Quantum key distribution method, device and system

Abstract

The embodiment of the invention provides a quantum key distribution method, device and system, participants of quantum key distribution comprise a first party and a second party, and the method comprises the following steps: the first party prepares coherent light pulses with first light intensity and a first phase, and sends the coherent light pulses to the second party, the first phase is determined according to the first random value and the first key bit; the second party prepares a local oscillator light pulse with second light intensity and a second phase, the coherent light pulse and the local oscillator light pulse are input into a coherent detection module, a measurement result is obtained, and the second phase is determined according to a second random value; the second party compares the measurement result with a preset first threshold value, wherein the first threshold value is pre-agreed by the first party and the second party; if the measurement result and the first threshold meet a preset relationship, determining a second key bit corresponding to the first key bit in the second party, and disclosing a second random value to the first party; and the first party determines whether the first key bit is flipped or not according to the first random value and the second random value.

Description

A quantum key distribution method, device and system

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on March 31, 2023, with application number 2023103418969 and application name “A Quantum Key Distribution Method, Device and System”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the field of quantum communication, and in particular to a quantum key distribution method, device and system. Background Art

[0003] Quantum Key Distribution (QKD) is a technology that uses the properties of quantum mechanics to ensure communication security, allowing both communicating parties to generate and share a random, secure key to encrypt and decrypt messages. It has wide applications in practical cryptography, information security, national defense, and various secure communication environments.

[0004] A major challenge in quantum key distribution systems is how to achieve more practical, stable, and cost-effective quantum key distribution using optical devices. However, for security reasons, most current quantum key distribution systems control the signal intensity to the single-photon level. Furthermore, due to the attenuation of optical fiber and other channels, highly sensitive single-photon detectors are typically used at the measurement end. These detectors are often expensive and have low detection efficiency and high error rates due to issues such as dark counts and dead time.

[0005] Therefore, a new quantum key distribution scheme is needed.

[0006] Summary of the Invention

[0007] Embodiments of the present invention provide a method, apparatus, and system for quantum key distribution. This method enables the receiver of quantum key distribution to measure signal light using coherent detectors, eliminating the need for highly sensitive and expensive single-photon detectors. This results in lower-cost measurement equipment compared to existing solutions and effectively avoids the issues of dark counts and dead time associated with highly sensitive single-photon detectors, which can reduce measurement efficiency.

[0008] The present invention adopts a technical solution to solve the above technical problems. On the one hand, it provides a quantum key distribution method. The participants of the quantum key distribution include a first party and a second party. The method includes:

[0009] The first party prepares a coherent optical pulse having a first light intensity and a first phase, and transmits the coherent optical pulse to the second party, wherein the first phase is determined based on a first random value and a first key bit included in an original key of the first party;

[0010] The second party receives the coherent light pulse and prepares a local oscillator light pulse having a second light intensity and a second phase, inputs the coherent light pulse and the local oscillator light pulse into a coherent detection module, and obtains a measurement result, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to a second random value;

[0011] The second party compares the measurement result with a preset first threshold value, which is pre-agreed upon by the first and second parties; if the measurement result satisfies a preset relationship with the first threshold value, determining that the first key bit is in the second key bit corresponding to the second party, and disclosing the second random value to the first party;

[0012] The first party determines whether to flip the first key bit according to the first random value and the second random value.

[0013] Preferably, the method further comprises:

[0014] If the measurement result and the first threshold satisfy a preset relationship or not, then the step of determining the second key bit corresponding to the first key bit in the second party is abandoned.

[0015] Preferably, the first light intensity is randomly determined according to a plurality of pre-set light intensity values.

[0016] Preferably, the first phase can be expressed as:

[0017] Among them, φ i represents the first phase, represents the first random value, represents the first key bit;

[0018] Preferably, the first random value can be obtained by the first party from (k=0, 1, ... D-1; D is a positive natural number), the second random value can be randomly confirmed by the second party from (k=0,1,…D-1; D is a positive natural number) and confirmed randomly.

[0019] Preferably, the first threshold is greater than 0; if the measurement result and the first threshold satisfy a preset relationship, then determining the second key bit corresponding to the first key bit in the second party includes: if the measurement result is greater than the first threshold, then determining that the second key bit is 0.

[0020] Preferably, the first threshold is greater than 0; if the measurement result and the first threshold satisfy a preset relationship, the second key bit corresponding to the first key bit in the second party is determined, including: if the measurement result is less than the negative value of the first threshold, the second key bit is determined to be 1.

[0021] Preferably, the first party determines whether to flip the first key bit according to the first random value and the second random value, including:

[0022] If the absolute value of the difference between the first random value and the second random value falls within a preset interval, the first key bit is flipped.

[0023] In a second aspect, a quantum key distribution method is provided, wherein the participants in the quantum key distribution include a first party and a second party, and the method is performed by the first party, and the method includes:

[0024] preparing a coherent optical pulse having a first intensity and a first phase, and transmitting the coherent optical pulse to a second party, wherein the first phase is determined based on a first random value and a first key bit included in an original key of the first party;

[0025] Obtaining a second random value disclosed by the second party;

[0026] Determine whether to flip the first key bit according to the first random value and the second random value.

[0027] In a third aspect, a quantum key distribution method is provided, wherein the participants in the quantum key distribution include a first party and a second party, and the method is performed by the second party, and the method includes:

[0028] receiving a coherent optical pulse sent by the first party, and preparing a local oscillator optical pulse having a second optical intensity and a second phase, wherein the second optical intensity is greater than the first optical intensity of the coherent optical pulse, and the second phase is determined according to a second random value; inputting the coherent optical pulse and the local oscillator optical pulse into a coherent detection module to obtain a measurement result;

[0029] The measurement result is compared with a preset first threshold. If the measurement result satisfies a preset relationship with the first threshold, a second key bit is determined and the second random value is disclosed to the first party, wherein the first threshold is pre-agreed upon by the first and second parties.

[0030] In a fourth aspect, a quantum key distribution system is provided, including a first party and a second party as participants, wherein:

[0031] A first party is configured to prepare a coherent optical pulse having a first light intensity and a first phase, and transmit the coherent optical pulse to a second party, wherein the first phase is determined based on a first random value and a first key bit included in an original key of the first party;

[0032] The second party is configured to receive the coherent light pulse, prepare a local oscillator light pulse having a second light intensity and a second phase, input the coherent light pulse and the local oscillator light pulse into a coherent detection module, and obtain a measurement result, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to a second random value;

[0033] The second party is further configured to compare the measurement result with a preset first threshold value, where the first threshold value is pre-agreed upon by the first and second parties; if the measurement result satisfies a preset relationship with the first threshold value, determine that the first key bit is in a second key bit corresponding to the second party, and disclose the second random value to the first party;

[0034] The first party is further configured to determine whether to flip the first key bit according to the first random value and the second random value.

[0035] In a fifth aspect, a quantum key distribution device is provided, wherein the participants in the quantum key distribution include a first party and a second party, the device is provided at the first party, and the provision includes:

[0036] a preparation unit configured to prepare a coherent optical pulse having a first light intensity and a first phase, and send the coherent optical pulse to a second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party;

[0037] an acquiring unit configured to acquire a second random value disclosed by a second party;

[0038] The determining unit is configured to determine whether to flip the first key bit according to the first random value and the second random value.

[0039] In a sixth aspect, a quantum key distribution device is provided, wherein the participants in the quantum key distribution include a first party and a second party, the device is provided at the second party, and the device includes:

[0040] a measuring unit configured to receive a coherent optical pulse sent by the first party, and prepare a local oscillator optical pulse having a second optical intensity and a second phase, wherein the second optical intensity is greater than the first optical intensity of the coherent optical pulse, and the second phase is determined according to a second random value; input the coherent optical pulse and the local oscillator optical pulse into a coherent detection module to obtain a measurement result;

[0041] The determination unit is configured to compare the measurement result with a preset first threshold, and if the measurement result and the first threshold satisfy a preset relationship, determine a second key bit and disclose the second random value to the first party, wherein the first threshold is pre-agreed upon by the first party and the second party. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, 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 any creative work.

[0043] FIG1 is a schematic diagram of a scheme using a single photon detector in quantum key distribution;

[0044] FIG2A is a schematic diagram of a quantum key distribution scheme provided by an embodiment of the present invention;

[0045] FIG2B is a schematic structural diagram of a coherent detection module according to an embodiment of the present invention;

[0046] FIG3 is a flow chart of a quantum key distribution method provided by an embodiment of the present invention;

[0047] FIG4 is a flowchart of a quantum key distribution method provided by another embodiment of the present invention;

[0048] FIG5 is a flowchart of a quantum key distribution method provided by another embodiment of the present invention;

[0049] FIG6 is a structural diagram of a quantum key distribution system provided by an embodiment of the present invention;

[0050] FIG7 is a structural diagram of a quantum key distribution device provided by an embodiment of the present invention;

[0051] FIG8 is a structural diagram of a quantum key distribution device provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0053] As mentioned above, for security reasons, most current quantum key distribution systems control the transmitted signal intensity to the single-photon level. Combined with channel attenuation, such as in optical fibers, the signal intensity received by the measurement end is often very weak. Therefore, the measurement end typically uses a highly sensitive single-photon detector to measure the received signal. Figure 1 illustrates a scheme using single-photon detectors in quantum key distribution. As shown in Figure 1, the transmitting end (e.g., Alice) can generate a single-photon optical signal using a light source and encode the key information into the optical signal. This signal is then transmitted to the receiving end via a transmission channel (e.g., optical fiber). The receiving end (e.g., Bob) receives the optical signal and, after optical preprocessing (e.g., beam splitting), measures it using a single-photon detector and determines the key information based on the measurement results. However, this scheme presents the following challenges: Single-photon detectors are often very expensive, leading to high key distribution costs. Furthermore, the use of single-photon detectors can also result in low detection efficiency and high detection error rates due to issues such as dark counts and dead time. Dark counts occur when a single-photon detector, due to its high sensitivity, misinterprets stray light (non-signal light) and electrical noise as valid light signals. This misinterpretation is called a dark count. Dead time refers to the fixed amount of time (e.g., 20ns) required after a single-photon detector detects a photon to drain the capacitor charge before continuing to detect the next photon. This fixed time is called the dead time. Since photons cannot be detected during the dead time, measurement data may be missed.

[0054] In response to the above problems, the embodiments of this specification provide a new quantum key distribution scheme. Figure 2A is a schematic diagram of a quantum key distribution scheme provided by an embodiment of the present invention. As shown in Figure 2A, a coherent optical signal can be generated by the transmitting end Alice through a coherent light source, and the key information can be encoded into the coherent optical signal. Then, it is sent to the receiving end through a transmission channel. The receiving end (for example, Bob end) receives the coherent optical signal and prepares a corresponding local oscillator optical pulse. After optical preprocessing of the optical signal, the coherent optical pulse and the local oscillator optical pulse are input into the coherent detection module to obtain a measurement result, and then the key information is determined based on the measurement result. Figure 2B shows a schematic diagram of the structure of the coherent detection module. As shown in the figure, the input signal light and the local oscillator light enter the beam splitter respectively, and after interference, they enter the two detectors respectively. After the detector obtains the classical measurement result, the result is input into the post-processing module for certain operations to obtain the final measurement result. The post-processing here is usually a subtraction operation. It should be emphasized that the detector used here does not need to be a high-sensitivity single-photon detector, and a general detector is sufficient.

[0055] The advantages of the quantum key distribution scheme described above are that it reduces the error rate of measurement results by using coherent light to encode information and extract keys, and by replacing the measurement device with a coherent detection module instead of a single-photon detector. Furthermore, the coherent detection module can use a more cost-effective detector, thereby reducing the cost of quantum key distribution.

[0056] The following is a detailed description of the quantum key distribution scheme provided by the embodiments of this specification. Figure 3 is a flow chart of a quantum key distribution method provided by an embodiment of the present invention. The participants in the quantum key distribution include a first party and a second party. As shown in Figure 3, the method includes at least the following steps:

[0057] Step 31: The first party prepares a coherent optical pulse having a first light intensity and a first phase, and transmits the coherent optical pulse to the second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party;

[0058] Step 32: The second party receives the coherent optical pulse and prepares a local oscillator optical pulse having a second light intensity and a second phase, inputs the coherent optical pulse and the local oscillator optical pulse into a coherent detection module, and obtains a measurement result, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to a second random value;

[0059] Step 33: The second party compares the measurement result with a preset first threshold value, which is pre-agreed upon by the first and second parties. If the measurement result satisfies a preset relationship with the first threshold value, the second party determines the second key bit corresponding to the first key bit of the second party, and discloses the second random value to the first party.

[0060] Step 34: The first party determines whether to flip the first key bit based on the first random value and the second random value.

[0061] First, in step 31, the first party prepares a coherent optical pulse having a first light intensity and a first phase, and sends the coherent optical pulse to the second party.

[0062] In one embodiment, the first party may, for example, generate a coherent state pulse through a quantum coherent light source, and obtain a coherent light pulse of a first light intensity and a first phase through intensity and phase modulation, and transmit the modulated coherent light pulse to the second party through a transmission channel.

[0063] In different embodiments, the value of the first light intensity may be different. In one embodiment, the first light intensity may be randomly determined based on a plurality of pre-set light intensity values. In a specific embodiment, for example, the first light intensity may be randomly selected from three values: 0, ν, and μ (0<ν<μ).

[0064] The first phase may be determined based on the first random value and the first key bit included in the original key of the first party. In different embodiments, the first phase may be determined in different ways. In one embodiment, the first phase may be expressed as:

[0065] Among them, φ i represents the first phase, represents the first random value, Represents the first key bit, which is a bit in the original key held by the first party to be distributed.

[0066] In a specific embodiment, the first random value Can be obtained by the first party from (k=0,1,…D-1; D is a positive natural number).

[0067] In one embodiment, before step 31 , the first party and the second party may calibrate the communication clock and initial phase of the channel, and perform identity authentication on both parties.

[0068] Each participant can perform its own steps through its terminal. The terminal does not refer specifically to a participant's terminal device, such as a workstation. It can be any computing device used by the participant for computing and processing, including but not limited to servers, workstations, minicomputers, mobile processing terminals, etc., or it can be the coordinated work of multiple computing devices of the participant. Because the process of quantum key distribution can include quantum operations and post-processing, in some embodiments, the participant's terminal can also include a quantum-classical hybrid server, which includes a quantum processor and a classical processor. The quantum processor can perform the quantum operations, and the classical processor can perform the post-processing.

[0069] Then, in step 32, the second party may receive the coherent optical pulse and prepare a local oscillator optical pulse with a second intensity and a second phase, input the coherent optical pulse and the local oscillator optical pulse into a coherent detection module to obtain a measurement result. The second phase is determined according to the second random value.

[0070] In this step, the second party can, for example, determine the second phase based on the second random value, and use a local oscillator light source to prepare local oscillator light of a second light intensity of the corresponding phase, and input the received signal light and the prepared local oscillator light into the coherent measurement module for measurement to obtain a measurement result.

[0071] Theoretically, the second light intensity can be much greater than the first light intensity. Therefore, in one embodiment, the second light intensity can be greater than the first light intensity. In one embodiment, the second light intensity can be greater than a preset multiple of the first light intensity. In different specific embodiments, the preset multiple can be different specific multiples.

[0072] The second phase can be determined based on the second random value. A second party can (k=0,1,…D-1; D is a positive natural number).

[0073] The second party, based on the preparation of the local oscillator light described above, inputs the received coherent light pulse and the local oscillator light pulse prepared by this party into the coherent detection module. Referring to Figure 2B, the coherent light pulse and the local oscillator light pulse interfere with each other through the beam splitter and enter the two detectors respectively. After the two detectors obtain the classical measurement results respectively, the post-processing module performs an operation such as a subtraction operation on the two classical measurement results and uses the operation result as the measurement result n i .

[0074] Then, in step 33, the second party compares the measurement result with a preset first threshold, which is pre-agreed upon by the first and second parties; if the measurement result and the first threshold satisfy a preset relationship, the second key bit corresponding to the first key bit of the second party is determined, and the second random value is disclosed to the first party.

[0075] In this step, the measurement result n i With the first threshold n th Satisfying the preset relationship can indicate that the correctness of the transmission of the first key bit is high, so it can be determined that the key bit corresponding to the first key bit in the second party (the second key bit), that is, the key bit received by the second party. Specifically, in different embodiments, the first threshold n th , and the preset relationship may be different. In one embodiment, the first threshold n th For example, it can be greater than 0. If the measurement result is greater than the first threshold, that is, n i >n th , then it is determined that the second key bit is 0. In another embodiment, if the measurement result is less than the negative value of the first threshold, that is, n i <-n th , it is determined that the second key bit is 1.

[0076] Measurement result n i With the first threshold n th Failure to satisfy the preset relationship may indicate that the transmission accuracy of the first key bit is low, and therefore, determination of the key bit corresponding to the first key bit at the second party (the second key bit), i.e., the key bit received by the second party, may be abandoned. Therefore, in one embodiment, if the measurement result and the first threshold do not satisfy the preset relationship, determination of the second key bit corresponding to the first key bit at the second party is abandoned.

[0077] After the second party determines the second key bit, it can disclose the second random value to the first party. Because the first party's original key may include multiple key bits, in an embodiment, steps 31 to 33 can be performed in multiple rounds (for multiple key bits). Therefore, in one embodiment, after performing these multiple rounds, the second party can disclose to the first party the rounds in which it did not give up confirming the corresponding key bit of its own party, as well as the second random values ​​corresponding to these rounds.

[0078] Thereafter, in step 34, the first party determines whether to flip the first key bit based on the first random value and the second random value.

[0079] In actual scenarios, if the difference between the first random value and the second random value selected by the first party and the second party respectively is in a specific interval, the second key bit determined by the second party is often not the original value of the first key bit, but its flipped value (for example, 0 becomes 1, 0 becomes 1). Therefore, after the first party obtains the second random value disclosed by the second party, it can be compared whether the difference between the two is in the above-mentioned specific area. And based on the comparison result, determine whether to flip the original first key bit of this party as well, so as to keep it consistent with the second key bit determined by the second party. In one embodiment, if the absolute value of the difference between the first random value and the second random value belongs to the preset interval, the first key bit is flipped (0 becomes 1, 0 becomes 1). In different embodiments, the preset interval may be different. In a specific embodiment, the preset interval can be If Then the first key bit is flipped, otherwise the first key bit is not flipped.

[0080] As previously described, steps 31-33 can be performed multiple times (for multiple key bits). Therefore, in one embodiment, the first party can determine whether to flip its first key bit in each of the multiple rounds based on the rounds in which the second party did not abandon its confirmation of the corresponding key bit, as well as the second random values ​​corresponding to these rounds. Furthermore, the first and second parties can determine the key to be retained by each party based on the key bits determined by each party in each round that did not abandon their confirmation.

[0081] In order to further improve the accuracy of the keys retained by both parties and strengthen the security of key distribution, in one embodiment, the first party and the second party may also conduct further information negotiation (Information Reconciliation) and / or privacy amplification (Privacy Amplification) based on the keys of both parties. Information negotiation is mainly used to ensure that the keys held by each user are the same, that is, the consistency of the keys. Privacy amplification is mainly used to prevent potential eavesdroppers from obtaining key information, that is, to ensure the security of the keys. In different specific embodiments, the specific methods for the first party and the second party to conduct information negotiation and / or privacy amplification may be different, and this specification does not limit this.

[0082] In summary, the quantum key distribution method provided by an embodiment of the present invention can replace the measurement device from a single-photon detector with a coherent detection module through information encoding, optical signal transmission and key extraction based on coherent light. On the one hand, the error rate of optical signal measurement is significantly reduced, and the measurement efficiency is improved. On the other hand, compared with the conventional scheme that uses expensive single-photon detectors for optical signal measurement, this method can use low-cost ordinary optical detectors for optical signal measurement, which also significantly reduces the cost of quantum key distribution.

[0083] FIG4 is a flow chart of a quantum key distribution method provided by another embodiment of the present invention. The participants in quantum key distribution include a first party and a second party, and the method is performed by the first party. As shown in FIG4 , the method includes at least the following steps:

[0084] Step 41, preparing a coherent optical pulse having a first light intensity and a first phase, and sending the coherent optical pulse to a second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party;

[0085] Step 42: Obtain a second random value disclosed by the second party; the second random value is disclosed when the second party determines that a measurement result satisfies a preset relationship with a first threshold, wherein the measurement result is obtained by the second party inputting a local oscillator optical pulse having a second light intensity and a second phase, and the coherent optical pulse, prepared by the second party, into a coherent detection module, wherein the second light intensity is greater than the first light intensity, and the second phase is determined based on the second random value; and the first threshold is pre-agreed upon by the first and second parties.

[0086] Step 43: Determine whether to flip the first key bit according to the first random value and the second random value.

[0087] FIG5 is a flow chart of a quantum key distribution method provided by another embodiment of the present invention. The participants in quantum key distribution include a first party and a second party, and the method is performed by the first party. As shown in FIG5 , the method includes at least the following steps:

[0088] Step 51: Receive a coherent optical pulse having a first intensity and a first phase sent by a first party, wherein the first phase is determined based on a first random value held by the first party and a first key bit included in an original key of the first party; prepare a local oscillator optical pulse having a second intensity and a second phase, wherein the second intensity is greater than the first intensity of the coherent optical pulse, and the second phase is determined based on a second random value; input the coherent optical pulse and the local oscillator optical pulse into a coherent detection module to obtain a measurement result;

[0089] Step 52: Compare the measurement result with a first threshold value agreed upon in advance by the first and second parties. If the measurement result satisfies a preset relationship with the first threshold value, determine the second key bit corresponding to the first key bit of the second party, and disclose the second random value to the first party so that the first party can determine whether to flip the first key bit based on the first random value and the second random value.

[0090] According to another embodiment, a quantum key distribution system is also provided. FIG6 is a block diagram of a quantum key distribution system provided by an embodiment of the present invention. As shown in FIG6 , the system includes a first party 61 and a second party 62 as participants, wherein:

[0091] A first party 61 is configured to prepare a coherent optical pulse having a first intensity and a first phase, and transmit the coherent optical pulse to a second party, wherein the first phase is determined based on a first random value and a first key bit included in an original key of the first party;

[0092] The second party 62 is configured to receive the coherent optical pulse and prepare a local oscillator optical pulse having a second light intensity and a second phase, input the coherent optical pulse and the local oscillator optical pulse into a coherent detection module to obtain a measurement result, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to a second random value;

[0093] The second party 62 is further configured to compare the measurement result with a preset first threshold value, the first threshold value being pre-agreed upon by the first and second parties; if the measurement result satisfies a preset relationship with the first threshold value, determine that the first key bit is in a second key bit corresponding to the second party, and disclose the second random value to the first party;

[0094] The first party 61 is further configured to determine whether to flip the first key bit according to the first random value and the second random value.

[0095] According to another embodiment, a quantum key distribution system is also provided. FIG7 is a block diagram of a quantum key distribution system provided by an embodiment of the present invention. As shown in FIG6 , the system 600 includes a first party 610 and a second party 620 as participants, wherein:

[0096] A first party 610 is configured to prepare a coherent optical pulse having a first intensity and a first phase, and transmit the coherent optical pulse to a second party, wherein the first phase is determined based on a first random value and a first key bit included in an original key of the first party;

[0097] The second party 620 is configured to receive the coherent optical pulse, prepare a local oscillator optical pulse having a second light intensity and a second phase, input the coherent optical pulse and the local oscillator optical pulse into a coherent detection module, and obtain a measurement result, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to a second random value;

[0098] The second party 620 is further configured to compare the measurement result with a preset first threshold value, the first threshold value being pre-agreed upon by the first and second parties; if the measurement result satisfies a preset relationship with the first threshold value, determine that the first key bit is in a second key bit corresponding to the second party, and disclose the second random value to the first party;

[0099] The first party 610 is further configured to determine whether to flip the first key bit according to the first random value and the second random value.

[0100] In one embodiment, the first party 610 may include a quantum key distribution device. As shown in FIG7 , the device includes:

[0101] a preparation unit 611 configured to prepare a coherent optical pulse having a first light intensity and a first phase, and send the coherent optical pulse to a second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party;

[0102] an acquisition unit 612 configured to acquire a second random value disclosed by the second party when determining that a measurement result satisfies a preset relationship with a first threshold, wherein the measurement result is obtained by the second party inputting a local oscillator optical pulse having a second light intensity and a second phase and a coherent optical pulse prepared by the second party into a coherent detection module, wherein the second light intensity is greater than the first light intensity, and the second phase is determined based on the second random value; and the first threshold is pre-agreed upon by the first and second parties;

[0103] The determining unit 613 is configured to determine whether to flip the first key bit according to the first random value and the second random value.

[0104] In one embodiment, the second party 620 may include a quantum key distribution device. As shown in FIG8 , the device includes:

[0105] The measurement unit 621 is configured to receive a coherent optical pulse having a first light intensity and a first phase sent by a first party, wherein the first phase is determined based on a first random value held by the first party and a first key bit included in the original key of the first party; prepare a local oscillator optical pulse having a second light intensity and a second phase, wherein the second light intensity is greater than the first light intensity of the coherent optical pulse, and the second phase is determined based on the second random value; input the coherent optical pulse and the local oscillator optical pulse into a coherent detection module to obtain a measurement result;

[0106] The determination unit 622 is configured to compare the measurement result with a first threshold pre-agreed upon by the first party and the second party; if the measurement result satisfies a preset relationship with the first threshold, determine the second key bit corresponding to the first key bit of the second party, and disclose the second random value to the first party, so that the first party determines whether to flip the first key bit based on the first random value and the second random value.

[0107] According to yet another embodiment, a computer-readable medium is provided, comprising a computer program stored thereon, and the computer program executes the above method when the computer is running.

[0108] According to yet another embodiment, a computing device is provided, including a memory and a processor, wherein the memory stores executable code, and the processor implements the above method when executing the executable code.

[0109] The foregoing description of this specification describes specific embodiments. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different from that described in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order shown or the sequential order to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0110] Professionals should also be further aware that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0111] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0112] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A quantum key distribution method, wherein the participants of the quantum key distribution include a first party and a second party, and the method comprises: The first party prepares a coherent optical pulse having a first light intensity and a first phase, and sends the coherent optical pulse to the second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party; The second party receives the coherent light pulse, prepares a local oscillator light pulse with a second light intensity and a second phase, inputs the coherent light pulse and the local oscillator light pulse into a coherent detection module, and obtains a measurement result, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to a second random value; The second party compares the measurement result with a preset first threshold value, where the first threshold value is pre-agreed upon by the first party and the second party; if the measurement result satisfies a preset relationship with the first threshold value, determines that the first key bit is at a second key bit corresponding to the second party, and discloses the second random value to the first party; The first party determines whether to flip the first key bit according to the first random value and the second random value.

2. The method according to claim 1, further comprising: If the measurement result and the first threshold satisfy a preset relationship or not, then determining the second key bit corresponding to the first key bit at the second party is abandoned.

3. The method according to claim 1, wherein The first light intensity is randomly determined according to a plurality of preset light intensity values.

4. The method according to claim 1, wherein The first phase is expressed as: Among them, φ i represents the first phase, represents the first random value, Represents the first key bit.

5. The method according to claim 1, wherein: The first random value is obtained by the first party from The second random value is determined randomly by the second party from Determined randomly.

6. The method according to claim 1, wherein: The first threshold is greater than 0; If the measurement result and the first threshold satisfy a preset relationship, determining the second key position corresponding to the first key position at the second party includes: If the measurement result is greater than the first threshold, it is determined that the second key bit is 0.

7. The method according to claim 1, wherein: The first threshold is greater than 0; If the measurement result and the first threshold satisfy a preset relationship, determining the second key position corresponding to the first key position at the second party includes: If the measurement result is less than the negative value of the first threshold, it is determined that the second key bit is 1.

8. The method according to claim 1, wherein: The first party determines whether to flip the first key bit according to the first random value and the second random value, including: If the absolute value of the difference between the first random value and the second random value belongs to a preset interval, the first key bit is flipped.

9. A quantum key distribution method, wherein the participants of the quantum key distribution include a first party and a second party, the method is performed by the first party, and the method comprises: preparing a coherent optical pulse having a first light intensity and a first phase, and sending the coherent optical pulse to a second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party; Obtaining a second random value disclosed by the second party when it is determined that the measurement result and the first threshold satisfy a preset relationship, wherein the measurement result is obtained by the second party inputting a local oscillator optical pulse having a second light intensity and a second phase and a coherent optical pulse prepared by the second party into a coherent detection module, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to the second random value; and the first threshold is pre-agreed by the first party and the second party; Determine whether to flip the first key bit according to the first random value and the second random value.

10. A method for quantum key distribution, wherein the participants of the quantum key distribution include a first party and a second party, the method is performed by the second party, and the method comprises: receiving a coherent optical pulse having a first light intensity and a first phase sent by a first party, wherein the first phase is determined according to a first random value held by the first party and a first key bit included in an original key of the first party; Prepare a local oscillator light pulse with a second light intensity and a second phase, wherein the second light intensity is greater than the first light intensity of the coherent light pulse, and the second phase is determined according to a second random value; input the coherent light pulse and the local oscillator light pulse into a coherent detection module to obtain a measurement result; The measurement result is compared with a first threshold value pre-agreed upon by the first party and the second party. If the measurement result satisfies a preset relationship with the first threshold value, the second key bit corresponding to the first key bit of the second party is determined, and the second random value is disclosed to the first party so that the first party can determine whether to flip the first key bit based on the first random value and the second random value.

11. A quantum key distribution system, comprising a first party and a second party as participants, wherein: A first party configured to prepare a coherent optical pulse having a first light intensity and a first phase, and send the coherent optical pulse to a second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party; The second party is configured to receive the coherent light pulse, prepare a local oscillator light pulse with a second light intensity and a second phase, input the coherent light pulse and the local oscillator light pulse into a coherent detection module, and obtain a measurement result, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to a second random value; The second party is further configured to compare the measurement result with a preset first threshold, where the first threshold is pre-agreed by the first party and the second party; if the measurement result and the first threshold satisfy a preset relationship, determine the second key bit corresponding to the first key bit of the second party, and disclose the second random value to the first party; The first party is further configured to determine whether to flip the first key bit according to the first random value and the second random value.

12. A quantum key distribution device, wherein the participants of the quantum key distribution include a first party and a second party, the device is arranged at the first party, and the arrangement includes: a preparation unit configured to prepare a coherent optical pulse having a first light intensity and a first phase, and send the coherent optical pulse to a second party, wherein the first phase is determined according to a first random value and a first key bit included in an original key of the first party; an acquisition unit configured to acquire a second random value disclosed by the second party when it is determined that a measurement result satisfies a preset relationship with a first threshold, wherein the measurement result is obtained by the second party inputting a local oscillator optical pulse having a second light intensity and a second phase and a coherent optical pulse prepared by the second party into a coherent detection module, wherein the second light intensity is greater than the first light intensity, and the second phase is determined according to the second random value; and the first threshold is pre-agreed by the first party and the second party; The determination unit is configured to determine whether to flip the first key bit according to the first random value and the second random value.

13. A quantum key distribution device, wherein the participants of the quantum key distribution include a first party and a second party, the device is arranged at the second party, and the device comprises: The measuring unit is configured to receive a coherent optical pulse having a first light intensity and a first phase sent by a first party, wherein the first phase is determined according to a first random value held by the first party and a first key bit included in an original key of the first party; prepare a local oscillator optical pulse having a second light intensity and a second phase, wherein the second light intensity is greater than the first light intensity of the coherent optical pulse, and the second phase is determined according to a second random value; input the coherent optical pulse and the local oscillator optical pulse into a coherent detection module to obtain a measurement result; The determination unit is configured to compare the measurement result with a first threshold value pre-agreed upon by the first party and the second party, and if the measurement result and the first threshold value satisfy a preset relationship, determine the second key bit corresponding to the first key bit of the second party, and disclose the second random value to the first party, so that the first party can determine whether to flip the first key bit based on the first random value and the second random value.

Images