Quantum state encoding apparatus, method and software defined quantum communication system

Abstract

The application provides a quantum state encoding device, method and software-defined quantum communication system, the device comprises a polarization encoding unit, a first optical coupling unit, a polarization conversion time phase encoding unit, a first transmission optical path and a second optical coupling unit; the polarization encoding unit is used for modulating an input light pulse through at least one adjustable circular birefringence module and then outputting a polarization encoded quantum state light pulse; the polarization conversion time phase encoding unit is used for converting the polarization encoded quantum state light pulse output by the polarization encoding unit into a time phase encoded quantum state light pulse; according to a quantum communication encoding control instruction, the first optical coupling unit and the second optical coupling unit are controlled to output the polarization encoded quantum state light pulse or the time phase encoded quantum state light pulse, and the same quantum state encoding device can meet different encoding requirements of a quantum communication system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of quantum communication and optical quantum coding technology, and in particular to a quantum state coding device, a method and a software-defined quantum communication system. BACKGROUND

[0002] Quantum communication technology is a frontier and hot field combining quantum physics and information science. At present, the applications mainly include quantum key distribution and quantum direct communication. Based on physical principles such as Heisenberg uncertainty relation of quantum mechanics and quantum non-cloning theorem, quantum key distribution can securely share keys in real time between communication parties, and quantum direct communication can achieve information transmission, i.e., security. Quantum communication can detect potential eavesdropping behavior of the communication channel, and can be applied to fields such as national defense, government affairs, finance, and power with high security information transmission requirements.

[0003] The physical implementation of a quantum communication system, such as the physical implementation of quantum key distribution and quantum direct communication, requires encoding and decoding of quantum states. The commonly used quantum communication coding methods include polarization coding and time-phase coding. A set of quantum communication systems generally selects one of the coding methods, so the system is not universal and cannot be flexibly networked.

[0004] How to implement universal quantum state coding compatible with multiple quantum communication system coding methods in an optical quantum coding device is an important problem in quantum communication applications. SUMMARY

[0005] Therefore, the present application provides a quantum state coding device, a method and a quantum communication system to solve the technical problems in the background art.

[0006] According to a first aspect of the present application, a quantum state coding device is provided, comprising: a polarization coding unit, a first optical coupling unit, a polarization-to-time-phase coding unit, a first transmission optical path and a second optical coupling unit.

[0007] The polarization coding unit comprises at least one adjustable circular birefringence module, the adjustable circular birefringence module comprising a first quarter-wave plate, N built-in linear polarization operation modules and a second quarter-wave plate connected in series;

[0008] The first quarter-wave plate is used to convert left-handed circular polarization components and right-handed circular polarization components in an input light pulse into two orthogonal linear polarization components.

[0009] The built-in linear polarization operation module comprises a linear polarization control light path and at least one phase modulator; one end of the linear polarization control light path is connected with one end of the first quarter-wave plate, for receiving the light pulse containing the two orthogonal linear polarization components converted by the first quarter-wave plate, and splitting the light pulse into two sub light pulses, at least one of the two sub light pulses is phase-modulated by the phase modulator to generate a phase difference between the two sub light pulses, and the two sub light pulses with the phase difference are combined and output through the output end;

[0010] One end of the second quarter-wave plate is connected with the output end of the linear polarization control light path, for converting the two orthogonal linear polarization components in the light pulse output by the linear polarization control light path into left circular polarization components and right circular polarization components and outputting the light pulse through the output end;

[0011] The first optical coupling unit comprises one input port and two output ports, i.e. a first port, a second port and a third port, the first port is connected with the output end of the second quarter-wave plate in the polarization encoding unit;

[0012] 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;

[0013] The polarization-to-time-phase encoding unit comprises one input port and one output port, for performing time-phase encoding conversion on the input polarization encoded quantum state light pulse, and outputting a time-phase encoded quantum state light pulse;

[0014] The third port of the first optical coupling unit is connected with the input port of the polarization-to-time-phase encoding unit, and the output port of the polarization-to-time-phase encoding unit is connected with the fifth port of the second optical coupling unit, forming a first light output branch;

[0015] The second port of the first optical coupling unit is connected with the fourth port of the second optical coupling unit through the first transmission light path, forming a second light output branch;

[0016] The first optical coupling unit is used for inputting the polarization encoded quantum state light pulse output by the polarization encoding unit into the first light output branch and / or the second light output branch according to the quantum communication encoding control instruction, and the quantum communication encoding control instruction is determined according to the quantum communication system encoding requirement;

[0017] The sixth port of the second optical coupling unit is an output port of the quantum state encoding device, for outputting the polarization encoded quantum state light pulse transmitted by the second light output branch or the time-phase encoded quantum state light pulse output by the first light output branch according to the quantum communication encoding control instruction.

[0018] According to the second aspect of the present application, a quantum state encoding method is provided, applied to the quantum state encoding device.

[0019] According to the third aspect of the present application, a software-defined quantum communication system is provided, comprising the quantum state encoding device and the encoding control device.

[0020] The encoding control device is configured to generate quantum communication encoding control instructions based on the encoding requirements of the quantum communication system, and send the quantum state encoding device.

[0021] In summary, the quantum state encoding device, method and software-defined quantum communication system provided by the embodiments of the present application have at least the following beneficial effects:

[0022] The present application can control the output of polarization-encoded quantum state light pulses or time-phase-encoded quantum state light pulses according to the quantum communication encoding control instructions, so that the same quantum state encoding device can meet the different encoding requirements of the quantum communication system to realize the encoding output of multi-form quantum state light pulses, and the encoding requirements of the quantum communication system are met.

[0023] The present application can also meet the security requirements of quantum communication, reduce the number of lasers used, and reduce the weight and power consumption of the quantum communication transmitter. The polarization-encoded quantum state of the present application has strong stability and can meet the demand for time-phase-encoded quantum states in space quantum communication applications. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 The structure schematic diagram of a first embodiment of a quantum state encoding device provided by the embodiments of the present application is shown;

[0026] Figure 2 The structure schematic diagram of a first embodiment of a polarization encoding unit provided by the embodiments of the present application is shown;

[0027] Figure 3 The structure schematic diagram of a second embodiment of a quantum state encoding device provided by the embodiments of the present application is shown;

[0028] Figure 4 The structure schematic diagram of a first embodiment of a linear polarization operation module provided by the embodiments of the present application is shown;

[0029] Figure 5 Fig. 6 shows a structural schematic diagram of a second embodiment of the linear polarization operation module provided by the embodiment of the present application;

[0030] Figure 6 Fig. 7 shows a structural schematic diagram of a third embodiment of the linear polarization operation module provided by the embodiment of the present application;

[0031] Figure 7 Fig. 8 shows a structural schematic diagram of a fourth embodiment of the linear polarization operation module provided by the embodiment of the present application;

[0032] Figure 8 Fig. 9 shows a structural schematic diagram of a fifth embodiment of the linear polarization operation module provided by the embodiment of the present application;

[0033] Figure 9 Fig. 10 shows a structural schematic diagram of a sixth embodiment of the linear polarization operation module provided by the embodiment of the present application;

[0034] Figure 10 Fig. 11 shows a structural schematic diagram of a seventh embodiment of the linear polarization operation module provided by the embodiment of the present application;

[0035] Figure 11 Fig. 12 shows a structural schematic diagram of an eighth embodiment of the linear polarization operation module provided by the embodiment of the present application;

[0036] Figure 12 Fig. 13 shows a structural schematic diagram of a second embodiment of the polarization encoding unit provided by the embodiment of the present application;

[0037] Figure 13 Fig. 14 shows a structural schematic diagram of a third embodiment of the polarization encoding unit provided by the embodiment of the present application;

[0038] Figure 14 Fig. 15 shows a structural schematic diagram of a fourth embodiment of the polarization encoding unit provided by the embodiment of the present application;

[0039] Figure 15 Fig. 16 shows a structural schematic diagram of a fifth embodiment of the polarization encoding unit provided by the embodiment of the present application;

[0040] Figure 16 Fig. 17 shows a structural schematic diagram of a sixth embodiment of the polarization encoding unit provided by the embodiment of the present application;

[0041] Figure 17 Fig. 18 shows a structural schematic diagram of a seventh embodiment of the polarization encoding unit provided by the embodiment of the present application;

[0042] Figure 18 Fig. 19 shows a structural schematic diagram of an eighth embodiment of the polarization encoding unit provided by the embodiment of the present application;

[0043] Figure 19A structure diagram of a ninth embodiment of the polarization encoding unit provided by the embodiment of the application is shown.

[0044] Figure 20 A structure diagram of a tenth embodiment of the polarization encoding unit provided by the embodiment of the application is shown.

[0045] Figure 21 A structure diagram of an eleventh embodiment of the polarization encoding unit provided by the embodiment of the application is shown.

[0046] Figure 22 A structure diagram of a twelfth embodiment of the polarization encoding unit provided by the embodiment of the application is shown.

[0047] Figure 23 A structure diagram of a thirteenth embodiment of the polarization encoding unit provided by the embodiment of the application is shown.

[0048] Figure 24 A structure diagram of a first embodiment of the polarization rotation time phase encoding unit provided by the embodiment of the application is shown.

[0049] Figure 25 A structure diagram of a second embodiment of the polarization rotation time phase encoding unit provided by the embodiment of the application is shown.

[0050] Figure 26 A structure diagram of a third embodiment of the polarization rotation time phase encoding unit provided by the embodiment of the application is shown.

[0051] Figure 27 A structure diagram of a fourth embodiment of the polarization rotation time phase encoding unit provided by the embodiment of the application is shown.

[0052] Figure 28 A structure diagram of a fifth embodiment of the polarization rotation time phase encoding unit provided by the embodiment of the application is shown.

[0053] Figure 29 A structure diagram of a sixth embodiment of the polarization rotation time phase encoding unit provided by the embodiment of the application is shown.

[0054] Figure 30 A structure diagram of a seventh embodiment of the polarization rotation time phase encoding unit provided by the embodiment of the application is shown.

[0055] Figure 31 A structure diagram of a software defined quantum communication system provided by the embodiment of the application is shown. DETAILED DESCRIPTION

[0056] To make the above and other features and advantages of this application clearer, the application 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.

[0057] In the following description, numerous specific details are set forth to provide a thorough understanding of this application. However, it will be apparent to those skilled in the art that the specific details are not required to practice this application. In other instances, well-known steps or operations have not been described in detail to avoid obscuring this application.

[0058] It should be noted that the time phase encoding described in this application 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.

[0059] One embodiment of this application provides a quantum state encoding device, as shown in the attached document. Figure 1 This is a schematic diagram of the structure of a first embodiment of a quantum state encoding device provided in this application. The quantum state encoding device includes: a polarization encoding unit 110, a first optical coupling unit 120, a polarization-to-time phase encoding unit 130, a first transmission optical path 140, and a second optical coupling unit 150.

[0060] In one embodiment, such as Figure 2 As shown, the polarization encoding unit 110 includes at least one adjustable circular birefringence module. The adjustable circular birefringence module includes a first quarter-wave plate 111, N built-in linear polarization operation modules 112, and a second quarter-wave plate 113 connected in series; N is an integer greater than or equal to 1. Figure 2 The illustration shows only one embodiment that includes an adjustable circular birefringence module, and that the adjustable circular birefringence module includes only one built-in linear polarization operation module 112.

[0061] The first quarter-wave plate 111 is used to convert the left-hand circularly polarized component and the right-hand circularly polarized component in the input optical pulse into two orthogonal linearly polarized components.

[0062] In some implementations, refer again to the appendix. Figure 2 As shown, the built-in linear polarization operation module 112 includes a linear polarization control optical path 114 and at least one phase modulator 115. The input end of the linear polarization control optical path 114 is connected to one end of the first quarter-wave plate 111, and is used to receive the light pulse containing the two orthogonal linear polarization components after being converted by the first quarter-wave plate 111, and split it into two sub-light pulses. The phase modulator 115 modulates at least one of the two sub-light pulses to generate a phase difference between the two sub-light pulses, and combines the two sub-light pulses that have generated a phase difference and outputs them through the output end.

[0063] In some embodiments, referring again to FIG. 1, the second quarter wave plate 113 is connected to an output end of the linear polarization control optical path 114, for converting the two orthogonal linear polarization components in a light pulse output by the linear polarization control optical path 114 into left-handed circular polarization components and right-handed circular polarization components, and outputting the left-handed circular polarization components and right-handed circular polarization components through the output end. Figure 2

[0064] In some embodiments, referring again to FIG. 1, the first optical coupling unit 120 comprises an input port and two output ports, i.e., a first port L, a second port M and a third port N, and the first port L is connected to the output end O of the second quarter wave plate 113 in the polarization encoding unit 110. Figure 3

[0065] In some embodiments, referring again to FIG. 1, the second optical coupling unit 150 comprises two input ports and an output port, i.e., a fourth port M’, a fifth port N’ and a sixth port L’. Figure 3

[0066] In some embodiments, referring again to FIG. 1, the polarization-to-time phase encoding unit 130 comprises an input port P and an output port Q, for performing time phase encoding conversion on a light pulse of the input polarization encoded quantum state, and outputting a light pulse of a time phase encoded quantum state. Figure 3

[0067] In some embodiments, referring again to FIG. 1, the third port N of the first optical coupling unit 120 is connected to the input port P of the polarization-to-time phase encoding unit 130, and the output port Q of the polarization-to-time phase encoding unit 130 is connected to the fifth port N’ of the second optical coupling unit 150, forming a first light output branch. Figure 3

[0068] In some embodiments, referring again to FIG. 1, the second port M of the first optical coupling unit 120 is connected to the fourth port M’ of the second optical coupling unit 150 through the first transmission optical path 140, forming a second light output branch. Figure 3

[0069] In some embodiments, referring again to FIG. 1, the first optical coupling unit 120 is configured to input the light pulse of the polarization encoded quantum state output by the polarization encoding unit 110 into the first light output branch and / or the second light output branch according to a quantum communication encoding control instruction, and the quantum communication encoding control instruction is determined according to the encoding requirement of the quantum communication system. Figure 3

[0070] In some embodiments, referring again to FIG. 1, the third port N of the first optical coupling unit 120 is connected to the input port P of the polarization-to-time phase encoding unit 130, and the output port Q of the polarization-to-time phase encoding unit 130 is connected to the fifth port N’ of the second optical coupling unit 150, forming a first light output branch. Figure 3 ​​​​​​​As shown, the sixth port L' of the second optical coupling unit 150 is an output port of the quantum state encoding device, and is configured to output the polarization-encoded quantum state light pulse transmitted by the second optical output branch or the time-phase-encoded quantum state light pulse output by the first optical output branch according to the quantum communication encoding control instruction.

[0071] The quantum communication encoding control instruction can be used to control the output of the polarization-encoded quantum state light pulse or the output of the time-phase-encoded quantum state light pulse, so that the same quantum state encoding device can meet the different encoding requirements of the quantum communication system to realize the encoding output of quantum state light pulses in multiple forms, thereby meeting the encoding requirements of the quantum communication system. The quantum communication security requirement can be met, the number of lasers used is reduced, and the weight and power consumption of the quantum communication transmitter are reduced. The polarization-encoded quantum state has high stability and can meet the requirements of space quantum communication applications for polarization-encoded quantum states and time-phase-encoded quantum states.

[0072] In some embodiments, the first optical coupling unit 120 is an optical coupler, and the second optical coupling unit 150 is an optical switch. As shown, Figure 3 The first optical coupling unit 120 is configured to input the polarization-encoded quantum state light pulse output by the polarization encoding unit 110 through the first port L, and split the polarization-encoded quantum state light pulse into two sub light pulses, which are input into the first optical output branch and the second optical output branch through the third port N and the second port M, respectively. The second optical coupling unit 150 is configured to select the polarization-encoded quantum state light pulse transmitted by the second optical output branch or the time-phase-encoded quantum state light pulse output by the first optical output branch according to the quantum communication encoding control instruction.

[0073] In some embodiments, the first optical coupling unit 120 is an optical switch, and the second optical coupling unit 150 is an optical switch or an optical coupler. The first optical coupling unit 120 is configured to select the polarization-encoded quantum state light pulse to be input into the first optical output branch or the second optical output branch according to the quantum communication encoding control instruction. When the second optical coupling unit 150 is an optical switch, the second optical coupling unit 150 is configured to connect the first optical output branch outputting the time-phase-encoded quantum state light pulse or the second optical output branch outputting the polarization-encoded quantum state light pulse according to the quantum communication encoding control instruction.

[0074] In some other embodiments, when the second optical coupling unit 150 is an optical coupler, the second optical coupling unit 150 is configured to output the time-phase-encoded quantum state light pulse output by the first optical output branch or the polarization-encoded quantum state light pulse transmitted by the second optical output branch.

[0075] In some implementations, refer to the appendix. Figure 4 As shown, the linear polarization control optical path 114 includes: a third optical coupling unit 123, a fourth optical coupling unit 124, a second transmission optical path 125, and a third transmission optical path 126; the third optical coupling unit 123 and the fourth optical coupling unit 124 are connected through the second transmission optical path 125 and the third transmission optical path 126; the phase modulator 115 is disposed on the second transmission optical path 125 or the third transmission optical path 126.

[0076] In some embodiments, the third optical coupling unit 123 is used to receive the light pulse containing the two orthogonal linearly polarized components after being converted by the first quarter-wave plate 111, and split it into two sub-light pulses, namely the first sub-light pulse and the second light pulse, which are transmitted along the second transmission optical path 125 and the third transmission optical path 126 in the linear polarization control optical path 114, respectively.

[0077] In some embodiments, the phase modulator 115 is used to phase modulate at least one of the first and second optical pulses to generate a phase difference between the two optical pulses; the fourth optical coupling unit 124 is used to receive the two optical pulses that generate a phase difference and combine them into a single optical pulse for output.

[0078] In any of the above embodiments, one of the two intrinsic polarization states of the first quarter-wave plate 111 One of the two intrinsic polarization states of the linear polarization control optical path 114 The included angle is 45°±n·90°; one of the two intrinsic polarization states of the second quarter-wave plate 113. One of the two intrinsic polarization states of the linear polarization control optical path 114 The included angle is 45°±m·90°, where n and m are integers.

[0079] In some implementations, such as Figure 5 As shown, the third optical coupling unit 123 is a polarization beam splitter, and the fourth optical coupling unit 124 is a polarization beam combiner. The intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the linear polarization control optical path 114.

[0080] In some implementations, such as Figure 6 As shown, the third optical coupling unit 123 is a polarization beam splitter, and the fourth optical coupling unit 124 is an optical coupler. The intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the linear polarization control optical path 114.

[0081] In some implementations, such as Figure 7As shown, the third optical coupling unit 123 is an optical coupler, and the fourth optical coupling unit 124 is a polarization beam combiner, and the eigenpolarization state of the polarization beam combiner is the eigenpolarization state of the linear polarization control light path 114.

[0082] In some embodiments, as shown in FIG. 1, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter 123, and the linear polarization control light path 114 further comprises two mirrors 211 and 212, the mirror 211 and the mirror 212 are connected with the second transmission light path 125 and the third transmission light path 126 respectively, and are used to reflect the light pulses input into the mirror 211 and the mirror 212 back to the polarization beam splitter 123; and the eigenpolarization state of the polarization beam splitter 123 is the eigenpolarization state of the linear polarization control light path 114. Figure 8 In some embodiments, the polarization beam splitter 123 can include at least three ports, at least one input port and two output ports, which are port A, port B and port C respectively, and the port B and the port C are connected with the two mirrors through the third transmission light path 126 and the second transmission light path 125 respectively, and the port A is used as the input port to receive the light pulses input into the linear polarization control light path 114. Specifically, as shown in FIG. 1, the port B is connected with the mirror 212 through the third transmission light path 126, and the port C is connected with the mirror 211 through the second transmission light path 125.

[0083] Figure 8 In some embodiments, the polarization beam splitter 123 can include at least three ports, at least one input port and two output ports, which are port A, port B and port C respectively, and the port B and the port C are connected with the two mirrors through the third transmission light path 126 and the second transmission light path 125 respectively, and the port A is used as the input port to receive the light pulses input into the linear polarization control light path 114. Specifically, as shown in FIG. 1, the port B is connected with the mirror 212 through the third transmission light path 126, and the port C is connected with the mirror 211 through the second transmission light path 125.

[0084] In some embodiments, the polarization beam splitter 123 can include at least three ports, at least one input port and two output ports, which are port A, port B and port C respectively, and the port B and the port C are connected with the two mirrors through the third transmission light path 126 and the second transmission light path 125 respectively, and the port A is used as the input port to receive the light pulses input into the linear polarization control light path 114. Specifically, as shown in FIG. 1, the port B is connected with the mirror 212 through the third transmission light path 126, and the port C is connected with the mirror 211 through the second transmission light path 125.

[0085] In some embodiments, the polarization beam splitter 123 can include at least three ports, at least one input port and two output ports, which are port A, port B and port C respectively, and the port B and the port C are connected with the two mirrors through the third transmission light path 126 and the second transmission light path 125 respectively, and the port A is used as the input port to receive the light pulses input into the linear polarization control light path 114. Specifically, as shown in FIG. 1, the port B is connected with the mirror 212 through the third transmission light path 126, and the port C is connected with the mirror 211 through the second transmission light path 125. Figure 8 ​As shown, the polarization beam splitter 123 can further include an output port D as an output port of the linear polarization control optical path 114 for outputting the light pulses linear birefringence modulated by the linear polarization control optical path 114.

[0086] In some embodiments, the mirrors 211 and 212 can be polarization state rotation mirrors that rotate the polarization state of the reflected sub-pulses by a certain angle, for example, 90° polarization state rotation mirrors, the mirrors 211 and 212 can be quarter-wave plate mirrors or 90° Faraday rotation mirrors.

[0087] It should be noted that, in the case that the mirrors 211 and 212 do not rotate the polarization state of the input sub-pulses, the polarization beam splitter 123 only outputs the combined light pulses from the port A. In the case that the mirrors 211 and 212 rotate the polarization state of the input sub-pulses by any angle (not 0 and 90°), the polarization beam splitter 123 can output the combined light pulses from the port A or the port D, wherein if the polarization state of the sub-pulses is rotated by 90°, the combined light pulses can only be output from the port D, and when the polarization state is rotated by 90°, the mirrors 211 and 212 are 90° polarization state rotation mirrors, which can be quarter-wave plate mirrors or 90° Faraday rotation mirrors.

[0088] In some embodiments, as shown in FIG. 2, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitting unit 201, the second transmission optical path and the third transmission optical path are the same transmission optical path 205, and the eigenpolarization state of the polarization beam splitting unit 201 is the eigenpolarization state of the linear polarization control optical path 114. Figure 9

[0089] In some embodiments, as shown in FIG. 2, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitting unit 201, the second transmission optical path and the third transmission optical path are the same transmission optical path 205, and the eigenpolarization state of the polarization beam splitting unit 201 is the eigenpolarization state of the linear polarization control optical path 114. Figure 9

[0090] ​​In the above embodiment, the input and output of the linear polarization control optical path 114 are the same port. In this case, the polarization encoding unit 110 also includes an optical coupling unit. The optical coupling unit includes at least three ports, namely a first port, a second port, and a third port. The optical coupling unit can be disposed between the first quarter-wave plate 111 and the polarization beam splitter. The first port of the optical coupling unit is connected to the first quarter-wave plate 111, the second port of the optical coupling unit is connected to the polarization beam splitter, and the third port of the optical coupling unit is connected to the second quarter-wave plate 113. Alternatively, the optical coupling unit can be disposed before the first quarter-wave plate 111. The first port of the optical coupling unit receives one input optical pulse, the second port of the optical coupling unit is connected to the first quarter-wave plate 111, and the third port of the optical coupling unit is the output port. In this case, the first quarter-wave plate 111 and the second quarter-wave plate 113 are the same device. The optical coupling unit is an optical coupler or an optical circulator.

[0091] In some implementations, such as Figure 10 As shown, the polarization beam splitter unit includes: a polarization beam splitter 201, a first polarizer 206, and a second polarizer 207. The polarization beam splitter 201 has four ports: a first port A, a second port B, a third port C, and a fourth port D. The first port A of the polarization beam splitter 201 is the input port of the linear polarization control optical path 114, and the fourth port D of the polarization beam splitter 201 is the output port of the linear polarization control optical path 114. The second port B and the third port C of the polarization beam splitter 201 are respectively connected to the first side of the first polarizer 206. The port on the first side of the first polarizer 206 and the port on the second side of the second polarizer 207 are connected; the port on the second side of the first polarizer 206 and the port on the second side of the second polarizer 207 are connected through the transmission optical path 205; the angle between the polarization direction of the first polarizer 206 and one intrinsic polarization state of the polarization beam splitter 201 is θ, and the angle between the polarization direction of the second polarizer 207 and another intrinsic polarization state of the polarization beam splitter 201 is δ, where θ and δ ≠ n·90°, and n is an integer; the intrinsic polarization state of the polarization beam splitter 201 is the intrinsic polarization state of the polarization beam splitting unit.

[0092] In some implementations, such as Figure 11As shown, the polarization beam splitting unit comprises a light beam splitter 201, a first polarizer 206 and a second polarizer 207; the light beam splitter 201 comprises at least three ports, i.e. a first port A, a second port B and a third port C, the first port A of the light beam splitter 201 is the input port of the linear polarization control light path 114; the second port B and the third port C of the light beam splitter 201 are connected with the port on the first side of the first polarizer 206 and the port on the first side of the second polarizer 207 respectively; the port on the second side of the first polarizer 206 and the port on the second side of the second polarizer 207 are connected through the transmission light path 205. The polarization direction of the first polarizer 206 is The polarization direction of the second polarizer 207 is The polarization direction of the first polarizer 206 is orthogonal to the polarization direction of the second polarizer 207. The polarization direction of the first polarizer 206 is orthogonal to the polarization direction of the second polarizer 207. The polarization direction of the first polarizer 206 is

[0093] In the above embodiments, when the input and output of the linear polarization control light path 114 are the same port, at this time, the polarization encoding unit 110 further comprises an optical coupling unit, the optical coupling unit comprises at least three ports, i.e. a first port, a second port and a third port, the optical coupling unit can be arranged between the first quarter wave plate 111 and the light beam splitter 201, the first port of the optical coupling unit is connected with the first quarter wave plate 111, the second port of the optical coupling unit is connected with the light beam splitter 201, and the third port of the optical coupling unit is connected with the second quarter wave plate 113; or the optical coupling unit can be arranged before the first quarter wave plate 111, the first port of the optical coupling unit receives an input light pulse, the second port of the optical coupling unit is connected with the first quarter wave plate 111, and the third port of the optical coupling unit is an output port, at this time, the first quarter wave plate 111 and the second quarter wave plate 113 are the same device; the optical coupling unit is an optical coupler or an optical circulator.

[0094] In some embodiments, the light beam splitter 201 further comprises a fourth port D (not shown in the figure); the fourth port D of the light beam splitter 201 is the output port of the linear polarization control light path 114.

[0095] In some embodiments, the transmission light path 205 is a free space light path or a polarization maintaining optical fiber. Figures 9-11

[0096] Referring to the accompanying drawings Figures 9-11 ​In any of the accompanying drawings, a phase modulator 115 is disposed on the transmission optical path 205; the phase modulator 115 includes a first port E and a second port F, which are respectively a forward input optical port and a reverse input optical port; the phase modulator 115 modulates the optical pulse input to one of the first port E and the second port F, or modulates the optical pulse input to the first port E and the second port F with different phases.

[0097] In the above embodiment, after applying a high-frequency modulation electrical signal with a frequency higher than a specified threshold, the phase modulator 115 operates in a non-reciprocal state, and the ratio of the modulation efficiency of the first sub-optical pulse input from the forward input optical port to the modulation efficiency of the second sub-optical pulse input from the reverse input optical port is not less than a preset threshold. When the phase modulator 115 applies a high-frequency modulation signal with a frequency higher than the specified threshold, multiple sub-optical pulses input from the forward input optical port and multiple sub-optical pulses input from the reverse input optical port can exist in the phase modulator 115 at the same time.

[0098] In some of these embodiments, see Appendix Figures 9-11 In any of the accompanying drawings, the transmission optical path 205 is coupled to the slow axis of the first port E and the second port F of the phase modulator 115, or is coupled to the fast axis of the first port E and the second port F of the phase modulator 115.

[0099] In some of these embodiments, see Appendix Figures 9-11 As shown in any of the accompanying drawings, the polarization encoding unit 110 of this application further includes a polarization state rotator disposed in the transmission optical path 205, wherein the polarization state rotator may be a half-wave plate or a 90-degree Faraday rotator.

[0100] In some embodiments, when the input and output of the linear polarization control optical path 114 are at the same port, refer to the attached diagram. Figure 12 As shown, the polarization encoding unit 110 further includes: an optical coupling unit 117; the optical coupling unit 117 is an optical coupler or an optical circulator, the optical coupling unit 117 is disposed in front of the first quarter-wave plate 111, and the optical coupling unit 117 is connected to the first quarter-wave plate 111.

[0101] In the above embodiments, please refer again to the appendix. Figure 12 As shown, when the input and output of the linear polarization control optical path 114 are at the same port, the first quarter-wave plate 111 and the second quarter-wave plate 113 can also be the same device (i.e., Figure 12 In the first quarter-wave plate 111, the optical coupling unit 117 is placed before the first quarter-wave plate 111 to separate the input and output functions of the first quarter-wave plate 111. The optical coupling unit 117 is an optical coupler or an optical circulator.

[0102] In other embodiments, see Appendix Figure 13 As shown, when the input and output of the linear polarization control optical path 114 are at the same port, the optical coupling unit 117 can be directly connected in series at the front end of the polarization beam splitter 201. In this case, the input and output functions of the polarization beam splitter 201 can be separated. The first quarter-wave plate 111 and the second quarter-wave plate 113 are not the same device; the optical coupling unit 117 is also connected separately to the first quarter-wave plate 111 and the second quarter-wave plate 113 to realize the input and output of optical pulses. The optical coupling unit 117 is an optical coupler or an optical circulator.

[0103] In some implementations, refer to the appendix. Figure 14 As shown, when N is 2, that is, when the adjustable circular birefringence module includes two built-in linear polarization operation modules 112, the two built-in linear polarization operation modules 112 are connected in series between the first quarter-wave plate 111 and the second quarter-wave plate 113.

[0104] In some implementations, refer to the appendix. Figure 15 As shown, the polarization encoding unit 110 of this application further includes: M external linear polarization operation modules, such as... Figure 15 The second linear polarization operation module 116 is located within the module. The external linear polarization operation module is connected in series with the adjustable circular birefringence module, where M is an integer greater than or equal to 1. (Appendix) Figure 15 The adjustable circular birefringence module structure is based on Figure 2 Taking the structure shown as an example, as Figure 15 The diagram shows the structure of the polarization encoding unit 110, which includes an external linear polarization operation module.

[0105] It should be noted that the external linear polarization operation module and the built-in linear polarization operation module 112 described in this application embodiment have the same structure and function. In this application embodiment, the linear polarization operation module set in the adjustable circular birefringence module is referred to as the built-in linear polarization operation module. Figure 15 The first linear polarization operation module 112 in the module; the linear polarization operation module set outside the adjustable circular birefringence module and connected in series with the adjustable circular birefringence module is called the external linear polarization operation module, such as Figure 15 The second linear polarization operation module 116 in the diagram. See attached diagram. Figure 15 As shown in the attached figure, the second linear polarization operation module 116 in this embodiment can be disposed in front of the first quarter-wave plate 111; or it can be disposed as shown in the attached figure. Figure 16 As shown, the second linear polarization operation module 116 is positioned behind the second quarter-wave plate 113.

[0106] In some embodiments, when M is 2, i.e. the polarization encoding unit 110 of the present application comprises two external linear polarization operation modules (i.e. the second linear polarization operation module 116 and the third linear polarization operation module 116), the second linear polarization operation module 116 and the third linear polarization operation module 116 are connected in series, as shown in FIG. 1B. Figure 17 As shown in FIG. 1B, the second linear polarization operation module 116 and the third linear polarization operation module 116 can be both arranged in front of the first quarter-wave plate 111; or as shown in FIG. 1C, the second linear polarization operation module 116 and the third linear polarization operation module 116 can be both arranged behind the second quarter-wave plate 113; or as shown in FIG. 1D, one of the second linear polarization operation module 116 and the third linear polarization operation module 116 can be arranged in front of the first quarter-wave plate 111, and the other can be arranged behind the second quarter-wave plate 113. In the present embodiment, the second linear polarization operation module 116 is arranged in front of the first quarter-wave plate 111, and the third linear polarization operation module 116 is arranged behind the second quarter-wave plate 113. It can be understood that the positions of the second linear polarization operation module 116 and the third linear polarization operation module 116 can be interchanged. Figure 18 Figure 19 As shown in FIG. 1B, the second linear polarization operation module 116 and the third linear polarization operation module 116 can be both arranged in front of the first quarter-wave plate 111; or as shown in FIG. 1C, the second linear polarization operation module 116 and the third linear polarization operation module 116 can be both arranged behind the second quarter-wave plate 113; or as shown in FIG. 1D, one of the second linear polarization operation module 116 and the third linear polarization operation module 116 can be arranged in front of the first quarter-wave plate 111, and the other can be arranged behind the second quarter-wave plate 113. In the present embodiment, the second linear polarization operation module 116 is arranged in front of the first quarter-wave plate 111, and the third linear polarization operation module 116 is arranged behind the second quarter-wave plate 113. It can be understood that the positions of the second linear polarization operation module 116 and the third linear polarization operation module 116 can be interchanged.

[0107] In yet some embodiments, when M is 2, i.e. the polarization encoding unit 110 of the present application comprises two external linear polarization operation modules (i.e. the second linear polarization operation module 116 and the third linear polarization operation module 116), the included angle between the eigenpolarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116 is n·22.5°, wherein n is an integer.

[0108] Based on the above embodiments, in the case that the included angle between the eigenpolarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116 is n·22.5°, the included angle between the eigenpolarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116 is realized by rotating at least one of the second linear polarization operation module 116 and the third linear polarization operation module 116.

[0109] In some other embodiments, the polarization encoding unit 110 further comprises a polarization state rotator arranged between the second linear polarization operation module 116 and the third linear polarization operation module 116, and the included angle between the eigenpolarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116 is adjusted by the polarization state rotator.

[0110] ​In some embodiments, the polarization encoding unit 110 further comprises two polarization state rotators, which are respectively arranged at the front end and the rear end of one of the second linear polarization operation module 116 and the third linear polarization operation module 116, and the two polarization state rotators are used to adjust the included angle between the eigenpolarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116.

[0111] In some embodiments, when N is greater than 1, i.e., the number N of the built-in linear polarization operation modules 112 is greater than 1, the device further comprises N-1 optical isolation units, which can be optical isolators or optical circulators, and the N-1 optical isolation units are respectively arranged between any two adjacent built-in linear polarization operation modules.

[0112] In some embodiments, when N is greater than 1 and / or M is greater than 1, i.e., the number N of the built-in linear polarization operation modules 112 is greater than 1 and / or the number M of the external linear polarization operation modules 116 is greater than 1, the device further comprises N+M-1 optical isolation units, which are optical isolators or optical circulators, and the N+M-1 optical isolation units are respectively arranged between any two adjacent linear polarization operation modules (including the built-in linear polarization operation modules and the external linear polarization operation modules).

[0113] In some embodiments, the polarization state of the optical pulse input into the quantum state encoding device can be any linear polarization state, for example, the polarization state of the optical pulse input into the device can be a horizontal polarization state or a vertical polarization state.

[0114] In some embodiments, when M is 1 and the external linear polarization operation module is arranged in front of the first quarter wave plate 111, the polarization state of the optical pulse input into the device is wherein, and are the two eigenpolarization states of the linear polarization control optical path of the second linear polarization operation module, and θ is any value in the range of 0-2π.

[0115] In some embodiments, referring to FIG. 2, the polarization encoding unit 110 of the present application can comprise two series-connected adjustable circular birefringence modules. Figure 20

[0116] In some embodiments, when the two adjustable circular birefringence modules are connected in series with the external linear polarization operation module, the external linear polarization operation module can be arranged in front of the two adjustable circular birefringence modules, behind the two adjustable circular birefringence modules, or between the two adjustable circular birefringence modules. ​

[0117] In some of these implementations, such as Figure 21 In the process, the polarization encoding unit 110 includes two cascaded adjustable circular birefringence modules and an external linear polarization operation module, such as... Figure 21 The second linear polarization operation module 116 can be set in front of the first quarter-wave plate 111, that is, in front of the first adjustable circular birefringence module.

[0118] In some other implementations, such as Figure 22 As shown, the second linear polarization operation module 116 can be positioned between the two adjustable circular birefringence modules, that is, positioned after the second quarter-wave plate 113 of the first adjustable circular birefringence module and in front of the first quarter-wave plate 111 of the second adjustable circular birefringence module.

[0119] In some other implementations, such as Figure 23 As shown, the second linear polarization operation module 116 can also be set after the two adjustable circular birefringence modules, that is, connected to the second quarter-wave plate 113 of the second adjustable circular birefringence module.

[0120] In some implementations, such as Figure 24 As shown, the polarization-to-time phase encoding unit 130 includes: a fifth optical coupling unit 221, a sixth optical coupling unit 222, a fourth transmission optical path 223, and a fifth transmission optical path 224. The fifth optical coupling unit 221 includes at least three ports: one input port G and two output ports I and H. The sixth optical coupling unit 222 includes at least three ports: two input ports I' and H' and one output port G'. The two output ports I and H of the fifth optical coupling unit 221 are connected to the two input ports I' and H' of the sixth optical coupling unit 222 through the fourth transmission optical path 223 and the fifth transmission optical path 224. The optical paths of the fourth transmission optical path 223 and the fifth transmission optical path 224 are not equal.

[0121] In some implementations, such as Figure 25 As shown, the fifth optical coupling unit 221 is a polarization beam splitter, and the sixth optical coupling unit 222 is a polarization beam combiner.

[0122] In some implementations, such as Figure 26 As shown, the fifth optical coupling unit 221 is a polarization beam splitter, and the sixth optical coupling unit 222 is an optical coupler.

[0123] In some implementations, such as Figure 27 As shown, the fifth optical coupling unit 221 is an optical coupler, and the sixth optical coupling unit 222 is a polarization beam combiner.

[0124] In some implementations, such as Figure 28As shown, the fifth light coupling unit 221 is a light coupler, and the sixth light coupling unit 222 is a light coupler. The polarization conversion and time phase encoding unit 130 further comprises two polarizers 225 and 226. The polarizer 225 and the polarizer 226 are arranged on the fourth transmission light path 223 and the fifth transmission light path 224 respectively, and the polarization directions of the polarizer 225 and the polarizer 226 are orthogonal to each other.

[0125] In some embodiments, reference is made to any of the accompanying drawings, the fourth transmission light path 223 and the fifth transmission light path 224 are 90° twisted polarization maintaining optical fibers, or the polarization conversion and time phase encoding unit 130 of the present application further comprises a 90° polarization state rotator arranged on the fourth transmission light path 223 or the fifth transmission light path 224, for rotating the polarization state of the passing sub-light pulse by 90°. Figures 26-28

[0126] In some embodiments, as shown, the fifth light coupling unit and the sixth light coupling unit are the same polarization beam splitter 221. The polarization conversion and time phase encoding unit 130 further comprises two mirrors 227 and 228. The two output ports I and H of the polarization beam splitter 221 are connected with one end of the fourth transmission light path 223 and one end of the fifth transmission light path 224 respectively. The two mirrors 227 and 228 are connected with the other end of the fourth transmission light path 223 and the other end of the fifth transmission light path 224 respectively. Figure 29

[0127] In some embodiments, the two mirrors 227 and 228 can be polarization state rotating mirrors.

[0128] In one embodiment, when the polarization beam splitter 221 comprises three ports, the input port G can also serve as the output port of the polarization conversion and time phase encoding unit 130, for outputting the polarization conversion and time phase encoded light pulse. At this time, the polarization conversion and time phase encoding unit 130 further comprises a light coupling unit arranged in front of the polarization beam splitter 221. The light coupling unit can be a light coupler or a light circulator.

[0129] In another embodiment, when the two mirrors 227 and 228 are polarization state rotating mirrors, for example, the two mirrors 227 and 228 are quarter-wave plate mirrors or 90° Faraday rotating mirrors, the polarization beam splitter 221 can further comprise a fourth port G' (not shown in the figure). The fourth port G' of the polarization beam splitter 221 is the output port of the polarization conversion and time phase encoding unit 130.

[0130] In some embodiments, as shown, Figure 30 ​​As shown, the fifth light coupling unit and the sixth light coupling unit are the same light coupler 221, the polarization conversion time phase encoding unit 130 further comprises two mirrors 227, 228 and two polarizers 225, 226, two output ports I, H of the light coupler 221 are connected with one end of the fourth transmission light path 223 and one end of the fifth transmission light path 224 respectively, the two mirrors 227, 228 are connected with the other end of the fourth transmission light path 223 and the other end of the fifth transmission light path 224 respectively; the two polarizers 225, 226 are arranged on the fourth transmission light path 223 and the fifth transmission light path 224 respectively, and the polarization directions of the polarizer 225 and the polarizer 226 are orthogonal to each other.

[0131] In some embodiments, when the light coupler 221 comprises three ports, the input port G can also be used as an output port of the polarization conversion time phase encoding unit 130, for outputting the polarization conversion time phase encoded light pulse; at this time, the polarization conversion time phase encoding unit 130 further comprises a light coupling unit arranged in front of the light coupler 221, and the light coupling unit can be a light coupler or a light circulator.

[0132] In yet some embodiments, the light coupler 221 can further comprise a fourth port G' (not shown in the figure); the fourth port G' of the light coupler 221 is an output port of the polarization conversion time phase encoding unit 130.

[0133] In some embodiments, referring to any one of the accompanying drawings, Figures 24-30 In some embodiments, referring to any one of the accompanying drawings,

[0134] In any one of the above embodiments, the quantum state encoding device of the present application further comprises a quarter-wave plate and / or a polarization state rotator arranged between the polarization encoding unit 110 and the polarization conversion time phase encoding unit 130, and the polarization state rotator is a half-wave plate or a Faraday rotator.

[0135] In some embodiments, according to the requirements of quantum communication, the quantum state encoding device of the present application can also be used to realize a quantum state decoding process.

[0136] According to another aspect of the present application, a quantum state encoding method is provided, which is applied to the above quantum state encoding device.

[0137] According to yet another aspect of the present application, a software-defined quantum communication system is provided, Figure 31 Fig. 4 shows a structure schematic diagram of a software-defined quantum communication system provided by an embodiment of the present application, and Figure 31As shown, the software-defined quantum communication system can include the quantum state encoding device 3101 and the encoding control device 3102 described above; the encoding control device 3102 is used to generate quantum communication encoding control instructions based on the encoding requirements of the quantum communication system, and send them to the quantum state encoding device 3101.

[0138] The quantum communication system can be a discrete variable quantum communication system or a continuous variable quantum communication system, including a BB84 protocol, a reference frame independent protocol, an MDI protocol, a TF protocol, and the like.

[0139] It should be understood that the specific features, operations and details described above with respect to the device of the present application can also be similarly applied to the method and system of the present application, or vice versa. In addition, each step of the method of the present application can be performed by the corresponding components or units of the device or system of the present application.

[0140] The technical features described above can be combined arbitrarily. Although all possible combinations of these technical features are not described, any combination of these technical features should be considered to be covered by the present specification, as long as there is no contradiction in such combination.

[0141] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand: they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A quantum state encoding device, characterized by, The polarization encoding unit, the first optical coupling unit, the polarization-to-time phase encoding unit, the first transmission optical path, and the second optical coupling unit are included. The polarization encoding unit comprises at least one adjustable circular birefringence module, and the adjustable circular birefringence module comprises a first quarter-wave plate, N built-in linear polarization operation modules, and a second quarter-wave plate connected in series. The first quarter-wave plate is used to convert left-handed circular polarization components and right-handed circular polarization components in an input light pulse into two orthogonal linear polarization components. The built-in linear polarization operation module comprises a linear polarization control optical path and at least one phase modulator. The second quarter-wave plate is connected to the output end of the linear polarization control optical path, and is used to convert the two orthogonal linear polarization components in the light pulse output by the linear polarization control optical path into left-handed circular polarization components and right-handed circular polarization components. The first optical coupling unit comprises one input port and two output ports, namely a first port, a second port, and a third port. The second optical coupling unit comprises two input ports and one output port, namely a fourth port, a fifth port, and a sixth port. The polarization-to-time phase encoding unit comprises one input port and one output port, and is used to perform time-phase encoding conversion on the light pulse of the polarization-encoded quantum state input. The third port of the first optical coupling unit is connected to the input port of the polarization-to-time phase encoding unit, and the output port of the polarization-to-time phase encoding unit is connected to the fifth port of the second optical coupling unit, forming a first optical 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 optical path, forming a second optical output branch. The first optical coupling unit is used to input the light pulse of the polarization-encoded quantum state output by the polarization encoding unit into the first optical output branch and / or the second optical output branch according to a quantum communication encoding control instruction. The sixth port of the second optical coupling unit is an output port of the quantum state encoding device, and is used to output the light pulse of the polarization-encoded quantum state transmitted by the second optical output branch or the light pulse of the time-phase encoded quantum state output by the first optical output branch according to the quantum communication encoding control instruction. The first optical coupling unit is an optical coupler, and the second optical coupling unit is an optical switch.

2. The apparatus of claim 1, wherein, ​ 3. The apparatus of claim 2, wherein, The first optical coupling unit is configured to input the polarized quantum state light pulse output by the polarization encoding unit through the first port, split the polarized quantum state light pulse into two sub light pulses, and input the two sub light pulses into the first optical output branch and the second optical output branch through the third port and the second port respectively. The second optical coupling unit is configured to output the polarized quantum state light pulse transmitted by the second optical output branch or the time-phase encoded quantum state light pulse output by the first optical output branch according to the quantum communication encoding 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 configured to input the polarized quantum state light pulse into the first optical output branch or the second optical output branch according to the quantum communication encoding control instruction. When the second optical coupling unit is an optical switch, the second optical coupling unit is configured to connect the first optical output branch outputting the time-phase encoded quantum state light pulse or the second optical output branch outputting the polarized quantum state light pulse according to the quantum communication encoding control instruction. When the second optical coupling unit is an optical coupler, the second optical coupling unit is configured to output the time-phase encoded quantum state light pulse output by the first optical output branch or the polarized quantum state light pulse transmitted by the second optical output branch.

6. The apparatus of claim 1, wherein, The linear polarization control optical path 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 and the fourth optical coupling unit are connected through the second transmission optical path and the third transmission optical path; and the phase modulator is arranged on the second transmission optical path or the third transmission optical path. The third optical coupling unit is configured to receive the light pulse containing the two orthogonal linear polarization components converted by the first quarter-wave plate, split the light pulse into two sub light pulses, i.e., a first sub light pulse and a second sub light pulse, and transmit the first sub light pulse and the second sub light pulse along the second transmission optical path and the third transmission optical path in the linear polarization control optical path respectively. The phase modulator is configured to perform phase modulation on at least one of the first sub light pulse and the second sub light pulse, so as to generate a phase difference between the two sub light pulses. The fourth optical coupling unit is configured to receive the two sub light pulses with the phase difference, and combine the two sub light pulses into one light pulse for output.

7. The apparatus of claim 1 or 6, wherein one of the two eigenpolarizations of the first quarter-wave plate one of the two eigenpolarizations of the linear polarization control optical path is 45° ± n-90°; one of the two eigenpolarization states of the second quarter-wave plate one of the two eigenpolarization states of the linear polarization control optical path is 45°±m·90°, wherein n and m are integers.

8. The apparatus of claim 6, wherein The third optical coupling unit is a polarization beam splitter, the fourth optical coupling unit is a polarization beam combiner, and an intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the linear polarization control optical path.

9. The apparatus of claim 6, wherein The third optical coupling unit is a polarization beam splitter, the fourth optical coupling unit is an optical coupler, and an intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the linear polarization control optical path.

10. The apparatus of claim 6, wherein, the third optical coupling unit is an optical coupler, and the fourth optical coupling unit is a polarization beam combiner, and an eigenpolarization state of the polarization beam combiner is an eigenpolarization state of the linear polarization control optical path.

11. The apparatus of claim 6, wherein, the third optical coupling unit and the fourth optical coupling unit are a same polarization beam splitter, and the linear polarization control optical path further comprises: two mirrors, the two mirrors are connected with the second transmission optical path and the third transmission optical path respectively, and are configured to reflect light pulses input into the two mirrors back to the polarization beam splitter, and an eigenpolarization state of the polarization beam splitter is an eigenpolarization state of the linear polarization control optical path.

12. The apparatus of claim 11, wherein, the two mirrors are polarization state rotating mirrors.

13. The apparatus of claim 6, wherein, the third optical coupling unit and the fourth optical coupling unit are a same polarization beam splitting unit, the second transmission optical path and the third transmission optical path are a same transmission optical path, and an eigenpolarization state of the polarization beam splitting unit is an eigenpolarization state of the linear polarization control optical path.

14. The apparatus of claim 13, wherein, the polarization beam splitting unit is a polarization beam splitter, and the polarization beam splitter comprises three ports, i.e., a first port, a second port and a third port, the first port of the polarization beam splitter is an input and output port of the linear polarization control optical path, the second port and the third port of the polarization beam splitter are connected through the same transmission optical path, and an eigenpolarization state of the polarization beam splitter is an eigenpolarization state of the polarization beam splitting unit.

15. The apparatus of claim 13, wherein, the polarization beam splitting unit comprises: a polarization beam splitter, a first polarizer and a second polarizer; the polarization beam splitter comprises four ports, i.e., a first port, a second port, a third port and a fourth port, the first port of the polarization beam splitter is an input port of the linear polarization control optical path, the fourth port of the polarization beam splitter is an output port of the linear polarization control optical path, the second port and the third port of the polarization beam splitter are connected with a port on a first side of the first polarizer and a port on a first side of the second polarizer respectively, a port on a second side of the first polarizer and a port on a second side of the second polarizer are connected through the transmission optical path, an angle between a polarization direction of the first polarizer and an eigenpolarization state of the polarization beam splitter is θ, an angle between a polarization direction of the second polarizer and another eigenpolarization state of the polarization beam splitter is δ, and θ, δ ≠ n·90°, n is an integer, and an eigenpolarization state of the polarization beam splitter is an eigenpolarization state of the polarization beam splitting unit.

16. The apparatus of claim 13, wherein, the polarization beam splitting unit comprises: an optical beam splitter, a first polarizer and a second polarizer; The optical beam splitter comprises at least three ports, respectively a first port, a second port and a third port, the first port of the optical beam splitter is the input port of the linear polarization control optical path; the second port and the third port of the optical beam splitter are connected with the port of the first side of the first polarizer and the port of the first side of the second polarizer respectively; the port of the second side of the first polarizer and the port of the second side of the second polarizer are connected through the transmission optical path; the polarization direction of the first polarizer is The polarization direction of the second polarizer is The polarization direction a of the first polarizer and the polarization direction of the second polarizer are Orthogonal to each other; the polarization direction of the first polarizer And the polarization direction of the second polarizer Is the eigenpolarization state of the polarization beam splitting unit.

17. The apparatus of claim 16, wherein, the optical beam splitter further comprises a fourth port. The fourth port of the optical splitter is an output port of the linear polarization control optical path.

18. The apparatus of claim 14 or 16, wherein, The first quarter-wave plate and the second quarter-wave plate are the same device.

19. The apparatus of claim 18, wherein, The polarization encoding unit further comprises an optical coupling unit. The optical coupling unit is an optical coupler or an optical circulator, and the optical coupling unit is disposed before the first quarter-wave plate and connected to the first quarter-wave plate.

20. The apparatus of claim 14 or 16, wherein, The polarization encoding unit further comprises an optical coupling unit. The optical coupling unit is an optical coupler or an optical circulator, and the optical coupling unit is disposed between the first quarter-wave plate and the polarization splitting unit.

21. The apparatus of any one of claims 13 to 17, wherein, The transmission optical path is a free-space optical path or a polarization-maintaining optical fiber.

22. The apparatus of claim 21, wherein, The polarization encoding unit further comprises a half-wave plate or a 90-degree Faraday rotator disposed in the transmission optical path.

23. The apparatus of any one of claims 13 to 17, wherein, The phase modulator is disposed on the transmission optical path; the phase modulator comprises a first port and a second port, which are a forward input light port and a reverse input light port, respectively; the phase modulator modulates the light pulses input from one of the first port and the second port, or performs different phase modulation on the light pulses input from the first port and the second port.

24. The apparatus of claim 23, wherein, The transmission optical path is coupled with the slow axis of the first port and the second port of the phase modulator, or is coupled with the fast axis of the first port and the second port of the phase modulator.

25. The apparatus of claim 23, wherein, When a high-frequency modulation electrical signal with a frequency higher than a specified threshold is applied to the phase modulator, the phase modulator works in a non-reciprocal state, and a ratio of a modulation efficiency of a first sub-light pulse input from the forward input light port to a modulation efficiency of a second sub-light pulse input from the reverse input light port is not less than a preset threshold.

26. The apparatus of claim 1, wherein, When N is 2, two built-in linear polarization operation modules are disposed in series between the first quarter-wave plate and the second quarter-wave plate.

27. The device of claim 1, wherein, The polarization encoding unit further comprises: M external linear polarization operation modules, which are connected in series with the adjustable circular birefringence module, and M is an integer greater than or equal to 1.

28. The apparatus of claim 27, wherein, When M is 2, the two external linear polarization operation modules are connected in series and are both disposed before the first quarter-wave plate, or are both disposed after the second quarter-wave plate, or one external linear polarization operation module is disposed before the first quarter-wave plate and the other external linear polarization operation module is disposed after the second quarter-wave plate.

29. The apparatus of claim 27, wherein, When M is 2, an included angle between the eigenpolarizations of the two external linear polarization operation modules is n·22.5°, where n is an integer.

30. The apparatus of claim 29, wherein, The angle between the intrinsic polarization states of the two external linear polarization operation modules is adjusted by rotating at least one of the two external linear polarization operation modules; and / or The polarization encoding unit further comprises a polarization state rotator arranged between the two external linear polarization operation modules, and the angle between the intrinsic polarization states of the two external linear polarization operation modules is adjusted by the polarization state rotator; and / or The polarization encoding unit further comprises two polarization state rotators arranged at the front end and the rear end of one of the two external linear polarization operation modules, and the angle between the intrinsic polarization states of the two external linear polarization operation modules is adjusted by the two polarization state rotators.

31. The device of claim 1 or 27, wherein, The polarization encoding unit comprises two series-connected adjustable circular birefringence modules.

32. The apparatus of claim 1, wherein, When N is greater than 1, the polarization encoding unit further comprises N-1 optical isolation units, which are optical isolators or optical circulators, and the N-1 optical isolation units are arranged between any two adjacent internal linear polarization operation modules.

33. The apparatus of claim 27, wherein, When N is greater than 1 and / or M is greater than 1, the polarization encoding unit further comprises N+M-1 optical isolation units, which are optical isolators or optical circulators, and the N+M-1 optical isolation units are arranged between any two adjacent linear polarization operation modules.

34. The device of claim 1, wherein, The polarization-to-time phase encoding unit comprises a fifth optical coupling unit, a sixth optical coupling unit, a fourth transmission optical path, and a fifth transmission optical path, The fifth optical coupling unit comprises at least three ports, one input port and two output ports; the sixth optical coupling unit comprises at least three ports, two input ports and one output port, the two output ports of the fifth optical coupling unit are connected with the two input ports of the sixth optical coupling unit through the fourth transmission optical path and the fifth transmission optical path; and the optical path lengths of the fourth transmission optical path and the fifth transmission optical path are not equal.

35. The apparatus of claim 34, wherein, The fifth optical coupling unit is a polarization beam splitter, and the sixth optical coupling unit is a polarization beam combiner.

36. The apparatus of claim 34, wherein, The fifth optical coupling unit is a polarization beam splitter, and the sixth optical coupling unit is an optical coupler.

37. The apparatus of claim 34, wherein, The fifth optical coupling unit is an optical coupler, and the sixth optical coupling unit is a polarization beam combiner.

38. The apparatus of claim 34, wherein, The fifth optical coupling unit is an optical coupler, and the sixth optical coupling unit is an optical coupler, and the polarization-to-time phase encoding unit further comprises two polarizers, The two polarizers are arranged on the fourth transmission optical path and the fifth transmission optical path respectively, and the polarization directions of the two polarizers are orthogonal to each other.

39. The device of claim 34, wherein, The fifth optical coupling unit and the sixth optical coupling unit are the same polarization beam splitter, and the polarization-to-time phase encoding unit further comprises two mirrors, The two output ports of the polarization beam splitter are connected with one end of the fourth transmission optical path and one end of the fifth transmission optical path respectively, and the two mirrors are connected with the other end of the fourth transmission optical path and the other end of the fifth transmission optical path respectively.

40. The device of claim 39, wherein, The two mirrors are polarization state rotating mirrors.

41. The apparatus of claim 34, wherein, The fifth light coupling unit and the sixth light coupling unit are the same light coupler, and the polarization conversion and time phase encoding unit further comprises two mirrors and two polarizers, The two output ports of the light coupler are connected with one end of the fourth transmission light path and one end of the fifth transmission light path respectively, and the two mirrors are connected with the other end of the fourth transmission light path and the other end of the fifth transmission light path respectively; the two polarizers are arranged on the fourth transmission light path and the fifth transmission light path respectively, and the polarization directions of the two polarizers are orthogonal to each other.

42. The apparatus of claim 36 or 38, wherein, The fourth transmission light path or the fifth transmission light path is a 90° twisted polarization maintaining optical fiber, or The polarization conversion and time phase encoding unit further comprises a 90° polarization state rotator, The 90° polarization state rotator is arranged on the fourth transmission light path or the fifth transmission light path, and is used for rotating the polarization state of the passing sub-light pulse by 90°.

43. The apparatus of any one of claims 34-41, wherein, The polarization conversion and time phase encoding unit further comprises a polarizer. The polarizer is arranged at the output port of the polarization conversion and time phase encoding unit, and is used for polarizing the output light pulse.

44. The device of claim 1 or 27, wherein, The device further comprises a quarter-wave plate and / or a polarization state rotator arranged between the polarization encoding unit and the polarization conversion and time phase encoding unit.

45. A method of encoding a quantum state, the method comprising: The quantum state encoding device of any one of claims 1-44 is applied.

46. A software-defined quantum communication system, comprising: The quantum state encoding device of any one of claims 1-44 and an encoding control device are included. The encoding control device is used for generating quantum communication encoding control instructions based on the encoding requirements of a quantum communication system, and sending the quantum state encoding device.

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