Terahertz quantum communication sensing integrated system and method based on entanglement

Abstract

The invention discloses an entanglement-based terahertz quantum communication sensing integrated system and method. The problem that a traditional communication system is limited in the aspects of spectrum utilization, safety and environmental perception is solved. According to the implementation scheme, an Alice end generates terahertz pulses and idler frequency light pulses, the idler frequency light pulses are used for subsequent measurement, the terahertz pulses are sent to a communication or sensing mode of a Bob end after being extracted, and the terahertz pulses are sent to the Alice end after being extracted, modulated and amplified or directly extracted; the Alice end obtains an initial measurement result of the terahertz pulse by using different detection receivers in a communication or sensing mode; and the Alice end calculates an intrusion parameter, and performs post-processing of error correction and secret amplification on an initial result meeting the intrusion parameter to obtain final bit string information or a result whether a target exists or not. The terahertz-band quantum communication device is high in directivity, good in confidentiality, high in anti-interference performance and high in penetrability in the terahertz band, and can be used for realizing quantum communication and quantum radar detection in the terahertz band at the same time.

Description

Technical Field

[0001] The present invention belongs to the field of quantum communication technology, and further relates to a quantum communication and perception integrated system, which can be used for quantum communication and quantum radar detection in the terahertz band. Background Art

[0002] Terahertz quantum communication uses the quantum state of entangled photons in the terahertz band as an information carrier, transmits light quanta through quantum channels, and uses classical channels to assist in operations such as basis vector comparison, error correction, and density amplification, thereby realizing information transmission between the two communicating parties. This transmission method is different from the classical communication method, that is, if a third party attempts to eavesdrop, both parties in communication will notice it. It ensures the security of communication through the uncertainty principle and the no-cloning theorem in quantum mechanics. Any measurement of a quantum system will interfere with the system and cause perceptible anomalies. By transmitting information through quantum superposition or quantum entanglement, the communication system can detect whether there is eavesdropping, thereby theoretically achieving unconditionally secure communication. Terahertz quantum perception uses the entanglement characteristics between entangled photons in the terahertz band, and emits one of the photons as a detection photon to the target, while the other photon remains in the radar system as a reference photon. When the detection photon interacts with the target and returns, the information of the target, such as the position, speed, shape, etc., can be obtained by measuring and analyzing the quantum correlation characteristics between the returned detection photon and the reference photon, such as measuring the correlation changes in their polarization state and phase. By combining communication and perception, a synaesthesia integrated system is designed. Through joint design, spectrum resource sharing, software and hardware equipment sharing, etc., the integrated design of communication and perception functions is realized, and the fusion and symbiosis of communication and perception functions are achieved.

[0003] The patent document with application number CN201811649053.0 discloses a quantum radar based on continuous variables and its processing method, which includes: S1 generates an optical pulse signal; S2 modulates the signal light of the optical pulse signal based on the continuous variable code and records the quantum state of the signal light; S3 uses the optical pulse signal containing the coded signal light as the detection signal of the quantum radar. S4 splits the echo signal after being reflected by the object to form a first echo signal and a second echo signal. The first echo signal is measured and compared by a monitoring device, and the second echo signal is imaged by an imaging device; S5 determines whether the detection signal is interfered with according to the measurement and comparison results. Although this method can know in real time whether the radar pulse is intercepted by the target and sends an error signal accordingly, causing the detection to be interfered, it uses a single-photon light source, so it cannot monitor whether there is eavesdropping in real time, and its security cannot be guaranteed.

[0004] The patent document with application number CN201710036675.5 discloses a network system and method for the fusion of quantum communication and quantum time-frequency transmission, and its implementation includes: the quantum relay unit emits entangled photon pairs, which are sent to two quantum terminal units respectively through the transmission unit, and the quantum terminal unit reflects the input photons and returns to the quantum relay unit through the transmission unit. The quantum relay unit performs HOM interference measurement to achieve optical path balance. The laser pulse is sent to the quantum terminal unit, which encodes the input light pulse and transmits it back to the quantum relay unit via the transmission channel. After the quantum relay unit obtains the result and publishes the key, it passes through the classical channel and performs clock synchronization. Although this method can improve the security of time-frequency information and realize the fusion of quantum communication and quantum time-frequency transmission, since it does not have a real-time detection module, it cannot monitor whether there is eavesdropping, and cannot guarantee the security of Eve eavesdropping detection.

[0005] At the same time, since the light source bands used by the above two technologies are both in the visible light band, it is impossible to obtain correct detection results in some special scenarios where there is smoke and other obstructions. Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose an entanglement-based terahertz quantum communication and perception integrated system and method to simultaneously realize the two functions of quantum communication and quantum perception, increase the wireless communication frequency band range, ensure the security of communication and perception, and improve the overall performance of the system.

[0007] The technical solutions for achieving the purpose of the present invention include the following:

[0008] 1. An entanglement-based terahertz quantum communication perception integrated system, including a forward terahertz pulse transmission module, a backward terahertz pulse transmission module, an intrusion parameter calculation module, a post-processing module, a single photon detector, characterized in that it also includes a terahertz pulse generation module, a phase modulation module, and a terahertz pulse detection module;

[0009] The terahertz pulse generation module is used to generate signal terahertz pulses and idler light pulses, and connect them to the forward terahertz pulse transmission module, the terahertz pulse detection module and the single photon detector respectively.

[0010] The phase modulation module is connected to the forward terahertz pulse transmission module, the backward terahertz pulse transmission module and the single photon detector, respectively, and is used to modulate and amplify the terahertz photons received within the modulation symbol period;

[0011] The Hertz pulse detection module is respectively connected to the terahertz pulse generation module, the backward terahertz pulse transmission module and the intrusion parameter calculation module, and is used to use the idle frequency light pulse and the terahertz pulse to perform joint detection or double zero difference detection, and send the measurement results to the intrusion parameter calculation module to calculate the intrusion parameters, and then input the measurement results that meet the intrusion parameters to the post-processing module for error correction and density amplification post-processing.

[0012] Furthermore, the terahertz pulse generation module includes a spontaneous parametric down-converter and a beam splitter. The converter is used to generate a signal terahertz pulse and an idler light pulse. The beam splitter is used to divide the terahertz pulse into two parts, sending 2% of the terahertz pulse to the photon detector and sending the remaining terahertz pulse to the forward terahertz pulse transmission module, and sending the idler light pulse to the terahertz pulse detection module for subsequent measurement.

[0013] Furthermore, the terahertz pulse detection module includes a terahertz switch, a joint detection receiver, and a double zero-difference detection receiver. The terahertz switch is used to select whether the current mode is a communication mode or a perception mode; the joint detection receiver is used to perform a joint detection on the terahertz pulse sent by the backward terahertz pulse transmission module and the idler light pulse sent by the terahertz pulse generation module in the communication mode, and output an initial detection result; the double zero-difference detection receiver is used to perform a double zero-difference detection on the terahertz pulse sent by the backward terahertz pulse transmission module and the idler light pulse sent by the terahertz pulse generation module in the perception mode, and output an initial detection result.

[0014] Furthermore, the phase modulation module includes a beam splitter, a terahertz switch, a modulator, and an amplifier;

[0015] The beam splitter is used to split the terahertz pulse sent by the forward terahertz pulse transmission module into two parts, and send 1% of the terahertz pulse to the single photon detector and send the remaining terahertz pulse to the terahertz switch;

[0016] The terahertz switch is used to select the current mode as the communication mode or the sensing mode. When in the communication mode, the terahertz pulse is sent to the modulator; when in the sensing mode, the terahertz pulse is sent to the backward terahertz pulse transmission module for transmission;

[0017] The modulator is used to perform second-order phase modulation on the terahertz pulse in the communication mode and send the modulated pulse to the amplifier;

[0018] The amplifier is used to amplify the modulated pulse in the communication mode and send it to the backward terahertz pulse transmission module for transmission.

[0019] 2. An integrated terahertz quantum communication perception method based on entanglement is the communication perception between Alice and Bob, characterized by comprising:

[0020] Alice uses a spontaneous parametric down-converter to generate terahertz pulses and idler pulses, and retains the idler pulse locally for subsequent measurement. It splits the terahertz pulse into two parts and sends them to the single-photon detector and Bob respectively.

[0021] When Bob is in communication mode, he extracts, modulates and amplifies the received terahertz pulse and sends it to Alice. When in sensing mode, he sends the terahertz pulse reflected by the target to Alice.

[0022] When Alice is in communication mode, she uses a joint detection receiver to obtain the initial measurement result of the terahertz pulse. When Alice is in sensing mode, she uses a double homodyne detection receiver to obtain the initial measurement result R of the terahertz pulse. x ;

[0023] After Alice obtains the initial measurement results, it uses the measurement results of the single-photon detector to calculate the intrusion parameters. In the communication mode, the initial results that meet the intrusion parameters are corrected and processed for density amplification to obtain the final results. In the perception mode, the initial results that meet the intrusion parameters are corrected and processed for density amplification to obtain the final results, and then compared with the minimum threshold of the total error rate after error correction and density amplification:

[0024] If the final result is higher than the threshold, it is determined that the target does not exist.

[0025] If the final result is lower than the threshold, it is determined that the target exists.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] First, the present invention adopts terahertz signal light-visible idler light entangled two-photon pair as light source, sends terahertz pulse to free channel space at the transmitting end, receives, extracts, modulates, amplifies or directly sends back to the transmitting end for joint measurement at the receiving end, and obtains the final result through intrusion parameter calculation and post-processing. Therefore, it has large transmission bandwidth, high wireless transmission data rate, narrower beam, and has extremely high directionality, better confidentiality, strong anti-interference and penetration when working in the terahertz frequency band. Compared with its traditional communication perception integrated system, the present invention has greater advantages in the application of quantum communication and quantum radar fields.

[0028] Second, since the present invention adopts an integrated system of quantum communication and perception, it can simultaneously realize the functions of quantum communication and quantum radar, thereby improving the overall performance of quantum communication and quantum radar equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a block diagram of an integrated terahertz quantum communication and perception system based on entanglement according to the first embodiment of the present invention;

[0030] Figure 2 The figure is a structural and working principle diagram of the first embodiment of the present invention.

[0031] Figure 3 This is a flowchart of the integrated implementation of terahertz quantum communication perception based on entanglement according to the second embodiment of the present invention; DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the examples of the present invention.

[0033] The embodiments of the present invention include an entanglement-based terahertz quantum communication and perception integrated system and an entanglement-based terahertz quantum communication and perception integrated method, wherein the integrated method includes a communication mode and a perception mode.

[0034] It should be noted that the terms “first” and “second” in the present invention are used to distinguish similar objects rather than to describe a specific order or sequence.

[0035] Embodiment 1: A terahertz quantum communication and perception integrated system based on entanglement.

[0036] Reference Figure 1 This example includes a forward terahertz pulse transmission module 1, a backward terahertz pulse transmission module 2, an intrusion parameter calculation module 3, a post-processing module 4, a terahertz pulse generation module 5, a phase modulation module 6, a terahertz pulse detection module 7 and two single-photon detectors. Among them: the terahertz pulse generation module 5 is respectively connected to the forward terahertz pulse transmission module 1, the terahertz pulse detection module 7 and the first single-photon detector 8; the forward terahertz pulse transmission module 1 is respectively connected to the terahertz pulse generation module 5 and the phase modulation module 6; the phase modulation module 6 is connected to the forward terahertz pulse transmission module 1, the backward terahertz pulse transmission module 2 and the second single-photon detector 9; the backward terahertz pulse transmission module 2 is respectively connected to the phase modulation module 6 and the terahertz pulse detection module 7; the terahertz pulse detection module 7 is respectively connected to the backward terahertz pulse transmission module 2, the intrusion parameter calculation module 3 and the terahertz pulse generation module 5; the intrusion parameter calculation module 3 is respectively connected to the terahertz pulse detection module 7, the post-processing module 4, the first single-photon detector 8 and the second single-photon detector 9.

[0037] Reference Figure 2 , the partial module structure and overall working principle of the system of the present invention are as follows:

[0038] The forward terahertz pulse transmission module 1 and the backward terahertz pulse transmission module 2 share two terahertz antennas. The first terahertz antenna 11 is used in the forward terahertz pulse transmission module 1 to send the terahertz pulse sent by the terahertz pulse generation module 5 to the free space channel for transmission, and is used in the backward terahertz pulse transmission module 2 to receive the terahertz pulse sent from the free space channel; the second terahertz antenna 12 is used in the forward terahertz pulse transmission module 1 to receive the terahertz pulse sent from the free space channel, and is used in the backward terahertz pulse transmission module 2 to send the terahertz pulse sent by the phase modulation module 6 to the free space channel for transmission.

[0039] The intrusion parameter calculation module 3 is used to calculate the intrusion parameters of the eavesdropper Eve by using the measurement results and the detection results of the first single-photon detector 8 and the second first single-photon detector 9 after the terahertz pulse detection module 7 obtains the measurement results. When the intrusion parameters meet the requirements, the initial results are sent to the post-processing module 4.

[0040] The post-processing module 4 is used to perform error correction and density amplification on the initial result that meets the intrusion parameters obtained by the intrusion parameter calculation module 3 to obtain the final result, and also compare the final result with the minimum threshold of the total error rate in the perception mode. When the result is higher than the set threshold, it is determined that the object does not exist, and when the result is lower than the threshold, it is determined that the object exists.

[0041] The terahertz pulse generation module 5 includes a first converter 51 under spontaneous parameters and a beam splitter 52. The converter 51 is used to generate a signal terahertz pulse and an idler light pulse, and send the idler light pulse to the terahertz pulse detection module 7 for subsequent measurement; the beam splitter 52 is used to divide the terahertz pulse into two parts, and send 2% of the terahertz pulse to the first single-photon detector 8, and send the remaining terahertz pulse to the forward terahertz pulse transmission module 1.

[0042] The phase modulation module 6 comprises a second beam splitter 61, a first terahertz switch 62, a modulator 63 and an amplifier 64;

[0043] The second beam splitter 61 is used to split the terahertz pulse sent by the forward terahertz pulse transmission module 1 into two parts, and send 1% of the terahertz pulse to the single photon detector 8, and send the remaining terahertz pulse to the terahertz switch;

[0044] The terahertz switch 62 is used to select whether the current mode is the communication mode or the sensing mode. When in the communication mode, the terahertz pulse is sent to the modulator 63; when in the sensing mode, the terahertz pulse is sent to the backward terahertz pulse transmission module 2 for transmission;

[0045] The modulator 63 is used to perform second-order phase modulation on the terahertz pulse in the communication mode, and send the modulated pulse to the amplifier 64, which is used to amplify the modulated pulse in the communication mode and send it to the backward terahertz pulse transmission module 2 for transmission.

[0046] The terahertz pulse detection module 7 includes a second terahertz switch 71, a joint detection receiver 72, and a double zero-difference detection receiver 73. The terahertz switch is used to select whether the current mode is a communication mode or a sensing mode; the joint detection receiver 72 is used to perform a joint detection on the terahertz pulse sent by the backward terahertz pulse transmission module 2 and the idler light pulse sent by the terahertz pulse generation module 5 in the communication mode, and output an initial detection result; the double zero-difference detection receiver 73 is used to perform a double zero-difference detection on the terahertz pulse sent by the backward terahertz pulse transmission module 2 and the idler light pulse sent by the terahertz pulse generation module 5 in the sensing mode, and output an initial detection result.

[0047] The first single-photon detector 8 is used to detect the pulse sent by the terahertz pulse generation module 5, and input the pulse detection result to the intrusion parameter calculation module 3 to calculate the intrusion parameter.

[0048] The second single-photon detector 9 is used to detect the pulse received by the phase modulation module 6, and input the pulse detection result to the intrusion parameter calculation module 3 to calculate the intrusion parameter.

[0049] Reference Figure 3 The terahertz quantum communication perception integration method based on entanglement of the present invention refers to the communication perception between Alice and Bob, using a terahertz switch to switch between the communication mode and the perception mode, respectively realizing quantum communication and quantum perception between the two ends. Different embodiments of the terahertz quantum communication perception integration method based on entanglement are given below:

[0050] This example 2 is an integrated method of terahertz quantum communication perception based on entanglement in communication mode.

[0051] The implementation steps of this example are as follows:

[0052] Step 1: Generate terahertz pulses.

[0053] Alice generates M pairs of terahertz signal modes and optical idler modes through a converter under spontaneous parameters, which can be expressed as: in, represents the mth terahertz signal mode, represents the mth optical idler mode, m=1,···,M;

[0054] M terahertz signal modes Combined together to form a terahertz pulse P 1 :

[0055]

[0056] Since the terahertz signal mode and the optical idler mode are in an entangled state, the entanglement relationship between them can be expressed by the Wigner covariance matrix The formula is as follows:

[0057]

[0058] Among them, A SI =(V S +V 0 )·I 2 , C SI =(V S +1)·I 2 , V S is the variance of the terahertz pulse and the visible idler pulse, V 0 represents the thermal noise variance,

[0059] Step 2: Send a forward terahertz pulse.

[0060] Alice transmits the terahertz signal to By beam splitter A / (1-κ A ) is divided into two parts, which are sent as follows:

[0061] Send 2% of the terahertz signal mode to the single photon detector for channel monitoring, and execute step 7;

[0062] 98% of the signal mode Sent to free space, it is represented by:

[0063]

[0064] in, represents the annihilation operator of the vacuum state, κ A Indicates the reflection ratio of the beam splitter.

[0065] M terahertz signal modes Combined together to form a forward terahertz pulse P 2 :

[0066]

[0067] Step 3, receiving the forward terahertz pulse.

[0068] Bob receives the terahertz signal mode in free space through the terahertz antenna It is expressed as:

[0069]

[0070] M terahertz signal modes Combined together to form the received terahertz pulse P 3 :

[0071]

[0072] in, represents the channel thermal noise, η represents the channel transmittance, Represents the signal modulus sent by Alice.

[0073] Step 4: Generate backward terahertz pulses through phase modulation.

[0074] First, Bob receives the terahertz signal. Through the beam splitter according to κ B / (1-κ B ) is divided into two parts, and 1% of the terahertz signal mode is sent to the single photon detector for channel monitoring, and 99% of the signal mode is sent to the single photon detector for channel monitoring. Enter modulation, which is expressed as:

[0075]

[0076] in represents the annihilation operator of the vacuum state, κ B Indicates the reflection ratio of the beam splitter;

[0077] Then, Bob modulates the received signal. The output signal is modulated by the modulator

[0078]

[0079] Where i = 0, 1 represents the bit value of the information to be transmitted by Bob;

[0080] Then, Bob uses an amplifier to amplify the modulated signal to obtain the amplified signal modulus.

[0081]

[0082] Among them G B represents the gain of the amplifier, represents the noise mode.

[0083] Then, Bob will amplify the M signal modes Combined together to form a backward terahertz pulse P 4 :

[0084]

[0085] Step 5, transmitting the backward terahertz pulse.

[0086] Bob transmits the signal mode through the terahertz antenna Sent to Alice, Alice receives the receiving module: in, represents the channel thermal noise, and η represents the channel transmittance;

[0087] M terahertz return modes Combined together to form the received backward terahertz pulse P 5 :

[0088]

[0089] Step 6: Detect the terahertz pulse to obtain the received bit value bits.

[0090] Alice first receives the terahertz signal and local idler mode Sent to the joint detection receiver. The output detection result is c (m) :

[0091]

[0092] Where K represents the number of single photon detectors in the joint detection receiver. represents the detection result of the kth single-photon detector;

[0093] Alice can then obtain the bit value bits received by Alice based on the corresponding relationship between the phase and the output result of the joint detection receiver.

[0094] Step 7: Calculate the intrusion parameters.

[0095] 7-1) Alice uses a single-photon detector to measure the 2% terahertz signal pulse sent in step 2 to obtain the single-photon counting rate S at Alice's end. A , the 1% terahertz return pulse sent in step 4 is measured using a single photon detector to obtain the single photon count rate S at Bob's end B , the duration of use meets the gate T g The time alignment coincidence rate C is obtained by measuring the coincidence between the terahertz pulse sent by Alice and the idler light pulse. IA and time misalignment rate

[0096] 7-2) Alice's usage duration meets gate T g The coincidence measurement between the terahertz pulse received by Bob and the idler light pulse is performed to obtain the time alignment coincidence rate C IB and time misalignment rate

[0097] 7-3) Alice calculates the intrusion parameter f of the channel by Eve, based on the parameters obtained in 7-1) and 7-2) and the corresponding propagation delays of the transmitted and received terahertz pulses. E :

[0098]

[0099] 7-4) Alice determines whether the intrusion parameter is greater than or equal to 0.25%:

[0100] If so, the quantum communication is terminated;

[0101] Otherwise, go to step 8.

[0102] Step 8: Alice performs post-processing of error correction and confidentiality amplification on the initial detection result to obtain the final result.

[0103] This example 3 is an integrated method of terahertz quantum communication perception based on entanglement in the perception mode.

[0104] The implementation steps of this example are as follows:

[0105] Step 1: Generate terahertz pulses.

[0106] Alice generates M pairs of terahertz signal modes and optical idler modes through a converter under spontaneous parameters, which can be expressed as: in, represents the mth terahertz signal mode, represents the mth optical idler mode, m=1,···,M;

[0107] M terahertz signal modes Combined together to form a terahertz pulse P 1 :

[0108]

[0109] Since the terahertz signal mode and the optical idler mode are in an entangled state, the entanglement relationship between them can be expressed by the Wigner covariance matrix The formula is as follows:

[0110]

[0111] Among them, A SI =(V S +V 0 )·I 2 , C SI =(V S +1)·I 2 , V S is the variance of the terahertz pulse and the visible idler pulse, V 0 represents the thermal noise variance,

[0112] Step 2: Send a forward terahertz pulse.

[0113] Alice transmits the terahertz signal to By beam splitter A / (1-κ A ) is divided into two parts, which are sent as follows:

[0114] Send 2% of the terahertz signal mode to the single photon detector for channel monitoring and execute step seven;

[0115] 98% of the signal mode Sent to free space, it is represented by:

[0116]

[0117] in, represents the annihilation operator of the vacuum state, κ A Indicates the reflection ratio of the beam splitter.

[0118] M terahertz signal modes Combined together to form a forward terahertz pulse P 2 :

[0119]

[0120] Step 3: Receive the forward terahertz pulse.

[0121] Bob receives the terahertz return mode of the free space channel It is expressed as follows according to whether there is an object under test in the free space channel:

[0122]

[0123] in, represents the noise modulus, κ represents the reflectivity of the object being measured;

[0124] M terahertz return modes Combined together to form the received terahertz pulse P 3 ′:

[0125]

[0126] Step 4: Generate backward terahertz pulses through phase modulation.

[0127] 4.1) Bob receives the terahertz signal and returns it to Through the beam splitter according to κ B / (1-κ B ) is divided into two parts, which are sent as follows:

[0128] Send 1% of the terahertz return mode to the single photon detector for channel monitoring and execute step seven;

[0129] 99% of the terahertz is returned to the Sent to Alice, it is represented as:

[0130]

[0131] in represents the annihilation operator of the vacuum state, κ B Indicates the reflection ratio of the beam splitter;

[0132] 4.2) Return M terahertz waves to the module Combined together to form a backward terahertz pulse P 4 ′:

[0133]

[0134] Step five: transmit the backward terahertz pulse.

[0135] 5.1) Bob transmits the terahertz return signal through the terahertz antenna. Sent to Alice, Alice receives the receiving module It is expressed as:

[0136]

[0137] in, represents the channel thermal noise, and η represents the channel transmittance;

[0138] 5.2) Return M terahertz waves to the module Combined together to form the received backward terahertz pulse P 5 ′:

[0139]

[0140] Step 6: Detect the terahertz pulse and obtain the quantum illumination result R x .

[0141] Alice-to-terahertz return module and idler mode Perform double zero difference detection to obtain the initial measurement result R x :

[0142]

[0143] in, is the density operator, and Tr(·) is the trace operation.

[0144] Step 7: Calculate the intrusion parameters.

[0145] 7.1) Alice uses a single-photon detector to measure the 2% terahertz signal pulse sent in step 2 to obtain the single-photon counting rate S at Alice's end. A , the 1% terahertz return pulse sent in step 4 is measured using a single photon detector to obtain the single photon count rate S′ at Bob’s end B , the duration of use meets the gate T g The time alignment coincidence rate C is obtained by measuring the coincidence between the terahertz pulse sent by Alice and the idler light pulse. IA and time misalignment rate

[0146] 7.2) Alice's usage duration meets the gate T g The coincidence measurement between the terahertz pulse received by Bob and the idler light pulse is performed to obtain the time alignment coincidence rate C I ' B and time misalignment rate

[0147] 7.3) Based on the parameters obtained in 7.1) and 7.2) and the corresponding propagation delays of the transmitted and received terahertz pulses, the intrusion parameter f of the eavesdropper Eve on the channel is calculated. E ′:

[0148]

[0149] 7.4) Alice determines whether the intrusion parameter is greater than or equal to 0.25%:

[0150] If so, quantum perception is terminated;

[0151] Otherwise, go to step 8;

[0152] Step 8, post-processing.

[0153] 8.1) Alice sets the expected value R of the measurement operator when the object does not exist, based on the fact that the reflectivity is 0 when the object exists and 1 when the object does not exist.0 , measuring operator variance The measurement operator expectation R when the measured object exists 1 , the variance of the measurement operator when the measured object does not exist

[0154] 8.2) Using the set value of 8.1), calculate the minimum threshold value R of the total error probability Th :

[0155]

[0156] 8.3) Perform post-processing of error correction and density amplification on the initial detection results to obtain the final result R x ;

[0157] 8.4) Compare the final result with the minimum threshold R of the total error probability Th For comparison:

[0158] When R x ≥R Th , determine that the object does not exist;

[0159] When R x <R Th , determine the existence of the object.

[0160] The above descriptions are only a few specific examples of the present invention and do not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, they may make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

[0161] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the implementation scheme of the present invention to facilitate understanding, and the order of the step numbers is not limited.

Claims

1. A terahertz quantum communication and perception integrated system based on entanglement, comprising a forward terahertz pulse transmission module (1), a backward terahertz pulse transmission module (2), an intrusion parameter calculation module (3), a post-processing module (4), a single photon detector (8), and a single photon detector (9), characterized in that: It also includes a terahertz pulse generation module (5), a phase modulation module (6), and a terahertz pulse detection module (7); The terahertz pulse generation module (5) is used to generate a signal terahertz pulse and an idler light pulse, and respectively connect them to the forward terahertz pulse transmission module (1), the terahertz pulse detection module (7) and the single photon detector (8). The phase modulation module (6) is respectively connected to the forward terahertz pulse transmission module (1), the backward terahertz pulse transmission module (2) and the single photon detector (9), and is used to modulate and amplify the terahertz photons received within the modulation symbol period; The terahertz pulse detection module (7) is respectively connected to the terahertz pulse generation module (5), the backward terahertz pulse transmission module (2) and the intrusion parameter calculation module (3), and is used to perform joint detection or double zero difference detection using idle light pulses and terahertz pulses, and send the measurement results to the intrusion parameter calculation module (3) to calculate the intrusion parameters, and then input the measurement results that meet the intrusion parameters to the post-processing module (4) for error correction and density amplification post-processing.

2. The system according to claim 1, characterized in that The intrusion parameter calculation module (3) is respectively connected to the terahertz pulse detection module (7), the post-processing module (4), the single-photon detector (8) and the single-photon detector (9), and is used to calculate the intrusion parameters of the eavesdropper Eve by using the measurement results, the detection results of the single-photon detector (8) and the single-photon detector (9) after the terahertz pulse detection module (7) obtains the measurement results, and when the intrusion parameters meet the requirements, the initial results are sent to the post-processing module (4).

3. The system according to claim 1, characterized in that The terahertz pulse generation module (5) comprises a spontaneous parametric down-converter and a beam splitter, wherein the converter is used to generate a signal terahertz pulse and an idler light pulse, and the beam splitter is used to split the terahertz pulse into two parts, sending 2% of the terahertz pulse to a photon detector (8), sending the remaining terahertz pulse to a forward terahertz pulse transmission module (1), and sending the idler light pulse to a terahertz pulse detection module (7) for subsequent measurement.

4. The system according to claim 1, characterized in that The terahertz pulse detection module (7) comprises a terahertz switch, a joint detection receiver, and a double homodyne detection receiver. The terahertz switch is used to select whether the current mode is a communication mode or a sensing mode. The joint detection receiver is used to perform joint detection on the terahertz pulse sent by the backward terahertz pulse transmission module (2) and the idler light pulse sent by the terahertz pulse generation module (5) in the communication mode, and output an initial detection result. The double homodyne detection receiver is used to perform double homodyne detection on the terahertz pulse sent by the backward terahertz pulse transmission module (2) and the idle frequency light pulse sent by the terahertz pulse generation module (5) in the sensing mode, and output an initial detection result.

5. The system according to claim 1, characterized in that The forward terahertz pulse transmission module (1) and the backward terahertz pulse transmission module (2) share two terahertz antennas; the first terahertz antenna is used in the forward terahertz pulse transmission module (1) to transmit the terahertz pulse sent by the terahertz pulse generation module (5) to a free space channel for transmission, and is used in the backward terahertz pulse transmission module (2) to receive the terahertz pulse sent from the free space channel; the second terahertz antenna is used in the forward terahertz pulse transmission module (1) to receive the terahertz pulse sent from the free space channel, and is used in the backward terahertz pulse transmission module (2) to transmit the terahertz pulse sent by the phase modulation module (6) to the free space channel for transmission.

6. The system according to claim 1, characterized in that The phase modulation module (6) comprises a beam splitter, a terahertz switch, a modulator, and an amplifier; The beam splitter is used to split the terahertz pulse sent by the forward terahertz pulse transmission module (1) into two parts, and send 1% of the terahertz pulse to the single photon detector (9), and send the remaining terahertz pulse to the terahertz switch; The terahertz switch is used to select whether the current mode is a communication mode or a sensing mode. When in the communication mode, the terahertz pulse is sent to the modulator; when in the sensing mode, the terahertz pulse is sent to the backward terahertz pulse transmission module (2) for transmission; The modulator is used to perform second-order phase modulation on the terahertz pulse in the communication mode and send the modulated pulse to the amplifier; The amplifier is used to amplify the modulated pulse in the communication mode and send it to the backward terahertz pulse transmission module (2) for transmission.

7. The system according to claim 1, characterized in that The post-processing module (4) is used to perform error correction and density amplification on the initial result that meets the intrusion parameter obtained by the intrusion parameter calculation module (3) to obtain a final result, and also compare the final result with the minimum threshold of the total error rate in the sensing mode. When the result is higher than the threshold, It is determined that the object does not exist, and when the result is lower than the threshold, it is determined that the object exists.

8. An integrated terahertz quantum communication perception method based on entanglement is the communication perception between Alice and Bob, characterized in that: include: Alice uses a spontaneous parametric down-converter to generate terahertz pulses and idler pulses, and retains the idler pulse locally for subsequent measurement. It splits the terahertz pulse into two parts and sends them to the single-photon detector and Bob respectively. When Bob is in communication mode, he extracts, modulates and amplifies the received terahertz pulses and sends them to Alice. In the sensing mode, the terahertz pulse reflected by the target is sent to Alice; When Alice is in communication mode, she uses a joint detection receiver to obtain the initial measurement result of the terahertz pulse. When Alice is in sensing mode, she uses a double homodyne detection receiver to obtain the initial measurement result R of the terahertz pulse. x ; After Alice obtains the initial measurement results, it uses the measurement results of the single-photon detector to calculate the intrusion parameters. In the communication mode, the initial results that meet the intrusion parameters are corrected and processed for density amplification to obtain the final results. In the perception mode, the initial results that meet the intrusion parameters are corrected and processed for density amplification to obtain the final results, and then compared with the minimum threshold of the total error rate after error correction and density amplification: If the final result is higher than the threshold, it is determined that the target does not exist. If the final result is lower than the threshold, it is determined that the target exists.

9. The method according to claim 8, characterized in that The Alice end generates terahertz pulses and visible light idler pulses using a spontaneous parametric down-converter, and uses the Wigner covariance matrix according to the entangled state of the two. The formula is as follows: Among them, A SI =(V S +V0)·I2, C SI =(V S +1)·I2,V S represents the variance of the terahertz pulse and the idler pulse, V0 represents the thermal noise variance, 10. The method according to claim 8, characterized in that When the Bob end is in communication mode, the received terahertz pulse is extracted, modulated and amplified and then sent to the Alice end, which is implemented as follows: The extraction refers to that Bob first modulates the received signal Through the beam splitter according to κ B / (1-κ B ) splits a portion of the beam splitting ratio and sends it to the single photon detector for channel monitoring, and then the remaining signal mode Enter modulation, which is expressed as: in represents the vacuum state, κ B Indicates the reflection ratio of the beam splitter; The modulation refers to the modulation of the received signal by Bob. The signal output after modulation by the modulator Where i = 0, 1 represents the bit value of the information to be transmitted by Bob; The amplification is the amplification of the modulated signal by Bob. After being amplified by the amplifier, the output signal is Among them G B represents the gain of the amplifier, Represents the noise state.

11. The method according to claim 8, characterized in that Alice obtains the initial measurement result R of the terahertz pulse by using a double homodyne detection receiver. x , which is expressed as: in, is the density operator, Tr(·) is the trace operation, stands for terahertz pulse, Represents idler optical pulse.

12. The method according to claim 8, characterized in that After Alice obtains the initial measurement result, it uses the measurement result of the single photon detector to calculate the intrusion parameter, and its formula for the communication mode is f E And the formula f in perception mode E ' respectively represent as follows: Among them, C IA , They represent the time alignment coincidence rate and time misalignment coincidence rate between the terahertz pulse and the idler light pulse sent by Alice, respectively. IB , They represent the time alignment coincidence rate and time misalignment coincidence rate between the terahertz pulse and the idler light pulse received by Bob, respectively. A is the single photon counting rate of the single photon detector at Alice, S B Represents the single photon counting rate of the single photon detector at Bob's end. Among them, C IA , They represent the time alignment coincidence rate and time misalignment coincidence rate between the terahertz pulse and the idler light pulse sent by Alice, respectively. I ' B , They represent the time alignment coincidence rate and time misalignment coincidence rate between the terahertz pulse and the idler light pulse received by Bob, respectively. A represents the single photon counting rate of the single photon detector at Alice, S′ B Represents the single photon counting rate of the single photon detector at Bob's end.

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