Entanglement-based terahertz quantum communication perception integration system and method

Abstract

The application discloses a kind of entanglement-based terahertz quantum communication sensing integrated system and method.For solving the problem of the limitation of traditional communication system in spectrum utilization, security and environmental perception.The implementation scheme is: Alice end generates terahertz pulse and idle frequency light pulse, and uses idle frequency light pulse as subsequent measurement, extracts terahertz pulse and sends it to Bob end communication or sensing mode, respectively extracts, modulates and amplifies or directly extracts and sends to Alice end;Alice end uses different detection receivers to obtain the initial measurement result of terahertz pulse in communication or sensing mode;Alice end calculates the invasion parameter again, and the initial result meeting the invasion parameter is processed to obtain the final bit string information or the result whether there is target after error correction and secret amplification.The application has high directivity, good secrecy, strong anti-interference and penetration in terahertz frequency band, and can be used for simultaneously realizing quantum communication and quantum radar detection in terahertz band.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of quantum communication, and further relates to a quantum communication and perception integrated system, which can be used for quantum communication and quantum radar detection in a terahertz wave band. BACKGROUND

[0002] Terahertz quantum communication is a way of realizing information transmission between two communication parties by using quantum states of entangled photons in a terahertz wave band as information carriers, transmitting optical quanta through a quantum channel, and realizing base vector comparison, error correction and secret amplification by auxiliary classical channels. This transmission way is different from the classical communication way, that is, if a third party tries to eavesdrop, the two parties of communication will be aware of it, and the security of communication is ensured by the uncertainty principle and the no-cloning theorem in quantum mechanics. Any measurement on a quantum system will disturb the system and cause an observable anomaly. By transmitting information through quantum superposition states or quantum entangled states, the communication system can detect whether there is eavesdropping, so as to realize unconditional secure communication in theory. Terahertz quantum perception is to use the entanglement characteristics between entangled photons in a terahertz wave band, emit one photon as a probe photon to a target, and keep the other photon in the radar system as a reference photon. When the probe photon returns after interacting with the target, the information of the target such as the position, velocity and shape of the target can be obtained by measuring and analyzing the quantum correlation characteristics between the returned probe photon and the reference photon, such as the correlation changes in their polarization states and phases. By combining communication and perception, a communication and perception integrated system is designed, and the integration of communication and perception functions is realized through joint design, spectrum resource sharing, software and hardware device sharing and other means, so as to realize the fusion and symbiosis of communication and perception functions.

[0003] The patent document with the application number CN201811649053.0 discloses a quantum radar based on continuous variables and a processing method thereof, which realizes the following steps: S1, generating an optical pulse signal; S2, performing continuous variable-based encoding modulation on signal light of the optical pulse signal, and recording the quantum state of the signal light; S3, using the optical pulse signal containing the encoded signal light as a detection signal of the quantum radar. S4, splitting the echo signal reflected by the object to form a first echo signal and a second echo signal, measuring and comparing the first echo signal through a monitoring device, and imaging and processing the second echo signal through an imaging device; S5, judging whether the detection signal is disturbed according to the measurement and comparison result. Although this method can know in real time whether the radar pulse is intercepted by the target and send an error signal accordingly to disturb the detection, it cannot monitor in real time whether there is eavesdropping because it uses a single-photon light source, and its security cannot be guaranteed.

[0004] The patent document with the application number CN201710036675.5 discloses a quantum communication and quantum time-frequency transmission fusion network system and method, which realizes the following: a quantum relay unit emits an entangled photon pair, which is respectively sent to two quantum terminal units through a transmission unit, and the quantum terminal unit reflects the input photon and returns to the quantum relay unit through the transmission unit. The quantum relay unit performs HOM interference measurement to realize optical path balance. Laser pulses are sent to the quantum terminal unit, which encodes the input optical pulses and transmits them back to the quantum relay unit through a transmission channel. After the quantum relay unit obtains the result and publishes the key, the classical channel is used for 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, it cannot monitor whether there is eavesdropping and cannot guarantee the security of eavesdropping detection because it does not set a real-time detection module.

[0005] Meanwhile, since the light sources of the above two technologies are in the visible light band, the detection result cannot be correctly obtained in some special situations with smoke and other obstructions. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provides a terahertz quantum communication and sensing integrated system and method based on entanglement, which can realize both quantum communication and quantum sensing functions, increase the wireless communication frequency band range, guarantee the security of communication and sensing, and improve the overall performance of the system.

[0007] The technical solution for achieving the purpose of the present application includes the following:

[0008] 1. A terahertz quantum communication and sensing integrated system based on entanglement, comprising a forward terahertz pulse transmission module, a backward terahertz pulse transmission module, an intrusion parameter calculation module, a post-processing module, and a single-photon detector, characterized in that it further comprises 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 idle frequency light pulses, and connect them with the forward terahertz pulse transmission module, the terahertz pulse detection module, and the single-photon detector, respectively.

[0010] The phase modulation module is connected with 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 connected with the terahertz pulse generation module, the backward terahertz pulse transmission module and the intrusion parameter calculation module respectively, is used for combined detection or double zero difference detection by using idle frequency light pulses and terahertz pulses, and sends the measurement results to the intrusion parameter calculation module to calculate the intrusion parameters, and then inputs the measurement results meeting the intrusion parameters to the post-processing module for error correction and secret amplification post-processing.

[0012] Further, the terahertz pulse generation module comprises a spontaneous parametric down converter and a beam splitter, the converter is used for generating signal terahertz pulses and idle frequency light pulses, and the beam splitter is used for splitting the terahertz pulses into two parts, sending 2% of the terahertz pulses to a photon detector, and sending the remaining terahertz pulses to the forward terahertz pulse transmission module, and sending the idle frequency light pulses to the terahertz pulse detection module for subsequent measurement.

[0013] Further, the terahertz pulse detection module comprises a terahertz switch, a combined detection receiver and a double zero difference detection receiver, the terahertz switch is used for selecting whether the current mode is a communication mode or a sensing mode; the combined detection receiver is used for, in the communication mode, performing combined detection on the terahertz pulses sent by the backward terahertz pulse transmission module and the idle frequency light pulses sent by the terahertz pulse generation module, and outputting an initial detection result; and the double zero difference detection receiver is used for, in the sensing mode, performing double zero difference detection on the terahertz pulses sent by the backward terahertz pulse transmission module and the idle frequency light pulses sent by the terahertz pulse generation module, and outputting an initial detection result.

[0014] Further, the phase modulation module comprises a beam splitter, a terahertz switch, a modulator and an amplifier.

[0015] The beam splitter is used for splitting the terahertz pulses sent by the forward terahertz pulse transmission module into two parts, sending 1% of the terahertz pulses to a single photon detector, and sending the remaining terahertz pulses to the terahertz switch.

[0016] The terahertz switch is used for selecting whether the current mode is a communication mode or a sensing mode, in the communication mode, the terahertz switch sends the terahertz pulses to the modulator, and in the sensing mode, the terahertz switch sends the terahertz pulses to the backward terahertz pulse transmission module for transmission.

[0017] The modulator is used for, in the communication mode, performing second-order phase modulation on the terahertz pulses, and sending the modulated pulses to the amplifier.

[0018] The amplifier is used for, in the communication mode, amplifying the modulated pulses, and sending the modulated pulses to the backward terahertz pulse transmission module for transmission.

[0019] 2. A method for integrating communication and sensing based on entanglement in terahertz quantum communication, which is communication and sensing between Alice and Bob, characterized in that it comprises:

[0020] Alice generates terahertz pulses and idler light pulses by using a spontaneous parametric down-converter, retains the idler light pulses locally for subsequent measurement, and divides the terahertz pulses into two parts, which are sent to a single-photon detector and Bob respectively;

[0021] Bob sends the received terahertz pulses to Alice after extraction, modulation and amplification in the communication mode, and sends the terahertz pulses reflected by the target to Alice in the sensing mode;

[0022] Alice obtains the initial measurement result of the terahertz pulses by using a joint detection receiver in the communication mode, and obtains the initial measurement result R of the terahertz pulses by using a double zero difference detection receiver in the sensing mode. x ;

[0023] After Alice obtains the initial measurement result, the intrusion parameter is calculated by using the measurement result of the single-photon detector, and the final result is obtained by error correction and secret amplification of the initial result meeting the intrusion parameter in the communication mode, and the final result after error correction and secret amplification of the initial result meeting the intrusion parameter is compared with the minimum threshold of the total error rate in the sensing mode:

[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 application has the following advantages:

[0027] Firstly, the present application uses terahertz signal light-visible idler light entangled two-photon pairs as light sources, sends the terahertz pulses to the free channel space at the sending end, receives the terahertz pulses at the receiving end after extraction, modulation, amplification or directly sends them back to the sending end for joint measurement, calculates the intrusion parameter, and obtains the final result after post-processing, so that the transmission bandwidth is large, the wireless transmission data rate is high, the beam is narrower, and the working frequency band is in the terahertz band, which has extremely high directivity, better security, stronger anti-interference and penetration, and compared with the traditional communication and sensing integrated system, the present application has greater advantages in the field of quantum communication and quantum radar.

[0028] Secondly, the present application uses a quantum communication and sensing integrated system, which can simultaneously realize the functions of quantum communication and quantum radar, and improves the overall performance of quantum communication and quantum radar equipment. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The system block diagram of the embodiment one of the application based on entanglement of terahertz quantum communication and sensing integration is shown in the figure.

[0030] Figure 2 The structure and working principle diagram of the embodiment one of the application is shown in the figure.

[0031] Figure 3 The flow chart of the embodiment two of the application based on entanglement of terahertz quantum communication and sensing integration is shown in the figure. DETAILED DESCRIPTION

[0032] In order to make the person skilled in the art better understand the application scheme, the technical scheme in the application will be described clearly and completely below by combining the figures in the application examples.

[0033] The embodiment of the application includes a terahertz quantum communication and sensing integration system based on entanglement, and a terahertz quantum communication and sensing integration method based on entanglement, wherein the integration method includes a communication mode and a sensing mode.

[0034] It should be noted that the terms "first" and "second" in the application are used to distinguish similar objects, and are not intended to describe a specific order or sequence.

[0035] Embodiment one, a terahertz quantum communication and sensing integration system based on entanglement.

[0036] Referring to Figure 1 , the present 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 connected with the forward terahertz pulse transmission module 1, the terahertz pulse detection module 7 and the first single-photon detector 8 respectively; the forward terahertz pulse transmission module 1 is connected with the terahertz pulse generation module 5 and the phase modulation module 6 respectively; the phase modulation module 6 is connected with 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 connected with the phase modulation module 6 and the terahertz pulse detection module 7 respectively; the terahertz pulse detection module 7 is connected with the backward terahertz pulse transmission module 2, the intrusion parameter calculation module 3 and the terahertz pulse generation module 5 respectively; the intrusion parameter calculation module 3 is connected with the terahertz pulse detection module 7, the post-processing module 4, the first single-photon detector 8 and the second single-photon detector 9 respectively.

[0037] Referring to Figure 2 , the structure of part of the modules of the system and the overall working principle 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 for transmitting the terahertz pulse sent by the terahertz pulse generation module 5 into the free space channel for transmission in the forward terahertz pulse transmission module 1, and is used for receiving the terahertz pulse sent in the free space channel in the backward terahertz pulse transmission module 2; the second terahertz antenna 12 is used for receiving the terahertz pulse sent in the free space channel in the forward terahertz pulse transmission module 1, and is used for transmitting the terahertz pulse sent by the phase modulation module 6 into the free space channel for transmission in the backward terahertz pulse transmission module 2.

[0039] The intrusion parameter calculation module 3 is used for calculating the intrusion parameter of the eavesdropper Eve by using the measurement result and the detection result 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 result, and sending the initial result to the post-processing module 4 when the intrusion parameter meets the requirement.

[0040] The post-processing module 4 is used for performing error correction and secret amplification post-processing on the initial result meeting the intrusion parameter obtained by the intrusion parameter calculation module 3 to obtain a final result, and also comparing the final result with the total error rate minimum threshold value in the sensing mode, and determining that the object does not exist when the result is higher than the set threshold value, and determining that the object exists when the result is lower than the threshold value.

[0041] The terahertz pulse generation module 5 comprises a first parametric down conversion converter 51 and a beam splitter 52, the converter 51 is used for generating a signal terahertz pulse and an idler light pulse, and sending the idler light pulse to the terahertz pulse detection module 7 for subsequent measurement; the beam splitter 52 is used for dividing the terahertz pulse into two parts, and sending 2% of the terahertz pulse to the first single photon detector 8, and sending 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 for dividing the terahertz pulse sent by the forward terahertz pulse transmission module 1 into two parts, and sending 1% of the terahertz pulse to the single photon detector 8, and sending the remaining terahertz pulse to the terahertz switch;

[0044] The terahertz switch 62 is used for selecting whether the current mode is a communication mode or a sensing mode, and sending the terahertz pulse to the modulator 63 in the communication mode, and sending the terahertz pulse to the backward terahertz pulse transmission module 2 for transmission in the sensing mode;

[0045] The modulator 63 is used for second-order phase modulation of the terahertz pulse in the communication mode, and the modulated pulse is sent to the amplifier 64 for amplification of the modulated pulse in the communication mode, and the amplified pulse is sent 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 homodyne detection receiver 73.

[0047] The first single-photon detector 8 is used for detecting the pulse sent by the terahertz pulse generation module 5 and inputting the pulse detection result to the intrusion parameter calculation module 3 for calculation of the intrusion parameter.

[0048] The second single-photon detector 9 is used for detecting the pulse received by the phase modulation module 6 and inputting the pulse detection result to the intrusion parameter calculation module 3 for calculation of the intrusion parameter.

[0049] Reference Figure 3 The present application is based on the entangled terahertz quantum communication and sensing integrated method, which refers to the communication and sensing between Alice and Bob, uses a terahertz switch to switch between the communication mode and the sensing mode, and realizes quantum communication and quantum sensing between the two ends.

[0050] In this example 2, the entangled terahertz quantum communication and sensing integrated method in the communication mode is provided.

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

[0052] Step 1: Generate a terahertz pulse.

[0053] Alice generates M pairs of terahertz signal modes and optical idler modes through a converter under spontaneous parametric down-conversion, which is represented as: wherein, represents the mth terahertz signal mode, represents the mth optical idler mode, m = 1,..., M;

[0054] M terahertz signal modes The M terahertz signal modes are combined together to form a forward terahertz pulse P1:

[0055]

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

[0057]

[0058] Wherein, A SI = (V S + V0) · I2, C SI = (V S + 1) · I2, V S represents the variance of the terahertz pulse and the visible idler light pulse, V0 represents the thermal noise variance,

[0059] Step 2, send forward terahertz pulse.

[0060] The terahertz signal mode Through the beam splitter, it is divided into two parts by the beam splitting ratio of κ A / (1-κ A ), and the following transmission is carried out respectively:

[0061] 2% of the terahertz signal mode is sent to a single-photon detector for channel monitoring, and step 7 is performed;

[0062] 98% of the signal mode Is sent to free space, which is represented as:

[0063]

[0064] Wherein, Annihilation operator of vacuum state, κ A Indicates the reflection ratio of the beam splitter.

[0065] M terahertz signal modes Are combined together to form a forward terahertz pulse P2:

[0066]

[0067] Step 3, receive forward terahertz pulse.

[0068] The terahertz signal mode In free space is received by a terahertz antenna at the Bob end, which is represented as:

[0069]

[0070] M terahertz signal modes are combined together to form a received terahertz pulse P3:

[0071]

[0072] where, represents the channel thermal noise, η represents the channel transmittance, represents the signal mode sent by Alice.

[0073] Step 4, generate a backward terahertz pulse by phase modulation.

[0074] Firstly, the Bob end will receive the terahertz signal mode is split into two parts via a beam splitter in a beam splitting ratio of κ B / (1-κ B ), and 1% of the terahertz signal mode is sent to a single-photon detector for channel monitoring, and 99% of the signal mode is sent into modulation, which is represented as:

[0075]

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

[0077] Then, the Bob end will receive the signal mode via a modulator to output a signal mode

[0078]

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

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

[0081]

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

[0083] Then, the Bob end combines M amplified signal modes together to form a backward terahertz pulse P4:

[0084]

[0085] Step 5, transmitting backward terahertz pulse.

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

[0087] M terahertz return modes are combined together to form a received backward terahertz pulse P5:

[0088]

[0089] Step 6, detecting the terahertz pulse to obtain the received bit value bits.

[0090] Alice end first transmits the terahertz receiving mode and the local idle frequency mode to the joint detection receiver. The output detection result is c (m) :

[0091]

[0092] wherein, 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 end can obtain the bit value bits received by Alice according to the corresponding relationship between the phase and the joint detection receiver output result.

[0094] Step 7, calculating the intrusion parameter.

[0095] 7-1) Alice end measures the single-photon counting rate S A of Alice end by using a single-photon detector for 2% of the terahertz signal pulse transmitted in step 2, B measures the single-photon counting rate S g of Bob end by using a single-photon detector for 1% of the terahertz return pulse transmitted in step 4, IA performs coincidence measurement between the terahertz pulse and the idle frequency light pulse transmitted by Alice end to obtain the time alignment coincidence rate C g and the time misalignment coincidence rate

[0096] 7-2) Alice end performs coincidence measurement between the terahertz pulse and the idle frequency light pulse received by Bob end to obtain the time alignment coincidence rate C IB and the time misalignment coincidence rate

[0097] 7-3) Alice end calculates the intrusion parameter f of the channel by Eve according to the parameters obtained in 7-1) and 7-2) and in combination with the propagation delay corresponding to the sending and receiving of terahertz pulses E :

[0098]

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

[0100] If yes, terminate the quantum communication;

[0101] Otherwise, execute step 8.

[0102] Step 8, Alice end performs post-processing on the initial detection result to obtain the final result.

[0103] In this example 3, a sensing mode terahertz quantum communication sensing integrated method based on entanglement.

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

[0105] Step one, generate a terahertz pulse.

[0106] Alice end generates M pairs of terahertz signal modes and optical idler modes through a converter under spontaneous parameter: Wherein, represents the mth terahertz signal mode, represents the mth optical idler mode, m = 1, ···, M;

[0107] Combine M terahertz signal modes to form a terahertz pulse P1:

[0108]

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

[0110]

[0111] Wherein, A SI = (V S + V0)·I2, C SI = (V S +1)·I2, V SV0 represents the variance of thermal noise,

[0112] Step two, sending forward terahertz pulse.

[0113] Alice end sends the terahertz signal mode Through the beam splitter by κ A / (1-κ A ) beam splitting ratio, respectively, as follows:

[0114] 2% of the terahertz signal mode is sent to a single photon detector for channel monitoring, step seven is performed;

[0115] 98% of the signal mode is sent to free space, which is represented as:

[0116]

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

[0118] M terahertz signal modes are combined together to form a forward terahertz pulse P2:

[0119]

[0120] Step three, receiving forward terahertz pulse.

[0121] Bob receives the terahertz return mode of the free space channel, which is represented as:

[0122]

[0123] wherein, represents the noise mode, κ represents the reflectivity of the measured object;

[0124] M terahertz return modes are combined together to form a received terahertz pulse P3':

[0125]

[0126] Step four, generating backward terahertz pulse by phase modulation.

[0127] 4.1) Bob end sends the received terahertz return mode via a beam splitter by κ B / (1-κ B) are split into two parts and sent as follows:

[0128] 1% of the terahertz return modes are sent to a single photon detector for channel monitoring, performing step seven;

[0129] 99% of the terahertz return modes are sent to Alice, which is denoted as:

[0130]

[0131] where is the annihilation operator of the vacuum state, κ B is the reflection ratio of the beam splitter;

[0132] 4.2) M terahertz return modes are combined to form a backward terahertz pulse P4':

[0133]

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

[0135] 5.1) The terahertz return modes are sent to Alice by a terahertz antenna at Bob's end, and the received modes are received at Alice's end, which is denoted as:

[0136]

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

[0138] 5.2) M terahertz return modes are combined to form a received backward terahertz pulse P5':

[0139]

[0140] Step six, detect the terahertz pulse to obtain the quantum illumination result R x .

[0141] Alice performs double homodyne detection on the terahertz return modes and the idler modes to obtain the initial measurement result R x :

[0142]

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

[0144] Step 7: Calculate the intrusion parameters.

[0145] 7.1) Alice measures the single-photon count rate S at the Alice end using a single-photon detector on the 2% terahertz signal pulse sent in step two. A The single-photon count rate S′ at the Bob end is measured using a single-photon detector on the 1% terahertz return pulse sent in step four. B The duration of use conforms to the gate T g The timing alignment accuracy C is obtained by measuring the coincidence between the terahertz pulse and the idler optical pulse sent from the Alice end. IA Compliance rate with time misalignment

[0146] 7.2) Alice uses duration conforming to gate T g The timing alignment accuracy C is obtained by measuring the coincidence between the terahertz pulse received at the Bob end and the idler optical pulse. I ′ B Compliance rate with time misalignment

[0147] 7.3) Based on the parameters obtained in 7.1) and 7.2) and combined with 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, then terminate quantum perception;

[0151] Otherwise, proceed to step 8;

[0152] Step 8, post-processing.

[0153] 8.1) Alice sets the reflectivity to 0 when the measured object is present and 1 when the measured object is absent, and sets the expected value R0 and variance of the measurement operator when the measured object is absent. The expected value R1 of the measurement operator when the measured object exists, and the variance of the measurement operator when the measured object does not exist.

[0154] 8.2) Using the settings in 8.1), calculate the minimum threshold R for the total error probability. Th :

[0155]

[0156] 8.3) Post-processing of the initial detection result to correct errors and amplify the confidence, to obtain the final result R x ;

[0157] 8.4) Comparing the final result with the total error probability minimum threshold R Th :

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

[0159] When R x < R Th , it is determined that the object exists.

[0160] The above description is only several specific examples of the present application, and does not constitute any limitation on the present application. Obviously, after understanding the content and principles of the present application, those skilled in the art can make various modifications and changes in form and details without departing from the principles and structures of the present application, but these modifications and changes based on the idea of the present application are still within the protection scope of the claims of the present application.

[0161] It should be noted that the step numbers in the specification and claims of the present application are only for clearly describing the embodiments of the present application, and are not limited in sequence.

Claims

1. A system for entanglement-based terahertz quantum communication and sensing integration, 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 first single-photon detector (8), and a second single-photon detector (9), characterized in that, It also includes a terahertz pulse generation module (5), a phase modulation module (6), a terahertz pulse detection module (7); The terahertz pulse generation module (5) is used for generating signal terahertz pulses and idle frequency light pulses, and connecting them with the forward terahertz pulse transmission module (1), the terahertz pulse detection module (7) and the first single photon detector (8) respectively, The phase modulation module (6) is connected with the forward terahertz pulse transmission module (1), the backward terahertz pulse transmission module (2) and the second single photon detector (9) respectively, and is used for modulating and amplifying the terahertz photons received in the modulation symbol period. The terahertz pulse detection module (7) is connected with the terahertz pulse generation module (5), the backward terahertz pulse transmission module (2) and the intrusion parameter calculation module (3) respectively, and is used for joint detection or double zero difference detection with the idle frequency light pulse and the terahertz pulse, and sends the measurement results to the intrusion parameter calculation module (3) to calculate the intrusion parameter, and then inputs the measurement results meeting the intrusion parameter to the post-processing module (4) for error correction and privacy amplification post-processing. The terahertz pulse detection module (7) includes a second terahertz switch, a joint detection receiver and a double zero difference detection receiver, the second 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 idle frequency light pulse sent by the terahertz pulse generation module (5) in the communication mode, and output initial detection results; The double zero difference detection receiver is used to perform double zero difference 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 initial detection results.

2. The system of claim 1, wherein, The intrusion parameter calculation module (3) is connected with the terahertz pulse detection module (7), the post-processing module (4), the first single photon detector (8) and the second single photon detector (9) respectively, and is used for calculating the intrusion parameter of the eavesdropper Eve by using the measurement results, the detection results of the first single photon detector (8) and the second single photon detector (9) after obtaining the measurement results by the terahertz pulse detection module (7), and sending the initial results to the post-processing module (4) when the intrusion parameter meets the requirements.

3. The system of claim 1, wherein, The terahertz pulse generation module (5) includes a spontaneous parametric down-converter and a beam splitter, the converter is used to generate signal terahertz pulses and idle frequency light pulses, and the beam splitter is used to divide the terahertz pulses into two parts, send 2% of the terahertz pulses to the first single photon detector (8), and send the remaining terahertz pulses to the forward terahertz pulse transmission module (1), and send the idle frequency light pulses to the terahertz pulse detection module (7) for subsequent measurement.

4. The system of claim 1, wherein, The forward terahertz pulse transmission module (1) and the backward terahertz pulse transmission module (2) share two terahertz antennas, a first terahertz antenna, in the forward terahertz pulse transmission module (1), for transmitting the terahertz pulse sent by the terahertz pulse generation module (5) into the free space channel for transmission, and in the backward terahertz pulse transmission module (2), for receiving the terahertz pulse sent in the free space channel; A second terahertz antenna, in the forward terahertz pulse transmission module (1), for receiving the terahertz pulse sent in the free space channel, and in the backward terahertz pulse transmission module (2), for transmitting the terahertz pulse sent by the phase modulation module (6) into the free space channel for transmission.

5. The system of claim 1, wherein, The phase modulation module (6) comprises a beam splitter, a first terahertz switch, a modulator, and an amplifier; The beam splitter is used to divide the terahertz pulse sent by the forward terahertz pulse transmission module (1) into two parts, and send 1% of the terahertz pulse to the second single-photon detector (9), and send the remaining terahertz pulse to the first terahertz switch; The first terahertz switch is used to select whether the current mode is a communication mode or a sensing mode, and in the communication mode, the terahertz pulse is sent to the modulator; 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.

6. The system of claim 1, wherein, The post-processing module (4) is used to perform error correction and secret amplification on the initial results that meet the intrusion parameters obtained by the intrusion parameter calculation module (3), to obtain the final results, and in the sensing mode, the final results are also compared with the total error rate minimum threshold value, when the results are higher than the threshold value, it is determined that the object does not exist, and when the results are lower than the threshold value, it is determined that the object exists.

7. A method for entanglement-based terahertz quantum communication and sensing integration, which is communication and sensing between an Alice end and a Bob end, characterized in that, It comprises: The Alice end generates terahertz pulses and idler light pulses by using a spontaneous parametric down-conversion device, retains the idler light pulses locally for subsequent measurement, and divides the terahertz pulses into two parts, which are sent to a single-photon detector and the Bob end respectively; The Bob end sends the received terahertz pulses to the Alice end after extraction, modulation, and amplification in the communication mode, and sends the terahertz pulses reflected by the target to the Alice end in the sensing mode; Alice side in communication mode, using joint detection receiver to obtain the initial measurement results of terahertz pulse In the sensing mode, using a double zero difference detection receiver to obtain the initial measurement results of terahertz pulse ; After obtaining the initial measurement results, the Alice end calculates the intrusion parameters using the measurement results of the single-photon detector, and in the communication mode, performs error correction and secret amplification on the initial results that meet the intrusion parameters to obtain the final results, and in the sensing mode, compares the final results that meet the intrusion parameters after error correction and secret amplification with the total error rate minimum threshold value: If the final results are higher than the threshold value, it is determined that the target does not exist, If the final results are lower than the threshold value, it is determined that the target exists.

8. The method of claim 7, wherein, The Alice end utilizes spontaneous parametric down-conversion to generate terahertz pulses and visible idler light pulses, which are entangled according to the Wigner covariance matrix The formula is expressed as follows: ； wherein , , , denotes the variance of the terahertz pulse and the variance of the idler light pulse, denotes the variance of the thermal noise, , .

9. The method of claim 7, wherein, When the Bob end is in the communication mode, the received terahertz pulse is extracted, modulated and amplified and then sent to the Alice end, to achieve the following respectively: The extraction refers to that the Bob end first extracts the received signal mode A part of the signal mode is sent to a single-photon detector for channel monitoring via a beam splitter, and the remaining signal mode is sent into modulation, which is expressed as: ​ ； wherein represents a vacuum state, represents the reflection proportion of the beam splitter; The modulation: refers to the Bob end will receive the signal model The signal output after modulation by the modulator : ； wherein represents the bit value of the information to be transmitted at the Bob end; The amplification: refers to the Bob end to the signal model The amplified output signal model : ； wherein represents the gain of the amplifier, represents the noise state.

10. The method of claim 7, wherein, The Alice end uses a double null-difference detection receiver to obtain the initial measurement of the terahertz pulse which is expressed as: ； wherein is a density operator, is a trace operation, represents a terahertz pulse, represents an idler light pulse.

11. The method of claim 7, wherein, After the initial measurement result of the Alice end, the intrusion parameter is calculated by using the measurement result of the single-photon detector, and the formula for the communication mode and the formula for the sensing mode are respectively as follows: ； in, , These represent the time alignment accuracy and time misalignment accuracy between the terahertz pulse transmitted by Alice and the idler optical pulse, respectively. , These represent the time alignment accuracy and time misalignment accuracy between the terahertz pulse received by Bob and the idler optical pulse, respectively, in the communication mode. This represents the single-photon count rate of the single-photon detector at the Alice end. This indicates the single-photon count rate of the single-photon detector at the Bob end in communication mode; ； wherein, , respectively represent the time-aligned coincidence rate and the time-misaligned coincidence rate between the terahertz pulse and the idler light pulse received at the Bob side in the sensing mode, , respectively represent the time-aligned coincidence rate and the time-misaligned coincidence rate between the terahertz pulse and the idler light pulse received at the Bob side in the sensing mode, represents the single-photon counting rate of the single-photon detector at the Alice side, represents the single-photon counting rate of the single-photon detector at the Bob side in the sensing mode.

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