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

Abstract

The present disclosure provides a quantum state encoding apparatus and method, and a software-defined quantum communication system. The apparatus comprises a polarization encoding unit, a first optical coupling unit, a polarization-to-time-bin phase encoding unit, a first optical transmission path, and a second optical coupling unit; the polarization encoding unit is configured for modulating an input optical pulse by means of at least one tunable circular birefringence module and then outputting a polarization-encoded quantum-state optical pulse; the polarization-to-time-bin phase encoding unit is configured for converting the polarization-encoded quantum-state optical pulse output by the polarization encoding unit into a time-bin phase-encoded quantum-state optical pulse; and 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 optical pulse or output the time-bin phase-encoded quantum-state optical pulse. The present disclosure enables a single quantum state encoding apparatus to satisfy different encoding requirements of quantum communication systems.

Description

Quantum state encoding devices, methods, and software-defined quantum communication systems Technical Field

[0001] This disclosure relates to the fields of quantum communication and optical quantum coding technology, and in particular to a quantum state coding 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, commonly used quantum communication encoding methods include polarization encoding and time-phase encoding. A typical quantum communication system chooses only one encoding method, thus the system lacks versatility and cannot be flexibly networked.

[0004] How to achieve universal quantum state encoding that is compatible with the encoding methods of multiple quantum communication systems in an optical quantum encoding device is an important issue for quantum communication applications.

[0005] Summary of the Invention

[0006] In view of this, the present disclosure provides a quantum state encoding device, method and quantum communication system to solve the technical problems raised in the background art.

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

[0008] The polarization encoding unit includes at least one adjustable circular birefringence module, which includes a first quarter-wave plate, N built-in linear polarization operation modules, and a second quarter-wave plate connected in series; N is an integer greater than or equal to 1.

[0009] The first quarter-wave plate 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.

[0010] The built-in linear polarization operation module includes a linear polarization control optical path and at least one phase modulator; the input end of the linear polarization control optical path is connected to one end of the first quarter-wave plate, and is used to receive the light pulse containing the two orthogonal linear polarization components after being converted by the first quarter-wave plate, and split it into two sub-light pulses. The phase modulator 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 with the phase difference and outputs them through the output end.

[0011] One end of 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 one optical pulse output by the linear polarization control optical path into left-hand circular polarization components and right-hand circular polarization components, and then output them through the output end.

[0012] The first optical coupling unit includes one input port and two output ports, namely the first port, the second port and the third port, and the first port is connected to the output end of the second quarter-wave plate in the polarization coding unit;

[0013] The second optical coupling unit includes two input ports and one output port, namely the fourth port, the fifth port, and the sixth port;

[0014] The polarization-to-time-phase encoding unit includes an input port and an output port, used to perform time-phase encoding conversion on the input polarization-encoded quantum state light pulse and output the time-phase encoded quantum state light pulse;

[0015] 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 the first optical output branch;

[0016] 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;

[0017] The first optical coupling unit is used to input the light pulse of the polarization-coded quantum state output by the polarization coding unit into the first optical output branch and / or the second optical output branch according to the quantum communication coding control command. The quantum communication coding control command is determined according to the coding requirements of the quantum communication system.

[0018] The sixth port of the second optical coupling unit is the output port of the quantum state encoding device, which is used to output the optical pulse of the polarization-encoded quantum state transmitted by the second optical output branch or the optical pulse of the time-phase-encoded quantum state output by the first optical output branch according to the quantum communication encoding control command.

[0019] According to a second aspect of this disclosure, a quantum state encoding method is provided, which is applied to the quantum state encoding device described above.

[0020] According to a third aspect of this disclosure, a software-defined quantum communication system is provided, including the quantum state encoding device and the encoding control device as described above;

[0021] The encoding control device 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.

[0022] In summary, the quantum state encoding device, method, and software-defined quantum communication system provided in this disclosure have at least the following beneficial effects:

[0023] This disclosure allows for the control of outputting light pulses with polarization-encoded quantum states or time-phase-encoded quantum states according to quantum communication encoding control instructions. This enables the same quantum state encoding device to meet the different encoding requirements of quantum communication systems, thereby achieving the encoded output of multi-mode quantum state light pulses and satisfying the encoding requirements of quantum communication systems.

[0024] This disclosure also achieves the security requirements of quantum communication, reduces the number of lasers used, and reduces the weight and power consumption of quantum communication transmitters. The polarization-encoded quantum states disclosed in this disclosure have strong stability and can meet the requirements of space quantum communication applications for time-phase-encoded quantum states. Attached Figure Description

[0025] 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.

[0026] Figure 1 shows a schematic diagram of the structure of a first embodiment of a quantum state encoding device provided in this disclosure;

[0027] Figure 2 shows a schematic diagram of the structure of a first embodiment of the polarization coding unit provided in this disclosure;

[0028] Figure 3 shows a schematic diagram of a second embodiment of a quantum state encoding device provided in this disclosure;

[0029] Figure 4 shows a schematic diagram of the structure of a first embodiment of the linear polarization operation module provided in this disclosure;

[0030] Figure 5 shows a schematic diagram of the structure of a second embodiment of the linear polarization operation module provided in this disclosure;

[0031] Figure 6 shows a schematic diagram of the structure of a third embodiment of the linear polarization operation module provided in this disclosure;

[0032] Figure 7 shows a schematic diagram of the structure of the fourth embodiment of the linear polarization operation module provided in this disclosure;

[0033] Figure 8 shows a schematic diagram of the structure of the fifth embodiment of the linear polarization operation module provided in this disclosure;

[0034] Figure 9 shows a schematic diagram of the structure of the sixth embodiment of the linear polarization operation module provided in this disclosure;

[0035] Figure 10 shows a schematic diagram of the structure of the seventh embodiment of the linear polarization operation module provided in this disclosure;

[0036] Figure 11 shows a schematic diagram of the structure of the eighth embodiment of the linear polarization operation module provided in this disclosure;

[0037] Figure 12 shows a schematic diagram of the structure of a second embodiment of the polarization coding unit provided in this disclosure;

[0038] Figure 13 shows a schematic diagram of the structure of a third embodiment of the polarization coding unit provided in this disclosure;

[0039] Figure 14 shows a schematic diagram of the structure of the fourth embodiment of the polarization coding unit provided in this disclosure;

[0040] Figure 15 shows a schematic diagram of the structure of the fifth embodiment of the polarization coding unit provided in this disclosure;

[0041] Figure 16 shows a schematic diagram of the structure of the sixth embodiment of the polarization coding unit provided in this disclosure;

[0042] Figure 17 shows a schematic diagram of the structure of the seventh embodiment of the polarization coding unit provided in this disclosure;

[0043] Figure 18 shows a schematic diagram of the structure of the eighth embodiment of the polarization coding unit provided in this disclosure;

[0044] Figure 19 shows a schematic diagram of the structure of the ninth embodiment of the polarization coding unit provided in this disclosure;

[0045] Figure 20 shows a schematic diagram of the structure of the tenth embodiment of the polarization coding unit provided in this disclosure;

[0046] Figure 21 shows a schematic diagram of the structure of the eleventh embodiment of the polarization coding unit provided in this disclosure;

[0047] Figure 22 shows a schematic diagram of the structure of the twelfth embodiment of the polarization coding unit provided in this disclosure;

[0048] Figure 23 shows a schematic diagram of the structure of the thirteenth embodiment of the polarization coding unit provided in this disclosure;

[0049] Figure 24 shows a schematic diagram of the structure of a first embodiment of the polarization-to-time phase encoding unit provided in this disclosure;

[0050] Figure 25 shows a schematic diagram of the structure of a second embodiment of the polarization-to-time phase encoding unit provided in this disclosure;

[0051] Figure 26 shows a schematic diagram of the structure of a third embodiment of the polarization-to-time phase encoding unit provided in this disclosure;

[0052] Figure 27 shows a schematic diagram of the structure of a fourth embodiment of the polarization-to-time phase encoding unit provided in this disclosure;

[0053] Figure 28 shows a schematic diagram of the structure of a fifth embodiment of the polarization-to-time phase encoding unit provided in this disclosure;

[0054] Figure 29 shows a schematic diagram of the structure of a sixth embodiment of the polarization-to-time phase encoding unit provided in this disclosure;

[0055] Figure 30 shows a schematic diagram of the structure of the seventh embodiment of the polarization-to-time phase encoding unit provided in this disclosure;

[0056] Figure 31 shows a schematic diagram of the structure of a software-defined quantum communication system provided in an embodiment of this disclosure. Detailed Implementation

[0057] 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.

[0058] 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.

[0059] It should be noted that the time phase encoding described in 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.

[0060] This disclosure provides a quantum state encoding device. Referring to Figure 1, which is a schematic diagram of the structure of a first embodiment of the quantum state encoding device provided in this disclosure, 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.

[0061] In one embodiment, as shown in FIG2, 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. FIG2 shows only an embodiment containing one adjustable circular birefringence module, and this adjustable circular birefringence module contains only one built-in linear polarization operation module 112.

[0062] 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.

[0063] In some embodiments, referring again to Figure 2, 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 with the phase difference and outputs them through the output end.

[0064] In some embodiments, referring again to Figure 2, one end of the second quarter-wave plate 113 is connected to the output end of the linear polarization control optical path 114, and is used to convert the two orthogonal linear polarization components in one optical pulse output by the linear polarization control optical path 114 into a left-hand circular polarization component and a right-hand circular polarization component, and then output them through the output end.

[0065] In some embodiments, as shown in FIG3, the first optical coupling unit 120 includes an input port and two output ports, namely a first port L, a second port M and a third port N, and the first port L is connected to the output terminal O of the second quarter-wave plate 113 in the polarization coding unit 110.

[0066] In some embodiments, as shown in FIG3, the second optical coupling unit 150 includes two input ports and one output port, namely the fourth port M', the fifth port N', and the sixth port L'.

[0067] In some embodiments, as shown in FIG3, the polarization-to-time-phase encoding unit 130 includes an input port P and an output port Q, used to perform time-phase encoding conversion on the input polarization-encoded quantum state light pulse and output the time-phase-encoded quantum state light pulse.

[0068] In some embodiments, as shown in FIG3, 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 optical output branch.

[0069] In some embodiments, as shown in FIG3, 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 to form a second optical output branch.

[0070] In some embodiments, as shown in FIG3, the first optical coupling unit 120 is used to input the light pulse of the polarization-coded quantum state output by the polarization coding unit 110 into the first optical output branch and / or the second optical output branch according to the quantum communication coding control command. The quantum communication coding control command is determined according to the coding requirements of the quantum communication system.

[0071] In some embodiments, as shown in FIG3, the sixth port L' of the second optical coupling unit 150 is the output port of the quantum state encoding device, which is used to output the optical pulse of the polarization-encoded quantum state transmitted by the second optical output branch or the optical pulse of the time-phase-encoded quantum state output by the first optical output branch according to the quantum communication encoding control command.

[0072] This disclosure allows for the control and output of optical pulses in polarization-encoded quantum states or time-phase-encoded quantum states according to quantum communication encoding control commands. This enables the same quantum state encoding device to meet the different encoding requirements of quantum communication systems, achieving the encoded output of multi-mode quantum state optical pulses and fulfilling the encoding needs of quantum communication systems. This disclosure also meets quantum communication security requirements, reduces the number of lasers used, and lightens the weight and power consumption of quantum communication transmitters. The polarization-encoded quantum states of this disclosure exhibit strong stability, meeting the requirements of space quantum communication applications for both polarization-encoded and time-phase-encoded quantum states.

[0073] 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 in FIG3, the first optical coupling unit 120 is used to input the optical pulse of the polarization-coded quantum state output by the polarization coding unit 110 through the first port L. The first optical coupling unit 120 splits the optical pulse of the polarization-coded quantum state into two sub-optical pulses, and inputs the two sub-optical pulses 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 used to select, according to the quantum communication coding control command, to output the optical pulse of the polarization-coded quantum state transmitted by the second optical output branch or the optical pulse of the time-phase-coded quantum state output by the first optical output branch.

[0074] 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 used to selectively input a light pulse of a polarization-coded quantum state to either the first optical output branch or the second optical output branch, according to the quantum communication encoding control command. When the second optical coupling unit 150 is an optical switch, it is used to connect either the first optical output branch that outputs a light pulse of a time-phase-coded quantum state or the second optical output branch that outputs a light pulse of a polarization-coded quantum state, according to the quantum communication encoding control command.

[0075] In other embodiments, when the second optical coupling unit 150 is an optical coupler, the second optical coupling unit 150 is used to output the optical pulse of the time phase-coded quantum state output by the first optical output branch or the optical pulse of the polarization-coded quantum state transmitted by the second optical output branch.

[0076] In some embodiments, referring to Figure 4, 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 122 is disposed on the second transmission optical path 125 or the third transmission optical path 126.

[0077] In some embodiments, the third optical coupling unit 124 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.

[0078] In some embodiments, the phase modulator 122 is used to perform phase modulation on at least one of the first sub-optical pulse and the second sub-optical pulse to generate a phase difference between the two sub-optical pulses; the fourth optical coupling unit 124 is used to receive the two sub-optical pulses that generate a phase difference and combine them into a single optical pulse for output.

[0079] 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 eigenpolarization 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.

[0080] In some embodiments, as shown in FIG5, 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.

[0081] In some embodiments, as shown in FIG6, the third optical coupling unit 123 is a polarization beam splitter, the fourth optical coupling unit 124 is an optical coupler, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the linear polarization control optical path 114.

[0082] In some embodiments, as shown in FIG7, the third optical coupling unit 123 is an optical coupler, and the fourth optical coupling unit 124 is a polarization combiner. The intrinsic polarization state of the polarization combiner is the intrinsic polarization state of the linear polarization control optical path 114.

[0083] In some embodiments, as shown in FIG8, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter 123. The linear polarization control optical path 114 further includes two mirrors 211 and 212, which are connected to the second transmission optical path 125 and the third transmission optical path 126 respectively, for reflecting the light pulses input to the mirrors 211 and 212 back to the polarization beam splitter 123. The intrinsic polarization state of the polarization beam splitter 123 is the intrinsic polarization state of the linear polarization control optical path 114.

[0084] In some embodiments, the polarization beam splitter 123 may include at least three ports, including at least one input port and two output ports, namely port A, port B, and port C. Port B and port C are connected to two reflectors via a third transmission optical path 126 and a second transmission optical path 125, respectively. Port A serves as the input port for receiving optical pulses from the input linear polarization control optical path 123. Specifically, as shown in FIG8, port B is connected to reflector 212 via the third transmission optical path 126, and port C is connected to reflector 211 via the second transmission optical path 125.

[0085] In one embodiment, when the polarization beam splitter 123 includes three ports, the input port A can also serve as the output port of the linear polarization control optical path 114, for outputting light pulses modulated by the linear birefringence of the linear polarization control optical path 114. In this embodiment, the polarization encoding unit 110 further 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 123. 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 123, 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 an 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.

[0086] In another embodiment, as shown in FIG8, the polarization beam splitter 123 may further include an output port D, which serves as the output port of the linear polarization control optical path 114 for outputting light pulses modulated by the linear birefringence of the linear polarization control optical path 114.

[0087] In some embodiments, reflectors 211 and 212 can be polarization state rotating reflectors, which rotate the polarization state of the reflected sub-light pulse by a certain angle compared to the polarization state of the sub-light pulse before reflection, such as a 90° polarization state rotating reflector. Reflectors 211 and 212 can be quarter-wave plate reflectors or 90° Faraday rotating reflectors.

[0088] It should be noted that when reflectors 211 and 212 do not rotate the polarization state of the input sub-light pulse, the polarization beam splitter 123 only outputs the combined light pulse from port A. When reflectors 211 and 212 rotate the polarization state of the input sub-light pulse by any angle (other than 0° and 90°), the polarization beam splitter 123 can output the combined light pulse from either port A or port D. Specifically, if the polarization state of the sub-light pulse is rotated by 90°, the combined light pulse can only be output from port D. When the polarization state is rotated by 90°, reflectors 211 and 212 become 90° polarization state rotating reflectors, which can be quarter-wave plate reflectors or 90° Faraday rotating reflectors.

[0089] In some embodiments, as shown in FIG9, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter unit 201, the second transmission optical path and the third transmission optical path are the same transmission optical path 205, and the intrinsic polarization state of the polarization beam splitter unit 201 is the intrinsic polarization state of the linear polarization control optical path 114.

[0090] In some embodiments, as shown in FIG9, the polarization beam splitter unit 201 is a polarization beam splitter, which includes three ports, namely a first port A, a second port B and a third port C. The first port A of the polarization beam splitter is the input and output port of the linear polarization control optical path 114. The second port B and the third port C of the polarization beam splitter are connected through the same transmission optical path 205. The intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the polarization beam splitter unit 201.

[0091] 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.

[0092] In some embodiments, as shown in FIG10, 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 includes four ports, namely a first port A, a second port B, a third port C, and a fourth port D, wherein 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 D of the polarization beam splitter 201... C is connected to 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 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.

[0093] In some embodiments, as shown in FIG11, the polarization beam splitting unit includes: an optical beam splitter 201, a first polarizer 206, and a second polarizer 207; the optical beam splitter 201 includes at least three ports, namely a first port A, a second port B, and a third port C, wherein the first port A of the optical beam splitter 201 is the input port of the linear polarization control optical path 114; the second port B and the third port C of the optical beam splitter 201 are respectively connected to the first side ports of the first polarizer 206 and the first side ports of the second polarizer 207; the second side ports of the first polarizer 206 and the second side ports of the second polarizer 207 are connected through a transmission optical path 205. The polarization direction of the first polarizer 206 is... The polarization direction of the second polarizer 207 is The direction of the first polarizer 206 The polarization direction of the second polarizer 207 Mutually orthogonal; the polarization direction of the first polarizer 206 The polarization direction of the second polarizer 207 This represents the intrinsic polarization state of the polarization beam splitter unit.

[0094] In the above embodiments, when the input and output of the linear polarization control optical path 114 are at the same port, the polarization encoding unit 110 further 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 optical beam splitter 201. 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 optical beam splitter 201, 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.

[0095] In some other embodiments, the optical beam splitter 201 also includes a fourth port D (not shown in the figure); the fourth port D of the optical beam splitter 201 is the output port of the linear polarization control optical path 114.

[0096] In some embodiments shown in Figures 9-11, the transmission optical path 205 is a free-space optical path or a polarization-maintaining fiber.

[0097] Referring to any of the figures in Figures 9-11, 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.

[0098] 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.

[0099] In some embodiments, referring to any of the figures in Figures 9-11, 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.

[0100] In some embodiments, referring to any of the figures in Figures 9-11, the polarization encoding unit 110 of this disclosure further includes a polarization state rotator disposed in the transmission optical path 205, the polarization state rotator being a half-wave plate or a 90-degree Faraday rotator.

[0101] In some embodiments, when the input and output of the linear polarization control optical path 114 are at the same port, referring to Figure 12, 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 before the first quarter-wave plate 111, and the optical coupling unit 117 is connected to the first quarter-wave plate 111.

[0102] In the above embodiments, referring again to Figure 12, 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., the first quarter-wave plate 111 in Figure 12). In this case, by placing the optical coupling unit 117 before the first quarter-wave plate 111, the input and output functions of the first quarter-wave plate 111 can be separated. The optical coupling unit 117 is an optical coupler or an optical circulator.

[0103] In some other embodiments, referring to Figure 13, 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.

[0104] In some embodiments, referring to Figure 14, 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.

[0105] In some embodiments, referring to Figure 15, the polarization encoding unit 110 of this disclosure further includes M external linear polarization operation modules, such as the second linear polarization operation module 116 in Figure 15. The external linear polarization operation modules are connected in series with the adjustable circular birefringence module, where M is an integer greater than or equal to 1. The adjustable circular birefringence module structure in Figure 15 is exemplified by the structure shown in Figure 2. Figure 15 shows the structure of the polarization encoding unit 110 including one external linear polarization operation module.

[0106] It should be noted that the external linear polarization operation module and the internal linear polarization operation module 112 described in this embodiment have the same structure and function. In this embodiment, the linear polarization operation module disposed within the adjustable circular birefringence module is referred to as the internal linear polarization operation module, as shown in the first linear polarization operation module 112 in Figure 15; the linear polarization operation module disposed outside the adjustable circular birefringence module and connected in series with the adjustable circular birefringence module is referred to as the external linear polarization operation module, as shown in the second linear polarization operation module 116 in Figure 15. Referring to Figure 15, the second linear polarization operation module 116 in this embodiment can be disposed in front of the first quarter-wave plate 111; or, as shown in Figure 16, the second linear polarization operation module 116 can be disposed behind the second quarter-wave plate 113.

[0107] In some embodiments, when M is 2, that is, when the polarization encoding unit 110 of this disclosure includes 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 FIG17. The second linear polarization operation module 116 and the third linear polarization operation module 116 can both be disposed in front of the first quarter-wave plate 111; or, as shown in FIG18, the second linear polarization operation module 116 and the third linear polarization operation module 116 can both be disposed in front of the first quarter-wave plate 111. After the second quarter-wave plate 113; or, as shown in Figure 19, one of the second linear polarization operation module 116 and the third linear polarization operation module 116 can be set before the first quarter-wave plate 111 and the other after the second quarter-wave plate 113. In this embodiment, the second linear polarization operation module 116 is set before the first quarter-wave plate 111 and the third linear polarization operation module 116 is set after 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.

[0108] In some of these embodiments, when M is 2, that is, when the polarization encoding unit 110 of this disclosure includes two external linear polarization operation modules (i.e., the second linear polarization operation module 116 and the third linear polarization operation module 116), the angle between the intrinsic polarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116 is n·22.5°, where n is an integer.

[0109] Based on the above implementation, when the included angle between the intrinsic polarization 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 intrinsic polarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116 is achieved by rotating at least one of the second linear polarization operation module 116 and the third linear polarization operation module 116.

[0110] In other embodiments, the polarization encoding unit 110 further includes a polarization state rotator disposed between the second linear polarization operation module 116 and the third linear polarization operation module 116, which adjusts the angle between the intrinsic polarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116.

[0111] In other embodiments, the polarization encoding unit 110 further includes: two polarization state rotators, which are respectively disposed at the front end and 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 adjust the angle between the intrinsic polarization states of the second linear polarization operation module 116 and the third linear polarization operation module 116; optionally, one of the two polarization state rotators realizes a polarization state rotation angle γ, and the other of the two polarization state rotators realizes a polarization state rotation angle -γ.

[0112] In some embodiments, when N is greater than 1, that is, when the number N of the built-in linear polarization operation modules 112 is greater than 1, the device further includes N-1 optical isolation units, which can be optical isolators or optical circulators, and the N-1 optical isolation units are respectively disposed between any two adjacent built-in linear polarization operation modules.

[0113] In some embodiments, when N is greater than 1 and / or M is greater than 1, that is, when the number of built-in linear polarization operation modules 112 N is greater than 1 and / or the number of external linear polarization operation modules 116 M is greater than 1, the device further includes N+M-1 optical isolation units, the optical isolation units being optical isolators or optical circulators, and the N+M-1 optical isolation units are respectively disposed between any two adjacent linear polarization operation modules (including built-in linear polarization operation modules and external linear polarization operation modules).

[0114] In some embodiments, the polarization state of the optical pulse input to the quantum state encoding device of this disclosure can be a linearly polarized state of any shape. For example, the polarization state of the optical pulse input to the device can be a horizontally polarized state or a vertically polarized state.

[0115] In some embodiments, when M is 1 and the external linear polarization operation module is positioned in front of the first quarter-wave plate 111, the polarization state of the optical pulse input to the device is... in, and These are the two intrinsic polarization states of the linear polarization control optical path of the second linear polarization operation module, where θ is any value from 0 to 2π.

[0116] In some embodiments, referring to Figure 20, the polarization encoding unit 110 of this disclosure may include two series-connected adjustable circular birefringence modules.

[0117] In some embodiments, when two adjustable circular birefringence modules are connected in series with an external linear polarization operation module, the external linear polarization operation module can be positioned before, after, or between the two adjustable circular birefringence modules.

[0118] In some embodiments, as shown in FIG21, the polarization encoding unit 110 includes two series-connected adjustable circular birefringence modules and an external linear polarization operation module, such as the second linear polarization operation module 116 in FIG21. 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.

[0119] In some other embodiments, as shown in FIG22, the second linear polarization operation module 116 may be disposed between two adjustable circular birefringence modules, that is, disposed after the second quarter-wave plate 113 of the first adjustable circular birefringence module and disposed in front of the first quarter-wave plate 111 of the second adjustable circular birefringence module.

[0120] In some other embodiments, as shown in FIG23, the second linear polarization operation module 116 may also be disposed after the two adjustable circular birefringence modules, that is, connected to the second quarter-wave plate 113 of the second adjustable circular birefringence module.

[0121] In some embodiments, as shown in FIG24, 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.

[0122] In some embodiments, as shown in FIG25, the fifth optical coupling unit 221 is a polarization beam splitter and the sixth optical coupling unit 222 is a polarization beam combiner.

[0123] In some implementations, as shown in FIG26, the fifth optical coupling unit 221 is a polarization beam splitter and the sixth optical coupling unit 222 is an optical coupler.

[0124] In some implementations, as shown in FIG27, the fifth optical coupling unit 211 is an optical coupler and the sixth optical coupling unit 222 is a polarization combiner.

[0125] In some embodiments, as shown in FIG28, the fifth optical coupling unit 221 is an optical coupler, the sixth optical coupling unit 222 is an optical coupler, and the polarization-to-time phase encoding unit 130 further includes two polarizers 225 and 226, which are respectively disposed on the fourth transmission optical path 223 and the fifth transmission optical path 224, and the polarization directions of the polarizers 225 and 226 are orthogonal to each other.

[0126] In some embodiments, referring to any of the figures 26-28, the fourth transmission optical path 223 and the fifth transmission optical path 224 are 90° twisted polarization-maintaining fibers, or the polarization-to-time phase encoding unit 130 of this disclosure further includes a 90° polarization state rotator, which is disposed on the fourth transmission optical path 223 or the fifth transmission optical path 224, for rotating the polarization state of the passing sub-light pulse by 90°.

[0127] In some embodiments, as shown in FIG29, the fifth optical coupling unit and the sixth optical coupling unit are the same polarization beam splitter 221. The polarization-to-time phase encoding unit 130 further includes two mirrors 227 and 228. The two output ports I and H of the polarization beam splitter 221 are respectively connected to one end of the fourth transmission optical path 223 and one end of the fifth transmission optical path 224. The two mirrors 227 and 228 are respectively connected to the other end of the fourth transmission optical path 223 and the other end of the fifth transmission optical path 224.

[0128] In some of the above embodiments, the two reflectors 227 and 228 may be polarization state rotating reflectors.

[0129] In one embodiment, when the polarization beam splitter 221 includes three ports, the input port G can also serve as the output port of the polarization-to-time-phase encoding unit 130, for outputting optical pulses encoded by polarization-to-time-phase encoding. In this case, the polarization-to-time-phase encoding unit 130 also includes an optical coupling unit, which is disposed at the front end of the polarization beam splitter 221. The optical coupling unit can be an optical coupler or an optical circulator.

[0130] In another embodiment, when the two reflectors 227 and 228 are polarization state rotating reflectors, for example, when the two reflectors 227 and 228 are quarter-wave plate reflectors or 90° Faraday rotating reflectors, the polarization beam splitter 221 may also include 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-to-time phase encoding unit 130.

[0131] In some embodiments, as shown in FIG30, the fifth optical coupling unit and the sixth optical coupling unit are the same optical coupler 221. The polarization-to-time phase encoding unit 130 further includes: two mirrors 227 and 228 and two polarizers 225 and 226. The two output ports I and H of the optical coupler 221 are respectively connected to one end of the fourth transmission optical path 223 and one end of the fifth transmission optical path 224. The two mirrors 227 and 228 are respectively connected to the other end of the fourth transmission optical path 223 and the other end of the fifth transmission optical path 224. The two polarizers 225 and 226 are respectively disposed on the fourth transmission optical path 223 and the fifth transmission optical path 224, and the polarization directions of the polarizers 225 and 226 are orthogonal to each other.

[0132] In some embodiments, when the optical coupler 221 includes three ports, the input port G can also serve as the output port of the polarization-to-time-phase encoding unit 130 for outputting optical pulses encoded by polarization-to-time-phase encoding. In this case, the polarization-to-time-phase encoding unit 130 also includes an optical coupling unit, which is disposed at the front end of the optical coupler 221. The optical coupling unit can be an optical coupler or an optical circulator.

[0133] In some other embodiments, the optical coupler 221 may also include a fourth port G' (not shown in the figure); the fourth port G' of the optical coupler 221 is the output port of the polarization-to-time phase encoding unit 130.

[0134] In some embodiments, referring to any of the figures 24-30, the time phase encoding device may further include: a polarizer; the polarizer is disposed at the output port of the polarization-to-time phase encoding unit 130 and is used to polarize the output optical pulse.

[0135] In any of the above embodiments, the quantum state encoding device of this disclosure further includes: a quarter-wave plate and / or a polarization state rotator, disposed between the polarization encoding unit 100 and the polarization-to-time phase encoding unit 200, wherein the polarization state rotator is a half-wave plate or a Faraday rotator.

[0136] In some implementations, the quantum state encoding device of this disclosure can also be used to implement the quantum state decoding process, depending on the requirements of quantum communication.

[0137] According to another aspect of this disclosure, a quantum state encoding method is provided, which is applied to the quantum state encoding device described above.

[0138] In another aspect, this disclosure provides a software-defined quantum communication system. Figure 31 shows a schematic diagram of the structure of a software-defined quantum communication system provided in this disclosure. As shown in Figure 31, the software-defined quantum communication system 3100 may include the aforementioned quantum state encoding device 3101 and encoding control device 3102. 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.

[0139] The quantum communication system can be a discrete variable quantum communication system or a continuous variable quantum communication system, including quantum communication systems such as the BB84 protocol, the reference frame-independent protocol, the MDI protocol, and the TF protocol.

[0140] 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. Furthermore, each step of the methods of this disclosure can be performed by a corresponding component or unit of the apparatus or system of this disclosure.

[0141] 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.

[0142] 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 encoding device, wherein, include: The system comprises 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. The polarization encoding unit includes at least one adjustable circular birefringence module, which includes a first quarter-wave plate, N built-in linear polarization operation modules, and a second quarter-wave plate connected in series; N is an integer greater than or equal to 1. The first quarter-wave plate 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. The built-in linear polarization operation module includes a linear polarization control optical path and at least one phase modulator; the input end of the linear polarization control optical path is connected to one end of the first quarter-wave plate, and is used to receive the light pulse containing the two orthogonal linear polarization components after being converted by the first quarter-wave plate, and split it into two sub-light pulses. The phase modulator 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 with the phase difference and outputs them through the output end. One end of 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 one optical pulse output by the linear polarization control optical path into left-hand circular polarization components and right-hand circular polarization components, and then output them through the output end. The first optical coupling unit includes one input port and two output ports, namely the first port, the second port and the third port, and the first port is connected to the output end of the second quarter-wave plate in the polarization coding unit; The second optical coupling unit includes two input ports and one output port, namely the fourth port, the fifth port, and the sixth port; The polarization-to-time-phase encoding unit includes an input port and an output port, used to perform time-phase encoding conversion on the input polarization-encoded quantum state light pulse and output the time-phase encoded quantum state light pulse; 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 the 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 to form a second optical output branch; The first optical coupling unit is used to input the light pulse of the polarization-coded quantum state output by the polarization coding unit into the first optical output branch and / or the second optical output branch according to the quantum communication coding control command. The quantum communication coding control command is determined according to the coding requirements of the quantum communication system. The sixth port of the second optical coupling unit is the output port of the quantum state encoding device, which is used to output the optical pulse of the polarization-encoded quantum state transmitted by the second optical output branch or the optical pulse of the time-phase-encoded quantum state output by the first optical output branch according to the quantum communication encoding control command.

2. The apparatus according to 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 according to claim 2, wherein, The first optical coupling unit is used to input the light pulse of the polarization-coded quantum state output by the polarization coding unit through the first port, split the light pulse of the polarization-coded quantum state 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 used to select, according to the quantum communication encoding control command, to output either the optical pulse of the polarization-coded quantum state transmitted by the second optical output branch or the optical pulse of the time-phase-coded quantum state output by the first optical output branch.

4. The apparatus according to 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 according to claim 4, wherein, The first optical coupling unit is used to selectively input the optical pulse of the polarization-coded quantum state to the first optical output branch or the second optical output branch according to the quantum communication encoding control command; When the second optical coupling unit is an optical switch, the second optical coupling unit is used to connect the first optical output branch of the optical pulse that outputs the time phase encoded quantum state or the second optical output branch of the optical pulse that outputs the polarization encoded quantum state, according to the quantum communication encoding control command. When the second optical coupling unit is an optical coupler, the second optical coupling unit is used to output the optical pulse of the time phase encoded quantum state output by the first optical output branch or the optical pulse of the polarization encoded quantum state transmitted by the second optical output branch.

6. The apparatus according to claim 1, wherein, The linear polarization control optical path includes: 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; the phase modulator is disposed on the second transmission optical path or the third transmission optical path; The third optical coupling unit is used to receive the light pulse containing the two orthogonal linear polarization components after being converted by the first quarter-wave plate, and split it into two sub-light pulses, namely the first sub-light pulse and the second light pulse. The first light pulse and the second light pulse are transmitted along the second transmission optical path and the third transmission optical path in the linear polarization control optical path, respectively. The phase modulator modulates 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 is used to receive two sub-optical pulses that generate a phase difference and combine them into a single optical pulse for output.

7. The apparatus according to claim 1 or 6, wherein, One of the two intrinsic polarization states of the first quarter-wave plate With one of the two intrinsic polarization states of the linear polarization control optical path The included angle is 45°±n·90°; One of the two intrinsic polarization states of the second quarter-wave plate With one of the two intrinsic polarization states of the linear polarization control optical path The included angle is 45°±m·90°, where n and m are integers.

8. The apparatus according to claim 6, wherein, The third optical coupling unit is a polarization beam splitter, and the fourth optical coupling unit 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.

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

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

11. The apparatus according to claim 6, wherein, The third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter, and the linear polarization control optical path also includes two mirrors. The two reflectors are respectively connected to the second transmission optical path and the third transmission optical path, and are used to reflect the light pulses input to the two reflectors back to the polarization beam splitter; the polarization beam splitter The intrinsic polarization state is the intrinsic polarization state of the linear polarization control optical path.

12. The apparatus according to claim 11, wherein, The two mirrors are polarization-state rotating mirrors.

13. The apparatus according to claim 6, wherein, The third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter unit, the second transmission optical path and the third transmission optical path are the same transmission optical path, and the intrinsic polarization state of the polarization beam splitter unit is the intrinsic polarization state of the linear polarization control optical path.

14. The apparatus according to claim 13, wherein, The polarization beam splitter unit is a polarization beam splitter, which includes three ports: a first port, a second port, and a third port. The first port of the polarization beam splitter is the input and output port of the linear polarization control optical path. The second and third ports of the polarization beam splitter are connected through the same transmission optical path. The intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the polarization beam splitter unit.

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

16. The apparatus according to claim 13, wherein, The polarization beam splitter unit includes: an optical beam splitter, a first polarizer, and a second polarizer; The optical beamsplitter includes at least three ports: a first port, a second port, and a third port. The first port of the optical beamsplitter is the input port of the linear polarization control optical path. The second and third ports of the optical beamsplitter are respectively connected to ports on the first side of the first polarizer and ports on the first side of the second polarizer. Ports on the second side of the first polarizer and ports on 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 of the first polarizer The deflection direction of the second deflector Mutually orthogonal; the deflection direction of the first deflector The deflection direction of the second deflector The intrinsic polarization state of the polarization beam splitter unit.

17. The apparatus according to claim 16, wherein, The optical beam splitter also includes a fourth port; The fourth port of the optical beam splitter is the output port of the linear polarization control optical path.

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

19. The apparatus according to claim 18, wherein, The polarization coding unit further includes: an optical coupling unit; The optical coupling unit is an optical coupler or an optical circulator, and the optical coupling unit is disposed in front of the first quarter-wave plate and connected to the first quarter-wave plate.

20. The apparatus according to claim 14 or 16, wherein, The polarization coding unit further includes: 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 beam splitter.

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

22. The apparatus according to claim 21, wherein, The polarization encoding unit also includes a half-wave plate or a 90-degree Faraday rotator disposed in the transmission optical path.

23. The apparatus according to any one of claims 13 to 17, wherein, The phase modulator is disposed on the transmission optical path; the phase modulator includes a first port and a second port, which are respectively a forward input optical port and a reverse input optical port; the phase modulator modulates the optical pulse input to one of the first port and the second port, or modulates the optical pulse input to the first port and the second port with different phases.

24. The apparatus according to claim 23, wherein, The transmission optical path is coupled to the slow axis of the first and second ports of the phase modulator. Both are either coupled to the fast axis of the first and second ports of the phase modulator.

25. The apparatus according to claim 23, wherein, After applying a high-frequency modulation electrical signal with a frequency higher than a specified threshold, the phase modulator 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.

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

27. The apparatus according to claim 1, wherein, The polarization coding unit further includes: M external linear polarization operation modules are connected in series with the adjustable circular birefringence module, where M is an integer greater than or equal to 1.

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

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

30. The apparatus according to claim 29, wherein, The angle between the intrinsic polarization states of the two external linear polarization operation modules is achieved by rotating at least one of the two external linear polarization operation modules; and / or The polarization encoding unit further includes: a polarization state rotator, which is disposed between two external linear polarization operation modules, and adjusts the angle between the intrinsic polarization states of the two external linear polarization operation modules; and / or The polarization encoding unit further includes two polarization state rotators, which are disposed at the front and rear ends of one of the two external linear polarization operation modules, and the two polarization state rotators are used to adjust the angle between the intrinsic polarization states of the two external linear polarization operation modules.

31. The apparatus according to claim 1 or 27, wherein, The polarization encoding unit includes two cascaded adjustable circular birefringence modules.

32. The apparatus according to claim 1, wherein, When N is greater than 1, the polarization encoding unit also includes N-1 optical isolation units, which are optical isolators or optical circulators. The N-1 optical isolation units are respectively arranged between any two adjacent built-in linear polarization operation modules.

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

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

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

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

40. The apparatus according to claim 39, wherein, The two mirrors are polarization-state rotating mirrors.

41. The apparatus according to claim 34, wherein, The fifth optical coupling unit and the sixth optical coupling unit are the same optical coupler. The polarization-to-time phase encoding unit further includes two mirrors and two polarizers. The two output ports of the optical coupler are respectively connected to one end of the fourth transmission optical path and one end of the fifth transmission optical path, and the two reflectors are respectively connected to the other end of the fourth transmission optical path and the other end of the fifth transmission optical path; the two polarizers are respectively disposed on the fourth transmission optical path and the fifth transmission optical path, and the polarization directions of the two polarizers are orthogonal to each other.

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

43. The apparatus according to any one of claims 34 to 41, wherein, The polarization-to-time phase encoding unit further includes: a polarizer; The polarizer is located at the output port of the polarization-to-time phase encoding unit and is used to control the output. The light pulse is used for polarization.

44. The apparatus according to claim 1 or 27, wherein, The device further includes a quarter-wave plate and / or a polarization state rotator, disposed between the polarization encoding unit and the polarization-to-time phase encoding unit.

45. A quantum state encoding method, wherein, The quantum state encoding device according to any one of claims 1-44.

46. ​​A software-defined quantum communication system, wherein, Includes the quantum state encoding device and encoding control device as described in any one of claims 1-44; The encoding control device 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.

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