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

Abstract

The present application relates to the technical fields of quantum communications and optical quantum encoding, and discloses a quantum state encoding apparatus and method, and a software-defined quantum communication system. The quantum state encoding apparatus comprises: a polarization encoding unit, a first optical coupling unit, an unequal-arm polarization control interferometer, a first transmission optical path, and a second optical coupling unit; the polarization encoding unit is configured to generate an optical pulse of a polarization-encoded quantum state; and the unequal-arm polarization control interferometer is configured to convert the optical pulse of the polarization-encoded quantum state into an optical pulse of a time-phase-encoded quantum state. On the basis of a quantum communication encoding control instruction, the first optical coupling unit and the second optical coupling unit are controlled to output the optical pulse of the polarization-encoded quantum state or output the optical pulse of the time-phase-encoded quantum state. In the present application, the same quantum state encoding apparatus can satisfy different encoding requirements of a quantum communication system.

Description

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

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

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

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

[0004] How to implement universal quantum state encoding in an optical quantum encoding apparatus that is compatible with multiple quantum communication system encoding methods is an important problem in quantum communication applications.

[0005] SUMMARY

[0006] The purpose of the present application is to provide a quantum state encoding apparatus, method and software-defined quantum communication system to solve the technical problems mentioned in the prior art.

[0007] In order to achieve the above-mentioned purpose, in a first aspect, the application provides a quantum state encoding device, comprising: a polarization encoding unit, a first optical coupling unit, an unequal arm polarization control interferometer, a first transmission optical path, and a second optical coupling unit. The polarization encoding unit comprises at least one input port and one output port. The polarization encoding unit is configured to input an optical pulse through one of the input ports, generate a polarization encoded quantum state optical pulse based on the input optical pulse, and output the polarization encoded quantum state optical pulse through the output port. The first optical coupling unit comprises one input port and two output ports, i.e., a first port, a second port, and a third port. The first port is connected to the output port of the polarization encoding unit. The second optical coupling unit comprises two input ports and one output port, i.e., a fourth port, a fifth port, and a sixth port. The unequal arm polarization control interferometer comprises one input port and one output port. The unequal arm polarization control interferometer is configured to perform time-phase encoding conversion on the input polarization encoded quantum state optical pulse, and output a time-phase encoded quantum state optical pulse. The third port of the first optical coupling unit is connected to the input port of the unequal arm polarization control interferometer. The output port of the unequal arm polarization control interferometer is connected to the fifth port of the second optical coupling unit, forming a first optical output branch. The second port of the first optical coupling unit is connected to the fourth port of the second optical coupling unit through the first transmission optical path, forming a second optical output branch. The first optical coupling unit is configured to input the polarization encoded quantum state optical pulse output by the polarization encoding unit into the first optical output branch and / or the second optical output branch according to a quantum communication encoding control instruction. The quantum communication encoding control instruction is determined according to the encoding requirements of a quantum communication system. The sixth port of the second optical coupling unit is an output port of the quantum state encoding device. The quantum state encoding device is configured to output the polarization encoded quantum state optical pulse transmitted by the second optical output branch or the time-phase encoded quantum state optical pulse transmitted by the first optical output branch according to the quantum communication encoding control instruction.

[0008] In a second aspect, the application provides a quantum state encoding method, which is implemented by using the quantum state encoding device described above.

[0009] In a third aspect, the application provides a software-defined quantum communication system, which comprises the quantum state encoding device described above.

[0010] In summary, the quantum state encoding device, method, and software-defined quantum communication system provided by the application have at least the following beneficial effects:

[0011] The application adopts a polarization encoding unit, a first optical coupling unit, an unequal arm polarization control interferometer, a first transmission light path and a second optical coupling unit to form a quantum state encoding device, wherein the polarization encoding unit is used to generate a polarization encoded quantum state light pulse, and the unequal arm polarization control interferometer is used to convert the polarization encoded quantum state light pulse into a time phase encoded quantum state light pulse. According to a quantum communication encoding control instruction, the first optical coupling unit and the second optical coupling unit output the polarization encoded quantum state light pulse or output the time phase encoded quantum state light pulse, so that the same quantum state encoding device can meet different encoding requirements of a quantum communication system. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and serve to explain the principles of the application, and do not limit the application. In the drawings:

[0013] Fig. 1 is a structural block diagram of a quantum state encoding device provided by an embodiment of the application;

[0014] Fig. 2 is a structural block diagram of a polarization encoding unit provided by an embodiment of the application;

[0015] Fig. 3 is a structural block diagram of a first polarization operation module provided by an embodiment of the application;

[0016] Fig. 4 is a structural block diagram of a second polarization operation module provided by an embodiment of the application;

[0017] Fig. 5 is a structural block diagram of a third polarization operation module provided by an embodiment of the application;

[0018] Fig. 6 is a structural block diagram of a fourth polarization operation module provided by an embodiment of the application;

[0019] Fig. 7 is a structural block diagram of a fifth polarization operation module provided by an embodiment of the application;

[0020] Fig. 8 is a structural block diagram of a sixth polarization operation module provided by an embodiment of the application;

[0021] Fig. 9 is a structural block diagram of a seventh polarization operation module provided by an embodiment of the application;

[0022] Fig. 10 is a structural block diagram of an eighth polarization operation module provided by an embodiment of the application;

[0023] Fig. 11 is a structural block diagram of a ninth polarization operation module provided by an embodiment of the application;

[0024] Fig. 12 is a structural block diagram of a tenth polarization operation module provided by an embodiment of the application;

[0025] FIG. 13 is a structural block diagram of a 11th polarization operation module according to an embodiment of the present application;

[0026] FIG. 14 is a structural block diagram of a 12th polarization operation module according to an embodiment of the present application;

[0027] FIG. 15 is a structural block diagram of a 13th polarization operation module according to an embodiment of the present application;

[0028] FIG. 16 is a structural block diagram of a 14th polarization operation module according to an embodiment of the present application;

[0029] FIG. 17 is a structural block diagram of a 15th polarization operation module according to an embodiment of the present application;

[0030] FIG. 18 is a structural block diagram of a 16th polarization operation module according to an embodiment of the present application;

[0031] FIG. 19 is a structural diagram of a first embodiment of an unequal arm polarization control interferometer according to an embodiment of the present application;

[0032] FIG. 20 is a structural diagram of a second embodiment of an unequal arm polarization control interferometer according to an embodiment of the present application;

[0033] FIG. 21 is a structural diagram of a third embodiment of an unequal arm polarization control interferometer according to an embodiment of the present application;

[0034] FIG. 22 is a structural diagram of a fourth embodiment of an unequal arm polarization control interferometer according to an embodiment of the present application;

[0035] FIG. 23 is a structural diagram of a fifth embodiment of an unequal arm polarization control interferometer according to an embodiment of the present application;

[0036] FIG. 24 is a structural diagram of a sixth embodiment of an unequal arm polarization control interferometer according to an embodiment of the present application;

[0037] FIG. 25 is a structural diagram of another quantum state encoding device according to an embodiment of the present application;

[0038] FIG. 26 is a structural diagram of a software defined quantum communication system according to an embodiment of the present application. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. It should be understood, however, that the description is merely exemplary of the present application, but is not intended to limit the present application. Further, in the following description, the description of well-known structures and techniques is omitted to avoid obscuring the concept of the present application.

[0040] Various structural diagrams according to embodiments of the present application are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for clarity and others are omitted. The shapes and relative sizes of the various regions, layers, and the relative positions of the regions / layers shown in the drawings are merely exemplary and may deviate in actuality due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, and relative positions can be additionally designed according to actual needs by those skilled in the art.

[0041] In the context of the present application, when a layer / element is referred to as being located "on" another layer / element, the layer / element can be directly on the other layer / element, or there can be an intervening layer / element therebetween. In addition, if a layer / element is located "on" another layer / element in one orientation, it can be located "under" the other layer / element when the orientation is reversed. In order to make the technical problems, technical solutions, and beneficial effects of the present application more clear, the present application is further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present application and not to limit the present application.

[0042] Furthermore, the terms "first", "second", etc. are used only for descriptive purposes and should not be construed as indicating or implying relative importance or an indicated number of the technical features. Thus, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited. The meaning of "several" is one or more, unless otherwise explicitly specified and limited.

[0043] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", and "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] The quantum state encoding device in the existing quantum communication system has the following problems:

[0045] 1. The commonly used quantum communication encoding methods include polarization encoding and time phase encoding. A set of quantum communication system generally selects one of the encoding methods, so that the system does not have universality and cannot be flexibly networked, and cannot meet the encoding needs of different quantum communication systems for quantum states.

[0046] 2, The preparation of polarization encoding or time phase encoding quantum states is usually implemented using a phase modulator, however, the phase modulator is susceptible to environmental influences leading to phase drift, which requires real-time feedback compensation or temperature control measures, making it difficult for quantum communication systems to work stably and efficiently.

[0047] 3, Currently, the encoding rate of quantum communication systems in practical applications is mainly 100MHz and 1GHz, however, in order to increase the safe transmission distance of quantum communication and improve the quantum key generation rate or information transmission rate, quantum states at a speed of 10GHz or higher need to be encoded.

[0048] 4, Currently, quantum communication systems generally support the encoding of two groups of four quantum states, and it is difficult to support multiple quantum communication protocols such as BB84 and reference frame independent in a set of quantum communication systems, and quantum communication systems need to support three groups of four quantum state encoding or three groups of six quantum state encoding.

[0049] In order to solve the above problems, the present application provides a quantum state encoding device, as shown in Figure 1, which is a structural block diagram of a quantum state encoding device provided by an embodiment of the present application, the device comprises: a polarization encoding unit 100, a first optical coupling unit 200, an unequal arm polarization control interferometer 300, a first transmission light path 400 and a second optical coupling unit 500.

[0050] In some embodiments, the polarization encoding unit 100 comprises at least one input port and one output port. The polarization encoding unit 100 is used to input an optical pulse through one of the input ports, generate a polarization encoded quantum state optical pulse based on the input optical pulse, and output through the output port.

[0051] The first optical coupling unit 200 comprises an input port and two output ports, namely a first port G, a second port H and a third port I. Among them, the first port G is connected with the output port of the polarization encoding unit 100.

[0052] The second optical coupling unit 500 comprises two input ports and one output port, namely a fourth port H', a fifth port I' and a sixth port G'.

[0053] The unequal arm polarization control interferometer 300 comprises an input port and an output port, which is used for time phase encoding conversion of the input polarization encoded quantum state optical pulse, and outputs the time phase encoded quantum state optical pulse. Among them, the input port of the unequal arm polarization control interferometer 300 is used for receiving the polarization encoded quantum state optical pulse input by the first optical coupling unit, and the output port of the unequal arm polarization control interferometer 300 is used for outputting the time phase encoded quantum state optical pulse after the time phase encoding conversion by the unequal arm polarization control interferometer 300.

[0054] 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 X phase base, Y phase base and Z time base quantum states.

[0055] The third port I of the first optical coupling unit 200 is connected with the input port of the unequal arm polarization control interferometer 300. The output port of the unequal arm polarization control interferometer 300 is connected with the fifth port I' of the second optical coupling unit 500, forming a first optical output branch.

[0056] The second port H of the first optical coupling unit 200 is connected with the fourth port H' of the second optical coupling unit 500 through the first transmission optical path 400, forming a second optical output branch.

[0057] The sixth port G' of the second optical coupling unit 500 is an output port of the quantum state encoding device. In the embodiment of the present application, the second optical coupling unit 500 can be used to output the polarization encoded quantum state light pulse output by the second optical output branch or output the time-phase encoded quantum state light pulse output by the first optical output branch according to the quantum communication encoding control instruction.

[0058] It should be noted that the quantum communication encoding control instruction can be issued by programmable control software. For example, when the first optical coupling unit and the second optical coupling unit are both optical switches, according to the encoding needs of the quantum communication system, the quantum communication encoding control instruction is issued by running the control software in the upper computer (control circuit unit or processor unit) in the quantum communication system to configure the gating state of the optical switch, so as to realize the selective output of the polarization encoded quantum state light pulse or the time-phase encoded quantum state light pulse.

[0059] In the above embodiment, the polarization encoding unit 100, the first optical coupling unit 200, the unequal arm polarization control interferometer 300, the first transmission optical path 400 and the second optical coupling unit 500 are used to form the quantum state encoding device. The polarization encoding unit 100 can generate a polarization encoded quantum state light pulse, and the unequal arm polarization control interferometer 300 can convert the polarization encoded quantum state light pulse into a time-phase encoded quantum state light pulse. The first optical coupling unit 200 and the second optical coupling unit 500 can control the output of the polarization encoded quantum state light pulse or the output of the time-phase encoded quantum state light pulse according to the quantum communication encoding control instruction. Therefore, the quantum state encoding device described in the embodiment of the present application flexibly realizes various quantum communication encoding modes of polarization encoded quantum states and time-phase encoded quantum states, and realizes that the same quantum state encoding device can meet different encoding needs of the quantum communication system.

[0060] In some embodiments, the first optical coupling unit 200 is an optical coupler, and the second optical coupling unit 500 is an optical switch. The optical coupler can be a free-space crystal coupler or a fiber coupler, which is used to split the optical pulses. The optical switch can be used to select the encoded quantum state transmitted through one of the optical output branches by connecting or disconnecting.

[0061] Since the first port G of the first optical coupling unit 200 is connected to the output port of the polarization encoding unit 100, the second port H is connected to one end of the first transmission optical path 400, and the third port I is connected to the input port of the unequal-arm polarization control interferometer 300. Therefore, when the first optical coupling unit 200 is an optical coupler, it can be used to input the polarization-encoded quantum state optical pulses output by the polarization encoding unit 100 through the first port, and split the polarization-encoded quantum state optical pulses into two sub-pulses, which are respectively input into the first optical output branch and the second optical output branch through the third port I and the second port H.

[0062] In this embodiment, the second optical coupling unit 500 is used to select the polarization-encoded quantum state optical pulses output by the second optical output branch or the time-phase encoded quantum state optical pulses output by the first optical output branch according to the quantum communication encoding control instruction. In an embodiment, the second optical coupling unit 500, i.e., the optical switch, can flexibly switch the connection between the second optical output branch and the first optical output branch according to the quantum communication encoding control instruction, so as to select the polarization-encoded quantum state optical pulses output by the second optical output branch or the time-phase encoded quantum state optical pulses output by the first optical output branch.

[0063] In the above embodiment, the polarization-encoded quantum state optical pulses are split into two paths by the first optical coupling unit 200, and are respectively input into the first optical output branch and the second optical output branch. The selection function of the second optical coupling unit 500 can switch the connected optical output branch according to the encoding requirement of the quantum communication system. In this way, the quantum states with different encoding modes can be selectively output, which improves the flexibility and adaptability of the quantum communication system. The advantages of the two encoding modes can be fully utilized to ensure the adaptability of the quantum state to the communication channel in the quantum communication process, and to improve the security and reliability of the quantum communication system. In addition, it is convenient to integrate new encoding modes, thereby supporting new communication protocols and higher-performance quantum state transmission.

[0064] In some other embodiments, the first optical coupling unit 200 is an optical switch, and the second optical coupling unit 500 is an optical switch.

[0065] The first port G of the first optical coupling unit 200 is connected with the output port of the polarization encoding unit 100, the second port H is connected with the input port of the first transmission optical path 400, and the third port I is connected with the input port of the unequal-arm polarization control interferometer 300. Therefore, when the first optical coupling unit 200 is an optical switch, the light pulse of the polarization encoded quantum state can be selectively input to the first optical output branch or the second optical output branch based on the quantum communication encoding control instruction.

[0066] In an embodiment of the present application, the first optical coupling unit 200 can select the corresponding optical output branch to be connected according to the quantum communication encoding control instruction, and input the light pulse of the polarization encoded quantum state output by the polarization encoding unit 100 to the corresponding optical output branch. That is, when the quantum communication encoding control instruction is an instruction for outputting the polarization encoded quantum state, the first optical coupling unit 200 selects the second optical output branch to be connected, and inputs the light pulse of the polarization encoded quantum state to the second optical output branch. When the quantum communication encoding control instruction is an instruction for outputting the time-phase encoded quantum state, the first optical coupling unit 200 selects the first optical output branch to be connected, and inputs the light pulse of the polarization encoded quantum state to the first optical output branch.

[0067] In the embodiment, the second optical coupling unit 500 is an optical switch, which can connect the first optical output branch or the second optical output branch according to the quantum communication encoding control instruction, that is, connect the first optical output branch outputting the light pulse of the time-phase encoded quantum state, or connect the second optical output branch outputting the light pulse of the polarization encoded quantum state.

[0068] It should be noted that, generally, the optical output branch selected to be connected by the second optical coupling unit 500 is consistent with the optical output branch selected to be connected by the first optical coupling unit 200. Specifically, the first optical coupling unit 200 and the second optical coupling unit 500 select the same optical output branch to be connected based on the quantum communication encoding control instruction, that is, the first optical coupling unit 200 selects the first optical output branch to be connected based on the quantum communication encoding control instruction, and the second optical coupling unit 500 also selects the first optical output branch to be connected based on the quantum communication encoding control instruction. When the first optical coupling unit 200 and the second optical coupling unit 500 are both connected with the first transmission optical path, the second optical coupling unit 500 outputs the light pulse of the time-phase encoded quantum state transmitted by the first optical output branch.

[0069] Alternatively, the first optical coupling unit 200 selects the second optical output branch to be connected based on the quantum communication encoding control instruction, and the second optical coupling unit 500 also selects the second optical output branch to be connected based on the quantum communication encoding control instruction. When the first optical coupling unit 200 and the second optical coupling unit 500 are both connected with the second optical output branch, the second optical coupling unit 500 outputs the light pulse of the polarization encoded quantum state transmitted by the second optical output branch.

[0070] In the above embodiment, the first optical coupling unit 200 and the second optical coupling unit 500 can be connected to the same optical output branch according to the quantum communication encoding control instruction, so that the encoded quantum state matching the quantum communication protocol can be output, and the flexibility and adaptability of the quantum communication system are improved. The advantages of the two encoding methods can be fully utilized to ensure the adaptability of the quantum state to the communication channel in the quantum communication process, and the security and reliability of the quantum communication system are improved. In addition, new encoding methods can be integrated to support new communication protocols and higher performance quantum state transmission.

[0071] In some embodiments, the first optical coupling unit 200 is an optical switch, and the second optical coupling unit 500 is an optical coupler.

[0072] In the embodiment of the present application, the first optical coupling unit 200 includes one input port and two output ports. The first optical coupling unit 200 can freely switch the connected port based on the quantum communication encoding control instruction, so as to be connected to the first optical output branch or the second optical output branch.

[0073] The optical coupler corresponding to the second optical coupling unit 500 can include two input ports and one output port, and each input port can correspond to one optical output branch. The optical coupler is used to output the time-phase encoded quantum state light pulse transmitted by the first optical output branch or the polarization encoded quantum state light pulse transmitted by the second optical output branch.

[0074] Specifically, when the first optical coupling unit 200 is connected to the first optical output branch through the output port I based on the quantum communication encoding control instruction, the first optical coupling unit 200 inputs the polarization encoded quantum state light pulse output by the polarization encoding unit 100 to the first optical output branch through the output port I. At this time, the first optical output branch inputs the polarization encoded quantum state light pulse output by the first optical coupling unit 200, and outputs the time-phase encoded quantum state light pulse converted by the unequal arm polarization control interferometer 300. The input and output of the second optical output branch are both empty. The second optical coupling unit 500 couples the outputs of the two optical output branches, and the coupling output is the time-phase encoded quantum state light pulse of the first optical output branch.

[0075] When the first optical coupling unit 200 communicates with the second optical output branch through the output port H based on the quantum communication encoding control instruction, the first optical coupling unit 200 inputs the polarized encoded quantum state light pulse output by the polarization encoding unit 100 to the second optical output branch through the output port H. At this time, the second optical output branch receives the polarized encoded quantum state light pulse input by the first optical coupling unit 200 and outputs it, and the input and output of the first optical output branch are both empty. The second optical coupling unit 500 couples the outputs of the two optical output branches, and the coupling amount of the output is the polarized encoded quantum state light pulse of the second optical output branch.

[0076] In the above embodiment, the first optical coupling unit 200 can output the polarized encoded quantum state to the optical output branch matched with the quantum communication system encoding requirement, and then the second optical coupling unit 500 can output the quantum state required by the quantum communication system encoding. In this way, the flexibility and adaptability of the quantum communication system are improved. And the advantages of the two encoding methods can be fully utilized to ensure the adaptability of the quantum state to the communication channel in the communication process and improve the security and reliability of the quantum communication system. In addition, it is convenient to integrate new encoding methods, thereby supporting new communication protocols and higher performance quantum state transmission.

[0077] FIG. 2 shows a structure block diagram of a polarization encoding unit provided by an embodiment of the present application. The polarization encoding unit 100 comprises at least one polarization operation module 110. The polarization operation module 110 comprises a polarization control optical path 111 and at least one phase modulator 112 arranged in the transmission optical path of the polarization control optical path. That is, one polarization operation module 110 comprises one polarization control optical path 111 and one or more phase modulators 112.

[0078] The polarization control optical path 111 comprises at least one input port and one output port. Among them, the input port of the polarization control optical path 111 serves as the input port of the polarization operation module 110, and the output port of the polarization control optical path 111 serves as the output port of the polarization operation module 110.

[0079] The polarization control optical path 111 is used to split one light pulse input by itself into two sub light pulses. The phase modulator 112 is used to phase modulate at least one sub light pulse based on a modulation signal, so that a specific phase difference is generated between the two sub light pulses. The polarization control optical path 111 is also used to combine the two sub light pulses with the phase difference and output the generated polarized encoded quantum state light pulse.

[0080] In the embodiment of the present application, the two sub light pulses split by the polarization control optical path 111 can be a first sub light pulse and a second sub light pulse. One or more phase modulators 112 in the polarization operation module 110 can modulate the phase of the first sub light pulse and / or the second sub light pulse, so that a specific phase difference between the two sub light pulses is generated to meet the requirements of the quantum communication system. The first sub light pulse and the second sub light pulse after the one or more phase modulators 112 are combined in the polarization control optical path 111, and an output combined light pulse is output.

[0081] wherein the two eigenpolarizations of the polarization control optical path 111 are and respectively represent the horizontal direction and the vertical direction. The eigenpolarizations of the polarization control optical path 111 are the eigenpolarizations of the polarization operation module 110.

[0082] FIG. 3 shows a structural block diagram of a polarization operation module according to an embodiment of the present application. As shown in FIG. 3, the polarization control optical path 111 in the polarization operation module 110 can include a third optical coupling unit 31, a fourth optical coupling unit 32, a second transmission optical path 33, and a third transmission optical path 34. The third optical coupling unit 31 and the fourth optical coupling unit 32 are connected through the second transmission optical path 33 and the third transmission optical path 34.

[0083] In an embodiment of the present application, the third optical coupling unit 31 can include at least three ports, of which at least one is an input port and the other two are output ports. The fourth optical coupling unit 32 can include at least three ports, of which two are input ports and at least one is an output port. One output port of the third optical coupling unit 31 is connected to one input port of the fourth optical coupling unit 32 through the second transmission optical path 33, and the other output port of the third optical coupling unit 31 is connected to the other input port of the fourth optical coupling unit 32 through the third transmission optical path 34.

[0084] In the embodiment, the one or more phase modulators 112 can be arranged in the second transmission optical path 33 or the third transmission optical path 34, or arranged in the second transmission optical path 33 and the third transmission optical path 34, respectively.

[0085] The third optical coupling unit 31 is configured to split an input light pulse into two sub light pulses, i.e., a first sub light pulse and a second sub light pulse, which are transmitted along the second transmission optical path 33 and the third transmission optical path 34, respectively, and then combined by the fourth optical coupling unit 34 after passing through at least one phase modulator 112.

[0086] In some embodiments, the phase modulator 112 comprises a forward input optical port E and a backward input optical port F. The transmission optical path (the second transmission optical path 33 or the third transmission optical path 34) connected to the phase modulator 112 is coupled to the slow axis of the forward input optical port and the slow axis of the backward input optical port of the phase modulator 112, or is coupled to the fast axis of the forward input optical port and the fast axis of the backward input optical port of the phase modulator 112; the phase modulator 112 is configured to perform phase modulation on the input sub-light pulses based on a modulation signal, so as to generate a phase difference between the two sub-light pulses.

[0087] In addition, it can be understood that the phase modulator 112 further comprises an electrical port for receiving a modulation signal.

[0088] In some embodiments, the phase modulator 112 performs effective phase modulation on the sub-light pulses input from the forward input optical port and the backward input optical port after applying a low-frequency modulation signal (for example, a modulation signal with a frequency less than 1 GHz). When the phase modulator 112 works in a non-reciprocal state after applying a high-frequency modulation signal (for example, a modulation signal with a frequency not less than 10 GHz) with a frequency higher than a specified threshold, the ratio of the modulation efficiency of the sub-light pulses input from the forward input optical port to the modulation efficiency of the sub-light pulses input from the backward input optical port is greater than a preset threshold, that is, only the sub-light pulses input from the forward input optical port are effectively phase-modulated, and the sub-light pulses input from the backward input optical port are not effectively phase-modulated, which can also be considered as not modulated; when the phase modulator 112 applies a high-frequency modulation signal with a frequency higher than the specified threshold, there can be multiple sub-light pulses input from the forward input optical port and multiple sub-light pulses input from the backward input optical port at the same time.

[0089] In some embodiments, the third light coupling unit 31 and the fourth light coupling unit 32 are the same light coupler. The second transmission light path 33 and the third transmission light path 34 are two different transmission light paths. FIG. 4 shows a specific structural schematic diagram of a polarization operation module according to an embodiment of the present application. As shown in FIG. 4, the polarization control light path 111 in the polarization operation module 110 can include a light coupler 41 (i.e., the third light coupling unit 31 and the fourth light coupling unit 32), a second transmission light path 42 and a third transmission light path 43, a mirror 44 and a mirror 45. The mirror 44 and the mirror 45 are used to reflect the input sub-light pulses back to the light coupler 41. The mirror 44 or the mirror 45 is a quarter-wave plate mirror or a 90° Faraday rotating mirror, so that the polarization state of the reflected sub-light pulses is rotated by 90° relative to the polarization state of the sub-light pulses input to the corresponding mirror, so that the polarization states of the two sub-light pulses reflected back to the light coupler 41 are orthogonal to each other. In this embodiment, the polarization states of the two sub-light pulses reflected back to the light coupler 41 are the eigenpolarizations of the polarization control light path 111. That is, the polarization states of the two sub-light pulses reflected back to the light coupler 41 are the eigenpolarizations of the polarization operation module 110.

[0090] The light coupler 41 can include at least three ports, at least one input port and two output ports, namely port A, port B and port C, wherein the port B and the port C are output ports and are connected to the two mirrors 44 and 45 through the second transmission light path 42 and the third transmission light path 43, respectively, and the port A is an input port for receiving the light pulses output by the polarization control light path 111. Specifically, as shown in FIG. 4, the port B is connected to the mirror 44 through the second transmission light path 42, and the port C is connected to the mirror 45 through the third transmission light path 43.

[0091] In an embodiment, when the light coupler 41 includes three ports, the input port can also serve as an output port of the polarization operation module 110 for outputting the light pulses of the polarization-encoded quantum state.

[0092] In another embodiment, when the light coupler 41 includes four ports, as described in FIG. 4, the light coupler 41 can further include an output port, i.e., the port D, which serves as an output port of the polarization operation module 110 for outputting the light pulses of the polarization-encoded quantum state.

[0093] One or more phase modulators 112 in the polarization operation module 110 can be arranged in the second transmission light path 42 or in the third transmission light path 43, or arranged in the second transmission light path 42 and the third transmission light path 43 respectively. The phase modulator 112 is used to phase modulate the passing sub-light pulse based on a modulation signal, so as to generate a phase difference between the two sub-light pulses reflected back to the optical coupler 41. FIG. 4 only shows the case where one phase modulator is arranged in the second transmission light path 42.

[0094] In an embodiment of the present application, the optical coupler 41 is used to split one light pulse received from the input port into two sub-light pulses, and output the two sub-light pulses through the port B and the port C respectively, and transmit the two sub-light pulses along the second transmission light path 42 and the third transmission light path 43 respectively to the two mirrors, and reflect the two sub-light pulses back to the optical coupler 41 by the two mirrors. Wherein, the sub-light pulse transmitted along the transmission light path where the phase modulator 112 is arranged will pass through the phase modulator 112 for phase modulation, so as to generate a phase difference between the two sub-light pulses reflected back to the optical coupler 41.

[0095] In some embodiments, the third optical coupling unit 31 and the fourth optical coupling unit 32 are the same polarization beam splitter. The second transmission light path 33 and the third transmission light path 34 are two different transmission light paths. FIGS. 5 and 6 show the structure of another polarization operation module provided by an embodiment of the present application. The polarization control light path 111 in the polarization operation module 110 can include a polarization beam splitter 51 (i.e. the third optical coupling unit 31 and the fourth optical coupling unit 32), a second transmission light path 52 and a third transmission light path 53, a mirror 54 and a mirror 55. Wherein, the mirror 54 and the mirror 55 are used to reflect the input sub-light pulse back to the polarization beam splitter 51. Optionally, the mirror 54 and the mirror 55 are polarization state rotating mirrors, for example, the mirror 54 and the mirror 55 can be quarter-wave plate mirrors or 90° Faraday rotating mirrors.

[0096] The polarization beam splitter 51 can include at least three ports, at least one input port and two output ports, namely port A, port B and port C, wherein the port B and the port C are connected with the two mirrors through the second transmission light path 52 and the third transmission light path 53 respectively, and the port A is used as an input port for receiving the light pulse input into the polarization control light path 111. Specifically, as shown in FIG. 5, the port B is connected with the mirror 54 through the second transmission light path 52, and the port C is connected with the mirror 55 through the third transmission light path 53.

[0097] In an embodiment, as shown in FIG. 5, when the polarization beam splitter 51 includes three ports, the input port A can also be used as an output port of the polarization operation module 110, for outputting the polarization encoded quantum state light pulse.

[0098] In yet another embodiment, as shown in FIG. 6, the polarization beam splitter 51 can further include an output port D as the output port of the polarization operation module 110, for outputting the polarization-encoded quantum state light pulse.

[0099] It should be noted that, in the case that the mirrors 54 and 55 do not rotate the polarization state of the input sub-light pulse, the polarization beam splitter 51 only outputs the polarization-encoded quantum state light pulse after beam combination from the port A. In the case that the mirrors 54 and 55 rotate the polarization state of the input sub-light pulse by any one of the angles (non-0 and 90°), the polarization beam splitter 51 can output the polarization-encoded quantum state light pulse after beam combination from the port A or the port D, wherein, if the polarization state of the sub-light pulse is rotated by 90°, the polarization-encoded quantum state light pulse after beam combination can only be output from the port D.

[0100] In the embodiment, the eigenpolarization state of the polarization beam splitter 51 is the eigenpolarization state of the polarization control optical path 111.

[0101] One or more phase modulators 112 in the polarization operation module 110 can be arranged in the second transmission optical path 52 or the third transmission optical path 53, or arranged in the second transmission optical path 52 and the third transmission optical path 53 respectively. It should be noted that FIG. 5 and FIG. 6 only show the case that one phase modulator 112 is arranged in the second transmission optical path 52.

[0102] In an embodiment of the present application, the polarization beam splitter 51 is used to split one light pulse received from the input port into two sub-light pulses, and output the two sub-light pulses through the port B and the port C respectively, and transmit the two sub-light pulses along the second transmission optical path 52 and the third transmission optical path 53 respectively to two mirrors, and reflect the two sub-light pulses back to the polarization beam splitter 51 by the two mirrors. Among them, one sub-light pulse transmitted along the transmission optical path where the phase modulator 112 is located will be phase-modulated by the phase modulator 112, so that the two sub-light pulses reflected back to the polarization beam splitter 51 form a phase difference.

[0103] It should be noted that the principle of the phase modulator 112 modulating the sub-light pulse in the embodiment of the present application is similar to the foregoing, and for the sake of brevity, it will not be described here.

[0104] In an embodiment, the third optical coupling unit 31 can be a polarization beam splitter, and the fourth optical coupling unit 32 can be an optical coupler. FIG. 7 shows a specific structure diagram of another polarization operation module provided by an embodiment of the present application. As shown in FIG. 7, the polarization control optical path 111 in the polarization operation module 110 can include a polarization beam splitter 71 (i.e. the third optical coupling unit 31), a second transmission optical path 72, a third transmission optical path 73, and an optical coupler 74 (i.e. the fourth optical coupling unit 32).

[0105] As shown in FIG. 7, the polarization beam splitter 71 is connected with the optical coupler 74 through the second transmission light path 72 and the third transmission light path 73. The polarization beam splitter 71 can include three ports, i.e., a port A, a port B and a port C. The optical coupler 74 can include three ports, i.e., a port A', a port B' and a port C'. The port B of the polarization beam splitter 71 can be connected with the port B' of the optical coupler 74 through the second transmission light path 72, and the port C of the polarization beam splitter 71 can be connected with the port C' of the optical coupler 74 through the third transmission light path 73.

[0106] The one or more phase modulators 112 can be arranged in the second transmission light path 72 or in the third transmission light path 73, or arranged in the second transmission light path 72 and the third transmission light path 73 respectively. FIG. 7 only shows that one phase modulator 112 is arranged in the third transmission light path 73. The principle of the phase modulator 112 modulating the sub-light pulse in the embodiment of the present application is similar to the foregoing, and for the sake of brevity, it will not be described here again.

[0107] The polarization beam splitter 71 is used for splitting one light pulse input from the port A into two sub-light pulses, i.e., a first sub-light pulse and a second sub-light pulse, and outputting the two sub-light pulses from the ports B and C respectively. The first sub-light pulse and the second sub-light pulse are transmitted along the second transmission light path 72 and the third transmission light path 73 respectively, and one sub-light pulse is phase-modulated by at least one phase modulator 112. The two sub-light pulses are input into the optical coupler 74 from the ports B' and C' respectively. The optical coupler 74 is used for combining the two input sub-light pulses, and outputting the light pulse of the polarization encoding quantum state from the port A'.

[0108] It should be noted that the intrinsic polarization state of the polarization beam splitter 71 in the embodiment is the intrinsic polarization state of the polarization control light path 111.

[0109] In yet another embodiment, the third optical coupling unit 31 can be a polarization beam splitter, and the fourth optical coupling unit 32 can also be a polarization beam splitter. FIG. 8 shows a specific structure diagram of another polarization operation module provided by the embodiment of the present application. As shown in FIG. 8, the polarization control light path 111 in the polarization operation module 110 can include a polarization beam splitter 81 (i.e., the third optical coupling unit 31), a second transmission light path 82, a third transmission light path 83 and a polarization beam splitter 84 (i.e., the fourth optical coupling unit 32). The intrinsic polarization state of the polarization beam splitter 84 is the intrinsic polarization state of the polarization control light path 111.

[0110] As shown in FIG. 8, the polarization beam splitter 81 is connected with the polarization beam splitter 84 through the second transmission light path 82 and the third transmission light path 83. The polarization beam splitter 81 can include three ports, i.e., a port A, a port B and a port C. The polarization beam splitter 84 can include three ports, i.e., a port A', a port B' and a port C'. The port B of the polarization beam splitter 81 can be connected with the port B' of the polarization beam splitter 84 through the second transmission light path 82, and the port C of the polarization beam splitter 81 can be connected with the port C' of the polarization beam splitter 84 through the third transmission light path 83. The port A of the polarization beam splitter 81 serves as an input port of the polarization control light path 111, and the port A' of the polarization beam splitter 84 serves as an output port of the polarization control light path 111.

[0111] The one or more phase modulators 112 can be arranged in the second transmission light path 82 or in the third transmission light path 83, or arranged in the second transmission light path 82 and the third transmission light path 83 respectively. FIG. 8 only shows that one phase modulator 112 is arranged in the third transmission light path 83. The principle of modulating the sub light pulses by the phase modulator 112 in the embodiment of the present application is similar to the foregoing, and for the sake of brevity, it will not be described here again.

[0112] The polarization beam splitter 81 is used to split one light pulse input from the port A into two sub light pulses, i.e., a first sub light pulse and a second sub light pulse, and output from the ports B and C respectively. The first sub light pulse and the second sub light pulse are transmitted along the second transmission light path 82 and the third transmission light path 83 respectively, wherein one sub light pulse is phase-modulated by at least one phase modulator 112. The two sub light pulses are input into the optical coupler 84 from the ports B' and C' respectively. The optical coupler 84 is used to combine the two input sub light pulses, and output the light pulse of the polarization encoded quantum state from the port A'.

[0113] In yet another embodiment, the third optical coupling unit 31 can be an optical coupler, and the fourth optical coupling unit 32 can be an optical coupler. FIG. 9 shows a specific structure diagram of another polarization operation module provided by the embodiment of the present application. As shown in FIG. 9, the polarization control light path 111 in the polarization operation module 110 can include an optical coupler 91 (i.e., the third optical coupling unit 31), a second transmission light path 92, a third transmission light path 93, and an optical coupler 94 (i.e., the fourth optical coupling unit 32). In the embodiment, the polarization states of the two sub light pulses input into the optical coupler 94 are the eigenpolarization states of the polarization control light path 111.

[0114] In one embodiment, the polarization manipulation module further comprises a 90° polarization state rotator 95, which can be disposed in the second transmission optical path 92 or the third transmission optical path 93, for rotating the polarization state of the passing sub-light pulses by 90°. In some embodiments, the 90° polarization state rotator 95 can be a half-wave plate or a 90° Faraday rotator.

[0115] In another embodiment, the second transmission optical path 92 or the third transmission optical path 93 is a 90° twisted polarization maintaining optical fiber.

[0116] As shown in FIG. 9, the optical coupler 91 and the optical coupler 94 are connected by the second transmission optical path 92 and the third transmission optical path 93. The optical coupler 91 can include three ports, namely port A, port B and port C. The optical coupler 95 can include three ports, namely port A', port B' and port C'. The port B of the optical coupler 91 can be connected to the port B' of the optical coupler 94 through the second transmission optical path 92, and the port C of the optical coupler 91 can be connected to the port C' of the optical coupler 94 through the third transmission optical path 93.

[0117] The one or more phase modulators 112 can be disposed in the second transmission optical path 92 or in the third transmission optical path 93, or in the second transmission optical path 92 and the third transmission optical path 93, respectively. The principle of the phase modulator 112 for modulating the sub-light pulses in the present embodiment is similar to the foregoing, and for the sake of brevity, it will not be repeated here. The 90° polarization state rotator 95 is also disposed in the second transmission optical path 92 or the third transmission optical path 93, for rotating the polarization state of the passing sub-light pulses by 90°. The phase modulator 112 and the 90° polarization state rotator 95 can be disposed in different transmission optical paths, or in the same transmission optical path. FIG. 9 only shows that one phase modulator 112 is disposed in the third transmission optical path 93, and the 90° polarization state rotator 95 is disposed in the second transmission optical path 92.

[0118] The optical coupler 91 is used to split one light pulse input from the port A into two sub-light pulses, namely a first sub-light pulse and a second sub-light pulse, and output from the port B and the port C, respectively. The first sub-light pulse and the second sub-light pulse are transmitted along the second transmission optical path 92 and the third transmission optical path 93, respectively. One of the two sub-light pulses passes through at least one phase modulator 112, and the other sub-light pulse passes through a 90° polarization state rotator 95, or one of the two sub-light pulses passes through at least one phase modulator 112 and a 90° polarization state rotator 95. The two sub-light pulses are input into the optical coupler 94 from the port B' and the port C', respectively. The optical coupler 94 is used to combine the two input sub-light pulses and output a light pulse of a polarization encoded quantum state from the port A'.

[0119] In yet another embodiment, the third optical coupling unit 31 can be an optical coupler, and the fourth optical coupling unit 32 can be a polarization beam splitter. FIG. 10 shows a specific structural schematic diagram of another polarization operation module according to an embodiment of the present application. As shown in FIG. 10, the polarization control light path 111 in the polarization operation module 110 can include an optical coupler 1001, a second transmission light path 1002, a third transmission light path 1003, and a polarization beam splitter 1004. In this embodiment, the eigenpolarization state of the polarization beam splitter 1004 is the eigenpolarization state of the polarization control light path 111.

[0120] In one embodiment, the polarization operation module further includes a 90° polarization state rotator 1005, which can be arranged in the second transmission light path 1002 or the third transmission light path 1003, and is configured to rotate the polarization state of the passing sub-light pulse by 90°. In some embodiments, the 90° polarization state rotator 1005 can be a half-wave plate or a 90° Faraday rotator.

[0121] In another embodiment, the second transmission light path 1002 or the third transmission light path 1003 is a 90° twisted polarization maintaining optical fiber.

[0122] As shown in FIG. 10, the optical coupler 1001 and the polarization beam splitter 1004 are connected through the second transmission light path 1002 and the third transmission light path 1003. The optical coupler 1001 can include three ports, namely port A, port B, and port C. The polarization beam splitter 1004 can include three ports, namely port A', port B', and port C'. The port B of the optical coupler 1001 can be connected to the port B' of the polarization beam splitter 1004 through the second transmission light path 1002, and the port C of the optical coupler 1001 can be connected to the port C' of the polarization beam splitter 1004 through the third transmission light path 1003.

[0123] The one or more phase modulators 112 can be arranged in the second transmission light path 1002 or in the third transmission light path 1003, or arranged in the second transmission light path 1002 and the third transmission light path 1003 respectively. The principle of the phase modulator 112 modulating the sub-light pulse is similar to the foregoing, and thus will not be described here again for brevity. The 90° polarization state rotator 1005 can also be arranged in the second transmission light path 1002 or the third transmission light path 1003, and is configured to rotate the polarization state of the passing sub-light pulse by 90°. The phase modulator 112 and the 90° polarization state rotator 1005 can be arranged in different transmission light paths or in the same transmission light path. FIG. 10 only shows that one phase modulator 112 is arranged in the third transmission light path 1003, and the 90° polarization state rotator 1005 is arranged in the second transmission light path 1002.

[0124] The optical coupler 1001 is configured to split one optical pulse input from the port A into two sub optical pulses, i.e., a first sub optical pulse and a second sub optical pulse, and output the first sub optical pulse from the port B and the second sub optical pulse from the port C. The first sub optical pulse and the second sub optical pulse are transmitted along the second transmission optical path 92 and the third transmission optical path 93, respectively. One of the first sub optical pulse and the second sub optical pulse passes through the at least one phase modulator 112, and the other one passes through the 90° polarization state rotator 1005, or one of the first sub optical pulse and the second sub optical pulse passes through the at least one phase modulator 112 and the 90° polarization state rotator 1005. The two sub optical pulses are input into the polarization beam splitter 1004 from the port B' and the port C', respectively. The polarization beam splitter 1004 is configured to combine the two input sub optical pulses and output the optical pulse of the polarization encoded quantum state from the port A'.

[0125] In some embodiments, in order to adjust the intensity of the input optical pulse, a pre-interferometer can be arranged in the polarization control optical path, which is configured to adjust the intensity of the two sub optical pulses input into the second transmission optical path and the third transmission optical path. The pre-interferometer can have various structures, such as a Mach-Zehnder interferometer and a Sagnac interferometer.

[0126] In an embodiment of the present application, the third optical coupling unit 31 and the fourth optical coupling unit 32 are optical couplers. The pre-interferometer can be a first pre-interferometer, i.e., a Sagnac interferometer. The first pre-interferometer includes the fourth transmission optical path, the third optical coupling unit 31, and a pre-phase modulator arranged on the fourth transmission optical path.

[0127] FIG. 11 shows a specific structure of another polarization operation module according to an embodiment of the present application. As shown in FIG. 11, the polarization control optical path 111 in the polarization operation module 110 can include an optical coupler 1101 (i.e., the third optical coupling unit 31), a second transmission optical path 1102, a third transmission optical path 1103, a 90° polarization state rotator 1104 arranged on the second transmission optical path 1102 or the third transmission optical path 1103, an optical coupler 1105 (i.e., the fourth optical coupling unit 32), a fourth transmission optical path 1106, a pre-phase modulator 1107, and an intermediate optical coupling unit 1108. The intermediate optical coupling unit 1108 is arranged in the second transmission optical path 1102 or the third transmission optical path 1103. The polarization states of the two sub optical pulses input into the optical coupler 1105 are the eigenpolarization states of the polarization control optical path 111.

[0128] Compared with FIG. 9, the polarization operation module shown in FIG. 11 adds the first pre-interferometer and the intermediate optical coupling unit 1108, and the optical coupler 1101 includes four ports.

[0129] The first pre-light interferometer is configured to split the input light pulse into two pre-sub light pulses, and cause a phase difference between the two pre-sub light pulses by a pre-phase modulator.

[0130] The pre-phase modulator 1107 is configured to perform phase modulation on one of the two pre-sub light pulses transmitted by the fourth transmission light path 1106 based on a modulation signal, or perform different phase modulation on the two pre-sub light pulses, so that the two pre-sub light pulses have a phase difference.

[0131] As shown in FIG. 11, the optical coupler 1101 can include four ports, namely port A, port B, port C and port D. The optical coupler 1105 can include three ports, namely port A', port B' and port C'. Among them, the port A' of the optical coupler 1105 can be used as an output port of the polarization operation module, and is configured to output the generated polarization encoded quantum state light pulse.

[0132] The intermediate optical coupling unit 1108 can include three ports, namely port X, port Y and port Z.

[0133] The two ports of the intermediate optical coupling unit 1108 are connected with the optical coupler 1101 and the optical coupler 1105 respectively. Specifically, when the intermediate optical coupling unit 1108 is arranged in the third transmission light path 1103, as shown in FIG. 11, the port Y of the intermediate optical coupling unit 1108 is connected with the port B of the optical coupler 1101, and the port Z of the intermediate optical coupling unit 1108 is connected with the port B' of the optical coupler 1105. When the intermediate optical coupling unit 1108 is arranged in the second transmission light path 1102, the port Y of the intermediate optical coupling unit 1108 is connected with the port C of the optical coupler 1101, and the port Z of the intermediate optical coupling unit 1108 is connected with the port C' of the optical coupler 1105.

[0134] The port X of the intermediate optical coupling unit 1108 is an input port of the polarization operation module 110. The intermediate optical coupling unit 1108 is configured to receive one light pulse of the input polarization control light path 111 from the port X, and input it into the first pre-light interferometer through the port Y.

[0135] The port A and the port D of the optical coupler 1101 are connected through the fourth transmission light path 1106, and are configured to split the one light pulse input by the intermediate optical coupling unit 1108 into two pre-sub light pulses and input them into the fourth transmission light path 1106 from different ports.

[0136] One or more phase modulators 112 in the polarization operation module 110 can be arranged in the second transmission light path 1102 or in the third transmission light path 1103, or arranged in the second transmission light path 1102 and the third transmission light path 1103 respectively. The principle of the phase modulator 112 modulating the sub-light pulse is similar to the foregoing, and for the sake of brevity, it is not repeated here. The 90° polarization state rotator 1104 can also be arranged in the second transmission light path 1102 or the third transmission light path 1103, for rotating the polarization state of the passing sub-light pulse by 90°. The phase modulator 112 and the 90° polarization state rotator 1104 can be arranged in different transmission light paths respectively, or arranged in the same transmission light path. FIG. 11 only shows that one phase modulator 112 is arranged in the third transmission light path 1103, and the 90° polarization state rotator 1104 is arranged in the third transmission light path 1103, and the intermediate optical coupling unit 1108 is arranged in the second transmission light path 1102. It can be understood that the 90° polarization state rotator 1104 can be replaced by a 90° twisted polarization maintaining fiber, that is, the second transmission light path 1102 or the third transmission light path 1103 is selected as a 90° twisted polarization maintaining fiber.

[0137] The port X of the intermediate optical coupling unit 1108 receives an input light pulse, which is output from the port Y of the intermediate optical coupling unit 1108 to one port of the optical coupler 1101, which can be the port B or the port C. The optical coupler 1101 splits the light pulse into two pre-sub-light pulses, which are transmitted in different directions along the fourth transmission light path 1106, pass through the pre-phase modulator 1107, and enter the optical coupling unit 1101 from the port A and the port D of the optical coupling unit 1101. The optical coupling unit 1101 reflects and transmits the two pre-sub-light pulses to generate two sub-light pulses, and inputs the two sub-light pulses into the second transmission light path 1102 and the third transmission light path 1103 respectively through the port C and the port B. The two sub-light pulses are transmitted along the second transmission light path 1102 and the third transmission light path 1103 respectively, enter the optical coupler 1105 from different ports of the optical coupler 1105, and the optical coupler 1105 combines the two sub-light pulses and outputs them.

[0138] In another embodiment of the present application, the third optical coupling unit 31 can be an optical coupler, and the fourth optical coupling unit 32 can be a polarization beam splitter. The pre-interferometer can be a first pre-interferometer, i.e., a Sagnac interferometer, which includes the fourth transmission optical path, the third optical coupling unit 31, and the pre-phase modulator arranged on the fourth transmission optical path. FIG. 12 shows a specific structural schematic diagram of another polarization operation module according to an embodiment of the present application. As shown in FIG. 12, the polarization control optical path in the polarization operation module can include an optical coupler 1201 (i.e., the third optical coupling unit 31), a second transmission optical path 1202, a third transmission optical path 1203, a 90° polarization state rotator 1204 arranged on the second transmission optical path 1202 or the third transmission optical path 1203, a polarization beam splitter 1205 (i.e., the fourth optical coupling unit 32), a fourth transmission optical path 1206, a pre-phase modulator 1207, and an intermediate optical coupling unit 1208. The intermediate optical coupling unit 1208 is arranged on the second transmission optical path 1202 or the third transmission optical path 1203. In this embodiment, the eigenpolarization state of the polarization beam splitter 1205 is the eigenpolarization state of the polarization control optical path 111.

[0139] The difference between the polarization operation module shown in FIG. 11 and the polarization operation module shown in FIG. 12 lies in the device type of the fourth optical coupling unit 32. The internal device connection mode and the processing mode of the optical pulse of the polarization operation module shown in FIG. 12 are similar to those of the polarization operation module shown in FIG. 11, and thus will not be described here.

[0140] In another embodiment of the present application, the pre-interferometer can be a second pre-interferometer, i.e., a Mach-Zehnder interferometer. The second pre-interferometer can include a pre-optical coupling unit, a first pre-transmission optical path, a second pre-transmission optical path, a pre-phase modulator arranged in the first pre-transmission optical path or the second pre-transmission optical path, and a third optical coupling unit 31.

[0141] The third optical coupling unit 31 can be an optical coupler, and the fourth optical coupling unit 32 can be an optical coupler. FIG. 13 shows a specific structural diagram of another polarization operation module according to an embodiment of the present application. As shown in FIG. 13, the polarization control light path in the polarization operation module can include an optical coupler 1301 (i.e., the third optical coupling unit 31), a second transmission light path 1302, a third transmission light path 1303, a 90° polarization state rotator 1304 arranged on the second transmission light path 1302 or the third transmission light path 1303, an optical coupler 1305 (i.e., the fourth optical coupling unit 32), a first pre-transmission light path 1306, a second pre-transmission light path 1307, a pre-phase modulator 1308 arranged in the first pre-transmission light path 1306 or the second pre-transmission light path 1307, and a pre-optical coupling unit 1309. The polarization states of the two sub light pulses input into the optical coupler 1305 are the eigenpolarization states of the polarization control light path 111. It can be understood that the 90° polarization state rotator 1304 can be a half-wave plate or a 90° Faraday rotator. Alternatively, the 90° polarization state rotator 1304 can be replaced by a 90° twisted polarization maintaining optical fiber, i.e., the second transmission light path 1302 or the third transmission light path 1303 is selected as a 90° twisted polarization maintaining optical fiber.

[0142] In some embodiments, the pre-optical coupling unit 1309 can be an optical coupler.

[0143] The optical coupler 1301 can include four ports, i.e., a port A, a port B, a port C, and a port D. The optical coupler 1305 includes three ports, i.e., a port A', a port B', and a port C'. The pre-optical coupling unit 1309 includes three ports, i.e., a port X, a port Y, and a port Z. The port B and the port C of the optical coupler 1301 are connected to the port B' and the port C' of the optical coupler 1305 through the second transmission light path 1302 and the third transmission light path 1303, respectively. The port A and the port D of the optical coupler 1301 are connected to the port Y and the port Z of the pre-optical coupling unit 1309 through the second pre-transmission light path 1307 and the first pre-transmission light path 1306, respectively. The port X of the pre-optical coupling unit 1309 is an input port of the polarization control light path. The pre-phase modulator 1308 is configured to perform phase modulation on the input sub light pulse.

[0144] The front light coupling unit 1309 is configured to receive the input light pulse and split the light pulse into two front sub-light pulses which are input into the first front transmission light path 1306 and the second front transmission light path 1307 respectively. One of the two front sub-light pulses is phase-modulated by the front phase modulator 1308. The two front sub-light pulses reach the optical coupler 1301 simultaneously. The optical coupler 1301 is also configured to receive the two front sub-light pulses with a phase difference. The optical coupler 1301 reflects and transmits the two front sub-light pulses to input the two sub-light pulses into the second transmission light path 1302 and the third transmission light path 1303 through the port B and the port C respectively.

[0145] In the embodiment, the second front light interferometer is configured to control the intensity of the two sub-light pulses input into the second transmission light path and the third transmission light path.

[0146] FIG. 14 shows a specific structure of another polarization operation module according to an embodiment of the present application. The difference between the structure shown in FIG. 14 and the structure shown in FIG. 13 is that the fourth light coupling unit 32 is a polarization beam splitter. The working principle of the second front light interferometer is the same as that in the previous embodiment, which is not described herein. The internal device connection mode and the light pulse processing mode of the polarization operation module shown in FIG. 14 are similar to those of the polarization operation module shown in FIG. 13, which are not described herein.

[0147] In some embodiments, the third light coupling unit 31 and the fourth light coupling unit 32 are the same light coupling unit. The second transmission light path and the third transmission light path are the same transmission light path. The eigenpolarization state of the light coupling unit is the eigenpolarization state of the polarization control light path 111.

[0148] FIG. 15 shows another embodiment of a polarization operation module. In the embodiment, the second transmission light path and the third transmission light path are the same transmission light path. The same light coupling unit can be a polarization beam splitter. As shown in FIG. 15, the polarization operation module can include a polarization beam splitter 151, a transmission light path 152, and at least one phase modulator 112. The phase modulator 112 is arranged in the transmission light path 152 and is configured to phase-modulate one of the two input sub-light pulses or to phase-modulate the two sub-light pulses differently.

[0149] The polarization beam splitter 151 includes three ports, i.e., a first port A, a second port B, and a third port C. The first port of the polarization beam splitter 151 is the input and output port of the polarization control light path 111. The second port and the third port of the polarization beam splitter 151 are connected through the same transmission light path 152. In the embodiment, the eigenpolarization state of the polarization beam splitter 151 is the eigenpolarization state of the light coupling unit.

[0150] Figure 16 shows another embodiment of the polarization operation module. In this embodiment, the second transmission optical path and the third transmission optical path are the same transmission optical path. The same optical coupling unit includes four ports, which are port A, port B, port C and port D. The same optical coupling unit can include a polarization beam splitter, a first polarizer and a second polarizer. As shown in Figure 16, the polarization operation module can include a polarization beam splitter 161, a first polarizer 162, a second polarizer 163, a transmission optical path 164 and at least one phase modulator 112. The at least one phase modulator 112 can be arranged in the transmission optical path 164 for phase modulating one of the two input sub light pulses or for different phase modulating the two sub light pulses.

[0151] The polarization beam splitter 161 includes four ports, which are a first port, a second port, a third port and a fourth port. The first port of the polarization beam splitter 161 is the port A of the optical coupling unit, which is the input port of the polarization control optical path 111. The fourth port of the polarization beam splitter 161 is the port D of the optical coupling unit, wherein the first port or the fourth port is the output port of the polarization control optical path 111. The second port and the third port of the polarization beam splitter 161 are connected with the ports of the first side of the first polarizer 162 and the second polarizer 163, respectively. The port of the second side of the first polarizer 162 is the port B of the optical coupling unit, and the port of the second side of the second polarizer 163 is the port C of the optical coupling unit. The ports of the second side of the first polarizer 162 and the second polarizer 163 are connected by the transmission optical path 164. The angle between the polarization direction of the first polarizer 162 and one eigenpolarization state of the polarization beam splitter 161 is θ, and the angle between the polarization direction of the second polarizer 163 and the other eigenpolarization state of the polarization beam splitter 161 is δ; wherein θ, δ ≠ n·90°, n is an integer. In this embodiment, the eigenpolarization state of the polarization beam splitter 161 is the eigenpolarization state of the optical coupling unit.

[0152] Figure 17 shows another embodiment of the polarization operation module. In this embodiment, the second transmission optical path and the third transmission optical path are the same transmission optical path. The same optical coupling unit includes three ports, which are port A, port B and port C. The same optical coupling unit can include an optical beam splitter, a first polarizer and a second polarizer. As shown in Figure 17, the polarization operation module can include an optical beam splitter 171, a first polarizer 172 and a second polarizer 173, a transmission optical path 174 and at least one phase modulator 112. The at least one phase modulator 112 can be arranged in the transmission optical path 174 for phase modulating one of the two input sub light pulses or for different phase modulating the two sub light pulses.

[0153] The optical splitter 171 comprises three ports, which are a first port, a second port and a third port. The first port of the optical splitter 171 is port A of the same optical coupling unit, which is the input port of the polarization control light path 111. The second port and the third port of the optical splitter 171 are connected with the port of the first side of the first polarizer 172 and the port of the first side of the second polarizer 173 respectively, the port of the second side of the first polarizer 172 is port B of the same optical coupling unit, the port of the second side of the second polarizer 173 is port C of the same optical coupling unit, and the port of the second side of the first polarizer 172 and the port of the second side of the second polarizer 173 are connected through the transmission light path 174. The polarization direction of the first polarizer 172 is The polarization direction of the second polarizer 173 is The polarization direction of the first polarizer 172 is The polarization direction of the second polarizer 173 is Orthogonal to each other. The polarization direction of the first polarizer 172 is The polarization direction of the second polarizer 173 is The eigenpolarization state of the optical coupling unit.

[0154] As shown in FIG. 18, it is another embodiment structure schematic diagram of the polarization operation module. In this embodiment, the same optical coupling unit comprises four ports, which are port A, port B, port C and port D. The second transmission light path and the third transmission light path are the same transmission light path, and the same optical coupling unit can comprise an optical splitter, a first polarizer and a second polarizer. The difference between this embodiment and the embodiment shown in FIG. 17 is that the optical splitter 171 further comprises a fourth port, which is port D of the same optical coupling unit. The fourth port of the optical splitter 171 is the output port of the polarization control light path 111.

[0155] In the corresponding structures of FIG. 15-18, the two sub-pulses polarized and split in one polarization control optical path 111 have the same transmission path when combined, which has self-compensation function to environmental interference, and can stably generate polarization encoded quantum states, so that the generation of time phase encoded quantum states also has the advantages of anti-interference and high stability. In addition, in the corresponding structure, at least one phase modulator 112 is applied with a high-frequency modulation signal with a frequency higher than a specified threshold, so that the phase modulator has non-reciprocity to the modulation phase of the input light pulses in the forward and reverse directions, so that the phase modulator 112 can effectively modulate the phase of the light pulses input by the forward input optical port, and cannot effectively modulate the phase of the light pulses input by the reverse input optical port, so that when the light pulses input by the forward input optical port and the light pulses input by the reverse input optical port pass through the high-frequency modulated phase modulator 112, the light pulses input by the forward input optical port obtain phase modulation, and the light pulses input by the reverse input optical port have no phase modulation, forming a phase difference between the two light pulses, which can realize the encoding of 10GHz or higher speed time phase quantum states.

[0156] In some embodiments, the polarization encoding unit comprises N polarization operation modules connected in series, and N is a positive integer. By setting the angle between the eigenpolarization states of the polarization control optical paths in the N polarization operation modules, and the angle between the eigenpolarization states of the polarization control optical paths and the eigenpolarization states of the unequal arm polarization control interferometer, different quantum communication system encoding requirements can be met.

[0157] For example, when N is 2, the angle between the eigenpolarization states of the two polarization control optical paths can be set to n·22.5°, where n is an integer, and different polarization states of two groups of bases or three groups of bases can be prepared.

[0158] In one embodiment, the angle between the eigenpolarization states of the two polarization control optical paths can be realized by rotating at least one of the two polarization control optical paths. That is, by rotating any one of the two polarization control optical paths, the angle between the eigenpolarization states of the two polarization control optical paths can be adjusted.

[0159] In another embodiment, the polarization encoding unit 100 further comprises a polarization state rotator arranged between the two polarization control optical paths, and the angle between the eigenpolarization states of the two polarization control optical paths is adjusted by the polarization state rotator.

[0160] The polarization state rotator can be a half-wave plate or a Faraday rotator. The angle of rotation of the polarization state rotator can be n·22.5°, where n is an integer.

[0161] In another embodiment, the angle between the two polarization control light paths can be jointly adjusted by rotating one of the two polarization control light paths and setting a polarization state rotator.

[0162] For example, when N is 3, the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the second polarization control light path is set to l·90°, and the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the third polarization control light path is set to 22.5°±m·45° or 45°±m·90°, where l and m are integers, two groups of four polarization states or three groups of six polarization states can be prepared.

[0163] For example, when N is 3, the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the second polarization control light path is set to 22.5°±a·45° or 45°±a·90°, and the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the third polarization control light path is set to n·22.5°, where a and n are integers, two groups of four polarization states or three groups of six polarization states can also be prepared.

[0164] In one embodiment, the angle between the eigenpolarization states of the three polarization control light paths can be set by rotating the second polarization control light path to adjust the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the second polarization control light path, and rotating the third polarization control light path to adjust the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the third polarization control light path.

[0165] In another embodiment, the polarization encoding unit 100 further comprises a first polarization state rotator and / or a second polarization state rotator.

[0166] The first polarization state rotator is arranged between the first polarization control light path and the second polarization control light path, and the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the second polarization control light path is adjusted by the first polarization state rotator.

[0167] The second polarization state rotator is arranged between the second polarization control light path and the third polarization control light path, and the angle between the eigenpolarization state of the first polarization control light path and the eigenpolarization state of the third polarization control light path is adjusted by the first polarization state rotator and / or the second polarization state rotator.

[0168] The first polarization state rotator and the second polarization state rotator can be a half-wave plate or a Faraday rotator.

[0169] In yet another embodiment, the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the second polarization control optical path can be adjusted by rotating the second polarization control optical path and the first polarization state rotator. That is, the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the second polarization control optical path is adjusted by rotating the second polarization control optical path and setting the first polarization state rotator.

[0170] In yet another embodiment, the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the second polarization control optical path can be adjusted by rotating the second polarization control optical path and the first polarization state rotator. That is, the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the second polarization control optical path is adjusted by rotating the second polarization control optical path and setting the first polarization state rotator.

[0171] In one embodiment, the polarization encoding unit 100 further comprises N-1 optical isolation units, which are optical isolators or optical circulators, and the N-1 optical isolation units are arranged between any two adjacent polarization operation modules.

[0172] It should be noted that in the case of multiple polarization operation modules in series, the structure of each polarization operation module can adopt any of the structures shown in Figures 15-18. The structures of any two polarization operation modules can be the same or different.

[0173] In some embodiments, the polarization state of the optical pulse input into the polarization operation module is Alternatively, the polarization state of the optical pulse input into the polarization operation module is where n is an integer, and are the two eigenpolarization states of the polarization control optical path (for the case of N>1, the first polarization control optical path) in the polarization encoding unit, and β is any value between 0 and 2π. For example, the polarization state of the optical pulse input into the polarization operation module can be 45° linear polarization, -45° linear polarization, left-handed circular polarization or right-handed circular polarization.

[0174] In some embodiments, the unequal-arm polarization control interferometer 300 comprises a fifth optical coupling unit, a sixth optical coupling unit, a fifth transmission optical path and a sixth transmission optical path, wherein the fifth optical coupling unit comprises at least three ports, one input port and two output ports; the sixth optical coupling unit comprises at least three ports, two input ports and one output port, the two output ports of the fifth optical coupling unit are connected with the two input ports of the sixth optical coupling unit through the fifth transmission optical path and the sixth transmission optical path; the input port of the fifth optical coupling unit is the input port of the unequal-arm polarization control interferometer, the output port of the sixth optical coupling unit is the output port of the unequal-arm polarization control interferometer, the optical path length of the fifth transmission optical path is not equal to that of the sixth transmission optical path, so that the two sub-pulses transmitted through the fourth transmission optical path and the fifth transmission optical path produce time delay when combined and output.

[0175] As shown in FIG. 19, it is a schematic diagram of an embodiment structure of the unequal-arm polarization control interferometer 300, in which the fifth optical coupling unit is a polarization beam splitter 1901, the sixth optical coupling unit is a polarization beam combiner 1902, and the eigenpolarization state of the polarization beam splitter 1901 is the eigenpolarization state of the unequal-arm polarization control interferometer 300. The polarization beam splitter 1901 and the polarization beam combiner 1902 are connected through the fifth transmission optical path 1903 and the sixth transmission optical path 1904 with unequal optical path lengths, respectively.

[0176] As shown in FIG. 20, it is another schematic diagram of an embodiment structure of the unequal-arm polarization control interferometer 300, in which the fifth optical coupling unit is a polarization beam splitter 2001, the sixth optical coupling unit is an optical coupler 2002, and the eigenpolarization state of the polarization beam splitter 2001 is the eigenpolarization state of the unequal-arm polarization control interferometer 300. The polarization beam splitter 2001 and the optical coupler 2002 are connected through the fifth transmission optical path 2003 and the sixth transmission optical path 2004 with unequal optical path lengths, respectively. Optionally, the fifth transmission optical path 2003 or the sixth transmission optical path 2004 is a 90° twisted polarization maintaining optical fiber, or the unequal-arm polarization control interferometer 300 further comprises a 90° polarization state rotator 2005, which is arranged on the fifth transmission optical path 2003 or the sixth transmission optical path 2004 and used for rotating the polarization state of the passing sub-pulse by 90°. The 90° polarization state rotator 2005 is a half-wave plate or a 90° Faraday rotator.

[0177] Figure 21 shows a schematic diagram of another embodiment of the unequal-arm polarization control interferometer 300, in which the fifth optical coupling unit is an optical coupler 2101, and the sixth optical coupling unit is a polarization beam combiner 2102, and the eigenpolarization state of the polarization beam combiner 2102 is the eigenpolarization state of the unequal-arm polarization control interferometer 300. The optical coupler 2101 and the polarization beam combiner 2102 are connected by the fifth transmission optical path 2103 and the sixth transmission optical path 2104, respectively, which have unequal optical path lengths.

[0178] Figure 22 shows a schematic diagram of another embodiment of the unequal-arm polarization control interferometer 300, in which the fifth optical coupling unit is an optical coupler 2201, and the sixth optical coupling unit is an optical coupler 2202. The unequal-arm polarization control interferometer further comprises two polarizers, i.e., a polarizer 2203 and a polarizer 2204, which are arranged on the fifth transmission optical path 2205 and the sixth transmission optical path 2206, respectively. In this embodiment, one output port of the optical coupler 2201 is connected to a port on the first side of the polarizer 2203, and the polarizer 2203 is configured to polarize one of the sub light pulses output by the optical coupler 2201. Another output port of the optical coupler 2201 is connected to a port on the first side of the polarizer 2204, and the polarizer 2204 is configured to polarize another of the sub light pulses output by the optical coupler 2201, and the polarization directions of the two polarizers 2203 and 2204 are orthogonal to each other. The other port on the second side of the polarizer 2203 and the other port on the second side of the polarizer 2204 are connected to the optical coupler 2202 via the fifth transmission optical path 2205 and the sixth transmission optical path 2206, respectively. In this embodiment, the polarization directions of the two polarizers are the eigenpolarization state directions of the unequal-arm polarization control interferometer. Optionally, the fifth transmission optical path 2205 or the sixth transmission optical path 2206 is a 90° twisted polarization maintaining optical fiber, or the unequal-arm polarization control interferometer 300 further comprises a 90° polarization state rotator 2207 arranged on the fifth transmission optical path 2205 or the sixth transmission optical path 2206, which is configured to rotate the polarization state of the sub light pulse passing therethrough by 90°, and the 90° polarization state rotator 2207 is a half-wave plate or a 90° Faraday rotator.

[0179] As shown in FIG. 23, it is another embodiment structure diagram of the unequal-arm polarization control interferometer 300, in which the fifth light coupling unit and the sixth light coupling unit are the same polarization beam splitter 2301, and the eigenpolarization state of the polarization beam splitter 2301 is the eigenpolarization state of the unequal-arm polarization control interferometer. The unequal-arm polarization control interferometer 300 further comprises two mirrors, i.e. mirror 2302 and mirror 2303, and the two output ports of the polarization beam splitter 2301 are connected with one end of the fifth transmission light path 2304 and one end of the sixth transmission light path 2305 respectively, and the two mirrors 2302 and 2303 are connected with the other end of the fifth transmission light path 2304 and the other end of the sixth transmission light path 2305 respectively, and the two mirrors 2302 and 2303 are used to reflect the input sub-light pulse back to the polarization beam splitter 2301. Optionally, the two mirrors 2302 and 2303 can be quarter-wave plate mirrors or 90° Faraday rotating mirrors, which are used to rotate the polarization state of the input sub-light pulse by 90°. Alternatively, the two mirrors 2302 and 2303 are polarization state rotating mirrors, which are used to rotate the polarization state of the input sub-light pulse by 45° or other preset angles.

[0180] It should be noted that the polarization beam splitter 2301 can include three ports or four ports.

[0181] As shown in FIG. 24, it is another embodiment structure diagram of the unequal-arm polarization control interferometer 300, in which the fifth light coupling unit and the sixth light coupling unit are the same light coupler 2401, and the unequal-arm polarization control interferometer 300 further comprises two mirrors 2402 and 2403 and two polarizers 2404 and 2405.

[0182] The two output ports of the light coupler 2401 are connected with one end of the fifth transmission light path and one end of the sixth transmission light path respectively, and the two mirrors 2402 and 2403 are connected with the other end of the fifth transmission light path and the other end of the sixth transmission light path respectively; the two polarizers 2404 and 2405 are arranged on the fifth transmission light path and the sixth transmission light path respectively, and the polarization directions of the two polarizers 2404 and 2405 are orthogonal to each other; and the polarization directions of the two polarizers 2404 and 2405 are the eigenpolarization state directions of the unequal-arm polarization control interferometer.

[0183] In some embodiments, the unequal-arm polarization control interferometer 300 further comprises a polarizer arranged at the output port of the unequal-arm polarization control interferometer 300, which is used to polarize the output light pulse.

[0184] In some embodiments, the quantum state encoding apparatus further comprises a quarter wave plate arranged between the polarization encoding unit 100 and the first optical coupling unit 200, or arranged between the first optical coupling unit 200 and the unequal-arm polarization control interferometer 300.

[0185] In some embodiments, the angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be n·22.5°, where n is an integer.

[0186] In one embodiment, the angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be adjusted by rotating at least one of the polarization control optical path and the unequal-arm polarization control interferometer 300.

[0187] Specifically, the angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be adjusted by rotating the polarization control optical path. Alternatively, the angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be adjusted by rotating the unequal-arm polarization control interferometer 300. Alternatively, the angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be adjusted by rotating the polarization control optical path and the unequal-arm polarization control interferometer 300.

[0188] In another embodiment, the quantum state encoding apparatus further comprises a polarization state rotator arranged between the polarization control optical path and the unequal-arm polarization control interferometer 300, and the angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be adjusted by the polarization state rotator.

[0189] In yet another embodiment, the angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be adjusted by rotating the polarization control optical path and / or the unequal-arm polarization control interferometer 300 and the polarization state rotator.

[0190] In other embodiments, when the polarization encoding unit 100 comprises N polarization operation modules connected in series, the angle between the eigenpolarization state of the polarization control optical path of the polarization operation module connected with the unequal-arm polarization control interferometer 300 and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be n·22.5°, where n is an integer.

[0191] In one embodiment, the angle between the eigenpolarization state of the polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer 300 and the eigenpolarization state of the unequal-arm polarization control interferometer 300 is adjusted by rotating at least one of the polarization operation module connected with the unequal-arm polarization control interferometer 300 and the unequal-arm polarization control interferometer 300.

[0192] Specifically, the angle between the eigenpolarization state of the polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer 300 and the eigenpolarization state of the unequal-arm polarization control interferometer 300 is adjusted by rotating the polarization operation module connected with the unequal-arm polarization control interferometer 300. Alternatively, the angle between the eigenpolarization state of the polarization control light path and the eigenpolarization state of the unequal-arm polarization control interferometer 300 is adjusted by rotating the unequal-arm polarization control interferometer 300. Alternatively, the angle between the eigenpolarization state of the polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer 300 and the eigenpolarization state of the unequal-arm polarization control interferometer 300 is adjusted by rotating the polarization operation module connected with the unequal-arm polarization control interferometer 300 and the unequal-arm polarization control interferometer 300.

[0193] In another embodiment, the quantum state encoding device further comprises a polarization state rotator. The polarization state rotator is arranged between the polarization operation module connected with the unequal-arm polarization control interferometer and the unequal-arm polarization control interferometer 300, and the angle between the eigenpolarization state of the polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer and the eigenpolarization state of the unequal-arm polarization control interferometer 300 is adjusted by the polarization state rotator.

[0194] In yet another embodiment, the angle between the eigenpolarization state of the polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer 300 and the eigenpolarization state of the unequal-arm polarization control interferometer 300 can be adjusted by rotating the polarization operation module connected with the unequal-arm polarization control interferometer 300 and / or the unequal-arm polarization control interferometer 300 and the polarization state rotator.

[0195] For further understanding of the quantum state encoding device provided by the embodiments of the present application, in which the polarization encoding unit adopts two polarization operation modules connected in series, the polarization operation module adopts the structure shown in FIG. 16, the unequal-arm polarization control interferometer adopts the structure shown in FIG. 19, and the structure of the quantum state encoding device is shown in FIG. 25.

[0196] In some embodiments, according to the requirements of quantum communication, the quantum state encoding device of the present application can also be used in the quantum state decoding process.

[0197] According to the present application, a quantum state encoding method is provided, and the method is implemented by using the quantum state encoding device.

[0198] The present application further provides a software-defined quantum communication system, as shown in FIG. 26, which comprises the quantum state encoding device 2601 and the encoding control device 2602. The encoding control device 2602 is used to generate quantum communication encoding control instructions based on the encoding requirements of the quantum communication system, and send the quantum communication encoding control instructions to the quantum state encoding device 2601, so that the quantum state encoding device 2601 selects the polarized encoded quantum state light pulse or the time phase encoded quantum state light pulse based on the quantum communication encoding control instructions.

[0199] The quantum communication system can be a discrete variable quantum communication system or a continuous variable quantum communication system.

[0200] It should be understood that the specific features, operations and details described above with respect to the device of the present application can also be similarly applied to the method and system of the present application, or vice versa.

[0201] The technical features described above can be combined arbitrarily. Although all possible combinations of the technical features are not described, any combination of the technical features should be considered to be covered by the present specification, as long as there is no contradiction in such combination.

[0202] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the above embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A quantum state encoding device, wherein, include: The system comprises a polarization encoding unit, a first optical coupling unit, an unequal-arm polarization control interferometer, a first transmission optical path, and a second optical coupling unit. The polarization encoding unit includes at least one input port and one output port. The polarization encoding unit is used to input a light pulse through one of the input ports, generate a light pulse with a polarization-coded quantum state based on the input light pulse, and output it through the output port. The first optical coupling unit includes one input port and two output ports, namely the first port, the second port and the third port, and the first port is connected to the output port of the polarization encoding unit; The second optical coupling unit includes two input ports and one output port, namely the fourth port, the fifth port, and the sixth port; The unequal-arm polarization control interferometer includes an input port and an output port, used to perform time-phase encoding conversion on the input polarization-encoded quantum state light pulse and output the time-phase encoded quantum state light pulse; The third port of the first optical coupling unit is connected to the input port of the unequal-arm polarization control interferometer, and the output port of the unequal-arm polarization control interferometer is connected to the fifth port of the second optical coupling unit, forming the first optical output branch; The second port of the first optical coupling unit is connected to the fourth port of the second optical coupling unit through the first transmission optical path to form a second optical output branch; The first optical coupling unit is used to input the light pulse of the polarization-coded quantum state output by the polarization coding unit into the first optical output branch and / or the second optical output branch according to the quantum communication coding control command. The quantum communication coding control command is determined according to the coding requirements of the quantum communication system. The sixth port of the second optical coupling unit is the output port of the quantum state encoding device, which is used to output the optical pulse of the polarization-encoded quantum state transmitted by the second optical output branch or the optical pulse of the time-phase-encoded quantum state transmitted by the first optical output branch according to the quantum communication encoding control command.

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

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

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

5. The apparatus of claim 4, wherein, The first optical coupling unit is used to selectively input the optical pulse of the polarization-coded quantum state to the first optical output branch or the second optical output branch according to the quantum communication encoding control command; when the second optical coupling unit is an optical switch, the second optical coupling unit is configured to connect a first optical output branch outputting time-phase encoding quantum state light pulses or a second optical output branch outputting polarization encoding quantum state light pulses according to the quantum communication encoding control instruction; when the second optical coupling unit is an optical coupler, the second optical coupling unit is configured to output time-phase encoding quantum state light pulses transmitted by the first optical output branch or polarization encoding quantum state light pulses transmitted by the second optical output branch.

6. The apparatus of claim 1, wherein, The polarization encoding unit comprises a polarization operation module, and the polarization operation module comprises a polarization control optical path and at least one phase modulator arranged in a transmission optical path of the polarization control optical path. The polarization control optical path is configured to split one input light pulse into two sub light pulses. The phase modulator is configured to perform phase modulation on at least one sub light pulse based on a modulation signal, so that a specific phase difference is generated between the two sub light pulses. The polarization control optical path is further configured to combine the two sub light pulses with the phase difference and output the generated polarization encoding quantum state light pulse.

7. The apparatus of claim 6, wherein, The polarization control optical path comprises a third optical coupling unit, a fourth optical coupling unit, a second transmission optical path, and a third transmission optical path. The third optical coupling unit and the fourth optical coupling unit are connected through the second transmission optical path and the third transmission optical path. The third optical coupling unit is configured to split one input light pulse into two sub light pulses, i.e., a first sub light pulse and a second sub light pulse, and the first sub light pulse and the second sub light pulse are transmitted along the second transmission optical path and the third transmission optical path respectively, and then combined by the fourth optical coupling unit after passing through the at least one phase modulator.

8. The apparatus of claim 7, wherein, The third optical coupling unit and the fourth optical coupling unit are the same optical coupler, and the polarization control optical path further comprises two mirrors. The optical coupler comprises at least three ports, at least one input port, and two output ports, and the two output ports are connected with the two mirrors through the second transmission optical path and the third transmission optical path respectively, and the two mirrors are configured to reflect the input light pulses back to the optical coupler, and one of the two mirrors is a quarter-wave plate mirror or a 90° Faraday rotation mirror.

9. The apparatus of claim 7, wherein, The third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter, and the polarization control optical path further comprises two mirrors. The polarization beam splitter comprises at least three ports, at least one input port, and two output ports, and the two output ports are connected with the two mirrors through the second transmission optical path and the third transmission optical path respectively, and the two mirrors are configured to reflect the input light pulses back to the polarization beam splitter.

10. The apparatus of claim 7, wherein, The third optical coupling unit is a polarization beam splitter, and the fourth optical coupling unit is an optical coupler or a polarization beam splitter.

11. The apparatus of claim 7, wherein, The third optical coupling unit is an optical coupler, and the fourth optical coupling unit is an optical coupler or a polarization beam splitter.

12. The apparatus of claim 11, wherein, The second transmission optical path or the third transmission optical path is a 90° polarization maintaining optical fiber; or The polarization control optical path further comprises: a 90° polarization state rotator arranged on the second transmission optical path or the third transmission optical path, and the polarization state rotator is used for rotating the polarization state of the passing sub-light pulse by 90°.

13. The apparatus of claim 11 or 12, wherein, The polarization control optical path further comprises: a first pre-light interferometer and an intermediate optical coupling unit, wherein the first pre-light interferometer comprises the third optical coupling unit, a fourth transmission optical path, and a pre-phase modulator arranged on the fourth transmission optical path; The intermediate optical coupling unit is arranged in the second transmission optical path or the third transmission optical path, and is used for receiving an input light pulse and inputting it to the first pre-light interferometer; The first pre-light interferometer is used for splitting the input light pulse into two pre-sub-light pulses and generating a phase difference between the two pre-sub-light pulses through the pre-phase modulator; The two ports of the third optical coupling unit are connected through the fourth transmission optical path, and are used for splitting the light pulse input by the intermediate optical coupling unit into two pre-sub-light pulses and inputting the two pre-sub-light pulses from different ports into the fourth transmission optical path; The pre-phase modulator is used for phase modulating one of the two pre-sub-light pulses transmitted in the fourth transmission optical path based on a modulation signal, or differently phase modulating the two pre-sub-light pulses, so as to generate a phase difference between the two pre-sub-light pulses; The third optical coupling unit is also used for reflecting and transmitting the two pre-sub-light pulses with a phase difference generated after the pre-phase modulator, generating two sub-light pulses, and inputting the two sub-light pulses into the second transmission optical path and the third transmission optical path through different ports.

14. The apparatus of claim 11 or 12, wherein, The polarization control optical path further comprises: a second pre-light interferometer, the second pre-light interferometer comprises: a pre-optical coupling unit, a first pre-transmission optical path, a second pre-transmission optical path, a pre-phase modulator arranged in the first pre-transmission optical path or the second pre-transmission optical path, and the third optical coupling unit, The pre-optical coupling unit is connected with the two input ports of the third optical coupling unit through the first pre-transmission optical path and the second pre-transmission optical path respectively, and the pre-optical coupling unit is used for splitting an input light pulse into two pre-sub-light pulses and inputting the two pre-sub-light pulses into the first pre-transmission optical path and the second pre-transmission optical path respectively; The pre-phase modulator is used for phase modulating one of the two pre-sub-light pulses based on a modulation signal, so as to generate a phase difference between the two pre-sub-light pulses input into the third optical coupling unit; The third optical coupling unit is used for reflecting and transmitting the two pre-sub-light pulses with a phase difference input from different ports, generating two sub-light pulses, and inputting the two sub-light pulses into the second transmission optical path and the third transmission optical path through different ports. The third optical coupling unit and the fourth optical coupling unit are the same optical coupling unit, and the second transmission optical path and the third transmission optical path are the same transmission optical path.

15. The apparatus of claim 7, wherein, ​ 16. The apparatus of claim 15, wherein, The same optical coupling unit is a polarization beam splitter, the polarization beam splitter includes three ports, which are a first port, a second port and a third port, the first port of the polarization beam splitter is an input and output port of the polarization control optical path, the second port and the third port of the polarization beam splitter are connected through the same transmission optical path, and an intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the polarization control optical path.

17. The apparatus of claim 15, wherein, The same optical coupling unit includes a polarization beam splitter, a first polarizer and a second polarizer. The polarization beam splitter includes four ports, which are 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 polarization control optical path, and the first port or the fourth port of the polarization beam splitter is an output port of the polarization control optical path; the second port and the third port of the polarization beam splitter are connected with a port on a first side of the first polarizer and a port on a first side of the second polarizer respectively; a port on a second side of the first polarizer and a port on a second side of the second polarizer are connected through a transmission optical path; an angle between a polarization direction of the first polarizer and one intrinsic polarization state of the polarization beam splitter is θ, and an angle between a polarization direction of the second polarizer and another intrinsic polarization state of the polarization beam splitter is δ; wherein θ, δ ≠ n·90°, n is an integer, and an intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the polarization control optical path.

18. The apparatus of claim 15, wherein, The same optical coupling unit includes a polarization beam splitter, a first polarizer and a second polarizer. The optical beam splitter comprises at least three ports, respectively a first port, a second port and a third port, the first port of the optical beam splitter is the input port and the output port of the polarization control optical path; the second port and the third port of the optical beam splitter are connected with the port of the first side of the first polarizer and the port of the first side of the second polarizer respectively; the port of the second side of the first polarizer and the port of the second side of the second polarizer are connected through a transmission optical path, the polarization direction of the first polarizer is The second polarizer has a polarization direction that is a polarization direction of the first polarizer a polarizing direction of the second polarizer orthogonal to each other, the polarizing direction of the first polarizer a polarizing direction of the second polarizer The intrinsic polarization state of the polarization control optical path.

19. The apparatus of claim 15, wherein, The same optical coupling unit includes a polarization beam splitter, a first polarizer and a second polarizer. The optical splitter comprises four ports, respectively a first port, a second port, a third port and a fourth port, the first port of the optical splitter is the input port of the polarization control optical path; the second port and the third port of the optical splitter are connected with the port of the first side of the first polarizer and the port of the first side of the second polarizer respectively; the port of the second side of the first polarizer and the port of the second side of the second polarizer are connected through a transmission optical path; the fourth port of the optical splitter is the output port of the polarization control optical path, and the polarization direction of the first polarizer is a polarization direction of the second polarizer is a polarization direction of the first polarizer the polarizing direction of the second polarizer is The intrinsic polarization state of the polarization control optical path.

20. The apparatus of any of claims 15-19, wherein, The phase modulator includes a forward input light port and a reverse input light port, and the phase modulator works in a non-reciprocal state after a high-frequency modulation signal with a frequency higher than a specified threshold is applied, and a ratio of a modulation efficiency of a light pulse input by the forward input light port to a modulation efficiency of a light pulse input by the reverse input light port is greater than a preset threshold.

21. The apparatus of any one of claims 15-19, wherein, The polarization encoding unit includes N polarization operation modules connected in series, and N is a positive integer.

22. The apparatus of claim 21, wherein, When N is 2, an angle between the intrinsic polarization states of the two polarization control optical paths is n·22.5°, wherein n is an integer.

23. The apparatus of claim 22, wherein, The angle between the intrinsic polarization states of the two polarization control optical paths is realized by rotating at least one of the two polarization control optical paths; and / or The polarization encoding unit further includes a polarization state rotator arranged between the two polarization control optical paths, and the angle between the intrinsic polarization states of the two polarization control optical paths is adjusted by the polarization state rotator.

24. The apparatus of claim 21, wherein, When N is 3, when the angle between the intrinsic polarization state of the first polarization control optical path and the intrinsic polarization state of the second polarization control optical path is 22.5°±l·45°, or 45°±l·90°, the angle between the intrinsic polarization state of the first polarization control optical path and the intrinsic polarization state of the third polarization control optical path is 22.5°±m·45°, or 45°±m·90°, wherein l and m are integers. When the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the second polarization control optical path is 22.5°±a·45° or 45°±a·90°, the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the third polarization control optical path is n·22.5°, wherein a and n are integers.

25. The apparatus of claim 24, wherein, The angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the second polarization control optical path is achieved by rotating the second polarization control optical path, and the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the third polarization control optical path is achieved by rotating the third polarization control optical path; and / or, The polarization encoding unit further comprises a first polarization state rotator and / or a second polarization state rotator, The first polarization state rotator is arranged between the first polarization control optical path and the second polarization control optical path, and the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the second polarization control optical path is adjusted by the first polarization state rotator. The second polarization state rotator is arranged between the second polarization control optical path and the third polarization control optical path, and the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the third polarization control optical path is adjusted by the first polarization state rotator and / or the second polarization state rotator.

26. The apparatus of claim 21, wherein, The polarization encoding unit further comprises N-1 optical isolation units, which are optical isolators or optical circulators, and the N-1 optical isolation units are arranged between any two adjacent polarization operation modules.

27. The apparatus of claim 1, wherein, The polarization state of the optical pulses input to the polarization encoding unit is Or, The polarization state of the optical pulses input to the polarization encoding unit is wherein n is an integer, and β is any value between 0 and 2π for the two eigenpolarization states of the polarization control optical path in the polarization encoding unit.

28. The apparatus of claim 1, wherein, The unequal-arm polarization control interferometer comprises 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 comprises at least three ports, one input port and two output ports; the sixth optical coupling unit comprises at least three ports, two input ports and one output port, the two output ports of the fifth optical coupling unit are connected to the two input ports of the sixth optical coupling unit through the fifth transmission optical path and the sixth transmission optical path; the input port of the fifth optical coupling unit is the input port of the unequal-arm polarization control interferometer, the output port of the sixth optical coupling unit is the output port of the unequal-arm polarization control interferometer, and the optical path lengths of the fifth transmission optical path and the sixth transmission optical path are not equal.

29. The apparatus of claim 28, wherein, The fifth optical coupling unit is a polarization beam splitter, and the sixth optical coupling unit is a polarization beam combiner, and the eigenpolarization state of the polarization beam splitter is the eigenpolarization state of the unequal-arm polarization control interferometer.

30. The apparatus of claim 28, wherein, The fifth optical coupling unit is a polarization beam splitter, and the sixth optical coupling unit is an optical coupler, and the eigenpolarization state of the polarization beam splitter is the eigenpolarization state of the unequal-arm polarization control interferometer.

31. The apparatus of claim 28, wherein, The fifth light coupling unit is a light coupler, and the sixth light coupling unit is a polarization beam combiner, and an intrinsic polarization state of the polarization beam combiner is an intrinsic polarization state of the unequal-arm polarization control interferometer.

32. The apparatus of claim 28, wherein, The fifth light coupling unit is a light coupler, and the sixth light coupling unit is a light coupler, and the unequal-arm polarization control interferometer further comprises two polarizers, The two polarizers are respectively arranged on the fifth transmission light path and the sixth transmission light path, and polarization directions of the two polarizers are orthogonal to each other, and the polarization directions of the two polarizers are intrinsic polarization state directions of the unequal-arm polarization control interferometer. The fifth light coupling unit and the sixth light coupling unit are the same polarization beam splitter, and the unequal-arm polarization control interferometer further comprises two mirrors, 33. The apparatus of claim 28, wherein, The two output ports of the polarization beam splitter are respectively connected with one end of the fifth transmission light path and one end of the sixth transmission light path, and the two mirrors are respectively connected with the other end of the fifth transmission light path and the other end of the sixth transmission light path, and an intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the unequal-arm polarization control interferometer. The two mirrors are quarter-wave plate mirrors or 90° Faraday rotation mirrors.

34. The apparatus of claim 33, wherein, The fifth light coupling unit and the sixth light coupling unit are the same light coupler, and the unequal-arm polarization control interferometer further comprises two mirrors and two polarizers, 35. The apparatus of claim 28, wherein, The two output ports of the light coupler are respectively connected with one end of the fifth transmission light path and one end of the sixth transmission light path, and the two mirrors are respectively connected with the other end of the fifth transmission light path and the other end of the sixth transmission light path; the two polarizers are respectively arranged on the fifth transmission light path and the sixth transmission light path, and polarization directions of the two polarizers are orthogonal to each other; and the polarization directions of the two polarizers are intrinsic polarization state directions of the unequal-arm polarization control interferometer. The fifth transmission light path or the sixth transmission light path is a 90° twisted polarization maintaining optical fiber, or 36. The apparatus of claim 30 or 32, wherein, The unequal-arm polarization control interferometer further comprises a 90° polarization state rotator, The 90° polarization state rotator is arranged on the fifth transmission light path or the sixth transmission light path, and is used for rotating a polarization state of a sub-light pulse passing through by 90°. The unequal-arm polarization control interferometer further comprises a polarizer.

37. The apparatus of any one of claims 28-35, wherein, The polarizer is arranged on an output port of the unequal-arm polarization control interferometer, and is used for polarizing an output light pulse. An included angle between the intrinsic polarization state of the polarization control optical path and the intrinsic polarization state of the unequal-arm polarization control interferometer is n·22.5°, wherein n is an integer.

38. The apparatus of any one of claims 16-19, wherein, The included angle between the intrinsic polarization state of the polarization control optical path and the intrinsic polarization state of the unequal-arm polarization control interferometer is realized by rotating at least one of the polarization control optical path and the unequal-arm polarization control interferometer; and / or 39. The device of claim 38, wherein, The device further comprises a polarization state rotator arranged between the polarization control optical path and the unequal-arm polarization control interferometer, and the included angle between the intrinsic polarization state of the polarization control optical path and the intrinsic polarization state of the unequal-arm polarization control interferometer is adjusted through the polarization state rotator. ​ 40. The apparatus of claim 21, wherein, The polarization encoding unit comprises N polarization operation modules connected in series, and an angle between an eigenpolarization state of a polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer and an eigenpolarization state of the unequal-arm polarization control interferometer is n·22.5°, where n is an integer.

41. The apparatus of claim 40, wherein, The angle between the eigenpolarization state of the polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer and the eigenpolarization state of the unequal-arm polarization control interferometer is realized by rotating at least one of the polarization operation module connected with the unequal-arm polarization control interferometer and the unequal-arm polarization control interferometer; and / or The device further comprises a polarization state rotator arranged between the polarization operation module connected with the unequal-arm polarization control interferometer and the unequal-arm polarization control interferometer, and the angle between the eigenpolarization state of the polarization control light path of the polarization operation module connected with the unequal-arm polarization control interferometer and the eigenpolarization state of the unequal-arm polarization control interferometer is adjusted by the polarization state rotator.

42. The device of claim 1, wherein, The device further comprises a quarter-wave plate arranged between the polarization encoding unit and the first light coupling unit, or arranged between the first light coupling unit and the unequal-arm polarization control interferometer.

43. A method of encoding a quantum state, wherein, The quantum state encoding device is applied to quantum state encoding.

44. A software-defined quantum communication system, wherein, The quantum state encoding device comprises the quantum state encoding device and an encoding control device. The encoding control device is used to generate quantum communication encoding control instructions based on quantum communication system encoding requirements, and send the quantum state encoding device. The quantum state encoding device is applied to quantum state encoding. The quantum state encoding device comprises the quantum state encoding device and an encoding control device. The encoding control device is used to generate quantum communication encoding control instructions based on quantum communication system encoding requirements, and send the quantum state encoding device.

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