Integrated high-dimensional quantum key distribution system and path-polarization encoding and decoding method thereof

Abstract

The invention relates to an integrated high-dimensional quantum key distribution system and a path-polarization encoding and decoding method thereof, the system comprises a sending end chip, a receiving end chip and a single-photon detector, the sending end chip is connected with the receiving end chip through a multi-core optical fiber, and the receiving end chip is connected with the single-photon detector. The transmitting end chip can perform path-polarization joint coding, and the receiving end chip can decode a coded four-dimensional quantum state. The sending end chip and the receiving end chip are respectively provided with two selectable path coding and decoding modules, and through the coding method provided by the invention, various combined coding and decoding schemes can be realized. According to the invention, transmission of a high-dimensional quantum state can be completed by using two paths of multi-core optical fiber cores, and a complete integrated high-dimensional quantum key distribution system with high information efficiency, low cost and high robustness is provided.

Description

Technical Field

[0001] The present invention belongs to the field of quantum information technology, and in particular relates to an integrated high-dimensional quantum key distribution system and a path-polarization encoding and decoding method thereof. Background Art

[0002] Quantum Key Distribution (QKD) is based on the basic principles of quantum mechanics and "one-time-one-pad" encryption technology, which can theoretically achieve information-theoretic security for confidential communications. At present, with the growing demand for secure communications, traditional two-dimensional QKD has limitations in information capacity and is difficult to meet the needs of high-speed, high-capacity communications in the big data era. In order to achieve higher information efficiency, high-dimensional quantum key distribution (HD-QKD) technology has been developed. HD-QKD uses high-dimensional quantum states for encoding, which can improve the rate and security of key distribution. Compared with traditional quantum key distribution, high-dimensional quantum key distribution has a higher transmission rate and stronger noise resistance.

[0003] Traditional fiber transmission has problems such as loss and crosstalk, which limit the distance and efficiency of key distribution. Multi-core fiber technology greatly increases the transmission speed and can accommodate richer data information through the transmission of multiple internal cores. At the same time, it can solve the problems of limited transmission distance faced by single-mode fiber transmission. Combining multi-core fiber technology with high-dimensional quantum key distribution technology will help improve the transmission capacity and efficiency of the QKD system and obtain better performance.

[0004] In addition, in order to improve the stability and scalability of the QKD system, the combination of integrated photonics and QKD has gradually become a research hotspot. Integrated quantum chips integrate quantum devices and optical paths on the same chip, with the advantages of small size, low power consumption, light weight, high stability, and low cost, which is conducive to promoting the practical application and large-scale deployment of QKD.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides an integrated high-dimensional quantum key distribution system and its path-polarization encoding and decoding method, which can achieve high utilization of quantum bits. The system structure integrates multiple functional modules on a chip to realize a highly integrated high-dimensional quantum key distribution system, and can complete the transmission of four-dimensional quantum states using two fiber cores, providing a complete integrated QKD system with high information efficiency, low cost, high security and high robustness.

[0007] Specifically, the present invention relates to an integrated high-dimensional quantum key distribution system based on path-polarization coding, characterized in that it comprises a transmitting end chip, a multi-core optical fiber channel, a receiving end chip, and a single photon detector;

[0008] The transmitting end chip comprises a pulse laser source module, a entrapped state modulation module, a path coding module, an optical attenuation module, and a polarization coding module connected in sequence; wherein the pulse laser source module is used to generate laser pulses with random phases, the entrapped state modulation module is used to modulate the pulse light into different intensities, the path coding module is used to encode the pulse light into a path-coded quantum state, the optical attenuation module is used to attenuate the intensity of the optical pulse to a single photon level while balancing the insertion loss of the two output paths, and the polarization coding module is used to encode the polarization of the quantum state; the quantum state after the path and polarization coding is completed is transmitted to the receiving end chip via a multi-core optical fiber channel;

[0009] The receiving end chip includes two groups of polarization rotation beam splitters, four groups of optical attenuators, four groups of beam splitters, a polarization decoding module, and a path decoding module connected in sequence; wherein the polarization decoding module is used to decode the polarization information of the quantum state, and the path decoding module is used to decode the path information of the quantum state, and the quantum state after polarization and path decoding is measured in a single-photon detector.

[0010] Furthermore, the path encoding module has two optional structures: path encoding module 1 and path encoding module 2;

[0011] The path encoding module 1 includes a fifth beam splitter and a sixth beam splitter; two optical waveguides are provided between the fifth beam splitter and the sixth beam splitter, and a sixth phase modulator and a seventh phase modulator are provided on the first and second optical waveguides; the input end of the fifth beam splitter is connected to the entrapped state modulation module; the output end of the sixth beam splitter is connected to the optical attenuation module through two optical waveguides, and an eighth phase modulator and a ninth phase modulator are provided on the first and second optical waveguides;

[0012] The path coding module 2 includes a seventh beam splitter; the input end of the seventh beam splitter is connected to the entrapped state modulation module; the output end of the seventh beam splitter is connected to the optical attenuation module through two waveguides, and a tenth phase modulator and an eleventh phase modulator are provided on the first and second optical waveguides.

[0013] Furthermore, the optical attenuation module includes a first variable optical attenuator and a second variable optical attenuator; the first variable optical attenuator is connected to the upper branch waveguide output by the path encoding module; and the second variable optical attenuator is connected to the lower branch waveguide output by the path encoding module.

[0014] Further, the polarization encoding module includes a polarization encoding optical path 1 and a polarization encoding optical path 2; the input end of the polarization encoding optical path 1 is connected to the first variable optical attenuator, and the output end is connected to the first chip-fiber coupler; the input end of the polarization encoding optical path 2 is connected to the second variable optical attenuator, and the output end is connected to the second chip-fiber coupler;

[0015] The polarization encoding optical path 1 includes an eighth beam splitter, a ninth beam splitter and a first two-dimensional grating coupler; two waveguides are provided between the eighth beam splitter and the ninth beam splitter, and a twelfth phase modulator and a thirteenth phase modulator are provided on the first and second waveguides; two waveguides are provided between the ninth beam splitter and the first two-dimensional grating coupler, and a fourteenth phase modulator and a fifteenth phase modulator are provided on the first and second waveguides;

[0016] The polarization encoding optical path 2 includes a tenth beam splitter, an eleventh beam splitter and a second two-dimensional grating coupler; two waveguides are arranged between the tenth beam splitter and the eleventh beam splitter, and a sixteenth phase modulator and a seventeenth phase modulator are arranged on the first and second waveguides; two waveguides are arranged between the eleventh beam splitter and the second two-dimensional grating coupler, and an eighteenth phase modulator and a nineteenth phase modulator are arranged on the first and second waveguides.

[0017] Further, the polarization decoding module includes polarization decoding optical path one, polarization decoding optical path two, polarization decoding optical path three and polarization decoding optical path four;

[0018] The polarization decoding optical path 1 includes a sixteenth beam splitter and a seventeenth beam splitter; two waveguides are arranged between the sixteenth beam splitter and the seventeenth beam splitter, and a sixth phase compensator is arranged on the first waveguide; the input end of the sixteenth beam splitter has two upper and lower waveguide branches, the upper branch at the input end of the sixteenth beam splitter is connected to the upper branch at the output end of the twelfth beam splitter through the fifth phase compensator, and the lower branch at the input end of the sixteenth beam splitter is connected to the upper branch at the output end of the thirteenth beam splitter;

[0019] The second polarization decoding optical path includes an eighteenth beam splitter and a nineteenth beam splitter; two waveguides are arranged between the eighteenth beam splitter and the nineteenth beam splitter, and an eighth phase compensator is arranged on the first waveguide; the eighteenth beam splitter input end has two upper and lower waveguide branches, the upper branch at the eighteenth beam splitter input end is connected to the lower branch at the twelfth beam splitter output end, and the lower branch at the eighteenth beam splitter input end is connected to the lower branch at the thirteenth beam splitter output end through the seventh phase compensator;

[0020] The polarization decoding optical path three includes a 20th decibel splitter and a 21st beam splitter; two waveguides are arranged between the 21st decibel splitter and the 21st beam splitter, and a 10th phase compensator is arranged on the first waveguide; the input end of the 21st decibel splitter has two upper and lower waveguide branches, the upper branch at the input end of the 21st decibel splitter is connected to the upper branch at the output end of the 14th beam splitter through the 9th phase compensator, and the lower branch at the input end of the 21st decibel splitter is connected to the upper branch at the output end of the 15th beam splitter;

[0021] The polarization decoding optical path four includes a twenty-second beam splitter and a twenty-third beam splitter; two waveguides are arranged between the twenty-second beam splitter and the twenty-third beam splitter, and a twelfth phase compensator is arranged on the first waveguide; the input end of the twenty-second beam splitter has two upper and lower waveguide branches, the upper branch at the input end of the twenty-second beam splitter is connected to the lower branch at the output end of the fourteenth beam splitter, and the lower branch at the input end of the twenty-second beam splitter is connected to the lower branch at the output end of the fifteenth beam splitter through the eleventh phase compensator.

[0022] Furthermore, the path decoding module has two optional structures: path decoding module one and path decoding module two;

[0023] The path decoding module 1 includes a path decoding optical path 1, a path decoding optical path 2, a path decoding optical path 3 and a path decoding optical path 4;

[0024] The path decoding optical path 1 is composed of two waveguides, the upper branch waveguide connects the upper branch at the output end of the seventeenth beam splitter to the third chip-fiber coupler, and the lower branch waveguide connects the lower branch at the output end of the seventeenth beam splitter to the fourth chip-fiber coupler;

[0025] The path decoding optical path 2 is composed of a thirteenth phase compensator and a twenty-fourth beam splitter; the twenty-fourth beam splitter input end has two upper and lower waveguide branches, the upper branch of the twenty-fourth beam splitter input end is connected to the upper branch of the nineteenth beam splitter output end through the thirteenth phase compensator, and the lower branch of the twenty-fourth beam splitter input end is connected to the upper branch of the twenty-first beam splitter output end; the upper branch waveguide of the twenty-fourth beam splitter output end is connected to the fifth chip-fiber coupler, and the lower branch waveguide is connected to the sixth chip-fiber coupler;

[0026] The path decoding optical path three is composed of a fourteenth phase compensator and a twenty-fifth beam splitter; the twenty-fifth beam splitter input end has two upper and lower waveguide branches, the lower branch of the twenty-fifth beam splitter input end is connected to the lower branch of the twenty-first beam splitter output end through the fourteenth phase compensator, and the upper branch of the twenty-fifth beam splitter input end is connected to the lower branch of the nineteenth beam splitter output end; the upper branch waveguide of the twenty-fifth beam splitter output end is connected to the seventh chip-fiber coupler, and the lower branch waveguide is connected to the eighth chip-fiber coupler;

[0027] The path decoding optical path 4 is composed of two waveguides, the upper branch waveguide connects the upper branch at the output end of the twenty-third beam splitter to the ninth chip-fiber coupler, and the lower branch waveguide connects the lower branch at the output end of the twenty-third beam splitter to the tenth chip-fiber coupler;

[0028] The path decoding module 2 includes a path decoding optical path 5, a path decoding optical path 6, a path decoding optical path 7 and a path decoding optical path 8;

[0029] The path decoding optical path 5 is composed of a fifteenth phase compensator and a twenty-sixth beam splitter; the twenty-sixth beam splitter input end has two upper and lower waveguide branches, the upper branch of the twenty-sixth beam splitter input end is connected to the upper branch of the seventeenth beam splitter output end through the fifteenth phase compensator, and the lower branch of the twenty-sixth beam splitter input end is connected to the upper branch of the twenty-first beam splitter output end; the upper branch waveguide of the twenty-sixth beam splitter output end is connected to the third chip-fiber coupler, and the lower branch waveguide is connected to the fourth chip-fiber coupler;

[0030] The path decoding optical path 6 is composed of a sixteenth phase compensator and a twenty-seventh beam splitter; the twenty-seventh beam splitter input end has two upper and lower waveguide branches, the upper branch of the twenty-seventh beam splitter input end is connected to the upper branch of the nineteenth beam splitter output end through the sixteenth phase compensator, and the lower branch of the twenty-seventh beam splitter input end is connected to the upper branch of the twenty-third beam splitter output end; the upper branch waveguide of the twenty-seventh beam splitter output end is connected to the fifth chip-fiber coupler, and the lower branch waveguide is connected to the sixth chip-fiber coupler;

[0031] The path decoding optical path 7 is composed of a seventeenth phase compensator and a twenty-eighth beam splitter; the twenty-eighth beam splitter input end has two upper and lower waveguide branches, the lower branch of the twenty-eighth beam splitter input end is connected to the lower branch of the twenty-first beam splitter output end through the seventeenth phase compensator, and the upper branch of the twenty-eighth beam splitter input end is connected to the lower branch of the seventeenth beam splitter output end; the upper branch waveguide of the twenty-eighth beam splitter output end is connected to the seventh chip-fiber coupler, and the lower branch waveguide is connected to the eighth chip-fiber coupler;

[0032] The path decoding optical path eight is composed of an eighteenth phase compensator and a twenty-ninth beam splitter; the twenty-ninth beam splitter input end has two upper and lower waveguide branches, the lower branch of the twenty-ninth beam splitter input end is connected to the lower branch of the twenty-third beam splitter output end through the eighteenth phase compensator, and the upper branch of the twenty-ninth beam splitter input end is connected to the lower branch of the nineteenth beam splitter output end; the upper branch waveguide of the twenty-ninth beam splitter output end is connected to the ninth chip-fiber coupler, and the lower branch waveguide is connected to the tenth chip-fiber coupler.

[0033] Preferably, the phase compensator is a thermally tuned phase shifter, and the phase modulator is a carrier depletion phase shifter.

[0034] Furthermore, when the structure of the path encoding module is path encoding module one, the structure of the path decoding module is path decoding module one; when the structure of the path encoding module is path encoding module two, the structure of the path decoding module is path decoding module two.

[0035] Beneficial technical effects of the present invention:

[0036] (1) The system of the present invention adopts the HD-QKD scheme, a single quantum state can carry more information, can achieve higher information efficiency, and reduce the impact of detector recovery time;

[0037] (2) The space division multiplexing technology adopted by the present invention is a multi-core optical fiber solution. The high-dimensional QKD based on multi-core optical fiber has a higher transmission rate and stronger anti-noise ability, allowing a received signal with a lower signal-to-noise ratio;

[0038] (3) The present invention adopts a polarization-path encoding scheme to generate a four-dimensional quantum state in two degrees of freedom, and the transmission of the four-dimensional quantum state can be completed using two fiber cores;

[0039] (4) According to different combinations of path coding and polarization coding basis vectors, a variety of different coding schemes can be implemented to adapt to different process conditions and application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention relates to a transmitter chip structure of an integrated high-dimensional quantum key distribution system.

[0041] Figure 2 The invention relates to a path encoding module of a transmitter chip of an integrated high-dimensional quantum key distribution system.

[0042] Figure 3 The present invention relates to a path encoding module II of a transmitter chip of an integrated high-dimensional quantum key distribution system.

[0043] Figure 4 The present invention relates to a receiving end chip structure of an integrated high-dimensional quantum key distribution system

[0044] Figure 5 The invention relates to a path decoding module of a receiving end chip of an integrated high-dimensional quantum key distribution system.

[0045] Figure 6 The invention relates to a path decoding module II of a receiving end chip of an integrated high-dimensional quantum key distribution system. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments, but the scope of protection claimed in the present invention is not limited to the following specific embodiments.

[0047] Embodiment 1:

[0048] An integrated high-dimensional quantum key distribution system based on path-polarization coding includes a transmitting chip 1, a receiving chip 2, and single-photon detectors 3201-3208;

[0049] like Figure 1 As shown, the transmitting end chip 1 includes a pulse laser source module 11, a entrapped state modulation module 12, a path coding module 13, an optical attenuation module 14, and a polarization coding module 15 connected in sequence; wherein the pulse laser source module 11 is used to generate laser pulses with random phases, the entrapped state modulation module 12 is used to modulate the pulse light into different intensities, the path coding module 13 is used to encode the pulse light into a path-coded quantum state, the optical attenuation module 14 is used to attenuate the intensity of the optical pulse to a single photon level while balancing the insertion loss of the two output paths, and the polarization coding module 15 is used to encode the polarization of the quantum state; the quantum state after the path and polarization coding is completed is transmitted to the receiving end chip 2 via a multi-core optical fiber channel;

[0050] like Figure 4 As shown, the receiving end chip 2 includes two groups of polarization rotation beam splitters (2111, 2121) connected in sequence, four groups of optical attenuators (2112, 2114, 2122, 2124), four groups of beam splitters (2113, 2115, 2123, 2125), a polarization decoding module 22, and a path decoding module 23; wherein the polarization decoding module 22 is used to decode the polarization information of the quantum state, and the path decoding module 23 is used to decode the path information of the quantum state, and the quantum state after polarization and path decoding is measured in the single photon detectors 3201~3208.

[0051] The first chip-fiber coupler 3101 of the transmitting chip is connected to the first fiber-chip coupler 3103 of the receiving chip using the same multi-core fiber core, and the second chip-fiber coupler 3102 of the transmitting chip is connected to the second fiber-chip coupler 3104 of the receiving chip 2 using the same multi-core fiber core.

[0052] The pulse laser source module 11 includes an on-chip laser light source 1101, a first beam splitter 1102 and a second beam splitter 1107; two optical waveguides are provided between the first beam splitter 1102 and the second beam splitter 1107, and a first phase compensator 1103 and a first phase modulator 1104, a second phase compensator 1105 and a second phase modulator 1106 are provided on the first and second optical waveguides; the output of the laser light source 1101 is connected to the input of the first beam splitter 1102, the output of the second beam splitter 1107 is connected to the input of the third phase modulator 1108, and finally the third phase modulator 1108 is connected to the entrapped state modulation module 12;

[0053] The spoofed state modulation module 12 includes a third beam splitter 1201 and a fourth beam splitter 1206; two optical waveguides are provided between the third beam splitter 1201 and the fourth beam splitter 1206, and a third phase compensator 1202 and a fourth phase modulator 1203, a fourth phase compensator 1204 and a fifth phase modulator 1205 are provided on the first and second optical waveguides; the input of the third beam splitter 1201 is connected to the output of the third phase modulator 1108, and finally the fourth beam splitter 1206 is connected to the path encoding module 13;

[0054] The path coding module 13 has two optional structures: a path coding module 1 131 and a path coding module 2 132;

[0055] like Figure 2 As shown, the path encoding module 131 includes a fifth beam splitter 1311 and a sixth beam splitter 1314; two optical waveguides are arranged between the fifth beam splitter 1311 and the sixth beam splitter 1314, and a sixth phase modulator 1312 and a seventh phase modulator 1313 are arranged on the first and second optical waveguides; the input end of the fifth beam splitter 1311 is connected to the entrapped state modulation module 12; the output end of the sixth beam splitter 1314 is connected to the optical attenuation module 14 through two optical waveguides, and an eighth phase modulator 1315 and a ninth phase modulator 1316 are arranged on the first and second optical waveguides. During the encoding process, the sixth phase modulator 1312 and the seventh phase modulator 1313 are adjusted so that the phase difference of the optical pulses of the upper and lower branches is a, and after interference, they are output from the upper branch or the lower branch of the sixth beam splitter 1314; the eighth phase modulator 1315 and the ninth phase modulator 1316 are used to set the phase difference of the optical pulses of the upper and lower branches to b, so as to complete the path encoding. Table 1 gives the degrees of freedom in the coding path, coding Z pa (|Z0> pa =|0>、|Z1> pa =|1>),

[0056] When the quantum states are in the three basis vectors, the theoretical values ​​of the optical pulse phase difference a that needs to be set between the sixth phase modulator 1312 and the seventh phase modulator 1313 and the optical pulse phase difference b that needs to be set between the eighth phase modulator 1315 and the ninth phase modulator 1316 are.

[0057] Table 1 Working method of path encoding module - encoding quantum state

[0058] <![CDATA[Z 0pa ]]> <![CDATA[Z 1pa ]]> <![CDATA[X 0pa ]]> <![CDATA[X 1pa ]]> <![CDATA[Y 0pa ]]> <![CDATA[Y 1pa ]]> a π 0 π / 2 π / 2 π / 2 π / 2 b - - 0 π π / 2 3π / 2

[0059] like Figure 3 As shown, the path encoding module 2 132 includes a seventh beam splitter 1321; the input end of the seventh beam splitter 1321 is connected to the entrapped state modulation module 12; the beam splitting ratio of the seventh beam splitter 1321 is 1:1, and its output end is connected to the optical attenuation module 14 through two waveguides, and the tenth phase modulator 1322 and the eleventh phase modulator 1323 are provided on the first and second optical waveguides. During the encoding process, the tenth phase modulator 1322 and the eleventh phase modulator 1323 are adjusted so that the phase difference of the optical pulses of the upper and lower branches is c, and the path encoding is completed. Table 2 shows the degrees of freedom of the encoding path, the encoding When the quantum states of the two basis vectors are in the same quantum state, the theoretical value of the optical pulse phase difference c that needs to be set between the tenth phase modulator 1322 and the eleventh phase modulator 1323.

[0060] Table 2 Working method of encoding quantum state in path encoding module II

[0061] <![CDATA[X 0pa ]]> <![CDATA[X 1pa ]]> <![CDATA[Y 0pa ]]> <![CDATA[Y 1pa ]]> c 0 π π / 2 3π / 2

[0062] The optical attenuation module 14 includes a first variable optical attenuator 1401 and a second variable optical attenuator 1402; the first variable optical attenuator 1401 is connected to the upper branch waveguide output by the path encoding module 13; the variable optical attenuator 1402 is connected to the lower branch waveguide output by the path encoding module. By setting the first variable optical attenuator 1401 and the second variable optical attenuator 1402, the intensity of the optical pulse can be attenuated to the single photon level. At the same time, in the case where the insertion losses of the two branches where the variable optical attenuators are located are inconsistent, the insertion losses of the two branches can be balanced by setting the first variable optical attenuator 1401 or the second variable optical attenuator 1402.

[0063] The polarization encoding module 15 includes a polarization encoding optical path 1 151 and a polarization encoding optical path 2 152; the input end of the polarization encoding optical path 1 151 is connected to the first variable optical attenuator 1401, and the output end is connected to the first chip-fiber coupler 3101; the input end of the polarization encoding optical path 2 152 is connected to the second variable optical attenuator 1402, and the output end is connected to the second chip-fiber coupler 3102;

[0064] The polarization encoding optical path 151 includes an eighth beam splitter 1511, a ninth beam splitter 1514 and a first two-dimensional grating coupler 1517; two waveguides are provided between the eighth beam splitter 1511 and the ninth beam splitter 1514, and a twelfth phase modulator 1512 and a thirteenth phase modulator 1513 are provided on the first and second waveguides; two waveguides are provided between the ninth beam splitter 1514 and the first two-dimensional grating coupler 1517, and a fourteenth phase modulator 1515 and a fifteenth phase modulator 1516 are provided on the first and second waveguides;

[0065] The second polarization encoding optical path 152 includes a tenth beam splitter 1521, an eleventh beam splitter 1524 and a second two-dimensional grating coupler 1527; two waveguides are provided between the tenth beam splitter 1521 and the eleventh beam splitter 1524, and a sixteenth phase modulator 1522 and a seventeenth phase modulator 1523 are provided on the first and second waveguides; two waveguides are provided between the eleventh beam splitter 1524 and the second two-dimensional grating coupler 1527, and an eighteenth phase modulator 1525 and a nineteenth phase modulator 1526 are provided on the first and second waveguides;

[0066] Polarization encoding optical path 1 151 is used to polarize the optical pulse of the upper branch at the output end of the path encoding module 13, and polarization encoding optical path 2 152 is used to polarize the optical pulse of the lower branch at the output end of the path encoding module 13; the encoding method of polarization encoding optical path 1 151 is the same as that of polarization encoding optical path 2 152, and the phase difference of the upper and lower branch optical pulses is d1 (d2) and e1 (e2) respectively by setting the twelfth phase modulator 1512 and the thirteenth phase modulator 1513 (the sixteenth phase modulator 1522 and the seventeenth phase modulator 1523) and the fourteenth phase modulator 1515 and the fifteenth phase modulator 1516 (the eighteenth phase modulator 1525 and the nineteenth phase modulator 1526) to complete the modulation of any polarization state. Table 3 gives the encoding polarization degrees of freedom, encoding Z po (|Z0> po =|0>、|Z1> po =|1>), When the quantum states are in the three basis vectors, the theoretical values ​​of the optical pulse phase differences d1 (d2) and e1 (e2) that need to be set between the twelfth phase modulator 1512 and the thirteenth phase modulator 1513 (the sixteenth phase modulator 1522 and the seventeenth phase modulator 1523), and the fourteenth phase modulator 1515 and the fifteenth phase modulator 1516 (the eighteenth phase modulator 1525 and the nineteenth phase modulator 1526).

[0067] Table 3 Polarization-encoded optical path encoding quantum state method

[0068] <![CDATA[Z 0po ]]> <![CDATA[Z 1po ]]> <![CDATA[X 0po ]]> <![CDATA[X 1po ]]> <![CDATA[Y 0po ]]> <![CDATA[Y 1po ]]> d1(d2) π 0 π / 2 π / 2 π / 2 π / 2 e1(e2) - - 0 π π / 2 3π / 2

[0069] The polarization decoding module 22 includes a polarization decoding optical path 1 221, a polarization decoding optical path 222, a polarization decoding optical path 3 223 and a polarization decoding optical path 4 224;

[0070] The polarization decoding optical path 1 221 includes a sixteenth beam splitter 2212 and a seventeenth beam splitter 2214; two waveguides are provided between the sixteenth beam splitter 2212 and the seventeenth beam splitter 2214, and a sixth phase compensator 2213 is provided on the first waveguide; the input end of the sixteenth beam splitter 2212 has two upper and lower waveguide branches, the upper branch at the input end of the sixteenth beam splitter 2212 is connected to the upper branch at the output end of the twelfth beam splitter 2113 through the fifth phase compensator 2211, and the lower branch at the input end of the sixteenth beam splitter 2212 is connected to the upper branch at the output end of the thirteenth beam splitter 2115;

[0071] The second polarization decoding optical path 222 includes an eighteenth beam splitter 2222 and a nineteenth beam splitter 2224; two waveguides are provided between the eighteenth beam splitter 2222 and the nineteenth beam splitter 2224, and an eighth phase compensator 2223 is provided on the first waveguide; the input end of the eighteenth beam splitter 2222 has two upper and lower waveguide branches, the upper branch at the input end of the eighteenth beam splitter 2222 is connected to the lower branch at the output end of the twelfth beam splitter 2113, and the lower branch at the input end of the eighteenth beam splitter 2222 is connected to the lower branch at the output end of the thirteenth beam splitter 2115 through the seventh phase compensator 2221;

[0072] The polarization decoding optical path three 223 includes a second demultiplexer 2232 and a twenty-first beam splitter 2234; two waveguides are provided between the second demultiplexer 2232 and the twenty-first beam splitter 2234, and a tenth phase compensator 2233 is provided on the first waveguide; the second demultiplexer 2232 has two upper and lower waveguide branches at the input end, the upper branch at the input end of the second demultiplexer 2232 is connected to the upper branch at the output end of the fourteenth beam splitter 2123 through the ninth phase compensator 2231, and the lower branch at the input end of the second demultiplexer 2232 is connected to the upper branch at the output end of the fifteenth beam splitter 2125;

[0073] Polarization decoding optical path four 224 includes a twenty-second beam splitter 2242 and a twenty-third beam splitter 2244; two waveguides are arranged between the twenty-second beam splitter 2242 and the twenty-third beam splitter 2244, and a twelfth phase compensator 2243 is arranged on the first waveguide; the twenty-second beam splitter 2242 has two upper and lower waveguide branches at the input end, the upper branch at the input end of the twenty-second beam splitter 2242 is connected to the lower branch at the output end of the fourteenth beam splitter 2123, and the lower branch at the input end of the twenty-second beam splitter 2242 is connected to the lower branch at the output end of the fifteenth beam splitter 2125 through the eleventh phase compensator 2241.

[0074] The method of decoding quantum states by polarization decoding optical path 1 221, polarization decoding optical path 2 222, polarization decoding optical path 3 223 and polarization decoding optical path 4 224 is the same. The phase differences introduced by the fifth phase compensator 2211 (seventh phase compensator 2221, ninth phase compensator 2231, eleventh phase compensator 2241) and the sixth phase compensator 2213 (eighth phase compensator 2223, tenth phase compensator 2233, twelfth phase compensator 2243) to the upper and lower branch optical pulses are respectively f1 (f2, f3, f4) and g1 (g2, g3, g4) to complete the setting of arbitrary measurement basis vectors of polarization freedom. Table 4 shows the four groups of polarization decoding optical paths set to Z po , X po , Y po When measuring the basis vectors of the three polarization degrees of freedom, the fifth phase compensator 2211 (seventh phase compensator 2221, ninth phase compensator 2231, eleventh phase compensator 2241) and the sixth phase compensator 2213 (eighth phase compensator 2223, tenth phase compensator 2233, twelfth phase compensator 2243) need to introduce the theoretical values ​​of the optical pulse phase difference f1 (f2, f3, f4) and g1 (g2, g3, g4).

[0075] Table 4 Working method of polarization decoding optical path setting measurement basis vector

[0076] <![CDATA[Z po ]]> <![CDATA[X po ]]> <![CDATA[Y po ]]> f1(f2, f3, f4) π / 2 0 0 g1(g2, g3, g4) π / 2 π / 2 0

[0077] The path decoding module 23 has two optional structures: a path decoding module 1 231 and a path decoding module 2 232;

[0078] The path decoding module 1 231 includes a path decoding optical path 1 2311 , a path decoding optical path 2 2312 , a path decoding optical path 3 2313 and a path decoding optical path 4 2314 ;

[0079] The path decoding optical path 1 2311 is composed of two waveguides, the upper branch waveguide connects the upper branch at the output end of the seventeenth beam splitter 2214 to the third chip-fiber coupler 3105, and the lower branch waveguide connects the lower branch at the output end of the seventeenth beam splitter 2214 to the fourth chip-fiber coupler 3106;

[0080] The second path decoding optical path 2312 is composed of a thirteenth phase compensator 23121 and a twenty-fourth beam splitter 23122; the twenty-fourth beam splitter 23122 has two upper and lower waveguide branches at the input end, the upper branch at the input end of the twenty-fourth beam splitter 23122 is connected to the upper branch at the output end of the nineteenth beam splitter 2224 through the thirteenth phase compensator 23121, and the lower branch at the input end of the twenty-fourth beam splitter 23122 is connected to the upper branch at the output end of the twenty-first beam splitter 2234; the upper branch waveguide at the output end of the twenty-fourth beam splitter 23122 is connected to the fifth chip-fiber coupler 3107, and the lower branch waveguide is connected to the sixth chip-fiber coupler 3108;

[0081] The path decoding optical path three 2313 is composed of a fourteenth phase compensator 23131 and a twenty-fifth beam splitter 23132; the twenty-fifth beam splitter 23132 has two upper and lower waveguide branches at the input end, the lower branch at the input end of the twenty-fifth beam splitter 23132 is connected to the lower branch at the output end of the twenty-first beam splitter 2234 through the fourteenth phase compensator 23131, and the upper branch at the input end of the twenty-fifth beam splitter 23132 is connected to the lower branch at the output end of the nineteenth beam splitter 2224; the upper branch waveguide at the output end of the twenty-fifth beam splitter 23131 is connected to the seventh chip-fiber coupler 3109, and the lower branch waveguide is connected to the eighth chip-fiber coupler 3110;

[0082] The path decoding optical path 4 2314 is composed of two waveguides, the upper branch waveguide connects the upper branch at the output end of the twenty-third beam splitter 2244 to the ninth chip-fiber coupler 3111, and the lower branch waveguide connects the lower branch at the output end of the twenty-third beam splitter 2244 to the tenth chip-fiber coupler 3112;

[0083] The path decoding optical path 1 2311 and the path decoding optical path 4 2314 are set to have the same path freedom Z pa Measurement basis vector; path decoding optical path 2312 and path decoding optical path 3 2313 are set to the measurement basis vector with the same path degree of freedom; when the phase difference introduced by the thirteenth phase compensator 23121 and the fourteenth phase compensator 23131 to the upper and lower branches is set to 0, the path decoding optical path 2312 and the path decoding optical path 3 2313 are set to X pa When the phase difference introduced by the thirteenth phase compensator 23121 and the fourteenth phase compensator 23131 on the upper and lower branches is set to -π / 2, the path decoding optical path 2312 and the path decoding optical path 3 2313 are set to Y pa Measure the basis vector.

[0084] The decoding module 232 includes a path decoding optical path 5 2321, a path decoding optical path 6 2322, a path decoding optical path 7 2323 and a path decoding optical path 8 2324;

[0085] The path decoding optical path 5 2321 is composed of a fifteenth phase compensator 23211 and a twenty-sixth beam splitter 23212; the twenty-sixth beam splitter 23212 has two upper and lower waveguide branches at its input end, the upper branch at the input end of the twenty-sixth beam splitter 23212 is connected to the upper branch at the output end of the seventeenth beam splitter 2214 through the fifteenth phase compensator 23211, and the lower branch at the input end of the twenty-sixth beam splitter 23212 is connected to the upper branch at the output end of the twenty-first beam splitter 2234; the upper branch waveguide at the output end of the twenty-sixth beam splitter 23212 is connected to the third chip-fiber coupler 3105, and the lower branch waveguide is connected to the fourth chip-fiber coupler 3106;

[0086] The path decoding optical path 6 2322 is composed of a sixteenth phase compensator 23221 and a twenty-seventh beam splitter 23222; the twenty-seventh beam splitter 23222 has two upper and lower waveguide branches at the input end, the upper branch at the input end of the twenty-seventh beam splitter 23222 is connected to the upper branch at the output end of the nineteenth beam splitter 2224 through the sixteenth phase compensator 23221, and the lower branch at the input end of the twenty-seventh beam splitter 23222 is connected to the upper branch at the output end of the twenty-third beam splitter 2244; the upper branch waveguide at the output end of the twenty-seventh beam splitter 23222 is connected to the fifth chip-fiber coupler 3107, and the lower branch waveguide is connected to the sixth chip-fiber coupler 3108;

[0087] The path decoding optical path 7 2323 is composed of the seventeenth phase compensator 23231 and the twenty-eighth beam splitter 23232; the twenty-eighth beam splitter 23232 has two upper and lower waveguide branches at the input end, the lower branch at the input end of the twenty-eighth beam splitter 23232 is connected to the lower branch at the output end of the twenty-first beam splitter 2234 through the seventeenth phase compensator 23231, and the upper branch at the input end of the twenty-eighth beam splitter 23232 is connected to the lower branch at the output end of the seventeenth beam splitter 2214; the upper branch waveguide at the output end of the twenty-eighth beam splitter 23232 is connected to the seventh chip-fiber coupler 3109, and the lower branch waveguide is connected to the eighth chip-fiber coupler 3110;

[0088] The path decoding optical path eight 2324 is composed of an eighteenth phase compensator 23241 and a twenty-ninth beam splitter 23242; the twenty-ninth beam splitter 23242 has two upper and lower waveguide branches at the input end, the lower branch at the input end of the twenty-ninth beam splitter 23242 is connected to the lower branch at the output end of the twenty-third beam splitter 2244 through the eighteenth phase compensator 23241, and the upper branch at the input end of the twenty-ninth beam splitter 23242 is connected to the lower branch at the output end of the nineteenth beam splitter 2224; the upper branch waveguide at the output end of the twenty-ninth beam splitter 23242 is connected to the ninth chip-fiber coupler 3111, and the lower branch waveguide is connected to the tenth chip-fiber coupler 3112.

[0089] The path decoding optical path five 2321 and the path decoding optical path seven 2323 are set as the measurement basis vectors with the same path degrees of freedom; when the phase difference introduced by the fifteenth phase compensator 23211 and the seventeenth phase compensator 23231 to the upper and lower branches is set to 0, the path decoding optical path five 2321 and the path decoding optical path seven 2323 are set to X pa When the phase difference introduced by the fifteenth phase compensator 23211 and the seventeenth phase compensator 23231 on the upper and lower branches is set to -π / 2, the path decoding optical path five 2321 and the path decoding optical path seven 2323 are set to Y pa Measure the basis vector.

[0090] The path decoding optical path 6 2322 and the path decoding optical path 8 2324 are set as the measurement basis vectors with the same path degrees of freedom; when the phase difference introduced by the sixteenth phase compensator 23221 and the eighteenth phase compensator 23241 to the upper and lower branches is set to 0, the path decoding optical path 6 2322 and the path decoding optical path 8 2324 are set to X pa When the phase difference introduced by the sixteenth phase compensator 23221 and the eighteenth phase compensator 23241 on the upper and lower branches is set to -π / 2, the path decoding optical path six 2322 and the path decoding optical path eight 2324 are set to Y pa Measure the basis vector.

[0091] The phase compensator is a thermally tuned phase shifter; the phase modulator is a carrier depletion phase shifter that can perform rapid modulation of quantum states.

[0092] The encoding basis vector set of path freedom is λ∈{Z pa ,X pa ,Y pa}, the encoding set of polarization degrees of freedom is χ∈{Z po ,X po ,Y po}. The direct product of the quantum states of the two degrees of freedom of path and polarization can construct a four-dimensional quantum state Different combinations of λ and χ can construct different quantum state combinations in four-dimensional space. Choose any two sets of quantum states and If they satisfy: Then the combination of these two sets of quantum states can meet the requirements of high-dimensional quantum key distribution. In particular, It is called the Z-basis quantum state of high-dimensional quantum key distribution. It is called the X-basis quantum state of high-dimensional quantum key distribution.

[0093] When encoding high-dimensional quantum states, if the path freedom Z is used paBasis (λ = Z pa ), it is necessary to use a path encoding module 131 and a path decoding module 231 to encode and decode high-dimensional quantum states; if the path freedom Z is not used pa Basis (λ = Z pa ), the path encoding module 2 132 and the path decoding module 2 232 are used to encode and decode the high-dimensional quantum state.

[0094] Using the integrated high-dimensional quantum key distribution system and its path-polarization encoding method provided in this embodiment, two encoding and decoding methods as shown in Embodiment 2 and Embodiment 3 can be implemented.

[0095] Embodiment 2:

[0096] An HD-QKD system using a path encoding module 131 and a path decoding module 231.

[0097] In this embodiment, the Z-basis quantum state for HD-QKD is expressed as: The X-basis quantum state is expressed as:

[0098] Step S1: The pulse laser module 11 generates discrete pulse light with randomized phases.

[0099] Step S2: The decoy state modulation module 12 performs intensity modulation on the pulse light to generate optical signals in the signal state and the decoy state.

[0100] Step S3: The entrapped state modulation module 12 generates a signal state, adjusts the sixth phase modulator 1312 and the seventh phase modulator 1313 so that the output light intensity of the first chip-fiber coupler 3101 is maximized and the output light intensity of the second chip-fiber coupler 3102 is minimized, and then adjusts the first variable optical attenuator 1401 so that the average number of photons of the pulse light output by the first chip-fiber coupler 3101 is the average number of photons in the signal state; then adjusts the sixth phase modulator 1312 and the seventh phase modulator 1313 so that the output light intensity of the first chip-fiber coupler 1313 is minimized and the output light intensity of the second chip-fiber coupler 3102 is maximized, and then adjusts the second variable optical attenuator 1402 so that the average number of photons of the pulse light output by the second chip-fiber coupler 1402 is the average number of photons in the signal state.

[0101] Step S4: as shown in Table 6, adjust the sixth phase modulator 1312, the seventh phase modulator 1313, the eighth phase modulator 1315, the ninth phase modulator 1316, the twelfth phase modulator 1512, the thirteenth phase modulator 1513, the fourteenth phase modulator 1515, the fifteenth phase modulator 1516, the sixteenth phase modulator 1522, the seventeenth phase modulator 1523, the eighteenth phase modulator 1525, and the nineteenth phase modulator 1526 to complete the Z-basis and X-basis quantum state encoding of HD-QKD.

[0102] Table 6 Working method of encoding Z-basis and X-basis quantum states when using path encoding module 131

[0103] <![CDATA[Z0]]> <![CDATA[Z1]]> <![CDATA[Z2]]> <![CDATA[Z3]]> <![CDATA[X0]]> <![CDATA[X1]]> <![CDATA[X2]]> <![CDATA[X3]]> a π π 0 0 π / 2 π / 2 π / 2 π / 2 b - - - - 0 0 π π d1 π 0 - - π / 2 π / 2 π / 2 π / 2 e1 - - - - 0 π 0 π d2 - - π 0 π / 2 π / 2 π / 2 π / 2 e2 - - - - 0 π 0 π

[0104] Step S5: Set the polarization decoding optical path 1 221 and the polarization decoding optical path 4 224 to Z po The measurement basis vector, polarization decoding optical path 222 and polarization decoding optical path 3 223 are set to X po Measure the basis vector; set the path decoding optical path 1 2311 and the path decoding optical path 4 2314 to Z pa Measuring basis vector, path decoding optical path 2312 and path decoding optical path 3 2313 are set to X pa The polarization decoding optical path 1 221, the polarization decoding optical path 4 224, the path decoding optical path 1 2311, and the path decoding optical path 4 2314 decode the Z basis quantum state of HD-QKD; the polarization decoding optical path 2 222, the polarization decoding optical path 3 223, the path decoding optical path 2 2312, and the path decoding optical path 3 2313 decode the X basis quantum state of HD-QKD.

[0105] Step S6: When the encoding and decoding basis vectors selected by the HD-QKD sender and receiver are the same, the quantum states corresponding to the responses of different single-photon detectors are shown in Table 7.

[0106] Table 7 Correspondence between single photon detector and quantum state when using path decoding module 231

[0107]

[0108] Step S7: Finally, the communicating parties generate a security key according to the HD-QKD protocol post-processing method.

[0109] Embodiment three:

[0110] An HD-QKD system using a path encoding module two 132 and a path decoding module two 232.

[0111] In this embodiment, the Z-basis quantum state for HD-QKD is expressed as: The X-basis quantum state is expressed as:

[0112] Step S1: The pulse laser module 11 generates discrete pulse light with randomized phases.

[0113] Step S2: The decoy state modulation module 12 performs intensity modulation on the pulse light to generate optical signals in the signal state and the decoy state.

[0114] Step S3: The entrapped state modulation module 12 generates a signal state, and adjusts the first variable optical attenuator 1401 so that the average number of photons of the pulse light output by the first chip-fiber coupler 3101 is half of the average number of photons of the signal state; then adjusts the second variable optical attenuator 1402 so that the average number of photons of the pulse light output by the second chip-fiber coupler 3102 is half of the average number of photons of the signal state.

[0115] Step S4: as shown in Table 8, adjust the tenth phase modulator 1322, the eleventh phase modulator 1323, the twelfth phase modulator 1512, the thirteenth phase modulator 1513, the fourteenth phase modulator 1515, the fifteenth phase modulator 1516, the sixteenth phase modulator 1522, the seventeenth phase modulator 1523, the eighteenth phase modulator 1525, and the nineteenth phase modulator 1526 to complete the Z-basis and X-basis quantum state encoding of HD-QKD.

[0116] Table 8 Encoding Z-basis and X-basis quantum states when using path encoding module 131

[0117] <![CDATA[Z0]]> <![CDATA[Z1]]> <![CDATA[Z2]]> <![CDATA[Z3]]> <![CDATA[X0]]> <![CDATA[X1]]> <![CDATA[X2]]> <![CDATA[X3]]> a π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 b π / 2 π / 2 3π / 2 3π / 2 0 0 π π d1 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 e1 π / 2 3π / 2 π / 2 3π / 2 0 π 0 π d2 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 π / 2 e2 π / 2 3π / 2 π / 2 3π / 2 0 π 0 π

[0118] Step S5: Set the polarization decoding optical path 1 221 and the polarization decoding optical path 3 223 to Y po The measurement basis vector, polarization decoding optical path 222 and polarization decoding optical path 4 224 are set to X po Measure the basis vector; set the path decoding optical path five 2321 and the path decoding optical path seven 2323 to Y pa Measure the basis vector and set the path decoding optical path six 2322 and the path decoding optical path eight 2324 to X pa The polarization decoding optical path 1 221, the polarization decoding optical path 3 223, the path decoding optical path 5 2321, and the path decoding optical path 7 2323 decode the Z basis quantum state of HD-QKD; the polarization decoding optical path 2 222, the polarization decoding optical path 4 224, the path decoding optical path 6 2322, and the path decoding optical path 8 2324 decode the X basis quantum state of HD-QKD.

[0119] Step S6: When the encoding and decoding basis vectors selected by the HD-QKD sender and receiver are the same, the quantum states corresponding to the responses of different single-photon detectors are shown in Table 9.

[0120] Table 9 Correspondence between single photon detector and quantum state when using path decoding module 232

[0121]

[0122] Step S7: Finally, the communicating parties generate a security key according to the HD-QKD protocol post-processing method.

Claims

1. An integrated high-dimensional quantum key distribution system based on path-polarization coding, characterized in that: It includes a transmitter chip, a multi-core optical fiber channel, a receiver chip, and a single-photon detector; The transmitting end chip comprises a pulse laser source module, a entrapped state modulation module, a path coding module, an optical attenuation module, and a polarization coding module connected in sequence; wherein the pulse laser source module is used to generate laser pulses with random phases, the entrapped state modulation module is used to modulate the pulse light into different intensities, the path coding module is used to encode the pulse light into a path-coded quantum state, the optical attenuation module is used to attenuate the intensity of the optical pulse to a single photon level while balancing the insertion loss of the two output paths, and the polarization coding module is used to encode the polarization of the quantum state; the quantum state after the path and polarization coding is completed is transmitted to the receiving end chip via a multi-core optical fiber channel; The receiving end chip includes two groups of polarization rotation beam splitters, four groups of optical attenuators, four groups of beam splitters, a polarization decoding module, and a path decoding module connected in sequence; wherein the polarization decoding module is used to decode the polarization information of the quantum state, and the path decoding module is used to decode the path information of the quantum state, and the quantum state after polarization and path decoding is measured in a single-photon detector.

2. An integrated high-dimensional quantum key distribution system based on path-polarization coding according to claim 1, characterized in that: The path coding module has two optional structures: path coding module 1 and path coding module 2; The path encoding module 1 includes a fifth beam splitter and a sixth beam splitter; two optical waveguides are provided between the fifth beam splitter and the sixth beam splitter, and a sixth phase modulator and a seventh phase modulator are provided on the first and second optical waveguides; the input end of the fifth beam splitter is connected to the entrapped state modulation module; the output end of the sixth beam splitter is connected to the optical attenuation module through two optical waveguides, and an eighth phase modulator and a ninth phase modulator are provided on the first and second optical waveguides; The path coding module 2 includes a seventh beam splitter; the input end of the seventh beam splitter is connected to the entrapped state modulation module; the output end of the seventh beam splitter is connected to the optical attenuation module through two waveguides, and a tenth phase modulator and an eleventh phase modulator are provided on the first and second optical waveguides.

3. The integrated high-dimensional quantum key distribution system based on path-polarization coding according to claim 1, characterized in that: The optical attenuation module includes a first variable optical attenuator and a second variable optical attenuator; the first variable optical attenuator is connected to the upper branch waveguide output by the path coding module; the second variable optical attenuator is connected to the lower branch waveguide output by the path coding module.

4. The integrated high-dimensional quantum key distribution system based on path-polarization coding according to claim 1, characterized in that: The polarization encoding module comprises a polarization encoding optical path 1 and a polarization encoding optical path 2; the input end of the polarization encoding optical path 1 is connected to the first variable optical attenuator, and the output end is connected to the first chip-fiber coupler; the input end of the polarization encoding optical path 2 is connected to the second variable optical attenuator, and the output end is connected to the second chip-fiber coupler; The polarization encoding optical path 1 includes an eighth beam splitter, a ninth beam splitter and a first two-dimensional grating coupler; two waveguides are provided between the eighth beam splitter and the ninth beam splitter, and a twelfth phase modulator and a thirteenth phase modulator are provided on the first and second waveguides; two waveguides are provided between the ninth beam splitter and the first two-dimensional grating coupler, and a fourteenth phase modulator and a fifteenth phase modulator are provided on the first and second waveguides; The polarization encoding optical path 2 includes a tenth beam splitter, an eleventh beam splitter and a second two-dimensional grating coupler; two waveguides are arranged between the tenth beam splitter and the eleventh beam splitter, and a sixteenth phase modulator and a seventeenth phase modulator are arranged on the first and second waveguides; two waveguides are arranged between the eleventh beam splitter and the second two-dimensional grating coupler, and an eighteenth phase modulator and a nineteenth phase modulator are arranged on the first and second waveguides.

5. The integrated high-dimensional quantum key distribution system based on path-polarization coding according to claim 1, characterized in that: The polarization decoding module includes polarization decoding optical path one, polarization decoding optical path two, polarization decoding optical path three and polarization decoding optical path four; The polarization decoding optical path 1 includes a sixteenth beam splitter and a seventeenth beam splitter; two waveguides are arranged between the sixteenth beam splitter and the seventeenth beam splitter, and a sixth phase compensator is arranged on the first waveguide; the input end of the sixteenth beam splitter has two upper and lower waveguide branches, the upper branch at the input end of the sixteenth beam splitter is connected to the upper branch at the output end of the twelfth beam splitter through the fifth phase compensator, and the lower branch at the input end of the sixteenth beam splitter is connected to the upper branch at the output end of the thirteenth beam splitter; The second polarization decoding optical path includes an eighteenth beam splitter and a nineteenth beam splitter; two waveguides are arranged between the eighteenth beam splitter and the nineteenth beam splitter, and an eighth phase compensator is arranged on the first waveguide; the eighteenth beam splitter input end has two upper and lower waveguide branches, the upper branch at the eighteenth beam splitter input end is connected to the lower branch at the twelfth beam splitter output end, and the lower branch at the eighteenth beam splitter input end is connected to the lower branch at the thirteenth beam splitter output end through the seventh phase compensator; The polarization decoding optical path three includes a 20th decibel splitter and a 21st beam splitter; two waveguides are arranged between the 21st decibel splitter and the 21st beam splitter, and a 10th phase compensator is arranged on the first waveguide; the input end of the 21st decibel splitter has two upper and lower waveguide branches, the upper branch at the input end of the 21st decibel splitter is connected to the upper branch at the output end of the 14th beam splitter through the 9th phase compensator, and the lower branch at the input end of the 21st decibel splitter is connected to the upper branch at the output end of the 15th beam splitter; The polarization decoding optical path four includes a twenty-second beam splitter and a twenty-third beam splitter; two waveguides are arranged between the twenty-second beam splitter and the twenty-third beam splitter, and a twelfth phase compensator is arranged on the first waveguide; the input end of the twenty-second beam splitter has two upper and lower waveguide branches, the upper branch at the input end of the twenty-second beam splitter is connected to the lower branch at the output end of the fourteenth beam splitter, and the lower branch at the input end of the twenty-second beam splitter is connected to the lower branch at the output end of the fifteenth beam splitter through the eleventh phase compensator.

6. The integrated high-dimensional quantum key distribution system based on path-polarization coding according to claim 1, characterized in that: The path decoding module has two optional structures: path decoding module one and path decoding module two; The path decoding module 1 includes a path decoding optical path 1, a path decoding optical path 2, a path decoding optical path 3 and a path decoding optical path 4; The path decoding optical path 1 is composed of two waveguides, the upper branch waveguide connects the upper branch at the output end of the seventeenth beam splitter to the third chip-fiber coupler, and the lower branch waveguide connects the lower branch at the output end of the seventeenth beam splitter to the fourth chip-fiber coupler; The path decoding optical path 2 is composed of a thirteenth phase compensator and a twenty-fourth beam splitter; the twenty-fourth beam splitter input end has two upper and lower waveguide branches, the upper branch of the twenty-fourth beam splitter input end is connected to the upper branch of the nineteenth beam splitter output end through the thirteenth phase compensator, and the lower branch of the twenty-fourth beam splitter input end is connected to the upper branch of the twenty-first beam splitter output end; the upper branch waveguide of the twenty-fourth beam splitter output end is connected to the fifth chip-fiber coupler, and the lower branch waveguide is connected to the sixth chip-fiber coupler; The path decoding optical path three is composed of a fourteenth phase compensator and a twenty-fifth beam splitter; the twenty-fifth beam splitter input end has two upper and lower waveguide branches, the lower branch of the twenty-fifth beam splitter input end is connected to the lower branch of the twenty-first beam splitter output end through the fourteenth phase compensator, and the upper branch of the twenty-fifth beam splitter input end is connected to the lower branch of the nineteenth beam splitter output end; the upper branch waveguide of the twenty-fifth beam splitter output end is connected to the seventh chip-fiber coupler, and the lower branch waveguide is connected to the eighth chip-fiber coupler; The path decoding optical path 4 is composed of two waveguides, the upper branch waveguide connects the upper branch at the output end of the twenty-third beam splitter to the ninth chip-fiber coupler, and the lower branch waveguide connects the lower branch at the output end of the twenty-third beam splitter to the tenth chip-fiber coupler; The path decoding module 2 includes a path decoding optical path 5, a path decoding optical path 6, a path decoding optical path 7 and a path decoding optical path 8; The path decoding optical path 5 is composed of a fifteenth phase compensator and a twenty-sixth beam splitter; the twenty-sixth beam splitter input end has two upper and lower waveguide branches, the upper branch of the twenty-sixth beam splitter input end is connected to the upper branch of the seventeenth beam splitter output end through the fifteenth phase compensator, and the lower branch of the twenty-sixth beam splitter input end is connected to the upper branch of the twenty-first beam splitter output end; the upper branch waveguide of the twenty-sixth beam splitter output end is connected to the third chip-fiber coupler, and the lower branch waveguide is connected to the fourth chip-fiber coupler; The path decoding optical path 6 is composed of a sixteenth phase compensator and a twenty-seventh beam splitter; the twenty-seventh beam splitter input end has two upper and lower waveguide branches, the upper branch of the twenty-seventh beam splitter input end is connected to the upper branch of the nineteenth beam splitter output end through the sixteenth phase compensator, and the lower branch of the twenty-seventh beam splitter input end is connected to the upper branch of the twenty-third beam splitter output end; the upper branch waveguide of the twenty-seventh beam splitter output end is connected to the fifth chip-fiber coupler, and the lower branch waveguide is connected to the sixth chip-fiber coupler; The path decoding optical path 7 is composed of a seventeenth phase compensator and a twenty-eighth beam splitter; the twenty-eighth beam splitter input end has two upper and lower waveguide branches, the lower branch of the twenty-eighth beam splitter input end is connected to the lower branch of the twenty-first beam splitter output end through the seventeenth phase compensator, and the upper branch of the twenty-eighth beam splitter input end is connected to the lower branch of the seventeenth beam splitter output end; the upper branch waveguide of the twenty-eighth beam splitter output end is connected to the seventh chip-fiber coupler, and the lower branch waveguide is connected to the eighth chip-fiber coupler; The path decoding optical path eight is composed of an eighteenth phase compensator and a twenty-ninth beam splitter; the twenty-ninth beam splitter input end has two upper and lower waveguide branches, the lower branch of the twenty-ninth beam splitter input end is connected to the lower branch of the twenty-third beam splitter output end through the eighteenth phase compensator, and the upper branch of the twenty-ninth beam splitter input end is connected to the lower branch of the nineteenth beam splitter output end; the upper branch waveguide of the twenty-ninth beam splitter output end is connected to the ninth chip-fiber coupler, and the lower branch waveguide is connected to the tenth chip-fiber coupler.

7. An integrated high-dimensional quantum key distribution system based on path-polarization coding according to claims 1-6, characterized in that: The phase compensator is a thermally tuned phase shifter, and the phase modulator is a carrier depletion phase shifter.

8. A high-dimensional quantum key distribution method based on an integrated high-dimensional quantum key distribution system based on path-polarization coding according to any one of claims 1 to 7, characterized in that: When the structure of the path encoding module is path encoding module one, the structure of the corresponding path decoding module is path decoding module one; when the structure of the path encoding module is path encoding module two, the structure of the corresponding path decoding module is path decoding module two.

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