Time phase encoding device and method and quantum communication system

Abstract

The invention provides a time phase coding device and method and a quantum communication system, and the device comprises a polarization coding unit and a polarization-to-time phase coding unit which are connected in series, and the polarization coding unit comprises at least one adjustable circular birefringence module. The adjustable circular birefringence module is used for converting one path of input optical pulse into two orthogonal linear polarization components, splitting the two orthogonal linear polarization components into two paths of sub-optical pulses, performing phase modulation on the two paths of sub-optical pulses by using a phase modulator, enabling the two paths of sub-optical pulses to generate a phase difference, and then combining the two paths of sub-optical pulses to be output; the polarization-to-time phase coding unit is used for converting the optical pulse output by the adjustable circular birefringence module into an optical pulse in a time phase coding quantum state, and converting the two orthogonal linear polarization components into a circular polarization component to be output, and the polarization-to-time phase coding unit is used for converting the optical pulse output by the adjustable circular birefringence module into an optical pulse in a time phase coding quantum state. The quantum communication security requirement is met, the number of used lasers is reduced, and the weight and power consumption of a transmitter are reduced.

Description

Technical Field

[0001] The present application relates to the field of quantum communication and optical quantum coding technology, and in particular to a time phase coding device, method and quantum communication system. Background Art

[0002] Quantum communication technology is a frontier hotspot combining quantum physics and information science. Its current applications mainly include quantum key distribution and quantum direct communication. Based on physical principles such as the Heisenberg uncertainty relation in quantum mechanics and the quantum no-cloning theorem, quantum key distribution can share keys in real time and securely between communicating parties, and quantum direct communication can achieve information transmission security. 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 electricity.

[0003] The physical realization of quantum communication systems, such as quantum key distribution and quantum direct communication, requires encoding and decoding of quantum states. Time phase coding has the advantages of being resistant to channel environment disturbances and efficient coding. It has been highly valued by the industry and has become one of the main coding methods for quantum communication. One way to achieve time phase coding is through multiple lasers, each of which produces a coded quantum state. In order to meet the security requirements of quantum communication, reduce the number of lasers used, and reduce the weight and power consumption of quantum communication transmitters, a single laser is required to generate optical pulses and stably modulate the optical pulses with a time phase quantum state. Therefore, how to achieve stable time phase coded quantum states under a single laser is an important issue in quantum communication applications. Summary of the invention

[0004] In view of this, the present application provides a time phase encoding device, method and quantum communication system to solve the technical problems raised by the background technology.

[0005] According to a first aspect of the present application, a time phase encoding device is provided, comprising: a polarization encoding unit and a polarization-to-time phase encoding unit connected in series;

[0006] The polarization encoding unit includes at least one adjustable circular birefringence module, and the adjustable circular birefringence module includes a first quarter wave plate, N built-in linear polarization operation modules and a second quarter wave plate connected in series in sequence; N is an integer greater than or equal to 1;

[0007] The first quarter wave plate is used to convert the left-handed circular polarization component and the right-handed circular polarization component in an input optical pulse into two orthogonal linear polarization components;

[0008] 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 optical pulse containing the two orthogonal linear polarization components after being converted by the first quarter wave plate, and split it into two sub-optical pulses, perform phase modulation on at least one of the two sub-optical pulses through the phase modulator, so that a phase difference is generated between the two sub-optical pulses, and combine the two sub-optical pulses with the phase difference and output them through the output end;

[0009] One end of the second quarter wave plate is connected to the output end of the linear polarization control light path, and is used for converting the two orthogonal linear polarization components in a light pulse output by the linear polarization control light path into a left-handed circular polarization component and a right-handed circular polarization component, and then outputting them through the output end;

[0010] The polarization-to-time phase encoding unit is connected to the output end of the second quarter-wave plate, and is used to receive the optical pulse output by the second quarter-wave plate, perform time phase encoding conversion on the optical pulse, and then output an optical pulse in a time phase encoded quantum state.

[0011] In some embodiments, the linear polarization control optical path includes: a first optical coupling unit, a second optical coupling unit, a first transmission optical path, and a second transmission optical path; the first optical coupling unit and the second optical coupling unit are connected through the first transmission optical path and the second transmission optical path; the phase modulator is disposed on the first transmission optical path or the second transmission optical path;

[0012] The first optical coupling unit is used to receive the optical pulse containing the two orthogonal linear polarization components after conversion by the first quarter-wave plate, and split it into two paths of sub-optical pulses, namely a first path of optical pulses and a second path of optical pulses, and the first path of optical pulses and the second path of optical pulses are respectively transmitted along a first transmission optical path and a second transmission optical path in the linear polarization control optical path;

[0013] The phase modulator performs phase modulation on at least one of the first optical pulse and the second optical pulse, so as to generate a phase difference between the two optical pulses;

[0014] The second optical coupling unit is used to receive two paths of sub-light pulses that generate a phase difference, and combine them into one path of light pulses for output.

[0015] According to a second aspect of the present application, a time phase encoding method is provided, which is applied to the above-mentioned time phase encoding device.

[0016] According to a third aspect of the present application, a quantum communication system is provided, comprising the time phase encoding device as described above.

[0017] In summary, the time phase encoding device, method and quantum communication system provided by the embodiments of the present application have at least the following beneficial effects:

[0018] The temporal phase encoding device of the present application comprises a polarization encoding unit and a polarization-to-temporal phase encoding unit connected in series, wherein the polarization encoding unit comprises at least one adjustable circular birefringence module, wherein the adjustable circular birefringence module is formed by adopting a first quarter wave plate, a second quarter wave plate and N built-in linear polarization operation modules, wherein the first quarter wave plate can convert a left-handed circular polarization component and a right-handed circular polarization component in an input optical pulse into two orthogonal linear polarization components; and the built-in linear polarization operation module is formed by adopting a linear polarization control optical path and at least one phase modulator, wherein the linear polarization control optical path is connected to one end of the first quarter wave plate and is used to receive optical pulses of two orthogonal linear polarization components, And split it into two paths of sub-light pulses, the phase modulator can phase modulate at least one of the two paths of light pulses, so that a phase difference is generated between the two paths of light pulses and output; the second quarter wave plate can convert the two orthogonal linear polarization components in one path of light pulse output by the second optical coupling unit into a left-handed circular polarization component and a right-handed circular polarization component and then output, by connecting the polarization-to-time phase encoding unit to the output end of the second quarter wave plate, the polarization-to-time phase encoding unit can receive the light pulse output by the second quarter wave plate, and the polarization-to-time phase encoding unit can convert it into a time phase encoding and then output a light pulse of a time phase encoded quantum state. The time phase encoding device described in the embodiment of the present application can realize the stable generation of light pulses of polarization encoded quantum states, and the encoding conversion output of light pulses of polarization encoded quantum states to light pulses of time phase encoded quantum states, which meets the time phase encoding requirements of quantum communication systems. 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 quantum communication transmitters. The time phase encoded quantum state of the present application has strong stability and can meet the requirements of quantum communication applications for time phase encoded quantum states. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic structural diagram of a first embodiment of a time phase encoding device provided in an embodiment of the present application is shown;

[0021] Figure 2A schematic structural diagram of a second embodiment of a time phase encoding device provided in an embodiment of the present application is shown;

[0022] Figure 3 A schematic structural diagram of a first embodiment of an adjustable circular birefringence module provided in an embodiment of the present application is shown;

[0023] Figure 4 A schematic structural diagram of a first embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0024] Figure 5 A schematic structural diagram of a first embodiment of a linear polarization operation module provided in an embodiment of the present application is shown;

[0025] Figure 6 A schematic structural diagram of a second embodiment of a linear polarization operation module provided in an embodiment of the present application is shown;

[0026] Figure 7 A schematic structural diagram of a third embodiment of a linear polarization operation module provided in an embodiment of the present application is shown;

[0027] Figure 8 A schematic structural diagram showing a fourth embodiment of a linear polarization operation module provided in an embodiment of the present application;

[0028] Fig. 9 A schematic structural diagram of a fifth embodiment of a linear polarization operation module provided in an embodiment of the present application is shown;

[0029] Fig.10 A schematic structural diagram showing a sixth embodiment of a linear polarization operation module provided in an embodiment of the present application;

[0030] Fig.11 A schematic structural diagram showing a seventh embodiment of a linear polarization operation module provided in an embodiment of the present application;

[0031] Fig.12 A schematic structural diagram of a second embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0032] Fig.13 A schematic structural diagram of a third embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0033] Fig.14 A schematic structural diagram of a fourth embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0034] Fig.15 A schematic structural diagram of a fifth embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0035] Fig.16 A schematic structural diagram of a sixth embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0036] Fig.17 A schematic structural diagram of a seventh embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0037] Fig.18 A schematic structural diagram of an eighth embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0038] Fig.19 A schematic structural diagram of a ninth embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0039] Fig. 20 A schematic diagram showing the structure of a tenth embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0040] Fig.21 A schematic structural diagram of an eleventh embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0041] Fig. 22 A schematic structural diagram of a twelfth embodiment of a polarization coding unit provided in an embodiment of the present application is shown;

[0042] Fig.23 A schematic structural diagram of a first embodiment of a polarization-to-temporal phase encoding unit provided in an embodiment of the present application is shown;

[0043] Fig.24 A schematic diagram showing the structure of a second embodiment of a polarization-to-temporal phase encoding unit provided in an embodiment of the present application is shown;

[0044] Fig.25 A schematic structural diagram showing a third embodiment of a polarization-to-temporal phase encoding unit provided in an embodiment of the present application is shown;

[0045] Fig.26 A schematic structural diagram showing a fourth embodiment of a polarization-to-temporal phase encoding unit provided in an embodiment of the present application is shown;

[0046] Fig. 27 A schematic structural diagram showing a fifth embodiment of a polarization-to-temporal phase encoding unit provided in an embodiment of the present application is shown;

[0047] Fig.28 A schematic diagram showing the structure of a sixth embodiment of a polarization-to-temporal phase encoding unit provided in an embodiment of the present application is shown;

[0048] Fig.29 A schematic diagram showing the structure of a seventh embodiment of a polarization-to-temporal phase encoding unit provided in an embodiment of the present application is shown;

[0049] Fig.30 A schematic structural diagram of a third embodiment of a time phase encoding device provided in an embodiment of the present application is shown;

[0050] Fig.31 A schematic diagram of the structure of a quantum communication system provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0051] In order to make the above and other features and advantages of the present application more clear, the present application is further described below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explaining to those skilled in the art and are only exemplary and not restrictive.

[0052] In the following description, many specific details are set forth to provide a thorough understanding of the present application. However, it is apparent to those skilled in the art that specific details need not be adopted to practice the present application. In other cases, well-known steps or operations are not described in detail to avoid blurring the present application.

[0053] It should be noted that the time phase encoding described in the present application includes phase encoding, that is, the time phase encoding is an encoding composed of any combination of quantum states of X phase basis, Y phase basis, and Z time basis.

[0054] The present application provides a time phase encoding unit. Figure 1 This is a schematic structural diagram of a first embodiment of a time phase encoding device provided in an embodiment of the present application. The time phase encoding device may include a polarization encoding unit 100 and a polarization-to-time phase encoding unit 200 connected in series.

[0055] In one embodiment, if Figure 2 As shown, the polarization encoding unit 100 includes at least one adjustable circular birefringence module, wherein the adjustable circular birefringence module includes a first quarter wave plate 110, N built-in linear polarization operation modules 120 and a second quarter wave plate 130 connected in series in sequence; N is an integer greater than or equal to 1. Figure 2 Only one embodiment including an adjustable circular birefringence module is shown, and the adjustable circular birefringence module only includes one built-in linear polarization operation module 120. In one embodiment, the first quarter wave plate 110 is used to convert the left-handed circular polarization component and the right-handed circular polarization component in an input optical pulse into two orthogonal linear polarization components. In one embodiment, Figure 2As shown, the built-in linear polarization operation module 120 includes a linear polarization control optical path 121 and at least one phase modulator 122; the input end of the linear polarization control optical path 121 is connected to one end of the first quarter wave plate 110, and is used to receive the optical pulse containing the two orthogonal linear polarization components after being converted by the first quarter wave plate 110, and the first quarter wave plate 110 splits it into two sub-optical pulses, and then phase modulates at least one of the two sub-optical pulses through the phase modulator 122, so that a phase difference is generated between the two sub-optical pulses, and the two sub-optical pulses with the phase difference are combined and output through the output end. In one embodiment, one end of the second quarter wave plate 130 is connected to the output end of the linear polarization control optical path 121, and is used to convert the two orthogonal linear polarization components in one optical pulse output by the linear polarization control optical path 121 into a left-handed circular polarization component and a right-handed circular polarization component, and then output them through the output end.

[0056] In one embodiment, Figure 2 As shown, the polarization-to-temporal phase encoding unit 200 is connected to the output end of the second quarter wave plate 130, and is used to receive the optical pulse output by the second quarter wave plate 130, perform time phase encoding conversion on it, and then output a time phase encoded quantum state optical pulse.

[0057] The time phase encoding device of the present application can realize the stable generation of optical pulses of polarization-encoded quantum states, and the coded output of optical pulses of polarization-encoded quantum states to optical pulses of time phase-encoded quantum states, meeting the time phase encoding requirements of quantum communication systems. The present application can also realize the security requirements of quantum communication, reduce the number of lasers used, and reduce the weight and power consumption of quantum communication transmitters. The time phase-encoded quantum state of the present application has strong stability and can meet the requirements of quantum communication applications for time phase-encoded quantum states.

[0058] In some embodiments, referring to Figure 3 As shown, the linear polarization control optical path 121 includes: a first optical coupling unit 123, a second optical coupling unit 124, a first transmission optical path 125, and a second transmission optical path 126; the first optical coupling unit 123 and the second optical coupling unit 124 are connected through the first transmission optical path 125 and the second transmission optical path 126; the phase modulator 122 is arranged on the first transmission optical path 125 or the second transmission optical path 126.

[0059] In some embodiments, referring again to the attached Figure 3As shown, the first optical coupling unit 123 of the linear polarization control optical path 121 is connected to one end of the first quarter wave plate 110, and the first optical coupling unit 123 is used to receive the optical pulse containing the two orthogonal linear polarization components after conversion by the first quarter wave plate 110, and split it into two paths of sub-optical pulses, namely the first path of optical pulses and the second path of optical pulses, which are respectively transmitted along the first transmission optical path 125 and the second transmission optical path 126 in the linear polarization control optical path 121, and the phase modulator 122 performs phase modulation on the first path of optical pulses and / or the second path of optical pulses to generate a phase difference between the two paths of optical pulses, and the two paths of sub-optical pulses with the phase difference are combined into one path of optical pulses by the second optical coupling unit 124 for output; the second optical coupling unit 124 is used to receive the two paths of sub-optical pulses with the phase difference, and combine them into one path of optical pulses for output. Among them, one of the two intrinsic polarization states of the linear polarization control optical path 121 is

[0060] In some embodiments, referring again to the attached Figure 3 As shown, the second quarter wave plate 130 is connected to the second optical coupling unit 124, and is used to convert two orthogonal linear polarization components in a beam-combined optical pulse output by the second optical coupling unit 124 into a left-handed circular polarization component and a right-handed circular polarization component for output.

[0061] In some embodiments, one of the two eigenpolarization states of the first quarter-wave plate 110 is One of the two intrinsic polarization states of the linear polarization control optical path 121 The angle is 45°±n·90°; one of the two eigenpolarization states of the second quarter-wave plate 130 One of the two intrinsic polarization states of the linear polarization control optical path 121 The included angle is 45°±m·90°, where n and m are integers.

[0062] In some embodiments, referring to Figure 4 As shown, when N is 2, that is, when the adjustable circular birefringence module includes two built-in linear polarization operation modules 120 , the two built-in linear polarization operation modules 120 are arranged in series between the first quarter wave plate 110 and the second quarter wave plate 130 .

[0063] In some of these embodiments, refer to the attached Figure 5 As shown, the first optical coupling unit 123 is a polarization beam splitter, the second optical coupling unit 124 is a polarization beam combiner, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the linear polarization control optical path 121 .

[0064] In some other embodiments, refer to the attached Figure 6As shown, the first optical coupling unit 123 is a polarization beam splitter, the second 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 121 .

[0065] In some other embodiments, refer to the attached Figure 7 As shown, the first optical coupling unit 123 is an optical coupler, the second optical coupling unit 124 is a polarization beam combiner, and the intrinsic polarization state of the polarization beam combiner is the intrinsic polarization state of the linear polarization control optical path 121 .

[0066] In some other embodiments, refer to the attached Figure 8 As shown, the first optical coupling unit 123 and the second optical coupling unit 124 are the same polarization beam splitter 123, and the linear polarization control optical path 121 further includes: two reflectors 211 and 212, the reflectors 211 and 212 are respectively connected to the first transmission optical path 125 and the second transmission optical path 126, and are used to reflect the light pulses input to the reflectors 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 121. Optionally, the reflectors 211 and 212 are polarization state rotating reflectors, which realize the polarization state of the reflected sub-light pulse being rotated by a certain angle compared to the polarization state of the sub-light pulse before reflection, such as a 90° polarization state rotating reflector, and the reflectors 211 and 212 can be quarter-wave plate reflectors or 90° Faraday rotating reflectors.

[0067] 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, wherein port B and port C are connected to two reflectors through the second transmission optical path 126 and the first transmission optical path 125, respectively, and port A is used as an input port for receiving the optical pulse of the input linear polarization control optical path 121. Specifically, as shown in FIG. Figure 8 As shown, port B is connected to the reflector 212 through the second transmission light path 126 , and port C is connected to the reflector 211 through the first transmission light path 125 .

[0068] In one embodiment, when the polarization beam splitter 123 includes three ports, the input port A can also serve as an output port of the linear polarization control light path 121 for outputting optical pulses modulated by the linear birefringence of the linear polarization control light path 121 . In this embodiment, the polarization encoding unit 100 further includes an optical coupling unit, which includes at least three ports, namely a first port, a second port and a third port. The optical coupling unit can be arranged between the first quarter wave plate 110 and the polarization beam splitter 123, the first port of the optical coupling unit is connected to the first quarter wave plate 110, 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 130; or the optical coupling unit can be arranged before the first quarter wave plate 110, the first port of the optical coupling unit receives an input optical pulse, the second port of the optical coupling unit is connected to the first quarter wave plate 110, and the third port of the optical coupling unit is an output port. In this case, the first quarter wave plate 110 and the second quarter wave plate 130 are the same device; the optical coupling unit is an optical coupler or an optical circulator.

[0069] In yet another embodiment, Figure 8 As shown, the polarization beam splitter 123 may further include an output port D, which serves as an output port of the linear polarization control light path 121 and is used to output the optical pulse modulated by the linear birefringence of the linear polarization control light path 121 .

[0070] It should be noted that, when the reflectors 211 and 212 do not rotate the polarization states of the input sub-light pulses, the polarization beam splitter 123 only outputs the combined light pulse from port A. When the reflectors 211 and 212 rotate the polarization states of the input sub-light pulses by any angle (not 0 and 90°), the polarization beam splitter 123 can output the combined light pulse from port A or port D, wherein if the polarization states of the sub-light pulses are rotated by 90°, the combined light pulse can only be output from port D.

[0071] In some of these embodiments, refer to the attached Fig. 9 As shown, the first optical coupling unit 123 and the second optical coupling unit 124 are the same polarization beam splitting unit 201 , the first transmission optical path 125 and the second transmission optical path 126 are the same transmission optical path 205 , and the intrinsic polarization state of the polarization beam splitting unit 201 is the intrinsic polarization state of the linear polarization control optical path 121 .

[0072] In the above-mentioned embodiment, again referring to the attached Fig. 9As shown, 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 121, the second port B and the third port C of the polarization beam splitter are connected through the same transmission optical path 205, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the polarization beam splitter unit 201.

[0073] In the above embodiment, the input and output of the linear polarization control optical path 121 are the same port, and the polarization encoding unit 100 may further include an optical coupling unit, the optical coupling unit includes at least three ports, namely a first port, a second port and a third port, and the optical coupling unit may be arranged between the first quarter wave plate 110 and the polarization beam splitter 201, the first port of the optical coupling unit is connected to the first quarter wave plate 110, the second port of the optical coupling unit is connected to the polarization beam splitter 201, and the third port of the optical coupling unit is connected to the second quarter wave plate 130; or the optical coupling unit may be arranged before the first quarter wave plate 110, the first port of the optical coupling unit receives an input optical pulse, the second port of the optical coupling unit is connected to the first quarter wave plate 110, and the third port of the optical coupling unit is an output port. In this case, the first quarter wave plate 110 and the second quarter wave plate 130 are the same device; the optical coupling unit is an optical coupler or an optical circulator.

[0074] In some embodiments, referring to Fig.10 As shown, in the case where the first optical coupling unit 123 and the second optical coupling unit 124 are the same polarization beam splitting unit, the polarization beam splitting 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, the first port A of the polarization beam splitter 201 is the input port of the linear polarization control light path 121, and the fourth port D of the polarization beam splitter 201 is the output port of the linear polarization control light path 121; the second port B and the third port C of the polarization beam splitter 201 are the output ports of the linear polarization control light path 121; The three ports C are respectively 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; 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 an 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, wherein θ, 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 splitter unit.

[0075] In some embodiments, referring to Fig.11 As shown, in the case where the first optical coupling unit 123 and the second optical coupling unit 124 are the same polarization beam splitting unit, 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, and the first port A of the optical beam splitter 201 is the input port of the linear polarization control optical path 121; the second port B and the third port C of the optical beam splitter 201 are respectively 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; 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 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 The polarization direction of the second polarizer 207 Orthogonal to each other; the polarization direction of the first polarizer 206 The polarization direction of the second polarizer 207 is the intrinsic polarization state of the polarization beam splitter unit.

[0076] In the above embodiment, when the input and output of the linear polarization control optical path 121 are the same port, the polarization encoding unit 100 may further include 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 may be arranged between the first quarter wave plate 110 and the optical beam splitter 201, the first port of the optical coupling unit is connected to the first quarter wave plate 110, 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 130; or the optical coupling unit may be arranged before the first quarter wave plate 110, the first port of the optical coupling unit receives an input optical pulse, the second port of the optical coupling unit is connected to the first quarter wave plate 110, and the third port of the optical coupling unit is an output port, in which case the first quarter wave plate 110 and the second quarter wave plate 130 are the same device; the optical coupling unit is an optical coupler or an optical circulator.

[0077] In some further embodiments, the optical beam splitter 201 further includes a fourth port D (not shown in the figure); the fourth port D of the optical beam splitter 201 is an output port of the linear polarization control optical path 121 .

[0078] In some embodiments, when the input and output of the linear polarization control optical path 121 are the same port, refer to the attached Fig.12As shown, the polarization encoding unit 100 further includes: an optical coupling unit 150 ; the optical coupling unit 150 is an optical coupler or an optical circulator, and the optical coupling unit 150 is arranged before the first quarter wave plate 110 , and the optical coupling unit 150 is connected to the first quarter wave plate 110 .

[0079] In the above-mentioned embodiment, again referring to the attached Fig.12 As shown, when the input and output of the linear polarization control optical path are the same port, the first quarter wave plate 110 and the second quarter wave plate 130 can also be the same device (ie Fig.12 In this case, the optical coupling unit 150 is disposed before the first quarter wave plate 110, so that the input function and the output function of the first quarter wave plate 110 can be separated.

[0080] In some other embodiments, refer to the attached Fig.13 As shown, when the input and output of the linear polarization control optical path are the same port, the optical coupling unit 150 can be directly arranged in series at the front end of the polarization beam splitter unit. At this time, the input function and the output function of the polarization beam splitter unit can be separated. The first quarter wave plate 110 and the second quarter wave plate 130 are not the same device, and the optical coupling unit 150 is also separately connected to the first quarter wave plate 110 and the second quarter wave plate 130 to realize the input and output of the optical pulse. Among them, the optical coupling unit 150 is an optical coupler or an optical circulator.

[0081] exist Figure 9-11 In some implementations, the transmission optical path 205 is a free space optical path or a polarization-maintaining optical fiber.

[0082] See attached Figure 9-11 In any of the figures, the phase modulator 122 is arranged on the transmission optical path 205; the phase modulator 122 includes a first port E and a second port F, which are a forward input optical port and a reverse input optical port respectively; the phase modulator 122 modulates the optical pulse input from one of the first port E and the second port F, or performs different phase modulations on the optical pulses input from the first port E and the second port F.

[0083] In the above embodiment, after the phase modulator 122 applies a high-frequency modulated electrical signal having a frequency higher than a specified threshold, the phase modulator 122 operates in a non-reciprocal state, and the ratio of the modulation efficiency of the first path of sub-optical pulses input from the forward input optical port to the modulation efficiency of the second path of sub-optical pulses input from the reverse input optical port is not less than a preset threshold. When the phase modulator 122 applies a high-frequency modulated signal having a frequency higher than a specified threshold, at the same time, the phase modulator 122 may have multiple sub-optical pulses input from the forward input optical port and multiple sub-optical pulses input from the reverse input optical port.

[0084] In some of these embodiments, refer to the attached Figure 9-11 In any of the figures, the transmission optical path 205 is coupled to the slow axes of the first port E and the second port F of the phase modulator 122, or is coupled to the fast axes of the first port E and the second port F of the phase modulator 122.

[0085] In some of these embodiments, refer to the attached Figure 9-11 As shown in any of the figures in the figure, the polarization encoding unit 100 of the present application further includes a polarization state rotator arranged in the transmission optical path 205, and the polarization state rotator can be a half-wave plate or a 90-degree Faraday rotator.

[0086] In some embodiments, referring to Fig.14 As shown, the polarization coding unit 100 of the present application further includes: M external linear polarization operation modules, such as Fig.14 The second linear polarization operation module in the embodiment. The external linear polarization operation module is connected in series with the adjustable circular birefringence module, and M is an integer greater than or equal to 1. Fig.14 The structure of the adjustable circular birefringence module is Figure 2 Take the structure shown in as an example, Fig.14 As shown in FIG. 1 , the polarization coding unit 100 includes an external linear polarization operation module 140 .

[0087] It should be noted that the external linear polarization operation module 140 and the internal linear polarization operation module 120 described in the embodiment of the present application have the same structure and function. In the embodiment of the present application, the linear polarization operation module disposed in the adjustable circular birefringence module is referred to as the internal linear polarization operation module. Fig.14 The first linear polarization operation module 120 in the adjustable circular birefringence module; the linear polarization operation module arranged outside the adjustable circular birefringence module in series is called an external linear polarization operation module, such as Fig.14 The second linear polarization operation module 140 in FIG. Fig.14 As shown, the second linear polarization operation module 140 in the embodiment of the present application can be arranged before the first quarter wave plate 110; Fig.15 As shown, the second linear polarization operation module 140 is disposed behind the second quarter wave plate 130 .

[0088] In some embodiments, when M is 2, that is, when the polarization coding unit 100 of the present application includes two external linear polarization operation modules (that is, the second linear polarization operation module 140 and the third linear polarization operation module 140), the second linear polarization operation module 140 and the third linear polarization operation module 140 are connected in series, such as Fig.16 As shown, the second linear polarization operation module 140 and the third linear polarization operation module 140 can be both arranged before the first quarter wave plate 110; or, as shown in FIG. Fig.17 As shown, the second linear polarization operation module 140 and the third linear polarization operation module 140 can both be arranged after the second quarter wave plate 130; or, as shown in Fig.18 As shown, the second linear polarization operation module 140 and the third linear polarization operation module 140 can be arranged in front of the first quarter wave plate 110, and the other can be arranged behind the second quarter wave plate 130. In this embodiment, the second linear polarization operation module 140 is arranged in front of the first quarter wave plate 110, and the third linear polarization operation module 140 is arranged behind the second quarter wave plate 130. It can be understood that the positions of the second linear polarization operation module 140 and the third linear polarization operation module 140 can be interchanged.

[0089] In some other embodiments, when M is 2, that is, when the polarization coding unit 100 of the present application includes two external linear polarization operation modules (that is, the second linear polarization operation module 140 and the third linear polarization operation module 140), the angle between the intrinsic polarization states of the second linear polarization operation module 140 and the third linear polarization operation module 140 is n·22.5°, where n is an integer.

[0090] Based on the above-mentioned embodiment, when the angle between the intrinsic polarization states of the second linear polarization operation module 140 and the third linear polarization operation module 140 is n·22.5°, the angle between the intrinsic polarization states of the second linear polarization operation module 140 and the third linear polarization operation module 140 is achieved by rotating at least one of the second linear polarization operation module 140 and the third linear polarization operation module 140.

[0091] In other embodiments, the polarization encoding unit 100 further includes: a polarization state rotator, which is arranged between the second linear polarization operation module 140 and the third linear polarization operation module 140, and the angle between the intrinsic polarization states of the second linear polarization operation module 140 and the third linear polarization operation module 140 is adjusted by the polarization state rotator.

[0092] In other embodiments, the polarization encoding unit 100 further includes: 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 140 and the third linear polarization operation module 140, and the angle between the intrinsic polarization states of the second linear polarization operation module 140 and the third linear polarization operation module 140 is adjusted by the two polarization state rotators; 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.

[0093] In some embodiments, when N is greater than 1, that is, when the number of built-in linear polarization operation modules N is greater than 1, the polarization encoding unit 100 further includes 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.

[0094] In some embodiments, when N is greater than 1 and / or M is greater than 1, that is, the number N of built-in linear polarization operation modules is greater than 1 and / or the number M of external linear polarization operation modules is greater than 1, the polarization coding unit 100 further includes 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 built-in linear polarization operation modules and external linear polarization operation modules).

[0095] In some embodiments, the polarization state of the optical pulse input into the temporal phase encoding device of the present application may be any linear polarization state, for example, the polarization state of the optical pulse input into the device may be a horizontal polarization state or a vertical polarization state.

[0096] In some embodiments, when M is 1, and the external linear polarization operation module is disposed before the first quarter wave plate 110, the polarization state of the light pulse input to the device is in, and are two eigenpolarization states of the linear polarization control light path of the second linear polarization operation module, and θ is any value between 0 and 2π.

[0097] In some embodiments, referring to Fig.19 As shown, the polarization encoding unit 100 of the present application may include two adjustable circular birefringence modules connected in series.

[0098] 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 arranged before the two adjustable circular birefringence modules, after the two adjustable circular birefringence modules, or between the two adjustable circular birefringence modules.

[0099] In some embodiments, such as Fig. 20 In the embodiment, the polarization coding unit 100 includes two series-connected adjustable circular birefringence modules and an external linear polarization operation module, such as Fig. 20 The second linear polarization operation module 140 may be disposed in front of the first quarter wave plate 110, that is, in front of the first adjustable circular birefringence module.

[0100] In some other embodiments, Fig.21As shown, the second linear polarization operation module 140 can be arranged between two adjustable circular birefringence modules, that is, arranged behind the second quarter wave plate 130 of the first adjustable circular birefringence module and arranged before the first quarter wave plate 110 of the second adjustable circular birefringence module.

[0101] In some other embodiments, Fig. 22 As shown, the second linear polarization operation module 140 can also be arranged after the two adjustable circular birefringence modules, that is, connected to the second quarter wave plate 130 of the second adjustable circular birefringence module.

[0102] In some embodiments, Fig.23 As shown, the polarization-to-time phase encoding unit includes: a third optical coupling unit 221, a fourth optical coupling unit 222, a third transmission optical path 223 and a fourth transmission optical path 224, the third optical coupling unit 221 includes at least three ports, an input port G and two output ports I, H; the fourth optical coupling unit includes at least three ports, two input ports I', H' and one output port G', the two output ports I, H of the third optical coupling unit 221 are respectively connected to the two input ports I', H' of the fourth optical coupling unit 222 through the third transmission optical path 223 and the fourth transmission optical path 224; the optical paths of the third transmission optical path 223 and the fourth transmission optical path 224 are not equal.

[0103] In some embodiments, such as Fig.24 As shown, the third optical coupling unit 221 is a polarization beam splitter, and the fourth optical coupling unit 222 is a polarization beam combiner.

[0104] In some embodiments, such as Fig.25 As shown, the third optical coupling unit 221 is a polarization beam splitter, and the fourth optical coupling unit 222 is an optical coupler.

[0105] In some embodiments, such as Fig.26 As shown, the third optical coupling unit 221 is an optical coupler, and the fourth optical coupling unit 222 is a polarization beam combiner.

[0106] In some embodiments, such as Fig. 27 As shown, the third optical coupling unit 221 is an optical coupler, the fourth optical coupling unit 222 is an optical coupler, and the polarization-to-time phase encoding unit 200 also includes: two polarizers 225 and 226, which are respectively arranged on the third transmission optical path 223 and the fourth transmission optical path 224, and the polarization directions of the polarizer 225 and the polarizer 226 are orthogonal to each other.

[0107] In some of these embodiments, refer to the attached Figure 25-27In any of the figures, the third transmission optical path 223 or the fourth transmission optical path 224 is a 90° twisted polarization-maintaining optical fiber, or the polarization-to-time phase encoding unit 200 of the present application further includes: a 90° polarization state rotator, which is arranged on the third transmission optical path 223 or the fourth transmission optical path 224, and is used to rotate the polarization state of the passing sub-light pulse by 90°.

[0108] In some embodiments, such as Fig.28 As shown, the third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter 221, and the polarization-to-time phase encoding unit 200 also includes: two reflectors 227 and 228, the two output ports I and H of the polarization beam splitter 221 are respectively connected to one end of the third transmission optical path 223 and one end of the fourth transmission optical path 224, and the two reflectors 227 and 228 are respectively connected to the other end of the third transmission optical path 223 and the other end of the fourth transmission optical path 224.

[0109] In some of the above embodiments, the two reflectors 227 and 228 may be polarization rotating reflectors.

[0110] 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 200, for outputting optical pulses that have been polarization-to-time phase encoded; at this time, the polarization-to-time phase encoding unit 200 also includes an optical coupling unit, which is disposed at the front end of the polarization beam splitter 221, and the optical coupling unit can be an optical coupler or an optical circulator.

[0111] In another embodiment, when the two reflectors 227 and 228 are polarization rotation mirrors, for example, the two reflectors 227 and 228 are quarter-wave plate mirrors or 90° Faraday rotation mirrors, 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 200.

[0112] In some embodiments, such as Fig.29As shown, the third optical coupling unit and the fourth optical coupling unit are the same optical coupler 221, and the polarization-to-time phase encoding unit 200 also includes: two reflectors 227, 228 and two polarizers 225, 226, the two output ports I, H of the optical coupler are respectively connected to one end of the third transmission optical path 223 and one end of the fourth transmission optical path 224, the two reflectors 227, 228 are respectively connected to the other end of the third transmission optical path 223 and the other end of the fourth transmission optical path 224; the two polarizers 225, 226 are respectively arranged on the third transmission optical path 223 and the fourth transmission optical path 224, and the polarization directions of the polarizer 225 and the polarizer 226 are orthogonal to each other.

[0113] In some of the 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 200, for outputting optical pulses that have been polarization-to-time phase encoded; at this time, the polarization-to-time phase encoding unit 200 also includes an optical coupling unit, which is disposed at the front end of the optical coupler 221, and the optical coupling unit can be an optical coupler or an optical circulator.

[0114] In some other embodiments, the optical coupler 221 may further 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-temporal phase encoding unit 200 .

[0115] In some of these embodiments, refer to the attached Figure 23-29 As shown in any of the figures, the temporal phase encoding device may further include: a polarizer; the polarizer is arranged at the output port of the polarization conversion temporal phase encoding unit 200, and is used to polarize the output optical pulse.

[0116] In any of the above-mentioned embodiments, as shown in Appendix 30, the time phase coding device of the present application also includes: a quarter wave plate and / or a polarization state rotator 300, which is arranged between the polarization coding unit 100 and the polarization-to-time phase coding unit 200, and the polarization state rotator is a half wave plate or a Faraday rotator.

[0117] In some implementations, according to the requirements of quantum communication, the time phase encoding device of the present application can also be used to implement the time phase decoding process.

[0118] According to another aspect of the present application, a time phase encoding method is provided, which is applied to the above-mentioned time phase encoding device.

[0119] Another aspect of the present application provides a quantum communication system. Fig.31 A schematic diagram of the structure of a quantum communication system provided in an embodiment of the present application is shown as follows: Fig.31As shown, the quantum communication system 3100 may include the time phase encoding device 3101 described in any embodiment of the present application.

[0120] The quantum communication system may be a discrete 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. It should be understood that the specific features, operations, and details described hereinabove regarding the apparatus of the present application may 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 may be performed by a corresponding component or unit of the apparatus or system of the present application.

[0121] The various 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 this specification as long as there is no contradiction in such combination.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A time phase encoding device, characterized in that: include: A polarization encoding unit and a polarization conversion time phase encoding unit connected in series; The polarization encoding unit includes at least one adjustable circular birefringence module, and the adjustable circular birefringence module includes a first quarter wave plate, N built-in linear polarization operation modules and a second quarter wave plate connected in series in sequence; N is an integer greater than or equal to 1; The first quarter wave plate is used to convert the left-handed circular polarization component and the right-handed circular polarization component in an input optical pulse into two orthogonal linear polarization 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 optical pulse containing the two orthogonal linear polarization components after being converted by the first quarter wave plate, and split it into two sub-optical pulses, perform phase modulation on at least one of the two sub-optical pulses through the phase modulator, so that a phase difference is generated between the two sub-optical pulses, and combine the two sub-optical pulses with the phase difference and output them through the output end; One end of the second quarter wave plate is connected to the output end of the linear polarization control light path, and is used for converting the two orthogonal linear polarization components in a light pulse output by the linear polarization control light path into a left-handed circular polarization component and a right-handed circular polarization component, and then outputting them through the output end; The polarization-to-time phase encoding unit is connected to the output end of the second quarter-wave plate, and is used to receive the optical pulse output by the second quarter-wave plate, perform time phase encoding conversion on the optical pulse, and then output an optical pulse in a time phase encoded quantum state.

2. The device according to claim 1, characterized in that The linear polarization control optical path includes: a first optical coupling unit, a second optical coupling unit, a first transmission optical path, and a second transmission optical path; the first optical coupling unit and the second optical coupling unit are connected through the first transmission optical path and the second transmission optical path; the phase modulator is arranged on the first transmission optical path or the second transmission optical path; The first optical coupling unit is used to receive the optical pulse containing the two orthogonal linear polarization components after conversion by the first quarter-wave plate, and split it into two paths of sub-optical pulses, namely a first path of optical pulses and a second path of optical pulses, and the first path of optical pulses and the second path of optical pulses are respectively transmitted along a first transmission optical path and a second transmission optical path in the linear polarization control optical path; The phase modulator performs phase modulation on at least one of the first optical pulse and the second optical pulse, so as to generate a phase difference between the two optical pulses; The second optical coupling unit is used to receive two paths of sub-light pulses that generate a phase difference, and combine them into one path of light pulses for output.

3. The device according to claim 1 or 2, characterized in that: One of the two eigenpolarization states of the first quarter wave plate One of the two eigenpolarization states of the linear polarization control optical path The angle 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 The included angle is 45°±m·90°, where n and m are integers.

4. The device according to claim 2, characterized in that The first optical coupling unit is a polarization beam splitter, the second optical coupling unit is a polarization beam combiner, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the linear polarization control optical path.

5. The device according to claim 2, characterized in that The first optical coupling unit is a polarization beam splitter, the second 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.

6. The device according to claim 2, characterized in that The first optical coupling unit is an optical coupler, the second optical coupling unit is a polarization beam combiner, and the intrinsic polarization state of the polarization beam combiner is the intrinsic polarization state of the linear polarization control optical path.

7. The device according to claim 2, characterized in that The first optical coupling unit and the second optical coupling unit are the same polarization beam splitter, and the linear polarization control optical path further comprises: two reflectors, The two reflectors are respectively connected to the first transmission optical path and the second transmission optical path, and are used to reflect the light pulses input to the two reflectors back to the polarization beam splitter; the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the linear polarization control optical path.

8. The device according to claim 7, characterized in that The two reflectors are polarization rotating reflectors.

9. The device according to claim 2, characterized in that The first optical coupling unit and the second optical coupling unit are the same polarization beam splitting unit, the first transmission optical path and the second transmission optical path are the same transmission optical path, and the intrinsic polarization state of the polarization beam splitting unit is the intrinsic polarization state of the linear polarization control optical path.

10. The device according to claim 9, characterized in that The polarization beam splitter unit is a polarization beam splitter, which includes three ports, namely 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 port and the third port of the polarization beam splitter are connected through the same transmission optical path, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the polarization beam splitter unit.

11. The device according to claim 9, characterized in that The polarization beam splitting unit comprises: a polarization beam splitter, a first polarizer and a second polarizer; The polarization beam splitter comprises four ports, namely 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, and 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 respectively connected to the port on the first side of the first polarizer and the port on the first side of the second polarizer; the port on the second side of the first polarizer and the port on the second side of the second polarizer are connected through the transmission optical path; the angle between the polarization direction of the first polarizer and an 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, wherein θ, 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 splitter.

12. The device according to claim 9, characterized in that The polarization beam splitting unit comprises: a beam splitter, a first polarizer and a second polarizer; The optical beam splitter comprises at least three ports, namely, 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 respectively connected to the port on the first side of the first polarizer and the port on the first side of the second polarizer; the port on the second side of the first polarizer and the port 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 a of the first polarizer is different from the polarization direction a of the second polarizer. mutually orthogonal; the polarizing direction of the first polarizer The polarizing direction of the second polarizer is the intrinsic polarization state of the polarization beam splitting unit.

13. The device according to claim 12, characterized in that The optical beam splitter further comprises a fourth port; The fourth port of the optical beam splitter is an output port of the linear polarization control light path.

14. The device according to claim 10 or 12, characterized in that The first quarter wave plate and the second quarter wave plate are the same device.

15. The device according to claim 14, characterized in that 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 arranged before the first quarter wave plate and connected to the first quarter wave plate.

16. The device according to claim 10 or 12, characterized in that 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 arranged between the first quarter wave plate and the polarization beam splitting unit.

17. The device according to any one of claims 9 to 13, characterized in that The transmission optical path is a free space optical path or a polarization-maintaining optical fiber.

18. The device according to claim 17, characterized in that The polarization encoding unit further includes a half-wave plate or a 90-degree Faraday rotator arranged in the transmission optical path.

19. The device according to any one of claims 9 to 13, characterized in that The phase modulator is arranged on the transmission optical path; the phase modulator comprises 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 inputted from one of the first port and the second port, or performs different phase modulations on the optical pulse inputted from the first port and the second port.

20. The device according to claim 19, characterized in that The transmission optical paths are both coupled to the slow axes of the first port and the second port of the phase modulator, or are both coupled to the fast axes of the first port and the second port of the phase modulator.

21. The device according to claim 19, characterized in that After applying a high-frequency modulated electrical signal having a frequency higher than a specified threshold, the phase modulator operates in a non-reciprocal state, and a ratio of a modulation efficiency of a first path optical pulse input from a forward input optical port to a modulation efficiency of a second path optical pulse input from a reverse input optical port is not less than a preset threshold.

22. The device according to claim 1, characterized in that When N is 2, two built-in linear polarization operation modules are arranged in series between the first quarter wave plate and the second quarter wave plate.

23. The device according to claim 1, characterized in that The polarization encoding unit also includes: M external linear polarization operation modules are connected in series with the adjustable circular birefringence module, and M is an integer greater than or equal to 1.

24. The device according to claim 23, characterized in that When M is 2, two external linear polarization operation modules are connected in series and are both arranged in front of the first quarter wave plate; or both are arranged after the second quarter wave plate; or one of the external linear polarization operation modules is arranged in front of the first quarter wave plate, and the other external linear polarization operation module is arranged after the second quarter wave plate.

25. The device according to claim 23, characterized in that 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.

26. The device according to claim 25, characterized in that 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 comprises: a polarization state rotator, wherein the polarization state rotator is 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, which are respectively 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.

27. The device according to claim 1 or 23, characterized in that The polarization encoding unit includes two tunable circular birefringence modules connected in series.

28. The device according to claim 1, characterized in that When N is greater than 1, the polarization encoding unit further includes N-1 optical isolation units, the optical isolation unit is an optical isolator or an optical circulator, and the N-1 optical isolation units are respectively arranged between any two adjacent built-in linear polarization operation modules.

29. The device according to claim 23, characterized in that 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, the optical isolation unit is an optical isolator or an optical circulator, and the N+M-1 optical isolation units are respectively arranged between any two adjacent linear polarization operation modules.

30. The device according to claim 1, characterized in that The polarization-to-temporal phase encoding unit comprises: a third optical coupling unit, a fourth optical coupling unit, a third transmission optical path and a fourth transmission optical path. The third optical coupling unit includes at least three ports, one input port and two output ports; the fourth optical coupling unit includes at least three ports, two input ports and one output port, the two output ports of the third optical coupling unit are connected to the two input ports of the fourth optical coupling unit through the third transmission optical path and the fourth transmission optical path; the optical path of the third transmission optical path is not equal to the optical path of the fourth transmission optical path.

31. The device according to claim 30, characterized in that The third optical coupling unit is a polarization beam splitter, and the fourth optical coupling unit is a polarization beam combiner.

32. The device according to claim 30, characterized in that The third optical coupling unit is a polarization beam splitter, and the fourth optical coupling unit is an optical coupler.

33. The device according to claim 30, characterized in that The third optical coupling unit is an optical coupler, and the fourth optical coupling unit is a polarization beam combiner.

34. The device according to claim 30, characterized in that The third optical coupling unit is an optical coupler, the fourth optical coupling unit is an optical coupler, and the polarization-to-temporal phase encoding unit further includes: two polarizers, The two polarizers are respectively arranged on the third transmission light path and the fourth transmission light path, and the polarization directions of the two polarizers are orthogonal to each other.

35. The device according to claim 30, characterized in that The third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter, and the polarization-to-temporal phase encoding unit further includes: two reflectors, The two output ports of the polarization beam splitter are respectively connected to one end of the third transmission optical path and one end of the fourth transmission optical path, and the two reflectors are respectively connected to the other end of the third transmission optical path and the other end of the fourth transmission optical path.

36. The device according to claim 35, characterized in that The two reflectors are polarization rotating reflectors.

37. The device according to claim 30, characterized in that The third optical coupling unit and the fourth optical coupling unit are the same optical coupler, and the polarization-to-temporal phase encoding unit further includes: two reflectors and two polarizers, The two output ports of the optical coupler are respectively connected to one end of the third transmission optical path and one end of the fourth transmission optical path, and the two reflectors are respectively connected to the other end of the third transmission optical path and the other end of the fourth transmission optical path; the two polarizers are respectively arranged on the third transmission optical path and the fourth transmission optical path, and the polarization directions of the two polarizers are orthogonal to each other.

38. The device according to claim 32 or 34, characterized in that The third transmission optical path or the fourth transmission optical path is a 90° twisted polarization-maintaining optical fiber, or, The polarization-to-temporal phase encoding unit further comprises: a 90° polarization state rotator, The 90° polarization state rotator is arranged on the third transmission optical path or the fourth transmission optical path, and is used to rotate the polarization state of the passing sub-light pulse by 90°.

39. The device according to any one of claims 30 to 37, characterized in that The polarization-to-temporal phase encoding unit further comprises: a polarizer; The polarizer is arranged at the output port of the polarization-to-temporal phase encoding unit and is used for polarizing the output optical pulse.

40. The device according to claim 1 or 23, characterized in that The device further comprises: a quarter wave plate and / or a polarization state rotator, which is arranged between the polarization encoding unit and the polarization-to-temporal phase encoding unit.

41. A time phase encoding method, characterized in that: A time phase encoding device as described in any one of claims 1-40 is used.

42. A quantum communication system, characterized in that: A time phase encoding device comprising any one of claims 1-40.

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