A photon loss-resistant quantum radar device based on dual transmitters

Abstract

The present invention relates to the field of target detection and identification technology, and discloses a dual-transmitter photon loss-resistant quantum radar device, comprising a first transmitter, a second transmitter, a receiver, and a transceiver synchronization system. The first and second transmitters each include a quantum entangled light source, a signal collimation module, and a first single-photon detector. The receiver includes a quantum interference module and two second single-photon detectors. The first, second, and receivers achieve clock synchronization and real-time communication via the transceiver synchronization system. The present invention employs dual transmitters capable of generating quantum interference for target detection, resulting in better target detection performance than using two independent transmitters. This represents a new approach to improving target detection performance through multiple transmitter configurations.

Description

Technical Field

[0001] The present invention relates to the technical field of target detection and identification, and in particular to a photon loss-resistant quantum radar device based on dual transmitters. Background Art

[0002] Quantum radar is a new technology that uses quantum entanglement in quantum information to detect targets. Since its proposal, quantum radar has garnered widespread attention from numerous research institutions both domestically and internationally. Developing practical, loss-resistant quantum radar technology is crucial for its practical application.

[0003] In order to solve the problem of quantum radar's resistance to photon loss, this paper proposes a quantum radar solution based on dual transmitters that is resistant to photon loss. Through the interference of the echo signals of the dual transmitters, the signal receiving efficiency of the quantum radar can be effectively increased from η to This is very effective for target detection when η<<1. Taking η=0.0001 as an example, the efficiency will be improved to This represents a 100-fold improvement. This is extremely beneficial for target detection under extreme echo signal loss, and provides a solution for detecting dim targets under strong loss.

[0004] We also proposed a method for using photon anti-correlation statistics for the received echo signals, using the anti-photon correlation of the dual-transmitter signals as a test statistic, significantly improving the actual target detection performance. This loss-resistant quantum radar based on dual transmitters is particularly suitable for detecting small, slow, low-altitude targets whose longitudinal distance is significantly greater than the target's altitude. Therefore, this radar device has the potential to be used for the detection and identification of small, low-altitude targets. Summary of the Invention

[0005] The present invention aims to provide a photon loss-resistant quantum radar device based on dual transmitters, which can effectively overcome the quantum signal loss in the existing quantum target detection process, realize target information inversion through the photon anti-correlation signal inside the dual transmitters, and provide key technical support for the detection and identification of low, slow and small targets in the future.

[0006] In order to achieve the above-mentioned object, the basic scheme of the present invention is as follows: a photon loss-resistant quantum radar device based on dual transmitters includes a first transmitter, a second transmitter, a receiver and a transmitting and receiving synchronization system;

[0007] The first transmitter and the second transmitter each include a quantum entangled light source, a signal collimation module and a first single-photon detector;

[0008] The receiver includes a quantum interference module and two second single-photon detectors;

[0009] The first transmitter, the second transmitter and the receiver realize clock synchronization and real-time communication through a transceiver synchronization system.

[0010] Furthermore, the quantum entangled light source of the first transmitter completes the preparation of the two-mode quantum entangled state, and transmits one of the modes to the area to be measured through the signal collimation and transmission unit, and sends the other mode directly to the optical delay line for optical delay. The delayed quantum signal is sent to the first single-photon detector for detection. The first transmitter is equipped with a transceiver synchronization system A for clock synchronization with the receiver and the second transmitter.

[0011] Furthermore, the quantum entangled light source of the second transmitter completes the preparation of the two-mode quantum entangled state, and transmits one of the modes to the area to be measured through the signal collimation and transmission unit, and sends the other mode directly to the optical delay line for optical delay. The delayed quantum signal is sent to the first single-photon detector for detection. The second transmitter is equipped with a transceiver synchronization system B, which is used to synchronize the clock with the receiver and the first transmitter.

[0012] Furthermore, the receiver is used to interfere with the signals transmitted to the target and returned by the first transmitter and the second transmitter. The interference is performed on the quantum interference module. The interference results of the quantum interference module are detected by two second single-photon detectors. The receiver is provided with a transceiver synchronization system C for clock synchronization with the first transmitter, the second transmitter and the receiver.

[0013] Furthermore, the detection results of the first single-photon detector and the second single-photon detector are both submitted to the data screening unit.

[0014] Furthermore, the data identification unit forms photon counting statistics through the detection results of the first single-photon detector and the second photon detector, and compares them with a preset threshold to form a target determination result, thereby obtaining relevant information of the target.

[0015] 1. Principles and advantages of the basic solution: The present invention uses dual transmitters that can generate quantum interference for target detection, which has better target detection performance than two independent transmitters. It is a new idea to improve target detection performance from the perspective of multiple transmitter configurations.

[0016] 2. The present invention achieves target detection by exploiting the anticorrelation of photon counts from two single-photon detectors. This anticorrelation is induced by photon detection in the receiver. Furthermore, in most cases, the two anticorrelated measurements result in zero and one photon, respectively, meaning that the detector that measures zero photons has a lower detection efficiency requirement. This allows the dual-transmitter quantum radar device to maintain high performance even with low-efficiency single-photon detectors, resulting in enhanced device robustness.

[0017] 3. Due to the 0-1 photon interference adopted by quantum interference, there is at most one photon in the two interfering light paths, which is insensitive to light path loss, allowing the system to be The efficiency of target detection is improved by 10%. Compared with the known quantum radar with single transmitter and single receiver configuration, the performance of signal reception efficiency is improved by 10%. times, which is particularly beneficial for target detection under extreme loss.

[0018] 4. The present invention is particularly suitable for detecting targets whose longitudinal distance is much greater than the target height, and is especially suitable for detecting and identifying small, low, slow and distant targets.

[0019] 5. The present invention adopts dispersed placement of transmitters and receivers. The separation distance can be flexibly adjusted according to needs. The radar device has high concealment, maneuverability and battlefield attack resistance.

[0020] 6. This invention is based on the quantum interference of optical bands and photons. The principle of dual-transmitter quantum radar is also applicable to quantum radar in the microwave band. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the overall scheme diagram of the present invention;

[0022] Figure 2 Schematic diagram of transmitter 1, transmitter 2 and receiver according to embodiment 1 of the present invention;

[0023] Figure 3 This is a data processing flow chart of the data identification unit for target detection in the first embodiment of the present invention;

[0024] Figure 4 The threshold value N in the first embodiment of the present invention is th Flowchart of the setting calculation algorithm;

[0025] Figure 5 The variation trend of the anti-correlation probability with η in the first embodiment of the present invention, where η=10 -2 ~10 -4 ,κ=0.2,λ=0.2.

[0026] Figure 6 The variation trend of missed detection probability with η at different transmission times M in the first embodiment of the present invention, where η=10 -2 ~10 -4 ,κ=0.2,λ=0.2. The larger M is, the lower the missed detection probability is and the better the performance is.

[0027] Figure 7 The performance comparison between this scheme and the single transmitter scheme is shown in Figure 1, where η = 10 -2 ~10 -4,κ=0.2,λ=0.2,M=200000.

[0028] Figure 8 for Figure 7 Schematic diagram of the single-transmitter solution for performance comparison.

[0029] Figure 9 Schematic diagram of a transmitter and a receiver according to the second embodiment of the present invention.

[0030] Figure 10 Schematic diagram of the port markings of the optical beam splitters BS0, BS1, BS2, BS3, and BS4 according to the second embodiment of the present invention.

[0031] Figure 11 For different detection efficiencies η d Signal utilization rate of the dual-transmitter quantum radar scheme under the condition, where η=10 -2 ~10 -4 ,κ=0.2,λ=0.2. DETAILED DESCRIPTION

[0032] The following is further described in detail through specific implementation methods:

[0033] The present application provides a photon loss-resistant quantum radar device based on dual transmitters. Figure 1 As shown, it includes a first transmitter (transmitter 1), a second transmitter (transmitter 2), a receiver and a transceiver synchronization system.

[0034] Both the first transmitter and the second transmitter include a quantum entangled light source, a first single-photon detector and a signal collimation and emission unit. In this embodiment, the quantum entangled light source of the first transmitter is quantum entangled light source 1, the quantum entangled light source of the second transmitter is quantum entangled light source 2, the first single-photon detector of the first transmitter is single-photon detector 1, the first transmitter is equipped with a transceiver synchronization system A, the first single-photon detector of the second transmitter is single-photon detector 2, and the second transmitter is equipped with a transceiver synchronization system B.

[0035] The receiver includes a quantum interference module and two second single-photon detectors, which are single-photon detector 3 and single-photon detector 4 respectively, and is equipped with a transmitting and receiving synchronization system C.

[0036] The above-mentioned photon loss-resistant quantum radar device based on dual transmitters has the following implementation scheme:

[0037] Implementation Plan 1

[0038] As shown in Figure 2, in the first embodiment of the present invention, a quantum radar device based on dual transmitters is provided to resist photon loss. We further refine transmitter 1, transmitter 2, and receiver.

[0039] The quantum entangled light source 1 in the transmitter 1 emits the quantum entangled state Quantum entangled state |ψ> AB The A mode is sent to the optical delay line DL1. The optical delay line DL1 can be replaced by a section of low-loss optical fiber. Its function is to delay the time of photon detection to synchronize the detection time with the single-photon detectors D2, D3, and D4. AB The B mode is sent to the signal collimation and transmission unit. The signal collimation and transmission unit consists of collimating lens ZL1 and collimating lens ZL2. The one-way photon transmission efficiency on the line from transmitter 1 to the target to be measured is The reflectivity of the target is κ.

[0040] The quantum entangled light source 2 in transmitter 2 emits quantum entangled state Quantum entangled state |ψ> CD The D mode is sent to the optical delay line DL2. The optical delay line DL2 can be replaced by a section of low-loss optical fiber. Its function is to delay the time of photon detection to synchronize the detection time with the single-photon detectors D1, D3, and D4. The A mode of the quantum entangled state is sent to the signal collimation and emission unit. Among them, the signal collimation and emission unit consists of collimating lens ZL3 and collimating lens ZL4. The one-way photon transmission efficiency on the line from transmitter 2 to the target to be measured is The reflectivity of the target is κ.

[0041] It should be noted that traditional radars often use the method of sending and returning signals to detect targets, and the total channel utilization rate is The present invention adopts the method of quantum interference, and the final signal utilization rate will reach the efficiency of one-way photon transmission.

[0042] The receiver uses an optical beam splitter (BS) to achieve quantum interference. To maintain symmetry, a 50:50 optical beam splitter is used. The echo signal from transmitter 1 is connected to the first input terminal ① of the optical beam splitter (BS); the echo signal from transmitter 2 is connected to the second input terminal ② of the optical beam splitter (BS); the third output terminal ③ of the optical beam splitter (BS) is connected to the single-photon detector D3; and the fourth output terminal ④ of the optical beam splitter (BS) is connected to the single-photon detector D2.

[0043] The detection results of the four single-photon detectors D1, D2, D3 and D4 are connected to a data discrimination unit. The data discrimination unit can be implemented by a hardware comparison circuit or by a computer algorithm and software.

[0044] Flowchart as Figure 3 As shown. The dual-transmitter anti-photon loss quantum radar works in pulse mode. For each pulse, the data discrimination unit Figure 3 Then, by obtaining the photon statistics of M pulses, all the measured anti-correlation counts N are calculated. AC With threshold N th Compare and realize the detection of the target state. Specifically: for each pulse, the data discrimination unit first analyzes the detection results of the single-photon detectors D3 and D4 in the receiver. If D3 detects more than 0 photons, the current count is directly terminated. If D3 detects 1 photon, the number of photons detected by D4 is analyzed. If D4 detects 1 photon, the current count is directly terminated. If D4 detects 0 photons, the detection results of the single-photon detectors D1 and D2 are compared. If the number of photons measured by D1 and D2 is different (the number of photons detected by the single-photon detectors (D1, D2) is (0, 1) or (1, 0) respectively), the subsequent anti-correlation count will be performed: N AC =N AC +1. Otherwise, the anti-correlation count is abandoned. In order to improve the signal-to-noise ratio of target detection, a larger M is generally set, such as M=1000.

[0045] Figure 4 The threshold value N in the first embodiment of the present invention is th The flow chart of the setting calculation algorithm; we combine Figure 2 We assume that the corresponding threshold value is calculated based on the optical path. Specifically:

[0046] 1.1B mode has a transmittance of After the channel, it becomes a mixed state

[0047]

[0048] 1.2C mode has a transmittance of After the channel, it becomes a mixed state

[0049]

[0050] 2.1 Calculating the quantum state after reflection from the target when there is a target

[0051]

[0052] 2.2 Calculating the quantum state after reflection from the target when there is a target

[0053]

[0054] 2.3 Calculating the A-B' quantum state without a target

[0055]

[0056] 2.4 Calculation of the C'-D quantum state without a target

[0057]

[0058] 3.1 Output quantum state after quantum interference with target

[0059] Since ρ AB'C'D (1) There are many non-zero matrix elements. For the sake of simplicity, ρ is omitted here. AB'C'D (1) The calculation results of .

[0060] 3.2 Output quantum state after quantum interference in the absence of a target

[0061]

[0062] 4.1 Calculation of the two modes AD after projecting B' to 0 photon and C' to 1 photon when there is a target

[0063]

[0064] The success probability is

[0065]

[0066] 4.2 Calculation of the AD two modes after projecting B' to 0 photon and C' to 1 photon when there is no target

[0067] According to ρ AB'C'D (0) In its specific form, when there is no target, the probability that B' is projected onto 0 photon and C' is projected onto 1 photon is 0. That is, when there is no target, the situation where B' is projected onto 0 photon and C' is projected onto 1 photon will not occur.

[0068] Q 01 =0.

[0069] 5.1 Calculating the anti-correlation probability of AD two-modal measurement results when there is a target

[0070]

[0071] 5.2 Calculating the probability of anti-correlation between AD and bimodal measurements in the absence of a target

[0072] q=0.

[0073] 6. Set the threshold

[0074]

[0075] Figure 5 The variation trend of the anti-correlation probability with η in the first embodiment of the present invention, where η=10-2 ~10 -4 For comparison, Figure 5 At the same time, it gave With the changing trend of η. ref The anti-correlation probability p given by the dual-transmitter quantum radar decreases rapidly at a rate of η. The rate of decrease. Figure 5 As can be seen, the decline rate of p is significantly lower than that of p ref This shows that dual-transmitter radar has unique advantages in improving signal utilization.

[0076] Figure 6 The missed detection probability of the quantum radar using dual transmitters is given for different signal transmission times M. When a target exists, the probability of anti-correlation of the photon counts of the single-photon detectors D1 and D4 can be approximated by a mean of The variance is Gaussian distribution. Assume The probability of missed detection can be calculated as where η = 10 -2 ~10 -4 ,κ=0.2,λ=0.2. In particular, when η=10 -4 ,M=100000, the probability of missed detection is P m =0.086.

[0077] Figure 7 For the performance comparison between this scheme and the single transmitter scheme, we select the parameter as: η=10 -2 ~10 -4 ,κ=0.2,λ=0.2,M=200000. When η=10 -4 When , the missed detection probability of the dual-transmitter solution is 1 / 8 of that of the single-transmitter solution.

[0078] Figure 8 for Figure 7 Schematic diagram of the single-transmitter scheme in the performance comparison. Schematic diagram of the single-transmitter scheme in the performance comparison. In the single-transmitter scheme, a pair of quantum entangled states is prepared in the transmitter. The quantum state of path B passes through the transmission efficiency The channel reaches the target. The reflectivity of the target is also set to κ. After being reflected by the target, the signal passes through the channel again with a transmission efficiency of The channel reaches the receiver and is received and detected by the single-photon detector D2 in the receiver. At the same time, the quantum state of path A in the transmitter is detected by the single-photon detector D1. The entire target detection still uses multiple signal transmissions and multiple signal receptions. In order to be the same as the number of quantum entangled sources in the M-times dual-transmitter quantum radar scheme, the number of signal transmissions of a single transmitter is set to 2M. Through 2M signal transmissions and corresponding detections, the number of times D1 and D2 simultaneously detect single photons is recorded, and if the number is greater than a preset threshold, the target is considered to exist, otherwise the target is considered not to exist. In the single-transmitter scheme, the simultaneous detection of single-photon signals by two single-photon detectors (i.e., photon correlation) is the key to inferring target information. Because under the single-transmitter condition, the line passes through The line with lower efficiency has a lower calculated missed detection probability.

[0079] Implementation Plan 2

[0080] The limited detection efficiency of the detector is an unavoidable problem in practical quantum radar. Therefore, it is necessary to study the impact of the actual non-ideal detection efficiency on the performance of dual-transmitter quantum radar.

[0081] Figure 9 This is a schematic diagram of the transmitter and receiver of the second embodiment of the present invention. This diagram uses four actual dual-transmitter schemes with non-100% detection efficiency. We use BS0 to mark the 50:50 optical beam splitter with a transmittance of 1 / 2 in the receiver. The transmittance is η d The optical beam splitters BS1, BS2, BS3, and BS4 represent the optical loss caused by the non-ideal detection efficiency in the detector. E, F, G, and H are the four auxiliary signal inputs, all in vacuum state. E', F', G', and H' are dissipated into the environment. In the second embodiment, the photon counts of the four single-photon detectors D1, D2, D3, and D4 are still input into the data discrimination unit, and through Figure 3 The data processing flowchart is used to obtain the target information.

[0082] Figure 10 Schematic diagram of optical port markings of each optical beam splitter in the second embodiment of the present invention.

[0083] In particular, according to Figure 10Schematic diagram of optical ports. The output port of optical delay line DL1 in transmitter 1 is connected to the first input port ① of optical beam splitter BS1. The vacuum state of path E is input via the second input port ② of optical beam splitter BS1. The first output port ③ of BS1 is directly connected to single-photon detector D1. The output port of optical delay line DL2 in transmitter 2 is connected to the first input port ① of optical beam splitter BS4. The vacuum state of path H is input via the second input port ② of optical beam splitter BS4. The first output port ③ of BS4 is directly connected to single-photon detector D2. The first output port ③ of optical beam splitter BS0 in the receiver is connected to the second input port ② of optical beam splitter BS2. The second output port ④ of optical beam splitter BS0 in the receiver is connected to the first input port ① of optical beam splitter BS3. Optical path F is directly connected to the first input port ① of optical beam splitter BS2. Optical path G is directly connected to the second input port of optical beam splitter BS3. The first output terminal ③ of the optical beam splitter BS2 is directly connected to the single-photon detector D3, and the second output terminal ④ of the optical beam splitter BS3 is directly connected to the single-photon detector D4. The optical paths E', F', G', and H' will all dissipate into the environment.

[0084] Figure 11 For different detection efficiencies η d Signal utilization rate of the dual-transmitter quantum radar scheme under the condition, where η=10 -2 ~10 -4 ,κ=0.2,λ=0.2. We take η d =0.7, 0.8, 0.9. At each given η d , we can get the anti-correlation probability of the two transmitters as At the same time, we also use the black dotted line to show the P decreasing at a rate of η. ref =0.15η, where the constant factor 0.15 is to make P ref and η d = 0.7 when the anti-correlation probability is equal. ref =0.15η As η decreases by the power of η. The anti-correlation probability of the quantum radar with dual transmitters is The speed decreases. When η=10 -4 This means that from η = 10 -4 arrive A 100-fold improvement. Figure 11 The results show that even with a practical single-photon detector with non-100% detection efficiency, the quantum radar with dual emitters can still achieve high signal utilization. This will play a very important role in target detection under extreme loss.

[0085] The above is only an embodiment of the present invention, and common knowledge such as the specific structure and / or characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A photon loss-resistant quantum radar device based on dual transmitters, characterized by: The system comprises a first transmitter, a second transmitter, a receiver and a transceiver synchronization system; the first transmitter and the second transmitter each comprise a quantum entangled light source, a signal collimation module and a first single-photon detector; the receiver comprises a quantum interference module and two second single-photon detectors; the first transmitter, the second transmitter and the receiver achieve clock synchronization and real-time communication through the transceiver synchronization system; The quantum entangled light source of the first transmitter completes the preparation of the two-mode quantum entangled state, and transmits one mode to the test area through the signal collimation and transmission unit, and directly sends the other mode to the optical delay line for optical delay. The delayed quantum signal is sent to the first single-photon detector for detection. The first transmitter is equipped with a transceiver synchronization system A for clock synchronization with the receiver and the second transmitter; The quantum entangled light source of the second transmitter completes the preparation of the two-mode quantum entangled state, and transmits one mode to the area to be measured through the signal collimation and transmission unit, and directly sends the other mode to the optical delay line for optical delay. The delayed quantum signal is sent to the first single-photon detector for detection. The second transmitter is equipped with a transceiver synchronization system B for clock synchronization with the receiver and the first transmitter; The receiver is used to interfere with the signals transmitted to the target and returned by the first transmitter and the second transmitter. The interference is performed on the quantum interference module. The interference results of the quantum interference module are detected by two second single-photon detectors. The receiver is provided with a transceiver synchronization system C for clock synchronization with the first transmitter, the second transmitter and the receiver.

2. The dual-transmitter photon loss-resistant quantum radar device according to claim 1, characterized in that: The detection results of the first single-photon detector and the second single-photon detector are both submitted to the data screening unit.

3. The dual-transmitter photon loss-resistant quantum radar device according to claim 2, characterized in that: The data identification unit forms photon counting statistics through the detection results of the first single-photon detector and the second photon detector, and compares them with a preset threshold to form a target determination result, thereby obtaining relevant information of the target.

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