Time phase encoding apparatus, method and quantum communication system

Abstract

The application provides a time-phase encoding device, a method and a quantum communication system, and the device comprises a first polarization operation module, a second polarization operation module and an unequal arm polarization control interferometer connected in series, wherein the first polarization operation module and the second polarization operation module each comprise a polarization control optical path and a phase modulator, and the unequal arm polarization control interferometer comprises a fifth optical coupling unit, a sixth optical coupling unit and a transmission optical path with unequal optical paths; by setting the included angle between the intrinsic polarization state of the polarization control optical path in the two polarization operation modules and the included angle between the intrinsic polarization state of the unequal arm polarization control interferometer, the requirements of various quantum communication protocols are met. The application realizes the generation of three groups of six polarization encoding quantum states through two polarization operation modules, and then the polarization encoding quantum states are converted into time-phase encoding quantum states by using the unequal arm polarization control interferometer, so that the generation of X base / Y base phase base and Z base time base quantum states is realized.

Description

Technical Field

[0001] This invention relates to the fields of quantum communication and optical quantum coding technology, and in particular to a time phase coding device, method and 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. In fiber-optic quantum communication systems, time-phase encoding (including phase encoding) has advantages such as resistance to channel disturbances and efficient code generation, and has received attention from the industry, becoming the main encoding method for quantum communication.

[0004] How to make multiple quantum communication protocols compatible and realize multiple time-phase encoded quantum states in the same optical quantum coding device is an important problem in the current application of quantum communication. Summary of the Invention

[0005] This application provides a time phase encoding device, method, and quantum communication system to solve the technical problems mentioned in the prior art.

[0006] According to a first aspect of this application, a time-phase encoding device is provided, comprising: a first polarization operation module, a second polarization operation module, and an unequal-arm polarization control interferometer connected in series, wherein the first polarization operation module comprises: a first polarization control optical path and a first phase modulator; and the second polarization operation module comprises: a second polarization control optical path and a second phase modulator.

[0007] The first 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;

[0008] The first optical coupling unit is used to split the input optical pulse into two sub-optical pulses, namely a first sub-optical pulse and a second optical pulse. The first and second optical pulses are transmitted along the first and second transmission optical paths in the first polarization control optical path, respectively, and then combined into a single optical pulse by the second optical coupling unit for output. One of the two intrinsic polarization states of the first polarization control optical path is...

[0009] The first phase modulator is disposed in the first transmission optical path or the second transmission optical path of the first polarization control optical path; the first 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 transmission optical paths connected to the first phase modulator are all coupled to the slow axis of the first port and the second port of the first phase modulator, or are all coupled to the fast axis of the first port and the second port of the first phase modulator; the first phase modulator is used to perform phase modulation on the input sub-optical pulses, so that a phase difference φ is generated between the two sub-optical pulses.

[0010] The second polarization control optical path includes: 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 and the fourth optical coupling unit are connected through the third transmission optical path and the fourth transmission optical path;

[0011] The first polarization control optical path outputs an optical pulse, which is then input into the second polarization control optical path via the third optical coupling unit. The third optical coupling unit splits the input optical pulse into two sub-pulses, a third sub-pulse and a fourth sub-pulse. These two sub-pulses are transmitted along the third and fourth transmission optical paths of the second polarization control optical path, respectively, and are then combined into a single output optical pulse by the fourth optical coupling unit. One of the two intrinsic polarization states of the second polarization control optical path is...

[0012] The second phase modulator is disposed in the third or fourth transmission optical path of the second polarization control optical path; the second phase modulator includes a third port and a fourth port, which are respectively a forward input optical port and a reverse input optical port; the transmission optical paths connected to the second phase modulator are all coupled to the slow axis of the third and fourth ports of the second phase modulator, or are all coupled to the fast axis of the third and fourth ports of the second phase modulator; the second phase modulator performs phase modulation on the input sub-optical pulses, thereby generating a phase difference between the two sub-optical pulses.

[0013] The unequal-arm polarization control interferometer includes: a fifth optical coupling unit, a sixth optical coupling unit, a fifth transmission optical path, and a sixth 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 respectively connected to the two input ports of the sixth optical coupling unit through the fifth transmission optical path and the sixth transmission optical path, and the optical path lengths of the fifth transmission optical path and the sixth transmission optical path are unequal;

[0014] The light pulse output from the second polarization control optical path is input into the unequal-arm polarization control interferometer through the input port of the fifth optical coupling unit. The fifth optical coupling unit further splits the input light pulse into two sub-light pulses, namely the fifth sub-light pulse and the sixth sub-light pulse. These two sub-light pulses are then transmitted along the fifth and sixth transmission optical paths, respectively, and are combined into a single light pulse by the sixth optical coupling unit of the unequal-arm polarization control interferometer. One of the two intrinsic polarization states of the unequal-arm polarization control interferometer is...

[0015] Among them, the intrinsic polarization state of the first polarization control optical path The intrinsic polarization state of the second polarization control optical path The included angle between them, and the intrinsic polarization state of the first polarization control optical path. The intrinsic polarization state of the unequal-arm polarization control interferometer The angle between them is set according to the requirements of the quantum communication protocol.

[0016] According to a second aspect of this application, a time phase encoding method is provided, which implements time phase encoding using the aforementioned time phase encoding device.

[0017] According to a third aspect of this application, a quantum communication system is provided, including the time phase encoding device described above.

[0018] In summary, the time-phase encoding device, method, and quantum communication system provided in this application have at least the following beneficial effects:

[0019] This application employs a first polarization operation module, a second polarization operation module, and an unequal-arm polarization control interferometer connected in series. Each of the first and second polarization operation modules includes a polarization control optical path and a phase modulator. The unequal-arm polarization control interferometer includes a fifth optical coupling unit, a sixth optical coupling unit, and a transmission optical path with unequal optical path lengths. The application achieves this by setting the intrinsic polarization states of the polarization control optical paths in the two polarization operation modules. and The angle between them, and The intrinsic polarization state of the unequal-arm polarization control interferometer The angle between the two polarization operation modules is used to meet the requirements of various quantum communication protocols. This application uses two polarization operation modules connected in series with an unequal-arm interferometer. The two polarization operation modules can generate three sets of six polarization-coded quantum states, and then convert the polarization-coded quantum states into time-phase-coded quantum states, thereby realizing the generation of X-based / Y-based phase-based and Z-based time-based quantum states. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of this application or the technical solutions in 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 application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A structural block diagram of a time phase encoding device provided for an embodiment of this application;

[0022] Figure 2 A structural diagram of an embodiment of a time phase encoding device provided for the purposes of this application;

[0023] Figure 3 A structural diagram of a second embodiment of the polarization control optical path provided for the purposes of this application;

[0024] Figure 4 A structural diagram of a third embodiment of the polarization control optical path provided for the purposes of this application;

[0025] Figure 5 A structural diagram of a fourth embodiment of the polarization control optical path provided in this application;

[0026] Figure 6 A structural diagram of the fifth embodiment of the polarization control optical path provided in this application;

[0027] Figure 7 A structural diagram of the sixth embodiment of the polarization control optical path provided for the embodiments of this application;

[0028] Figure 8 A structural diagram of the seventh embodiment of the polarization control optical path provided for the embodiments of this application;

[0029] Figure 9 A structural diagram of a first embodiment of an unequal-arm polarization control interferometer provided for the purposes of this application;

[0030] Figure 10A structural diagram of a second embodiment of the unequal-arm polarization control interferometer provided for the purposes of this application;

[0031] Figure 11 A structural diagram of a third embodiment of an unequal-arm polarization control interferometer provided for the purposes of this application;

[0032] Figure 12 A structural diagram of a fourth embodiment of the unequal-arm polarization control interferometer provided for the purposes of this application;

[0033] Figure 13 A structural diagram of the fifth embodiment of the unequal-arm polarization control interferometer provided for the embodiments of this application;

[0034] Figure 14 A structural diagram of the sixth embodiment of the unequal-arm polarization control interferometer provided for the embodiments of this application. Detailed Implementation

[0035] To make the above and other features and advantages of this application clearer, the application is further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explanation to those skilled in the art, and are exemplary only, not restrictive.

[0036] In the following description, numerous specific details are set forth to provide a thorough understanding of this application. However, it will be apparent to those skilled in the art that the specific details are not required to practice this application. In other instances, well-known steps or operations have not been described in detail to avoid obscuring this application.

[0037] It should be noted that the time phase encoding described in this application includes phase encoding, that is, the time phase encoding is an encoding composed of any combination of quantum states of the X phase basis, Y phase basis, and Z time basis.

[0038] See attached document Figure 1 Appendix Figure 2 As shown, this application provides a time phase encoding device, such as... Figure 1 The diagram shown is a structural block diagram of the device, which includes: a first polarization operation module 100, a second polarization operation module 200, and an unequal-arm polarization control interferometer 300. The first polarization operation module 100 includes: a first polarization control optical path and a first phase modulator; the second polarization operation module 200 includes a second polarization control optical path and a second phase modulator.

[0039] In some implementations, such as Figure 2As shown, the first polarization control optical path includes: a first optical coupling unit 201a, a second optical coupling unit 201b, a first transmission optical path 204a, and a second transmission optical path 204b; the first optical coupling unit 201a and the second optical coupling unit 201b are connected through the first transmission optical path 204a and the second transmission optical path 204b.

[0040] In one exemplary embodiment, the first optical coupling unit 201a is used to split the input optical pulse into two sub-optical pulses, namely a first sub-optical pulse and a second optical pulse. The first and second optical pulses are transmitted along the first transmission optical path 204a and the second transmission optical path 204b in the first polarization control optical path, respectively, and then combined by the second optical coupling unit 201b into a single output optical pulse. The two intrinsic polarization states of the first polarization control optical path are respectively... and

[0041] In one exemplary embodiment, the first phase modulator 205 is disposed in the first transmission optical path 204a or the second transmission optical path 204b of the first polarization control optical path, such as... Figure 2 The diagram shows a first phase modulator 205 disposed in the first transmission optical path 204a; the first phase modulator 205 includes a first port and a second port, as shown... Figure 2 Ports E and F are the forward input optical port and the reverse input optical port, respectively; the transmission optical path connecting the first phase modulator 205 (e.g., ...) Figure 2 The first transmission optical path 204a) is coupled to the slow axis of port E and port F of the first phase modulator 205, or is coupled to the fast axis of port E and port F of the first phase modulator 205; the first phase modulator 205 is used to perform phase modulation on the input sub-optical pulses, so that a phase difference φ is generated between the two sub-optical pulses.

[0042] It is understood that the first phase modulator 205 also includes an interface for receiving modulated signals, which is not shown in the figure.

[0043] It should be noted that, Figure 2 The structures of the first polarization control optical path, the second polarization control optical path, and the unequal-arm polarization control interferometer shown are all examples of structures. Other examples of polarization control optical path structures will be introduced below.

[0044] In one embodiment, one of the first optical coupling unit 201a and the second optical coupling unit 201b is a polarization beam splitter, and the other of the first optical coupling unit 201a and the second optical coupling unit 201b is a polarization beam splitter or an optical coupler, wherein the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the first polarization control optical path.

[0045] like Figure 2 The structure of the first polarization control optical path included in the first polarization operation module 100 shown is a first embodiment of this application. In this embodiment, the first optical coupling unit 201a and the second optical coupling unit 201b in the first polarization control optical path are polarization beamsplitters, and the intrinsic polarization state of the polarization beamsplitter is the intrinsic polarization state of the first polarization control optical path. In this embodiment, the first optical coupling unit 201a includes three ports, namely port A, port B, and port X, where port A is the input port (also the input port of the first polarization control optical path), and ports B and X are output ports. The second optical coupling unit 201b includes three ports, namely port C, port D, and port Y, where ports C and Y are input ports, and port D is the output port (also the output port of the first polarization control optical path). Port B of the first optical coupling unit 201a and port C of the second optical coupling unit 201b are connected through the first transmission optical path 204a, and port X of the first optical coupling unit 201a and port Y of the second optical coupling unit 201b are connected through the second transmission optical path 204b.

[0046] See attached document Figure 3 The diagram illustrates a second embodiment of the structure of the first polarization control optical path. In this embodiment, the first optical coupling unit 201a and the second optical coupling unit 201b are the same polarization beamsplitter 201, while the first transmission optical path 204a and the second transmission optical path 204b are different transmission optical paths. The intrinsic polarization state of the polarization beamsplitter 201 is the intrinsic polarization state of the first polarization control optical path. The polarization beamsplitter 201 includes three ports: port A, port B, and port C. Port A serves as both the input and output port of the first polarization control optical path. The first polarization control optical path further includes two mirrors: mirror 217 and mirror 218. Mirrors 217 and 218 are connected to ports B and C of the polarization beamsplitter 201 via the first transmission optical path 204a and the second transmission optical path 204b, respectively, to reflect the light pulses input to the two mirrors back to the polarization beamsplitter 201.

[0047] See attached document Figure 4The diagram illustrates a third embodiment of the structure of the first polarization control optical path. In this embodiment, the first optical coupling unit 201a and the second optical coupling unit 201b are the same polarization beamsplitter 201, while the first transmission optical path 204a and the second transmission optical path 204b are different transmission optical paths. The intrinsic polarization state of the polarization beamsplitter 201 is the intrinsic polarization state of the first polarization control optical path. The polarization beamsplitter 201 includes four ports: port A, port B, port C, and port D. Port A is the input port of the first polarization control optical path, and port D is the output port of the first polarization control optical path. The first polarization control optical path also includes two mirrors: mirror 217 and mirror 218. Mirrors 217 and 218 are connected to ports B and C of the polarization beamsplitter 201 via the first transmission optical path 204a and the second transmission optical path 204b, respectively, to reflect the light pulses input to the two mirrors back to the polarization beamsplitter 201. In one exemplary embodiment, the above-mentioned reflectors 217 and 218 are 90° polarization state rotating reflectors, which can be 90° Faraday rotating reflectors or quarter-wave plate reflectors.

[0048] It should be noted that, in the above Figures 2-4 In one embodiment of the structure of the first polarization control optical path, the two sub-light pulses arrive at the second optical coupling unit 201b simultaneously after passing through two transmission optical paths (e.g., the first transmission optical path 204a and the second transmission optical path 204b).

[0049] See attached document Figure 5As shown, this is a fourth embodiment of the structure of the first polarization control optical path. In this embodiment, the first optical coupling unit 201a and the second optical coupling unit 201b are the same optical coupling unit, the first transmission optical path 204a and the second transmission optical path 204b are the same transmission optical path 204, and the intrinsic polarization state of the optical coupling unit is the intrinsic polarization state of the first polarization control optical path. In this embodiment, the optical coupling unit is a polarization beamsplitter 201, which includes three ports: port A, port B, and port C. Port A of the polarization beamsplitter 201 serves as both the input and output port of the first polarization control optical path. Ports B and C of the polarization beamsplitter 201 are connected via a transmission optical path 204. The first polarization control optical path also includes an optical circulator (not shown in the figure), which is positioned at the front end of port A. The optical circulator includes three ports: a first port, a second port, and a third port. The first port of the optical circulator is the input port of the first polarization control optical path, and the third port is the output port. The second port of the optical circulator is connected to port A. Light pulses input from the first port of the optical circulator are output through the second port, and light pulses input from the second port are output through the third port. In this embodiment, the intrinsic polarization state of the polarization beamsplitter 201 is the intrinsic polarization state of the optical coupling unit.

[0050] See attached document Figure 6The diagram shows a fifth embodiment of the structure of the first polarization control optical path. In this embodiment, the first optical coupling unit 201a and the second optical coupling unit 201b are the same optical coupling unit, the first transmission optical path 204a and the second transmission optical path 204b are the same transmission optical path 204, and the intrinsic polarization state of the optical coupling unit is the intrinsic polarization state of the first polarization control optical path. The optical coupling unit includes: a polarization beamsplitter 201, a first polarizer 202, and a second polarizer 203. The polarization beamsplitter 201 includes four ports: port A, port B, port C, and port D. Port A of the polarization beamsplitter 201 is the input port of the first polarization control optical path, and port D of the polarization beamsplitter 201 is the output port of the first polarization control optical path. Ports B and C of the polarization beamsplitter 201 are connected to the ports on the first side of the first polarizer 202 and the first side of the second polarizer 203, respectively. The ports on the second side of the first polarizer 202 and the second side of the second polarizer 203 are connected via optical transmission path 204. The angle between the polarization direction of the first polarizer 202 and one intrinsic polarization state of the polarization beam splitter 201 is θ, and the angle between the polarization direction of the second polarizer 203 and another intrinsic polarization state of the polarization beam splitter 201 is δ. Wherein, θ and δ ≠ 90°, and n is an integer. The angle between the polarization direction of the first polarizer 202 and the polarization direction of the second polarizer 203 is ω, where 0 ≤ ω ≤ 2π. In this embodiment, the intrinsic polarization state of the polarization beam splitter 201 is the intrinsic polarization state of the optical coupling unit.

[0051] See attached document Figure 7 The diagram shows a sixth embodiment of the structure of the first polarization control optical path. In this embodiment, the first optical coupling unit 201a and the second optical coupling unit 201b are the same optical coupling unit, the first transmission optical path 204a and the second transmission optical path 204b are the same transmission optical path 204, and the intrinsic polarization state of the optical coupling unit is the intrinsic polarization state of the first polarization control optical path. The optical coupling unit includes: an optical beamsplitter 201, a first polarizer 202, and a second polarizer 203. The optical beamsplitter 201 includes at least three ports, namely port A, port B, and port C. Port A of the optical beamsplitter 201 is the input port of the first polarization control optical path; ports B and C of the optical beamsplitter 201 are connected to the ports on the first side of the first polarizer 202 and the first side of the second polarizer 203, respectively; the ports on the second side of the first polarizer 202 and the second side of the second polarizer 203 are connected through the transmission optical path 204. The polarization direction of the first polarizer 202 is... The polarization direction of the second polarizer 203 is The direction of the first polarizer 202 The polarization direction of the second polarizer 203 Mutually orthogonal; in this embodiment, the deflection direction of the first deflector 202 The polarization direction of the second polarizer 203 This refers to the intrinsic polarization state of the optical coupling unit.

[0052] See attached document Figure 8 The diagram shows a seventh embodiment of the structure of the first polarization control optical path. In this embodiment, the first optical coupling unit 201a and the second optical coupling unit 201b are the same optical coupling unit, the first transmission optical path 204a and the second transmission optical path 204b are the same transmission optical path 204, and the intrinsic polarization state of the optical coupling unit is the intrinsic polarization state of the first polarization control optical path. This embodiment is similar to... Figure 7 The difference in the embodiment shown is that the optical beam splitter 201 also includes a port D; the port D of the optical beam splitter 201 is the output port of the first polarization control optical path.

[0053] exist Figures 5-8 In the corresponding structure, the two sub-light pulses from the polarization-splitting beam in the polarization control optical path travel through identical optical paths when combined, exhibiting self-compensation against environmental interference and stably generating three sets of six polarization-coded quantum states. This results in the generation of time-phase-coded quantum states also possessing the advantage of high stability against interference. Furthermore, in this structure, the first phase modulator in the polarization control optical path is subjected to a high-frequency modulation signal exceeding a specified threshold, making the first phase modulator non-reciprocal in modulating the phases of the forward and reverse input sub-light pulses. Thus, the first phase modulator can effectively modulate the phase of the sub-light pulse input from the forward input optical port but cannot effectively modulate the phase of the sub-light pulse input from the reverse input optical port. Consequently, when the sub-light pulses input from the forward and reverse input optical ports pass through the high-frequency modulated phase modulator, the sub-light pulse input from the forward input optical port receives phase modulation, while the sub-light pulse input from the reverse input optical port does not, creating a phase difference between the two sub-light pulses. This enables time-phase quantum state encoding at speeds of 10 GHz or higher. The high-frequency modulation signal is, for example, a modulation signal of not less than 10 GHz. When a high-frequency modulation signal with a frequency higher than a specified threshold is applied to the phase modulator, the phase modulator may have multiple sub-optical pulses input to the forward input optical port and multiple sub-optical pulses input to the reverse input optical port at the same time.

[0054] In some implementations, such as Figure 2 As shown, the second polarization control optical path includes: a third optical coupling unit 206a, a fourth optical coupling unit 206b, a third transmission optical path 209a, and a fourth transmission optical path 209b; the third optical coupling unit 206a and the fourth optical coupling unit 206b are connected through the third transmission optical path 209a and the fourth transmission optical path 209b.

[0055] In one exemplary embodiment, the first polarization control optical path inputs the output light pulse into the second polarization control optical path through the third optical coupling unit 206a. The third optical coupling unit 206a splits the input light pulse into two sub-light pulses, namely the third sub-light pulse and the fourth sub-light pulse. The third sub-light pulse and the fourth sub-light pulse are transmitted along the third transmission optical path 209a and the fourth transmission optical path 209b in the second polarization control optical path, respectively, and are then combined into a single light pulse by the fourth optical coupling unit 206b for output. The two intrinsic polarization states of the second polarization control optical path are respectively... and

[0056] In one exemplary embodiment, the second phase modulator 210 is disposed in the third transmission optical path 209a or the fourth transmission optical path 209b of the second polarization control optical path; the second phase modulator 210 includes a third port and a fourth port, such as Figure 2 Ports E' and F' shown are the forward input optical port and the reverse input optical port, respectively; the transmission optical path connecting the second phase modulator 210 (e.g., ...) Figure 2 The third transmission optical path 209a) is coupled to the slow axis of the third port E' and the fourth port F' of the second phase modulator 210, or is coupled to the fast axis of the third port E' and the fourth port F' of the second phase modulator 210; the second phase modulator 210 performs phase modulation on the input sub-optical pulses, so that a phase difference is generated between the two sub-optical pulses. Similarly, the second phase modulator 210 also includes an interface for receiving modulated signals.

[0057] It should be noted that the second polarization control optical path can also be as follows: Figures 2-8 The structure in any of the embodiments is the same as that in the first polarization control optical path, and the structure of the second polarization control optical path can be the same as or different from that in the first polarization control optical path.

[0058] In some embodiments, the device may further include: a third phase modulator, which is disposed in the transmission optical path of the first polarization control optical path, connected in series with the first phase modulator 205 in the same transmission optical path 204a, or disposed with the first phase modulator 205 in different transmission optical paths in the first transmission optical path 204a and the second transmission optical path 204b, respectively; the third phase modulator includes a fifth port and a sixth port, which are a forward input optical port and a reverse input optical port, respectively; the transmission optical paths connected to the third phase modulator are all coupled to the slow axis of the fifth and sixth ports of the third phase modulator, or are all coupled to the fast axis of the fifth and sixth ports of the third phase modulator; the third phase modulator performs phase modulation on the input sub-light pulses, so that a phase difference is generated between the two sub-light pulses.

[0059] Alternatively, the third phase modulator is disposed in the transmission optical path of the second polarization control optical path, connected in series with the second phase modulator 210 in the same transmission optical path 209a, or disposed with the second phase modulator 210 in different transmission optical paths in the third transmission optical path 209a and the fourth transmission optical path 209b, respectively; the third phase modulator includes a fifth port and a sixth port, which are the forward input optical port and the reverse input optical port, respectively, and the transmission optical paths connected to the third phase modulator are all coupled to the slow axis of the fifth and sixth ports of the third phase modulator, or are all coupled to the fast axis of the fifth and sixth ports of the third phase modulator; the third phase modulator performs phase modulation on the input sub-light pulses, so that a phase difference is generated between the two sub-light pulses.

[0060] Similarly, the third phase modulator also includes an interface for receiving modulated signals.

[0061] After the first phase modulator, the second phase modulator, and / or the third phase modulator are subjected to the high-frequency modulation signal, the modulation phase of the forward and reverse input sub-optical pulses is non-reciprocal. This ensures effective phase modulation of the sub-optical pulse input from the forward input optical port, but ineffective phase modulation of the sub-optical pulse input from the reverse input optical port. The ratio of the modulation efficiency of the sub-optical pulse input from the forward input optical port to that of the sub-optical pulse input from the reverse input optical port is not less than a preset threshold, such as 10 dB. Therefore, when the sub-optical pulses input from the forward and reverse input optical ports pass through the high-frequency modulation phase modulator, the sub-optical pulse input from the forward input optical port receives phase modulation, while the sub-optical pulse input from the reverse input optical port does not, creating a phase difference between the two sub-optical pulses. This enables time-phase quantum state encoding at speeds of 10 GHz or higher.

[0062] This application reduces the number of phase types modulated by a single phase modulator by combining the first phase modulator, the second phase modulator, and the third phase modulator. For example, a single phase modulator can modulate two signal states using only digital modulation, thereby reducing the implementation difficulty of the single phase modulator drive circuit.

[0063] See attached document Figure 2As shown, in some embodiments, the unequal-arm polarization control interferometer 300 includes: a fifth optical coupling unit 211, a sixth optical coupling unit 214, a fifth transmission optical path 212, and a sixth transmission optical path 213; the fifth optical coupling unit 211 includes at least three ports, one input port and two output ports; the sixth optical coupling unit 214 includes at least three ports, two input ports and one output port; the two output ports of the fifth optical coupling unit 211 are respectively connected to the two input ports of the sixth optical coupling unit 214 through the fifth transmission optical path 212 and the sixth transmission optical path 213, and the optical paths of the fifth transmission optical path 212 and the sixth transmission optical path 213 are not equal.

[0064] In one exemplary embodiment, the light pulse output from the second polarization control optical path is input into the unequal-arm polarization control interferometer 300 via the fifth optical coupling unit 211. The fifth optical coupling unit 211 further splits the input light pulse into two sub-light pulses, namely the fifth sub-light pulse and the sixth sub-light pulse. The fifth and sixth sub-light pulses are transmitted along the fifth transmission optical path 212 and the sixth transmission optical path 213, respectively, and then combined into a single light pulse by the sixth optical coupling unit 214 of the unequal-arm polarization control interferometer 300. The two intrinsic polarization states of the unequal-arm polarization control interferometer 300 are respectively... and

[0065] like Figure 9 The diagram shows a schematic representation of an embodiment of the unequal-arm polarization control interferometer 300. In this embodiment, the fifth optical coupling unit is a polarization beamsplitter 901, and the sixth optical coupling unit is a polarization beam combiner 902. The intrinsic polarization state of the polarization beamsplitter 901 is the intrinsic polarization state of the unequal-arm polarization control interferometer 300. The polarization beamsplitter 901 and the polarization beam combiner 902 are connected via a fifth transmission optical path 903 and a sixth transmission optical path 904, respectively, with unequal optical path lengths.

[0066] like Figure 10The diagram shows another embodiment of the unequal-arm polarization control interferometer 300. In this embodiment, the fifth optical coupling unit is a polarization beamsplitter 1001, and the sixth optical coupling unit is an optical coupler 1002. The intrinsic polarization state of the polarization beamsplitter 1001 is the intrinsic polarization state of the unequal-arm polarization control interferometer 300. The polarization beamsplitter 1001 and the optical coupler 1002 are connected through a fifth transmission optical path 1003 and a sixth transmission optical path 1004 with unequal optical path lengths, respectively. Optionally, the fifth transmission optical path 1003 or the sixth transmission optical path 1004 is a 90° twisted polarization-maintaining fiber, or the unequal arm polarization control interferometer 300 further includes: a 90° polarization state rotator 1005, which is disposed on the fifth transmission optical path 1003 or the sixth transmission optical path 1004 and is used to rotate the polarization state of the passing sub-light pulse by 90°. The 90° polarization state rotator 1005 can be a half-wave plate or a 90° Faraday rotator.

[0067] like Figure 11 The diagram shows a schematic representation of another embodiment of the unequal-arm polarization control interferometer 300. In this embodiment, the fifth optical coupling unit is an optical coupler 1101, and the sixth optical coupling unit is a polarization combiner 1102. The intrinsic polarization state of the polarization combiner 1102 is the intrinsic polarization state of the unequal-arm polarization control interferometer 300. The optical coupler 1101 and the polarization combiner 1102 are connected via a fifth transmission optical path 1103 and a sixth transmission optical path 1104, respectively, with unequal optical path lengths.

[0068] like Figure 12The diagram shows another embodiment of the unequal-arm polarization control interferometer 300. In this embodiment, the fifth optical coupling unit is an optical coupler 1201, and the sixth optical coupling unit is an optical coupler 1202. The unequal-arm polarization control interferometer further includes two polarizers, polarizer 1203 and polarizer 1204, which are respectively disposed on the fifth transmission optical path 1205 and the sixth transmission optical path 1206. One output port of the optical coupler 1201 is connected to the first port of the polarizer 1203, and the polarizer 1203 is used to polarize one sub-light pulse output by the optical coupler 1201. The other output port of the optical coupler 1201 is connected to the first port of the polarizer 1204, and the polarizer 1204 is used to polarize another sub-light pulse output by the optical coupler 1201. The polarization directions of the two polarizers 1203 and 1204 are orthogonal to each other. The other ports of polarizer 1203 and polarizer 1204 are connected to optical coupler 1202 via fifth transmission optical path 1205 and sixth transmission optical path 1206, respectively. In this embodiment, the polarization direction of the two polarizers is the intrinsic polarization state direction of the unequal-arm polarization control interferometer. Optionally, the fifth transmission optical path 1205 or the sixth transmission optical path 1206 is a 90° twisted polarization-maintaining fiber, or the unequal-arm polarization control interferometer 300 further includes a 90° polarization state rotator 1207, which is disposed on the fifth transmission optical path 1205 or the sixth transmission optical path 1206 and is used to rotate the polarization state of the passing sub-light pulse by 90°. The 90° polarization state rotator 1207 can be a half-wave plate or a 90° Faraday rotator.

[0069] like Figure 13The diagram shows a schematic representation of another embodiment of the unequal-arm polarization control interferometer 300. In this embodiment, the fifth optical coupling unit and the sixth optical coupling unit are the same polarization beamsplitter 1301, and the intrinsic polarization state of the polarization beamsplitter 1301 is the intrinsic polarization state of the unequal-arm polarization control interferometer. The unequal-arm polarization control interferometer 300 further includes two mirrors, mirror 1302 and mirror 1303, respectively. The two output ports of the polarization beamsplitter 1301 are connected to one end of the fifth transmission optical path 1304 and one end of the sixth transmission optical path 1305, respectively. The two mirrors 1302 and 1303 are connected to the other ends of the fifth transmission optical path 1304 and the sixth transmission optical path 1305, respectively. The two mirrors 1302 and 1303 are used to reflect the input sub-light pulses back to the polarization beamsplitter 1301. Optionally, the two reflectors 1302 and 1303 can be quarter-wave plate reflectors or 90° Faraday rotation reflectors, used to rotate the polarization state of the input sub-light pulse by 90°. Alternatively, the two reflectors 1302 and 1303 can be polarization rotation reflectors, used to rotate the polarization state of the input sub-light pulse by 45° or other preset angles.

[0070] It should be noted that the polarization beam splitter 1301 may include three ports or four ports.

[0071] like Figure 14 The diagram shows another embodiment of the unequal-arm polarization control interferometer 300. In this embodiment, the fifth optical coupling unit and the sixth optical coupling unit are the same optical coupler 1401. The unequal-arm polarization control interferometer 300 also includes two mirrors 1402 and 1403 and two polarizers 1404 and 1405.

[0072] The two output ports of the optical coupler 1401 are connected to one end of the fifth transmission optical path and one end of the sixth transmission optical path, respectively. The two mirrors 1402 and 1403 are connected to the other ends of the fifth transmission optical path and the sixth transmission optical path, respectively. The two polarizers 1404 and 1405 are respectively disposed on the fifth transmission optical path and the sixth transmission optical path, and the polarization directions of the two polarizers 1404 and 1405 are orthogonal to each other. The polarization directions of the two polarizers 1404 and 1405 are the intrinsic polarization state directions of the unequal arm polarization control interferometer.

[0073] In some embodiments, the device may further include: an optical polarizer connected to the output port L of the sixth optical coupling unit, used to polarize the optical pulses output by the sixth optical coupling unit.

[0074] In some embodiments, the device further includes a quarter-wave plate disposed between the second polarization control optical path and the unequal-arm polarization control interferometer 300; in one embodiment, the intrinsic polarization direction of the quarter-wave plate is... and The intrinsic polarization direction and The included angle between them can be k·45°, where k is an integer.

[0075] In some implementations, the intrinsic polarization state of the first polarization control optical path The intrinsic polarization state of the second polarization control optical path The angle between them is n·22.5°, where n is an integer.

[0076] In some embodiments, the intrinsic polarization state of the first polarization control optical path The intrinsic polarization state of the second polarization control optical path The included angle is achieved by rotating at least one of the two polarization control optical paths; and / or

[0077] The device further includes a polarization state rotator, which is disposed between two polarization control optical paths and adjusts the angle between the intrinsic polarization states of the two polarization control optical paths.

[0078] In some embodiments, the device further includes an optical isolation unit, which is an optical isolator or an optical circulator, and is disposed between the first polarization operation module and the second polarization operation module.

[0079] In one exemplary embodiment, the intrinsic polarization state of the first polarization control optical path The intrinsic polarization states of the unequal-arm polarization control interferometer 300 The angle between them is m·22.5°, where m is an integer.

[0080] In one exemplary embodiment, the intrinsic polarization state of the first polarization control optical path The intrinsic polarization states of an unequal-arm polarization-controlled interferometer The included angle between them is achieved by rotating at least one of the first polarization control optical path and the unequal-arm polarization control interferometer; and / or

[0081] The device further includes: a polarization state rotator, which is disposed between the first polarization control optical path and the unequal-arm polarization control interferometer, and adjusts the angle between the intrinsic polarization state of the first polarization control optical path and the intrinsic polarization state of the unequal-arm polarization control interferometer by means of the polarization state rotator.

[0082] In some embodiments, the polarization state of the optical pulse of the input first polarization control light is Alternatively, the polarization state of the input light pulse for the first polarization control light is... Alternatively, the polarization state of the optical pulse input to the first polarization control optical path is... or Where n is an integer, and These are the two intrinsic polarization states of the first polarization control optical path, where β is any value from 0 to 2π.

[0083] For example, the polarization state of the optical pulse input to the time phase encoding device (first polarization control optical path) can be 45° linear polarization, -45° linear polarization, left-hand circular polarization, or right-hand circular polarization.

[0084] In some embodiments, by combining and modulating the first phase modulator 205 and the second phase modulator 210, the output optical pulse can achieve a horizontal and vertical polarization base. ±45° polarization base or left- or right-handed circular polarization base Multiple combinations of polarization quantum states are generated. The polarization-encoded quantum state is converted into a time-phase-encoded quantum state through an unequal-arm polarization control interferometer, thereby realizing the generation of X-based / Y-based phase-based and Z-based time-based quantum states.

[0085] In some implementations, a phase difference φ is generated between the first and second sub-optical pulses, and a phase difference is generated between the third and fourth sub-optical pulses. Determined based on the coding requirements of the quantum communication protocol.

[0086] For example, when the intrinsic polarization state of the first polarization control optical path The intrinsic polarization state of the second polarization control optical path The included angle between them is 45°, and the intrinsic polarization state of the first polarization control optical path The intrinsic polarization states of an unequal-arm polarization-controlled interferometer When the included angle between them is 0°, and both the first and second polarization control optical paths use a polarization beam splitting unit composed of a four-port polarization beam splitter and two optical polarizers, the first polarization control optical path will input... The output remains unchanged in polarization state, while the input... The polarization state also remains unchanged at the output, meaning the relationship between the input and output of the first polarization control optical path is as follows: (The negative sign indicates that it was taken into consideration) (Due to the polarization state being reflected twice by the polarization beam splitter); the second polarization control optical path also maintains its intrinsic polarization state at output. When the polarization state of the light pulse input to the first polarization control optical path is 45° linearly polarized, if the first phase modulator 205 randomly modulates 0°, 90°, 180°, or 270°, i.e., the phase difference φ is modulated to 0°, 90°, 180°, or 270°, and the second phase modulator 210 modulates 0° (i.e., no modulation), then a ±45° polarization base can be prepared. and left-hand and right-hand circular polarization bases Two sets of four polarization states can be used to prepare four phase states of X-based / Y-based after polarization-phase encoding by an unequal-arm polarization control interferometer 300.

[0087] If the first phase modulator 205 randomly modulates 0°, 90°, or 180°, that is, the phase difference φ is modulated to 0°, 90°, or 180°, and the second phase modulator 210 randomly modulates 90° or 270°, that is, the phase difference φ is modulated to 0°, 90°, or 180°, then the second phase modulator 210 randomly modulates 9 By modulating the polarization to 90° or 270°, horizontal and vertical polarization bases can be prepared. and ±45° polarization base Two sets of four polarization states based on polarization can be used to prepare two phase states based on the X-base and two time bit states based on the Z-base after polarization-to-time-phase encoding by an unequal-arm polarization control interferometer 300.

[0088] If the first phase modulator 205 randomly modulates 90° or 270°, and the second phase modulator 210 modulates 0° or 90°, then a horizontal and vertical polarization base can be prepared. and left-hand and right-hand circular polarization bases Two sets of four polarization states based on polarization can be used to prepare two phase states based on Y and two time bit states based on Z after polarization-phase encoding by an unequal-arm polarization control interferometer 300.

[0089] If the first phase modulator 205 is randomly modulated to 0°, 90°, 180°, or 270°, and the second phase modulator 210 is randomly modulated to 0° or 90°, then a horizontal and vertical polarization base can be prepared. ±45° polarization base and left-hand and right-hand circular polarization bases With three bases and six polarization states, after polarization-to-time-phase encoding using an unequal-arm polarization-controlled interferometer, four phase states (X-based / Y-based) and two time-bit states (Z-based) can be prepared.

[0090] If the first phase modulator 205 is randomly modulated to 0°, 90°, or 180°, and the second phase modulator 210 is randomly modulated to 0° or 90°, then a horizontal and vertical polarization base can be prepared. ±45° polarization base and left-hand and right-hand circular polarization bases With three bases and four polarization states, polarization-to-time-phase encoding can be achieved using an unequal-arm polarization-controlled interferometer, which can prepare three bases and four time-phase states: X-based, Y-based, and Z-based.

[0091] In some implementations, the time-phase encoding device of this application can also be used to implement the time-phase decoding process, depending on the requirements of quantum communication.

[0092] The time-phase encoding device of this application includes a first polarization operation module, a second polarization operation module, and an unequal-arm polarization control interferometer connected in series. Each of the first and second polarization operation modules includes a polarization control optical path and a phase modulator. The unequal-arm polarization control interferometer includes a fifth optical coupling unit, a sixth optical coupling unit, and a transmission optical path with unequal optical path lengths. The device achieves this by setting the intrinsic polarization states of the polarization control optical paths in the two polarization operation modules. and The angle between them, and The intrinsic polarization state of the unequal-arm polarization control interferometer The included angle between the two polarization operation modules is used to meet the requirements of various quantum communication protocols. The device described in this application uses two polarization operation modules connected in series with an unequal-arm interferometer. The two polarization operation modules can generate three sets of six polarization-coded quantum states, and then convert the polarization-coded quantum states into time-phase-coded quantum states, thereby realizing the generation of X-based / Y-based phase-based and Z-based time-based quantum states.

[0093] According to this application, a time phase encoding method is provided, which uses the aforementioned time phase encoding device to implement time phase encoding.

[0094] According to this application, a quantum communication system is provided, including the time phase encoding device described above.

[0095] The quantum communication system can be a discrete-variable quantum communication system or a continuous-variable quantum communication system. The protocols of the quantum communication system include, but are not limited to, BB84, BBM92, E91, MDI, TF, frame-independent, and coherent state protocols.

[0096] It should be understood that the specific features, operations and details described herein with respect to the apparatus of this application can also be similarly applied to the methods and systems of this application, or vice versa.

[0097] 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.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 application.

Claims

1. A time phase encoding device, characterized in that, include: The system comprises a first polarization operation module, a second polarization operation module, and an unequal-arm polarization control interferometer connected in series. The first polarization operation module includes a first polarization control optical path and a first phase modulator. The second polarization operation module includes a second polarization control optical path and a second phase modulator. The first 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 first optical coupling unit is used to split the input optical pulse into two sub-optical pulses, namely a first sub-optical pulse and a second optical pulse. The first and second optical pulses are transmitted along the first and second transmission optical paths in the first polarization control optical path, respectively, and then combined into a single optical pulse by the second optical coupling unit for output. One of the two intrinsic polarization states of the first polarization control optical path is... The first phase modulator is disposed in the first transmission optical path or the second transmission optical path of the first polarization control optical path; the first 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 transmission optical paths connected to the first phase modulator are all coupled to the slow axis of the first port and the second port of the first phase modulator, or are all coupled to the fast axis of the first port and the second port of the first phase modulator; the first phase modulator is used to perform phase modulation on the input sub-optical pulses, so that a phase difference φ is generated between the two sub-optical pulses. The second polarization control optical path includes: 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 and the fourth optical coupling unit are connected through the third transmission optical path and the fourth transmission optical path; The first polarization control optical path outputs an optical pulse, which is then input into the second polarization control optical path via the third optical coupling unit. The third optical coupling unit splits the input optical pulse into two sub-pulses, a third sub-pulse and a fourth sub-pulse. These two sub-pulses are transmitted along the third and fourth transmission optical paths of the second polarization control optical path, respectively, and are then combined into a single output optical pulse by the fourth optical coupling unit. One of the two intrinsic polarization states of the second polarization control optical path is... The second phase modulator is disposed in the third or fourth transmission optical path of the second polarization control optical path; the second phase modulator includes a third port and a fourth port, which are respectively a forward input optical port and a reverse input optical port; the transmission optical paths connected to the second phase modulator are all coupled to the slow axis of the third and fourth ports of the second phase modulator, or are all coupled to the fast axis of the third and fourth ports of the second phase modulator; the second phase modulator performs phase modulation on the input sub-optical pulses, thereby generating a phase difference between the two sub-optical pulses. The unequal-arm polarization control interferometer includes: a fifth optical coupling unit, a sixth optical coupling unit, a fifth transmission optical path, and a sixth 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 respectively connected to the two input ports of the sixth optical coupling unit through the fifth transmission optical path and the sixth transmission optical path, and the optical path lengths of the fifth transmission optical path and the sixth transmission optical path are unequal; The light pulse output from the second polarization control optical path is input into the unequal-arm polarization control interferometer through the input port of the fifth optical coupling unit. The fifth optical coupling unit further splits the input light pulse into two sub-light pulses, namely the fifth sub-light pulse and the sixth sub-light pulse. These two sub-light pulses are then transmitted along the fifth and sixth transmission optical paths, respectively, and are combined into a single light pulse by the sixth optical coupling unit of the unequal-arm polarization control interferometer. One of the two intrinsic polarization states of the unequal-arm polarization control interferometer is... Among them, the intrinsic polarization state of the first polarization control optical path The intrinsic polarization state of the second polarization control optical path The included angle between them, and the intrinsic polarization state of the first polarization control optical path. The intrinsic polarization states of the unequal-arm polarization control interferometer The angle between them is set according to the requirements of the quantum communication protocol.

2. The apparatus according to claim 1, characterized in that, The device further includes: a third phase modulator, The third phase modulator is disposed in the transmission optical path of the first polarization control optical path, either in series with the first phase modulator in the same transmission optical path, or disposed in different transmission optical paths in the first and second transmission optical paths respectively. or, The third phase modulator is disposed in the transmission optical path of the second polarization control optical path, either in series with the second phase modulator in the same transmission optical path, or disposed with the second phase modulator in different transmission optical paths in the third and fourth transmission optical paths, respectively. The third phase modulator includes a fifth port and a sixth port, which are the forward input optical port and the reverse input optical port, respectively. The transmission optical paths connected to the third phase modulator are all coupled to the slow axis of the fifth and sixth ports of the third phase modulator, or all are coupled to the fast axis of the fifth and sixth ports of the third phase modulator. The third phase modulator performs phase modulation on the input sub-optical pulses, so that a phase difference is generated between the two sub-optical pulses.

3. The apparatus according to claim 1, characterized in that, One of the first optical coupling unit and the second optical coupling unit is a polarization beamsplitter, and the other of the first optical coupling unit and the second optical coupling unit is a polarization beamsplitter or an optical coupler, wherein the intrinsic polarization state of the polarization beamsplitter is the intrinsic polarization state of the first polarization control optical path; and / or, The third optical coupling unit and the fourth optical coupling unit are both polarization beam splitters. The other of the third optical coupling unit and the fourth optical coupling unit is a polarization beam splitter or an optical coupler. The intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the second polarization control optical path.

4. The apparatus according to claim 1, characterized in that, The first optical coupling unit and the second optical coupling unit are the same polarization beam splitter, and the first polarization control optical path further includes: two mirrors. 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 first polarization control optical path; and / or, The third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter, and the second polarization control optical path also includes two mirrors. The two reflectors are respectively connected to the third transmission optical path and the fourth 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 second polarization control optical path.

5. The apparatus according to claim 4, characterized in that, The two reflectors are 90° polarization state rotating reflectors.

6. The apparatus according to claim 1, characterized in that, The first optical coupling unit and the second optical coupling unit are the same optical coupling 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 optical coupling unit is the intrinsic polarization state of the first polarization control optical path; and / or, The third optical coupling unit and the fourth optical coupling unit are the same optical coupling unit, the third transmission optical path and the fourth transmission optical path are the same transmission optical path, and the intrinsic polarization state of the optical coupling unit is the intrinsic polarization state of the second polarization control optical path.

7. The apparatus according to claim 6, characterized in that, The optical coupling unit in the first polarization control optical path and / or the second polarization control optical path is a polarization beam splitter. The polarization beam splitter 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 first polarization control optical path and / or the second polarization control optical path. The second port and the third port of the polarization beam splitter are connected through a transmission optical path. The intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the optical coupling unit.

8. The apparatus according to claim 6, characterized in that, The optical coupling unit in the first polarization control optical path and / or the second polarization control optical path 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 first polarization control optical path and / or the second polarization control optical path, and the fourth port of the polarization beam splitter is the output port of the first polarization control optical path and / or the second 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 ports on the second side of the second polarizer are connected through a 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. 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 optical coupling unit.

9. The apparatus according to claim 6, characterized in that, The optical coupling unit in the first polarization control optical path and / or the second polarization control optical path 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 first polarization control optical path and / or the second polarization control optical path. The second and third ports of the optical beamsplitter 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 ports on the second side of the second polarizer are connected through a 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 This refers to the intrinsic polarization state of the optical coupling unit.

10. The apparatus according to claim 9, characterized in that, The optical beam splitter also includes a fourth port; The fourth port of the optical beam splitter is the output port of the first polarization control optical path and / or the second polarization control optical path.

11. The apparatus according to any one of claims 6 to 10, characterized in that, After the first phase modulator and / or the second phase modulator apply a high-frequency modulation electrical signal with a frequency higher than a specified threshold, they operate in a non-reciprocal state, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is not less than a preset threshold.

12. The apparatus according to claim 1, characterized in that, The fifth optical coupling unit is a polarization beam splitter, the sixth 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 unequal arm polarization control interferometer.

13. The apparatus according to claim 1, characterized in that, The fifth optical coupling unit is a polarization beam splitter, the sixth optical coupling unit is an optical coupler, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the unequal arm polarization control interferometer.

14. The apparatus according to claim 1, characterized in that, The fifth optical coupling unit is an optical coupler, and the sixth optical coupling unit is a polarization beam combiner. The intrinsic polarization state of the polarization beam combiner is the intrinsic polarization state of the unequal arm polarization control interferometer.

15. The apparatus according to claim 1, characterized in that, The fifth optical coupling unit is an optical coupler, the sixth optical coupling unit is an optical coupler, and the unequal-arm polarization control interferometer further includes two polarizers. The two polarizers are respectively disposed on the fifth and sixth transmission optical paths. The polarization directions of the two polarizers are orthogonal to each other, and the polarization directions of the two polarizers are the intrinsic polarization state directions of the unequal arm polarization control interferometer.

16. The apparatus according to claim 1, characterized in that, The fifth optical coupling unit and the sixth optical coupling unit are the same polarization beam splitter. The unequal-arm polarization control interferometer also includes two mirrors. The two output ports of the polarization beam splitter are respectively connected to one end of the fifth transmission optical path and one end of the sixth transmission optical path, and the two reflectors are respectively connected to the other end of the fifth transmission optical path and the other end of the sixth transmission optical path. The intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the unequal arm polarization control interferometer.

17. The apparatus according to claim 16, characterized in that, The two reflectors are either quarter-wave plate reflectors or 90° Faraday rotation reflectors.

18. The apparatus according to claim 1, characterized in that, The fifth optical coupling unit and the sixth optical coupling unit are the same optical coupler. The unequal-arm polarization control interferometer also includes two mirrors and two polarizers. The two output ports of the optical coupler are respectively connected to one end of the fifth transmission optical path and one end of the sixth transmission optical path, and the two mirrors are respectively connected to the other end of the fifth transmission optical path and the other end of the sixth transmission optical path; the two polarizers are respectively disposed on the fifth transmission optical path and the sixth transmission optical path, and the polarization directions of the two polarizers are orthogonal to each other; the polarization directions of the two polarizers are the intrinsic polarization state directions of the unequal arm polarization control interferometer.

19. The apparatus according to claim 13 or 15, characterized in that, The fifth or sixth transmission optical path is a 90° twisted polarization-maintaining fiber, or... The unequal-arm polarization control interferometer also includes a 90° polarization state rotator. The 90° polarization state rotator is disposed on the fifth or sixth transmission optical path and is used to rotate the polarization state of the passing sub-light pulse by 90°.

20. The apparatus according to any one of claims 12 to 18, characterized in that, The device also includes: a polarizer; The polarizer is located at the output port of the unequal-arm polarization control interferometer and is used to polarize the light pulses output by the unequal-arm polarization control interferometer.

21. The apparatus according to claim 1, characterized in that, The device further includes: A quarter-wave plate is positioned between the second polarization control optical path and the unequal-arm polarization control interferometer.

22. The apparatus according to claim 1, characterized in that, Intrinsic polarization state of the first polarization control optical path The intrinsic polarization state of the second polarization control optical path The angle between them is n·22.5°, where n is an integer.

23. The apparatus according to claim 22, characterized in that, Intrinsic polarization state of the first polarization control optical path The intrinsic polarization state of the second polarization control optical path The included angle is achieved by rotating at least one of the two polarization control optical paths; and / or The device further includes a polarization state rotator, which is disposed between two polarization control optical paths and adjusts the angle between the intrinsic polarization states of the two polarization control optical paths.

24. The apparatus according to claim 1, characterized in that, The device further includes an optical isolation unit, which is an optical isolator or an optical circulator, and is disposed between the first polarization operation module and the second polarization operation module.

25. The apparatus according to claim 1 or 22, characterized in that, Intrinsic polarization state of the first polarization control optical path The intrinsic polarization states of an unequal-arm polarization-controlled interferometer The angle between them is m·22.5°, where m is an integer.

26. The apparatus according to claim 25, characterized in that, Intrinsic polarization state of the first polarization control optical path The intrinsic polarization states of an unequal-arm polarization-controlled interferometer The included angle between them is achieved by rotating at least one of the first polarization control optical path and the unequal-arm polarization control interferometer; and / or The device further includes a polarization state rotator, which is disposed between the first polarization control optical path and the unequal-arm polarization control interferometer, and adjusts the angle between the intrinsic polarization state of the first polarization control optical path and the intrinsic polarization state of the unequal-arm polarization control interferometer by means of the polarization state rotator.

27. The apparatus according to claim 1, characterized in that, The polarization state of the optical pulse input to the first polarization control optical path is or, The polarization state of the optical pulse input to the first polarization control optical path is or, The polarization state of the optical pulse input to the first polarization control optical path is or Where n is an integer, and These are the two intrinsic polarization states of the first polarization control optical path, where β is any value from 0 to 2π.

28. The apparatus according to claim 27, characterized in that, The polarization state of the optical pulse input to the first polarization control optical path is 45° linear polarization, -45° linear polarization, left-hand circular polarization, or right-hand circular polarization.

29. A time phase encoding method, characterized in that, Time phase encoding is implemented using the time phase encoding device according to any one of claims 1 to 28.

30. A quantum communication system, characterized in that, Includes the time phase encoding device according to any one of claims 1 to 28.

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