Time phase encoding apparatus, method and quantum communication system

Abstract

The application provides a time-phase encoding device, a method and a quantum communication system. The device comprises a first polarization operation module, a second polarization operation module, a third polarization operation module and an unequal arm polarization control interferometer connected in series. The three polarization operation modules each comprise a polarization control light path and a phase modulator. The unequal arm polarization control interferometer comprises a first optical coupling unit, a second optical coupling unit and a transmission light path with unequal optical paths. The included angle between the intrinsic polarization states of the polarization control light paths of the three polarization operation modules and the included angle between the polarization control light path of the first polarization operation module and the intrinsic polarization states of the unequal arm polarization control interferometer are set, and the phase difference of the combined modulation of the three polarization operation modules is matched, so as to meet the requirements of various quantum communication protocols. The application can realize the generation of X base / Y base phase base and Z base time base quantum states.

Description

TECHNICAL FIELD

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

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

[0003] The physical implementation of a quantum communication system, such as the physical implementation of quantum key distribution and quantum direct communication, requires encoding and decoding of quantum states. In an optical fiber quantum communication system, time-phase coding (including phase coding) has advantages such as resistance to channel environment disturbance and efficient coding, and is valued by the industry. It has become the main coding method for quantum communication.

[0004] How to compatibly support multiple quantum communication protocols in the same optical quantum coding device and implement multiple time-phase quantum state coding is an important problem in the current application of quantum communication. SUMMARY

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

[0006] According to a first aspect of the present application, a time-phase coding device is provided, comprising: a first polarization operation module, a second polarization operation module, a third polarization operation module and a non-equal arm polarization control interferometer connected in series.

[0007] The first polarization operation module comprises a first polarization control optical path and a first phase modulator arranged in a transmission light path of the first polarization control optical path. The first polarization control optical path is used to split an input light pulse into two sub-light pulses, i.e. a first sub-light pulse and a second sub-light pulse. The first phase modulator is used to modulate the phase of the first sub-light pulse and / or the second sub-light pulse, so that a phase difference φ is generated between the two sub-light pulses. The first sub-light pulse and the second sub-light pulse after the first phase modulator are combined and output through the first polarization control optical path. One of the two eigenpolarization states of the first polarization control optical path is

[0008] The second polarization operation module comprises a second polarization control optical path and a second phase modulator arranged in a transmission light path of the second polarization control optical path, the second polarization control optical path is connected in series with the first polarization control optical path, the second polarization control optical path is used for inputting the light pulses output by the first polarization control optical path from an input port, splitting the light pulses into two sub light pulses, i.e. a third sub light pulse and a fourth sub light pulse, and the second phase modulator is used for phase modulating the third sub light pulse and / or the fourth sub light pulse to generate a phase difference between the two sub light pulses The third sub light pulse and the fourth sub light pulse after passing through the second phase modulator are output by the second polarization control optical path; one of the two eigenpolarizations of the second polarization control optical path is

[0009] The third polarization operation module comprises a third polarization control optical path and a third phase modulator arranged in a transmission light path of the third polarization control optical path, the third polarization control optical path is connected in series with the first polarization control optical path and the second polarization control optical path, the third polarization control optical path is used for inputting the light pulses output by the second polarization control optical path from an input port, splitting the light pulses into two sub light pulses, i.e. a fifth sub light pulse and a sixth sub light pulse, and the third phase modulator is used for phase modulating the fifth sub light pulse and / or the sixth sub light pulse to generate a phase difference γ between the two sub light pulses, the fifth sub light pulse and the sixth sub light pulse after passing through the third phase modulator are output by the third polarization control optical path; one of the two eigenpolarizations of the third polarization control optical path is

[0010] The unequal-arm polarization control interferometer comprises a first optical coupling unit, a second optical coupling unit, a first transmission control optical path and a second transmission control optical path; the first optical coupling unit comprises at least three ports, one input port and two output ports; the second optical coupling unit comprises at least three ports, two input ports and one output port; the two output ports of the first optical coupling unit are connected with the two input ports of the second optical coupling unit through the first transmission control optical path and the second transmission control optical path respectively, and the optical paths of the first transmission control optical path and the second transmission control optical path are not equal

[0011] The light pulse output by the third polarization control light path is input into the unequal-arm polarization control interferometer through the input port of the first optical coupling unit of the unequal-arm polarization control interferometer, the input light pulse is split into two sub light pulses, i.e., a seventh sub light pulse and an eighth sub light pulse, by the first optical coupling unit, and the seventh sub light pulse and the eighth sub light pulse are transmitted along the first transmission control light path and the second transmission control light path respectively and then combined into one light pulse output by the second optical coupling unit of the unequal-arm polarization control interferometer; one of the two eigenpolarizations of the unequal-arm polarization control interferometer is

[0012] The angle between the eigenpolarization and the eigenpolarization , the angle between the eigenpolarization and the eigenpolarization , and the angle between the eigenpolarization and the eigenpolarization are set, and the phase difference φ, the phase difference and the phase difference γ are matched to meet the requirements of different quantum communication protocols.

[0013] According to a second aspect of the present application, a time-phase encoding method is provided, which is implemented by using the time-phase encoding device described above.

[0014] According to a third aspect of the present application, a quantum communication system is provided, which comprises the time-phase encoding device described above.

[0015] In summary, the time-phase encoding device, method and quantum communication system provided by the present application have at least the following beneficial effects:

[0016] The time-phase encoding device provided by the present application comprises a first polarization operation module, a second polarization operation module, a third polarization operation module and an unequal-arm polarization control interferometer connected in series, wherein the first polarization operation module, the second polarization operation module and the third polarization operation module each comprise a polarization control light path and a phase modulator, and the unequal-arm polarization control interferometer comprises a first optical coupling unit, a second optical coupling unit and an unequal optical path transmission light path; the angle between the eigenpolarization and , the angle between the eigenpolarization and , and the angle between the eigenpolarization and the eigenpolarization of the unequal-arm polarization control interferometer are set.The three polarization operation modules are connected in series with the unequal arm polarization control interferometer, and the three polarization operation modules can generate three groups of six polarization encoding quantum states. The unequal arm polarization control interferometer converts the polarization encoding quantum state into a time phase encoding quantum state, thereby providing more implementation ways for generating X base / Y base phase base and Z base time base quantum states. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the specific embodiments or prior art in the present application, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0018] Figure 1 A structural block diagram of a time phase encoding device provided by an embodiment of the present application is provided.

[0019] Figure 2 An embodiment structural diagram of a time phase encoding device provided by an embodiment of the present application is provided.

[0020] Figure 3 A first embodiment structural diagram of an unequal arm polarization control interferometer provided by an embodiment of the present application is provided.

[0021] Figure 4 A second embodiment structural diagram of an unequal arm polarization control interferometer provided by an embodiment of the present application is provided.

[0022] Figure 5 A third embodiment structural diagram of an unequal arm polarization control interferometer provided by an embodiment of the present application is provided.

[0023] Figure 6 A fourth embodiment structural diagram of an unequal arm polarization control interferometer provided by an embodiment of the present application is provided.

[0024] Figure 7 A fifth embodiment structural diagram of an unequal arm polarization control interferometer provided by an embodiment of the present application is provided.

[0025] Figure 8 A sixth embodiment structural diagram of an unequal arm polarization control interferometer provided by an embodiment of the present application is provided.

[0026] Figure 9 A first embodiment structural diagram of a polarization control optical path provided by an embodiment of the present application is provided.

[0027] Figure 10A structural diagram of a second embodiment of the polarization control optical path provided for the purposes of this application;

[0028] Figure 11 A structural diagram of a third embodiment of the polarization control optical path provided for the purposes of this application;

[0029] Figure 12 The diagram shows a fourth embodiment of the polarization control optical path provided in this application. Detailed Implementation

[0030] To make the above and other features and advantages of this application clearer, the application is further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explanation to those skilled in the art, and are exemplary only, not restrictive.

[0031] In the following description, numerous specific details are set forth to provide a thorough understanding of this application. However, it will be apparent to those skilled in the art that the specific details are not required to practice this application. In other instances, well-known steps or operations have not been described in detail to avoid obscuring this application.

[0032] It should be noted that the time phase encoding described in this application includes phase encoding, that is, the time phase encoding is an encoding composed of any combination of quantum states of the X phase basis, Y phase basis, and Z time basis.

[0033] This application provides a time phase encoding device, as shown in the attached document. Figure 1 and attached Figure 2 As shown, attached Figure 1 Here is a structural block diagram of the time phase encoding device, with appendix. Figure 2 The diagram shows a structural embodiment of the time-phase encoding device, which includes: a first polarization operation module 100, a second polarization operation module 200, a third polarization operation module 300, and an unequal-arm polarization control interferometer 400 connected in series.

[0034] In some implementations, such as Figure 2 As shown, the first polarization operation module 100 includes: a first polarization control optical path and a transmission optical path disposed in the first polarization control optical path (e.g., Figure 2a first phase modulator 205 in the first transmission optical path 204 in the first polarization control optical path 203); the first polarization control optical path is used to split an input light pulse into two sub light pulses, a first sub light pulse and a second sub light pulse, and the first phase modulator 205 is used to modulate the phase of the first sub light pulse and / or the second sub light pulse, so that a phase difference φ is generated between the two sub light pulses, and the first sub light pulse and the second sub light pulse after the first phase modulator 205 are combined and output by the first polarization control optical path; the two eigenpolarizations of the first polarization control optical path are and respectively represent the horizontal direction and the vertical direction.

[0035] In an exemplary embodiment, the first phase modulator 205 is used to modulate the phase of the first sub light pulse and / or the second sub light pulse, including: modulating the phase of one of the first sub light pulse and the second sub light pulse, or modulating the phase of the first sub light pulse and the second sub light pulse differently.

[0036] In an exemplary embodiment, the first phase modulator 205 includes a first port E, a second port F, and a third port (not shown in the figure), the first port E and the second port F are respectively the forward input optical port and the reverse input optical port of the first phase modulator 205, the first sub light pulse is input into the first phase modulator 205 through the first port E and output by the second port F after passing through the first phase modulator 205, and the second sub light pulse is input into the first phase modulator 205 through the second port F and output by the first port E after passing through the first phase modulator 205, the third port is an electrical port connected with a first driver (not shown in the figure) for receiving a modulation electrical signal applied by the first driver.

[0037] In an embodiment, the first phase modulator 205 is arranged in the first transmission optical path 204, and the first transmission optical path 204 is coupled with the slow axis of the first port E and the second port F of the first phase modulator 205, or is coupled with the fast axis of the first port E and the second port F of the first phase modulator 205. The first phase modulator 205 modulates one of the light pulses input through the first port E and the second port F, or modulates the light pulses input through the first port E and the second port F differently.

[0038] In an exemplary embodiment, the first phase modulator 205 works in a non-reciprocal state when a modulating electrical signal with a frequency higher than a specified threshold is applied to the first phase modulator 205, and the ratio of the modulating efficiency of the first sub light pulse input from the forward input optical port (i.e., the first port E) to the modulating efficiency of the second sub light pulse input from the reverse input optical port (i.e., the second port F) is not less than a preset threshold. In one embodiment, the preset threshold can be 10 decibels (dB). The modulating signal can be, for example, a modulating signal with a frequency not less than 10 GHz. Non-reciprocity is a physical concept that describes whether a certain physical process is equal to its inverse process. If equal, it is called reciprocal; if not equal, it is called non-reciprocal. In this application, non-reciprocity refers to the fact that an optical wave exhibits different characteristics such as loss and phase shift when transmitted in opposite directions in an optical transmission path.

[0039] It can be understood that when the modulating electrical signal with a frequency higher than a specified threshold is applied to the first phase modulator 205, the modulating efficiency of the reverse transmission light pulse (i.e., the second sub light pulse) input from the second port F is much lower than the modulating efficiency of the forward transmission light pulse (i.e., the first sub light pulse) input from the first port E. That is, the first phase modulator 205 can effectively perform phase modulation on the light pulse transmitted forward through the first phase modulator 205, but cannot effectively perform phase modulation on the light pulse transmitted backward through the first phase modulator 205. When the two sub light pulses pass through the first phase modulator 205 at the same time, if the same modulating electrical signal pulse is applied to the two sub light pulses transmitted forward and backward, a phase difference can be formed between the first sub light pulse and the second sub light pulse; if different modulating electrical signals are applied to the first phase modulator 205, different phase differences are formed between the first sub light pulse and the second sub light pulse, so that different polarization states of light pulses are generated when the light pulses are output by the first polarization control optical path.

[0040] In some embodiments, the second polarization operation module 200 includes a second polarization control optical path and a second phase modulator 210 disposed in a transmission optical path (e.g., the second transmission optical path 209) of the second polarization control optical path. The second polarization control optical path is connected in series with the first polarization control optical path. The second polarization control optical path is configured to input the light pulse output by the first polarization control optical path from an input port, split the light pulse into two sub light pulses, i.e., a third sub light pulse and a fourth sub light pulse. The second phase modulator 210 is configured to perform phase modulation on the third sub light pulse and / or the fourth sub light pulse, so that a phase difference is generated between the two sub light pulses. Figure 2 ​The third sub-light pulse and the fourth sub-light pulse after passing through the second phase modulator 210 are output through the second polarization control optical path; the two eigenpolarizations of the second polarization control optical path are and

[0041] In an example embodiment, the second phase modulator 210 is configured to perform phase modulation on the third sub-light pulse and / or the fourth sub-light pulse, including: the second phase modulator 210 is configured to perform phase modulation on one of the third sub-light pulse and the fourth sub-light pulse, or to perform different phase modulation on the third sub-light pulse and the fourth sub-light pulse.

[0042] In an example embodiment, the second phase modulator 210 includes: a fourth port K, a fifth port L, and a sixth port (not shown in the figure), the fourth port K and the fifth port L are a forward input optical port and a reverse input optical port of the second phase modulator 210 respectively, the third sub-light pulse is input into the second phase modulator 210 through the fourth port K and output from the fifth port L after passing through the second phase modulator 210, the fourth sub-light pulse is input into the second phase modulator 210 through the fifth port L and output from the fourth port K after passing through the second phase modulator 210, and the sixth port is an electrical port connected with a second driver (not shown in the figure) for receiving a modulation electrical signal applied by the second driver.

[0043] In an example embodiment, the second phase modulator 210 is arranged in the second transmission optical path 209, and the second transmission optical path 209 is coupled with the slow axis of the fourth port K and the fifth port L of the second phase modulator 210, or coupled with the fast axis of the fourth port K and the fifth port L of the second phase modulator 210. The second phase modulator 210 performs phase modulation on one of the light pulses input through the fourth port K and the fifth port L, or performs different phase modulation on the light pulses input through the fourth port K and the fifth port L.

[0044] In an example embodiment, when the second phase modulator 210 is applied with a modulation electrical signal with a frequency higher than a specified threshold, the second phase modulator 210 works in a non-reciprocal state, and the ratio of the modulation efficiency of the third sub-light pulse input through the forward input optical port (i.e. the fourth port K) to the modulation efficiency of the fourth sub-light pulse input through the reverse input optical port (i.e. the fifth port L) is not less than a preset threshold.

[0045] It can be understood that when the modulation electrical signal with the frequency higher than the specified threshold is applied to the second phase modulator 210, the modulation efficiency of the second phase modulator 210 on the reverse transmission optical pulse (i.e., the fourth sub optical pulse) input from the fifth port L is much lower than the modulation efficiency on the forward transmission optical pulse (i.e., the third sub optical pulse) input from the fourth port K. That is, the second phase modulator 210 can effectively perform phase modulation on the optical pulse transmitted forwardly through the second phase modulator 210 at each high-speed modulation, and cannot effectively perform phase modulation on the optical pulse transmitted reversely through the second phase modulator 210. When the two sub optical pulses pass through the second phase modulator 210 simultaneously at high speed, if the same modulation electrical signal pulse is applied to the two sub optical pulses transmitted forwardly and reversely, a phase difference can be formed between the third sub optical pulse and the fourth sub optical pulse; if different modulation electrical signals are applied to the second phase modulator 210, the phase difference formed between the third sub optical pulse and the fourth sub optical pulse is different, so that the optical pulses with different polarization states are generated by modulation when the second polarization control optical path is combined and output.

[0046] In some embodiments, the third polarization operation module 300 includes a third polarization control optical path and a third phase modulator 215 arranged in a transmission optical path (such as the third transmission optical path 214) of the third polarization control optical path. The third polarization control optical path is connected in series with the first polarization control optical path and the second polarization control optical path. The third polarization control optical path is used to input the optical pulse combined and output by the second polarization control optical path from an input port, split the optical pulse into two sub optical pulses, i.e., a fifth sub optical pulse and a sixth sub optical pulse. The third phase modulator 215 is used to perform phase modulation on the fifth sub optical pulse and / or the sixth sub optical pulse, so that a phase difference γ is generated between the two sub optical pulses. The fifth sub optical pulse and the sixth sub optical pulse after the third phase modulator 215 are combined and output by the third polarization control optical path. Figure 2 The two eigenpolarizations of the third polarization control optical path are and

[0047] In an exemplary embodiment, the third phase modulator 215 is used to perform phase modulation on the fifth sub optical pulse and / or the sixth sub optical pulse, including that the third phase modulator 215 is used to perform phase modulation on one of the fifth sub optical pulse and the sixth sub optical pulse, or perform different phase modulation on the fifth sub optical pulse and the sixth sub optical pulse.

[0048] In an example embodiment, the third phase modulator 215 comprises a seventh port T, an eighth port U and a ninth port (not shown in the figure), the seventh port T and the eighth port U are the forward input optical port and the reverse input optical port of the third phase modulator 215 respectively, the fifth sub light pulse is input into the third phase modulator 215 through the seventh port T and output from the eighth port U after passing through the third phase modulator 215, the sixth sub light pulse is input into the third phase modulator 215 through the eighth port U and output from the seventh port T after passing through the third phase modulator 215, the ninth port is an electrical port, connected with a third driver (not shown in the figure) for receiving a modulation electrical signal applied by the third driver.

[0049] In an example embodiment, the third phase modulator 215 is arranged in the third transmission light path 214, the third transmission light path 214 is coupled with the slow axis of the seventh port T and the eighth port U of the third phase modulator 215 or coupled with the fast axis of the seventh port T and the eighth port U of the third phase modulator 215. The third phase modulator 215 modulates one of the light pulses input from the seventh port T and the eighth port U or modulates the light pulses input from the seventh port T and the eighth port U with different phase modulation.

[0050] In an example embodiment, when the third phase modulator 215 is applied with a modulation electrical signal with a frequency higher than a specified threshold, the third phase modulator 215 works in a non-reciprocal state, the ratio of the modulation efficiency of the fifth sub light pulse input from the forward input optical port (i.e. the seventh port T) to the modulation efficiency of the sixth sub light pulse input from the reverse input optical port (i.e. the eighth port U) is not less than a preset threshold.

[0051] It can be understood that when the third phase modulator 215 is applied with the modulation electrical signal with the frequency higher than the specified threshold, the modulation efficiency of the reverse transmission light pulse (i.e. the sixth sub light pulse) input from the eighth port U is much lower than the modulation efficiency of the forward transmission light pulse (i.e. the fifth sub light pulse) input from the seventh port T. That is, the third phase modulator 215 can effectively modulate the light pulse passing through the third phase modulator 215 in the forward transmission direction but cannot effectively modulate the light pulse passing through the third phase modulator 215 in the reverse transmission direction each time the third phase modulator 215 is modulated at a high speed. When two sub light pulses pass through the third phase modulator 215 modulated at a high speed at the same time, if the same modulation electrical signal is applied to the two sub light pulses in the forward transmission and the reverse transmission, a phase difference can be formed between the fifth sub light pulse and the sixth sub light pulse; if different modulation electrical signals are applied to the third phase modulator 215, the phase difference formed between the fifth sub light pulse and the sixth sub light pulse is different, so that the light pulses with different polarization states are generated by modulation when the light pulses are output from the third polarization control light path.

[0052] The phase modulator of the present application, when a high frequency modulation signal with a frequency higher than a specified threshold is applied, at the same time, there can be multiple forward input optical ports input sub light pulses and reverse input optical port input sub light pulses.

[0053] In some embodiments, as shown in Figure 2 The unequal arm polarization control interferometer 400 includes a first optical coupling unit 216, a second optical coupling unit 217, a first transmission control optical path 218 and a second transmission control optical path 219; the first optical coupling unit 216 includes at least three ports, port V is the input port of the first optical coupling unit 216, ports X and W are two output ports of the first optical coupling unit 216; the second optical coupling unit 217 includes at least three ports, ports M and Y are two input ports of the second optical coupling unit 217, and port N is the output port of the second optical coupling unit 217; the two output ports of the first optical coupling unit 216 are connected with the two input ports of the second optical coupling unit 217 through the first transmission control optical path 218 and the second transmission control optical path 219 respectively, and the optical paths of the first transmission control optical path 218 and the second transmission control optical path 219 are not equal.

[0054] In an exemplary embodiment, the light pulse output by the third polarization operation module 300 is input into the unequal arm polarization control interferometer 400 through the first optical coupling unit 216 of the unequal arm polarization control interferometer 400, the input light pulse is again split into two sub light pulses by the first optical coupling unit 216, which are the seventh sub light pulse and the eighth sub light pulse, respectively, and the seventh sub light pulse and the eighth sub light pulse are transmitted along the first transmission control optical path 218 and the second transmission control optical path 219 respectively, and then combined into a light pulse output by the second optical coupling unit 217 of the unequal arm polarization control interferometer 400; the two eigenpolarizations of the unequal arm polarization control interferometer 400 are and

[0055] As shown in Figure 3 is an embodiment structure diagram of the unequal arm polarization control interferometer 400, in which embodiment, the first optical coupling unit is a polarization beam splitter 301, and the second optical coupling unit is a polarization beam combiner 302, and the eigenpolarization of the polarization beam splitter 301 is the eigenpolarization of the unequal arm polarization control interferometer 400. The polarization beam splitter 301 and the polarization beam combiner 302 are connected through the first transmission control optical path 303 and the second transmission control optical path 304 with unequal optical paths, respectively.

[0056] As shown in Figure 4Another embodiment of the unequal-arm polarization control interferometer 400 is shown in FIG. 4B, in which the first optical coupling unit is a polarization beam splitter 401, the second optical coupling unit is an optical coupler 402, and the eigenpolarization state of the polarization beam splitter 401 is the eigenpolarization state of the unequal-arm polarization control interferometer 400. The polarization beam splitter 401 and the optical coupler 402 are connected by the first transmission control optical path 403 and the second transmission control optical path 404, respectively, which have unequal optical path lengths. Optionally, the first transmission control optical path 403 or the second transmission control optical path 404 is a 90° polarization state rotator 405, which is a half-wave plate or a 90° Faraday rotator, and is arranged on the first transmission control optical path 403 or the second transmission control optical path 404 to rotate the polarization state of the sub-pulses passing therethrough by 90°.

[0057] As shown in FIG. 4C, Figure 5 Another embodiment of the unequal-arm polarization control interferometer 400 is shown in FIG. 4D, in which the first optical coupling unit is an optical coupler 501, the second optical coupling unit is a polarization beam combiner 502, and the eigenpolarization state of the polarization beam combiner 502 is the eigenpolarization state of the unequal-arm polarization control interferometer 400. The optical coupler 501 and the polarization beam combiner 502 are connected by the first transmission control optical path 503 and the second transmission control optical path 504, respectively, which have unequal optical path lengths.

[0058] As shown in FIG. 4E, Figure 6The diagram shows another embodiment of the unequal-arm polarization control interferometer 400. In this embodiment, the first optical coupling unit is an optical coupler 601, and the second optical coupling unit is an optical coupler 602. The unequal-arm polarization control interferometer also includes two polarizers, polarizer 603 and polarizer 604, which are respectively disposed on the first transmission control optical path 605 and the second transmission control optical path 606. One output port of the optical coupler 601 is connected to the first side port of the polarizer 603, and the polarizer 603 is used to polarize one sub-light pulse output by the optical coupler 601. The other output port of the optical coupler 601 is connected to the first side port of the polarizer 604, and the polarizer 604 is used to polarize another sub-light pulse output by the optical coupler 601. The polarization directions of the two polarizers 603 and 604 are orthogonal to each other. The other ports of polarizer 603 and polarizer 604 are connected to optical coupler 602 via first transmission control optical path 605 and second transmission control optical path 606, respectively. In this embodiment, the polarization direction of the two polarizers is the intrinsic polarization state direction of the unequal-arm polarization control interferometer. Optionally, the first transmission control optical path 605 or the second transmission control optical path 606 is a 90° twisted polarization-maintaining fiber, or the unequal-arm polarization control interferometer 400 further includes a 90° polarization state rotator 607, which is disposed on the first transmission control optical path 605 or the second transmission control optical path 606 and is used to rotate the polarization state of the passing sub-light pulse by 90°. The 90° polarization state rotator 607 is a half-wave plate or a 90° Faraday rotator.

[0059] like Figure 7 The diagram shows another embodiment of the unequal-arm polarization control interferometer 400. In this embodiment, the first optical coupling unit and the second optical coupling unit are the same polarization beamsplitter 701, and the intrinsic polarization state of the polarization beamsplitter 701 is the intrinsic polarization state of the unequal-arm polarization control interferometer. The unequal-arm polarization control interferometer 400 further includes two mirrors, mirror 702 and mirror 703. The two output ports of the polarization beamsplitter 701 are respectively connected to one end of the first transmission control optical path 704 and one end of the second transmission control optical path 705. The two mirrors 702 and 703 are respectively connected to the other end of the first transmission control optical path 704 and the other end of the second transmission control optical path 705. The two mirrors 702 and 703 are used to reflect the input sub-light pulses back to the polarization beamsplitter 701. Optionally, the two mirrors 702 and 703 can be quarter-wave plate mirrors or 90° Faraday rotation mirrors, used to rotate the polarization state of the input sub-light pulses by 90°. Alternatively, the two reflectors 702 and 703 can be polarization state rotating reflectors, used to rotate the polarization state of the input sub-light pulse by 45° or other preset angles.

[0060] It should be noted that the polarization beam splitter 701 can include three ports or four ports.

[0061] As Figure 8 shown is another embodiment structure diagram of the unequal-arm polarization control interferometer 400, in the embodiment, the first light coupling unit and the second light coupling unit are the same light coupler 801, and the unequal-arm polarization control interferometer 400 further includes two mirrors 802 and 803 and two polarizers 804 and 805.

[0062] The two output ports of the light coupler 801 are connected with one end of the first transmission control light path 806 and one end of the second transmission control light path 807 respectively, and the two mirrors 802 and 803 are connected with the other end of the first transmission control light path 806 and the other end of the second transmission control light path 807 respectively; the two polarizers 804 and 805 are arranged on the first transmission control light path 806 and the second transmission control light path 807 respectively, and the polarization directions of the two polarizers 804 and 805 are orthogonal to each other; the polarization directions of the two polarizers 804 and 805 are the eigenpolarization state directions of the unequal-arm polarization control interferometer.

[0063] In some embodiments, the device can further include a light polarizer connected with the output port N of the second light coupling unit, for polarizing the light pulse output by the second light coupling unit.

[0064] In some embodiments, the device further includes a quarter-wave plate arranged between the third polarization control light path and the unequal-arm polarization control interferometer 400. In some embodiments, the included angle between the quarter-wave plate and the eigenpolarization state of the unequal-arm polarization control interferometer 400 can be n·45°.

[0065] It should be noted that the structures of the first polarization control light path, the second polarization control light path and the third polarization control light path in the time phase encoding device shown in Figure 2 may be only one embodiment structure, and the first polarization control light path, the second polarization control light path and the third polarization control light path described in the present application can adopt the structures shown in Figures 9 to 12 respectively. The structures of the three polarization control light paths can be the same or different. That is, the three polarization control light paths can respectively adopt any one of the four structures provided in the embodiment of the present application. Figures 9 to 12 Similarly, the structure of the unequal-arm polarization control interferometer 400 can be only one embodiment structure, and the structure of the unequal-arm polarization control interferometer 400 described in the present application is not limited to Figures 2 to 8 ​The structure of the unequal-arm polarization control interferometer 400 can be any type of structure that can be implemented, as long as it is based on this application.

[0066] In one exemplary implementation, such as Figure 9 The diagram shows a first embodiment of a polarization control optical path. In this embodiment, the polarization control optical path includes a polarization beam splitter unit and a transmission optical path 204. The polarization beam splitter unit includes at least three ports, namely port A, port B, and port C. The intrinsic polarization state of the polarization beam splitter unit is... and The polarization beam splitter unit splits the optical pulse input from port A into two sub-pulses, which are output from ports B and C respectively. The transmission optical path 204 connects ports B and C of the polarization beam splitter unit. In this case, the polarization control optical path also includes an optical circulator (not shown in the figure), which is located at the front end of port A. The optical circulator has three ports: a first port, a second port, and a third port. The first port of the optical circulator is the input port of the polarization control optical path, and the third port is the output port. The second port of the optical circulator is connected to port A. The optical pulse input from the first port of the optical circulator is output through the second port, and the optical pulse input from the second port is output through the third port. In this embodiment, the polarization beam splitter unit is a polarization beam splitter, and therefore, the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the polarization beam splitter unit.

[0067] In one exemplary implementation, such as Figure 10The diagram shows a second embodiment of the polarization control optical path. In this embodiment, the polarization beam splitter unit includes: a polarization beam splitter 201, a first polarizer 202, and a second polarizer 203. The polarization beam splitter unit also includes port D. The polarization beam splitter 201 includes four ports, namely a first port, a second port, a third port, and a fourth port. The first port of the polarization beam splitter 201 is port A of the polarization beam splitter unit, and the fourth port of the polarization beam splitter 201 is port D of the polarization beam splitter unit. The second and third ports of the polarization beam splitter 201 are respectively connected to the first port of the first polarizer 202 and the second port. The first port of polarizer 203 is connected; the second port of the first polarizer 202 is port B of the polarization beam splitter unit, and the second port of the second polarizer 203 is port C of the polarization beam splitter unit; the second ports of the first polarizer 202 and the second ports of the second polarizer 203 are connected through the first transmission optical path 204; the angle between the polarization direction of the first polarizer 202 and one intrinsic polarization state of the polarization beam splitter 201 is θ, and the angle between the polarization direction of the second polarizer 203 and another intrinsic polarization state of the polarization beam splitter 201 is δ; where θ and δ ≠ 90°, and n is an integer. The angle between the polarization direction of the first polarizer 202 and the polarization direction of the second polarizer 203 is ω, 0 ≤ ω ≤ 2π. In this embodiment, the intrinsic polarization state of the polarization beam splitter 201 is the intrinsic polarization state of the polarization beam splitter unit.

[0068] In some embodiments, the first polarizer 202 may be bonded to the second port of the polarization beam splitter 201, and the second polarizer 203 may be bonded to the third port of the polarization beam splitter 201.

[0069] In one exemplary implementation, such as Figure 11 The diagram shows a third embodiment of the polarization control optical path. In this embodiment, the polarization beam splitting unit includes: an optical beam splitter 201, a first polarizer 202, and a second polarizer 203. The optical beam splitter 201 includes at least three ports, namely a first port, a second port, and a third port. The first port of the optical beam splitter 201 is port A of the polarization beam splitting unit. The second and third ports of the optical beam splitter 201 are respectively connected to the first side ports of the first polarizer 202 and the first side ports of the second polarizer 203. The second side port of the first polarizer 202 is port B of the polarization beam splitting unit, and the second side port of the second polarizer 203 is port C of the polarization beam splitting unit. The second side ports of the first polarizer 202 and the second side ports of the second polarizer 203 are connected through a first transmission optical path 204. The polarization direction of the first polarizer 202 is... The polarization direction of the second polarizer 203 is The direction of the first polarizer 202 The polarization direction of the second polarizer 203 orthogonal to each other; the polarizing direction a of the first polarizer 202 is orthogonal to the polarizing direction b of the second polarizer 203 is the eigenpolarization state of the polarization beam splitting unit.

[0070] In an exemplary embodiment, as shown in Figure 12 Fig. 4 is a fourth embodiment of the polarization control optical path, in which the polarization beam splitting unit comprises an optical beam splitter 201, a first polarizer 202 and a second polarizer 203; the polarization beam splitting unit further comprises a port D; the optical beam splitter 201 comprises four ports, which are a first port, a second port, a third port and a fourth port, respectively; the first port of the optical beam splitter 201 is the port A of the polarization beam splitting unit, and the fourth port of the optical beam splitter 201 is the port D of the polarization beam splitting unit; the second port and the third port of the optical beam splitter 201 are connected to the port on the first side of the first polarizer 202 and the port on the first side of the second polarizer 203, respectively; the port on the second side of the first polarizer 202 is the port B of the polarization beam splitting unit, and the port on the second side of the second polarizer 203 is the port C of the polarization beam splitting unit; the port on the second side of the first polarizer 202 and the port on the second side of the second polarizer 203 are connected by a first transmission optical path 204. The polarizing direction a of the first polarizer 202 is the polarizing direction b of the second polarizer 203 is the polarizing direction a of the first polarizer 202 is orthogonal to the polarizing direction b of the second polarizer 203 orthogonal to each other; the polarizing direction a of the first polarizer 202 is orthogonal to the polarizing direction b of the second polarizer 203 orthogonal to the polarizing direction b of the second polarizer 203 is the eigenpolarization state of the polarization beam splitting unit.

[0071] In some embodiments, the first transmission optical path 204, the second transmission optical path 209 and the third transmission optical path 214 can be free-space optical paths or polarization-maintaining optical fibers. In an exemplary embodiment, both ports of the polarization beam splitting unit are coupled to the slow axis of the polarization-maintaining optical fiber or are coupled to the fast axis of the polarization-maintaining optical fiber. Figure 9 For example, as shown in Fig. 4, the first transmission optical path 204 is a polarization-maintaining optical fiber, and at this time, the port B and the port C of the polarization beam splitting unit are coupled to the slow axis of the polarization-maintaining optical fiber or are coupled to the fast axis of the polarization-maintaining optical fiber.

[0072] In an exemplary embodiment, the device further comprises a half-wave plate or a 90-degree Faraday rotator arranged in the transmission optical path, and the polarization states of the two sub-optical pulses in the transmission optical path can be controlled through the half-wave plate or the 90-degree Faraday rotator, so that the transmission paths of the two sub-optical pulses in the transmission optical path and the phase modulator are consistent, and the phase drifts of the two sub-optical pulses caused by environmental interference are the same, thereby accurately controlling the phase difference between the two sub-optical pulses through the modulation of the phase modulator.

[0073] In some embodiments, the first phase modulator 205, the second phase modulator 210, and / or the third phase modulator 215 can be a single-polarization phase modulator or a birefringent phase modulator.

[0074] In an exemplary embodiment, based on the present application, the polarization states of the optical pulses can be modulated by modulating the three phase modulators, and the corresponding time-phase encoding quantum states can be modulated by the unequal-arm polarization control interferometer. The three phase modulators can be modulated according to the requirements of different quantum communication protocols: for example, the first phase modulator 205 can randomly modulate four phase states of 0°, 45°, 90°, or 135°; or randomly modulate four phase states of 45°, 90°, 135°, or 180°; or randomly modulate two phase states of 0° or 180°; or randomly modulate two phase states of 90° or 270°; or randomly modulate four phase states of 0°, 90°, 180°, or 270°. The second phase modulator 210 can have multiple modulation modes, such as randomly modulating two phase states of 0° or 180°; or randomly modulating two phase states of 0° or 90°; or randomly modulating two phase states of 90° or 270°; or randomly modulating four phase states of 0°, 90°, 180°, or 270°. The third phase modulator 215 can have multiple modulation modes, such as randomly modulating two phase states of 0° or 180°; or randomly modulating two phase states of 0° or 90°; or randomly modulating two phase states of 90° or 270°; or randomly modulating four phase states of 0°, 90°, 180°, or 270°.

[0075] In the present application, the included angle between the eigenpolarization state and the eigenpolarization state , the included angle between the eigenpolarization state and the eigenpolarization state , and the included angle between the eigenpolarization state and the eigenpolarization state of the unequal-arm polarization control interferometer, and the phase difference φ, the phase difference and the phase difference γ are matched to meet the requirements of different quantum communication protocols.

[0076] In an exemplary embodiment, the angle between the eigenpolarization state and the eigenpolarization state may be m-90°, or 22.5°±m-45°, or 45°±m-90°, where m is an integer.

[0077] In an exemplary embodiment, when the angle between the eigenpolarization state and the eigenpolarization state is l-90°, the angle between the eigenpolarization state and the eigenpolarization state may be 22.5°±m-45°, or 45°±m-90°, where l and m are integers.

[0078] In another exemplary embodiment, when the angle between the eigenpolarization state and the eigenpolarization state is 22.5°±a-45° or 45°±a-90°, the angle between the eigenpolarization state and the eigenpolarization state may be n-22.5°, where a and n are integers.

[0079] 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, 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,

[0080] The apparatus further comprises a first polarization state rotator and / or a second polarization state rotator,

[0081] The first polarization state rotator is disposed 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;

[0082] The second polarization state rotator is disposed 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.

[0083] In an exemplary embodiment, the device further comprises two optical isolation units, which are optical isolators or optical circulators, and the two optical isolation units are respectively arranged between the first polarization operation module and the second polarization operation module, and between the second polarization operation module and the third polarization operation module.

[0084] In an exemplary embodiment, the eigenpolarization state of the first polarization operation module and the eigenpolarization state of the unequal-arm polarization control interferometer may be an angle of b·22.5°, where b is an integer.

[0085] The angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer is achieved by rotating at least one of the first polarization control optical path and the unequal-arm polarization control interferometer; and / or

[0086] The device further comprises a polarization state rotator arranged between the first polarization control optical path and the unequal-arm polarization control interferometer, and the angle between the eigenpolarization state of the first polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer is adjusted by the polarization state rotator.

[0087] In an exemplary embodiment, the polarization state of the optical pulse input into the first polarization operation module is Alternatively, the polarization state of the optical pulse input into the first polarization operation module is Alternatively, the polarization state of the optical pulse input into the first polarization operation module is or wherein n is an integer, and are two eigenpolarization states of the first polarization control optical path of the first polarization operation module, and β is any value between 0 and 2π.

[0088] In an exemplary embodiment, the polarization state of the optical pulse input into the first polarization operation module is 45° linear polarization, -45° linear polarization, left-handed circular polarization or right-handed circular polarization.

[0089] The present application combines the modulation of the first phase modulator 205, the second phase modulator 210 and the third phase modulator 215, so that the output optical pulse can realize horizontal and vertical polarization bases ±45° polarization bases or left and right circular polarization bases Multiple combinations of polarization quantum states are generated, and the polarization encoding is further converted to time phase encoding through an unequal arm polarization control interferometer, thereby generating three sets of six time phase encoded quantum states (including phase encoded quantum states).

[0090] For example, suppose that the first polarization control optical path, the second polarization control optical path, and the third polarization control optical path are all selected Figure 2 The optical path structure is shown. The first, second, and third polarization control optical paths all maintain the intrinsic polarization state of the input unchanged at the output. For example, for the first polarization control optical path, the relationship between its input and output is as follows: (The negative sign indicates that it was taken into consideration) (Due to the polarization state being reflected twice by the polarization beam splitter). The intrinsic polarization state of the first polarization control optical path... With the intrinsic polarization state of the second polarization control optical path The included angle is configured as 22.5°; the intrinsic polarization state of the first polarization control optical path With the intrinsic polarization state of the third polarization control optical path The included angle is configured at 45°; the intrinsic polarization state of the first polarization control optical path Intrinsic polarization states of unequal-arm polarization control interferometer The included angle between them is configured as 0°. When the polarization state of the optical pulse input to the first polarization operation module is 45° linear polarization, if the first phase modulator 205 randomly modulates 0°, 90°, or 180°, that is, the phase difference φ is modulated to 0°, 90°, or 180°, the second phase modulator 210 modulates 0° (that is, no modulation), that is, the phase difference φ is modulated to 0°, 90°, or 180°. With the modulation set to 0°, and the third phase modulator 215 randomly modulating to 0° or 180°, i.e., the phase difference γ modulated to 0° or 180°, a ±45° polarization base can be prepared. and left-hand and right-hand circular polarization bases Two sets of four polarization states are used. After the polarization encoding is converted to phase encoding by the unequal arm polarization control interferometer 400, two phase states of X-based and two phase states of Y-based can be prepared.

[0091] If the first phase modulator 205 randomly modulates 0° or 180°, that is, the phase difference φ is modulated to 0° or 180°, and the second phase modulator 210 randomly modulates 0° or 180°, that is, the phase difference φ is modulated to 0° or 180°, then the phase difference φ is modulated to 0° or 180°. When the modulation is 0° or 180°, and the third phase modulator 215 is modulated at 0° (i.e., not modulated), meaning the phase difference γ is modulated to 0°, a horizontal and vertical polarization base can be prepared. and ±45° polarization base Two sets of four polarization states are used. After the polarization code is converted into time and phase code by the unequal arm polarization control interferometer 400, two phase states of X-based and two time bit states of Z-based can be prepared.

[0092] If the first phase modulator 205 randomly modulates 0° or 180°, the second phase modulator 210 modulates 180°, and the third phase modulator 215 randomly modulates 0° or 90°, the horizontal-vertical polarization basis and the left-right circular polarization basis The two sets of bases four polarization states, after the polarization encoding is converted into time phase encoding by the unequal arm polarization control interferometer 400, the Y basis two phase states and the Z basis two time bit states can be prepared;

[0093] If the first phase modulator 205 randomly modulates 0° or 180°, the second phase modulator 210 randomly modulates 0° or 180°, and the third phase modulator 215 randomly modulates 0° or 90°, the horizontal-vertical polarization basis ±45° polarization basis and the left-right circular polarization basis The three sets of bases six polarization states, after the polarization encoding is converted into time phase encoding by the unequal arm polarization control interferometer 400, the X basis / Y basis four phase states and the Z basis two time bit states can be prepared;

[0094] If the first phase modulator 205 randomly modulates 0° or 90°, the second phase modulator 210 randomly modulates 0° or 180°, and the third phase modulator 215 modulates 0°, the horizontal-vertical polarization basis ±45° polarization basis and the left-right circular polarization basis Three sets of bases four polarization states After the polarization encoding is converted into time phase encoding by the unequal arm polarization control interferometer 400, the X basis one phase state, the Y basis two phase states and the Z basis one time bit state can be prepared.

[0095] The time phase encoding device of the application comprises a first polarization operation module, a second polarization operation module, a third polarization operation module and an unequal arm polarization control interferometer connected in series, wherein the first polarization operation module, the second polarization operation module and the third polarization operation module each comprise a polarization control optical path and a phase modulator, and the unequal arm polarization control interferometer comprises a first optical coupling unit, a second optical coupling unit and an unequal optical path transmission optical path; by setting the included angle between the intrinsic polarization state and the included angle between the intrinsic polarization state and and and the intrinsic polarization state of the unequal arm polarization control interferometer The three polarization operation modules are combined with the phase difference of the modulation to meet the requirements of various quantum communication protocols. The device described in the application uses three polarization operation modules in series with the unequal arm interferometer. The three polarization operation modules can generate three groups of six polarization encoding quantum states. The unequal arm polarization control interferometer is used to convert the polarization encoding quantum state into a time phase encoding quantum state, which provides more implementation ways for generating X base / Y base phase base and Z base time base quantum states.

[0096] The time phase encoding device of the application can also be used in a time phase decoding process.

[0097] According to the application, a time phase encoding method is provided, which uses the time phase encoding device described above to realize time phase encoding.

[0098] The application provides a quantum communication system, which includes the time phase encoding device described above.

[0099] The quantum communication system can be a discrete variable quantum communication system or a continuous variable quantum communication system. The protocols of the quantum communication system include but are not limited to BB84, BBM92, E91, MDI, TF, reference frame independent, coherent state protocol, etc.

[0100] It should be understood that the specific features, operations and details described above with respect to the device of the application can be similarly applied to the method and system of the application, or vice versa.

[0101] 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 application, as long as there is no contradiction in such combination.

[0102] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they 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 application.

Claims

1. A time phase encoding device, characterized in that, include: The system consists of a first polarization operation module, a second polarization operation module, a third polarization operation module, and an unequal-arm polarization control interferometer connected in series. The first polarization operation module includes: a first polarization control optical path and a first phase modulator disposed in the transmission optical path of the first polarization control optical path; the first polarization control optical path is used to split an input optical pulse into two sub-optical pulses, namely a first sub-optical pulse and a second sub-optical pulse; the first phase modulator is used to perform phase modulation on the first sub-optical pulse and / or the second sub-optical pulse, so that a phase difference φ is generated between the two sub-optical pulses; the first sub-optical pulse and the second sub-optical pulse after passing through the first phase modulator are combined and output through the first polarization control optical path; one of the two intrinsic polarization states of the first polarization control optical path is... The second polarization operation module includes: a second polarization control optical path and a second phase modulator disposed in the transmission optical path of the second polarization control optical path. The second polarization control optical path is connected in series with the first polarization control optical path. The second polarization control optical path is used to input the optical pulse output from the beam combining output of the first polarization control optical path from the input port and split it into two sub-optical pulses, namely a third sub-optical pulse and a fourth sub-optical pulse. The second phase modulator is used to perform phase modulation on the third sub-optical pulse and / or the fourth sub-optical pulse, so that a phase difference is generated between the two sub-optical pulses. The third and fourth sub-pulses, after passing through the second phase modulator, are combined and output via the second polarization control optical path; one of the two intrinsic polarization states of the second polarization control optical path is... The third polarization operation module includes: a third polarization control optical path and a third phase modulator disposed in the transmission optical path of the third polarization control optical path. The third polarization control optical path is connected in series with the first polarization control optical path and the second polarization control optical path. The third polarization control optical path is used to input the optical pulse output from the combined beam of the second polarization control optical path from the input port, and split it into two sub-optical pulses, namely a fifth sub-optical pulse and a sixth sub-optical pulse. The third phase modulator is used to perform phase modulation on the fifth sub-optical pulse and / or the sixth sub-optical pulse, so that a phase difference γ is generated between the two sub-optical pulses. The fifth sub-optical pulse and the sixth sub-optical pulse after passing through the third phase modulator are combined and output through the third polarization control optical path. One of the two intrinsic polarization states of the third polarization control optical path is... The unequal-arm polarization control interferometer includes: a first optical coupling unit, a second optical coupling unit, a first transmission control optical path, and a second transmission control optical path; the first optical coupling unit includes at least three ports, one input port and two output ports; the second optical coupling unit includes at least three ports, two input ports and one output port; the two output ports of the first optical coupling unit are respectively connected to the two input ports of the second optical coupling unit through the first transmission control optical path and the second transmission control optical path, and the optical path lengths of the first transmission control optical path and the second transmission control optical path are not equal; The light pulse output from the third polarization control optical path is input into the unequal-arm polarization control interferometer through the input port of the first optical coupling unit. The first optical coupling unit further splits the input light pulse into two sub-light pulses, namely the seventh sub-light pulse and the eighth sub-light pulse. The seventh and eighth sub-light pulses are transmitted along the first and second transmission control optical paths, respectively, and then combined into a single light pulse by the second optical coupling unit of the unequal-arm polarization control interferometer. One of the two intrinsic polarization states of the unequal-arm polarization control interferometer is... Wherein, by setting the intrinsic polarization state x and the intrinsic polarization state The included angle between them, the intrinsic polarization state With the intrinsic polarization state The included angle between them, and the intrinsic polarization state x and the intrinsic polarization state The included angle between them, and in conjunction with the phase difference φ, phase difference And the phase difference γ to meet the requirements of different quantum communication protocols.

2. The apparatus according to claim 1, characterized in that, The first polarization control optical path, the second polarization control optical path, and / or the third polarization control optical path each include: a polarization beam splitting unit and a transmission optical path; The polarization beam splitter unit includes at least three ports, namely port A, port B and port C; the polarization beam splitter unit is used to polarize and split the light pulse input from port A into two sub-light pulses, which are output from port B and port C respectively; the intrinsic polarization state of the polarization beam splitter unit is the intrinsic polarization state of the first polarization control optical path, the second polarization control optical path and / or the third polarization control optical path; The transmission optical path is used to connect port B and port C of the polarization beam splitter unit.

3. The apparatus according to claim 2, characterized in that, The polarization beam splitter unit is a polarization beam splitter, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state of the polarization beam splitter unit.

4. The apparatus according to claim 2, characterized in that, The polarization beam splitter unit includes: a polarization beam splitter, a first polarizer, and a second polarizer; The polarization beam splitter unit also includes port D; The polarization beamsplitter includes four ports: a first port, a second port, a third port, and a fourth port. The first port of the polarization beamsplitter is port A of the polarization beamsplitter unit, and the fourth port of the polarization beamsplitter is port D of the polarization beamsplitter unit. The second and third ports of the polarization beamsplitter are connected to the ports on the first and second sides of the first and second polarizers, respectively. The port on the second side of the first polarizer is port B of the polarization beamsplitter unit, and the port on the second side of the second polarizer is port C of the polarization beamsplitter unit. The ports on the second side of the first and second polarizers are connected through the transmission optical path. The angle between the polarization direction of the first polarizer and one intrinsic polarization state of the polarization beamsplitter is θ, and the angle between the polarization direction of the second polarizer and another intrinsic polarization state of the polarization beamsplitter is δ. Wherein, θ and δ ≠ 90°, and n is an integer. The intrinsic polarization state of the polarization beamsplitter is the intrinsic polarization state of the polarization beamsplitter unit.

5. The apparatus according to claim 2, characterized in that, The polarization beam splitter unit includes: an optical beam splitter, a first polarizer, and a second polarizer; The optical beamsplitter includes at least three ports, designated as a first port, a second port, and a third port. The first port of the optical beamsplitter is port A of the polarization beamsplitter unit. The second and third ports of the optical beamsplitter are respectively connected to ports on the first side of the first polarizer and ports on the first side of the second polarizer. The port on the second side of the first polarizer is port B of the polarization beamsplitter unit, and the port on the second side of the second polarizer is port C of the polarization beamsplitter unit. The ports on the second side of the first polarizer and the ports on the second side of the second polarizer are connected through the transmission optical path. The polarization direction of the first polarizer is... The polarization direction of the second polarizer is The polarization direction of the first polarizer The deflection direction of the second deflector Mutually orthogonal; the deflection direction of the first deflector The deflection direction of the second deflector The intrinsic polarization state of the polarization beam splitter unit.

6. The apparatus according to claim 5, characterized in that, The optical beam splitter also includes a fourth port; The polarization beam splitter unit also includes port D; The fourth port of the optical beam splitter is port D of the polarization beam splitter unit.

7. The apparatus according to claim 2, characterized in that, The transmission optical path is a free-space optical path or a polarization-maintaining fiber.

8. The apparatus according to claim 7, characterized in that, Ports B and C of the polarization beam splitter are either coupled to the slow axis of the polarization-maintaining fiber or both are coupled to the fast axis of the polarization-maintaining fiber.

9. The apparatus according to claim 7, characterized in that, The device also includes a half-wave plate or a 90-degree Faraday rotator disposed in the transmission optical path.

10. The apparatus according to any one of claims 1 to 9, characterized in that, The first phase modulator includes a first port, a second port, and a third port. The first port and the second port are the forward input optical port and the reverse input optical port of the first phase modulator, respectively. The first sub-optical pulse is input to the first phase modulator through the first port and output from the second port after passing through the first phase modulator. The second sub-optical pulse is input to the first phase modulator through the second port and output from the first port after passing through the first phase modulator. The third port is an electrical port used to apply a modulated electrical signal. The second phase modulator includes a fourth port, a fifth port, and a sixth port. The fourth port and the fifth port are the forward input optical port and the reverse input optical port of the second phase modulator, respectively. The third sub-optical pulse is input to the second phase modulator through the fourth port and output from the fifth port after passing through the second phase modulator. The fourth sub-optical pulse is input to the second phase modulator through the fifth port and output from the fourth port after passing through the second phase modulator. The sixth port is an electrical port used to apply a modulated electrical signal. The third phase modulator includes a seventh port, an eighth port, and a ninth port. The seventh port and the eighth port are the forward input optical port and the reverse input optical port of the third phase modulator, respectively. The fifth sub-optical pulse is input to the third phase modulator through the seventh port and output from the eighth port after passing through the third phase modulator. The sixth sub-optical pulse is input to the third phase modulator through the eighth port and output from the seventh port after passing through the third phase modulator. The ninth port is an electrical port used to apply a modulation electrical signal.

11. The apparatus according to claim 10, characterized in that, After the first phase modulator applies a modulation electrical signal with a frequency higher than a specified threshold, the first phase modulator operates in a non-reciprocal state, and the ratio of the modulation efficiency of the first sub-optical pulse input from the forward input optical port to the modulation efficiency of the second sub-optical pulse input from the reverse input optical port is not less than a preset threshold. After the second phase modulator applies a modulation electrical signal with a frequency higher than a specified threshold, the second phase modulator operates in a non-reciprocal state, and the ratio of the modulation efficiency of the third sub-optical pulse input from the forward input optical port to the modulation efficiency of the fourth sub-optical pulse input from the reverse input optical port is not less than a preset threshold. After applying a modulation electrical signal with a frequency higher than a specified threshold, the third phase modulator operates in a non-reciprocal state, and the ratio of the modulation efficiency of the fifth sub-optical pulse input from the forward input optical port to the modulation efficiency of the sixth sub-optical pulse input from the reverse input optical port is not less than a preset threshold.

12. The apparatus according to claim 11, characterized in that, The first optical pulse and the second optical pulse pass through the first phase modulator simultaneously; The third and fourth sub-optical pulses simultaneously pass through the second phase modulator; and / or The fifth and sixth sub-light pulses pass through the third phase modulator simultaneously.

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

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

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

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

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

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

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

20. The apparatus according to claim 14 or 16, characterized in that, The first transmission control optical path or the second transmission control optical path is a 90° twisted polarization-maintaining fiber, or... The unequal-arm polarization control interferometer also includes a 90° polarization state rotator. The 90° polarization state rotator is disposed on the first transmission control optical path or the second transmission control optical path, and is used to rotate the polarization state of the passing sub-light pulse by 90°.

21. The apparatus according to any one of claims 13 to 19, characterized in that, The device further includes: a polarizer; The polarizer is located at the output port of the unequal-arm polarization control interferometer and is used to polarize the light pulses output by the unequal-arm polarization control interferometer.

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

23. The apparatus according to claim 1, characterized in that, Intrinsic polarization state of the first polarization control optical path Intrinsic polarization state of the second polarization control optical path When the included angle between them is 1·90°, the intrinsic polarization state of the first polarization control optical path and the intrinsic polarization state of the third polarization control optical path The included angle between them is 22.5°±m·45°, or 45°±m·90°, where l and m are integers; Intrinsic polarization state of the first polarization control optical path and intrinsic polarization state When the included angle between them is 22.5°±a·45° or 45°±a·90°, the intrinsic polarization state of the first polarization control optical path and the intrinsic polarization state of the third polarization control optical path The included angle between them is n·22.5°, where a and n are integers.

24. The apparatus according to claim 23, characterized in that, Intrinsic polarization state of the first polarization control optical path Intrinsic polarization state of the second polarization control optical path The included angle between them is achieved by rotating the second polarization control optical path, and the intrinsic polarization state of the first polarization control optical path is... and the intrinsic polarization state of the third polarization control optical path The included angle between them is achieved by rotating the third polarization control optical path; and / or, The device further includes: a first polarization state rotator and / or a second polarization state rotator. The first polarization state rotator is disposed between the first polarization control optical path and the second polarization control optical path, and the intrinsic polarization state of the first polarization control optical path is adjusted by the first polarization state rotator. Intrinsic polarization state of the second polarization control optical path The angle between them; The second polarization state rotator is disposed between the second polarization control optical path and the third polarization control optical path, and adjusts the intrinsic polarization state of the first polarization control optical path by means of the first polarization state rotator and / or the second polarization state rotator. and the intrinsic polarization state of the third polarization control optical path The angle between them.

25. The apparatus according to claim 1, characterized in that, The device further includes two optical isolation units, which are optical isolators or optical circulators. The two optical isolation units are respectively disposed between the first polarization operation module and the second polarization operation module, and between the second polarization operation module and the third polarization operation module.

26. The apparatus according to claim 1 or 23, characterized in that, Intrinsic polarization state of the first polarization control optical path The intrinsic polarization states of an unequal-arm polarization-controlled interferometer The angle between them is b·22.5°, where b is an integer.

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

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

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

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

31. A quantum communication system, characterized in that, Includes the time phase encoding device according to any one of claims 1 to 29.

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