A TF-type QKD system based on a single single-photon detector and its implementation method

Abstract

The present invention discloses a TF-type QKD system based on a single single-photon detector and an implementation method thereof. In the measuring end Charlie, only a single single-photon detector is arranged to perform interference measurement on the optical pulse of the transmitting end, and it is proposed to use the response of the only single-photon detector as a valid event to implement TF-type QKD including SNS-TF-QKD, PM-QKD, NPP-QKD, etc. Compared with the existing TF-type QKD implementation method, the complexity of the QKD system can be reduced, and since the number of single-photon detectors can be reduced, the system cost can also be effectively reduced, which is conducive to the practical application and productization of the TF-type QKD system.

Description

Technical Field

[0001] The present invention relates to the field of quantum optics and quantum information technology, and in particular to a TF-type QKD system based on a single single-photon detector and an implementation method thereof. Background Art

[0002] With the development of science and technology, people in the fields of military, government affairs, finance, etc. pay more and more attention to information security issues. However, due to the development of quantum computers, the security of classical encryption technology is facing huge threats. Quantum key distribution (QKD) has advantages that classical cryptography cannot match. It can provide theoretically unconditionally secure key transmission.

[0003] In the past few decades, the field of QKD has made significant progress. QKD experiments over 400 kilometers of optical fiber and over 1000 kilometers of satellite-to-ground links have fully demonstrated the feasibility of long-distance point-to-point QKD. However, there are some basic limitations on the key transmission capabilities of relayless QKD, namely the PLOB bound proposed by Stefano Pirandola, Riccardo Laurenza, Carlo Ottaviani of the University of York, UK, and Leonardo Banchi of University College London, UK in 2017. The PLOB bound refers to the linear relationship between the coding rate R and the channel transmission rate η when the channel transmission rate is small, so this upper bound is called the linear coding rate upper bound of relayless QKD.

[0004] Traditional protocols such as the BB84 protocol cannot exceed the PLOB limit in terms of coding rate. Although the MDI-QKD protocol proposed later introduced a third party as a measurement relay, its coding rate still did not exceed the PLOB limit. In 2018, AJ Shields and others from Toshiba Europe Research Institute proposed a new type of measurement device-independent quantum key distribution protocol-the dual-field quantum key distribution (TF-QKD) protocol. Unlike the coding rates R~O(η) of the traditional BB84 protocol and the MDI-QKD protocol, the coding rate of the TF-QKD protocol is The TF-type QKD protocols developed on the basis of the TF-QKD protocol include sending-or-not-sending TF-QKD scheme (Sending-or-not-sending TF-QKD, SNS-TF- QKD), phase-matching QKD scheme (phase-matching QKD, PM- QKD), no phase-post-selected QKD scheme (no phase-post-selected- QKD, NPP-QKD), etc.

[0005] During the implementation of the TF-type QKD protocol, Alice and Bob send light pulses to a third party, Charlie, for measurement. In existing schemes, Charlie's measurement process uses two detectors, located on both sides of the spectrometer. If only one detector responds during the detection process, the event is regarded as a valid event, and the valid event is post-processed to obtain the final key.

[0006] The detectors used in the Charlie measurement stations in the existing TF-QKD protocols are all single-photon detectors, especially in some scenarios with high coding rate requirements, superconducting nanowire single-photon detectors are also required. However, due to the complex chip process of superconducting nanowire single-photon detectors, they need to operate under extremely low temperature conditions and are extremely sensitive to vibration, static electricity, temperature, etc., making the TF-QKD system more complex and expensive, so it is necessary to improve the above technology. Summary of the invention

[0007] In view of the above-mentioned problems existing in the prior art, the present invention discloses a TF-type QKD system based on a single single-photon detector and an implementation method thereof, in which only a single single-photon detector is set in the measuring end Charlie to perform interference measurement on the light pulse of the transmitting end, and it is proposed to use the response of the only single-photon detector as a valid event to implement TF-type QKD including SNS-TF-QKD, PM-QKD, NPP-QKD, etc. Compared with the existing TF-type QKD implementation method, the complexity of the QKD system can be reduced, and since the number of single-photon detectors can be reduced, the system cost can also be effectively reduced, which is conducive to the practical application and productization of the TF-type QKD system.

[0008] Specifically, the TF-type QKD implementation method based on a single single-photon detector of the present invention may include a state preparation step, a quantum state measurement step, a screening step, a parameter estimation and a post-processing step;

[0009] The state preparation step is used by the transmitting end Alice and Bob to prepare the optical pulse according to the TF-type QKD protocol;

[0010] The quantum state measurement step is used to perform interference measurement on the light pulse by the measuring end Charlie, wherein only a single single-photon detector is provided in the measuring end Charlie for the interference measurement, and the response of the single single-photon detector is used as a valid event;

[0011] The screening step is used for the sending end to publish and screen the state preparation data corresponding to the valid event and obtain the original key;

[0012] The parameter estimation and post-processing steps are used to perform parameter estimation using the screened state preparation data, and to obtain the final key using the parameter estimation result and the original key.

[0013] Furthermore, in the screening step, the measuring end Charlie announces the valid event, the transmitting end publishes the state preparation data corresponding to the valid event through a public channel according to the TF-type QKD protocol and screens it, and obtains the original key using the bits corresponding to the signal state light pulse.

[0014] Furthermore, the state preparation data includes one or more of intensity, basis vector and phase information.

[0015] Furthermore, the TF-type QKD protocol is an SNS-TF-QKD protocol, and in the state preparation step, the transmitter transmits the signal with probability p x and 1-p x Selecting to prepare the light pulses under an X-window and a Z-window; and,

[0016] Under the X-window, the sender i (i=0, 1, 2) Randomly prepare phase-randomized coherent state light pulses The light pulse is a vacuum pulse, a light pulse and With strength μ 1 and μ 2 , μ 1 <μ 2 ;

[0017] Under the Z-window, the transmitter randomly prepares coherent state light pulses with probabilities ∈ and 1-∈ and vacuum pulses Used to represent different bits, where the bits are 0 and 1.

[0018] Furthermore, in the screening step, the transmitter publishes the window corresponding to the valid event, and also publishes the intensity information and the phase information when the X-window is selected at the same time, and uses the bit information corresponding to the valid event to form the original key when the Z-window is selected at the same time.

[0019] Furthermore, in the parameter estimation and post-processing steps:

[0020] Defining a Collection and The collection Used to meet |θ A -θ B |≤Δ / 2 coherent state light pulse gather Used to meet |θ A -θ B -π|≤Δ / 2 coherent state light pulse And the collection and The number of light pulses in and The corresponding number of valid events is recorded as and Among them, θ A and θ B are the phase values ​​of the optical pulses of Alice and Bob at the transmitting end, respectively, and Δ is a small value set based on experience;

[0021] Single-photon light pulses in the Z-window The lower bound of the count rate is:

[0022]

[0023] in. Count rate S jk =n jk / N jk , N jk Select a coherent state for the sender Alice And the sender Bob chooses the coherent state The count of time, n jk is the number of valid events, j, k = 0, 1, 2, z;

[0024] The single photon state light pulse Bit Error Rate The upper bound of is:

[0025] in,

[0026] And the final bit rate in, is z The probability of emitting a single-photon light pulse in Z and E Z are the counting rate and bit error rate under the Z-window respectively, and f is the error correction efficiency coefficient.

[0027] Preferably, in the parameter estimation and post-processing steps:

[0028] make

[0029] S is obtained by statistical prediction 1 , S 2 , S00 , T Δ Corresponding expected value upper bound estimate and lower bound estimate S 1 , S 2 , S 00 , T Δ Among them, the expected value of the counting rate is The lower bound estimate of And the expected bit error rate The upper bound estimate of

[0030] The present invention also relates to a TF-type QKD system based on a single single-photon detector, which includes transmitting ends Alice and Bob, and a measuring end Charlie;

[0031] The transmitting ends Alice and Bob are configured to prepare optical pulses according to a TF-type QKD protocol, screen state preparation data and an original key according to valid events, perform parameter estimation using the screened state preparation data, and obtain a final key using the parameter estimation result and the original key;

[0032] The measurement end Charlie is provided with only a single single-photon detector to perform interference measurement on the light pulse, and the response of the single single-photon detector is used as a valid event.

[0033] Further, the state preparation data includes one or more of intensity, basis vector and phase information; and / or, the measuring end Charlie is configured to announce the valid event; the transmitting end is configured to publish the state preparation data corresponding to the valid event through a public channel according to the TF-type QKD protocol.

[0034] Further, the TF-type QKD protocol is an SNS-TF-QKD protocol;

[0035] The senders Alice and Bob are configured to x and 1-p x Selecting to prepare the light pulse under the X-window and the Z-window;

[0036] Among them, under the X-window, the sending end uses probability p i (i=0, 1, 2) Randomly prepare phase-randomized coherent state light pulses The light pulse is a vacuum pulse, a light pulse and With strength μ 1 and μ 2 , μ 1 <μ 2 ; Under the Z-window, the transmitter randomly prepares coherent state light pulses with probability ∈ and 1-∈ and vacuum pulses Used to represent different bits.

[0037] Furthermore, the sending ends Alice and Bob are also configured to:

[0038] Defining a Collection and The collection Used to meet |θ A -θ B |≤Δ / 2 coherent state light pulse gather Used to meet |θ A -θ B -π|≤Δ / 2 coherent state light pulse And the collection and The number of light pulses in and The corresponding number of valid events is recorded as and Among them, θ A and θ B are the phase values ​​of the optical pulses of Alice and Bob at the transmitting end, respectively, and Δ is a small value set based on experience;

[0039] Single-photon light pulses in the Z-window The lower bound of the count rate is:

[0040]

[0041] in. Count rate S jk =n jk / N jk , N jk Select a coherent state for the sender Alice And the sender Bob chooses the coherent state The count of time, n jk is the number of valid events, j, k = 0, 1, 2, z;

[0042] The single photon state light pulse Bit Error Rate The upper bound of is:

[0043] in.

[0044] And the final bit rate in, is z The probability of emitting a single-photon light pulse in Z and E Z are the counting rate and bit error rate under the Z-window respectively, and f is the error correction efficiency coefficient.

[0045] Preferably, the sending ends Alice and Bob are further configured to:

[0046] make

[0047] S is obtained by statistical prediction 1 , S 2 , S 00 , T Δ Corresponding expected value upper bound estimate and lower bound estimate S 1 , S 2 , S 00 , T Δ ;

[0048] Expected count rate The lower bound estimate of

[0049] BER Expected Value The upper bound estimate of BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. It is obvious that the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 The measurement end Charlie of the TF-type QKD system based on a single single-photon detector used in the present invention is schematically shown. DETAILED DESCRIPTION

[0053] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so as to fully convey the spirit of the present invention to those skilled in the art to which the present invention belongs. Therefore, the present invention is not limited to the embodiments disclosed herein.

[0054] Figure 1 The measurement end Charlie of the TF-type QKD system based on a single single-photon detector used in the present invention is schematically shown, wherein only a single single-photon detector is provided, which is located on one side of the spectroscope and is used for quantum state measurement in the TF-type QKD.

[0055] According to the present invention, the TF-type QKD implementation method based on a single single-photon detector may include the steps of state preparation, quantum state measurement, screening, parameter estimation and post-processing.

[0056] In the state preparation step, the transmitting end Alice and Bob randomly prepare optical pulses according to the TF-type QKD protocol and send them to the measuring end Charlie. The optical pulses can be signal state optical pulses or decoy state optical pulses.

[0057] Preferably, the TF-type QKD protocol may include the SNS-TF-QKD protocol, the PM-QKD protocol and the NPP-QKD protocol.

[0058] In the quantum state measurement step, the measuring end Charlie uses a single single-photon detector to perform interference measurement on the light pulse, records the detection result and broadcasts it to the sending ends Alice and Bob through a public channel. Those skilled in the art will understand that in the present invention, the detection result will only include the response of the single single-photon detector, which is different from the detection result of the prior art that includes the response of two single-photon detectors.

[0059] In the screening step, after interferometric measurement is performed on N pairs of optical pulses to obtain a series of detection results, the measuring end Charlie announces the valid event that causes the unique single-photon detector response based on the detection results, and the sending ends Alice and Bob publish the state preparation data corresponding to the valid event through a public channel according to the TF-type QKD protocol, which includes, for example, intensity, basis vector or phase information, to allow screening based on the published state preparation data, and allow the sending ends Alice and Bob to use the bits corresponding to the signal state optical pulses to obtain the original key.

[0060] In the parameter estimation and post-processing steps, the senders Alice and Bob use the screened data to perform parameter estimation, which includes, for example, single-photon state count rate, phase reversal bit error rate, etc. The senders Alice and Bob use the original key to perform error correction, use the parameter estimation results and the coding rate formula to calculate the privacy amplification factor, and perform privacy amplification on the corrected key according to the privacy amplification factor to obtain the final key.

[0061] In order to better understand the present invention, the working process of the TF-type QKD implementation method based on a single single-photon detector according to the present invention is described in detail below by taking the four-intensity SNS-TF-QKD protocol as an example.

[0062] In the state preparation step, the transmitters Alice and Bob randomly select to prepare optical pulses in the X-window (decoy state window) or Z-window (signal state window) and send them to the measuring terminal Charlie, where the probability of using the X-window is denoted as px and the probability of using the Z-window is denoted as 1-px.

[0063] When selecting the X-window, the sender Alice (Bob) sends i (i=0,1,2) Randomly generate coherent light pulses and sent to the measurement end Charlie, where the light pulse With randomized phase, and light pulses is a vacuum pulse, a light pulse and With strength μ 1 and μ 2 (μ 1 <μ 2 ).

[0064] When the Z-window is selected, the transmitter Alice (Bob) randomly prepares coherent light pulses and vacuum pulses to represent bits 1 / 0 or 0 / 1. Among them, for coherent light pulses The probabilities of and vacuum state pulses can be denoted as ∈ and 1-∈ respectively.

[0065] In the quantum state measurement step, the measuring end Charlie uses a unique single-photon detector to perform interference measurement on the received light pulse and records the detection results, wherein when the unique single-photon detector responds, it is recorded as a valid event, and then the detection result (i.e., whether the unique single-photon detector responds) is broadcast to the sending ends Alice and Bob through a public channel.

[0066] In the screening step, after obtaining N detection results, the senders Alice and Bob may publish state preparation data corresponding to valid events, such as window information (X-window or Z-window) selected corresponding to valid events.

[0067] Corresponding to the valid event that the senders Alice and Bob simultaneously select the X-window, the senders Alice and Bob also publish the intensity information and the phase information.

[0068] Corresponding to the fact that the sender Alice and Bob simultaneously select valid events of the Z-window, the original keys of the sender Alice and Bob are formed using the bit information corresponding to the valid events.

[0069] Among them, the counting rate S jk =n jk / N jk , n jk is the number of valid events, N jk Select the coherent state for Alice And Bob chooses the coherent state The count at time, j, k = 0, 1, 2, z.

[0070] In the parameter estimation and post-processing steps, the senders Alice and Bob use the screened data to perform parameter estimation, and based on the parameter estimation results, perform post-processing operations such as error correction and confidentiality enhancement on the original key to obtain the final key.

[0071] Specifically, in order to achieve effective estimation of the bit error rate, the present invention defines a set and Among them, the collection To satisfy the relationship |θ A -θ B |≤Δ / 2 coherent state light pulse gather To satisfy the relationship |θ A -θ B -π|≤Δ / 2 coherent state light pulse And collection and The number of light pulses in and The corresponding valid event numbers are and θ A and θ B are the phase values ​​of the optical pulses prepared for Alice and Bob respectively, and Δ is a small value set based on experience.

[0072] Therefore, the single photon count rate of Alice and Bob at the sending end is The lower bound and phase reversal bit error rate The upper bound of is estimated.

[0073] In the present invention, phase randomized coherent state light pulses Using the probability combination form of number states represents, where μ j is the intensity, j=0, 1, 2, z.

[0074] Therefore, when Alice does not emit a light pulse, Bob emits a coherent light pulse. When , the corresponding state can be expressed as

[0075] From this we can get the state The corresponding lower bound of the count rate is:

[0076]

[0077] Among them, S 0k For light source The corresponding count rate, S 00 is the counting rate when both Alice and Bob emit vacuum state signals (i.e., vacuum source).

[0078] Similar to the state The corresponding lower bound of the count rate is:

[0079]

[0080] Among them, S j0 For light source The corresponding count rate.

[0081] therefore, The lower bound of its count rate is

[0082] Bit Error Rate The upper bound of in

[0083] Calculate the final bitrate in is z The probability of emitting a single-photon light pulse in Z and E Z are the counting rate and bit error rate under the Z-window respectively, and f is the error correction efficiency coefficient.

[0084] In a preferred example, considering the statistical fluctuation effect caused by the limited number of optical pulses, Use statistical prediction related conclusions (such as Chernoff Bound and other methods) to obtain the observed quantity S 1 , S 2 , S 00 , T Δ The upper bound estimate of the corresponding expected value and lower bound estimate S 1 , S 2 , S 00 , T Δ .

[0085] At this time, the expected value of the count rate is The lower bound estimate of is:

[0086]

[0087] Expected value of bit error rate The upper bound of is estimated to be:

[0088]

[0089] Using the estimated value of the expected value, we can further obtain the prediction result of the corresponding true value of the corresponding light pulse, that is, the lower bound of the number of single-photon state counts corresponding to the remaining part after error correction is completed. n 1 , and the upper bound of the bit error rate And thus the final code length is obtained.

[0090] At the same time, the present invention also discloses a TF-type QKD system based on a single single-photon detector, which includes transmitting ends Alice and Bob, and a measuring end Charlie, and can realize the above-mentioned TF-type QKD process based on a single single-photon detector.

[0091] Specifically, in the QKD system, the transmitters Alice and Bob are used to prepare optical pulses according to the TF-type QKD protocol, prepare data and original keys according to the state screening of valid events, perform parameter estimation using the screened state preparation data, and obtain the final key using the parameter estimation results and the original key.

[0092] The measurement end Charlie is provided with only a single single photon detector for interferometric measurement of the optical pulse. In the present invention, the response of the single single photon detector is taken as a valid event.

[0093] When the measuring end Charlie announces a detected valid event after N interference measurements, the sending end can publish the state preparation data corresponding to the valid event through a public channel according to the protocol, which is, for example, one or more of intensity, basis vector and phase information.

[0094] When the system is used to implement the SNS-TF-QKD protocol, the senders Alice and Bob can x and 1-p x The light pulses are prepared selectively under the X-window and the Z-window.

[0095] Under the X-window, the sender can send i (f=0, 1, 2) Randomly prepare phase-randomized coherent state light pulses The light pulse is a vacuum pulse, a light pulse and With strength μ 1 and μ 2 , μ 1 <μ 2 .

[0096] Under the Z-window, the transmitter can randomly prepare coherent state light pulses with probability ∈ and 1-∈ and vacuum pulses Used to represent different bits, such as 0 / 1 or 1 / 0.

[0097] After the sender screens the state preparation data according to the valid events and obtains the original key, it can perform parameter estimation and data post-processing.

[0098] To this end, the senders Alice and Bob can also define a set and The collection Used to meet |θ A -θ B |≤Δ / 2 coherent state light pulse gather Used to meet |θ A -θ B -π|≤Δ / 2 coherent state light pulse And will collect and The number of light pulses in and The corresponding number of valid events is recorded as and Among them, θ A and θ B are the phase values ​​of the optical pulses of Alice and Bob at the transmitting end, respectively, and Δ is a small value set based on experience;

[0099] Single-photon light pulses in the Z-window The lower bound of the count rate is:

[0100]

[0101]

[0102]

[0103] Count rate S jk =n jk / N jk , N jk Select the coherent state for the sender Alice And the sender Bob chooses the coherent state The count of time, n jk is the number of valid events, j, k = 0, 1, 2, z.

[0104] Single-photon light pulses Bit Error Rate The upper bound of is:

[0105]

[0106] in,

[0107] Final bit rate

[0108] in, is z The probability of emitting a single-photon light pulse in Z and E Z are the counting rate and bit error rate under the Z-window respectively, and f is the error correction efficiency coefficient.

[0109] In a preferred example, the sending ends Alice and Bob can also be configured to use And through statistical prediction, we get S 1 , S 2 , S 00 , T Δ Corresponding expected value upper bound estimate and lower bound estimate S 1 , S 2 , S 00 , T Δ .

[0110] From this, the expected value of the count rate can be obtained The lower bound estimate of And the expected bit error rate The upper bound estimate of

[0111] In summary, the present invention proposes a method and system for realizing TF-type QKD with the help of only a single single-photon detector, in which only a single single-photon detector is set in the measuring end Charlie to perform interference measurement on the light pulse of the transmitting end, and the response of the only single-photon detector is used as the valid event, thereby realizing TF-type QKD including SNS-TF-QKD, PM-QKD, NPP-QKD, etc. Compared with the existing TF-type QKD implementation method, the complexity of the QKD system can be reduced, and since the number of single-photon detectors can be reduced, the system cost can also be effectively reduced, which is conducive to the practical application and productization of the TF-type QKD system.

[0112] Although the present invention has been described above through specific embodiments in conjunction with the accompanying drawings, those skilled in the art will readily recognize that the above embodiments are merely exemplary and are used to illustrate the principles of the present invention, and do not limit the scope of the present invention. Those skilled in the art may make various combinations, modifications and equivalent substitutions to the above embodiments without departing from the spirit and scope of the present invention.

Claims

1. A TF-type QKD implementation method based on a single single-photon detector, which includes a state preparation step, a quantum state measurement step, a screening step, a parameter estimation step and a post-processing step; The state preparation step is used by the transmitting end Alice and Bob to prepare the optical pulse according to the TF-type QKD protocol; The quantum state measurement step is used to perform interference measurement on the light pulse by the measuring end Charlie, wherein: The measuring end Charlie is provided with only a single single-photon detector for the interference measurement, and the response of the single single-photon detector is taken as a valid event; The screening step is used for the sending end to publish and screen the state preparation data corresponding to the valid event and obtain the original key; The parameter estimation and post-processing steps are used to perform parameter estimation using the screened state preparation data, and to obtain the final key using the parameter estimation result and the original key.

2. The TF-based QKD implementation method according to claim 1, wherein: In the screening step, the measuring end Charlie announces the valid event, the sending end publishes the state preparation data corresponding to the valid event through a public channel according to the TF-type QKD protocol and screens it, and obtains the original key using the bits corresponding to the signal state light pulse.

3. The TF-based QKD implementation method as claimed in claim 2, wherein: The state preparation data includes one or more of intensity, basis vector and phase information.

4. The TF-based QKD implementation method according to claim 1, wherein: The TF-type QKD protocol is an SNS-TF-QKD protocol, and in the state preparation step, the transmitting end uses probability p x and 1-p x Selecting to prepare the light pulses under an X-window and a Z-window; and, Under the X-window, the sender i (i=0, 1, 2) Randomly prepare phase-randomized coherent state light pulses The light pulse is a vacuum pulse, a light pulse and They have intensities μ1 and μ2, μ1<μ2; Under the Z-window, the transmitter randomly prepares coherent state light pulses with probabilities ∈ and 1-∈ and vacuum pulses Used to represent different bits.

5. The TF-based QKD implementation method as claimed in claim 4, wherein: In the screening step, the transmitter publishes the window corresponding to the valid event, and also publishes the intensity information and the phase information when the X-window is selected at the same time, and uses the bit information corresponding to the valid event to form the original key when the Z-window is selected at the same time.

6. The TF-based QKD implementation method as claimed in claim 5, wherein: In the parameter estimation and post-processing steps: Defining a Collection and The collection Used to meet |θ A -θ B |≤Δ / 2 coherent state light pulse gather Used to meet |θ A -θ B -π|≤Δ / 2 coherent state light pulse And the collection and The number of light pulses in and The corresponding number of valid events is recorded as and Among them, θ A and θ B are the phase values ​​of the optical pulses of Alice and Bob at the transmitting end, respectively, and Δ is a small value set based on experience; Single-photon light pulses in the Z-window The lower bound of the count rate is: in, Count rate S jk =n jk / N jk , N jk Select a coherent state for the sender Alice And the sender Bob chooses the coherent state The count of time, n jk is the number of valid events, j, k = 0, 1, 2, z; The single photon state light pulse Bit Error Rate The upper bound of is: in, And the final bit rate in, is z The probability of emitting a single-photon light pulse in Z and E Z are the counting rate and bit error rate under the Z-window respectively, and f is the error correction efficiency coefficient.

7. The TF-based QKD implementation method according to claim 6, wherein: In the parameter estimation and post-processing steps: make S1, S2, S are obtained by statistical prediction 00 , T Δ Corresponding expected value upper bound estimate and lower bound estimate S 1, S 2, S 00 , T Δ ; Expected count rate The lower bound estimate of BER Expected Value The upper bound estimate of 8. A TF-type QKD system based on a single single-photon detector, comprising transmitting ends Alice and Bob, and a measuring end Charlie; The transmitting ends Alice and Bob are configured to prepare optical pulses according to a TF-type QKD protocol, screen state preparation data and an original key according to valid events, perform parameter estimation using the screened state preparation data, and obtain a final key using the parameter estimation result and the original key; The measurement end Charlie is provided with only a single single-photon detector to perform interference measurement on the light pulse, and the response of the single single-photon detector is used as a valid event.

9. The TF-type QKD system as claimed in claim 8, wherein: The state preparation data includes one or more of intensity, basis vector and phase information; and / or, The measuring terminal Charlie is configured to announce the valid event; The transmitting end is configured to publish state preparation data corresponding to a valid event through a public channel according to the TF-type QKD protocol.

10. The TF-type QKD system according to claim 9, wherein: The TF-type QKD protocol is the SNS-TF-QKD protocol; The transmitting ends Alice and Bob are configured to select to prepare the optical pulses in the X-window and the Z-window with probabilities px and 1-px; Among them, under the X-window, the sending end uses probability p i (i=0, 1, 2) Randomly prepare phase-randomized coherent state light pulses The light pulse is a vacuum pulse, a light pulse and respectively have intensities μ1 and μ2, μ1<μ2; under the Z-window, the transmitter randomly prepares coherent state light pulses with probabilities ∈ and 1-∈ and vacuum pulses Used to represent different bits.

11. The TF-type QKD system according to claim 10, wherein: The sending ends Alice and Bob are also configured to: Defining a Collection and The collection Used to meet |θ A -θ B |≤Δ / 2 coherent state light pulse gather Used to meet |θ A -θ B -π|≤Δ / 2 coherent state light pulse And the collection and The number of light pulses in and The corresponding number of valid events is recorded as and Among them, θ A and θ B are the phase values ​​of the optical pulses of Alice and Bob at the transmitting end, respectively, and Δ is a small value set based on experience; Single-photon light pulses in the Z-window The lower bound of the count rate is: in, Count rate S jk =n jk / N jk , N jk Select a coherent state for the sender Alice And the sender Bob chooses the coherent state The count of time, n jk is the number of valid events, j, k = 0, 1, 2, z; The single photon state light pulse Bit Error Rate The upper bound of is: in, And the final bit rate in, is z The probability of emitting a single-photon light pulse in Z and E Z are the counting rate and bit error rate under the Z-window respectively, and f is the error correction efficiency coefficient.

12. The TF-type QKD system according to claim 11, wherein: The sending ends Alice and Bob are also configured to: make S1, S2, S are obtained by statistical prediction 00 , T Δ Corresponding expected value upper bound estimate and lower bound estimate S 1, S 2, S 00 , T Δ ; Expected count rate The lower bound estimate of BER Expected Value The upper bound estimate of

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