CN115580355B

CN115580355B - Quantum communication coding and decoding method compatible with multiple coding systems

Info

Publication number: CN115580355B
Application number: CN202211451656.6A
Authority: CN
Inventors: 王纺翔; 陈巍; 王双; 银振强; 何德勇; 周政; 范元冠杰; 郭光灿; 韩正甫
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2022-11-18
Filing date: 2022-11-18
Publication date: 2023-03-10
Anticipated expiration: 2042-11-18
Also published as: CN115580355A

Abstract

The invention provides a quantum communication encoding and decoding method compatible with multiple encoding systems and a network system, which are applied to the technical field of quantum communication and quantum information processing. The coding method and the decoding method are respectively applied to a sender and a receiver in a quantum communication network compatible with multiple coding systems. A sender encodes photons to be sent through N encoding degrees of freedom, and the encoding method comprises the following steps: acquiring decoding information of a receiver, and decoding the quantum state signal by the receiver through M decoding degrees of freedom; determining the same F target degrees of freedom from the N encoding degrees of freedom and the M decoding degrees of freedom in the presence of the same degrees of freedom between the N encoding degrees of freedom and the M decoding degrees of freedom; and encoding the photons to be transmitted by using the F target degrees of freedom to obtain a modulated quantum state signal, so that a receiving party decodes and detects the quantum state signal by using the F target degrees of freedom.

Description

Quantum communication coding and decoding method compatible with multiple coding systems

Technical Field

The invention relates to the field of quantum communication and quantum information processing, in particular to a quantum communication encoding and decoding method compatible with a multi-coding system and a network system.

Background

Quantum communication refers to the realization of information theory-based secure information transmission between different users by using the fundamental principle of Quantum mechanics, including point-to-point direct Quantum Key Distribution (QKD), quantum network, and the like. Photons are the most important information carriers for long-distance communication, and the loading, transmission and decoding of information are realized by modulating and demodulating coherent light fields or photon states in classical optical communication and quantum communication.

In the related art, the point-to-point QKD and QKD networks generally use two-dimensional quantum states for encoding and decoding, such as polarization encoding, time stamp encoding, phase encoding, spatial mode encoding, frequency encoding, and the like. For example, chinese patent publication No. CN 109150522A. The most commonly used QKD codec systems include a polarization-encoded QKD system and a time stamp-phase encoded QKD system. QKD architectures based on polarization or timestamp-phase encoding and decoding have deployed large-scale metropolitan and wide-area quantum communication networks, respectively. However, the QKD networks of both coding schemes have the problems of high requirements on quantum channel and system bit error rate and low secure key distribution rate.

In addition, the QKD systems and the quantum networks of the two coding systems cannot be directly interconnected, so that the large-scale, generalized and low-cost construction and application of the quantum communication network are limited.

Disclosure of Invention

In view of the above problems, the present invention provides a quantum communication encoding and decoding method and a network system compatible with multiple encoding systems.

According to a first aspect of the present invention, a quantum communication encoding method is provided, which is applied to a sender in a quantum communication network compatible with multiple encoding systems, where the quantum communication network includes multiple network nodes, and the sender encodes photons to be sent through N encoding degrees of freedom, where N is greater than or equal to 2.

The encoding method comprises the following steps: the method comprises the steps of obtaining decoding information of a receiver to be subjected to quantum communication in a quantum communication network, wherein the decoding information comprises M decoding degrees of freedom adopted by the receiver, the receiver decodes received quantum state signals through the M decoding degrees of freedom, M is more than or equal to 2 and is less than or equal to N, a sender and the receiver are network nodes in the quantum communication network, and the modulation dimensionality of each coding degree of freedom and each decoding degree of freedom is more than or equal to 2.

In the case where there are identical degrees of freedom between the N encoding degrees of freedom and the M decoding degrees of freedom, the same F target degrees of freedom are determined from the N encoding degrees of freedom and the M decoding degrees of freedom, where F ≧ 1.

And encoding the photons to be transmitted by utilizing the F target degrees of freedom to obtain a modulated quantum state signal, so that a receiving party can decode and detect the quantum state signal by utilizing the F target degrees of freedom.

The N coding degrees of freedom are modulated by N independent coding modules with different degrees of freedom, and quantum state subspaces modulated by the independent coding modules with different degrees of freedom are orthogonal to each other; the M decoding degrees of freedom are modulated by independent decoding modules with M different degrees of freedom, and quantum state subspaces modulated by the independent decoding modules with the different degrees of freedom are orthogonal to each other.

Alternatively, in the case where there are the same degrees of freedom between the N encoding degrees of freedom and the M decoding degrees of freedom, determining the same F target degrees of freedom from the N encoding degrees of freedom and the M decoding degrees of freedom includes: in the case where it is determined that N is equal to M and that the N encoding degrees of freedom and the M decoding degrees of freedom are the same, the N encoding degrees of freedom are taken as F target degrees of freedom.

Alternatively, in the case where there are the same degrees of freedom between the N encoding degrees of freedom and the M decoding degrees of freedom, determining the same F target degrees of freedom from the N encoding degrees of freedom and the M decoding degrees of freedom includes: in a case where it is determined that N is greater than M and M encoding degrees of freedom identical to M decoding degrees of freedom exist among the N encoding degrees of freedom, the M encoding degrees of freedom are taken as F target degrees of freedom.

Alternatively, the encoding of the photons to be transmitted by using F target degrees of freedom to obtain the modulated quantum state signal includes: determining F independent coding modules corresponding to the F target degrees of freedom from the N independent coding modules; shutting down (N-F) independent encoding modules except the F independent encoding modules from the N independent encoding modules; and finishing the encoding of the photons to be transmitted under F degrees of freedom by utilizing F independent encoding modules to obtain modulated quantum state signals.

Alternatively, the method further comprises: determining a target relay node under the condition that N is greater than M and N coding degrees of freedom are not the same as M decoding degrees of freedom, wherein the target relay node is respectively connected with a sender and a receiver, P modulation degrees of freedom are the same as the sender, and Q modulation degrees of freedom are the same as the receiver; quantum key distribution based on a quantum communication protocol between a target relay node and a receiver is realized through the target relay node, wherein P is more than or equal to 1, Q is more than or equal to 1, and the modulation dimension of each modulation degree of freedom is more than or equal to 2; in the process of quantum key distribution, a sender utilizes P modulation degrees of freedom to encode photons to be sent, and a receiver utilizes Q modulation degrees of freedom to decode and detect quantum state signals.

Alternatively, the method further comprises: under the condition that K receivers exist and T modulation degrees of freedom identical to those of the sender exist in the K receivers, the T modulation degrees of freedom are utilized to encode photons to be sent to obtain modulated quantum state signals, the quantum state signals are sent to the K receivers in a broadcasting mode, the K receivers can decode and detect the received quantum state signals by utilizing the T modulation degrees of freedom, wherein K is more than or equal to 2, and T is more than or equal to 1.

Alternatively, the method further comprises: when T is more than or equal to 2, the Tth degree of freedom in the T modulation degrees of freedom is adjusted _i The modulation freedom degree is used as the resource multiplexing freedom degree, wherein, the K receiving sides respectively correspond to the Tth _i K multiplexing channels under the modulation freedom degree, wherein the K multiplexing channels are mutually orthogonal; and when the T is equal to 1 and the adjustable dimensionality of the modulation freedom degree is greater than or equal to K +2, taking K dimensionalities in the modulation freedom degree as resource multiplexing freedom degrees, wherein K receiving sides respectively correspond to K multiplexing channels, and the K multiplexing channels are mutually orthogonal.

Alternatively, wherein the receiver and the sender communicate based on a quantum communication protocol, the quantum communication protocol comprising one of: the BB84 protocol; a high-dimensional QKD protocol; two or more groups are free of bias groups; the encoding degree of freedom and the decoding degree of freedom include at least one of: polarization, timestamp, phase, spatial mode, and frequency; wherein the spatial pattern comprises one of: a multi-path mode of the multi-core fiber; a multi-path mode of the optical chip; laguerre gaussian mode; bessel mode.

According to a second aspect of the present invention, a quantum communication decoding method is provided, which is applied to a receiving party in a quantum communication network compatible with multiple coding systems, where the quantum communication network includes multiple network nodes, and the receiving party decodes a received quantum state signal through M decoding degrees of freedom, where M is greater than or equal to 2.

The decoding method comprises the following steps: the method comprises the steps of obtaining coding information of a sender to be subjected to quantum communication in a quantum communication network, wherein the coding information comprises N coding degrees of freedom adopted by a receiver, the sender codes photons to be sent through the N coding degrees of freedom, N is more than or equal to 2, N is more than or equal to M, the sender and the receiver are network nodes in the quantum communication network, and the modulation dimensionality of each coding degree of freedom and each decoding degree of freedom is more than or equal to 2.

And decoding and detecting the received quantum state signals by using the F target degrees of freedom, wherein the quantum state signals are obtained by encoding photons to be transmitted by a transmitter by using the F target degrees of freedom.

The N coding degrees of freedom are modulated by N independent coding modules with different degrees of freedom, and quantum state subspaces modulated by the independent coding modules with different degrees of freedom are orthogonal to each other; the M decoding degrees of freedom are modulated by independent decoding modules with M different degrees of freedom, and quantum state subspaces modulated by the independent decoding modules with different degrees of freedom are orthogonal to each other.

According to a third aspect of the present invention, there is provided a quantum communication network system compatible with multiple coding schemes, the quantum communication network comprising a plurality of network nodes, each of the plurality of network nodes being configured to serve as a sender or a receiver in a quantum communication process.

The sender includes: a quantum key distribution transmitting terminal; the quantum key distribution transmitting terminal comprises N cascaded independent coding modules, the N independent coding modules are used for coding N different degrees of freedom, quantum state subspaces modulated by the independent coding modules with the different degrees of freedom are orthogonal to each other, and N is larger than or equal to 2.

The receiving side includes: a quantum key distribution receiving end; the quantum key distribution receiving end comprises M cascaded independent decoding modules, the M independent decoding modules are used for decoding M different degrees of freedom, quantum state subspaces modulated by the independent decoding modules with different degrees of freedom are orthogonal to each other, M is more than or equal to 2, and M is less than or equal to N.

The invention provides a quantum communication encoding method and a quantum communication decoding method, which are applied to a quantum communication network compatible with multiple encoding systems. Within the quantum communication network, the sender and receiver may be high-dimensional nodes of different dimensions. Before quantum communication is carried out, the same target degree of freedom between a sender and a receiver is determined, and then the same target degree of freedom is utilized to carry out coding of the sender and decoding of the receiver, so that interconnection and intercommunication among different coding and decoding degrees of freedom, multidimensional QKD systems and networks are finally realized, and the communication scale of a quantum communication network is expanded.

In addition, the encoding and decoding method provided by the invention can realize safe key distribution and compatible networking among the QKD networks, and simultaneously can obviously improve the anti-noise capability and the safe key distribution efficiency of the QKD networks, and expand the usability of different encoding and decoding degrees of freedom and dimensionality QKD systems and networks.

Drawings

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

fig. 1 shows a flow chart of an encoding method of quantum communication according to an embodiment of the present invention.

Fig. 2 shows a schematic encoding flow according to an embodiment of the invention.

Fig. 3 shows a decoding flow diagram according to an embodiment of the invention.

Fig. 4 shows a schematic diagram of a quantum communication network according to an embodiment of the invention.

Fig. 5 shows a flow chart of a decoding method of quantum communication according to an embodiment of the present invention.

Fig. 6 shows a schematic structural diagram of a network node in a quantum communication network system according to an embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It is to be understood that such description is merely illustrative and not intended to limit the scope of the present invention. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

Where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.).

In quantum communication over QKD networks, it is found that QKD networks in the related art typically employ two-dimensional quantum states for encoding and decoding, such as polarization encoded QKD systems and timestamp-phase encoded QKD systems. However, the communication bandwidth, channel noise and the overall quantum bit error rate of the secure communication of the QKD network that employs two-dimensional quantum states for encoding and decoding are limited to a small range, thereby affecting the secure key distribution rate and the versatility of the quantum communication network.

As shown in FIG. 1, the encoding method of this embodiment includes operations S110 to S130.

According to the embodiment of the invention, the quantum communication network comprises a plurality of network nodes, wherein each network node in the plurality of network nodes can be used as a sending party in the quantum communication process and also can be used as a receiving party in another quantum communication process. And the sender encodes the quantum state signal to be sent through N encoding degrees of freedom, wherein N is more than or equal to 2. Among them, a node that encodes or decodes photons with N degrees of freedom of encoding is also referred to as an N-dimensional node.

According to the embodiment of the invention, the plurality of network nodes in the quantum communication network can be network nodes with multiple dimensions, such as two-dimensional nodes, three-dimensional nodes, four-dimensional nodes \8230; \8230, N-dimensional nodes and the like.

In operation S110, decoding information of a receiver to be subjected to quantum communication in a quantum communication network is acquired.

According to an embodiment of the present invention, before quantum communication is performed, the encoding degree of freedom or the decoding degree of freedom of a plurality of network nodes in the quantum communication network has been stored as public information to a base station or a preset storage address.

When quantum communication is carried out, a sender acquires decoding information of a receiver to be subjected to quantum communication from a preset storage address. Specifically, the obtained decoding information includes M decoding degrees of freedom possessed by the receiving party, wherein M is greater than or equal to 2, and M is less than or equal to N.

It should be noted that the sender may encode photons by using all encoding degrees of freedom to obtain a modulated quantum state signal; and coding can be carried out by utilizing one or more coding degrees of freedom which are the same as those of the receiving party to obtain the modulated quantum state signal. Similarly, the receiver can decode and detect the received quantum state signal by using all decoding degrees of freedom; decoding and detection may also be performed using the same one or more decoding degrees of freedom as the receiving party.

In the case where the sender and the receiver do not have the same degree of freedom, the sender may encode using the same one or more encoding degrees of freedom as the target relay node; the receiver may decode using the same one or more decoding degrees of freedom as the target relay node.

Further, the modulation dimension of each encoding degree of freedom and each decoding degree of freedom is greater than or equal to 2 for both the transmitting side and the receiving side. For example, for the coding degree of freedom F ₁ Using the coding degree of freedom F ₁ When the code modulation is carried out, the initial state photons to be transmitted are modulated to the degree of freedom F of the code ₁ At least two subspaces below.

In operation S120, in the case where the same degree of freedom exists between the N encoding degrees of freedom and the M decoding degrees of freedom, the same F target degrees of freedom are determined from the N encoding degrees of freedom and the M decoding degrees of freedom, where F ≧ 1.

According to embodiments of the present invention, an N-dimensional node may be encoded with N different types of degrees of freedom, and an M-dimensional node may be decoded with M different types of degrees of freedom. In the process of directly carrying out quantum communication between a sender and a receiver, the same type of freedom degrees are needed to be adopted for encoding and decoding photons.

According to an embodiment of the invention, in case there are the same degrees of freedom between the N encoding degrees of freedom and the M decoding degrees of freedom, the same F target degrees of freedom are determined from the N encoding degrees of freedom and the M decoding degrees of freedom. Wherein, for the sender, the F target degrees of freedom correspond to the coding degrees of freedom; for the receiving side, the F target degrees of freedom correspond to decoding degrees of freedom.

In operation S130, the photons to be transmitted are encoded by using the F target degrees of freedom to obtain a modulated quantum state signal, so that the receiving side decodes and detects the quantum state signal by using the F target degrees of freedom.

According to the embodiment of the invention, after the F target degrees of freedom are determined, the sender takes the F target degrees of freedom as coding degrees of freedom, and codes the photons to be sent by utilizing the F coding degrees of freedom to obtain the modulated quantum state signals. And the sender sends the modulated quantum state information to the receiver through a quantum channel, so that the receiver decodes and detects the quantum state signal by using the F target degrees of freedom.

The sender comprises a QKD transmitting end and is composed of independent coding modules with N different degrees of freedom. The N coding degrees of freedom are modulated by N independent coding modules of different degrees of freedom, each independent coding module being adapted to modulate one coding degree of freedom. And quantum state subspaces modulated by independent coding modules of different degrees of freedom are orthogonal to each other.

The receiving end comprises a QKD receiving end and consists of M independent decoding modules with different degrees of freedom. The M decoding degrees of freedom are modulated by M independent decoding modules with different degrees of freedom, each independent decoding module is used for modulating one decoding degree of freedom, and quantum state subspaces modulated by the independent decoding modules with different degrees of freedom are orthogonal to each other.

It should be noted that N independent coding modules are cascaded, and the modulation performed by each independent coding module for one degree of freedom does not affect the modulation process of other degrees of freedom. M independent decoding modules are also cascaded, and the modulation of each independent decoding module aiming at one degree of freedom does not influence the modulation process of other degrees of freedom.

According to the embodiment of the invention, the sender and the receiver are both two-dimensional nodes and nodes with higher dimensionality than two dimensions, so that the quantum communication network formed by a plurality of nodes adopts an encoding or decoding method with multiple degrees of freedom.

Specifically, the sender adopts a high-dimensional quantum state encoding method. The high-dimensional quantum states of the high-dimensional QKD networking satisfy the direct product form of the quantum states of different degrees of freedom subspaces, namely:

（1）

wherein,

representing the high-dimensional quantum state after being modulated by N coding degree of freedom states,

representing using a coding degree of freedom F ₁ The modulated quantum state,

Representing degrees of freedom F of coding ₂ The modulated quantum state,

Representing using a coding degree of freedom F _n The modulated quantum state.

The invention provides an encoding method and a decoding method for quantum communication, which are applied to a quantum communication network compatible with a multi-coding system. Within the quantum communication network, the sender and receiver may be high-dimensional nodes of different dimensions. Before quantum communication is carried out, the same target freedom degree between a sender and a receiver is determined, and then the same target freedom degree is utilized to carry out coding of the sender and decoding of the receiver, so that interconnection and intercommunication among different coding and decoding freedom degrees, multidimensional QKD systems and networks are finally realized, and the communication scale of a quantum communication network is expanded.

In addition, the encoding and decoding method provided by the invention can realize safe key distribution and compatible networking among the QKD networks, and simultaneously can obviously improve the anti-noise capability and the safe key distribution efficiency of the QKD networks, and expand the usability of different encoding and decoding degrees of freedom, dimensionality QKD systems and networks.

According to an embodiment of the invention, the encoding degree of freedom and the decoding degree of freedom comprise at least one of: polarization, timestamp, phase, spatial mode, and frequency; wherein the spatial pattern comprises one of: a multi-path mode of the multi-core fiber; a multi-path mode of the optical chip; laguerre gaussian mode; and a bessel mode.

Accordingly, the independent encoding module and the independent decoding module may be one specific modulation module for modulating the above degrees of freedom.

For example, where both the encoding and decoding degrees of freedom include polarization, one independent encoding module and one independent decoding module may be polarization controllers for encoding at the transmitting side or decoding at the receiving side. In case both the encoding and decoding degrees of freedom comprise phases, one independent encoding module and one independent decoding module may act as phase modulators for encoding at the transmitting side or decoding at the receiving side.

According to an embodiment of the invention, the receiver and the sender communicate based on a quantum communication protocol comprising one of: the BB84 protocol; a high-dimensional QKD protocol; and two or more groups of mutually unbiased groups.

The high-dimensional QKD protocol produces measured quantum states that satisfy the following form:

（2）

wherein,

，Nthe largest spatial dimension of the high-dimensional QKD quantum states,

is represented in a subspace

In the first degree of freedommGroups are unbiased with respect to each other (MUBs),

of high-dimensional QKDkThe groups are unbiased from each other, and satisfy:

（3）

（4）

wherein,

and a is not equal to b,

、

is that

The two orthogonal basis vectors of (a) are,

、

are respectively

And

one of the orthogonal basis vectors in (a),

which represents the inner product of the two basis vectors,N ₁ to represent

The dimension of the degree of freedom. The high-dimensional QKD protocol may employ two or more sets of MUBs to implement the protocol.

According to an embodiment of the present invention, in case it is determined that N is equal to M and that the N coding degrees of freedom and the M decoding degrees of freedom are the same, the N coding degrees of freedom are taken as F target degrees of freedom.

Specifically, in the case of N = M, the encoding process of the transmitting side is described by taking N encoding degrees of freedom as an example; the decoding process of the receiver will be described by taking N decoding degrees of freedom as an example.

Fig. 2 shows a schematic encoding flow according to an embodiment of the present invention.

In the process of quantum communication between the sender and the receiver, the sender modulates the initialization photons by using N coding degrees of freedom to obtain quantum state signals. Specifically, for the initial state photons to be coded, the coding freedom F is utilized in sequence ₁ 、F ₂ 823060 \ 8230and coding freedom F _n And modulating the initialized photons to obtain a coded photon state.

As shown in FIG. 2, the input initiating photon is

The output coded photon state to be transmitted is

. The process of preparing the quantum state signal for communication includes operations S201 to S203.

Operation S201: based on the degree of freedom F of the coding ₁ And (6) coding is carried out. In particular, with a first independent coding module, based on the coding degree of freedom F ₁ For input of

And (6) coding is carried out. The encoded photon states are then sent to a second independent encoding module.

Operation S202: based on the degree of freedom F of the coding ₂ And (6) coding is carried out. In particular, with a second independent coding module, based on the coding degree of freedom F ₂ And coding the photon state output by the first independent coding module. The encoded photon states are then sent to a third independent encoding module.

Operation S203: based on the degree of freedom F of the coding _n And (6) coding is carried out. Specifically, with the Nth independent encoding module, based on the encoding degree of freedom F _n The photon state output by the (N-1) th independent coding module is coded to obtain the final to-be-sent photon state

。

The process that the sender utilizes N coding degrees of freedom to modulate satisfies the following conditions:

（5）

wherein,

representing the quantum state after modulation with N coding degrees of freedom,

representing the state of the photon before encoding,

for coding degrees of freedom F _n Is expressed in the coding degree of freedom F _n And performing unitary operation inside.

Indicating sequential use of coding degrees of freedom F ₁ And a degree of freedom F of coding ₂ And a coding degree of freedom F _n For is to

And (6) coding is carried out.

As shown in FIG. 3, the receiving party receives a quantum state signal of

And detecting the decoded photons by using a detector after decoding. The specific decoding process includes operations S301 to S303.

Operation S301: based on the decoding degree of freedom F _n And decoding is carried out. Specifically, with the Nth independent decoding module, based on the decoding degree of freedom F _n For input

And (6) decoding is carried out. The decoded photon state is then sent to the N-1 th independent decodeAnd (5) modules.

Operation S302: based on the decoding degree of freedom F _n-1 And decoding is carried out. Specifically, with the N-1 st independent decoding module, based on the decoding degree of freedom F _n-1 And decoding the photon state output by the Nth independent decoding module. The decoded photon state is then sent to the N-2 independent decoding module.

Operation S303: based on the decoding degree of freedom F ₁ And decoding is carried out. Specifically, with the 1 st independent decoding module, based on the decoding degree of freedom F ₁ And decoding the photon state output by the 2 nd independent decoding module, and then detecting the single photon by using a detector after decoding.

Wherein the receiver may perform decoding and detection of the quantum state signals using means including, but not limited to, inverse transformation.

According to the embodiment of the invention, the sequence of the N coding degrees of freedom can be changed when the transmitting side performs modulation by using the N coding degrees of freedom. Accordingly, the receiving side performs decoding in the order opposite to the N encoding degrees of freedom in the process of performing decoding using the N decoding degrees of freedom.

As shown in fig. 4, communication between node a and node B is exemplified by N =4. Node a and node B are both N-dimensional QKD systems. The node A is used as a sender in quantum communication, and the node B is used as a receiver in quantum communication.

The nodes A can respectively utilize the coding freedom F ₁ 、F ₂ 、F ₃ And F ₄ And modulating the photons to be transmitted to obtain the modulated quantum state signals. Wherein, and the degree of freedom F of coding ₁ 、F ₂ 、F ₃ And F ₄ The first independent coding module, the second independent coding module, the third independent coding module and the fourth independent coding module which correspond to each other are connected in cascade.

Node B uses the decoding degree of freedom F respectively ₄ 、F ₃ 、F ₂ And F ₁ The received quantum state signals are decoded and detected. Wherein, and decodingDegree of freedom F ₄ 、F ₃ 、F ₂ And F ₁ The fourth independent decoding module, the third independent decoding module, the second independent decoding module and the first independent decoding module which are respectively corresponding are cascaded and connected.

And the node A and the node B adopt an N-dimensional QKD protocol to carry out high-dimensional communication so as to obtain the maximum safe communication bandwidth and the anti-noise capability.

According to an embodiment of the present invention, in a case where it is determined that N is greater than M and that M encoding degrees of freedom identical to M decoding degrees of freedom exist among the N encoding degrees of freedom, the M encoding degrees of freedom are taken as F target degrees of freedom. The transmitting side encodes the photons to be transmitted by using the F target degrees of freedom to obtain modulated quantum state signals, and the receiving side decodes and detects the received quantum state signals by using the F target degrees of freedom.

And the sender utilizes M coding degrees of freedom to code the photons to be sent to obtain the modulated quantum state signals. And the receiving party decodes and detects the received quantum state signals by using the M decoding degrees of freedom.

According to the embodiment of the invention, the process of encoding by using M encoding degrees of freedom by a sender comprises the following steps: determining M independent coding modules corresponding to the M coding degrees of freedom from the N independent coding modules; (N-M) independent encoding modules other than the M independent encoding modules are turned off from the N independent encoding modules; and completing the coding of the photons to be transmitted under M coding degrees of freedom by utilizing M independent coding modules to obtain modulated quantum state signals.

In the case where N > M, the quantum communication may be of a high-dimensional node with another smaller-dimensional space node.

For example, quantum communication between node a and node C, and quantum communication between node a and node G are taken as examples, where node a serves as a sender and node C and node G serve as receivers. Node a acts as a high dimensional node with respect to receiver node C and node G.

For quantum communication between node a and node G: node A is an N-dimensional QKD system and node G is an M-dimensional QKD system. As shown in fig. 4, taking N =4 and M =2 as examples, two sets of MUBs are used to execute the protocol, for example

And

。

node A includes a respective and encoding degree of freedom F ₁ 、F ₂ 、F ₃ And F ₄ The node G comprises respective degrees of freedom F corresponding to the independent coding modules ₁ And F ₂ And a corresponding independent coding module.

Determining that there is the same degree of freedom F of encoding between node A and node G ₁ And F ₂ In case of node A as sender, the degree of freedom F of node A is closed and coded ₃ And F ₄ Corresponding independent coding modules, using in turn the coding degrees of freedom F ₁ And F ₂ And coding the photons to be transmitted to obtain the modulated quantum state signals. As a receiving side, the node G can utilize the decoding freedom F by means of inverse transformation ₁ And F ₂ The received quantum state signals are decoded and detected.

The node A and the node G carry out high-dimensional quantum communication through an M-dimensional QKD protocol, and the following requirements are met:

（6）

（7）

wherein,

and

two sets of mutually unbiased bases representing quantum communication between node a and node G,

and

respectively with a degree of freedom F ₃ And F ₄ The corresponding identity matrix.

For quantum communication between node a and node C: node A is an N-dimensional QKD system and node C is a Q-dimensional QKD system. As shown in fig. 4, taking N =4 and Q =3, two sets of MUBs are used to execute the protocol, for example

And

。

node A includes a respective and encoding degree of freedom F ₁ 、F ₂ 、F ₃ And F ₄ The node G comprises respective degrees of freedom F corresponding to the independent coding modules ₁ 、F ₃ And F ₄ And a corresponding independent coding module. Determining that there is the same degree of freedom F of encoding between node A and node C ₁ 、F ₃ And F ₄ In case of node A as sender, the degree of freedom F of node A is closed and coded ₄ Corresponding independent coding modules, using in turn the coding degrees of freedom F ₁ 、F ₃ And F ₄ And coding the photons to be transmitted to obtain modulated quantum state signals. As a receiving side, the node C can utilize the decoding degree of freedom F in an inverse transformation mode ₁ 、F ₃ And F ₄ The received quantum state signals are decoded and detected.

And the node A and the node C carry out high-dimensional quantum communication through a Q-dimensional QKD protocol.

（8）

（9）

Wherein,

and

respectively representing two mutually unbiased bases of quantum communication between node a and node C,

is a degree of freedom F ₂ The corresponding identity matrix.

According to the embodiment of the invention, under the condition that N is more than M and the N coding degrees of freedom do not have the same degree of freedom as M decoding degrees of freedom, the target relay node is determined, the target relay node is respectively connected with the sending party and the receiving party, P modulation degrees of freedom are the same in the target relay node and the sending party, and Q modulation degrees of freedom are the same in the target relay node and the receiving party.

Specifically, the process of determining the target relay node may be: and under the condition that the sender and the receiver do not have the same degree of freedom, acquiring the degree of freedom information of other nodes from a preset storage address. Then, a relay node which can communicate with the sender through P degrees of freedom and communicate with the receiver through Q nodes is determined from the plurality of nodes, and the relay node is determined as a target relay node.

After the target relay node is determined, the sender and the receiver are controlled to realize quantum key distribution based on a quantum communication protocol through the target relay node, P is larger than or equal to 1, Q is larger than or equal to 1, and the modulation dimension of each modulation degree of freedom is larger than or equal to 2. In the process of quantum key distribution, a sender utilizes P modulation degrees of freedom to encode photons to be sent, and a receiver utilizes Q modulation degrees of freedom to decode and detect quantum state signals.

Specifically, as shown in fig. 4, the communication between the node E and the node J is taken as an example. The degree of freedom that the node E can modulate is F ₁ And F ₃ Can use the degree of freedom F ₁ And F ₃ Encoding and decoding; the degree of freedom that the node J can modulate is F ₂ Can use the degree of freedom F ₂ Encoding and decoding are performed. The same modulation freedom degree does not exist between the node E and the node J, the nodes belong to different coding systems, and quantum communication cannot be directly carried out.

For node G, it is advantageousUsing degree of freedom F ₁ And F ₂ Encoding and decoding are performed. Therefore, the node G can be regarded as a target relay node.

After the node G is determined as the target relay node, quantum communication is first performed between the node E and the node G, and between the node J and the node G, respectively. Specifically, the quantum communication process between the node E and the node G satisfies: node E closes the pair degree of freedom F ₂ And F ₄ Independent coding or decoding modules for modulation, node G closing the pair degree of freedom F ₂ An independent encoding module or an independent decoding module for modulation. Then using the degree of freedom F ₁ Quantum communication between node E and node G is realized, and the two parties share a secure key string L ₁ 。

The quantum communication process between the node J and the node G meets the following conditions: node G closes pair degree of freedom F ₁ An independent encoding module or an independent decoding module for modulation. Then using the degree of freedom F ₂ Quantum communication between the node J and the node G is realized, and the two parties share the secure key string L ₂ . Secure key string L ₁ And a secure key string L ₂ Are equal in length.

According to the embodiment of the invention, the sender and the receiver in the quantum communication process are relative.

According to the embodiment of the invention, in the process of quantum communication between the nodes E and G and between the nodes J and G, the node G can be used as a receiver, and both the nodes E and J can be used as senders, so that the quantum communication between the nodes E and G and between the nodes J and G is completed. In the above situation, the construction cost in the quantum communication process is reduced by taking the target relay node as the receiving party.

According to another embodiment of the invention, in the process of quantum communication between the node E and the node G, the node E is used as a sender, and the node G is used as a receiver. In the process of quantum communication between the node J and the node G, the node G is used as a sender, and the node J is used as a receiver, so that the quantum communication between the node J and the node G is completed.

Between completion node E and node G, nodes J andafter quantum communication process between nodes G, target relay node G publishes a secure key string L ₁ And a secure key string L ₂ And performing exclusive OR operation on the result. The result after the exclusive-or operation satisfies:

。

as a recipient of quantum communication between node E and node J, node J pairs the public result and the secure key string L ₂ And carrying out exclusive OR operation to enable the node E and the node J to share a string of the same security key, thereby realizing quantum communication between the node E and the node J. For public result and security key string L ₂ The process of performing the exclusive or operation satisfies the following conditions:

。

according to an embodiment of the invention, as a sender of quantum communication between node E and node J, node E may pair a public result and a security key string L ₁ And carrying out exclusive OR operation to enable the node E and the node J to share a string of the same security key, thereby realizing quantum communication between the node E and the node J. For public result and security key string L ₁ The process of performing the exclusive or operation satisfies the following conditions:

。

according to an embodiment of the present invention, in the case where there is no same degree of freedom between node E and node J, a high-dimensional node may also be selected as the target relay node.

Specifically, as shown in fig. 4, node a is used as a relay node. In the process of realizing quantum communication between the node A and the node E, the node A is only required to close the pair degree of freedom F ₂ And F ₄ Modulation of (3). In the process of realizing quantum communication between the node A and the node J, the node A is only required to close the pair degree of freedom F ₁ 、F ₃ And F ₄ Modulation of (3). It is not necessary that either node E or node J turn off the modulation for a certain degree of freedom.

According to the embodiment of the invention, under the condition that the same degree of freedom does not exist between the node E and the node J, two or more target relay nodes can be determined to realize quantum communication between the node E and the node J.

As shown in fig. 4, node D, node C, and node B may also be selected as a plurality of target relay nodes between node E and node J. Before quantum communication between the node E and the node J is carried out, communication between the node E and the node D, communication between the node D and the node C, communication between the node C and the node B, and communication between the node B and the node J are carried out, so that a string of same security keys is shared between the node E and the node J.

When a plurality of target relay nodes are used for quantum communication between nodes E and J of different coding systems, the situation that the nodes E and J cannot communicate due to the fact that the target relay nodes G have problems can be avoided, the quantum communication scene compatible with the multiple coding systems is expanded, and the usability of the quantum communication network provided by the invention is enhanced.

According to the embodiment of the invention, under the condition that K receivers exist and T modulation degrees of freedom identical to those of the sender exist in the K receivers, the sender utilizes the T modulation degrees of freedom to encode photons to be sent to obtain modulated quantum state signals and sends the quantum state signals to the K receivers in a broadcasting mode, wherein K is more than or equal to 2, and T is more than or equal to 1; and the K receivers decode and detect the received quantum state signals by utilizing the T modulation degrees of freedom.

When quantum communication between a high-dimensional node and a plurality of spatial nodes with the same or less dimensions is realized, the high-dimensional node as a sender can communicate with a plurality of receivers in a quantum broadcast mode.

As shown in FIG. 4, taking the communication between node A and node B as an example, node A is an N-dimensional node and utilizes a degree of freedom F ₁ 、F ₂ 、F ₃ And F ₄ Encoding and decoding; the node B comprises B ₁ And B ₂ Two QKD systems, and B ₁ And B ₂ All utilize degree of freedom F ₁ 、F ₂ 、F ₃ And F ₄ Encoding and decoding are performed. Node A as the sender, B ₁ And B ₂ As two receivers, sender and receiverThere are 4 identical degrees of modulation freedom F between the parties ₁ 、F ₂ 、F ₃ And F ₄ I.e. T =4.

Node A as the sender, using the coding degree of freedom F ₁ 、F ₂ 、F ₃ And F ₄ Coding the photon state to be transmitted to obtain a modulated quantum state signal, and then transmitting the modulated quantum state signal to a receiver B in a quantum broadcasting mode ₁ And B ₂ 。B ₁ And B ₂ After receiving the quantum state signal, using the decoding degree of freedom F ₁ 、F ₂ 、F ₃ And F ₄ The received quantum state signals are decoded and detected. The sender and the receivers realize quantum communication through an N-dimensional QKD protocol.

As shown in FIG. 4, taking the communication between node A as a high-dimensional node and node C including C as an example ₁ And C ₂ Two QKD systems, and C ₁ And C ₂ Communication with the node a is realized as a Q-dimensional node lower than the node a.

Specifically, before quantum communication is performed, the node A closes the pair degree of freedom F ₂ Modulation of (2) using the coding degree of freedom F ₁ 、F ₃ And F ₄ Coding the photon state to be transmitted to obtain a modulated quantum state signal, and then transmitting the modulated quantum state signal to a receiver C in a quantum broadcasting mode ₁ And C ₂ 。C ₁ And C ₂ After receiving the quantum state signal, using the decoding degree of freedom F ₁ 、F ₃ And F ₄ The received quantum state signals are decoded and detected. The sender and the receivers realize quantum communication through a Q-dimensional QKD protocol.

According to the embodiment of the invention, when T ≧ 2, the Tth in the T modulation degrees of freedom _i The modulation freedom degree is used as the resource multiplexing freedom degree, and the K receivers respectively correspond to the Tth receiver _i K multiplexing channels under the modulation freedom degree are orthogonal to each other; when T is equal to 1 and the adjustable dimensionality of the modulation freedom degree is greater than or equal to K +2, taking K dimensionalities in the modulation freedom degree as resource multiplexing freedom degrees and K receiving dimensionalitiesThe method is characterized in that the method respectively corresponds to K multiplexing channels, and the K multiplexing channels are mutually orthogonal.

As shown in FIG. 4, again with respect to communication between node A and node B, two sets of MUBs may be implemented to implement a protocol, for example

And

. The node B comprises B ₁ And B ₂ Two QKD systems. Node A will have degree of freedom F ₂ As a resource multiplexing degree of freedom, the degree of freedom F ₂ With different orthogonal basis vectors corresponding to the subspaces as multiplexing modes, e.g. when F ₂ The degree of freedom has two orthogonal basis vectors

And

then, then

As node A and node B ₁ The number of multiplexed channels in between,

as node A and node B ₂ The multiplexed channels in between. Other degrees of freedom F ₁ 、F ₃ And F ₄ Still as the coding degree of freedom, do not influence the modulation to the resource multiplexing degree of freedom.

Node A is utilizing degree of freedom F ₁ 、F ₂ 、F ₃ And F ₄ In the process of encoding, for the degree of freedom F ₂ Modulation result of (2)

Satisfies the following conditions:

（10）

the quantum states prepared by node a include:

（11）

（12）

wherein,

and

respectively representing the degrees of freedom F of the node A ₂ Two groups of mutually unbiased bases obtained after modulation as resource multiplexing freedom degrees are obtained, at this time,

is represented by F ₂ Orthogonal basis vector in degrees of freedom.

B ₁ And B ₂ After receiving the quantum state signal from node A, for degree of freedom F ₂ For decoding, the degree of freedom F ₂ Respectively only project to

And

，B ₁ and B ₂ The result after demodulation is:

（13）

（14）

（15）

（16）

wherein,

and

respectively represent a receiver B ₁ For degree of freedom F ₂ Is projected to

And

the result of the demodulation obtained after that is,

and

respectively represent the receiver B ₂ For degree of freedom F ₂ Is projected to

And

the result of the demodulation obtained after that is,

represents the orthogonal basis vector

The orthogonal projection operator of (1).

For example, when quantum communication is performed between node A and node J, node A utilizes the encoding degree of freedom F ₂ Encoding is performed with node J using the degree of freedom F of decoding ₂ And decoding is carried out. Node J includes J ₁ 、J ₂ 、J ₃ And J ₄ A QKD system, all using a degree of freedom F ₂ And decoding is carried out. In a degree of freedom F ₂ Having at least 6 orthogonal basis vectors, the degree of freedom F can only be adjusted ₂ As a resource multiplexing degree of freedom, the nodes A and J are realized ₁ 、J ₂ 、J ₃ 、J ₄ Quantum broadcast communication between.

The invention can realize the quantum communication coding and decoding and the networking compatible with a plurality of coding systems, and can realize mode multiplexing such as wavelength division multiplexing, time division multiplexing, spatial mode multiplexing and the like by carrying out the combined coding and decoding on different degrees of freedom of photons, thereby greatly improving the communication bandwidth and the user scale of a communication network.

The encoding and decoding methods provided by the present invention can be implemented by a free space system or a fiber system.

According to the embodiment of the invention, the network node in the quantum communication network provided by the invention can also be a conventional two-dimensional QKD node, and the method is also suitable for the encoding and decoding method.

According to the embodiment of the invention, for a receiving party in the quantum communication process, the received quantum state signal is decoded through M decoding degrees of freedom, wherein M is more than or equal to 2.

Fig. 5 shows a flow chart of a decoding method of quantum communication according to an embodiment of the invention.

As shown in FIG. 5, the decoding method includes operations S510-S530.

Operation S510 obtains encoding information of a sender to be subjected to quantum communication in a quantum communication network.

Specifically, the encoding information includes N encoding degrees of freedom adopted by the receiver, wherein the sender encodes the photons to be sent through the N encoding degrees of freedom, N is greater than or equal to 2 and N is greater than or equal to M, the sender and the receiver are both network nodes in a quantum communication network, and the modulation dimension of each encoding degree of freedom and each decoding degree of freedom is greater than or equal to 2.

In operation S520, in the case where the same degree of freedom exists between the N encoding degrees of freedom and the M decoding degrees of freedom, the same F target degrees of freedom are determined from the N encoding degrees of freedom and the M decoding degrees of freedom. Wherein F is more than or equal to 1.

In operation S530, the received quantum state signal is decoded and detected by using the F target degrees of freedom, and the quantum state signal is obtained by encoding the photon to be transmitted by the transmitting side by using the F target degrees of freedom.

According to an embodiment of the present invention, the descriptions of operations S510 to S530 refer to operations S110 to S130, which are not repeated herein.

According to an embodiment of the present invention, there is also provided a quantum communication network system compatible with multiple coding schemes, where the quantum communication network includes multiple network nodes, and each of the multiple network nodes is configured to serve as a sender or a receiver in a quantum communication process.

The receiving side includes: a quantum key distribution receiving end; the quantum key distribution receiving end comprises M cascaded independent decoding modules, the M independent decoding modules are used for decoding M different degrees of freedom, quantum state subspaces modulated by the independent decoding modules with the different degrees of freedom are orthogonal to each other, M is more than or equal to 2, and M is less than or equal to N.

As shown in fig. 6, a network node a in the quantum communication network system is taken as an example. The node a may be a sender in quantum communication or a receiver in quantum communication. Node a's structure 600 includes a QKD transmit end 610 and a QKD receive end 620.

QKD transmit end 610 includes N independent encoding modules. Specifically, QKD transmitting end 610 includes a first independent encoding module 610-1, a second independent encoding module 610-2 \8230 \ 8230, and an nth independent encoding module 610-N. Each independent coding module is used for coding and modulating photons in one degree of freedom space.

QKD receiving end 620 includes N independent decoding modules. Specifically, QKD receiving end 620 includes a first independent decoding module 620-1, a second independent decoding module 620-2 \8230 \ 8230, and an nth independent decoding module 620-N. Each independent decoding module is used for coding and modulating photons in one degree of freedom space.

For example, the first independent encoding module may be a polarization controller and the second independent encoding module may be a phase modulator. Correspondingly, the nth independent decoding module may be a polarization controller, and the (N-1) th independent decoding module may be a phase modulator.

According to the embodiment of the invention, the nodes in the quantum communication network can comprise both the QKD transmitting end and the QKD receiving end, or only the QKD transmitting end or the QKD receiving end according to actual needs.

The invention provides a quantum communication coding and decoding method compatible with multiple coding systems and a quantum communication network system, which comprise a high-dimensional quantum state independent coding and decoding method with different degrees of freedom, a compatible quantum communication method among coding and decoding users with different degrees of freedom, and a compatible quantum communication method among users with different coding and decoding systems, and can realize the compatible communication of multiple quantum coding and decoding systems. In addition, the invention realizes high-dimensional quantum state encoding and decoding by utilizing single or multiple degrees of freedom, not only can improve the communication bandwidth of quantum secure communication, but also can greatly improve the tolerance of quantum communication to channel noise and the integral quantum bit error rate of a communication system, thereby enhancing the adaptability of quantum communication in practical application environment.

It will be appreciated by a person skilled in the art that various combinations or combinations of features described in the various embodiments and/or the claims of the invention are possible, even if such combinations or combinations are not explicitly described in the invention. In particular, various combinations and/or combinations of the features recited in the various embodiments and/or claims of the present invention may be made without departing from the spirit or teaching of the invention. All such combinations and/or associations fall within the scope of the present invention.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The quantum communication coding method is applied to a sender in a quantum communication network compatible with a multi-coding system, and the quantum communication network comprises a plurality of network nodes; the encoding method comprises the following steps:

acquiring decoding information of a receiver to be subjected to quantum communication in the quantum communication network, wherein the decoding information comprises M decoding degrees of freedom adopted by the receiver, the receiver decodes a received quantum state signal through the M decoding degrees of freedom, M is more than or equal to 2, both the sender and the receiver are network nodes in the quantum communication network, and the modulation dimension of each decoding degree of freedom is more than or equal to 2;

under the condition that the same freedom degree exists between the N coding freedom degrees and the M decoding freedom degrees of the sender, determining the same F target freedom degrees from the N coding freedom degrees and the M decoding freedom degrees, wherein F is more than or equal to 1,2 is more than or equal to M and less than or equal to N, and the modulation dimension of each coding freedom degree is more than or equal to 2;

the F target degrees of freedom are utilized to encode photons to be sent to obtain a modulated quantum state signal, so that the receiving party can decode and detect the quantum state signal by utilizing the F target degrees of freedom;

2. The method of claim 1, wherein determining the same F target degrees of freedom from the N degrees of encoding freedom and the M degrees of decoding freedom in the presence of the same degrees of freedom between the N degrees of encoding freedom and the M degrees of decoding freedom comprises:

in a case where it is determined that N is equal to M and that the N encoding degrees of freedom and the M decoding degrees of freedom are the same, the N encoding degrees of freedom are taken as the F target degrees of freedom.

3. The method of claim 1, wherein determining the same F target degrees of freedom from the N degrees of encoding freedom and the M degrees of decoding freedom in the presence of the same degrees of freedom between the N degrees of encoding freedom and the M degrees of decoding freedom comprises:

in a case where it is determined that N is greater than M and that there are M encoding degrees of freedom of the N encoding degrees of freedom that are the same as M decoding degrees of freedom, treating the M encoding degrees of freedom as the F target degrees of freedom.

4. The method of claim 1, wherein encoding the photons to be transmitted using the F target degrees of freedom to obtain a modulated quantum state signal comprises:

determining F independent coding modules corresponding to the F target degrees of freedom from the N independent coding modules;

(N-F) independent encoding modules other than the F independent encoding modules are turned off from the N independent encoding modules;

and the F independent coding modules are utilized to complete the coding of the photons to be sent under F degrees of freedom, and modulated quantum state signals are obtained.

5. The method of claim 1, further comprising:

determining a target relay node under the condition that N is greater than M and the N encoding degrees of freedom are not the same as the M decoding degrees of freedom, wherein the target relay node is respectively connected with the sender and the receiver, P modulation degrees of freedom are the same as the sender, and Q modulation degrees of freedom are the same as the receiver;

quantum key distribution based on a quantum communication protocol is realized between the target relay node and the receiver, wherein P is more than or equal to 1, Q is more than or equal to 1, and the modulation dimension of each modulation degree of freedom is more than or equal to 2;

in the process of quantum key distribution, the sender utilizes the P modulation degrees of freedom to encode the photons to be sent, and the receiver utilizes the Q modulation degrees of freedom to decode and detect the quantum state signals.

6. The method of claim 1, further comprising:

in the case where it is determined that there are K receivers and that there are T modulation degrees of freedom in the K receivers that are the same as the sender,

and encoding the photons to be transmitted by utilizing the T modulation degrees of freedom to obtain modulated quantum state signals, and transmitting the quantum state signals to the K receivers in a broadcasting manner, so that the K receivers decode and detect the received quantum state signals by utilizing the T modulation degrees of freedom, wherein K is more than or equal to 2, and T is more than or equal to 1.

7. The method of claim 6, further comprising:

when T is more than or equal to 2, the Tth degree of freedom in the T modulation degrees of freedom is set _i The modulation freedom degree is used as the resource multiplexing freedom degree, wherein the K receivers respectively correspond to the Tth receiver _i K multiplexing channels under the modulation freedom degree, wherein the K multiplexing channels are mutually orthogonal;

and when T is equal to 1 and the adjustable dimension of the modulation degree of freedom is greater than or equal to K +2, taking K dimensions in the modulation degree of freedom as the resource multiplexing degree of freedom, wherein the K receivers respectively correspond to the K multiplexing channels, and the K multiplexing channels are orthogonal to each other.

8. The method of claim 1, wherein the receiver and the sender communicate based on a quantum communication protocol, the quantum communication protocol comprising one of:

the BB84 protocol;

a high-dimensional QKD protocol;

two or more groups of mutually unbiased groups;

the encoding degree of freedom and the decoding degree of freedom include at least one of: polarization, timestamp, phase, spatial mode, and frequency;

wherein the spatial pattern comprises one of:

a multi-path mode of the multi-core fiber;

a multi-path mode of the optical chip;

laguer-gaussian mode; bessel mode.

9. The decoding method of quantum communication is characterized by being applied to a receiving party in a quantum communication network compatible with a multi-coding system, wherein the quantum communication network comprises a plurality of network nodes; the decoding method comprises the following steps:

acquiring coding information of a sender to be subjected to quantum communication in the quantum communication network, wherein the coding information comprises N coding degrees of freedom adopted by a receiver, the sender codes photons to be sent through the N coding degrees of freedom, N is more than or equal to 2, the sender and the receiver are network nodes in the quantum communication network, and the modulation dimension of each coding degree of freedom is more than or equal to 2;

determining the same F target degrees of freedom from the N coding degrees of freedom and the M decoding degrees of freedom under the condition that the same degrees of freedom exist between the N coding degrees of freedom and the M decoding degrees of freedom of the receiving party, wherein F is more than or equal to 1,2 is more than or equal to M and less than or equal to N, and the modulation dimension of each decoding degree of freedom is more than or equal to 2;

decoding and detecting the received quantum state signals by using the F target degrees of freedom, wherein the quantum state signals are obtained by encoding photons to be transmitted by the transmitter by using the F target degrees of freedom;