CN112073189A - Independent quantum key distribution method and system for continuous variable measurement equipment - Google Patents

Abstract

The invention provides a method and a system for independent quantum key distribution based on continuous variable measurement equipment, which comprises the following steps: step M1: the sending terminal and the receiving terminal carry out quantum signal preparation and coding; step M2: the sending end and the receiving end transmit the quantum signals to the measuring end, the measuring end interferes the quantum signals, and the interfered quantum signals are detected; step M3: performing information decoding on the detected quantum signals; step M4: preparing quantum signals (X) according to the stored signals according to the transmitting end and the receiving end_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DPerforming parameter evaluation; step M5: and carrying out data negotiation according to the decoded quantum signals and carrying out privacy enhancement according to parameter evaluation.

Description

Independent quantum key distribution method and system for continuous variable measurement equipment

Technical Field

The invention relates to the technical field of quantum secret communication, in particular to a method and a system for distributing independent quantum keys of continuous variable measuring equipment, and more particularly relates to a novel protocol for distributing independent quantum keys of measuring equipment, which is realized based on a continuous variable coherent state.

Background

The continuous variable quantum key distribution technology can utilize a coherent detection method to ensure that two communication parties far away from each other realize key distribution with information theory safety. As the continuous variable quantum key distribution technology inherits many advantages of classical coherent optical communication, has higher channel capacity and convergence with the classical optical communication, and is widely concerned by a plurality of mainstream quantum cryptography research organizations in the world. Various protocols have been proposed by researchers in various countries for continuous variable quantum key distribution so far, and the most widely applied protocol is gaussian modulation coherent state continuous variable quantum key distribution protocol, which has been proved to be unconditionally safe in theory. At present, the continuous variable quantum key distribution technology becomes an important branch of the whole quantum secret communication technology, and commercial products appear in the market, and the market is advanced towards industrialization.

However, although gaussian modulation coherent state continuous variable quantum key distribution has theoretically proven the security, the non-idealities of various actual devices of the system may introduce actual security holes and related attacks, such as local oscillation attack, calibration attack, wavelength attack, and the like, so that the system operation may no longer have unconditional integrity described in theory. In order to remove the actual security hole, researchers provide a continuous variable measurement device independent quantum key distribution (CV-MDI-QKD) scheme, so that the actual security problem caused by factors such as an imperfect measuring party can be removed. However, when such schemes are actually operated, if an effective security key is generated, the efficiency of the coherent detection of the continuous variable quantum used is required to reach an almost ideal condition, which greatly limits the practical application and popularization of the CV-MDI-QKD. In fact, to date, there has been little report of a truly practical CV-MDI-QKD experiment.

Patent document CN111404681A (application No.: 202010176435.7) discloses a continuous variable measurement device-independent quantum key distribution method, system, and medium, including: step A: according to the frequency offset estimation technology, estimating the frequency offset between the two parties of the method and the intermediate party by means of a pilot signal, and realizing frequency offset compensation; and B: according to the phase estimation technology and the data disclosed by both legal parties, the correlation coefficient between the received data and the intermediate party is calculated, the phase drift introduced by each channel is estimated, and the phase compensation of the quantum signals is realized.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method and a system for independent quantum key distribution based on continuous variable measurement equipment.

The invention provides a method for distributing independent quantum keys based on continuous variable measurement equipment, which comprises the following steps:

step M1: the sending terminal and the receiving terminal carry out quantum signal preparation and coding to obtain quantum signals (X) of the sending terminal and the receiving terminal_A,P_A) And (X)_B,P_B)；

Step M2: the sending end and the receiving end transmit the quantum signals to the measuring end, the measuring end interferes the quantum signals, and the interfered quantum signals are detected to obtain a measured value X_CAnd P_D；

Step M3: carrying out information decoding on the detected quantum signals;

step M4: preparing quantum signals (X) according to the preserved preparation of a transmitting terminal and a receiving terminal_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DPerforming parameter evaluation;

step M5: and carrying out data negotiation according to the decoded quantum signals and carrying out privacy enhancement according to parameter evaluation.

Preferably, the step M1 includes:

step M1.1: respectively obtaining binary true random number strings R1 and R2 according to binary true random number generators of a sending end and a receiving end;

step M1.2: selecting the encoding coherent state quantum signals of the corresponding bases according to binary true random numbers R1 and R2;

step M1.3: and adjusting the coherent state quantum signal through an adjustable attenuator to optimize the finally generated safe key rate.

Preferably, said step M1.2 comprises: the sending end selects an encoding base X or P according to a random number in the binary true random number R1, wherein 0 selects an X base, and 1 selects a P base; based on the selection of the coding bases in the binary true random number R1, selecting the coding coherent state quantum information of the corresponding bases according to the random number in the binary true random number R2;

when the encoding base of the binary true random number R1 is X base, and when the binary true random number R2 is 0, then the coherent state | α is selected>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^πi>(ii) a When the coding base of the binary true random number R1 is P base, and when the binary true random number R2 is 0, the coherent state | α e is selected^πi/2>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^3πi/2>Where a denotes the amplitude of the coherent quantum signal and i denotes the imaginary unit.

Preferably, the step M2 includes:

step M2.1: the sending end and the receiving end simultaneously send the encoded quantum signals to the measuring end through a quantum channel;

step M2.2: the measuring end interferes the quantum signal through the optical beam splitter;

step M2.3: coherent detection is carried out on the interfered quantum signals to respectively obtain measured values X_CAnd P_D。

Preferably, said step M2.3 comprises: the sending end and the receiving end encode the key information on discrete phases of continuous variable signals which are matched with each other, the key information cannot be revealed by publishing the information of the measuring end, the irrelevant quantum key distribution of the measuring equipment is realized by utilizing a quantum homodyne detector with low preset efficiency, and measured values X are respectively obtained_CAnd P_D。

Preferably, the step M3 includes:

step M3.1: the sending end and the receiving end both disclose respective random number strings R1, and respectively store the random number strings R1 with the consistent sending end and receiving end and the measured value X_CAnd P_DSatisfy { X ] for the same X radicals, respectively_C∈R:-_C≤X_C≤_COr { P for the same P base_D∈R:-_D≤P_D≤_DR2 of the sending terminal random number string R1 and R2 corresponding base coded coherent quantum signals meeting the judgment conditions are marked as K_AAnd the coherent quantum signals coded by the corresponding bases of the receiving end random number strings R1 and R2 are marked as K_B；

Wherein R represents a real number, X_CRepresenting the X-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Cthe judgment threshold of the detected X component is represented, namely, whether the result published by a measuring party meets the judgment threshold range is judged, a sending party and a receiving party respectively judge whether the currently prepared and coded signals can generate effective keys, subscript C represents the quantum signal modulus C detected by a Hom quantum homodyne measurer, and subscript P represents that the quantum signal modulus C and the P are respectively C_DRepresenting the P-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Da decision threshold representing the detected P component;

step M3.2: when the random number strings R1 of the sending end and the receiving end are correspondingly selected to be P base, the receiving end turns over K_BBit, the sending end and the receiving end form consistent key bits K and K';

step M3.3: the sending end and the receiving end respectively reserve the unsatisfied K_AAnd K_BThe transmitting end does not satisfy K_AThe coherent state quantum signal of different bases is denoted as (X)_A,P_A) Will receive end not satisfy K_BThe coherent state quantum signal of different bases is denoted as (X)_B,P_B)。

Preferably, the step M4 includes: the transmitting terminal and the receiving terminal prepare the quantum signal (X) according to the stored_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DAnd performing parameter evaluation.

Preferably, the step M5 includes:

step M5.1: negotiating the generated key bits K and K' by the transmitting end and the receiving end through a classical channel to obtain a consistent bit string;

step M5.2: and calculating a compression factor according to the parameters obtained by parameter evaluation, and performing privacy enhancement operation on the obtained bit string to finally obtain a string of shared security keys.

Preferably, the parameter evaluation comprises: evaluating channel over-noise and channel transmittance in the communication process, and evaluating the leaked information quantity and the mutual information quantity of a legal party; and judging whether the secret key rate is greater than zero or not according to the parameter evaluation, namely whether a legal party can obtain the safety secret key or not, and giving up communication and restarting when the secret key rate is less than zero.

The invention provides a device-independent quantum key distribution system based on continuous variable measurement, which comprises:

module M1: the sending terminal and the receiving terminal carry out quantum signal preparation and coding to obtain quantum signals (X) of the sending terminal and the receiving terminal_A,P_A) And (X)_B,P_B)；

Module M2: the sending end and the receiving end transmit the quantum signals to the measuring end, the measuring end interferes the quantum signals, and the interfered quantum signals are detected to obtain a measured value X_CAnd P_D；

Module M3: carrying out information decoding on the detected quantum signals;

module M4: preparing quantum signals (X) according to the preserved preparation of a transmitting terminal and a receiving terminal_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DPerforming parameter evaluation;

module M5: and carrying out data negotiation according to the decoded quantum signals and carrying out privacy enhancement according to parameter evaluation.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention is different from the previous CV-MDI-QKD protocol, because the invention adopts a phase matching coding method based on discrete modulation, the invention can directly generate a discretized binary original key, thereby directly carrying out negotiation and confidentiality enhancement processing by the existing post-processing algorithm method based on the discrete variable technology, reducing the realization complexity of the existing CVQKD system and improving the system performance from the post-processing angle.

2. The invention adopts a discrete phase matching method, has lower necessary detection efficiency (the necessary detection efficiency refers to the minimum quantum homodyne detector efficiency required by obtaining the security key rate under a specific transmission distance), so the protocol can still obtain the security key under the condition of actually lower detector efficiency, such as the detection efficiency of 0.6, but the traditional Gaussian modulation coherent CV-MDI-QKD can not obtain the security key.

3. The method for distributing the independent quantum key of the continuous variable measurement equipment based on the phase matching can allow the distribution of the super-long distance secure key in an ideal asymmetric channel mode, and can provide a practical and available solution for the distribution of the independent continuous variable quantum key of the long-distance measurement equipment in the later period.

4. Although the safe transmission distance is not particularly high in the symmetrical channel mode because of the reduction of the channel capacity caused by self discrete phase matching, the invention has the advantages that the safe transmission distance can be realized by utilizing the existing detector (namely the efficiency of the detector is required to be very low), and the safe continuous variable quantum key distribution method can be suitable for short-distance high-repetition-frequency application scenes such as access networks and building-to-building and realizes the high-speed actual safe continuous variable quantum key distribution among users.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic diagram of a method for distributing independent quantum keys of a continuous variable measurement device based on phase matching according to the present invention;

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

Aiming at the defects in the prior art, the invention aims to provide a phase matching-based independent quantum key distribution method for continuous variable measurement equipment, which is used for solving the problem that the practical realization is seriously limited due to the high requirement of the existing Gaussian modulation coherent CV-MDI-QKD on the efficiency of a quantum balance homodyne detector.

Example 1

The invention provides a method for distributing independent quantum keys based on continuous variable measurement equipment, which comprises the following steps:

step M1: the sending terminal and the receiving terminal carry out quantum signal preparation and coding to obtain quantum signals (X) of the sending terminal and the receiving terminal_A,P_A) And (X)_B,P_B)；

Step M2: the sending end and the receiving end transmit the quantum signals to the measuring end, the measuring end interferes the quantum signals, and the interfered quantum signals are detected to obtain a measured value X_CAnd P_D；

Step M3: carrying out information decoding on the detected quantum signals;

step M4: preparing quantum signals (X) according to the preserved preparation of a transmitting terminal and a receiving terminal_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DPerforming parameter evaluation;

step M5: and carrying out data negotiation according to the decoded quantum signals and carrying out privacy enhancement according to parameter evaluation.

Specifically, the step M1 includes:

step M1.1: respectively obtaining binary true random number strings R1 and R2 according to binary true random number generators of a sending end and a receiving end;

step M1.2: selecting the encoding coherent state quantum signals of the corresponding bases according to binary true random numbers R1 and R2;

step M1.3: and adjusting the coherent state quantum signal through an adjustable attenuator to optimize the finally generated safe key rate.

The optimization is to maximize the key rate, i.e., X_A,P_AAnd X_B,P_BThe values of (a) take an optimum value, which depends on the intensity of the different signal lights or on the amplitude alpha (hereinafter you will be referred to as a), which is adjusted by adjusting the attenuator, which is related to the final key rate.

In particular, said step M1.2 comprises: the sending end selects an encoding base X or P according to a random number in the binary true random number R1, wherein 0 selects an X base, and 1 selects a P base; based on the selection of the coding bases in the binary true random number R1, selecting the coding coherent state quantum information of the corresponding bases according to the random number in the binary true random number R2;

when the encoding base of the binary true random number R1 is X base, and when the binary true random number R2 is 0, then the coherent state | α is selected>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^πi>(ii) a When the coding base of the binary true random number R1 is P base, and when the binary true random number R2 is 0, the coherent state | α e is selected^πi/2>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^3πi/2>Where a denotes alpha which is the amplitude of the coherent quantum signal, and i denotes an imaginary unit.

Specifically, the step M2 includes:

step M2.1: the sending end and the receiving end simultaneously send the encoded quantum signals to the measuring end through a quantum channel;

step M2.2: the measuring end passes through 50: 50, the optical beam splitter interferes the quantum signals;

step M2.3: coherent detection is carried out on the quantum signals after interference, one component is measured, the other component is measured, and the measured value X is obtained_CAnd P_DAnd discloses these measurements.

In particular, said step M2.3 comprises: the sending end and the receiving end encode the key information on the discrete phases of the continuous variable signals which are matched with each other, the key information cannot be revealed by publishing the information of the measuring end, the irrelevant quantum key distribution of the measuring equipment is realized by utilizing the actually available low-efficiency quantum homodyne detector, and the measurement is respectively obtainedValue X_CAnd P_D. Obtaining X with a detector_CAnd P_DBut X_CAnd P_DInstead of the key, the detecting party publishes the result, which is needed to help the sending and receiving ends to establish the associated shared key.

Specifically, the step M3 includes:

step M3.1: the sending end and the receiving end both disclose respective random number strings R1, and respectively store the random number strings R1 with the consistent sending end and receiving end and the measured value X_CAnd P_DSatisfy { X ] for the same X radicals, respectively_C∈R:-_C≤X_C≤_COr { P for the same P base_D∈R:-_D≤P_D≤_DR2 of the sending terminal random number string R1 and R2 corresponding base coded coherent quantum signals meeting the judgment conditions are marked as K_AAnd the coherent quantum signals coded by the corresponding bases of the receiving end random number strings R1 and R2 are marked as K_B；

Wherein R represents a real number, X_CRepresenting the X-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Cthe judgment threshold of the detected X component is represented, namely, whether the result published by a measuring party meets the judgment threshold range is judged, a sending party and a receiving party respectively judge whether the currently prepared and coded signals can generate effective keys, subscript C represents the quantum signal modulus C detected by a Hom quantum homodyne measurer, and subscript P represents that the quantum signal modulus C and the P are respectively C_DRepresenting the P-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Da decision threshold representing the detected P component;

step M3.2: when the random number strings R1 of the sending end and the receiving end are correspondingly selected to be P base, the receiving end turns over K_BBit, the sending end and the receiving end form consistent key bits K and K';

step M3.3: the sending end and the receiving end respectively reserve the unsatisfied K_AAnd K_BThe transmitting end does not satisfy K_AThe coherent state quantum signal of different bases is denoted as (X)_A,P_A) Will receive end not satisfy K_BOfThe coherent quantum signal is denoted as (X)_B,P_B)。

Specifically, the step M4 includes: the transmitting terminal and the receiving terminal prepare the quantum signal (X) according to the stored_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DAnd evaluating the channel over-noise and transmittance parameters.

Specifically, the step M5 includes:

step M5.1: negotiating the generated key bits K and K' by the transmitting end and the receiving end through a classical channel to obtain a consistent bit string;

step M5.2: and calculating a compression factor according to the parameters obtained by parameter evaluation, and performing privacy enhancement operation on the obtained bit string to finally obtain a string of shared security keys.

Specifically, the parameter evaluation includes: evaluating channel over-noise and channel transmittance in the communication process, and evaluating the leaked information quantity and the mutual information quantity of a legal party; and judging whether the secret key rate is greater than zero or not according to the parameter evaluation, namely whether a legal party can obtain the safety secret key or not, and giving up communication and restarting when the secret key rate is less than zero.

The invention provides a device-independent quantum key distribution system based on continuous variable measurement, which comprises:

module M1: the sending terminal and the receiving terminal carry out quantum signal preparation and coding to obtain quantum signals (X) of the sending terminal and the receiving terminal_A,P_A) And (X)_B,P_B)；

Module M2: the sending end and the receiving end transmit the quantum signals to the measuring end, the measuring end interferes the quantum signals, and the interfered quantum signals are detected to obtain a measured value X_CAnd P_D；

Module M3: carrying out information decoding on the detected quantum signals;

module M4: preparing quantum signals (X) according to the preserved preparation of a transmitting terminal and a receiving terminal_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DPerforming parameter evaluation;

module M5: and carrying out data negotiation according to the decoded quantum signals and carrying out privacy enhancement according to parameter evaluation.

Specifically, the module M1 includes:

module M1.1: respectively obtaining binary true random number strings R1 and R2 according to binary true random number generators of a sending end and a receiving end;

module M1.2: selecting the encoding coherent state quantum signals of the corresponding bases according to binary true random numbers R1 and R2;

module M1.3: and adjusting the coherent state quantum signal through an adjustable attenuator to optimize the finally generated safe key rate.

The optimization is to maximize the key rate, i.e., X_A,P_AAnd X_B,P_BThe values of (a) take an optimum value, which depends on the intensity of the different signal lights or on the amplitude alpha (hereinafter you will be referred to as a), which is adjusted by adjusting the attenuator, which is related to the final key rate.

In particular, said module M1.2 comprises: the sending end selects an encoding base X or P according to a random number in the binary true random number R1, wherein 0 selects an X base, and 1 selects a P base; based on the selection of the coding bases in the binary true random number R1, selecting the coding coherent state quantum information of the corresponding bases according to the random number in the binary true random number R2;

when the encoding base of the binary true random number R1 is X base, and when the binary true random number R2 is 0, then the coherent state | α is selected>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^πi>(ii) a When the coding base of the binary true random number R1 is P base, and when the binary true random number R2 is 0, the coherent state | α e is selected^πi/2>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^3πi/2>Where a denotes alpha which is the amplitude of the coherent quantum signal, and i denotes an imaginary unit.

Specifically, the module M2 includes:

module M2.1: the sending end and the receiving end simultaneously send the encoded quantum signals to the measuring end through a quantum channel;

module M2.2: the measuring end passes through 50: 50, the optical beam splitter interferes the quantum signals;

module M2.3: coherent detection is carried out on the quantum signals after interference, one component is measured, the other component is measured, and the measured value X is obtained_CAnd P_DAnd discloses these measurements.

In particular, said module M2.3 comprises: the sending end and the receiving end encode the key information on the discrete phases of the continuous variable signals which are matched with each other, the key information cannot be revealed by publishing the information of the measuring end, the irrelevant quantum key distribution of the measuring equipment is realized by utilizing the actually available low-efficiency quantum homodyne detector, and the measured values X are respectively obtained_CAnd P_D. Obtaining X with a detector_CAnd P_DBut X_CAnd P_DInstead of the key, the detecting party publishes the result, which is needed to help the sending and receiving ends to establish the associated shared key.

Specifically, the module M3 includes:

module M3.1: the sending end and the receiving end both disclose respective random number strings R1, and respectively store the random number strings R1 with the consistent sending end and receiving end and the measured value X_CAnd P_DSatisfy { X ] for the same X radicals, respectively_C∈R:-_C≤X_C≤_COr { P for the same P base_D∈R:-_D≤P_D≤_DR2 of the sending terminal random number string R1 and R2 corresponding base coded coherent quantum signals meeting the judgment conditions are marked as K_AAnd the coherent quantum signals coded by the corresponding bases of the receiving end random number strings R1 and R2 are marked as K_B；

Wherein R represents a real number, X_CRepresenting the X-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Cthe judgment threshold of the detected X component is represented, namely, by judging whether the result published by the measuring party meets the judgment threshold range, the sending party and the receiving party respectively judge whether the signals currently prepared and coded by the measuring party can generate effective keys, and the subscript C represents the Hom quantum homodyneThe quantum signal mode detected by the measurer is C, P_DRepresenting the P-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Da decision threshold representing the detected P component;

module M3.2: when the random number strings R1 of the sending end and the receiving end are correspondingly selected to be P base, the receiving end turns over K_BBit, the sending end and the receiving end form consistent key bits K and K';

module M3.3: the sending end and the receiving end respectively reserve the unsatisfied K_AAnd K_BThe transmitting end does not satisfy K_AThe coherent state quantum signal of different bases is denoted as (X)_A,P_A) Will receive end not satisfy K_BThe coherent state quantum signal of different bases is denoted as (X)_B,P_B)。

Specifically, the module M4 includes: the transmitting terminal and the receiving terminal prepare the quantum signal (X) according to the stored_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DAnd evaluating the channel over-noise and transmittance parameters.

Specifically, the module M5 includes:

module M5.1: negotiating the generated key bits K and K' by the transmitting end and the receiving end through a classical channel to obtain a consistent bit string;

module M5.2: and calculating a compression factor according to the parameters obtained by parameter evaluation, and performing privacy enhancement operation on the obtained bit string to finally obtain a string of shared security keys.

Specifically, the parameter evaluation includes: evaluating channel over-noise and channel transmittance in the communication process, and evaluating the leaked information quantity and the mutual information quantity of a legal party; and judging whether the secret key rate is greater than zero or not according to the parameter evaluation, namely whether a legal party can obtain the safety secret key or not, and giving up communication and restarting when the secret key rate is less than zero.

Example 2

Example 2 is a modification of example 1

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

As shown in fig. 1, the method for distributing independent quantum keys of continuous variable measurement devices based on phase matching of the present invention comprises the following steps:

in fig. 1, Laser represents a coherent state quantum signal source of a transmitting and receiving party, RNG is a binary true random number generator, QM is quadrature phase shift keying modulation (four coherent states are modulated), VOA is an adjustable attenuator, which implements control of signal light intensity, and BS is 50: 50 optical beam splitter, Hom₀And Hom₁For quantum homodyne detector, the X and P components of two output modes of BS, i.e. X, are detected separately_CAnd P_D。

The method comprises the following steps: and (4) quantum signal preparation. Firstly, a sender prepares binary true random number strings R1 and R2, the sender selects a coding base X or P according to a random number in a random number string R1, wherein 0 selects an X base, 1 selects a P base, and further selects a coding coherent state quantum signal of a corresponding base according to the random number in R2, when the coding base is the X base, if R2 is 0, a coherent state | alpha is selected>When the value is 1, | α e is selected^πi>(ii) a When the coding base is P base, coherent state | α e is selected if R2 is 0^πi/2>When the value is 1, | α e is selected^3πi/2>；

Step two: and (4) transmission and detection of quantum signals. The sender and the receiver simultaneously send the encoded quantum signals to the measurer through a quantum channel, and the measurer firstly passes through a 50: 50 the optical beam splitter is used for interference, then coherent detection is respectively carried out on the interfered coherent states, one component is measured by X, the other component is measured by P, and the measured values X are respectively obtained_CAnd P_DAnd disclosing these measurements;

step three: and (5) decoding the information. The sender and the receiver both disclose their own measurement basis information R1 and respectively store their basis consistenceAnd the measurement results satisfy { X ] for the same X base_C∈R:-_C≤X_C≤_COr { P for the same P base_D∈R:-_D≤P_D≤_DR2 of (9), each denoted as K_AAnd K_B. When the sender and the receiver are both P-based, the receiver turns over K in the hands_BThe bits finally form consistent key bits K and K' by two parties, and the X and P components of coherent state quantum signals of different prepared bases are respectively X_A,X_BAnd P_A,P_B。

Step four: and (6) evaluating parameters. The sender and receiver prepare quantum X according to the stored_A,X_BAnd P_A,P_BAnd corresponding measured values X disclosed by the measuring party_CAnd P_DEvaluating the over-noise and transmittance of the channel, evaluating the leaked information amount and the mutual information amount of a legal party, judging whether the secret key rate is greater than zero or not according to the evaluation result, namely whether the legal party can obtain a safe secret key or not, and giving up communication and restarting if the secret key rate is less than zero;

step five: data negotiation and security enhancement. And negotiating the generated binary data by the transmitting end and the receiving end through a classical channel to obtain a consistent bit string. And then, calculating a compression factor according to the parameters obtained by parameter evaluation, and carrying out privacy enhancement operation on the obtained bit string to finally obtain a string of shared security keys.

The parameter evaluation comprises: and evaluating the channel over-noise and the channel transmittance in the communication process, and evaluating the leaked information quantity and the mutual information quantity of a legal method.

The parameter evaluation method, the mutual information amount and the compression factor are calculated as follows:

here we still follow the evaluation procedure of the traditional gaussian modulation coherent CV-MDI-QKD theoretical model, i.e. the two channels (the two channels from the sender to the measurer and from the receiver to the measurer, both having equal transmittance) of a CV-MDI-QKD system satisfy the following model:

y＝tx+z (1)

wherein the content of the first and second substances,

t is the transmission of the two channels, eta is the efficiency of the two detectors on the measuring side, and X is the transmission variable (value X)_AOr P_AComponent, only one of the components is left after base comparison), y is a measurement variable (corresponding to two regular components

Or

Components, only one of which remains after base-contrast), z is a noise obeying a gaussian distribution, and the variance of z satisfies

Here V_elNormalized electrical noise of quantum balance homodyne detector, and xi is normalized noise of channel

<y²>＝ηT(V_A+ξ)+1+V_el， (3)

Wherein, V_AIs a gaussian modulation variance, and is,<>to perform an averaging operation.

Therefore, in estimating the relevant parameters, the parameter estimation is performed using the maximum likelihood estimation value of the following expression:

where m denotes the data size for parameter evaluation, x_iRepresenting an element in a transmission variable X, valued at X_AOr P_AComponent(s) of(one component is left after base comparison), y_iRepresenting elements in a measurement square variable y, taking values as two regular components

Or

Components (only one of which remains after base comparison).

Therefore, the estimation values of the channel transmittance and the over-noise obtained by the above maximum likelihood estimation sub-estimation are respectively:

according to the key information evaluated above, the legal mutual information quantity I can be calculated_ABIs composed of

Wherein the content of the first and second substances,

wherein the content of the first and second substances,

alpha represents the amplitude of the coherent state quantum signal,

wherein the content of the first and second substances,

in addition, the first and second substrates are,

H(x)＝-xlog₂x-(1-x)log₂(1-x)，

in represents i multiplied by a variable n, i being an imaginary unit and k being a selected decoding threshold.

When the protocol works in a symmetrical channel mode, namely the transmittance and the over-noise of the channel from Alice to Charlie and the transmittance and the over-noise of the channel from Bob to Charlie are equal, the transmittances are less than 1, the over-noise is greater than zero, and the amount of information leaked at the moment

Comprises the following steps:

wherein the content of the first and second substances,

wherein the content of the first and second substances,

when the protocol works in an ideal asymmetric channel mode, namely the transmittance of the Bob to Charlie channel is equal to 1 and the over-noise is zero, the leaked information amount is

Is composed of

Wherein the content of the first and second substances,

when mu is more than or equal to 1, K is 1, and the security key cannot be acquired; when mu is less than 1, the secret enhancement compression factor K in the symmetric channel mode and the ideal asymmetric channel mode can be calculated as

Wherein, β is negotiation efficiency of data negotiation between the sending end and the receiving end.

The invention is different from the previous CV-MDI-QKD protocol, because the invention adopts a phase matching coding method based on discrete modulation, the invention can directly generate a discretized binary original key, thereby directly carrying out negotiation and confidentiality enhancement processing by the existing post-processing algorithm method based on the discrete variable technology, reducing the realization complexity of the existing CVQKD system and improving the system performance from the post-processing angle.

The invention adopts a discrete phase matching method, has lower necessary detection efficiency (the necessary detection efficiency refers to the minimum quantum homodyne detector efficiency required by obtaining the security key rate under a specific transmission distance), so the protocol can still obtain the security key under the condition of actually lower detector efficiency, such as the detection efficiency of 0.6, but the traditional Gaussian modulation coherent CV-MDI-QKD can not obtain the security key.

The method for distributing the independent quantum key of the continuous variable measurement equipment based on the phase matching can allow the long-distance safe key distribution under an ideal asymmetric channel mode, and can provide a practical and available solution for the distribution of the independent continuous variable quantum key of the long-distance measurement equipment in the later period.

Although the safe transmission distance is not particularly high in the symmetrical channel mode because of the reduction of the channel capacity caused by self discrete phase matching, the invention has the advantages that the safe transmission distance can be realized by utilizing the existing detector (namely the efficiency of the detector is required to be very low), and the safe continuous variable quantum key distribution method can be suitable for short-distance high-repetition-frequency application scenes such as access networks and building-to-building and realizes the high-speed actual safe continuous variable quantum key distribution among users.

Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered to be both software programs for performing the methods and structures within hardware components.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (10)

1. A method for distributing independent quantum keys based on continuous variable measurement equipment is characterized by comprising the following steps:

step M1: the sending terminal and the receiving terminal carry out quantum signal preparation and coding to obtain quantum signals (X) of the sending terminal and the receiving terminal_A,P_A) And (X)_B,P_B)；

Step M2: the sending end and the receiving end transmit the quantum signals to the measuring end, the measuring end interferes the quantum signals, and the interfered quantum signals are detected to obtain a measured value X_CAnd P_D；

Step M3: carrying out information decoding on the detected quantum signals;

step M4: preparing quantum signals (X) according to the preserved preparation of a transmitting terminal and a receiving terminal_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DPerforming parameter evaluation;

step M5: and carrying out data negotiation according to the decoded quantum signals and carrying out privacy enhancement according to parameter evaluation.

2. The continuous variable measurement device-independent quantum key distribution method according to claim 1, wherein the step M1 comprises:

step M1.1: respectively obtaining binary true random number strings R1 and R2 according to binary true random number generators of a sending end and a receiving end;

step M1.2: selecting the encoding coherent state quantum signals of the corresponding bases according to binary true random numbers R1 and R2;

step M1.3: and adjusting the coherent state quantum signal through an adjustable attenuator to optimize the finally generated safe key rate.

3. The continuous variable measurement device-independent quantum key distribution method according to claim 2, wherein the step M1.2 comprises: the sending end selects an encoding base X or P according to a random number in the binary true random number R1, wherein 0 selects an X base, and 1 selects a P base; based on the selection of the coding bases in the binary true random number R1, selecting the coding coherent state quantum information of the corresponding bases according to the random number in the binary true random number R2;

when the encoding base of the binary true random number R1 is X base, and when the binary true random number R2 is 0, then the coherent state | α is selected>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^πi>(ii) a When the coding base of the binary true random number R1 is P base, and when the binary true random number R2 is 0, the coherent state | α e is selected^πi/2>(ii) a When the binary true random number R2 is 1, then the coherent state | α e is selected^3πi/2>Where a denotes alpha which is the amplitude of the coherent quantum signal, and i denotes an imaginary unit.

4. The continuous variable measurement device-independent quantum key distribution method according to claim 1, wherein the step M2 comprises:

step M2.1: the sending end and the receiving end simultaneously send the encoded quantum signals to the measuring end through a quantum channel;

step M2.2: the measuring end interferes the quantum signal through the optical beam splitter;

step M2.3: for quantum after interferenceThe signals are subjected to coherent detection to respectively obtain measured values X_CAnd P_D。

5. The continuous variable measurement device-independent quantum key distribution method according to claim 4, wherein the step M2.3 comprises: the sending end and the receiving end encode the key information on discrete phases of continuous variable signals which are matched with each other, the key information cannot be revealed by publishing the information of the measuring end, the irrelevant quantum key distribution of the measuring equipment is realized by utilizing a quantum homodyne detector with low preset efficiency, and measured values X are respectively obtained_CAnd P_D。

6. The continuous variable measurement device-independent quantum key distribution method according to claim 1, wherein the step M3 comprises:

step M3.1: the sending end and the receiving end both disclose respective random number strings R1, and respectively store the random number strings R1 with the consistent sending end and receiving end and the measured value X_CAnd P_DSatisfy { X ] for the same X radicals, respectively_C∈R:-_C≤X_C≤_COr { P for the same P base_D∈R:-_D≤P_D≤_DR2 of the sending terminal random number string R1 and R2 corresponding base coded coherent quantum signals meeting the judgment conditions are marked as K_AAnd the coherent quantum signals coded by the corresponding bases of the receiving end random number strings R1 and R2 are marked as K_B；

Wherein R represents a real number, X_CRepresenting the X-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Cthe judgment threshold of the detected X component is represented, namely, whether the result published by a measuring party meets the judgment threshold range is judged, a sending party and a receiving party respectively judge whether the currently prepared and coded signals can generate effective keys, subscript C represents the quantum signal modulus C detected by a Hom quantum homodyne measurer, and subscript P represents that the quantum signal modulus C and the P are respectively C_DRepresenting the P-component of the quantum signal detected by the Hom quantum homodyne detector on the measuring side,_Da decision threshold representing the detected P component;

step M3.2: when the random number strings R1 of the sending end and the receiving end are correspondingly selected to be P base, the receiving end turns over K_BBit, the sending end and the receiving end form consistent key bits K and K';

step M3.3: the sending end and the receiving end respectively reserve the unsatisfied K_AAnd K_BThe transmitting end does not satisfy K_AThe coherent state quantum signal of different bases is denoted as (X)_A,P_A) Will receive end not satisfy K_BThe coherent state quantum signal of different bases is denoted as (X)_B,P_B)。

7. The continuous variable measurement device-independent quantum key distribution method according to claim 1, wherein the step M4 comprises: the transmitting terminal and the receiving terminal prepare the quantum signal (X) according to the stored_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DAnd performing parameter evaluation.

8. The continuous variable measurement device-independent quantum key distribution method according to claim 1, wherein the step M5 comprises:

step M5.1: negotiating the generated key bits K and K' by the transmitting end and the receiving end through a classical channel to obtain a consistent bit string;

step M5.2: and calculating a compression factor according to the parameters obtained by parameter evaluation, and performing privacy enhancement operation on the obtained bit string to finally obtain a string of shared security keys.

9. The continuous variable measurement device-independent quantum key distribution method of claim 7, wherein the parameter evaluation comprises: evaluating channel over-noise and channel transmittance in the communication process, and evaluating the leaked information quantity and the mutual information quantity of a legal party; and judging whether the secret key rate is greater than zero or not according to the parameter evaluation, namely whether a legal party can obtain the safety secret key or not, and giving up communication and restarting when the secret key rate is less than zero.

10. A device-independent quantum key distribution system based on continuous variable measurement, comprising:

module M1: the sending terminal and the receiving terminal carry out quantum signal preparation and coding to obtain quantum signals (X) of the sending terminal and the receiving terminal_A,P_A) And (X)_B,P_B)；

Module M2: the sending end and the receiving end transmit the quantum signals to the measuring end, the measuring end interferes the quantum signals, and the interfered quantum signals are detected to obtain a measured value X_CAnd P_D；

Module M3: carrying out information decoding on the detected quantum signals;

module M4: preparing quantum signals (X) according to the preserved preparation of a transmitting terminal and a receiving terminal_A,P_A) And (X)_B,P_B) And corresponding measured values X disclosed by the measuring party_CAnd P_DPerforming parameter evaluation;

module M5: and carrying out data negotiation according to the decoded quantum signals and carrying out privacy enhancement according to parameter evaluation.

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