A multi-user TF-QKD network system and an implementation method thereof

Abstract

A multi-user TF-QKD network system and an implementation method, relate to the technical field of quantum secure communication and optical communication, wherein the multi-user TF-QKD network system comprises a measurement end and a plurality of user ends directly and independently connected with the measurement end; the measurement end is used for counting the communication applications sent by the user ends to determine interference pairing, and allocating time windows to the corresponding user ends according to the interference pairing; the user end adjusts the frequency and delay of the pulse according to the time window allocated by the measurement end, modulates the signal, and sends the modulated single-photon-level quantum signal to the measurement end; the measurement end is also used for interference of the single-photon-level quantum signal in the corresponding time window, and coding according to the response. The application realizes the multi-user TF-QKD in a time division multiplexing mode, and has a high coding rate in long-distance quantum communication.

Description

Technical Field

[0001] This application relates to the fields of quantum secure communication and optical communication technology, specifically to a multi-user TF-QKD network system and its implementation method. Background Technology

[0002] Quantum Key Distribution (QKD) is a core area of ​​quantum communication development, possessing a relatively mature theoretical framework. QKD refers to the process by which legitimate users utilize the principles of quantum mechanics to acquire information loaded onto quantum states through open quantum channels. During legitimate user communication, even if eavesdropping occurs, it can be detected by leaving traces, thus ensuring the security of information transmission and theoretically achieving an absolutely secure communication method.

[0003] The BB84 protocol, the first QKD protocol in history, proved the security of QKD. Subsequently, the Twin-field (TF) QKD protocol was proposed, which can break the PLOB limit without quantum repeaters, greatly improving the code generation rate of communication, and this protocol is immune to all attacks targeting measurement devices.

[0004] However, existing TF-QKD networks often adopt a ring structure, where both users follow the same path and share losses. This ring structure limits multi-user communication to short distances. Summary of the Invention

[0005] This application provides a multi-user TF-QKD network system and its implementation method, which implements multi-user TF-QKD using time-division multiplexing and has a high key generation rate in long-distance quantum communication.

[0006] In a first aspect, embodiments of this application provide a multi-user TF-QKD network system, the multi-user TF-QKD network system including a measurement terminal and multiple user terminals directly and independently connected to the measurement terminal;

[0007] The measuring terminal is used to count the communication requests sent by the user terminal to determine interference pairing, and to allocate time windows to the corresponding user terminal according to the interference pairing;

[0008] The user terminal adjusts the frequency and delay of the pulse according to the time window allocated by the measurement terminal, modulates the signal, and sends the modulated single-photon quantum signal to the measurement terminal.

[0009] The measurement end is also used to perform single-photon-level quantum signal interference within the corresponding time window and to generate codes based on the response.

[0010] In conjunction with the first aspect, in one embodiment, the measuring end includes:

[0011] A measurement-end relay device is used to count the communication requests sent by the user terminal to determine interference pairing, and to allocate time windows to the corresponding user terminal according to the interference pairing;

[0012] A multi-port interferometer is used to receive single-photon-level quantum signals sent by the user terminal and to perform single-photon-level quantum signal interference within a corresponding time window;

[0013] Two single-photon detectors, each connected to the multi-port interferometer, are used to respond to the interference of single-photon level quantum signals and to generate codes based on the response.

[0014] In conjunction with the first aspect, in one implementation, the measurement relay device distributes the time window evenly according to the number of interference pairs.

[0015] In conjunction with the first aspect, in one implementation, the user terminal includes:

[0016] A laser, used to output an optical carrier wave;

[0017] An intensity modulator that modulates the signal intensity based on the optical carrier and prepares a decoy state;

[0018] A phase modulator is used to modulate the signal output by the intensity modulator to produce an optical signal carrying bit phase information and basis vector phase information.

[0019] A tunable optical attenuator is used to attenuate the optical signal output by the phase modulator to the single-photon level.

[0020] In conjunction with the first aspect, in one implementation, the multi-user TF-QKD network system includes five user terminals.

[0021] Secondly, embodiments of this application provide a method for implementing a multi-user TF-QKD network, the method comprising:

[0022] The measurement terminal counts communication requests sent by multiple user terminals that are directly and independently connected to the measurement terminal to determine interference pairing, and allocates time windows to the corresponding user terminals according to the interference pairing;

[0023] The user terminal adjusts the frequency and delay of the pulse according to the time window allocated by the measurement terminal, modulates the signal, and sends the modulated single-photon quantum signal to the measurement terminal.

[0024] The measuring end performs single-photon-level quantum signal interference within the corresponding time window and codes it according to the response.

[0025] In conjunction with the second aspect, in one implementation, the measurement terminal relay device is used to count the communication requests sent by the user terminal to determine interference pairing, and a time window is allocated to the corresponding user terminal according to the interference pairing;

[0026] A multi-port interferometer is used to receive single-photon-level quantum signals sent by the user terminal, and single-photon-level quantum signal interference is performed within the corresponding time window;

[0027] The interference of single-photon level quantum signals is achieved by using two single-photon detectors, both connected to the multi-port interferometer, and the response is encoded.

[0028] In conjunction with the second aspect, in one implementation, the measurement relay device distributes the time window evenly according to the number of interference pairs.

[0029] In conjunction with the second aspect, in one implementation, the user-end modulation of the single-photon-level quantum signal includes:

[0030] Utilizing a laser to output an optical carrier wave;

[0031] An intensity modulator is used to modulate the signal based on the optical carrier and prepare a decoy state.

[0032] The signal output from the intensity modulator is modulated using a phase modulator to produce an optical signal carrying bit phase information and basis vector phase information.

[0033] An adjustable optical attenuator is used to attenuate the optical signal output by the phase modulator to the single-photon level.

[0034] In conjunction with the second aspect, in one implementation, the number of user terminals is 5.

[0035] The beneficial effects of the technical solutions provided in this application include at least the following:

[0036] The multi-user TF-QKD network system in this application includes a measurement end and multiple user ends directly and independently connected to the measurement end. The measurement end is used to count the communication requests sent by the user ends to determine interference pairings and allocate time windows to the corresponding user ends according to the interference pairings. The user ends are used to perform signal modulation within the allocated time windows and send the modulated single-photon-level quantum signal to the measurement end. The measurement end is also used to perform single-photon-level quantum signal interference within the corresponding time windows and code according to the response.

[0037] This application implements a multi-user TF-QKD network system using time-division multiplexing, achieving a high key generation rate in long-distance quantum communication. The scheme presented in this application has the advantages of simple structure, easy implementation based on existing technology, and strong practicality; secondly, the system is a measurement-independent system, resistant to attacks targeting measurement devices; furthermore, the system can simultaneously execute multiple sets of TF-QKD protocols, greatly saving network resources. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating an embodiment of the multi-user TF-QKD network implementation method of this application.

[0039] Figure 2 This is a structural block diagram of an embodiment of the multi-user TF-QKD network system of this application;

[0040] Figure 3 This is a structural diagram of the user side of this application. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0042] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus. The terms "first," "second," and "third," etc., are used to distinguish different objects, etc., and do not indicate a sequence, nor do they limit "first," "second," and "third" to different types.

[0043] In the description of the embodiments of this application, terms such as "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a concrete manner.

[0044] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0045] In some processes described in the embodiments of this application, multiple operations or steps are included in a specific order. However, it should be understood that these operations or steps may not be executed in the order they appear in the embodiments of this application, or they may be executed in parallel. The sequence number of the operation is only used to distinguish different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed sequentially or in parallel, and these operations or steps may be combined.

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0047] In a first aspect, embodiments of this application provide a method for implementing a multi-user TF-QKD network.

[0048] In one embodiment, reference is made to Figure 1 , Figure 1 This is a flowchart illustrating an embodiment of the multi-user TF-QKD network implementation method of this application. Figure 1 As shown, the implementation methods for multi-user TF-QKD networks include:

[0049] S1. The measurement end counts the communication requests sent by multiple user terminals that are directly and independently connected to the measurement end to determine the interference pairing, and allocates a time window to the corresponding user terminal according to the interference pairing;

[0050] S2. The user terminal adjusts the frequency and delay of the pulse according to the time window allocated by the measurement terminal, modulates the signal, and sends the modulated single-photon quantum signal to the measurement terminal.

[0051] S3. The measurement end performs single-photon-level quantum signal interference within the corresponding time window and codes according to the response.

[0052] It is worth noting that existing TF-QKD networks often employ a ring structure, where both users follow the same path and share losses. This ring structure limits multi-user communication to short distances. In this embodiment, see... Figure 2 As shown, each user terminal connects directly and independently to the measurement terminal, similar to a star communication structure. The different communication paths between the two parties allow for extended communication distances.

[0053] In practice, a measurement relay device can be used to count the communication requests sent by the user terminal to determine interference pairings, and a time window can be allocated to the corresponding user terminal according to the interference pairings. Then, a multi-port interferometer can be used to receive the single-photon-level quantum signal sent by the user terminal and perform single-photon-level quantum signal interference within the corresponding time window. Then, two single-photon detectors, both connected to the multi-port interferometer, can be used to respond to the interference of the single-photon-level quantum signal and code it according to the response.

[0054] Generally speaking, in the absence of communication users requesting to occupy more network resources, the measurement end relay device will by default distribute the time window evenly according to the number of interference pairs. The measurement end relay device can be a computer or other devices.

[0055] For the user end, it is mainly used to transmit signals and perform modulation and coding (following the TF-QKD protocol), see [link / reference]. Figure 3 As shown, it includes a laser LASER, an intensity modulator IM, a phase modulator PM (two PMs are used in this embodiment), and a tunable optical attenuator VOA connected in sequence.

[0056] The main process for the user to send a single-photon-level quantum signal is as follows:

[0057] A laser is used to output an optical carrier; an intensity modulator is used to modulate the signal based on the optical carrier and prepare a decoy state; a phase modulator is used to modulate the signal output by the intensity modulator to produce an optical signal carrying bit phase information and basis vector phase information; and an adjustable optical attenuator is used to attenuate the optical signal output by the phase modulator to the single-photon level.

[0058] The measurement end divides time windows according to the network's full-load frequency and assigns each time window to two different users for interference. Each user sends a single-photon-level quantum signal to the corresponding assigned time window for interference, and the signal is encoded based on the detector's response.

[0059] It is worth noting that in the TF-QKD protocol, the states sent by Alice and Bob, the two communicating parties, are as follows:

[0060]

[0061]

[0062] Where |0> and |1> represent the vacuum state and the single-photon state, respectively. and Let X be the phase of the prepared quantum state, and when the X basis vector is chosen... When selecting the Y basis vector When the quantum states of Alice and Bob interfere at the measurement end, the detector at the measurement end responds. Based on the detector's response, coding is performed. The coding rate of TF-QKD is:

[0063]

[0064] Among them, Q μ It is the total gain, E μ The error rate is given by: Q1 is the lower limit of single-photon gain, e1 is the upper limit of single-photon error rate, M is the number of equally divided slices during random phase modulation, H2 is the binary Shannon entropy, and f is the error correction efficiency.

[0065] The following is a specific example to further illustrate this:

[0066] This embodiment is designed as follows: Figure 2 The multi-user TF-QKD network system structure shown is used for communication between two parties to perform the TF-QKD process. It includes N user terminals (N=5 in this example) connected by a bidirectional channel and a measurement terminal. The measurement terminal includes a multi-port interferometer U and two single-photon detectors DET. Any two user terminals can be the two communicating parties.

[0067] 1. Assume the full-load frequency of the measuring end is f;

[0068] 2. Establish time window rules for interference at the measurement end:

[0069] Rule: Both communicating parties first submit a communication request to the measurement end relay device. The measurement end relay device integrates all communication requests and allocates time windows to the corresponding users according to the requests. Users negotiate the transmission time of the optical pulse according to the allocated time window.

[0070] In this embodiment, all users who want to communicate send a request to the measurement terminal relay device. The measurement terminal relay device counts all user requests. For example, user 1 communicates with user 4 and user 5 respectively, user 4 communicates with user 1 and user 2 respectively, and user 3 communicates with user 5. At this time, there are 4 interference pairs in the network at the same time: interference pair 1: user 1 communicates with user 4; interference pair 2: user 1 communicates with user 5; interference pair 3: user 2 communicates with user 4; interference pair 4: user 3 communicates with user 5.

[0071] In the absence of any communication user requesting to occupy more network resources, the measurement end relay device defaults to evenly allocating the time window based on the number of interference pairs. Thus, each interference pair is allocated 1 / 4 of the time window. Based on the time window allocated by the interference pairs, users 1, 4, and 5 occupy 1 / 2 of the time window, while users 2 and 3 occupy 1 / 4 of the time window.

[0072] 3. The user modulates the signal according to the agreed time window, and then sends the modulated light pulse;

[0073] 4. The signal modulated by both communicating parties enters the multi-port interferometer at the measurement end and undergoes single-photon interference within the corresponding time window, and is encoded according to the detector's response.

[0074] 5. Both parties in the communication process perform post-processing.

[0075] Therefore, it can be seen that in this embodiment, the multi-user TF-QKD network system can support N groups of TF-QKD simultaneously, and the quantum signal sent by any user can reach the measurement end of the quantum network, enabling one user to communicate with multiple users.

[0076] In summary, the multi-user TF-QKD network implementation method in this application determines interference pairings by statistically analyzing communication requests issued by multiple user terminals directly and independently connected to the measurement terminal, and allocates time windows to the corresponding user terminals according to the interference pairings; the user terminals perform signal modulation within the allocated time windows and send the modulated single-photon-level quantum signal to the measurement terminal; the measurement terminal performs single-photon-level quantum signal interference within the corresponding time window and encodes the signal according to the response.

[0077] This application implements a multi-user TF-QKD network system using time-division multiplexing, achieving a high key generation rate in long-distance quantum communication. The scheme presented in this application has the advantages of simple structure, easy implementation based on existing technology, and strong practicality; secondly, the system is a measurement-independent system, resistant to attacks targeting measurement devices; furthermore, the system can simultaneously execute multiple sets of TF-QKD protocols, greatly saving network resources.

[0078] Secondly, embodiments of this application provide a multi-user TF-QKD network system.

[0079] In one embodiment, reference is made to Figure 2 , Figure 2 This is a structural block diagram of an embodiment of the multi-user TF-QKD network system of this application. Figure 2 As shown, the multi-user TF-QKD network system includes: a measurement terminal and multiple user terminals that are directly and independently connected to the measurement terminal.

[0080] The measuring end is used to count the communication requests sent by the user terminal to determine interference pairings, and allocate time windows to the corresponding user terminals according to the interference pairings. The user terminal adjusts the frequency and delay of the pulse according to the time window allocated by the measuring end, modulates the signal, and sends the modulated single-photon-level quantum signal to the measuring end. The measuring end is also used to perform single-photon-level quantum signal interference within the corresponding time window and code it according to the response.

[0081] Furthermore, in one embodiment, the measuring end includes:

[0082] A measurement-end relay device is used to count the communication requests sent by the user terminal to determine interference pairing, and to allocate time windows to the corresponding user terminal according to the interference pairing;

[0083] A multi-port interferometer is used to receive single-photon-level quantum signals sent by the user terminal and to perform single-photon-level quantum signal interference within a corresponding time window;

[0084] Two single-photon detectors, each connected to the multi-port interferometer, are used to respond to the interference of single-photon level quantum signals and to generate codes based on the response.

[0085] Furthermore, in one embodiment, the measurement end includes: the measurement end relay device evenly distributing the time window according to the number of interference pairs.

[0086] Furthermore, in one embodiment, see... Figure 3 As shown, the user terminal includes:

[0087] A laser, used to output an optical carrier wave;

[0088] An intensity modulator that modulates the signal intensity based on the optical carrier and prepares a decoy state;

[0089] A phase modulator is used to modulate the signal output by the intensity modulator to produce an optical signal carrying bit phase information and basis vector phase information.

[0090] A tunable optical attenuator is used to attenuate the optical signal output by the phase modulator to the single-photon level.

[0091] Furthermore, in one embodiment, the multi-user TF-QKD network system includes 5 user terminals.

[0092] The functions of each device in the above-mentioned multi-user TF-QKD network system correspond to the steps in the above-mentioned multi-user TF-QKD network implementation method embodiment, and their functions and implementation processes will not be described in detail here.

[0093] In summary, the multi-user TF-QKD network system of this application includes a measurement end and multiple user ends directly and independently connected to the measurement end; the measurement end is used to count the communication requests issued by the user ends to determine interference pairings, and allocate time windows to the corresponding user ends according to the interference pairings; the user ends are used to perform signal modulation within the allocated time windows and send the modulated single-photon-level quantum signal to the measurement end; the measurement end is also used to perform single-photon-level quantum signal interference within the corresponding time windows and code according to the response.

[0094] This application implements a multi-user TF-QKD network system using time-division multiplexing, achieving a high key generation rate in long-distance quantum communication. The scheme presented in this application has the advantages of simple structure, easy implementation based on existing technology, and strong practicality; secondly, the system is a measurement-independent system, resistant to attacks targeting measurement devices; furthermore, the system can simultaneously execute multiple sets of TF-QKD protocols, greatly saving network resources.

[0095] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A multi-user TF-QKD network system, characterized in that: The multi-user TF-QKD network system includes a measurement terminal and multiple user terminals that are directly and independently connected to the measurement terminal; The measuring terminal is used to count the communication requests sent by the user terminal to determine interference pairing, and to allocate time windows to the corresponding user terminal according to the interference pairing; The user terminal adjusts the frequency and delay of the pulse according to the time window allocated by the measurement terminal, modulates the signal, and sends the modulated single-photon quantum signal to the measurement terminal. The measurement end is also used to perform single-photon-level quantum signal interference within the corresponding time window and to generate codes based on the response.

2. The multi-user TF-QKD network system as described in claim 1, characterized in that, The measuring end includes: A measurement-end relay device is used to count the communication requests sent by the user terminal to determine interference pairing, and to allocate time windows to the corresponding user terminal according to the interference pairing; A multi-port interferometer is used to receive single-photon-level quantum signals sent by the user terminal and to perform single-photon-level quantum signal interference within a corresponding time window; Two single-photon detectors, each connected to the multi-port interferometer, are used to respond to the interference of single-photon level quantum signals and to generate codes based on the response.

3. The multi-user TF-QKD network system as described in claim 2, characterized in that: The measurement relay device distributes the time window evenly based on the number of interference pairs.

4. The multi-user TF-QKD network system as described in claim 1, characterized in that, The user terminal includes: A laser, used to output an optical carrier wave; An intensity modulator that modulates the signal intensity based on the optical carrier and prepares a decoy state; A phase modulator is used to modulate the signal output by the intensity modulator to produce an optical signal carrying bit phase information and basis vector phase information. A tunable optical attenuator is used to attenuate the optical signal output by the phase modulator to the single-photon level.

5. The multi-user TF-QKD network system as described in claim 1, characterized in that, The multi-user TF-QKD network system includes 5 user terminals.

6. A method for implementing a multi-user TF-QKD network, characterized in that: The multi-user TF-QKD network implementation method includes: The measurement terminal counts communication requests sent by multiple user terminals that are directly and independently connected to the measurement terminal to determine interference pairing, and allocates time windows to the corresponding user terminals according to the interference pairing; The user terminal adjusts the frequency and delay of the pulse according to the time window allocated by the measurement terminal, modulates the signal, and sends the modulated single-photon quantum signal to the measurement terminal. The measuring end performs single-photon-level quantum signal interference within the corresponding time window and codes it according to the response.

7. The multi-user TF-QKD network implementation method as described in claim 6, characterized in that: The communication requests sent by the user terminal are counted using the measurement terminal relay equipment to determine interference pairing, and a time window is allocated to the corresponding user terminal according to the interference pairing; A multi-port interferometer is used to receive single-photon-level quantum signals sent by the user terminal, and single-photon-level quantum signal interference is performed within the corresponding time window; The interference of single-photon level quantum signals is achieved by using two single-photon detectors, both connected to the multi-port interferometer, and the response is encoded.

8. The multi-user TF-QKD network implementation method as described in claim 7, characterized in that: The measurement relay device distributes the time window evenly based on the number of interference pairs.

9. The multi-user TF-QKD network implementation method as described in claim 6, characterized in that, The user-end modulation of single-photon-level quantum signals includes: Utilizing a laser to output an optical carrier wave; An intensity modulator is used to modulate the signal based on the optical carrier and prepare a decoy state. The signal output from the intensity modulator is modulated using a phase modulator to produce an optical signal carrying bit phase information and basis vector phase information. An adjustable optical attenuator is used to attenuate the optical signal output by the phase modulator to the single-photon level.

10. The multi-user TF-QKD network implementation method as described in claim 6, characterized in that, The number of user terminals is 5.

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