Quantum state decoding apparatus and method, and software-defined quantum communication system

Abstract

The present disclosure provides a quantum state decoding apparatus and method, and a software-defined quantum communication system. The apparatus comprises: a first optical coupling unit, a time-phase-to-polarization encoding unit, a first transmission optical path, a second optical coupling unit, and a polarization decoding unit. The time-phase-to-polarization encoding unit can convert an optical pulse in a time-phase-encoded quantum state into an optical pulse in a polarization-encoded quantum state. The polarization decoding unit can decode and output the optical pulse in the polarization-encoded quantum state. The first optical coupling unit and the second optical coupling unit can control, on the basis of a quantum communication decoding control instruction, the output of an optical pulse in the polarization-encoded quantum state of any optical output branch. Therefore, the quantum state decoding apparatus in embodiments of the present disclosure can realize that regardless of whether the optical pulse in the time-phase-encoded quantum state or the optical pulse in the polarization-encoded quantum state is input, the quantum state decoding apparatus can output the optical pulse in the polarization-encoded quantum state, and input the optical pulse in the polarization-encoded quantum state to the polarization decoding unit for decoding.

Description

Quantum state decoding device, method and software-defined quantum communication system Technical Field

[0001] This disclosure relates to the fields of quantum communication and optical quantum decoding technology, and in particular to a quantum state decoding device, method, and software-defined quantum communication system. Background Technology

[0002] Quantum communication technology is a cutting-edge and hotly debated field combining quantum physics and information science. Current applications primarily include quantum key distribution and quantum direct communication. Based on the Heisenberg uncertainty principle and the no-cloning theorem in quantum mechanics, quantum key distribution enables two communicating parties to securely share keys in real time, while quantum direct communication ensures secure information transmission from the outset. Quantum communication can detect potential eavesdropping on communication channels and can be applied to fields with high-security information transmission requirements, such as national defense, government affairs, finance, and power.

[0003] The physical implementation of quantum communication systems, such as quantum key distribution and quantum direct communication, requires encoding and decoding of quantum states. Currently, the main encoding methods for quantum communication systems include polarization encoding and time-phase encoding, with corresponding decoding methods of polarization decoding and time-phase decoding. Typically, a receiver in a quantum communication system chooses only one of these decoding methods, thus limiting the system's versatility and flexibility in networking.

[0004] How to achieve universal quantum state decoding that is compatible with decoding methods of multiple quantum communication systems in a single quantum state decoding device is an important issue in quantum communication applications.

[0005] Summary of the Invention

[0006] This disclosure provides a quantum state decoding device, method, and software-defined quantum communication system to solve the technical problems mentioned in the prior art.

[0007] According to a first aspect of this disclosure, a quantum state decoding device is provided, comprising: a first optical coupling unit, a time-phase-to-polarization encoding unit, a first transmission optical path, a second optical coupling unit, and a polarization decoding unit;

[0008] The first optical coupling unit includes one input port and two output ports, namely the first port, the second port and the third port. The first port is the input port of the quantum state decoding device, used to receive one input optical pulse.

[0009] The second optical coupling unit includes two input ports and one output port, namely the fourth port, the fifth port, and the sixth port;

[0010] The time-phase-to-polarization encoding unit includes an input port and an output port, used to perform polarization encoding conversion on the input time-phase encoded quantum state light pulse and output the polarization encoded quantum state light pulse;

[0011] The third port of the first optical coupling unit is connected to the input port of the time phase to polarization encoding unit, and the output port of the time phase to polarization encoding unit is connected to the fifth port of the second optical coupling unit, forming the first optical output branch;

[0012] The second port of the first optical coupling unit is connected to the fourth port of the second optical coupling unit through the first transmission optical path to form a second optical output branch;

[0013] The first optical coupling unit is used to input the input optical pulse into the first optical output branch and / or the second optical output branch according to the quantum communication decoding control command. The quantum communication decoding control command is determined according to the decoding requirements of the quantum communication system.

[0014] The second optical coupling unit is used to output the optical pulse of the polarization-coded quantum state output by the second optical output branch or the first optical output branch according to the quantum communication decoding control command;

[0015] The polarization decoding unit includes an input port and at least one output port. The input port of the polarization decoding unit is connected to the sixth port of the second optical coupling unit and is used to input the light pulse of the polarization-encoded quantum state, decode it, and output it through the at least one output port.

[0016] In some embodiments, the first optical coupling unit is an optical coupler, and the second optical coupling unit is an optical switch.

[0017] In some embodiments, the first optical coupling unit is used to split an input optical pulse input through the first port into two sub-optical pulses, and input the two sub-optical pulses into the first optical output branch and the second optical output branch through the third port and the second port, respectively.

[0018] The second optical coupling unit is used to select and output the optical pulse of the polarization-coded quantum state output by the second optical output branch or the first optical output branch according to the quantum communication decoding control command.

[0019] In some embodiments, the first optical coupling unit is an optical switch, and the second optical coupling unit is an optical switch or an optical coupler.

[0020] In some embodiments, the first optical coupling unit is used to select and output one input optical pulse input from the first port to the first optical output branch or the second optical output branch according to the quantum communication decoding control instruction;

[0021] When the second optical coupling unit is an optical switch, the second optical coupling unit is used to connect the first optical output branch or the second optical output branch according to the quantum communication decoding control command.

[0022] When the second optical coupling unit is an optical coupler, the second optical coupling unit is used to output the optical pulse of the polarization-coded quantum state output by the first optical output branch or the second optical output branch.

[0023] In some embodiments, the time-phase-to-polarization coding unit includes a third optical coupling unit, a fourth optical coupling unit, a second transmission optical path, and a third transmission optical path.

[0024] The third optical coupling unit includes at least three ports: one input port and two output ports; the fourth optical coupling unit includes at least three ports: two input ports and one output port; the two output ports of the third optical coupling unit are connected to the two input ports of the fourth optical coupling unit through the second transmission optical path and the third transmission optical path; the input port of the third optical coupling unit is the input port of the time-phase-to-polarization encoding unit, and the output port of the fourth optical coupling unit is the output port of the time-phase-to-polarization encoding unit; the optical path lengths of the second transmission optical path and the third transmission optical path are not equal.

[0025] In some embodiments, the third optical coupling unit and the fourth optical coupling unit are the same optical coupler, and the time phase-to-polarization encoding unit further includes two mirrors.

[0026] The two output ports of the optical coupler are respectively connected to one end of the second transmission optical path and one end of the third transmission optical path, and the two reflectors are respectively connected to the other end of the second transmission optical path and the other end of the third transmission optical path.

[0027] In some embodiments, one of the two reflectors is a 90° polarization state rotating reflector.

[0028] In some embodiments, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter, and the time-phase-to-polarization encoding unit further includes two mirrors.

[0029] The two output ports of the polarization beam splitter are respectively connected to one end of the second transmission optical path and one end of the third transmission optical path, and the two reflectors are respectively connected to the other end of the second transmission optical path and the other end of the third transmission optical path.

[0030] In some embodiments, the two reflectors are 90° polarization state rotating reflectors.

[0031] In some embodiments, the third optical coupling unit is an optical coupler, and the fourth optical coupling unit is an optical coupler or a polarization combiner.

[0032] In some embodiments, the second or third transmission optical path is a 90° twisted polarization-maintaining fiber; or...

[0033] The time-phase-to-polarization encoding unit further includes a 90° polarization state rotator, which is disposed in the second transmission optical path or the third transmission optical path and is used to rotate the polarization state of the input sub-light pulse by 90°.

[0034] In some embodiments, the third optical coupling unit is a polarization beam splitter, and the fourth optical coupling unit is an optical coupler or a polarization beam combiner.

[0035] In some embodiments, the device further includes: a first polarization controller and / or a second polarization controller.

[0036] The first polarization controller is disposed at the front end of the time phase to polarization encoding unit or at the front end of the first optical coupling unit, and is used to correct the polarization state of the optical pulse input to the time phase to polarization encoding unit;

[0037] The second polarization controller is disposed on the first transmission optical path, at the front end of the first optical coupling unit, or between the second optical coupling unit and the polarization decoding unit, and is used to correct the polarization state of the optical pulse input to the polarization decoding unit.

[0038] In some embodiments, the polarization decoding unit includes: a first optical beamsplitter, a first polarization beamsplitter, and a second polarization beamsplitter.

[0039] The first optical beam splitter includes three ports: one input port and two output ports. The input port of the first optical beam splitter is the input port of the polarization decoding unit, and the two output ports are respectively connected to the first polarization beam splitter and the second polarization beam splitter.

[0040] The first polarization beam splitter includes three ports: one input port and two output ports. The input port of the first polarization beam splitter is connected to one of the two output ports of the first optical beam splitter.

[0041] The second polarization beam splitter has three ports: one input port and two output ports. The input port of the second polarization beam splitter is connected to the other of the two output ports of the first optical beam splitter.

[0042] In some embodiments, the polarization decoding unit further includes: a second optical beamsplitter and a third polarization beamsplitter.

[0043] The second optical beam splitter includes three ports: one input port and two output ports. The input port of the second optical beam splitter is the input port of the polarization decoding unit. One of the two output ports of the second optical beam splitter is connected to the input port of the first optical beam splitter, and the other of the two output ports is connected to the third polarization beam splitter.

[0044] The third polarization beam splitter includes three ports: one input port and two output ports. The input port of the third polarization beam splitter is connected to the other of the two output ports of the second optical beam splitter.

[0045] In some embodiments, the second optical beam splitter is a 1:2 optical beam splitter.

[0046] In some embodiments, the polarization decoding unit further includes a quarter-wave plate and a half-wave plate.

[0047] The quarter-wave plate is disposed at the front end of any polarization beam splitter;

[0048] The half-wave plate is positioned in front of any of the polarization beamsplitters, but is not positioned in front of the same polarization beamsplitter as the quarter-wave plate.

[0049] In some embodiments, the polarization decoding unit further includes:

[0050] A quarter-wave plate is placed at the front end of any polarization beam splitter.

[0051] In some embodiments, the polarization decoding unit further includes:

[0052] A half-wave plate is placed at the front end of any polarization beam splitter.

[0053] According to a second aspect of this disclosure, a quantum state decoding method is provided, which is applied to the above-described quantum state decoding device to realize quantum state decoding.

[0054] According to a third aspect of this disclosure, a software-defined quantum communication system is provided, including the aforementioned quantum state decoding device and decoding control device;

[0055] The decoding control device is used to generate quantum communication decoding control instructions based on the decoding requirements of the quantum communication system, and send them to the quantum state decoding device.

[0056] In summary, the quantum state decoding device, method, and quantum communication system provided in this disclosure have at least the following beneficial effects:

[0057] This disclosure employs a first optical coupling unit, a time-phase to polarization encoding unit, a first transmission optical path, a second optical coupling unit, and a polarization decoding unit to form a quantum state decoding device. The time-phase to polarization encoding unit converts the polarization encoding of light pulses in a time-phase encoded quantum state, generating light pulses in a polarization encoded quantum state. The polarization decoding unit decodes and outputs these light pulses. The first and second optical coupling units can control the output of light pulses in polarization encoded quantum states from any optical output branch according to quantum communication decoding control commands. Therefore, the quantum state decoding device described in this disclosure can output light pulses in polarization encoded quantum states regardless of whether the input is a time-phase encoded quantum state light pulse or a polarization encoded quantum state light pulse, and input these pulses to the polarization decoding unit for decoding. This disclosure enables the same quantum state decoding device to meet the decoding requirements of both time-phase encoded and polarization encoded quantum states. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 is a structural block diagram of a quantum state decoding device provided in an embodiment of this disclosure;

[0060] Figure 2 is a first embodiment architecture diagram of a quantum state decoding device provided by the present disclosure;

[0061] Figure 3 is a second embodiment architecture diagram of a quantum state decoding device provided by the present disclosure;

[0062] Figure 4 is a third embodiment architecture diagram of a quantum state decoding device provided by the present disclosure;

[0063] Figure 5 is a structural diagram of a first embodiment of the time phase-to-polarization coding unit provided in this disclosure;

[0064] Figure 6 is a structural diagram of a second embodiment of the time phase-to-polarization coding unit provided in the present disclosure;

[0065] Figure 7 is a structural diagram of a third embodiment of the time phase-to-polarization encoding unit provided in this disclosure;

[0066] Figure 8 is a structural diagram of a fourth embodiment of the time phase-to-polarization coding unit provided in this disclosure;

[0067] Figure 9 is a structural diagram of a fifth embodiment of the time phase-to-polarization coding unit provided in this disclosure;

[0068] Figure 10 is a structural diagram of a sixth embodiment of the time phase-to-polarization coding unit provided in this disclosure;

[0069] Figure 11 is a structural diagram of a seventh embodiment of the time phase-to-polarization coding unit provided in this disclosure;

[0070] Figure 12 is a structural diagram of a first embodiment of the polarization decoding unit provided in this disclosure;

[0071] Figure 13 is a structural diagram of a second embodiment of the polarization decoding unit provided in the present disclosure;

[0072] Figure 14 is a schematic diagram of the structure of a software-defined quantum communication system provided in an embodiment of this disclosure. Detailed Implementation

[0073] To make the above and other features and advantages of this disclosure clearer, the disclosure is further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explanation to those skilled in the art and are exemplary only, not restrictive.

[0074] In the following description, numerous specific details are set forth to provide a thorough understanding of this disclosure. However, it will be apparent to those skilled in the art that the specific details are not required to practice this disclosure. In other instances, well-known steps or operations have not been described in detail to avoid obscuring this disclosure.

[0075] Referring to Figures 1 and 2, this disclosure provides a quantum state decoding device. Figure 1 shows a block diagram of the device structure. The device includes: a first optical coupling unit 100, a time-phase-to-polarization encoding unit 200, a first transmission optical path 300, a second optical coupling unit 400, and a polarization decoding unit 500.

[0076] In some embodiments, the time-phase-to-polarization encoding unit 200 includes an input port and an output port, used to perform polarization encoding conversion on the input time-phase-encoded quantum state optical pulse and output a polarization-encoded quantum state optical pulse. The input time-phase-encoded quantum state optical pulse may contain two time slots, being two time-domain separated sub-pulses; or the input time-phase-encoded quantum state optical pulse may contain only one time slot, being one of two time-domain separated sub-pulses (the preceding or following sub-pulse). The polarization states of the two sub-pulses may be the same or orthogonal.

[0077] It should be noted that the time phase encoding in the embodiments of this disclosure includes phase encoding, that is, the time phase encoding is an encoding composed of any combination of quantum states of the X phase basis, Y phase basis, and Z time basis; the time phase decoding includes phase decoding, that is, the time phase decoding is decoding the encoded quantum state composed of any combination of quantum states of the X phase basis, Y phase basis, and Z time basis.

[0078] Referring to Figure 2, which is an architectural diagram of the first embodiment of the quantum state decoding device provided in this disclosure, the first optical coupling unit 100 includes an input port and two output ports, namely a first port A, a second port B and a third port C. The first port A is the input port of the quantum state decoding device, used to receive one input optical pulse.

[0079] The second optical coupling unit 400 includes two input ports and one output port, namely the fourth port B', the fifth port C', and the sixth port A'.

[0080] In this configuration, the third port C of the first optical coupling unit 100 is connected to the input port of the time phase to polarization encoding unit 200, and the output port of the time phase to polarization encoding unit 200 is connected to the fifth port C' of the second optical coupling unit 400, forming a first optical output branch; the second port B of the first optical coupling unit 100 is connected to the fourth port B' of the second optical coupling unit 400 through the first transmission optical path 300, forming a second optical output branch.

[0081] The first optical coupling unit 100 is used to input one input optical pulse into the first optical output branch and / or the second optical output branch according to the quantum communication decoding control command, and the sixth port A' of the second optical coupling unit 400 is the output port of the second optical coupling unit 400.

[0082] In this embodiment of the present disclosure, the second optical coupling unit 400 is used to output the optical pulse of the polarization-coded quantum state output by the second optical output branch or the first optical output branch according to the quantum communication decoding control command.

[0083] The polarization decoding unit 500 includes an input port and at least one output port. The input port of the polarization decoding unit 500 is connected to the sixth port A' of the second optical coupling unit 400, and is used to input a light pulse of polarization-coded quantum state, decode it, and output it through at least one output port. The light pulse input to the first coupling unit 100 of this disclosure can be a light pulse of time-phase-coded quantum state or a light pulse of polarization-coded quantum state.

[0084] It should be noted that the quantum communication decoding control command can be determined according to the decoding requirements of the quantum communication system. The quantum communication decoding control command can be issued by programmable control software. For example, when both the first optical coupling unit 100 and the second optical coupling unit 400 are optical switches, the control software runs through the host computer (control circuit unit or processor unit) in the quantum communication system to issue quantum communication decoding control commands to configure the selection state of the optical switches, regardless of whether the input is a time-phase encoded quantum state or a polarization-encoded quantum state, the output of the optical pulse of the polarization-encoded quantum state can be achieved.

[0085] In the above embodiments, a quantum state decoding device is composed of a first optical coupling unit 100, a time-phase to polarization encoding unit 200, a first transmission optical path 300, a second optical coupling unit 400, and a polarization decoding unit 500. The time-phase to polarization encoding unit 200 can convert the polarization encoding of time-phase encoded quantum state light pulses and generate polarization encoded quantum state light pulses. The polarization decoding unit 500 can decode and output the polarization encoded quantum state light pulses. The first optical coupling unit 100 and the second optical coupling unit 400 can control the output of polarization encoded quantum state light pulses from any optical output branch according to quantum communication decoding control commands. Therefore, the quantum state decoding device described in this disclosure can output polarization encoded quantum state light pulses regardless of whether the input is a time-phase encoded quantum state light pulse or a polarization encoded quantum state light pulse, and input them to the polarization decoding unit for decoding. This disclosure enables the same quantum state decoding device to meet the decoding requirements of both time-phase encoded and polarization encoded quantum states.

[0086] In one embodiment, the first optical coupling unit 100 is an optical coupler, and the second optical coupling unit 400 is an optical switch. The optical coupler can be a free-space crystal coupler or a fiber optic coupler, used to split optical pulses. The optical switch can select and output a polarization-coded quantum state optical pulse from one optical output branch by connecting or disconnecting it.

[0087] When the first optical coupling unit 100 is an optical coupler, the first optical coupling unit 100 is used to split one input optical pulse into two sub-optical pulses through the first port A, and input the two sub-optical pulses into the first optical output branch and the second optical output branch through the third port C and the second port B respectively.

[0088] In this embodiment, the second optical coupling unit 400 is used to select, according to the quantum communication decoding control command, to output either a light pulse of a polarization-coded quantum state from the second optical output branch or a light pulse of a polarization-coded quantum state from the first optical output branch. In this embodiment, the second optical coupling unit 400 is an optical switch, capable of flexibly switching between the second and first optical output branches according to the quantum communication decoding control command, thereby selecting to output either a light pulse of a polarization-coded quantum state from the second optical output branch or a light pulse of a polarization-coded quantum state from the first optical output branch.

[0089] The purpose of this embodiment is to output a light pulse with a polarization-coded quantum state through the second optical coupling unit 400, regardless of whether the input is a light pulse with a time-phase encoded quantum state or a light pulse with a polarization-coded quantum state, and to decode it through the polarization decoding unit. Therefore, in the above embodiment, if the input is a light pulse with a time-phase encoded quantum state, the first optical coupling unit 100 can split the light pulse into two paths, which are respectively sent to the first optical output branch and the second optical output branch. In the first optical output branch, the time-phase to polarization encoding unit 200 converts the light pulse with a time-phase encoded quantum state into a light pulse with a polarization-coded quantum state before inputting it into the second optical coupling unit 400. The light pulse output in the second optical output branch is a light pulse with a time-phase encoded quantum state. Through the selection function of the second optical coupling unit 400, the light pulse with a polarization-coded quantum state is selected to be connected to the first optical output branch and input into the polarization decoding unit 500 for decoding, thereby realizing the effective decoding output of the target light pulse and improving the flexibility and adaptability of the quantum communication system.

[0090] If the input is a light pulse of polarization-coded quantum state, then the light pulse of the target output coded quantum state transmitted in the second optical output branch is the light pulse of the target output. The second optical coupling unit 400 can then choose to connect to the second optical output branch to output the light pulse of polarization-coded quantum state and input it into the polarization decoding unit 500 for decoding.

[0091] In another embodiment, the first optical coupling unit 100 is an optical switch, and the second optical coupling unit 400 is an optical coupler. In this embodiment, the first optical coupling unit 100 can freely switch its connection port based on quantum communication decoding control commands, thereby connecting with either the first optical output branch or the second optical output branch.

[0092] Specifically, if the input to the first optical coupling unit 100 is a time-phase encoded quantum state optical pulse, then the first optical coupling unit 100 connects to the first optical output branch through the third port C based on the quantum communication decoding control command. The first optical coupling unit 100 inputs the time-phase encoded quantum state optical pulse to the first optical output branch through the third port C. At this time, the first optical output branch inputs the time-phase encoded quantum state optical pulse output by the first optical coupling unit 100, and outputs a polarization encoded quantum state optical pulse converted by the time-phase to polarization encoding unit 200. The input and output of the second optical output branch are both empty. The second optical coupling unit 400 couples the outputs of the two optical output branches, and the coupling amount of the output is the polarization encoded quantum state optical pulse of the first optical output branch.

[0093] When the input to the first optical coupling unit 100 is a light pulse of a polarization-coded quantum state, and the first optical coupling unit 100 connects to the second optical output branch through the second port B based on the quantum communication decoding control command, the first optical coupling unit 100 inputs the light pulse of the polarization-coded quantum state to the second optical output branch through the second port B. At this time, the second optical output branch receives the light pulse of the polarization-coded quantum state input by the first optical coupling unit 100 and outputs it; both the input and output of the first optical output branch are empty. The second optical coupling unit 400 couples the outputs of the two optical output branches, and the coupling amount of the output is the light pulse of the polarization-coded quantum state of the second optical output branch.

[0094] In another embodiment, the first optical coupling unit 100 is an optical switch, and the second optical coupling unit 400 is an optical switch.

[0095] When the first optical coupling unit 100 functions as an optical switch, it can selectively input optical pulses to the corresponding first or second optical output branch according to quantum communication decoding control commands. The second optical coupling unit 400 functions as an optical switch, which can connect the first or second optical output branch according to quantum communication decoding control commands, and output optical pulses with polarization-coded quantum states.

[0096] It should be noted that, generally, the optical output branch selected for connection by the second optical coupling unit 400 is the same as the optical output branch selected for connection by the first optical coupling unit 100. For example, the first optical coupling unit 100 and the second optical coupling unit 400 select the same optical output branch based on quantum communication decoding control commands; that is, the first optical coupling unit 100 selects the first optical output branch based on quantum communication decoding control commands, and the second optical coupling unit 400 also selects the first optical output branch based on quantum communication decoding control commands. In this way, polarization-coded quantum states can be output, enabling precise output of the required optical pulses, thus improving the accuracy, flexibility, and adaptability of the quantum communication system.

[0097] In one embodiment of this disclosure, referring to Figure 3, which shows the architecture of a second embodiment of the quantum state decoding device, the time phase-to-polarization encoding unit 200 includes a third optical coupling unit 31, a fourth optical coupling unit 32, a second transmission optical path 33, and a third transmission optical path 34. The third optical coupling unit 31 includes at least three ports: one input port and two output ports, i.e., one input port D and two output ports E and F. The fourth optical coupling unit 32 may include at least three ports: two input ports and at least one output port, i.e., two input ports E' and F', and one output port D'. The output port F of the third optical coupling unit 31 is connected to the input port F' of the fourth optical coupling unit 32 via the second transmission optical path 33, and the output port E of the third optical coupling unit 31 is connected to the input port E' of the fourth optical coupling unit 32 via the third transmission optical path 34. In this embodiment, the input port D of the third optical coupling unit 31 is the input port of the time-phase-to-polarization encoding unit 200, and it is connected to the third port C of the first optical coupling unit 100. The output port D' of the fourth optical coupling unit 32 is the output port of the time-phase-to-polarization encoding unit 200, and it is connected to the fifth port C' of the second optical coupling unit 400. The optical paths of the second transmission optical path 33 and the third transmission optical path 34 are not equal. In the above embodiment, the third optical coupling unit 31 is used to split the input optical pulse into two sub-optical pulses, namely the first sub-optical pulse and the second sub-optical pulse. The first and second optical pulses are transmitted along the second transmission optical path 33 and the third transmission optical path 34, respectively, and are combined and output by the fourth optical coupling unit 32.

[0098] Referring to Figure 4, which is a schematic diagram of the third embodiment of the quantum state decoding device of this disclosure, in this embodiment, the third optical coupling unit 31 and the fourth optical coupling unit 32 included in the time phase to polarization encoding unit 200 are the same optical coupling unit 41. The time phase to polarization encoding unit 200 also includes a second transmission optical path 42, a third transmission optical path 43, and two reflectors 44 and 45.

[0099] The optical coupling unit 41 includes four ports, namely port D, port E, port F and port D'. Port D is the input port, which is connected to the third port C of the first optical coupling unit 100. Port D' is the output port, which is connected to the fifth port C' of the second optical coupling unit 400. Ports F and E are connected to two reflectors 44 and 45 through the second transmission optical path 42 and the third transmission optical path 43, respectively. Reflectors 44 and 45 are used to reflect the input sub-light pulses back to the optical coupling unit 41.

[0100] Figure 5 shows a structural diagram of the first embodiment of the time-phase-to-polarization encoding unit 200. In this embodiment, the third optical coupling unit 31 and the fourth optical coupling unit 32 are the same optical coupling unit, which is an optical coupler. The second transmission optical path 33 and the third transmission optical path 34 are two different transmission optical paths. The time-phase-to-polarization encoding unit 200 includes an optical coupler 51 (i.e., the third optical coupling unit 31 and the fourth optical coupling unit 32), a second transmission optical path 52 and a third transmission optical path 53, a reflector 54, and a reflector 55. One output port F of the optical coupler 51 is connected to one end of the second transmission optical path 52, and another output port E of the optical coupler 51 is connected to one end of the third transmission optical path 53. The reflector 54 is connected to the other end of the second transmission optical path 52, and the reflector 55 is connected to the other end of the third transmission optical path 53. The reflectors 54 and 55 are used to reflect the input sub-light pulses back to the optical coupler 51. Optionally, one of the reflectors 54 and 55 is a 90° polarization state rotating reflector.

[0101] In this embodiment, the optical coupler 51 may include at least three ports, including at least one input port and two output ports, namely port D, port E, and port F. Ports F and E are connected to two reflectors via a second transmission optical path 52 and a third transmission optical path 53, respectively. Port D serves as the input port for receiving input optical pulses. Port E is connected to reflector 55 via the third transmission optical path 53, and port F is connected to reflector 54 via the second transmission optical path 52. When the optical coupler 51 includes three ports, the input port D can also serve as the output port of the time-phase-to-polarization encoding unit 200 for outputting optical pulses of polarization-encoded quantum states. When the optical coupler 51 includes four ports, it may also include one output port, such as port D' in FIG. 5, which serves as the output port of the time-phase-to-polarization encoding unit 200 for outputting optical pulses of polarization-encoded quantum states.

[0102] Referring to Figure 6, a structural diagram of a second embodiment of the time-phase-to-polarization encoding unit 200 of this disclosure is shown. In this embodiment, the third optical coupling unit 31 and the fourth optical coupling unit 32 are the same optical coupling unit, which is a polarization beam splitter. The second transmission optical path 33 and the third transmission optical path 34 are two different transmission optical paths. As shown in Figure 6, the time-phase-to-polarization encoding unit 200 of this embodiment includes a polarization beam splitter 61 (i.e., the third optical coupling unit 31 and the fourth optical coupling unit 32), a second transmission optical path 62 and a third transmission optical path 63, a reflector 64, and a reflector 65. The output port F of the polarization beam splitter 61 is connected to one end of the second transmission optical path 62, the output port E of the polarization beam splitter 61 is connected to one end of the third transmission optical path 63, the reflector 64 is connected to the other end of the second transmission optical path 62, and the reflector 65 is connected to the other end of the third transmission optical path 63. The reflectors 64 and 65 are used to reflect the input sub-light pulses back to the polarization beam splitter 61.

[0103] The polarization beam splitter 61 may include at least three ports, namely port D, port E, and port F. Port F and port E are connected to two reflectors via a second transmission optical path 62 and a third transmission optical path 63, respectively. Port D serves as an input port for receiving input optical pulses. Port E is connected to reflector 65 via the third transmission optical path 63, and port F is connected to reflector 64 via the second transmission optical path 62. When the polarization beam splitter 61 includes three ports, as shown in Figure 6, the input port D can also serve as the output port of the time-phase-to-polarization coding unit 200, used to output light pulses of polarization-coded quantum states. In this case, the time-phase-to-polarization coding unit 200 also includes an optical circulator (not shown in the figure). The optical circulator is disposed at the front end of port D and includes three ports, namely a first port, a second port, and a third port. The first port of the optical circulator is the input port of the time-phase-to-polarization coding unit 200, and the third port of the optical circulator is the output port of the time-phase-to-polarization coding unit 200. The second port of the optical circulator is connected to port D. The light pulse input from the first port of the optical circulator is output through the second port of the optical circulator, and the light pulse input from the second port of the optical circulator is output through the third port of the optical circulator.

[0104] When the polarization beam splitter 61 includes four ports, as shown in FIG7, it is a structural diagram of the third embodiment of the time phase to polarization encoding unit 200 of this disclosure. The difference between this embodiment and the second embodiment is that the polarization beam splitter 61 may also include an output port, as shown in port D' in FIG7, which serves as the output port of the time phase to polarization encoding unit 200 for outputting optical pulses of polarization-encoded quantum states.

[0105] It should be noted that when mirrors 64 and 65 do not rotate the polarization state of the input sub-light pulse, polarization beam splitter 61 only outputs the combined polarization-encoded quantum state light pulse from port D. When mirrors 64 and 65 rotate the polarization state of the input sub-light pulse by any angle (other than 0° and 90°), polarization beam splitter 61 can output the combined polarization-encoded quantum state light pulse from port D or port D'. When mirrors 64 and 65 rotate the polarization state of the input sub-light pulse by 90°, the combined polarization-encoded quantum state light pulse can only be output from port D'.

[0106] In this embodiment, the polarization beam splitter 61 is used to polarize and split a single optical pulse received from the input port into two sub-optical pulses, which are output through port F and port E respectively, and transmitted along the second transmission optical path 62 and the third transmission optical path 63 to two reflectors 64 and 65 respectively, and reflected back to the polarization beam splitter 61 by the two reflectors 64 and 65.

[0107] Reflectors 64 and 65 are polarization state rotating reflectors, capable of rotating the polarization state of the input light pulse by 90°, 45°, or other angles. In an exemplary embodiment, the polarization state rotating reflector is a 90° polarization state rotating reflector, which can be a quarter-wave plate reflector or a 90° Faraday rotating reflector, such that the polarization state of the reflected sub-light pulse is rotated by 90° relative to the sub-light pulse input to the corresponding reflector, so that the polarization states of the two sub-light pulses are orthogonal when reflected back to the optical coupler 61, and are combined and output from port D'.

[0108] Figure 8 shows a structural diagram of a fourth embodiment of the time-phase-to-polarization encoding unit 200 of this disclosure. In this embodiment, the third optical coupling unit 31 is an optical coupler, and the fourth optical coupling unit 32 is a polarization combiner. The time-phase-to-polarization encoding unit 200 includes an optical coupler 81, a second transmission optical path 82, a third transmission optical path 83, and a polarization combiner 84. The optical paths of the second transmission optical path 82 and the third transmission optical path 83 are not equal.

[0109] Based on this structure, in one embodiment, the polarization states of the two time-slot sub-light pulses input to the time-phase-to-polarization coding unit 200 are orthogonal to each other, and the polarization states of the two time-slot sub-light pulses are the intrinsic polarization states of the polarization combiner 84; or the polarization states of the two time-slot sub-light pulses input to the time-phase-to-polarization coding unit 200 are the same or orthogonal, and there is a non-zero angle with the intrinsic polarization state of the polarization combiner 84, preferably 45°.

[0110] In another embodiment, the second transmission optical path 82 or the third transmission optical path 83 is a 90° twisted polarization-maintaining fiber. Alternatively, the time phase-to-polarization encoding unit 200 further includes a 90° polarization state rotator 85 (as shown in FIG. 8). The 90° polarization state rotator 85 is disposed on the second transmission optical path 82 or the third transmission optical path 83 and is used to rotate the polarization state of the passing sub-light pulse by 90°. The 90° polarization state rotator 85 is a half-wave plate or a 90° Faraday rotator. In this case, the polarization states of the two time slot sub-light pulses input to the time phase-to-polarization encoding unit 200 are the same and are one of the intrinsic polarization states of the polarization combiner 84; or the polarization states of the two time slot sub-light pulses input to the time phase-to-polarization encoding unit 200 are the same or orthogonal and are not the intrinsic polarization states of the polarization combiner 84.

[0111] In this embodiment, the optical coupler 81 may include three ports, namely port D, port E, and port F. The polarization combiner 84 may include three ports, namely port D', port E', and port F'. Port F of the optical coupler 81 can be connected to port F' of the polarization combiner 84 through the second transmission optical path 82, and port E of the optical coupler 81 can be connected to port E' of the polarization combiner 84 through the third transmission optical path 83.

[0112] Optical coupler 81 splits a single optical pulse input from port A into two sub-optical pulses, namely a first sub-optical pulse and a second sub-optical pulse, which are output from ports F and E, respectively. The first and second sub-optical pulses are transmitted along the second transmission optical path 82 and the third transmission optical path 83, respectively. The two sub-optical pulses are input to polarization combiner 84 from ports F' and E', respectively. Polarization combiner 84 combines the two input sub-optical pulses and outputs a polarization-coded quantum state optical pulse from port D'.

[0113] Figure 9 shows a structural diagram of the fifth embodiment of the time-phase-to-polarization encoding unit 200 of this disclosure. In this embodiment, the third optical coupling unit 31 and the fourth optical coupling unit 32 are both optical couplers. The time-phase-to-polarization encoding unit 200 includes: an optical coupler 91, a second transmission optical path 92, a third transmission optical path 93, and an optical coupler 94. The two output ports of the optical coupler 91 are connected to the optical coupler 94 through the second transmission optical path 92 and the third transmission optical path 93, respectively. In one embodiment, the polarization states of the two time-slot sub-light pulses input to the time-phase-to-polarization encoding unit 200 are mutually orthogonal. In another embodiment, the second transmission optical path 92 or the third transmission optical path 93 is a 90° twisted polarization-maintaining fiber. Alternatively, the time-phase-to-polarization encoding unit 200 further includes a 90° polarization state rotator 95, which is disposed in the second transmission optical path 92 or the third transmission optical path 93 to rotate the polarization state of the passing sub-light pulses by 90°. The 90° polarization state rotator 95 can be a half-wave plate or a 90° Faraday rotator. In this case, the polarization states of the sub-light pulses in the two time slots input to the time-phase-to-polarization encoding unit 200 are the same.

[0114] Figure 10 shows a structural diagram of a sixth embodiment of the time-phase-to-polarization encoding unit 200 of this disclosure. In this embodiment, the third optical coupling unit 31 can be a polarization beam splitter, and the fourth optical coupling unit 32 is an optical coupler. The time-phase-to-polarization encoding unit 200 includes a polarization beam splitter 1001 (i.e., the third optical coupling unit 31), a second transmission optical path 1002, a third transmission optical path 1003, and an optical coupler 1004 (i.e., the fourth optical coupling unit 32).

[0115] Figure 10 shows a structural diagram of the sixth embodiment of the time-phase-to-polarization encoding unit 200 of this disclosure. In this embodiment, the polarization beamsplitter 1001 and the optical coupler 1004 are connected through a second transmission optical path 1002 and a third transmission optical path 1003. The polarization beamsplitter 1001 may include three ports: port D, port E, and port F. The optical coupler 94 may include three ports: port D', port E', and port F'. Port E of the polarization beamsplitter 1001 can be connected to port E' of the optical coupler 1004 through the third transmission optical path 1003, and port F of the polarization beamsplitter 1001 can be connected to port F' of the optical coupler 1004 through the second transmission optical path 1002.

[0116] In one embodiment, the polarization states of the two time-slot sub-light pulses input to the time-phase-to-polarization coding unit 200 are orthogonal to each other, and the polarization states of the two time-slot sub-light pulses are the intrinsic polarization states of the polarization beam splitter 1001, or have an angle of non-zero degrees with the intrinsic polarization state of the polarization beam splitter 1001; or the polarization states of the two time-slot sub-light pulses input to the time-phase-to-polarization coding unit 200 are the same, and have an angle of non-zero degrees with the intrinsic polarization state of the polarization beam splitter 1001, preferably 45°.

[0117] Figure 11 shows a structural diagram of the seventh embodiment of the time-phase-to-polarization encoding unit 200 of this disclosure. In this embodiment, the third optical coupling unit 31 can be a polarization beam splitter, and the fourth optical coupling unit 32 can be a polarization beam combiner. In this embodiment, the time-phase-to-polarization encoding unit 200 includes a polarization beam splitter 1101 (i.e., the third optical coupling unit 31), a second transmission optical path 1102, a third transmission optical path 1103, and a polarization beam combiner 1104 (i.e., the fourth optical coupling unit 32).

[0118] In one embodiment, the polarization states of the two time-slot sub-light pulses input to the time-phase-to-polarization coding unit 200 are orthogonal to each other, and the polarization states of the two time-slot sub-light pulses are the intrinsic polarization states of the polarization beam splitter 1101, or have an angle of non-zero degrees with the intrinsic polarization state of the polarization beam splitter 1101; or the polarization states of the two time-slot sub-light pulses input to the time-phase-to-polarization coding unit 200 are the same, and have an angle of non-zero degrees with the intrinsic polarization state of the polarization beam splitter 1101, preferably 45°.

[0119] As shown in Figure 11, the polarization beamsplitter 1101 and the polarization beam combiner 1104 are connected via a second transmission optical path 1102 and a third transmission optical path 1103. The polarization beamsplitter 1101 may include three ports: port D, port E, and port F. The polarization beamsplitter 1104 may include three ports: port D', port E', and port F'. Port E of the polarization beamsplitter 1101 can be connected to port E' of the polarization beam combiner 1104 via the third transmission optical path 1103, and port F of the polarization beamsplitter 1101 can be connected to port F' of the polarization beamsplitter 1104 via the second transmission optical path 1102. Port D of the polarization beamsplitter 1101 serves as the input port of the time-phase-to-polarization coding unit 200, and port D' of the polarization beam combiner 1104 serves as the output port of the time-phase-to-polarization coding unit 200.

[0120] In some embodiments, the apparatus in any of the above embodiments further includes: a first polarization controller and / or a second polarization controller. The first polarization controller is disposed at the front end of the time-phase-to-polarization encoding unit 200 or at the front end of the first optical coupling unit 100, and is used to correct the polarization state of the optical pulse input to the time-phase-to-polarization encoding unit 200. The second polarization controller is disposed at the first transmission optical path 300, at the front end of the first optical coupling unit 100, or between the second optical coupling unit 400 and the polarization decoding unit 500, and is used to correct the polarization state of the optical pulse input to the polarization decoding unit 500. Typically, the optical pulse encoding the quantum state is input to the quantum state decoding device after being transmitted through a quantum channel. During the quantum channel transmission process, its polarization state is affected by channel interference and changes. During quantum state decoding, it is necessary to correct its polarization state to compensate for the influence of quantum channel interference. When the first polarization controller is disposed at the front end of the time-phase to polarization encoding unit 200, it can correct the polarization state of the input time-phase encoded quantum state light pulse; when the first polarization controller is disposed at the front end of the first optical coupling unit 100, it can correct the polarization state of the input time-phase encoded quantum state light pulse or polarization encoded quantum state light pulse; when the second polarization controller is disposed at the first transmission optical path 300 or disposed between the second optical coupling unit 400 and the polarization decoding unit 500, it can correct the polarization state of the input polarization encoded quantum state light pulse; when the second polarization controller is disposed at the front end of the first optical coupling unit 100, it can correct the polarization state of the input time-phase encoded quantum state light pulse or polarization encoded quantum state light pulse.

[0121] Figure 12 shows a structural diagram of a first embodiment of the polarization decoding unit 500 of this disclosure. In some embodiments, the polarization decoding unit 500 includes: a first optical beamsplitter 1201, a first polarization beamsplitter 1202, and a second polarization beamsplitter 1203. The first optical beamsplitter 1201 includes three ports: an input port X and two output ports X' and X''. In this embodiment, the input port X of the first optical beamsplitter is the input port of the polarization decoding unit 500, and the two output ports X' and X''' are respectively connected to the first polarization beamsplitter 1202 and the second polarization beamsplitter 1203. The first polarization beamsplitter 1202 includes three ports: an input port Z' and two output ports Z' ... The input port Z of the first polarization beamsplitter 1202 is connected to one output port X” of the first optical beamsplitter 1201. The second polarization beamsplitter 1203 includes three ports: one input port Y and two output ports Y' and Y”. The input port Y of the second polarization beamsplitter 1203 is connected to the other output port X' of the first optical beamsplitter 1201. The two output ports Z' and Z” of the first polarization beamsplitter 1202 and the two output ports Y' and Y” of the second polarization beamsplitter 1203 are the output ports of the polarization decoding unit 500.

[0122] In the above embodiments, the polarization decoding unit 500 further includes a quarter-wave plate and / or a half-wave plate. When only a quarter-wave plate is included, it is disposed at the front end of either the first polarization beamsplitter 1202 or the second polarization beamsplitter 1203. When only a half-wave plate is included, it is disposed at the front end of either the first polarization beamsplitter 1202 or the second polarization beamsplitter 1203. When both a quarter-wave plate and a half-wave plate are included, the quarter-wave plate is disposed at the front end of either the first polarization beamsplitter 1202 or the second polarization beamsplitter 1203; the half-wave plate is disposed at the front end of the other of the first polarization beamsplitter 1202 and the second polarization beamsplitter 1203.

[0123] Figure 13 shows a structural diagram of a second embodiment of the polarization decoding unit 500 of this disclosure. The difference between this embodiment and the previous embodiment is that, in addition to the structure of the previous embodiment, the polarization decoding unit 500 further includes: a second optical beamsplitter 1304 and a third polarization beamsplitter 1305. The second optical beamsplitter 1304 includes three ports: one input port P and two output ports P' and P''. In this embodiment, the input port of the second optical beamsplitter 1304 is the input port of the polarization decoding unit 500. One output port P'' of the second optical beamsplitter 1304 is connected to the input port X of the first optical beamsplitter 1301, and the other output port P'' of the second optical beamsplitter 1304 is connected to the third polarization beamsplitter 1305. Beam splitter 1305 is connected; the third polarization beam splitter 1305 includes three ports, one input port Q and two output ports Q' and Q''. The input port Q of the third polarization beam splitter 1305 is connected to the output port P' of the second optical beam splitter 1304. The two output ports Z' and Z'' of the first polarization beam splitter 1302 and the two output ports Y' and Y'' of the second polarization beam splitter 1303 are the output ports of the polarization decoding unit 500, and the two output ports Q' and Q'' of the third polarization beam splitter 1305 also serve as the output ports of the polarization decoding unit 500.

[0124] In one exemplary embodiment, the second optical beamsplitter is a 1:2 optical beamsplitter.

[0125] According to this disclosure, a quantum state decoding method is provided, which uses the quantum state decoding device described above to achieve quantum state decoding.

[0126] This disclosure also provides a software-defined quantum communication system, as shown in FIG14, including the aforementioned quantum state decoding device 1401 and decoding control device 1402. The decoding control device 1402 is used to generate quantum communication decoding control instructions based on the decoding requirements of the quantum communication system and send them to the quantum state decoding device 1401, so that the quantum state decoding device 1401 can decode the time phase encoded quantum state light pulses or polarization encoded quantum state light pulses on demand based on the quantum communication decoding control instructions, and output the decoded quantum state light pulses.

[0127] Quantum communication systems can be discrete-variable quantum communication systems or continuous-variable quantum communication systems. It should be understood that the specific features, operations, and details described herein with respect to the apparatus of this disclosure can also be similarly applied to the methods and systems of this disclosure, or vice versa.

[0128] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A quantum state decoding apparatus, wherein, The quantum state decoding device comprises: a first optical coupling unit, a time-phase-to-polarization encoding unit, a first transmission light path, a second optical coupling unit, and a polarization decoding unit; the first optical coupling unit comprises an input port and two output ports, i.e., a first port, a second port, and a third port, the first port being an input port of the quantum state decoding device and used for receiving an input light pulse; the second optical coupling unit comprises two input ports and one output port, i.e., a fourth port, a fifth port, and a sixth port; the time-phase-to-polarization encoding unit comprises an input port and an output port, and is used for performing polarization encoding conversion on an input time-phase encoded quantum state light pulse, and outputting a polarization encoded quantum state light pulse; the third port of the first optical coupling unit is connected to the input port of the time-phase-to-polarization encoding unit, and the output port of the time-phase-to-polarization encoding unit is connected to the fifth port of the second optical coupling unit, forming a first light output branch; the second port of the first optical coupling unit is connected to the fourth port of the second optical coupling unit through the first transmission light path, forming a second light output branch; the first optical coupling unit is used for inputting the input light pulse into the first light output branch and / or the second light output branch according to a quantum communication decoding control instruction, the quantum communication decoding control instruction being determined according to a quantum communication system decoding requirement; the second optical coupling unit is used for outputting the polarization encoded quantum state light pulse output by the second light output branch or the first light output branch according to the quantum communication decoding control instruction; the polarization decoding unit comprises an input port and at least one output port, the input port of the polarization decoding unit being connected to the sixth port of the second optical coupling unit, and being used for inputting the polarization encoded quantum state light pulse and outputting the polarization encoded quantum state light pulse after decoding through the at least one output port.

2. The apparatus of claim 1, wherein, The first optical coupling unit is an optical coupler, and the second optical coupling unit is an optical switch.

3. The apparatus of claim 2, wherein, The first optical coupling unit is used for splitting the input light pulse input through the first port into two sub light pulses, and inputting the two sub light pulses into the first light output branch and the second light output branch through the third port and the second port respectively; The second optical coupling unit is used for selecting the polarization encoded quantum state light pulse output by the second light output branch or the first light output branch according to the quantum communication decoding control instruction.

4. The apparatus of claim 1, wherein, The first optical coupling unit is an optical switch, and the second optical coupling unit is an optical switch or an optical coupler.

5. The apparatus of claim 4, wherein, The first optical coupling unit is used for selecting the input light pulse input through the first port to be output to the first light output branch or the second light output branch according to the quantum communication decoding control instruction; When the second optical coupling unit is an optical switch, the second optical coupling unit is used for connecting the first light output branch or the second light output branch according to the quantum communication decoding control instruction. When the second optical coupling unit is an optical coupler, the second optical coupling unit is configured to output the polarization-encoded quantum state of light pulses output by the first optical output branch or the second optical output branch.

6. The apparatus of claim 1, wherein, the time-phase conversion polarization encoding unit comprises a third optical coupling unit, a fourth optical coupling unit, a second transmission optical path and a third transmission optical path, the third optical coupling unit comprises at least three ports, one input port and two output ports; the fourth optical coupling unit comprises at least three ports, two input ports and one output port; the two output ports of the third optical coupling unit are connected with the two input ports of the fourth optical coupling unit through the second transmission optical path and the third transmission optical path; the input port of the third optical coupling unit is the input port of the time-phase conversion polarization encoding unit, and the output port of the fourth optical coupling unit is the output port of the time-phase conversion polarization encoding unit; the second transmission optical path and the third transmission optical path have different optical lengths.

7. The apparatus of claim 6, wherein, the third optical coupling unit and the fourth optical coupling unit are the same optical coupler, and the time-phase conversion polarization encoding unit further comprises two mirrors, the two output ports of the optical coupler are connected with one end of the second transmission optical path and one end of the third transmission optical path respectively, and the two mirrors are connected with the other end of the second transmission optical path and the other end of the third transmission optical path respectively.

8. The apparatus of claim 7, wherein, one of the two mirrors is a 90° polarization state rotation mirror.

9. The apparatus of claim 6, wherein, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter, and the time-phase conversion polarization encoding unit further comprises two mirrors, the two output ports of the polarization beam splitter are connected with one end of the second transmission optical path and one end of the third transmission optical path respectively, and the two mirrors are connected with the other end of the second transmission optical path and the other end of the third transmission optical path respectively.

10. The apparatus of claim 9, wherein, the two mirrors are 90° polarization state rotation mirrors.

11. The apparatus of claim 6, wherein, the third optical coupling unit is an optical coupler, and the fourth optical coupling unit is an optical coupler or a polarization beam combiner.

12. The apparatus of claim 11, wherein, the second transmission optical path or the third transmission optical path is a 90° twisted polarization maintaining optical fiber; or the time-phase conversion polarization encoding unit further comprises a 90° polarization state rotator, which is arranged in the second transmission optical path or the third transmission optical path and is configured to rotate the polarization state of input sub-light pulses by 90°.

13. The apparatus of claim 6, wherein, the third optical coupling unit is a polarization beam splitter, and the fourth optical coupling unit is an optical coupler or a polarization beam combiner.

14. The device of any one of claims 1 to 13, wherein, the apparatus further comprises a first polarization controller and / or a second polarization controller, the first polarization controller is arranged at the front end of the time-phase conversion polarization encoding unit or at the front end of the first optical coupling unit and is configured to correct the polarization state of light pulses input into the time-phase conversion polarization encoding unit; the second polarization controller is arranged at the front end of the second optical coupling unit or at the front end of the third optical coupling unit and is configured to correct the polarization state of light pulses input into the second optical coupling unit or the third optical coupling unit. The second polarization controller is arranged on the first transmission light path, or arranged in front of the first optical coupling unit, or arranged between the second optical coupling unit and the polarization decoding unit, and is used for correcting the polarization state of the optical pulse input into the polarization decoding unit.

15. The apparatus of claim 1, wherein, The polarization decoding unit comprises a first optical beam splitter, a first polarization beam splitter and a second polarization beam splitter, The first optical beam splitter comprises three ports, one input port and two output ports, the input port of the first optical beam splitter is the input port of the polarization decoding unit, and the two output ports are connected with the first polarization beam splitter and the second polarization beam splitter respectively. The first polarization beam splitter comprises three ports, one input port and two output ports, the input port of the first polarization beam splitter is connected with one of the two output ports of the first optical beam splitter. The second polarization beam splitter comprises three ports, one input port and two output ports, the input port of the second polarization beam splitter is connected with the other of the two output ports of the first optical beam splitter.

16. The apparatus of claim 15, wherein, The polarization decoding unit further comprises a second optical beam splitter and a third polarization beam splitter, The second optical beam splitter comprises three ports, one input port and two output ports, the input port of the second optical beam splitter is the input port of the polarization decoding unit, one of the two output ports of the second optical beam splitter is connected with the input port of the first optical beam splitter, and the other is connected with the third polarization beam splitter. The third polarization beam splitter comprises three ports, one input port and two output ports, the input port of the third polarization beam splitter is connected with the other of the two output ports of the second optical beam splitter. The second optical beam splitter is a 1:2 optical beam splitter.

17. The apparatus of claim 16, wherein, The polarization decoding unit further comprises a quarter-wave plate and a half-wave plate, 18. The apparatus of any one of claims 15 to 17, wherein, The quarter-wave plate is arranged in front of any polarization beam splitter. The half-wave plate is arranged in front of any polarization beam splitter, and is not arranged in front of the same polarization beam splitter as the quarter-wave plate. The polarization decoding unit further comprises:

19. The apparatus of any one of claims 15 to 17, wherein, A quarter-wave plate arranged in front of any polarization beam splitter. The polarization decoding unit further comprises:

20. The apparatus of any one of claims 15 to 17, wherein, A half-wave plate arranged in front of any polarization beam splitter. The quantum state decoding device of any one of claims 1 to 20 is applied to realize quantum state decoding.

21. A quantum state decoding method, wherein, The quantum state decoding device of any one of claims 1 to 20 and a decoding control device are included.

22. A software-defined quantum communication system, wherein, The decoding control device is used to generate quantum communication decoding control instructions based on the decoding requirements of a quantum communication system, and sends the quantum state decoding device. ​

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