Quantum key distribution method and quantum key distribution system

Abstract

The application provides a quantum key distribution method and a quantum key distribution system. The method comprises the following steps: emitting an initial laser signal by using a phase-locked light source, wherein the phase difference of the initial laser signal from a plurality of quantum state preparation sending ends is a preset value; processing the initial laser signal by using a chopper to obtain a transition pulse laser signal; performing phase modulation on the transition pulse laser signal by using a first phase modulator to obtain a target pulse laser signal, wherein the phase modulation comprises randomization phase and bit encoding phase; sending the target pulse laser signal from the plurality of quantum state preparation sending ends to a measurement end, so that the measurement end generates a detection result according to the plurality of target pulse laser signals; and determining a target quantum key between the plurality of quantum state preparation sending ends according to the bit encoding and the detection result sent by the measurement end.

Description

Technical Field

[0001] This invention relates to the field of quantum communication technology, and more specifically, to a quantum key distribution method and a quantum key distribution system. Background Technology

[0002] Quantum Key Distribution (QKD) technology refers to the distribution of secure keys using quantum physics principles to achieve information-theoretic security, thereby enabling unconditionally secure communication. However, in practical applications, various imperfections exist in different devices, making it impossible to fully meet the theoretical security requirements, resulting in a gap between the theory and practice of quantum key distribution. Optical detection devices, in particular, are likely to have the most vulnerabilities.

[0003] In related technologies, the proposed Measurement Device Independent protocol solves the security problems of probe devices. It can cope with all attacks targeting probe devices and completely eliminate vulnerabilities at the probe end.

[0004] However, the above protocol requires monitoring of protocol parameters during communication, which may have a certain impact on the security of quantum communication. In addition, monitoring protocol parameters requires additional steps to analyze information leakage, making the distribution of quantum keys more cumbersome. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a quantum key distribution method and a quantum key distribution system.

[0006] One aspect of this invention provides a quantum key distribution method applied to a quantum key distribution system, wherein the quantum key distribution system includes a measurement end and a plurality of quantum state preparation and transmission ends, each of the quantum state preparation and transmission ends including a phase-locked light source, a chopper, and a first phase modulator, and the method includes:

[0007] An initial laser signal is emitted using the aforementioned phase-locked light source, wherein the phase difference between the initial laser signal at the transmitting end prepared by the multiple aforementioned quantum states is a preset value;

[0008] The initial laser signal is processed using the aforementioned chopper to obtain a transition pulse laser signal.

[0009] The transition pulse laser signal is phase-modulated using the first phase modulator to obtain the target pulse laser signal, wherein the phase modulation includes randomized phase and bit-coded phase;

[0010] The target pulse laser signal from multiple quantum state preparation transmitters is sent to the measurement end, so that the measurement end generates a detection result based on the multiple target pulse laser signals.

[0011] Based on the bit encoding and the detection results sent by the measurement end, the target quantum key between the sending end and the multiple quantum states is determined.

[0012] According to embodiments of the present invention, the quantum key distribution method further includes:

[0013] Obtain reference laser signals transmitted by a third-party laser to multiple quantum state preparation transmitters as described above;

[0014] For each of the above quantum states, the phase of the light source is adjusted according to the above reference laser signal to obtain the above initial laser signal.

[0015] According to an embodiment of the present invention, the aforementioned transition pulse laser signal includes a plurality of pulse signals having position numbers;

[0016] The method described above, which uses a first phase modulator to perform phase modulation on the transition pulse laser signal to obtain the target pulse laser signal, includes:

[0017] For each of the transition pulse laser signals, a random phase is generated as the randomized phase;

[0018] For each of the pulse signals, the bit-encoded phase is determined based on the random bits corresponding to the pulse signal;

[0019] The target loading phase of the pulse signal is determined based on the randomized phase and the bit-coded phase of the pulse signal;

[0020] An intermediate pulse laser signal is generated based on multiple pulse signals having the target loading phase;

[0021] The intermediate pulse laser signal is processed using an attenuator to obtain the target pulse laser signal at the single-photon level.

[0022] According to an embodiment of the present invention, determining the bit-encoded phase based on the random bits corresponding to the pulse signal includes:

[0023] The random bits of the above pulse signal are determined as bit codes;

[0024] When the bit encoding is 0, the bit encoding phase is 0.

[0025] When the bit encoding is 1, the bit encoding phase is π.

[0026] According to an embodiment of the present invention, determining the target quantum key between multiple quantum state preparation transmitters based on the bit encoding and the detection result transmitted by the measurement end includes:

[0027] The detection results sent by the measurement end corresponding to the initial laser signal are obtained, wherein the detection results include multiple target position numbers that the measurement end confirms as valid responses, and the detector number corresponding to each valid response target position;

[0028] Perform an XOR operation on the two bit codes corresponding to the two target position indices to obtain the initial quantum key corresponding to the initial laser signal, wherein the two target position indices are any two of the multiple target position indices;

[0029] The target quantum key is generated based on multiple initial quantum keys derived from the aforementioned initial laser signals.

[0030] According to an embodiment of the present invention, the measurement end includes a beam splitter and two single-photon detectors respectively connected to two output ends of the beam splitter;

[0031] After performing the XOR operation described above, the process also includes:

[0032] If the above detection results indicate that the pulse signals corresponding to the two target position numbers are determined to be valid responses by the two single-photon detectors, then one of the two quantum state preparation and transmission ends performs the XOR operation and then performs bit reversal processing as the initial quantum key, so that the other quantum state preparation and transmission end performs the XOR operation on the quantum bits.

[0033] According to an embodiment of the present invention, generating the target quantum key based on a plurality of initial quantum keys derived from a plurality of initial laser signals includes:

[0034] For each of the above initial quantum keys, if the absolute value of the difference between the two randomized phases of the multiple quantum state preparation and transmission ends corresponding to the above initial quantum key is a preset value, the above initial quantum key is determined as the sieved key;

[0035] For multiple quantum state preparation and transmission ends mentioned above, the sieved key is subjected to error correction processing to obtain the sieved key with error correction.

[0036] The aforementioned error-corrected sieved key is then subjected to a private amplification process to obtain the target quantum key.

[0037] According to an embodiment of the present invention, the measurement end includes a beam splitter and two single-photon detectors respectively connected to two output ends of the beam splitter;

[0038] The aforementioned measurement end generates detection results based on multiple target pulse laser signals, including:

[0039] The beam splitter described above is used to perform interference processing on multiple target pulse laser signals to obtain an output signal, wherein the output signal includes a first interference signal and a second interference signal;

[0040] For the first interference signal and the second interference signal included in the above output signal, the above interference signals are processed by two single-photon detectors respectively to determine whether the above interference signal is a valid response;

[0041] If the above interference signal is determined to be a valid response, the pulse position of the response of the single-photon detector on the above interference signal is determined as the above detection result, wherein the pulse position represents the target position number.

[0042] According to an embodiment of the present invention, prior to performing the above-described interference process, the method further includes:

[0043] A second phase modulator is used to perform phase drift compensation processing on the aforementioned target pulse laser signal to obtain a processed target pulse laser signal, so that the aforementioned beam splitter can perform interference processing on the aforementioned target pulse laser signal and the processed target pulse laser signal.

[0044] Another aspect of the present invention provides a quantum key distribution system, comprising:

[0045] Multiple quantum state preparation transmitters, including the aforementioned quantum state preparation transmitters.

[0046] A phase-locked light source is used to emit an initial laser signal, wherein the phase difference of the initial laser signal generated by the multiple quantum states is a preset value;

[0047] A chopper is used to process the initial laser signal to obtain a transition pulse laser signal;

[0048] A first phase modulator is used to perform phase modulation on the aforementioned transition pulse laser signal to obtain a target pulse laser signal, wherein the phase modulation includes randomized phase and bit-coded phase;

[0049] At the measurement end, multiple quantum state preparation and transmission ends are respectively connected to the measurement end via optical channels. The measurement end is used to generate detection results based on multiple target pulse laser signals transmitted by the multiple quantum state preparation and transmission ends.

[0050] The aforementioned quantum state preparation transmitter is also used to determine the target quantum key among multiple aforementioned quantum state preparation transmitters based on the aforementioned bit encoding and the aforementioned detection results sent by the aforementioned measurement terminal.

[0051] According to embodiments of the present invention, multiple quantum state preparation transmitters send target pulsed laser signals to a measurement terminal. The measurement terminal generates detection results based solely on these multiple target pulsed laser signals. The target quantum key is generated at the quantum state preparation transmitter based on the detection results. Even if an eavesdropper attempts to intercept the measurement terminal, they can only obtain the detection results and not the corresponding target quantum key. This ensures the security of quantum communication even when various security vulnerabilities exist at the measurement terminal. The target pulsed laser signal comprises multiple pulse signals with position indices. This high-dimensional encoding method, which generates one quantum key bit from multiple pulses, ensures that an eavesdropper cannot simultaneously measure the phase difference between the same pair of pulses from multiple quantum state preparation transmitters. This allows all communicating parties to ensure that an eavesdropper can only obtain a small amount of information without monitoring protocol parameters. Simultaneously, this reduces the difficulty of key generation and improves the practicality of quantum key distribution. Attached Figure Description

[0052] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0053] Figure 1 A flowchart of a quantum key distribution method according to an embodiment of the present invention is shown;

[0054] Figure 2 A block diagram of a quantum key distribution system according to an embodiment of the present invention is shown;

[0055] Figure 3 A block diagram of a quantum key distribution system according to another embodiment of the present invention is shown;

[0056] Figure 4 A block diagram of a quantum key distribution system according to yet another embodiment of the present invention is shown;

[0057] Figure 5 A block diagram of a quantum key distribution system according to another embodiment of the present invention is shown. Detailed Implementation

[0058] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0059] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0060] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0061] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Similarly, when using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0062] Embodiments of the present invention provide a quantum key distribution method and a quantum key distribution system. The method includes emitting an initial laser signal using a phase-locked source, wherein the phase difference between the initial laser signals from multiple quantum state preparation transmitters is a preset value; processing the initial laser signal using a chopper to obtain a transition pulse laser signal; performing phase modulation on the transition pulse laser signal using a first phase modulator to obtain a target pulse laser signal, wherein the phase modulation includes randomized phase and bit-encoded phase; transmitting the target pulse laser signal from the multiple quantum state preparation transmitters to a measurement end, so that the measurement end generates a detection result based on the multiple target pulse laser signals; and determining a target quantum key among the multiple quantum state preparation transmitters based on the bit encoding and the detection result transmitted by the measurement end.

[0063] Figure 1 A flowchart of a quantum key distribution method according to an embodiment of the present invention is shown. Figure 2 A block diagram of a quantum key distribution system according to an embodiment of the present invention is shown.

[0064] This invention provides a quantum key distribution method applied to a quantum key distribution system. The quantum key distribution system includes a measurement terminal 100 and multiple quantum state preparation and transmission terminals 200. Each quantum state preparation and transmission terminal 200 includes a phase-locked light source 210, a chopper 220, and a first phase modulator 230, such as... Figure 1 and Figure 2 As shown, the method includes operations S101 to S105.

[0065] In operation S101, an initial laser signal is emitted using a phase-locked light source 210, wherein the phase difference of the initial laser signal generated by multiple quantum states at the transmitter 200 is a preset value.

[0066] In operation S102, the initial laser signal is processed by chopper 220 to obtain the transition pulse laser signal.

[0067] In operation S103, the transition pulse laser signal is phase modulated using the first phase modulator 230 to obtain the target pulse laser signal. The phase modulation includes randomized phase and bit-coded phase.

[0068] In operation S104, target pulse laser signals from multiple quantum state preparation transmitters 200 are sent to the measurement end 100 so that the measurement end 100 generates detection results based on the multiple target pulse laser signals.

[0069] In operation S105, a target quantum key is prepared between multiple quantum states based on the bit encoding and the detection results sent by the measurement end 100.

[0070] According to an embodiment of the present invention, when there are two quantum state preparation transmitters 200, for example, the two quantum state preparation transmitters 200 are the Alice terminal and the Bob terminal, respectively. The phase-locked light source 210 of the Alice terminal and the phase-locked light source 210 of the Bob terminal output initial laser signals, wherein the phase difference between the two initial laser signals is a preset value, which can be 2nπ, where n is an integer. For either the Alice terminal or the Bob terminal, the chopper 220 converts the initial laser signal of the continuous laser into a transition pulse laser signal of the pulse laser type.

[0071] According to an embodiment of the present invention, the transition pulse laser signal is subjected to phase modulation processing such as grouped phase randomization and phase encoding using a first phase modulator 230, thereby obtaining a target pulse laser signal loaded with randomized phase and bit-coded phase. The Alice end and the Bob end respectively transmit the target pulse laser signal to the measurement end 100 through a channel (e.g., an optical fiber channel).

[0072] According to an embodiment of the present invention, the measurement end 100 performs interference processing on two target pulsed laser signals and detects the interference signals, sending the detection results to the Alice end and the Bob end respectively. Each of the Alice end and the Bob end determines the target quantum key between the Alice end and the Bob end based on its own bit encoding and the detection results sent by the measurement end 100. In the generation of the above-mentioned target quantum key, the quantum key distribution system does not need to monitor various protocol parameters in the communication in real time.

[0073] According to embodiments of the present invention, multiple quantum state preparation transmitters send target pulsed laser signals to a measurement terminal. The measurement terminal generates detection results based solely on these multiple target pulsed laser signals. The target quantum key is generated at the quantum state preparation transmitter based on the detection results. Even if an eavesdropper attempts to intercept the measurement terminal, they can only obtain the detection results and not the corresponding target quantum key. This ensures the security of quantum communication even when various security vulnerabilities exist at the measurement terminal. The target pulsed laser signal comprises multiple pulse signals with position indices. This high-dimensional encoding method, which generates one quantum key bit from multiple pulses, ensures that an eavesdropper cannot simultaneously measure the phase difference between the same pair of pulses from multiple quantum state preparation transmitters. This allows all communicating parties to ensure that an eavesdropper can only obtain a small amount of information without monitoring protocol parameters. Simultaneously, it reduces the difficulty of key generation and improves the practicality of quantum key distribution.

[0074] According to embodiments of the present invention, the quantum key distribution method further includes the following operations:

[0075] The reference laser signals transmitted by the third-party laser to the multiple quantum state preparation transmitters 200 are obtained; for each quantum state preparation transmitter 200, the phase of the light source is adjusted according to the reference laser signal to obtain the initial laser signal.

[0076] According to an embodiment of the present invention, in order to make the phase difference of the initial laser signals transmitted by different quantum state preparation transmitters 200 a preset value, a third-party laser can be used to transmit a reference laser signal to multiple quantum state preparation transmitters 200 respectively. Each quantum state preparation transmitter 200 adjusts its own light source phase according to the reference laser signal to obtain the initial laser signal.

[0077] In an alternative embodiment, one of the Alice end and the Bob end can send a reference laser signal to the other end, so that the other end can adjust the phase of the light source according to the reference laser signal to obtain the initial laser signal, thereby ensuring that the phase difference between the initial laser signals sent by the Alice end and the Bob end is a preset value.

[0078] In another alternative embodiment, the Alice end and the Bob end can be used to send reference laser signals to the measurement end respectively. The measurement end compensates for the phase difference between the Alice end and the Bob end in real time based on the two reference laser signals, thereby obtaining the initial laser signal equivalently.

[0079] Figure 3 A block diagram of a quantum key distribution system according to another embodiment of the present invention is shown.

[0080] According to an embodiment of the present invention, the transition pulse laser signal includes a plurality of pulse signals having position numbers;

[0081] According to an embodiment of the present invention, the transition pulse laser signal is phase-modulated using a first phase modulator 230 to obtain a target pulse laser signal, including the following operations:

[0082] For each transition pulse laser signal, a random phase is generated as the randomized phase; for each pulse signal, a bit-coded phase is determined based on the random bits corresponding to the pulse signal; the target loading phase of the pulse signal is determined based on the randomized phase and the bit-coded phase of the pulse signal; an intermediate pulse laser signal is generated based on multiple pulse signals with target loading phases; the intermediate pulse laser signal is processed using attenuator 240 to obtain a single-photon level target pulse laser signal.

[0083] According to an embodiment of the present invention, each transition pulse laser signal is a quantum pulse signal string, and each transition pulse laser signal includes L pulse signals.

[0084] According to an embodiment of the present invention, see Figure 3 For each quantum pulse signal train containing L pulse signals prepared by Alice, Alice selects a random phase θ. A As the randomized phase of the transition pulse laser signal, for each pulse signal in the quantum pulse signal train, the Alice terminal also randomly selects a random bit 0 or 1 as the bit code. The bit code phase is determined based on the bit code corresponding to the pulse signal; for example, the bit code of the i-th pulse signal is denoted as s. Ai After the first phase modulator 230 processes the i-th pulse signal, the target loading phase of the pulse signal is θ. A +π×s Ai Finally, an intermediate pulse laser signal is generated based on multiple pulse signals with target loading phase. The intermediate pulse laser signal is then processed using attenuator 240 to reduce its intensity to the target pulse laser signal at the single-photon level.

[0085] According to an embodiment of the present invention, the Bob terminal also performs the above-described operation, except that the randomized phase selected by the Bob terminal for every L pulse signals is denoted as θ. B The bit code of the i-th pulse signal at Bob's end is denoted as s. Bi After the first phase modulator 230 at the Bob end processes the i-th pulse signal, the target loading phase of the pulse signal is θ. B +π×s Bi .

[0086] According to an embodiment of the present invention, determining the target quantum key between the transmitting end 200 based on the bit encoding and the detection result sent by the measuring end 100 involves the following operations:

[0087] The detection results sent by the measurement terminal 100 corresponding to the initial laser signal are obtained. The detection results include multiple target position numbers that the measurement terminal 100 confirms as valid responses, and the detector number corresponding to each valid response target position. An XOR operation is performed on the two bit codes corresponding to the two target position numbers to obtain the initial quantum key corresponding to the initial laser signal. The two target position numbers are any two of the multiple target position numbers. A target quantum key is generated based on the multiple initial quantum keys of the multiple initial laser signals.

[0088] According to an embodiment of the present invention, if the Alice end and the Bob end receive information published by the measurement end 100 indicating that the response of the measurement end 100 to the target pulse laser signal is invalid, then the Alice end and the Bob end will discard these L pulses and will not generate any key.

[0089] According to an embodiment of the present invention, when the Alice end and Bob end receive information from the measurement end 100 indicating that the response of the measurement end 100 to the target pulsed laser signal is a valid response, the indices a and b of the two pulse positions published by the measurement end 100 are determined as the two target position indices. Then, the Alice end performs an XOR operation on the bit encoding of its a-th and b-th pulse signals to obtain the initial quantum key, for example... Similarly, Bob's end also performs an XOR operation on the bit codes of the a-th and b-th pulse signals to obtain the initial quantum key, which is... Finally, Alice and Bob each generate the target quantum key based on their multiple initial quantum keys, whereby... This is the XOR operator.

[0090] According to an embodiment of the present invention, the measurement end 100 includes a beam splitter 110 and two single-photon detectors 120 respectively connected to the two output ends of the beam splitter 110.

[0091] According to an embodiment of the present invention, after performing the XOR operation, the following operation is further included:

[0092] If the detection results indicate that the pulse signals corresponding to the two target position numbers are determined to be valid responses by the two single-photon detectors 120, the initial quantum key of one of the two quantum state preparation and transmission terminals 200 is reversed to obtain the reversed qubit as the initial quantum key. This allows one quantum state preparation and transmission terminal 200 to perform an XOR operation and then perform a bit reversal operation to obtain the initial quantum key, while the other quantum state preparation and transmission terminal 200 performs an XOR operation on the qubit to obtain the initial quantum key.

[0093] In other words, if the detection results published by the measurement end 100 show that the two single-photon detectors 120 in the measurement end 100 have made a valid response on the pulse signal corresponding to the two target position numbers, either the Alice end or the Bob end can perform an XOR operation on its own bit code and then perform a bit reversal; the other end can perform an XOR operation based on the original bit code.

[0094] According to an embodiment of the present invention, the detection results published at the measurement end 100 show that the same single-photon detector 120 responded once on the pulse signal corresponding to the two target position numbers, and at this time there is no need to perform a bit reversal operation.

[0095] According to an embodiment of the present invention, the XOR operation means that when both bits are 0 or both are 1, the initial quantum key obtained by the operation is 0, and when the two bits are 0 and 1 respectively, the initial quantum key obtained by the operation is 1.

[0096] It should be noted that when measurement is performed at measurement end 100, assuming that two or more pulse positions (i.e., multiple target position numbers) out of a total of L pulse positions are responded to by single-photon detector 120, measurement end 100 declares this a valid response. Subsequently, measurement end 100 arbitrarily selects two pulse positions that have been responded to by single-photon detector 120 from the multiple pulse positions and sends them to Alice end and Bob end for XOR operation. If measurement end 100 confirms that fewer than two pulse positions out of the L pulse positions have detected a response, then measurement end 100 declares this response an invalid response.

[0097] According to an embodiment of the present invention, a target quantum key is generated based on multiple initial quantum keys from multiple initial laser signals, including the following operations:

[0098] For each initial quantum key, if the absolute value of the difference between the two randomized phases of the two quantum state preparation transmitters 200 corresponding to the initial quantum key is a preset value, the initial quantum key is determined as the sieved key; for the two quantum state preparation transmitters 200, the sieved key is subjected to error correction processing to obtain the error-corrected sieved key; the error-corrected sieved key is subjected to private amplification processing to obtain the target quantum key.

[0099] According to an embodiment of the present invention, for each initial quantum key, the Alice terminal publishes the corresponding randomized phase θ. A Similarly, Bob publishes the randomized phase θ B If the phase θ is randomized A With randomized phase θ B If the absolute value of the difference is a preset value, the initial quantum key is retained and determined as the sieved key; otherwise, Alice and Bob discard this pair of initial quantum keys. The preset value is in the range [0-m, 0+m] or [π-m, π+m], where m is a positive number less than π / 2. The smaller the value of m, the lower the bit error rate of the target quantum key.

[0100] According to an embodiment of the present invention, Alice and Bob perform an error correction step on each sieved key to obtain multiple sieved keys with errors corrected. Then, a private amplification operation is performed on each sieved key with errors corrected to obtain a part of the security key. The final target quantum key is generated based on the multiple parts of the security key.

[0101] Figure 4 A block diagram of a quantum key distribution system according to yet another embodiment of the present invention is shown.

[0102] According to embodiments of the present invention, such as Figure 4As shown, the measurement end 100 includes a beam splitter 110 and two single-photon detectors 120 respectively connected to the two output ends of the beam splitter 110.

[0103] According to an embodiment of the present invention, the measuring end 100 generates a detection result based on multiple target pulse laser signals, including:

[0104] Multiple target pulsed laser signals are subjected to interference processing by a beam splitter 110 to obtain an output signal, which includes a first interference signal and a second interference signal. When the output signal includes the first interference signal and the second interference signal, two single-photon detectors 120 are used to process the interference signal to determine whether the interference signal is a valid response. When the interference signal is determined to be a valid response, the pulse position of the response of the single-photon detector 120 on the interference signal is determined as the detection result, where the pulse position represents the target position number.

[0105] According to an embodiment of the present invention, see Figure 4 Alice and Bob transmit their target pulsed laser signals to the measurement end 100 through an optical channel. The beam splitter 110 performs interference processing on the two target pulsed laser signals to obtain an output signal. Two single-photon detectors 120 process the interference signal output by the beam splitter 110 to determine whether the interference signal can be effectively responded to. If there is an effective response, the pulse position of the response of the single-photon detector 120 on the beam split signal is determined as the detection result.

[0106] Figure 5 A block diagram of a quantum key distribution system according to another embodiment of the present invention is shown.

[0107] According to an embodiment of the present invention, since the light sources in the Alice and Bob ends are phase-locked, the phase difference between the two target pulse laser signals during interference processing is the phase difference encoded by the two first phase modulators 230. In this case, to ensure that the phase difference between the two target pulse laser signals processed by the beam splitter 110 is zero, the phase drift generated in the channel can be compensated before the interference beam splitting process, including:

[0108] like Figure 5 As shown, the second phase modulator 130 is used to perform phase drift compensation processing on a target pulse laser signal to obtain a processed target pulse laser signal, so that the beam splitter 110 can perform interference processing on the target pulse laser signal and the processed target pulse laser signal.

[0109] According to an embodiment of the present invention, the purpose of phase drift compensation processing is to adjust the phase between two target pulse laser signals to eliminate the phase difference between the two target pulse laser signals input to the beam splitter 110 caused by disturbances in the channel.

[0110] It should be noted that in the above embodiments, the present invention only uses Alice and Bob as two quantum state preparation and transmission ends 200 for exemplary description. However, this does not mean that the present invention can only have two quantum state preparation and transmission ends 200. It can be three or more quantum state preparation and transmission ends 200 distributing quantum keys. Secondly, in the above embodiments, only Alice end has been described in more detail. It should be known that the structure of Bob end is the same as that of Alice end, and all the operations of Alice end are performed.

[0111] According to an embodiment of the present invention, the security of this quantum key distribution method is based on the uncertainty of the pulse position of the photon in the prepared target pulsed laser signal, and does not depend on the trustworthiness of the measurement device. The detection results measured by the measurement end 100 do not leak information. Therefore, the entire measurement end 100 of the quantum key distribution system is untrustworthy and can be controlled by any third party (e.g., an eavesdropper). Since the measurement end 100 only acts as a relay, the information encoded by the two communicating parties cannot be inferred from the detection results measured by the measurement end 100. Therefore, the method provided by the present invention is independent of the measurement device.

[0112] In the method provided by this invention, a quantum pulse train is used to encode bit information in the preparation of the target pulsed laser signal. Since the light intensity of the quantum pulse train is weak, the probability of simultaneously detecting the presence of light signals at multiple pulse positions in the entire pulse train is very small. Therefore, it is difficult for any eavesdropper to simultaneously measure the phase difference between two pulse positions in one quantum pulse train and the phase difference between two pulses at the same position in another quantum pulse train. This ensures that the upper bound of the amount of information that an eavesdropper can obtain using any attack method for each quantum pulse train is predictable, without the need for additional monitoring of protocol parameters. Therefore, the method of this invention is parameter-free.

[0113] See Figure 2 The quantum key distribution system includes multiple quantum state preparation and transmission terminals 200 and measurement terminals 100. The quantum state preparation and transmission terminal 200 includes a phase-locked light source 210, a chopper 220, and a first phase modulator 230.

[0114] A phase-locked light source 210 is used to emit an initial laser signal, wherein the phase difference of the initial laser signal generated by multiple quantum states at the transmitter 200 is a preset value.

[0115] Chopper 220 is used to process the initial laser signal to obtain a transition pulse laser signal.

[0116] The first phase modulator 230 is used to perform phase modulation on the transition pulse laser signal to obtain the target pulse laser signal, wherein the phase modulation includes randomized phase and bit-coded phase.

[0117] Multiple quantum state preparation and transmission terminals 200 are respectively connected to the measurement terminal 100 via optical channels. The measurement terminal 100 is used to generate detection results based on multiple target pulse laser signals transmitted by the multiple quantum state preparation and transmission terminals 200.

[0118] The quantum state preparation transmitter 200 is also used to determine the target quantum key among multiple quantum state preparation transmitters 200 based on the bit encoding and the detection results sent by the measurement terminal 100.

[0119] According to embodiments of the present invention, multiple quantum state preparation transmitters send target pulsed laser signals to a measurement terminal. The measurement terminal generates detection results based solely on these multiple target pulsed laser signals. The target quantum key is generated at the quantum state preparation transmitter based on the detection results. Even if an eavesdropper attempts to intercept the measurement terminal, they can only obtain the detection results and not the corresponding target quantum key. This ensures the security of quantum communication even when various security vulnerabilities exist at the measurement terminal. The target pulsed laser signal comprises multiple pulse signals with positional indices. This high-dimensional encoding method, which generates one quantum key bit from multiple pulses, ensures that an eavesdropper cannot simultaneously measure the phase difference between the same pair of pulses from multiple quantum state preparation transmitters. This allows all communicating parties to ensure that an eavesdropper can only obtain a small amount of information without monitoring protocol parameters. Simultaneously, this reduces the difficulty of key generation and enhances the practicality of quantum key distribution.

[0120] According to an embodiment of the present invention, the quantum key distribution system further includes a third-party laser.

[0121] A third-party laser is used to send reference laser signals to multiple quantum state preparation transmitters 200 respectively.

[0122] The quantum state preparation transmitter 200 is also used to adjust the phase of the light source according to the reference laser signal to obtain the initial laser signal.

[0123] According to an embodiment of the present invention, the transition pulse laser signal includes a plurality of pulse signals having position numbers.

[0124] According to an embodiment of the present invention, phase modulation is performed on a transition pulse laser signal to obtain a target pulse laser signal, including:

[0125] For each pulse signal, the bit encoding phase is determined based on the random bits corresponding to the pulse signal;

[0126] The target loading phase of the pulse signal is determined based on the randomized phase and bit-coded phase of the pulse signal.

[0127] An intermediate pulse laser signal is generated based on multiple pulse signals with target loading phases;

[0128] The intermediate pulse laser signal is processed by attenuator 240 to obtain a single-photon level target pulse laser signal.

[0129] According to an embodiment of the present invention, determining the bit-coded phase based on random bits corresponding to a pulse signal includes:

[0130] The random bits of the pulse signal are determined as bit codes;

[0131] When the bit encoding is 0, the bit encoding phase is 0;

[0132] When the bit encoding is 1, the bit encoding phase is π.

[0133] According to an embodiment of the present invention, determining the target quantum key between the transmitting end 200 based on the bit encoding and the detection result sent by the measuring end 100, comprising:

[0134] The detection results sent by the measuring end 100 corresponding to the initial laser signal are obtained. The detection results include multiple target position numbers that the measuring end 100 confirms as valid responses, and the detector number corresponding to each valid response target position.

[0135] Perform an XOR operation on the two bit codes corresponding to the two target position indices to obtain the initial quantum key corresponding to the initial laser signal, wherein the two target position indices are any two of a plurality of target position indices;

[0136] The target quantum key is generated based on multiple initial quantum keys from multiple initial laser signals.

[0137] According to an embodiment of the present invention, the measurement end 100 includes a beam splitter 110 and two single-photon detectors 120 respectively connected to the two output ends of the beam splitter 110;

[0138] According to an embodiment of the present invention, after performing the XOR operation, the method further includes:

[0139] If the detection results indicate that the pulse signals corresponding to the two target position numbers are determined to be valid responses by the two single-photon detectors 120, then one of the two quantum state preparation and transmission terminals 200 performs the XOR operation and then performs bit reversal processing to obtain the initial quantum key.

[0140] According to an embodiment of the present invention, generating a target quantum key based on multiple initial quantum keys from multiple initial laser signals includes:

[0141] For each initial quantum key, if the absolute value of the difference between the two initial phases of the multiple quantum states corresponding to the initial quantum key at the transmitting end 200 is a preset value, the initial quantum key is determined as the sieved key.

[0142] For any quantum state, prepare the transmitter 200, perform error correction on the sieved key, and obtain the error-corrected sieved key;

[0143] The sieved key after error correction is privately amplified to obtain the target quantum key.

[0144] According to an embodiment of the present invention, the measurement end 100 includes a beam splitter 110 and two single-photon detectors 120 respectively connected to the two output ends of the beam splitter 110.

[0145] Beam splitter 110 is used to perform interference processing on multiple target pulse laser signals to obtain an output signal, wherein the output signal includes a first interference signal and a second interference signal;

[0146] Single-photon detector 120, used for:

[0147] When the output signal includes a first interference signal and a second interference signal, the interference is processed.

[0148] The signal is used to determine whether the interference signal is a valid response;

[0149] If the interference signal is determined to be an effective response, the pulse position of the response of the single-photon detector 120 to the interference signal is determined as the detection result, wherein the pulse position represents the target position number.

[0150] According to an embodiment of the present invention, the measuring end 100 further includes a second phase modulator 130.

[0151] The second phase modulator 130 is used to perform phase drift compensation processing on one of the aforementioned target pulse laser signals to obtain a processed target pulse laser signal, so that the beam splitter 110 can perform interference processing on the aforementioned target pulse laser signal and the processed target pulse laser signal.

[0152] It should be noted that the quantum key distribution system part in the embodiments of the present invention corresponds to the quantum key distribution method part in the embodiments of the present invention. The description of the quantum key distribution system part is specifically referred to in the quantum key distribution method part, and will not be repeated here.

[0153] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of the invention is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A quantum key distribution method applied to a quantum key distribution system, wherein, The quantum key distribution system comprises a measurement end and a plurality of quantum state preparation sending ends, each of the quantum state preparation sending ends comprising a phase-locked light source, a chopper and a first phase modulator, and the method comprises the following steps: emitting an initial laser signal by using the phase-locked light source, wherein the phase difference of the initial laser signal of each of the quantum state preparation sending ends is a preset value; processing the initial laser signal by using the chopper to obtain a transition pulse laser signal; phase modulating the transition pulse laser signal by using the first phase modulator to obtain a target pulse laser signal, wherein the phase modulation comprises randomization phase and bit encoding phase; sending the target pulse laser signal from each of the quantum state preparation sending ends to the measurement end, so that the measurement end generates a detection result according to the target pulse laser signal; obtaining the detection result corresponding to the initial laser signal sent by the measurement end, wherein the detection result comprises a plurality of target position serial numbers confirmed as valid responses by the measurement end, and a detector serial number corresponding to each target position of the valid response; performing XOR operation on two target position serial numbers corresponding to two bit encodings to obtain an initial quantum key corresponding to the initial laser signal, wherein the two target position serial numbers are any two of the plurality of target position serial numbers; generating a target quantum key between each of the quantum state preparation sending ends according to a plurality of initial quantum keys of a plurality of initial laser signals.

2. The method of claim 1, further comprising: obtaining reference laser signals sent by a third-party laser to each of the quantum state preparation sending ends; adjusting the light source phase according to the reference laser signal to obtain the initial laser signal for each of the quantum state preparation sending ends.

3. The method of claim 1, wherein the transition pulse laser signal comprises a plurality of pulse signals with position serial numbers; wherein phase modulating the transition pulse laser signal by using the first phase modulator to obtain a target pulse laser signal, comprising: generating a random phase as the randomization phase for each of the transition pulse laser signals; determining the bit encoding phase according to a random bit corresponding to the pulse signal for each of the pulse signals; determining a target loading phase of the pulse signal according to the randomization phase and the bit encoding phase of the pulse signal; generating an intermediate pulse laser signal according to a plurality of pulse signals with the target loading phase; processing the intermediate pulse laser signal by using an attenuator to obtain the target pulse laser signal at a single-photon level.

4. The method of claim 3, wherein, The method of claim 1, wherein determining the bit encoding phase according to a random bit corresponding to the pulse signal comprises: determining the random bit of the pulse signal as the bit encoding; in the case that the bit encoding is 0, the bit encoding phase is 0. In the case that the bit encoding is 1, the bit encoding phase is .

5. The method of claim 1, wherein the measurement end comprises a beam splitter and two single-photon detectors connected to two output ends of the beam splitter, respectively; wherein, after performing the XOR operation, the method further comprises: In a case where the detection result indicates that the pulse signals corresponding to the two target position serial numbers are determined as valid responses by the two single-photon detectors respectively, one of the quantum state preparation sending ends performs the XOR operation and then performs a bit inversion process, as an initial quantum key.

6. The method of claim 1, wherein, The target quantum key is generated according to a plurality of initial quantum keys of the plurality of initial laser signals, including: For each initial quantum key, in a case where the absolute value of the difference between the two randomization phases of the quantum state preparation sending ends corresponding to the initial quantum key is a preset value, the initial quantum key is determined as a post-screening key; For a plurality of quantum state preparation sending ends, the post-screening key is subjected to error correction processing to obtain a post-screening key after error correction; The post-screening key after error correction is subjected to private amplification processing to obtain the target quantum key.

7. The method of claim 1, wherein the measurement end comprises a beam splitter and two single-photon detectors respectively connected to two output ends of the beam splitter; wherein, The measurement end generates a detection result according to a plurality of target pulse laser signals, including: The beam splitter is used to interfere with a plurality of target pulse laser signals to obtain an output signal, wherein the output signal comprises a first interference signal and a second interference signal; For the first interference signal and the second interference signal included in the output signal, two single-photon detectors are used to process the interference signals respectively to determine whether the interference signals are valid responses; In a case where the interference signals are determined as valid responses, the pulse position of the response of the single-photon detector on the interference signal is determined as the detection result, wherein the pulse position represents the target position serial number.

8. The method of claim 7, wherein, Before the interference processing, further comprising: A second phase modulator is used to perform phase drift compensation processing on one target pulse laser signal to obtain a processed target pulse laser signal, so that the beam splitter interferes with the target pulse laser signal and the processed target pulse laser signal.

9. A quantum key distribution system, comprising: A plurality of quantum state preparation sending ends, the quantum state preparation sending ends comprising: A phase-locked light source for emitting an initial laser signal, wherein the phase difference of the initial laser signals of the plurality of quantum state preparation sending ends is a preset value; A chopper for processing the initial laser signal to obtain a transition pulse laser signal; A first phase modulator for phase modulating the transition pulse laser signal to obtain a target pulse laser signal, wherein the phase modulation includes a randomization phase and a bit encoding phase; A measurement end, a plurality of quantum state preparation sending ends are respectively connected to the measurement end through an optical channel, and the measurement end is used to generate a detection result according to a plurality of target pulse laser signals sent by a plurality of quantum state preparation sending ends; Wherein, the quantum state preparation sending end is further used: Obtaining the detection result corresponding to the initial laser signal sent by the measuring end, wherein the detection result includes a plurality of target position serial numbers confirmed as valid responses by the measuring end, and a detector serial number corresponding to each valid response target position; XOR operation is performed on two bit encodings corresponding to two target position serial numbers to obtain an initial quantum key corresponding to the initial laser signal, wherein the two target position serial numbers are any two of the plurality of target position serial numbers; According to the plurality of initial quantum keys of the plurality of initial laser signals, a target quantum key between the plurality of quantum state preparation sending ends is generated.

Images