undergo HOM interference in the beam splitter (7); Step S4, obtaining the arrival time of the echo photons through the echo photon arrival time determination component (300) of the system, and obtaining the arrival time of the local reference photons through the reference photon arrival time determination component (400) of the system, and recording the arrival times of the two identical echo photons and the local reference photons through the host computer (12) of the system; Step S5, the host computer (12) calculates the normalized coincidence count according to the arrival times of the two photons to obtain HOM interference fringes, extracts the Doppler frequency shift from the HOM interference fringes, and inverts the Doppler frequency shift to calculate the wind speed of the measured wind field.

10. The quantum interference method for wind field detection according to claim 9, characterized in that: In step S5, the normalized coincidence count is calculated according to the arrival time of the two photons to obtain HOM interference fringes, the Doppler frequency shift is extracted from the HOM interference fringes, and the wind speed of the measured wind field is calculated by inversion of the Doppler frequency shift, including: Step S51, the arrival time of each photon is divided into segments according to the accumulated time and the range gate; Step S52, calculating a normalized coincidence count according to each segment obtained by segmentation; Step S53, the oscillation frequency of the normalized coincidence count is used as the oscillation frequency of the HOM interference fringes; Step S54: extracting the Doppler frequency shift from the oscillation frequency, and calculating the wind speed of the measured wind field by inverting the Doppler frequency shift.

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