Time-phase encoding apparatus and method, and quantum communication system

Abstract

The present disclosure provides a time-phase encoding apparatus and method, and a quantum communication system. The apparatus comprises a polarization encoding module and an unbalanced polarization control interferometer which are connected in series. The polarization encoding module comprises at least one input port and one output port, and the polarization encoding module is used for inputting an optical pulse through one input port, generating an optical pulse of a polarization encoded quantum state on the basis of the optical pulse, and outputting the optical pulse of the polarization encoded quantum state through the output port. The unbalanced polarization control interferometer comprises one input port and one output port, and the unbalanced polarization control interferometer is connected to the output port of the polarization encoding module by means of the input port, and is used for receiving the optical pulse of the polarization encoded quantum state input by the polarization encoding module, converting the polarization encoded quantum state into a time-phase encoded quantum state, and then outputting the time-phase encoded quantum state through the output port. The present disclosure achieves flexible generation of time-phase encoded quantum states in an X-basis / Z-basis, a Y-basis / Z-basis, an X-basis / Y-basis and the like.

Description

Time phase encoding device, method and quantum communication system TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of quantum communication and optical quantum encoding, and particularly relates to a time phase encoding device, method and 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. In an optical fiber quantum communication system, time phase encoding (including phase encoding) has advantages such as resistance to channel environment disturbance and efficient coding, and is valued by the industry. It has become the main encoding method for quantum communication.

[0004] How to compatibly support multiple quantum communication protocols in the same optical quantum encoding device and implement multiple time phase encoding quantum states is an important problem in the application of quantum communication.

[0005] SUMMARY

[0006] The present disclosure provides a time phase encoding device, method and quantum communication system to solve the technical problems mentioned in the prior art.

[0007] According to a first aspect of the present disclosure, a time phase encoding device comprises a polarization encoding module and an unequal arm polarization control interferometer connected in series, wherein,

[0008] The polarization encoding module comprises at least one input port and one output port. The polarization encoding module is configured to input an optical pulse through an input port, generate a polarization encoded quantum state optical pulse based on the optical pulse, and output the polarization encoded quantum state optical pulse through the output port. One of two eigenpolarization states of the polarization encoding module is

[0009] The unequal-arm polarization control interferometer comprises an input port and an output port, the unequal-arm polarization control interferometer is connected with the output port of the polarization encoding module through the input port, and is used for receiving the polarization-encoded quantum state light pulse output by the polarization encoding module, converting the polarization-encoded quantum state light pulse into a time-phase encoded quantum state, and outputting the time-phase encoded quantum state through the output port, one of two eigenpolarization states of the unequal-arm polarization control interferometer is

[0010] The angle between the eigenpolarization state and the eigenpolarization state is set to meet the encoding requirements of different quantum communication systems.

[0011] According to a second aspect of the present disclosure, a time-phase encoding method is provided, and the time-phase encoding method is implemented by using the time-phase encoding device.

[0012] According to a third aspect of the present disclosure, a quantum communication system is provided, and the quantum communication system comprises the time-phase encoding device.

[0013] In summary, the time-phase encoding device, the method and the quantum communication system provided by the present disclosure have at least the following beneficial effects:

[0014] The device provided by the present disclosure comprises a polarization encoding module and an unequal-arm polarization control interferometer connected in series, wherein the polarization encoding module comprises at least one input port and one output port, the polarization encoding module is used for inputting a light pulse through an input port, generating a polarization-encoded quantum state light pulse based on the light pulse, and outputting the polarization-encoded quantum state light pulse through the output port; the unequal-arm polarization control interferometer comprises an input port and an output port, the unequal-arm polarization control interferometer is connected with the output port of the polarization encoding module through the input port, and is used for receiving the polarization-encoded quantum state light pulse input by the polarization encoding module, converting the polarization-encoded quantum state light pulse into a time-phase encoded quantum state, and outputting the time-phase encoded quantum state through the output port. The polarization encoding module and the unequal-arm interferometer are connected in series in the present disclosure, the polarization encoding module generates a polarization-encoded quantum state, and then the unequal-arm polarization control interferometer converts the polarization-encoded quantum state into a time-phase encoded quantum state, so that the flexible generation of X base / Z base, Y base / Z base and X base / Y base time-phase encoded quantum states is realized. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without creative labor.

[0016] Figure 1 is a structural block diagram of a time phase encoding device according to an embodiment of the present disclosure;

[0017] Figure 2 is an architecture diagram of an embodiment of a time phase encoding device according to an embodiment of the present disclosure;

[0018] Figure 3 is a structural diagram of a first embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0019] Figure 4 is a structural diagram of a second embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0020] Figure 5 is a structural diagram of a third embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0021] Figure 6 is a structural diagram of a fourth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0022] Figure 7 is a structural diagram of a fifth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0023] Figure 8 is a structural diagram of a sixth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0024] Figure 9 is a structural diagram of a seventh embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0025] Figure 10 is a structural diagram of an eighth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0026] Figure 11 is a structural diagram of a ninth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0027] Figure 12 is a structural diagram of a tenth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0028] Figure 13 is a structural diagram of an eleventh embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0029] Figure 14 is a structural diagram of a twelfth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0030] Figure 15 is a structural diagram of a thirteenth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0031] Figure 16 is a structural diagram of a fourteenth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0032] Figure 17 is a structural diagram of a fifteenth embodiment of a polarization control optical path according to an embodiment of the present disclosure;

[0033] Figure 18 is a structural diagram of a first embodiment of an unequal arm polarization control interferometer according to an embodiment of the present disclosure;

[0034] FIG. 19 is a structural diagram of a second embodiment of the unequal-arm polarization control interferometer according to an embodiment of the present disclosure;

[0035] FIG. 20 is a structural diagram of a third embodiment of the unequal-arm polarization control interferometer according to an embodiment of the present disclosure;

[0036] FIG. 21 is a structural diagram of a fourth embodiment of the unequal-arm polarization control interferometer according to an embodiment of the present disclosure;

[0037] FIG. 22 is a structural diagram of a fifth embodiment of the unequal-arm polarization control interferometer according to an embodiment of the present disclosure;

[0038] FIG. 23 is a structural diagram of a sixth embodiment of the unequal-arm polarization control interferometer according to an embodiment of the present disclosure;

[0039] FIG. 24 is a structural diagram of a seventh embodiment of the unequal-arm polarization control interferometer according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0040] In order to make the above and other features and advantages of the present disclosure clearer, the present disclosure will be 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 and are only illustrative and not restrictive.

[0041] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent, however, to one skilled in the art that the specific details need not be employed to practice the present disclosure. In other instances, well-known steps or operations have not been described in detail in order to avoid obscuring the present disclosure.

[0042] It should be noted that the time-phase encoding described in the present disclosure includes phase encoding, i.e., the time-phase encoding is an encoding composed of any combination of quantum states of X phase base, Y phase base, and Z time base.

[0043] Referring to FIGS. 1 and 2, an embodiment of the present disclosure provides a time-phase encoding device. FIG. 1 is a structural block diagram of the time-phase encoding device, and FIG. 2 is an architectural diagram of one embodiment of the time-phase encoding device according to the present disclosure. The device includes a polarization encoding module 100 and an unequal-arm polarization control interferometer 200 connected in series.

[0044] In some embodiments, the polarization encoding module 100 includes at least one input port and one output port. The polarization encoding module 100 is configured to input a light pulse through the input port, generate a polarization-encoded quantum state of light pulse based on the light pulse, and output through the output port. One of two eigenpolarization states of the polarization encoding module 100 is In some embodiments, the polarization encoding module 100 includes at least one input port and one output port. The polarization encoding module 100 is configured to input a light pulse through the input port, generate a polarization-encoded quantum state of light pulse based on the light pulse, and output through the output port. One of two eigenpolarization states of the polarization encoding module 100 is

[0045] In an example embodiment, the polarization encoding module 100 comprises: at least one polarization control optical path and at least one phase modulator 205 arranged in the transmission optical path of the polarization control optical path; wherein the polarization control optical path is configured to split the input light pulse into two sub light pulses; the phase modulator 205 is configured to modulate the phase of at least one sub light pulse based on a modulation signal, so that a phase difference φ 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 encoded quantum state light pulse; wherein the eigenpolarization state of the polarization control optical path is the eigenpolarization state of the polarization encoding module 100.

[0046] As shown in FIG. 2, the polarization encoding module 100 comprises one polarization control optical path and one phase modulator, in this embodiment, the polarization control optical path comprises: a third optical coupling unit 201a, a fourth optical coupling unit 201b, a third transmission optical path 204a, and a fourth transmission optical path 204b; the third optical coupling unit 201a and the fourth optical coupling unit 201b are connected through the third transmission optical path 204a and the fourth transmission optical path 204b.

[0047] The third optical coupling unit 201a comprises at least three ports, namely a first port, a second port and a third port, as shown in port A, port B and port X in the figure, the first port of the third optical coupling unit 201a is an input port, and the second port and the third port of the third optical coupling unit 201a are output ports; the fourth optical coupling unit 201b comprises at least three ports, namely a fourth port, a fifth port and a sixth port, as shown in port C, port Y and port D in the figure, the fourth port and the fifth port are input ports of the fourth optical coupling unit 201b, and the sixth port is an output port of the fourth optical coupling unit 201b; the second port and the third port of the third optical coupling unit 201a are connected to the fourth port and the fifth port of the fourth optical coupling unit 201b through the third transmission optical path 204a and the fourth transmission optical path 204b respectively.

[0048] In an example embodiment, the third optical coupling unit 201a is configured to split the input light pulse into two sub light pulses, namely a first sub light pulse and a second sub light pulse, the first sub light pulse and the second sub light pulse are transmitted along the third transmission optical path 204a and the fourth transmission optical path 204b respectively and then combined by the fourth optical coupling unit 201b to output a light pulse; the two eigenpolarization states of the polarization control optical path are and

[0049] It should be noted that the first sub-light pulse and the second sub-light pulse are transmitted through the third transmission optical path 204a and the fourth transmission optical path 204b respectively and reach the fourth optical coupling unit 201b at the same time.

[0050] The polarization control optical path of the present disclosure can have various structures. FIG. 3 shows a structure diagram of a first embodiment of the polarization control optical path of the present disclosure. In this embodiment, the third optical coupling unit is a polarization beam splitter 201a, the fourth optical coupling unit is a polarization beam splitter 201b, and the third transmission optical path 204a and the fourth transmission optical path 204b are different transmission optical paths. The polarization beam splitter 201a includes three ports, namely port A, port B and port X, and the polarization beam splitter 201b includes three ports, namely port Y, port C and port D. Among them, the port B and the port X of the polarization beam splitter 201a are connected with the port C and the port Y of the polarization beam splitter 201b through the transmission optical paths 204a and 204b respectively. The light pulse input into the polarization beam splitter 201a is split into two sub-light pulses by the polarization beam splitter 201a, namely a first sub-light pulse and a second sub-light pulse, which are output from the port B and the port X of the polarization beam splitter 201a respectively. After the two sub-light pulses are input into the polarization beam splitter 201b through the port C and the port Y of the polarization beam splitter 201b, they are combined by the polarization beam splitter 201b and then output from the port D. The eigenpolarization state of the polarization beam splitter 201b is the eigenpolarization state of the polarization control optical path.

[0051] Referring to FIG. 4, a structure diagram of a second embodiment of the polarization control optical path of the present disclosure is shown. In this embodiment, the third optical coupling unit 201a and the fourth optical coupling unit 201b are the same polarization beam splitter 201, the third transmission optical path 204a and the fourth transmission optical path 204b are different transmission optical paths, and the eigenpolarization state of the polarization beam splitter 201 is the eigenpolarization state of the polarization control optical path. The polarization beam splitter 201 includes three ports, namely a first port, a second port and a third port, such as port A, port B and port C in the figure, and the port A is both an input port and an output port of the polarization control optical path. The polarization control optical path further includes two mirrors, namely a mirror 217 and a mirror 218, which are connected with the port B and the port C of the polarization beam splitter 201 through the third transmission optical path 204a and the fourth transmission optical path 204b respectively, and the mirror 217 and the mirror 218 are used to reflect the input sub-light pulse back to the polarization beam splitter 201.

[0052] Referring to FIG. 5, a third embodiment of the polarization control light path is shown. In this embodiment, the third optical coupling unit 201a and the fourth optical coupling unit 201b are the same polarization beam splitter 201, the third transmission light path 204a and the fourth transmission light path 204b are different transmission light paths, and the eigenpolarization state of the polarization beam splitter 201 is the eigenpolarization state of the polarization control light path. The polarization beam splitter 201 includes four ports, namely a first port, a second port, a third port, and a fourth port, as shown in the ports A, B, C, and D. The port A is the input port of the polarization control light path, and the port D is the output port of the polarization control light path. The polarization control light path further includes two mirrors, namely a mirror 217 and a mirror 218, which are connected to the ports B and C of the polarization beam splitter 201 through the third transmission light path 204a and the fourth transmission light path 204b, respectively. The two mirrors are used to reflect the input sub-pulse back to the polarization beam splitter 201. The two mirrors are 90° polarization state rotation mirrors, which can be quarter-wave plate mirrors or 90° Faraday rotation mirrors.

[0053] Referring to FIG. 6, a fourth embodiment of the polarization control light path is shown. In this embodiment, the third optical coupling unit 201a and the fourth optical coupling unit 201b are the same optical coupling unit, the third transmission light path 204a and the fourth transmission light path 204b are the same transmission light path 204, and the eigenpolarization state of the optical coupling unit is the eigenpolarization state of the polarization control light path. The optical coupling unit is a polarization beam splitter 201, which includes three ports, namely a first port, a second port, and a third port, as shown in the ports A, B, and C. The port A of the polarization beam splitter 201 is the input and output port of the polarization control light path, and the ports B and C of the polarization beam splitter 201 are connected through the transmission light path 204. In this embodiment, the eigenpolarization state of the polarization beam splitter 201 is the eigenpolarization state of the optical coupling unit.

[0054] Referring to FIG. 7, a fifth embodiment of the structure of the polarization control optical path is shown. In this embodiment, the third optical coupling unit 201a and the fourth optical coupling unit 201b are the same optical coupling unit, which includes four ports, port A, port B, port C and port D, the third transmission optical path 204a and the fourth transmission optical path 204b are the same transmission optical path 204, and the eigenpolarization state of the optical coupling unit is the eigenpolarization state of the polarization control optical path. The optical coupling unit includes a polarization beam splitter 201, a first polarizer 202 and a second polarizer 203. The polarization beam splitter 201 includes four ports, a first port, a second port, a third port and a fourth port. The first port of the polarization beam splitter 201 is the port A of the optical coupling unit, which is the input port of the polarization control optical path. The fourth port of the polarization beam splitter 201 is the port D of the optical coupling unit, and the first port or the fourth port of the polarization beam splitter 201 is the output port of the polarization control optical path. The second port and the third port of the polarization beam splitter 201 are connected to the ports on the first side of the first polarizer 202 and the second polarizer 203, respectively. The port on the second side of the first polarizer 202 is the port B of the optical coupling unit, and the port on the second side of the second polarizer 203 is the port C of the optical coupling 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 the transmission optical path 204. The angle between the polarization direction of the first polarizer 202 and one of the eigenpolarization states of the polarization beam splitter 201 is θ, and the angle between the polarization direction of the second polarizer 203 and the other eigenpolarization state of the polarization beam splitter 201 is δ. In this embodiment, θ and δ are not equal to n*90°, where n is an integer. In this embodiment, the eigenpolarization state of the polarization beam splitter 201 is the eigenpolarization state of the optical coupling unit.

[0055] Referring to FIG. 8, a sixth embodiment of the structure of the polarization control optical path is shown. In this embodiment, the third optical coupling unit 201a and the fourth optical coupling unit 201b are the same optical coupling unit, the optical coupling unit includes at least three ports, which are port A, port B and port C, the third transmission optical path 204a and the fourth transmission optical path 204b are the same transmission optical path 204, and the eigenpolarization state of the optical coupling unit is the eigenpolarization state of the polarization control optical path. The optical coupling 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, which are a first port, a second port and a third port. The first port of the optical beam splitter 201 is the port A of the optical coupling unit, which 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 201 are connected with the port of the first side of the first polarizer 202 and the port of the first side of the second polarizer 203, respectively. The port of the second side of the first polarizer 202 is the port B of the optical coupling unit, and the port of the second side of the second polarizer 203 is the port C of the optical coupling unit. The port of the second side of the first polarizer 202 and the port of the second side of the second polarizer 203 are connected by the transmission optical path 204. The polarization direction of the first polarizer 202 is The polarization direction of the second polarizer 203 is The polarization direction of the first polarizer 202 is orthogonal to the polarization direction of the second polarizer 203 The polarization direction of the first polarizer 202 is orthogonal to the polarization direction of the second polarizer 203 The polarization direction of the first polarizer 202 is

[0056] Referring to FIG. 9, a seventh embodiment of the structure of the polarization control optical path is shown. In this embodiment, the third optical coupling unit 201a and the fourth optical coupling unit 201b are the same optical coupling unit, the third transmission optical path 204a and the fourth transmission optical path 204b are the same transmission optical path 204, and the difference between this embodiment and the previous embodiment is that the optical coupling unit further includes a port D, and the eigenpolarization state of the optical coupling unit is the eigenpolarization state of the polarization control optical path. The difference between this embodiment and the embodiment shown in FIG. 7 is that the optical beam splitter 201 further includes a fourth port, which is the port D of the optical coupling unit, and the fourth port of the optical beam splitter 201 is the output port of the polarization control optical path.

[0057] It should be noted that, in the structure shown in FIGS. 6-9, the same transmission optical path is a free-space optical path or a polarization-maintaining optical fiber. Both ports of the same optical coupling unit connected to the same transmission optical path 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. It can be understood that, in the structure of the optical coupling unit containing a polarizer, the corresponding polarizer is coupled to the slow axis or the fast axis of the polarization-maintaining optical fiber. In an exemplary embodiment, the device further comprises a 90° polarization state rotator disposed in the transmission optical path (the same transmission optical path), and the 90° polarization state rotator can be a half-wave plate or a 90° Faraday rotator.

[0058] As shown in FIG. 10, it is a structure diagram of the eighth embodiment of the polarization control optical path, and the third optical coupling unit 201a and the fourth optical coupling unit 201b are both optical couplers. The polarization control optical path further comprises a 90° polarization state rotator disposed in the third transmission optical path 204a or the fourth transmission optical path 204b, and the 90° polarization state rotator can be a half-wave plate or a 90° Faraday rotator. In this embodiment, the polarization states of the two sub-light pulses input into the fourth optical coupling unit 201b are the eigenpolarization states of the polarization control optical path.

[0059] As shown in FIG. 11, it is a structure diagram of the ninth embodiment of the polarization control optical path, and the third optical coupling unit and the fourth optical coupling unit are the same optical coupler 201. The polarization control optical path further comprises two mirrors, i.e., a mirror 227 and a mirror 228; two output ports of the optical coupler 201 are a port B and a port X, and the port B and the port X are connected to the mirror 227 and the mirror 228 through the third transmission optical path 204a and the fourth transmission optical path 204b, respectively, and the mirror 227 and the mirror 228 are used to reflect the input sub-light pulses back to the optical coupler 201; one of the two mirrors is a 90° polarization state rotating mirror, and the 90° polarization state rotating mirror can be a quarter-wave plate mirror or a 90° Faraday rotating mirror; and the polarization states of the two sub-light pulses reflected back to the optical coupler 201 are the eigenpolarization states of the polarization control optical path.

[0060] As shown in FIG. 12, it is a structure diagram of the tenth embodiment of the polarization control optical path, the third optical coupling unit 201a and the fourth optical coupling unit 201b are optical couplers, and the polarization control optical path further comprises: a first pre-optical interferometer and a pre-optical coupling unit 222, wherein the first pre-optical interferometer comprises: the third optical coupling unit 201a, a fifth transmission optical path 224, and a pre-phase modulator 225 arranged on the fifth transmission optical path 224; the pre-optical coupling unit 222 is arranged in the third transmission optical path 204a or the fourth transmission optical path 204b, and the pre-optical coupling unit 222 comprises three ports, which are port R, port S and port T respectively, the port R is an input port of the time phase encoding device, the optical pulse input by the port R is output by the port S, and the optical pulse input by the port S is output by the port T; the port S and the port T of the pre-optical coupling unit 222 are connected with the third optical coupling unit 201a and the fourth optical coupling unit 201b respectively; the pre-optical coupling unit 222 is used as an input port of the time phase encoding device, and a light pulse input by the port R is input to the third optical coupling unit 201a by the port S; the third optical coupling unit 201a further comprises a seventh port Q, and the first port A and the seventh port Q of the third optical coupling unit 201a are connected by the fifth transmission optical path 224; the pre-phase modulator 225 is used for phase modulating one of the two input sub-optical pulses or different phase modulating the two sub-optical pulses based on a modulation signal; the first pre-optical interferometer is used for splitting the input optical pulse into two sub-optical pulses and making a phase difference between the two sub-optical pulses by the pre-phase modulator 225; the third optical coupling unit 201a is further used for receiving the two sub-optical pulses with the phase difference, reflecting and transmitting the two sub-optical pulses and inputting them into the third transmission optical path 204a and the fourth transmission optical path 204b by the second port B and the third port X respectively. The polarization state of the two sub-optical pulses input by the optical coupler 201b is the eigenpolarization state of the polarization control optical path. In this embodiment, the first pre-optical interferometer is arranged to realize the intensity adjustment of the sub-optical pulses input into the third transmission optical path 204a and the fourth transmission optical path 204b.

[0061] As shown in Figure 13, it is a structure diagram of the eleventh embodiment of the polarization control optical path, the third optical coupling unit 201a and the fourth optical coupling unit 201b are optical couplers, and the polarization control optical path further comprises: a second front light interferometer, the second front light interferometer comprises: a third optical coupling unit 201a, a front light coupling unit 221, a first front transmission optical path 224a, a second front transmission optical path 224b, and a front phase modulator 225 arranged in the first front transmission optical path 224a or the second front transmission optical path 224b, the third optical coupling unit 201a further comprises a seventh port Q; the front light coupling unit 221 comprises at least three ports, which are an eighth port P, a ninth port P' and a tenth port P" respectively, the eighth port P is the input port of the time phase encoding device, the ninth port P' and the tenth port P" are connected with the first port A and the seventh port Q of the third optical coupling unit 201a through the first front transmission optical path 224a and the second front transmission optical path 224b respectively; the first front light interferometer is used for inputting a light pulse through the eighth port P, and splitting the input light pulse into two sub light pulses which are input into the first front transmission optical path 224a and the second front transmission optical path 224b respectively, the front phase modulator 225 is used for phase modulating one of the two sub light pulses based on a modulation signal, so as to generate a phase difference between the two sub light pulses; the third optical coupling unit 201a is further used for receiving the two sub light pulses with the phase difference, reflecting and transmitting the two sub light pulses, and inputting them into the third transmission optical path 204a and the fourth transmission optical path 204b through the second port B and the third port X respectively. The polarization state of the two sub light pulses input into the optical coupler 201b is the eigenpolarization state of the polarization control optical path. In this embodiment, the intensity of the sub light pulses input into the third transmission optical path 204a and the fourth transmission optical path 204b is adjustable by arranging the second front light interferometer.

[0062] As shown in Figure 14, it is a structure diagram of the twelfth embodiment of the polarization control optical path, the third optical coupling unit 201a is a polarization beam splitter, and the fourth optical coupling unit 201b is an optical coupler; the eigenpolarization state of the polarization beam splitter 201a is the eigenpolarization state of the polarization control optical path.

[0063] As shown in Figure 15, it is a structure diagram of the thirteenth embodiment of the polarization control optical path, the third optical coupling unit 201a is an optical coupler, and the fourth optical coupling unit 201b is a polarization beam splitter; the eigenpolarization state of the polarization beam splitter 201b is the eigenpolarization state of the polarization control optical path.

[0064] In the embodiment, the second transmission optical path 204a or the third transmission optical path 204b is a 90° twisted polarization maintaining optical fiber, or the polarization control optical path further comprises: a 90° polarization state rotator arranged on the third transmission optical path 204a or the fourth transmission optical path 204b, used for rotating the polarization state of the passing sub-light pulse by 90°.

[0065] Referring to FIG. 16, it is a structure diagram of a fourteenth embodiment of the polarization control optical path. The third optical coupling unit 201a is an optical coupler, and the fourth optical coupling unit 201b is a polarization beam splitter. The eigenpolarization state of the polarization beam splitter 201b is the eigenpolarization state of the polarization control optical path. The polarization control optical path further comprises: a first pre-light interferometer and a pre-light coupling unit 222. The first pre-light interferometer comprises: the third optical coupling unit 201a, a fifth transmission optical path 224, and a pre-phase modulator 225 arranged on the fifth transmission optical path 224. The pre-light coupling unit 222 is arranged in the third transmission optical path 204a or the fourth transmission optical path 204b. The pre-light coupling unit 222 comprises three ports, namely a port R, a port S, and a port T. The port R is an input port of the time phase encoding device. The light pulse input by the port R is output by the port S, and the light pulse input by the port S is output by the port T. The port S and the port T of the pre-light coupling unit 222 are connected with the third optical coupling unit 201a and the fourth optical coupling unit 201b respectively. The pre-light coupling unit 222 is used as an input port of the time phase encoding device, and a light pulse input by the port R is input to the third optical coupling unit 201a by the port S. The third optical coupling unit 201a further comprises a seventh port Q. The first port A and the seventh port Q of the third optical coupling unit 201a are connected by the fifth transmission optical path 224. The pre-phase modulator 225 is used for phase modulating one of the two sub-light pulses input based on a modulation signal, or for different phase modulating the two sub-light pulses. The first pre-light interferometer is used for splitting the input light pulse into two sub-light pulses and making a phase difference between the two sub-light pulses by the pre-phase modulator 225. The third optical coupling unit 221a is also used for receiving the two sub-light pulses with a phase difference, reflecting and transmitting the two sub-light pulses, and inputting the two sub-light pulses into the third transmission optical path 204a and the fourth transmission optical path 204b by the second port B and the third port X respectively. In addition, the embodiments of the present disclosure are also applicable to the following cases: the third transmission optical path 204a or the fourth transmission optical path 204b is a 90° twisted polarization maintaining optical fiber, or the polarization control optical path further comprises: a 90° polarization state rotator arranged on the third transmission optical path 204a or the fourth transmission optical path 204b, used for rotating the polarization state of the passing sub-light pulse by 90°.

[0066] Referring to FIG. 17, a structure diagram of a fifteenth embodiment of a polarization control light path is shown. The third optical coupling unit 201a is an optical coupler, and the fourth optical coupling unit 201b is a polarization beam splitter. The eigenpolarization state of the polarization beam splitter 201b is the eigenpolarization state of the polarization control light path. The polarization control light path further includes a second front light interferometer, which includes a third optical coupling unit 201a, a front light coupling unit 221, a first front transmission light path 224a, a second front transmission light path 224b, and a front phase modulator 225 arranged in the first front transmission light path 224a or the second front transmission light path 224b. The third optical coupling unit 201a further includes a seventh port Q. The front light coupling unit 221 includes at least three ports, which are an eighth port P, a ninth port P', and a tenth port P". The eighth port P is an input port of the time phase encoding device. The ninth port P' and the tenth port P" are connected to the first port A and the seventh port Q of the third optical coupling unit 201a through the first front transmission light path 224a and the second front transmission light path 224b, respectively. The first front light interferometer is configured to input a light pulse through the eighth port P, split the input light pulse into two sub-light pulses, and input the two sub-light pulses into the first front transmission light path 224a and the second front transmission light path 224b, respectively. The front phase modulator 225 is configured to modulate the phase of one of the two sub-light pulses based on a modulation signal, so as to generate a phase difference between the two sub-light pulses. The third optical coupling unit 201a is further configured to receive the two sub-light pulses with the phase difference, reflect and transmit the two sub-light pulses, and input the two sub-light pulses into the third transmission light path 204a and the fourth transmission light path 204b through the second port B and the third port X, respectively. In addition, the embodiments of the present disclosure are also applicable to the following cases: the third transmission light path 204a or the fourth transmission light path 204b is a 90° twisted polarization maintaining optical fiber, or the polarization control light path further includes a 90° polarization state rotator arranged on the third transmission light path 204a or the fourth transmission light path 204b, which is configured to rotate the polarization state of the passing sub-light pulse by 90°.

[0067] It should be noted that the polarization encoding module can include at least one phase modulator 205, which can be arranged in the third transmission light path 204a or the fourth transmission light path 204b, or can be arranged in different transmission light paths of the third transmission light path 204a and the fourth transmission light path 204b respectively; the phase modulator 205 includes a first port E and a second port F, which are a forward input light port and a reverse input light port respectively; the transmission light path connected with the phase modulator 205 is coupled with the slow axis of the first port E and the second port F of the phase modulator 205, or is coupled with the fast axis of the first port E and the second port F of the phase modulator 205; the phase modulator 205 is used for phase modulating the input sub-light pulse, so as to generate a phase difference φ between the two sub-light pulses. The at least one phase modulator can be a single polarization phase modulator or a birefringent phase modulator.

[0068] In an exemplary embodiment, the 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 a forward input light port and a reverse input light port of the phase modulator 205 respectively, a first sub-light pulse is input into the phase modulator 205 through the first port E and is output from the second port F after passing through the phase modulator 205, a second sub-light pulse is input into the phase modulator 205 through the second port F and is output from the first port E after passing through the phase modulator 205, and the third port is an electrical port used for connecting with a driver and receiving a modulation signal applied by the driver.

[0069] In an exemplary embodiment, referring to the structure of the polarization control light path shown in FIGS. 6-9, the phase modulator 205 is arranged in the transmission light path 204, and the first sub-light pulse and the second sub-light pulse can pass through the phase modulator 205 at the same time. After a high-frequency modulation signal is applied to the phase modulator 205, the phase modulator 205 works in a non-reciprocal state, and the ratio of the modulation efficiency of the first sub-light pulse input from the forward input light port to the modulation efficiency of the second sub-light pulse input from the reverse input light port is not less than a preset threshold value.

[0070] In the structure of the polarization control light path of any one of the embodiments shown in FIGS. 6-9, the polarization encoding module can include a plurality of phase modulators, the plurality of phase modulators are connected in series in the transmission light path 204, and the plurality of phase modulators cooperatively phase modulate the input sub-light pulse, so as to generate a phase difference φ between the two sub-light pulses. The plurality of phase modulators connected in series can realize the generation of different polarization encoding quantum states through digital modulation.

[0071] In the corresponding structures of FIG. 6-9, the two sub-pulses of polarization beam splitting in the polarization control optical path have the same transmission path when combined, which has self-compensation function to environmental interference. In addition, in the corresponding structures, the phase modulator in the polarization control optical path 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 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; therefore, 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 at the same time, 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, and realizing time phase quantum state encoding at a speed of 10GHz or more. The high frequency modulation signal is, for example, a modulation signal with a frequency not less than 10GHz. When the phase modulator is applied with a high frequency modulation signal with a frequency higher than a specified threshold, there can be multiple sub-pulses input by the forward input optical port and multiple sub-pulses input by the reverse input optical port at the same time.

[0072] In the above embodiments, the polarizer and the beam splitter or the polarization beam splitter can be bonded.

[0073] In an exemplary embodiment, the device further comprises a half-wave plate or a 90-degree Faraday rotator disposed in the transmission optical path 204.

[0074] Referring again to FIG. 2, the figure shows a schematic diagram of an unequal arm polarization control interferometer 200, which includes a first optical coupling unit 206, a second optical coupling unit 209, a first transmission optical path 207 and a second transmission optical path 208. The first optical coupling unit 206 includes at least three ports, one input port G and two output ports (i.e., port H and port I). The second optical coupling unit 209 includes at least three ports, two input ports (i.e., port M and port N) and one output port L. The two output ports of the first optical coupling unit 206 are connected to the two output ports of the second optical coupling unit 209 through the first transmission optical path 207 and the second transmission optical path 208, respectively. The optical paths of the first transmission optical path 207 and the second transmission optical path 208 are not equal, so that the two sub-pulses transmitted through the first transmission optical path 207 and the second transmission optical path 208 have a time delay when combined. The input port G of the first optical coupling unit 206 is the input port of the unequal arm polarization control interferometer 200, and the output port L of the second optical coupling unit 209 is the output port of the unequal arm polarization control interferometer 200, which is also the output port of the time phase encoding device.

[0075] In an exemplary embodiment, the first transmission optical path 207 and the second transmission optical path 208 are polarization maintaining optical fibers or free space.

[0076] In an exemplary embodiment, the unequal-arm polarization control interferometer further comprises a polarizer, which is arranged at the output port of the unequal-arm polarization control interferometer and used to polarize the output light pulse.

[0077] In an exemplary embodiment, the combined light pulse output by the polarization encoding module 100 is input into the unequal-arm polarization control interferometer 200 through the input port G of the first optical coupling unit 206 of the unequal-arm polarization control interferometer 200, and the input light pulse is split into two sub light pulses by the first optical coupling unit 206, which are the third sub light pulse and the fourth sub light pulse respectively. The third sub light pulse and the fourth sub light pulse are transmitted along the first transmission optical path 207 and the second transmission optical path 208 respectively, and then combined into one light pulse output by the second optical coupling unit 209 of the unequal-arm polarization control interferometer 200. The optical paths of the first transmission optical path 207 and the second transmission optical path 208 are not equal, so that the two sub light pulses transmitted through the first transmission optical path 207 and the second transmission optical path 208 produce time delay when combined and output by the second optical coupling unit 209. The two eigenpolarizations of the unequal-arm polarization control interferometer 200 are and

[0078] As shown in FIG. 18, it is a structure diagram of the first embodiment of the unequal-arm polarization control interferometer 200. In this embodiment, the first optical coupling unit 206 and the second optical coupling unit 209 are the same device, the first transmission optical path 207 and the second transmission optical path 208 are different transmission optical paths, and the unequal-arm polarization control interferometer 200 further comprises two mirrors (mirror 211 and mirror 212), the two output ports of the first optical coupling unit 206 are connected with one end of the first transmission optical path 207 and one end of the second transmission optical path 208 respectively, and the two mirrors are connected with the other end of the first transmission optical path 207 and the other end of the second transmission optical path 208 respectively, which are used to reflect the light pulse input into the two mirrors back to the first optical coupling unit 206. In this embodiment, the port G of the first optical coupling unit 206 serves as the input port and the output port of the unequal-arm polarization control interferometer 200. In this embodiment, the same device is a polarization beam splitter, and the eigenpolarization of the polarization beam splitter is the direction of the eigenpolarization of the unequal-arm polarization control interferometer.

[0079] In some embodiments, as shown in FIG. 19, a second embodiment structure diagram of the unequal-arm polarization control interferometer 200, the difference between the second embodiment and the structure shown in FIG. 18 is that the polarization beam splitter 206 further comprises a port G', which is an output port of the unequal-arm polarization control interferometer 200. In this embodiment, the port G is an input port of the unequal-arm polarization control interferometer 200. The mirrors 211 and 212 are polarization state rotation mirrors, which rotate the polarization state of the reflected light pulse by an angle relative to the polarization state of the input light, for example, the polarization state rotation mirrors can be quarter-wave plate mirrors or 90° Faraday rotation mirrors, or the unequal-arm polarization control interferometer 200 further comprises two polarizers (not shown in the figure), which are respectively arranged on the first transmission light path and the second transmission light path, and the polarization directions of the two polarizers are not orthogonal to the corresponding eigenpolarization states of the polarization beam splitter through which the light is transmitted, that is, the polarization direction of each polarizer is not orthogonal to the eigenpolarization state of the polarization beam splitter corresponding to the polarization processing.

[0080] As shown in FIG. 20, a third embodiment structure diagram of the unequal-arm polarization control interferometer 200, in this embodiment, the first optical coupling unit is the optical coupler 206, and the second optical coupling unit is the polarization beam combiner 209, and the eigenpolarization state of the polarization beam combiner 209 is the eigenpolarization state of the unequal-arm polarization control interferometer 200. The optical coupler 206 and the polarization beam combiner 209 are connected through the first transmission light path 207 and the second transmission light path 208 with unequal optical paths, respectively.

[0081] As shown in FIG. 21, a fourth embodiment structure diagram of the unequal-arm polarization control interferometer 200, in this embodiment, the first optical coupling unit is the polarization beam splitter 206, and the second optical coupling unit is the polarization beam combiner 209, and the eigenpolarization state of the polarization beam splitter 206 is the eigenpolarization state of the unequal-arm polarization control interferometer 200. The polarization beam splitter 206 and the polarization beam combiner 209 are connected through the first transmission light path 207 and the second transmission light path 208 with unequal optical paths, respectively.

[0082] As shown in Figure 22, it is a schematic diagram of the fifth embodiment of the unequal-arm polarization control interferometer 200, in which the first optical coupling unit is a polarization beam splitter 206, and the second optical coupling unit is an optical coupler 209, and the eigenpolarization state of the polarization beam splitter 206 is the eigenpolarization state of the unequal-arm polarization control interferometer 200. The polarization beam splitter 206 and the optical coupler 209 are connected through the first transmission optical path 207 and the second transmission optical path 208 with unequal optical path lengths, respectively. Optionally, the first transmission optical path 207 or the second transmission optical path 208 is a 90° twisted polarization maintaining fiber, or the unequal-arm polarization control interferometer 200 further comprises a 90° polarization state rotator, which is arranged on the first transmission optical path 207 or the second transmission optical path 208, and is used to rotate the polarization state of the sub-light pulse passing through by 90°. The 90° polarization state rotator can be a half-wave plate or a 90° Faraday rotator.

[0083] As shown in Figure 23, it is a schematic diagram of the sixth embodiment of the unequal-arm polarization control interferometer 200, in which the first optical coupling unit is an optical coupler 206, and the second optical coupling unit is an optical coupler 209. The unequal-arm polarization control interferometer 200 further comprises two polarizers, which are a polarizer 2203 and a polarizer 2204, respectively. The two polarizers 2203 and 2204 are arranged on the first transmission optical path 207 and the second transmission optical path 208, respectively. In which, one output port of the optical coupler 206 is connected with the first side port of the polarizer 2203, and the polarizer 2203 is used to polarize one of the sub-light pulses output by the optical coupler 206. Another output port of the optical coupler 206 is connected with the first side port of the polarizer 2204, and the polarizer 2204 is used to polarize another of the sub-light pulses output by the optical coupler 206, and the polarization directions of the two polarizers 2203 and 2204 are orthogonal to each other. The other side port of the polarizer 2203 and the other side port of the polarizer 2204 are connected with the optical coupler 209 through the first transmission optical path 207 and the second transmission optical path 208, 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 first transmission optical path 207 and the second transmission optical path 208 are 90° twisted polarization maintaining fibers, or the unequal-arm polarization control interferometer 200 further comprises a 90° polarization state rotator, which is arranged on the first transmission optical path 207 or the second transmission optical path 208, and is used to rotate the polarization state of the sub-light pulse passing through by 90°. The 90° polarization state rotator can be a half-wave plate or a 90° Faraday rotator.

[0084] As shown in FIG. 24, it is a schematic structural diagram of a seventh embodiment of the unequal-arm polarization control interferometer 200. In this embodiment, the first light coupling unit and the second light coupling unit are the same light coupler 206. The unequal-arm polarization control interferometer 200 further comprises: a first transmission light path 207, a second transmission light path 208, two mirrors 2402 and 2403, and two polarizers 2404 and 2405.

[0085] The two output ports of the light coupler 206 are connected with one end of the first transmission light path 207 and one end of the second transmission light path 208 respectively. The two mirrors 2402 and 2403 are connected with the other end of the first transmission light path 207 and the other end of the second transmission light path 208 respectively. The two polarizers 2404 and 2405 are arranged on the first transmission light path and the second transmission light path respectively. The polarization directions of the two polarizers 2404 and 2405 are orthogonal to each other. The polarization directions of the two polarizers 2404 and 2405 are the eigenpolarization state directions of the unequal-arm polarization control interferometer.

[0086] It should be noted that the above-mentioned same light coupler 206 can contain four ports or three ports. In FIG. 24, only the case of containing four ports is shown.

[0087] It should be noted that the structures of the polarization encoding module 100 and the unequal-arm polarization control interferometer 200 in FIGS. 2-24 are only structural examples. The structures of the polarization encoding module 100 and the unequal-arm polarization control interferometer 200 in the present disclosure are not limited to the structures in FIGS. 2-24. As long as the structures of the polarization encoding module 100 and the unequal-arm polarization control interferometer 200 can be realized, all types of structures can be adopted.

[0088] In an exemplary embodiment, the polarization state of the light pulse input into the polarization encoding module is Or, the polarization state of the light pulse input into the polarization encoding module is Wherein, n is an integer, And are the two eigenpolarization states of the first polarization encoding module, and β is an arbitrary value between 0 and 2π.

[0089] In an exemplary embodiment, the polarization state of the light pulse input into the polarization encoding module is 45° linear polarization, -45° linear polarization, left-handed circular polarization or right-handed circular polarization.

[0090] When the polarization state of the optical pulse input into the time-phase encoding and decoding device is 45° linear polarization, the phase modulator 205 randomly modulates four phases of 0°, 90°, 180° or 270°, so that the polarization control optical path randomly outputs left / right circular polarization states and ±45° linear polarization states. Further, the polarization control optical path randomly outputs left / right circular polarization states and ±45° linear polarization states, wherein the ±45° linear polarization states generate Z basis time states via the unequal-arm polarization control interferometer 200, and the left / right circular polarization states generate Y basis phase states via the unequal-arm polarization control interferometer 200, thereby generating time-phase encoding quantum states.

[0091] 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 200 is set to satisfy the requirements of different quantum communication protocols. 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 200 is set to satisfy the requirements of different quantum communication protocols. 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 200 is set to satisfy the requirements of different quantum communication protocols. 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 200 is set to satisfy the requirements of different quantum communication protocols. 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 200 is set to satisfy the requirements of different quantum communication protocols.

[0092] 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 200 is set to satisfy the requirements of different quantum communication protocols. 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 200 is set to satisfy the requirements of different quantum communication protocols. 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 200 is set to satisfy the requirements of different quantum communication protocols.

[0093] For example, when the polarization state of the optical pulse input into the time-phase encoding and decoding device is 45° linear polarization, the phase modulator 205 randomly modulates four phases of 0°, 90°, 180° or 270°, so that the polarization control optical path randomly outputs left / right circular polarization states and ±45° linear polarization states. The angle between the eigenpolarization state of the polarization control optical path and the eigenpolarization state of the unequal-arm polarization control interferometer 200 is set to 45°, and further, the polarization control optical path randomly outputs left / right circular polarization states and ±45° linear polarization states, wherein the ±45° linear polarization states generate Z basis time states via the unequal-arm polarization control interferometer 200, and the left / right circular polarization states generate Y basis phase states via the unequal-arm polarization control interferometer 200, thereby generating time-phase encoding quantum states. 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 200 is set to satisfy the requirements of different quantum communication protocols. 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 200 is set to satisfy the requirements of different quantum communication protocols.

[0094] In an exemplary embodiment, the apparatus further comprises: a quarter wave plate disposed between the polarization control optical path and the unequal arm polarization control interferometer 200. In some embodiments, one of the eigenpolarization states of the quarter wave plate can be at an angle of 45° ± m·90° or m·90°, m being an integer, with the eigenpolarization states of the unequal arm polarization control interferometer 200.

[0095] In embodiments where a quarter wave plate is disposed, by configuring the angle between the eigenpolarization states of the polarization control optical path and the eigenpolarization states of the unequal arm polarization control interferometer 200, the angle between the eigenpolarization states of the quarter wave plate and the eigenpolarization states of the unequal arm polarization control interferometer , a time phase encoding quantum state can be flexibly generated. For example, by configuring the angle between the eigenpolarization states of the polarization control optical path and the eigenpolarization states of the unequal arm polarization control interferometer 200 to be 0°, the angle between the eigenpolarization states of the quarter wave plate and the eigenpolarization states of the unequal arm polarization control interferometer to be 0°, an X / Y phase encoding quantum state can be prepared; by configuring the angle between the eigenpolarization states of the polarization control optical path and the eigenpolarization states of the unequal arm polarization control interferometer 200 to be 0°, the angle between the eigenpolarization states of the quarter wave plate and the eigenpolarization states of the unequal arm polarization control interferometer to be 45°, a Z / X time phase encoding quantum state can be prepared; by configuring the angle between the eigenpolarization states of the polarization control optical path and the eigenpolarization states of the unequal arm polarization control interferometer 200 to be 45°, the angle between the eigenpolarization states of the quarter wave plate and the eigenpolarization states of the unequal arm polarization control interferometer to be 45°, a Z / Y time phase encoding quantum state can be prepared. In some embodiments, the phase difference φ is set according to the requirements of the quantum communication protocol, which includes: 0°, 90°, 180° or 270°. In some embodiments, the phase difference φ is set according to the requirements of the quantum communication protocol, which includes: 0°, 90°, 180° or 270°.

[0096] In some embodiments, the phase difference φ is set according to the requirements of the quantum communication protocol, which includes: 0°, 90°, 180° or 270°.

[0097] ​​​In some embodiments, when multiple phase modulators 205 are arranged in the polarization control optical path, the modulation phase of the two sub-optical pulses by the multiple phase modulators can be determined according to the polarization encoding requirements of the quantum communication system. That is, regardless of whether it is in individual modulation mode or combined modulation mode, the phase difference between the two sub-optical pulses modulated by the phase modulator 205 meets the modulation phase requirements in the quantum communication protocol. In this way, high-precision implementation of the quantum communication protocol can be guaranteed, and the flexibility and adaptability of the device can be improved by setting multiple phase modulators to reduce the number of states of the modulation phase of a single phase modulator.

[0098] In combined modulation mode, a single phase modulator can modulate fewer types of phases than the required phases in a quantum communication protocol.

[0099] In some embodiments, the time-phase polarization encoding device of this disclosure can also be used to implement the time-phase polarization decoding process, depending on the requirements of quantum communication.

[0100] According to this disclosure, a time-phase polarization encoding method is provided, which uses the aforementioned time-phase encoding device to implement time-phase encoding.

[0101] This disclosure provides a quantum communication system including the aforementioned time-phase encoding device. The quantum communication system can be a discrete-variable quantum communication system or a continuous-variable quantum communication system.

[0102] It should be understood that the specific features, operation and details described herein with respect to the apparatus of this disclosure can also be similarly applied to the methods and systems of this disclosure, or vice versa.

[0103] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A time phase encoding apparatus, wherein, The application relates to a polarization encoding module and a polarization control interferometer. The included angle between the polarization encoding module and the polarization control interferometer satisfies the encoding requirements of different quantum communication systems. The polarization encoding module comprises at least one input port and one output port, the polarization encoding module is used for inputting optical pulses through an input port, generating polarization encoded quantum state optical pulses based on the optical pulses, and outputting through the output port; one of two eigenpolarization states of the polarization encoding module is The unequal-arm polarization control interferometer comprises an input port and an output port, the unequal-arm polarization control interferometer is connected with the output port of the polarization encoding module through the input port, and is used for receiving the polarization encoded quantum state light pulse output by the polarization encoding module, converting the polarization encoded quantum state into a time phase encoded quantum state, and outputting through the output port. One of the two eigenpolarization states of the unequal-arm polarization control interferometer is wherein the intrinsic polarization state is set by setting the polarization state of the light source with the intrinsic polarization state The polarization encoding 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.

2. The apparatus of claim 1, wherein, The polarization control optical path is used for splitting one light pulse into two sub-light pulses. The phase modulator is used for phase modulation of at least one sub-light pulse based on a modulation signal, so that a phase difference phi is generated between the two sub-light pulses. The polarization control optical path is also used for combining the two sub-light pulses with the phase difference and outputting a generated polarization encoding quantum state light pulse. The eigenpolarization state of the polarization control optical path is the eigenpolarization state of the polarization encoding module. The polarization control optical path comprises a third optical coupling unit, a fourth optical coupling unit, a third transmission optical path and a fourth transmission optical path.

3. The apparatus of claim 2, wherein, The third optical coupling unit comprises three ports, namely a first port, a second port and a third port. The fourth optical coupling unit comprises three ports, namely a fourth port, a fifth port and a sixth port. The second port and the third port of the third optical coupling unit are connected to the fourth port and the fifth port of the fourth optical coupling unit through the third transmission optical path and the fourth transmission optical path. The third optical coupling unit and the fourth optical coupling unit are optical couplers.

4. The apparatus of claim 3, wherein, The polarization control optical path further comprises a 90-degree polarization state rotator arranged in the third transmission optical path or the fourth transmission optical path. The polarization state of the two sub-light pulses input into the fourth optical coupling unit is the eigenpolarization state of the polarization control optical path.

5. The apparatus of claim 3, wherein, The third optical coupling unit and the fourth optical coupling unit are the same optical coupler. The polarization control optical path further comprises two mirrors. The two output ports of the optical coupler are connected to the two mirrors through the third transmission optical path and the fourth transmission optical path. One of the two mirrors is a quarter-wave plate mirror or a 90-degree Faraday rotating mirror.

6. The apparatus of claim 3, wherein, The polarization state of the two sub-light pulses reflected back to the optical coupler is the eigenpolarization state of the polarization control optical path. The third optical coupling unit and the fourth optical coupling unit are the same polarization beam splitter. The polarization control optical path further comprises two mirrors. The two output ports of the polarization beam splitter are connected to the two mirrors through the third transmission optical path and the fourth transmission optical path. The eigenpolarization state of the polarization beam splitter is the eigenpolarization state of the polarization control optical path.

7. The apparatus of claim 3, wherein, The third optical coupling unit is a polarization beam splitter, and the fourth optical coupling unit is an optical coupler. An intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the polarization control optical path.

8. The apparatus of claim 3, wherein, The third optical coupling unit is an optical coupler, and the fourth optical coupling unit is a polarization beam splitter. An intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the polarization control optical path.

9. The apparatus of claim 8, wherein, The third transmission optical path or the fourth transmission optical path is a 90° twisted polarization maintaining optical fiber, or, The polarization control optical path further comprises a 90° polarization state rotator arranged on the third transmission optical path or the fourth transmission optical path, for rotating a polarization state of a passing sub-light pulse by 90°.

10. The apparatus of claim 4, 8, or 9, wherein, The polarization control optical path further comprises a first pre-light interferometer and a pre-light coupling unit, wherein the first pre-light interferometer comprises a third optical coupling unit, a fifth transmission optical path, and a pre-phase modulator arranged on the fifth transmission optical path. The pre-light coupling unit is arranged in the third transmission optical path or the fourth transmission optical path, and the pre-light coupling unit comprises three ports, namely a port R, a port S, and a port T. The port R is an input port of the time-phase encoding device. Light pulses input through the port R are output through the port S, and light pulses input through the port S are output through the port T. The port S and the port T of the pre-light coupling unit are connected to the third optical coupling unit and the fourth optical coupling unit, respectively. The pre-light coupling unit is used as an input port of the time-phase encoding device, and a light pulse input through the port R is input to the third optical coupling unit through the port S. The third optical coupling unit further comprises a seventh port, and the first port and the seventh port of the third optical coupling unit are connected through the fifth transmission optical path. The pre-phase modulator is used to modulate the phase of one of the two sub-light pulses input based on a modulation signal, or to modulate the phases of the two sub-light pulses differently. The first pre-light interferometer is used to split the input light pulse into two sub-light pulses and generate a phase difference between the two sub-light pulses through the pre-phase modulator. The third optical coupling unit is further used to receive the two sub-light pulses with a phase difference, reflect and transmit the two sub-light pulses, and input the two sub-light pulses into the third transmission optical path and the fourth transmission optical path through the second port and the third port, respectively.

11. The apparatus of claim 4, 8, or 9, wherein, The polarization control optical path further comprises a second pre-light interferometer, and the second pre-light interferometer comprises a third optical coupling unit, a pre-light coupling unit, a first pre-transmission optical path, a second pre-transmission optical path, and a pre-phase modulator arranged in the first pre-transmission optical path or the second pre-transmission optical path. The third optical coupling unit further comprises a seventh port. The pre-light coupling unit comprises at least three ports, namely an eighth port, a ninth port, and a tenth port. The eighth port is an input port of the time-phase encoding device, and the ninth port and the tenth port are connected to the first port and the seventh port of the third optical coupling unit through the first pre-transmission optical path and the second pre-transmission optical path, respectively. The first pre-optical interferometer is configured to input one light pulse through the eighth port, and split the input light pulse into two sub-light pulses which are input into the first pre-transmission optical path and the second pre-transmission optical path respectively, and the pre-phase modulator is configured to perform phase modulation on one sub-light pulse based on a modulation signal, so as to generate a phase difference between the two sub-light pulses. The third optical coupling unit is further configured to receive the two sub-light pulses with the phase difference, reflect and transmit the two sub-light pulses to generate two sub-light pulses, and input the two sub-light pulses into the third transmission optical path and the fourth transmission optical path through the second port and the third port respectively.

12. The apparatus of claim 3, wherein, The third optical coupling unit and the fourth optical coupling unit are polarization beam splitters, and an eigenpolarization state of the polarization beam splitters is an eigenpolarization state of the polarization control optical path.

13. The apparatus of claim 3, wherein, The third optical coupling unit and the fourth optical coupling unit are the same optical coupling unit, the third transmission optical path and the fourth transmission optical path are the same transmission optical path, and an eigenpolarization state of the optical coupling unit is an eigenpolarization state of the polarization control optical path.

14. The apparatus of claim 13, wherein, The same optical coupling unit is a polarization beam splitter, the polarization beam splitter includes at least 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 transmission optical path, and an eigenpolarization state of the polarization beam splitter is an eigenpolarization state of the optical coupling unit.

15. The apparatus of claim 13, wherein, The 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, 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 the transmission optical path, an angle between a polarization direction of the first polarizer and an eigenpolarization state of the polarization beam splitter is θ, an angle between a polarization direction of the second polarizer and another eigenpolarization state of the polarization beam splitter is δ, θ and δ are not equal to n*90°, n is an integer, and an eigenpolarization state of the polarization beam splitter is an eigenpolarization state of the optical coupling unit.

16. The apparatus of claim 13, wherein, The optical coupling unit includes an optical beam splitter, a first polarizer and a second polarizer. The optical splitter comprises at least three ports, respectively a first port, a second port and a third 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 the transmission optical path, the polarization direction of the first polarizer is a polarization direction of the second polarizer is a polarization direction of the first polarizer a polarization direction of the second polarizer mutually orthogonal; the polarizing direction of the first polarizer The polarization direction of the second polarizer is perpendicular to the polarization direction of the first polarizer. deviation direction The eigenpolarization state of the optical coupling unit is the polarization direction of the second polarizer.

17. The apparatus of claim 16, wherein, The optical beam splitter further includes a fourth port. The fourth port of the optical beam splitter is an output port of the polarization control optical path.

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

19. The apparatus of claim 18, wherein, The second port and the third port of the same optical coupling unit are both coupled to the slow axis of the polarization maintaining optical fiber or both coupled to the fast axis of the polarization maintaining optical fiber.

20. The apparatus of any one of claims 13 to 17, wherein, The apparatus further comprises a half-wave plate or a 90° Faraday rotator arranged in the transmission optical path.

21. The apparatus of any one of claims 13 to 17, wherein, The phase modulator comprises a first port and a second port, which are a forward input light port and a backward input light port respectively, and transmission optical paths connected to the phase modulator are both coupled to the slow axis of the first port and the second port of the phase modulator or both coupled to the fast axis of the first port and the second port of the phase modulator.

22. The apparatus of claim 21, wherein, After being applied with a modulation signal with a frequency higher than a specified threshold, the phase modulator works in a non-reciprocal state, and a ratio of a modulation efficiency on sub-light pulses input by the forward input light port to a modulation efficiency on sub-light pulses input by the backward input light port is not less than a preset threshold. The unequal-arm polarization control interferometer comprises a first optical coupling unit, a second optical coupling unit, a first transmission optical path and a second transmission optical path.

23. The apparatus of claim 1, wherein, 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 to the two input ports of the second optical coupling unit through the first transmission optical path and the second transmission optical path respectively, the optical paths of the first transmission optical path and the second transmission optical path are not equal, the input port of the first optical coupling unit is an input port of the unequal-arm polarization control interferometer, and the output port of the second optical coupling unit is an output port of the unequal-arm polarization control interferometer. The second optical coupling unit is a polarization beam combiner.

24. The apparatus of claim 23, wherein, The first optical coupling unit is an optical coupler, and an intrinsic polarization state of the polarization beam combiner is an intrinsic polarization state of the unequal-arm polarization control interferometer; or, The first optical coupling unit is a polarization beam splitter, and an intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the unequal-arm polarization control interferometer. The second optical coupling unit is an optical coupler.

25. The apparatus of claim 23, wherein, The first optical coupling unit is a polarization beam splitter, and an intrinsic polarization state of the polarization beam splitter is an intrinsic polarization state of the unequal-arm polarization control interferometer. Or, The first optical coupling unit is an optical coupler, and the unequal-arm polarization control interferometer further comprises two polarizers arranged on the first transmission optical path and the second transmission optical path respectively, 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 first transmission optical path or the second transmission optical path is a 90° twisted polarization maintaining optical fiber, or, 26. The apparatus of claim 25, wherein, ​ The unequal-arm polarization control interferometer further comprises a 90° polarization state rotator arranged on the first transmission light path or the second transmission light path, for rotating the polarization state of the passing sub-light pulse by 90°.

27. The apparatus of claim 23, wherein, The first light coupling unit and the second light coupling unit are the same device, and the unequal-arm polarization control interferometer further comprises two mirrors, The two output ports of the first light coupling unit are connected with one end of the first transmission light path and one end of the second transmission light path respectively, and the two mirrors are connected with the other end of the first transmission light path and the other end of the second transmission light path respectively.

28. The apparatus of claim 27, wherein, The same device is a polarization beam splitter, and the intrinsic polarization state of the polarization beam splitter is the intrinsic polarization state direction of the unequal-arm polarization control interferometer.

29. The apparatus of claim 28, wherein, The two mirrors are quarter-wave plate mirrors or 90° Faraday rotation mirrors. Alternatively, the unequal-arm polarization control interferometer further comprises two polarizers, The two polarizers are arranged on the first transmission light path and the second transmission light path respectively, and the polarization directions of the two polarizers are not orthogonal to the corresponding intrinsic polarization states of the polarization beam splitter transmitting therethrough.

30. The apparatus of claim 27, wherein, The same device is a light coupler, and the unequal-arm polarization control interferometer further comprises two polarizers, The two polarizers are arranged on the first transmission light path and the second transmission light path respectively, and 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.

31. The apparatus of claim 23, wherein, The first transmission light path and the second transmission light path are polarization maintaining optical fibers or free space.

32. The apparatus of any one of claims 23 to 31, wherein, The unequal-arm polarization control interferometer further comprises a polarizer; The polarizer is arranged at the output port of the unequal-arm polarization control interferometer, for polarizing the output light pulse.

33. The device of claim 1, wherein, The device further comprises: A quarter-wave plate arranged between the polarization encoding module and the unequal-arm polarization control interferometer.

34. The device of claim 1, wherein, the eigen polarization state the eigen polarization state is an angle between the eigen polarization state and the eigen polarization state 35. The apparatus of claim 34, wherein, the eigen polarization state the angle between the eigen polarization state is achieved by rotating at least one of the polarization control optical path and the unequal arm polarization control interferometer; and / or The device further comprises a polarization state rotator arranged between the polarization control light path and the unequal-arm polarization control interferometer, for adjusting the included angle between the intrinsic polarization states of the polarization control light path and the unequal-arm polarization control interferometer.

36. The device of claim 1, wherein, The polarization state of the optical pulses input to the polarization encoding module is Alternatively, The polarization state of the optical pulses input to the polarization encoding module is wherein n is an integer, and The two intrinsic polarization states of the polarization encoding module, and β is any value from 0 to 2π.

37. A time phase encoding method, wherein, The time phase encoding device of any one of claims 1 to 36 is applied to realize time phase encoding.

38. A quantum communication system, wherein, The time phase encoding device of any one of claims 1 to 36 is included.

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