A quantum radar experimental device based on high-probability photon catalysis

Abstract

The present invention belongs to the technical field of quantum radar, and discloses a quantum radar experimental device based on high-probability photon catalysis, which includes a transmitter and a receiver. The transmitter includes a paired coherent state light source and an optical terminal transmitter that transmits a control signal to the paired coherent state light source. The paired coherent state light source generates quantum entangled states A and B. The receiver includes an optical terminal receiver, a high-probability photon catalysis device, a photon measurement device, and a target judgment logic unit. The high-probability photon catalysis device is used to catalyze the echo signal. The optical terminal transmitter and the optical terminal receiver are connected by an optical fiber, and the channel loss is 0.2 dB / km. The present invention reduces noise and improves the target detection effect by catalyzing the target echo signal.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum radar, and particularly relates to a quantum radar experimental device based on high-probability photon catalysis. Background Art

[0002] Quantum radar is an emerging technology that combines quantum information technology with traditional target detection technology. It has unique advantages in detecting dim targets in strong background noise. Therefore, quantum radar has become a new type of target detection technology vigorously developed by major countries in the world.

[0003] A quantum radar experimental device generally consists of a transmitter and a receiver. The signal transmitted by the transmitter is an entangled signal, and the receiver is responsible for collecting and detecting the echo signal reflected by the target. Among them, the receiver of the quantum radar is the most critical part in the design of the quantum radar. The currently known quantum radar receiver directly uses the received signal for quantum measurement and obtains target information by using the subsequent target judgment logic unit. Due to the large environmental noise, the signal received by the receiver contains more environmental noise, and these noises can directly enter the photon measurement device, so it will seriously affect the effect of target detection.

[0004] Therefore, the present invention provides a quantum radar experimental device based on high-probability photon catalysis. By using the high-probability photon catalysis device to catalyze the target signal and sending the catalyzed signal into the target judgment logic unit, the noise entering the target judgment logic unit can be greatly reduced, and the target detection effect can be improved. Summary of the Invention

[0005] The present invention aims to provide a quantum radar experimental device based on high-probability photon catalysis, and the present invention aims to solve the technical problems existing in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: A quantum radar experimental device based on high-probability photon catalysis, including a transmitter and a receiver. The transmitter includes a paired coherent state light source and an optical terminal transmitter that emits a control signal to the paired coherent state light source. The paired coherent state light source generates quantum entangled states A and B.

[0007] The receiver includes an optical terminal receiver, a high-probability photon catalysis device, a photon measurement device, and a target judgment logic unit. The high-probability photon catalysis device is used to catalyze the echo signal. The optical terminal transmitter and the optical terminal receiver are connected by an optical fiber, and the channel loss is 0.2 dB / km.

[0008] In another preferred embodiment of the present invention, the high-probability photon catalysis device is a photon number regulation device with single input and single output.

[0009] In another preferred embodiment of the present invention, the high-probability photon catalysis device is a cascaded photon catalysis device. The high-probability photon catalysis device includes a plurality of phase modulators, a plurality of optical beam splitters, and a single-photon detector D0, and the number of phase modulators is one less than the number of optical beam splitters.

[0010] In another preferred embodiment of the present invention, the photon measurement device includes a single-photon detector D1, a single-photon detector D2, and a function generator. The function generator is used to receive the control signal of the optical terminal receiver and generate an electrical pulse signal to control the single-photon detector D1 and the single-photon detector D2.

[0011] In another preferred embodiment of the present invention, the function generator is connected to the single-photon detector D1 and the single-photon detector D2 through a coaxial cable, and the impedance parameter of the coaxial cable is 50 ohms.

[0012] In another preferred embodiment of the present invention, the working process of the target judgment logic unit is as follows: First, initialize the threshold parameter N th , set the total number of times M of emitting quantum entangled states to 1000, set the photon effective count value count = 0, and the counter i = 1;

[0013] After the echo signal C reflected by the interaction between the quantum state B emitted by the paired coherent state light source and the target is successfully catalyzed, detect single photons through the detector D0, and read the measurement result of the photon measurement device; if the single-photon detector D1 and the single-photon detector D2 detect single photons simultaneously, the effective count value count = count + 1; if the single-photon detector D1 and the single-photon detector D2 do not detect single photons simultaneously, the effective count value count is not updated; at this time, the i-th photon catalysis and photon detection end, the counter is automatically incremented by 1, and i = i + 1;

[0014] Then perform the next cycle until the paired coherent state light source emits M times of quantum entangled states in total; after M times of quantum entangled states are sent, compare the effective count value count with the threshold N th ; if count ≤ N th , it is determined that there is no target, otherwise it is determined that there is a target.

[0015] In another preferred embodiment of the present invention, set the threshold N th such that P m = P f / 10, where P m represents the miss detection probability, and P f represents the false alarm probability.

[0016] The present invention has the following beneficial effects compared with the prior art:

[0017] 1. In the present invention, the photon catalysis technology is adopted to catalyze the echo signal C, enabling high-quality signals (with less noise in the signals) to enter the target judgment logic unit, facilitating the subsequent extraction of signals and improving the target detection effect.

[0018] 2. The present invention can significantly improve the catalysis probability through a cascade-type photon catalysis device, greatly reducing the consumption and waste of the echo signal C caused by catalysis failure; moreover, the adopted photon catalysis technology has wide applicability and a photon number adjustment function. In addition to being applied to a quantum radar receiver, it can also be used in other information processing processes such as quantum precision measurement and quantum imaging with photon number adjustment requirements.

[0019] Meanwhile, the high-probability photon catalysis device can achieve the amplification of optical quantum states, and the high-probability photon catalysis device itself is also a high-probability photon amplification device.

[0020] 3. The receiver of the present invention only needs to discriminate and perform information inversion on the echo signal C with successful catalysis, and the signal discrimination is more efficient and targeted. Therefore, under the same conditions, the power consumption of the receiver system of the quantum radar is lower.

[0021] 4. The present invention uses an optical terminal transmitter and an optical terminal receiver to be synchronized through optical signals. Compared with the traditional use of coaxial cables (channel loss is 20 dB / km), the channel transmission loss is small (0.2 dB / km), and it can be applied to target detection under the condition that the transmitter and receiver are far apart.

[0022] 5. In the present invention, different weights are set for the false alarm probability and the miss detection probability, and the miss detection probability is set to 1 / 10 of the false alarm probability, which is more focused on the detection of hostile targets.

[0023] 6. The transmitter of the present invention uses an optical terminal transmitter to control a paired coherent state light source to generate a quantum entanglement state for target detection, and its coherence is higher, providing a new solution path for improving the target detection performance of the quantum radar from the perspective of the signal source.

[0024] In summary, the present invention catalyzes the echo signal C received by the receiver to achieve the catalysis of the echo signal C. Then, the catalyzed high-quality echo signal is sent into the photon measurement device to improve the target detection performance of the quantum radar. At the same time, in order to improve the catalysis effect, a cascade-type photon catalysis device is proposed, achieving a significant improvement in the catalysis probability, providing an important support for the receiver design of a practical quantum radar.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0027] Figure 1 is the overall schematic diagram of the embodiment of the present application.

[0028] Figure 2 is the schematic structural diagram of the high-probability photon catalysis device in the embodiment of the present application.

[0029] Figure 3 is the schematic structural diagram of the photon measurement device in the embodiment of the present application.

[0030] Figure 4 is the logic flowchart of the target judgment logic unit in the embodiment of the present application.

[0031] Figure 5 is the superposition coefficient of the quantum entanglement state emitted by the paired coherent state light source on the photon number state in the embodiment of the present application.

[0032] Figure 6 is the overall optical path diagram of the embodiment of the present application, where high-probability photon catalysis adopts a three-beam splitter configuration.

[0033] Figure 7 is the schematic structural diagram of the high-probability photon catalysis device when N = 1, N = 2, and N = 3 in the embodiment of the present application.

[0034] Figure 8 is the comparison diagram of the catalytic success probabilities between traditional photon catalysis and high-probability photon catalysis in the embodiment of the present application.

[0035] Figure 9 is the schematic diagram of the threshold setting principle in the embodiment of the present application.

[0036] Figure 10 is the diagram of the misjudgment probability situation of the quantum radar using high-probability photon catalysis in the embodiment of the present application. Detailed implementation manners

[0037] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "lateral", "vertical", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0039] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0040] The present invention provides a quantum radar experimental device based on high-probability photon catalysis, as Figure 1 shown, which includes a transmitter and a receiver. The transmitter includes a paired coherent state light source and an optical terminal transmitter. The optical terminal transmitter emits a control signal to the paired coherent state light source, exciting the paired coherent state light source to generate a pair of quantum entanglement states of the paired coherent state type. The two-phase modes of the quantum entanglement state are quantum entanglement state A and B respectively, and the single-sided photon number thereof is μ. Quantum state B is sent to the target to be measured and interacts with the target to be measured, and then the echo signal C is reflected by the target to be measured.

[0041] The receiver includes an optical terminal receiver, a high-probability photon catalysis device, a photon measurement device, and a target judgment logic unit. The optical terminal transmitter and the optical terminal receiver are connected by an optical fiber, and the channel loss is 0.2 dB / km.

[0042] The high-probability photon catalysis device is used to realize the catalysis of the echo signal C. The high-probability photon catalysis device is a single-input and single-output photon number regulation device, and the high-probability photon catalysis device is a cascaded photon catalysis device, which includes a single-photon detector D0, a plurality of phase modulators, and a plurality of optical beam splitters, and the number of phase modulators is one less than that of the optical beam splitters. The high-probability photon catalysis device can be applied to quantum information processing processes such as quantum precision measurement and quantum imaging.

[0043] Combined with Figure 2 shown, in this embodiment, the high-probability photon catalysis device includes N-1 phase modulators and N optical beam splitters. For convenience, it can be set that φ1 = φ2 = … φ N-1 = φ. Use T i to represent the transmission coefficient of the i-th optical beam splitter. For convenience, it can be assumed that T1 = T2 = … TN = T.

[0044] The photon measurement device is as Figure 3 shown, including a single photon detector D1, a single photon detector D2 and a function generator. Both the single photon detector D1 and the single photon detector D2 are connected to the function generator through coaxial cables. The impedance parameter of the coaxial cable is 50 ohms, and the connector is an SMC RF connector.

[0045] The usage method of the quantum radar experimental device based on high-probability photon catalysis is as follows:

[0046] Step 1, inside the transmitter

[0047] The optical terminal transmitter sends a control signal to the paired coherent state light source. After the paired coherent state light source is excited, quantum entangled states A and B are generated. Among them, quantum state A is directly input into the photon measurement device, and quantum state B interacts with the target to be measured and reflects an echo signal C.

[0048] The optical terminal transmitter also sends a signal to the optical terminal receiver through an optical fiber.

[0049] Step 2, inside the receiver

[0050] The echo signal C enters the high-probability photon catalysis device, and its input is C, and the output is C N . The E mode is the auxiliary quantum state of the high-probability photon catalysis device and is initialized to a single photon state. The quantum state to be catalyzed is input from the C mode. First, it interacts with the E mode on the optical beam splitter BS1. The quantum states after the interaction are respectively located in C1 and E1. Then, the E1 mode is modulated by a phase modulator with a parameter of φ1, and a phase e is added to the quantum state of the E1 mode iφ1 . The E1 mode and the C1 mode perform a second interaction on the optical beam splitter BS2, and their outputs are respectively located in C2 and E2.

[0051] The E2 mode is modulated by a phase modulator with a parameter of φ2, and a phase e is added to the quantum state of the E2 mode iφ2 . And so on, until after N times of interaction with the optical beam splitter, the outputs are C N and E N The quantum state of the E N mode is detected by the single photon detector D0. When and only when the single photon detector D0 detects a single photon, the photon catalysis is successful; and the detection result of the single photon detector D0 is input into the target judgment logic unit.

[0052] The signal after catalysis and the quantum state A are simultaneously transmitted into the photon measurement device. After the optical terminal receiver receives the signal sent by the optical terminal transmitter, pulse trigger signal 1 and pulse trigger signal 2 are generated and transmitted into the photon measurement device, where they work in coordination with the photon measurement device and the measurement result is output.

[0053] The specific working process of the photon measurement device is as follows: The quantum state A is input into the single-photon detector D1. Since the quantum state A is directly input by the transmitter, in order to synchronize with the signal catalyzed by the high-probability photon catalysis device, pulse trigger signal 1 is input into the function generator, and after the pulse trigger signal 1 delays the signal through a coaxial cable, it controls the single-photon detector D1; while the signal catalyzed by the high-probability photon catalysis device is input into the single-photon detector D2. After pulse trigger signal 2 is input into the function generator, it directly controls the single-photon detector D2. And the measurement result is output through the single-photon detector D1 and the single-photon detector D2.

[0054] Finally, the target judgment logic unit conducts logical analysis and discrimination on the measurement results output by the high-probability photon catalysis device and the photon measurement device, and then completes the determination of the target information.

[0055] Combined Figure 4 As shown, the working process of the target judgment logic unit is as follows:

[0056] First, initialize the threshold parameter N th , set the total number of times M for emitting the quantum entangled state to 1000, set the photon effective count value count = 0, and the counter i = 1.

[0057] After the quantum state B emitted by the paired coherent state light source interacts with the target and the reflected echo signal C arrives at the high-probability photon catalysis device, it is catalyzed by the high-probability photon catalysis device. When the single-photon detector D0 detects a single photon, the catalysis is successful. At this time, an effective count count is generated, and the measurement result of the photon measurement device is read. If the single-photon detector D1 and the single-photon detector D2 detect single photons simultaneously, then the effective count value count = count + 1; if the single-photon detector D1 and the single-photon detector D2 do not detect single photons simultaneously, then the effective count value count is not updated. Thus, the i-th photon catalysis and photon detection end, the counter is automatically incremented by 1, and i = i + 1.

[0058] Then, perform the next loop until the paired coherent state light source emits the quantum entangled state M times in total.

[0059] After M times of quantum entangled states are sent, compare the effective count value count with the threshold N th ; if count ≤ N th , then it is judged that there is no target, otherwise it is judged that there is a target.

[0060] The specific implementation parameters of each part in this embodiment are as follows:

[0061] 1. The superposition coefficient c of the quantum entangled state emitted by the paired coherent state in the photon number state n As Figure 5 shown, the paired coherent state is a quantum entangled state with photon number correlation, and its expression in the photon number space is |ψ> = where μ is the average photon number on a single mode, and I0(x) is the first modified Bessel function.

[0062] Set μ = 0.8. As n gradually increases from 0, the coefficient c of the photon number state n rapidly decreases. When n = 9, the coefficient of its photon number state can already be ignored.

[0063] 2. The overall optical path diagram of the quantum radar in this embodiment is as Figure 6 shown. The high-probability photon catalysis device adopts a configuration of three optical beam splitters, that is, N = 3. The quantum state B interacts with the target to be measured, and the target to be measured uses an optical beam splitter with a reflectivity of κ. When conducting the experiment, if κ = 0 is set, it means the target does not exist; if κ = κ t , it means a target with a reflectivity of κ t exists in the optical path.

[0064] 3. As shown in Figure 7 , this embodiment uses the high-probability photon catalysis device ( Figure 7 , part (c)) to compare with the traditional photon catalysis device ( Figure 7 , part (a)). During the comparison process, the paired coherent state parameter μ = 0.8 with the same intensity is taken, the target reflectivity is set to κ t = 0.1, the transmittance T of the beam splitter is taken as 0.2 in the traditional photon catalysis, and in the high-probability photon catalysis, the optical beam splitters φ1 = φ2 = φ3 = φ.

[0065] The comparison results are as Figure 8 shown. Among them, there is no phase rotation in the traditional photon catalysis, while there is phase rotation in the high-probability photon catalysis device. Figure 8 shows the catalysis probability when φ varies between 0 and π / 2. It can be seen that when φ takes 0 and π / 2, the success probability of the high-probability photon catalysis is 1.22 to 4.74 times higher than that of the traditional photon catalysis.

[0066] 4. The setting of the threshold is the key to affecting the performance of the quantum radar and an important component in realizing the functions of the quantum radar. In the existing quantum radar solutions, usually the same weights are assigned to the false alarm probability and the miss detection probability, and the arithmetic mean of the two is used as the final measurement standard of the quantum radar. However, in this embodiment, different weights are set for the false alarm probability and the miss detection probability.

[0067] The schematic diagram of the threshold setting in this embodiment is as Figure 9 shown. Using P m to represent the miss detection probability and P f to represent the false alarm probability, set the threshold N th such that P m = P f / 10.

[0068] The misjudgment probability of the quantum radar is where is the prior occurrence probability of the target before radar detection. According to the definitions of the miss detection probability and the false alarm probability, P f = Prob(count > N th |κ = κ t ), P m = Prob(count < N th |κ = 0).

[0069] In a specific experiment, under the conditions of M >> 1, κ = κ t , the effective count count approximately follows a Gaussian distribution with a mean of μ1 and a variance of . Under the conditions of M >> 1, κ = 0, the effective count count approximately follows a Gaussian distribution with a mean of μ0 and a variance of . The miss detection probability can be expressed as: The false alarm probability can be expressed as The threshold N th needs to satisfy P m = P f / 10.

[0070] The mean μ0, the variance of and the mean μ1, the variance of involved in this embodiment can be obtained by the quantum state ρ AC on the two modes of the quantum state A and the echo signal C when the catalysis is successful. Let ρ AC (1) and ρ AC (0) respectively represent the quantum states on the two modes of the quantum state A and the echo signal C when the reflectivity κ = κ t and κ = 0, then and They are the optical field annihilation operators in the quantum state A and the echo signal C mode respectively.

[0071] The thresholds N corresponding to different phases φ in the high-probability photon catalysis device th are shown in Table 1. At the same time, for comparison, the thresholds N used in traditional photon catalysis under the same threshold condition P m =P f / 10 are also given. Since the traditional photon catalysis device does not contain the phase φ, the threshold of traditional photon catalysis does not change with the phase φ. th

[0072] Table 1

[0073]

[0074]

[0075] 5. The false judgment probability situation of the quantum radar using high-probability photon catalysis in this embodiment is as Figure 10 shown. Taking the environmental noise intensity as N B =0.20, as the phase increases, the false judgment probability decreases rapidly. For the quantum radar using the traditional photon catalysis method, its false judgment probability is a fixed value. Through high-probability photon catalysis, the present invention reduces the false judgment probability to 1 / 45 of the original, achieving a 16 dB reduction in the false judgment probability.

[0076] In summary, the present invention realizes the catalysis of the target signal by adding a high-probability photon catalysis device in the receiver, and sends the catalyzed signal into the target judgment logic unit, completing the discrimination and detection of high-quality echo signals, greatly reducing the noise entering the target judgment logic unit, effectively improving the signal extraction efficiency and utilization rate, and further improving the target detection effect. At the same time, a cascade-type photon catalysis device is designed, increasing the known success probability of photon catalysis by an order of magnitude, strongly supporting the target information inversion ability, and taking an important step towards practical quantum radar technology.

[0077] In the description of this specification, the descriptions referring to terms such as "preferred embodiment", "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0078] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A quantum radar experimental device based on high-probability photon catalysis, comprising a transmitter and a receiver, characterized in that: The transmitter includes a paired coherent state light source and an optical terminal transmitter that emits control signals to the paired coherent state light source. The paired coherent state light source generates quantum entangled states A and B; The receiver includes an optical terminal receiver, a high-probability photon catalysis device, a photon measurement device, and a target judgment logic unit. The high-probability photon catalysis device is used to catalyze the echo signal. The optical terminal transmitter and the optical terminal receiver are connected by an optical fiber, and the channel loss is 0.2 dB / km; The high-probability photon catalysis device is a photon number regulation device with single input and single output; the high-probability photon catalysis device is a cascaded photon catalysis device. The high-probability photon catalysis device includes multiple phase modulators, multiple optical beam splitters, and a single-photon detector D0, and the number of phase modulators is 1 less than the number of optical beam splitters; the photon measurement device includes a single-photon detector D1, a single-photon detector D2, and a function generator. The function generator is used to receive the control signal of the optical terminal receiver and generate an electrical pulse signal to control the single-photon detector D1 and the single-photon detector D2.

2. The quantum radar experimental device based on high-probability photon catalysis according to claim 1, characterized in that: The function generator is connected to the single-photon detector D1 and the single-photon detector D2 through a coaxial cable, and the impedance parameter of the coaxial cable is 50 ohms.

3. The quantum radar experimental device based on high-probability photon catalysis according to claim 2, characterized in that: The working process of the target judgment logic unit is as follows. First, initialize the threshold parameter , set the total number of times of emitting quantum entangled states , set the effective photon count value , counter ; After the echo signal C reflected by the interaction between the quantum state B emitted by the paired coherent state light source and the target is successfully catalyzed, single photons are detected by the detector D0, and the measurement results of the photon measurement device are read; if single photons are simultaneously detected by the single photon detector D1 and the single photon detector D2, the effective count value ; If single-photon detectors D1 and D2 do not simultaneously detect single photons, the effective count value is not updated; at this time, the th photon catalysis and photon detection end, and the counter automatically increments by 1, ; Perform the next loop until the paired coherent state light source emits a total of quantum entangled states; wait until the transmission of quantum entangled states is completed, and compare the effective count value with the threshold ; if , it is determined that there is no target, otherwise it is determined that there is a target.

4. A quantum radar experimental device based on high-probability photon catalysis according to claim 3, characterized in that: Set a threshold such that , where represents the missed detection probability, represents the false alarm probability.

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