A double-field quantum key distribution system based on thin-film lithium niobate integration

Abstract

The application discloses a double-field quantum key distribution system based on thin film lithium niobate integration, which comprises a sending end integrated chip of two legal communication users Alice and Bob and a measuring end integrated chip of an untrusted third party Charlie; the sending end integrated chip of the Alice and the Bob each comprises a first intensity modulation module, a second intensity modulation module, a third intensity modulation module, a phase modulation module and an attenuation monitoring module; and the measuring end chip comprises a PC1 module, a PC2 module, a twenty-first hot-tunable phase shifter, a twenty-second hot-tunable phase shifter, a twenty-first beam splitter and a single-photon detector and the like; the sending end chip of the application can modulate high-fidelity quantum states, and can compensate for polarization disturbance and phase offset of an optical fiber link; meanwhile, a high-speed, stable and low-cost wafer-level double-field quantum key distribution system can be realized, and large-scale deployment of a long-distance quantum secure communication network is promoted.

Description

Technical Field

[0001] This invention relates to the field of quantum information technology, and in particular to a dual-field quantum key distribution system based on thin-film lithium niobate integration. Background Technology

[0002] While network communication has brought many conveniences to daily life, it has also brought information security challenges. With the rapid development of technology, especially quantum computers, their powerful computing capabilities have rendered classical data encryption algorithms unreliable. Quantum Key Distribution (QKD), whose security is guaranteed by the principles of quantum mechanics, is one of the most promising solutions for secure communication in the future.

[0003] Overcoming the long-distance key generation rate limit (PLOB limit) in relay-free quantum key distribution and implementing QKD over long-distance fiber optic links remains a major challenge for large-scale fiber optic quantum communication systems. In 2018, Lucamaruini proposed a novel QKD protocol—Twin-Field Quantum Key Distribution (TF-QKD)—which enables secure key transmission over ultra-long distances. The proposed "send-no-send" improved TF-QKD protocol effectively enhances the system's tolerance to phase noise, increasing its practical feasibility. Researchers have already achieved kilometer-scale TF-QKD experimental demonstrations based on this variant. However, current TF-QKD experimental systems are primarily built upon traditional fiber optic components, and their large size and high cost are key obstacles to large-scale deployment. Therefore, developing a low-cost and highly integrated wafer-level TF-QKD system has become a current research hotspot.

[0004] By comparing the performance of various integrated platforms and devices, we found that thin-film lithium niobate possesses superior characteristics such as a wide transparency window, a large electro-optic coefficient, strong electro-optic and nonlinear effects, and high waveguide refractive index. These characteristics enable integrated unit devices based on thin-film lithium niobate to have advantages such as high modulation bandwidth, high extinction ratio, low insertion loss, low half-wave voltage, and low phase correlation loss. These are key indicators for achieving high-speed, high-fidelity quantum state preparation. Therefore, to promote the integration and large-scale deployment of TF-QKD, we propose a TF-QKD system based on a thin-film lithium niobate platform. This not only greatly improves the transmission distance and key rate of TF-QKD but also enhances the practical security of the protocol. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the aforementioned existing problems, this invention is proposed. Therefore, this invention provides a dual-field quantum key distribution system based on thin-film lithium niobate integration to solve the problems of excessive size and high cost associated with building TF-QKD experimental systems using traditional fiber optic components.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a dual-field quantum key distribution system based on thin-film lithium niobate integration, comprising:

[0008] The system architecture of the communication users Alice and Bob both includes a first intensity modulation module, a second intensity modulation module, a third intensity modulation module, a phase modulation module, and an attenuation monitoring module connected in sequence.

[0009] The third-party Charlie includes a PC1 module, a PC2 module, a 21st thermally tuned phase shifter, a 22nd thermally tuned phase shifter, a first single-photon detector, a second single-photon detector, a 21st beam splitter, a third single-photon detector, and a fourth single-photon detector.

[0010] The first intensity modulation module of the communication user Alice is connected to the second intensity modulation module, the second intensity modulation module is connected to the third intensity modulation module, the third intensity modulation module is connected to the phase modulation module, the phase modulation module is connected to the attenuation monitoring module, the attenuation monitoring module is connected to the third fiber coupler, the third fiber coupler is connected to the PC1 module of the third party Charlie through the first commercial fiber, the PC1 module is connected to the first single-photon detector and the twenty-first thermally tunable phase shifter, and the twenty-first thermally tunable phase shifter is connected to the twenty-first beam splitter; the first intensity modulation module of the communication user Bob is connected to the second intensity modulation module. The control module is connected to the second intensity modulation module, the second intensity modulation module is connected to the third intensity modulation module, the third intensity modulation module is connected to the phase modulation module, the phase modulation module is connected to the attenuation monitoring module, the attenuation monitoring module is connected to the sixth fiber coupler, the sixth fiber coupler is connected to the third-party Charlie's PC2 module through the second commercial fiber, the PC2 module is connected to the second single-photon detector and the twenty-twelfth thermally tuned phase shifter respectively, the twenty-twelfth thermally tuned phase shifter is connected to the twenty-first beam splitter, and the twenty-first beam splitter is connected to the third single-photon detector and the fourth single-photon detector respectively;

[0011] The two communicating users, Alice and Bob, as well as the third party Charlie, are all integrated on a thin-film lithium niobate material platform.

[0012] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, wherein: the first intensity modulation module of the communication user Alice includes: a first beam splitter and a second beam splitter;

[0013] Two optical arms are provided between the first beam splitter and the second beam splitter. A first thermally tunable phase shifter and a first carrier dispersive phase shifter are connected in series on the first optical arm, and a second thermally tunable phase shifter and a second carrier dispersive phase shifter are connected in series on the second optical arm. The first thermally tunable phase shifter and the second thermally tunable phase shifter are both connected to the first beam splitter, and the first carrier dispersive phase shifter and the second carrier dispersive phase shifter are both connected to the second beam splitter. The first beam splitter is connected to a first optical fiber coupler.

[0014] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, wherein: the second intensity modulation module of the communication user Alice includes: a third beam splitter and a fourth beam splitter;

[0015] Two optical arms are provided between the third and fourth beam splitters. A third thermally tunable phase shifter and a third carrier dispersive phase shifter are connected in series on the first optical arm, and a fourth thermally tunable phase shifter and a fourth carrier dispersive phase shifter are connected in series on the second optical arm. Both the third and fourth thermally tunable phase shifters are connected to the third beam splitter, and both the third and fourth carrier dispersive phase shifters are connected to the fourth beam splitter. The second beam splitter is connected to the third beam splitter.

[0016] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, wherein: the third intensity modulation module of the communication user Alice includes: a fifth beam splitter and a sixth beam splitter;

[0017] Two optical arms are provided between the fifth and sixth beam splitters. A fifth thermally tunable phase shifter and a fifth carrier dispersive phase shifter are connected in series on the first optical arm, and a sixth thermally tunable phase shifter and a sixth carrier dispersive phase shifter are connected in series on the second optical arm. Both the fifth and sixth thermally tunable phase shifters are connected to the fifth beam splitter, and both the fifth and sixth carrier dispersive phase shifters are connected to the sixth beam splitter. The fourth beam splitter is connected to the fifth beam splitter.

[0018] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, the phase modulation module of the communication user Alice includes: a seventh carrier dispersive phase shifter, an eighth carrier dispersive phase shifter, and a ninth carrier dispersive phase shifter.

[0019] The seventh carrier dispersive phase shifter is connected to the eighth carrier dispersive phase shifter, and the eighth carrier dispersive phase shifter is connected to the ninth carrier dispersive phase shifter; the seventh carrier dispersive phase shifter is connected to the sixth beam splitter, and the ninth carrier dispersive phase shifter is connected to the seventh beam splitter.

[0020] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, wherein: the attenuation monitoring module of the communication user Alice includes: an eighth beam splitter, a first variable optical attenuator, and a first optical power detector;

[0021] The eighth beam splitter is connected to the first variable optical attenuator and the first optical power detector, respectively. The first variable optical attenuator is connected to the seventh beam splitter. The eighth beam splitter is also connected to the second fiber coupler and the third fiber coupler, respectively.

[0022] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, wherein the third-party Charlie's PC1 module includes: a first polarization rotating beam splitter, a seventeenth beam splitter, and an eighteenth beam splitter;

[0023] Two optical arms are provided between the first polarization rotating beam splitter and the seventeenth beam splitter. A thirteenth thermally tunable phase shifter is provided on the first optical arm, and a fourteenth thermally tunable phase shifter is provided on the second optical arm. Two optical arms are provided between the seventeenth and eighteenth beam splitters. A fifteenth thermally tunable phase shifter is provided on the first optical arm, and a sixteenth thermally tunable phase shifter is provided on the second optical arm. The first polarization rotating beam splitter is connected to a third fiber coupler via a first commercial fiber. The eighteenth beam splitter is connected to the twenty-first thermally tunable phase shifter and the first single-photon detector, respectively.

[0024] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, the system comprises: a second polarization rotating beam splitter, a nineteenth beam splitter, and a twenty-tenth beam splitter.

[0025] Two optical arms are provided between the second polarization rotating beamsplitter and the nineteenth beamsplitter. A seventeenth thermally tunable phase shifter is provided on the first optical arm, and an eighteenth thermally tunable phase shifter is provided on the second optical arm. Two optical arms are provided between the nineteenth beamsplitter and the twentyth beamsplitter. A nineteenth thermally tunable phase shifter is provided on the first optical arm, and a twentieth thermally tunable phase shifter is provided on the second optical arm. The second polarization rotating beamsplitter is connected to a sixth fiber coupler via a second commercial fiber. The second beamsplitter is connected to a twenty-second thermally tunable phase shifter and a second single-photon detector, respectively.

[0026] As a preferred embodiment of the dual-field quantum key distribution system based on thin-film lithium niobate integration described in this invention, wherein: the two communicating users, Alice and Bob, as well as the third party Charlie, are all integrated on a thin-film lithium niobate material platform, including: all connections are made via lithium niobate optical waveguides.

[0027] Compared with existing technologies, the beneficial effects of the invention are:

[0028] 1. This invention can realize a stable, secure, and high-speed modulated dual-field quantum key distribution system, which is not only applicable to the TF-QKD protocol, but also supports other mainstream long-distance communication protocols, including the "send-no-send" improved TF-QKD protocol and phase-matched quantum key distribution (PM-QKD);

[0029] 2. The intensity modulation of the TF-QKD protocol using this invention can achieve a very high extinction ratio; since thin-film lithium niobate does not involve the dynamic process of charge carriers, the intensity correlation of phase modulation can be greatly reduced.

[0030] 3. The extinction ratio of the intensity modulator based on thin-film lithium niobate of this invention can exceed 40dB, and the three-level intensity modulation can achieve an extinction ratio greater than 120dB, providing a good extinction ratio for vacuum state preparation in the TF-QKD protocol;

[0031] 4. In the phase modulation module of the present invention, due to the large electro-optic coefficient of thin-film lithium niobate, the power consumption and half-wave voltage (Vπ) of the integrated device are reduced; currently, the half-wave voltage of the phase modulator based on thin-film lithium niobate can be less than 1.5V, which can reduce the difficulty and cost of high-speed electronics design.

[0032] 5. The system of the present invention has low insertion loss, higher waveguide refractive index in the thin-film lithium niobate system, and a wide wavelength range covered by the transparent window, thereby reducing the transmission loss of light in the waveguide.

[0033] 6. The system of the present invention has high security. The monitoring module of the system can realize real-time security monitoring to prevent malicious external light from attacking the encoder chip, thereby further ensuring the security of the system.

[0034] 7. The third-party Charlie of this invention can realize polarization compensation and phase compensation, which can compensate for polarization disturbances and phase shifts caused by unstable external environment during photon transmission, improve the interference contrast of single photon interference, reduce the system bit error rate, and increase the security key rate. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0036] Figure 1 This is a structural diagram of a dual-field quantum key distribution system based on thin-film lithium niobate integration according to an embodiment of the present invention. Detailed Implementation

[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0040] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0041] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] Example 1

[0044] Reference Figure 1This is the first embodiment of the present invention, which provides a dual-field quantum key distribution system based on thin-film lithium niobate integration, comprising:

[0045] First fiber coupler 1, first intensity modulation module 2, second intensity modulation module 3, third intensity modulation module 4, phase modulation module 5, attenuation monitoring module 6, seventh beam splitter 7, second fiber coupler 8, third fiber coupler 9, first commercial fiber optic cable 10, fourth fiber coupler 11, first intensity modulation module 12, second intensity modulation module 13, third intensity modulation module 14, phase modulation module 15, attenuation monitoring module 16, fifteenth beam splitter 17, fifth fiber coupler 18, sixth fiber coupler 19, second commercial fiber optic cable 20, PC1 module 21, PC2 module 22, twenty-first thermally tunable phase shifter 23, twenty-second thermally tunable phase shifter 24, first single-photon detector 25, second single-photon detector Sub-detector 26, twenty-first beam splitter 27, third single-photon detector 28, 29, fourth single-photon detector, first beam splitter 201, second beam splitter 202, first thermally tunable phase shifter 203, first carrier dispersive phase shifter 204, second thermally tunable phase shifter 205, second carrier dispersive phase shifter 206, third beam splitter 301, fourth beam splitter 302, third thermally tunable phase shifter 303, third carrier dispersive phase shifter 304, fourth thermally tunable phase shifter 305, fourth carrier dispersive phase shifter 306, fifth beam splitter 401, sixth beam splitter 402, fifth thermally tunable phase shifter 403, fifth carrier dispersive phase shifter 404, sixth thermally tunable phase shifter 405, sixth... Carrier-dispersive phase shifter 406, seventh carrier-dispersive phase shifter 501, eighth carrier-dispersive phase shifter 502, ninth carrier-dispersive phase shifter 503, eighth beam splitter 601, first variable optical attenuator 602, first optical power detector 603, ninth beam splitter 1201, tenth beam splitter 1202, seventh thermally tunable phase shifter 1203, tenth carrier-dispersive phase shifter 1204, eighth thermally tunable phase shifter 1205, eleventh carrier-dispersive phase shifter 1206, eleventh beam splitter 1301, twelfth beam splitter 1302, ninth thermally tunable phase shifter 1303, twelfth carrier-dispersive phase shifter 1304, tenth thermally tunable phase shifter 1305, thirteenth carrier-dispersive phase shifter 13 ...5, thirteenth carrier-dispersive phase shifter 1306, thirteenth carrier-dispersive phase shifter 1305, thirteenth carrier-dispersive phase shifter Phase shifter 1306, eleventh beam splitter 1401, fourteenth beam splitter 1402, eleventh thermally tunable phase shifter 1403, fourteenth carrier dispersive phase shifter 1404, twelfth thermally tunable phase shifter 1405, fifteenth carrier dispersive phase shifter 1406, sixteenth carrier dispersive phase shifter 1501, seventeenth carrier dispersive phase shifter 1502, eighteenth carrier dispersive phase shifter 1503, sixteenth beam splitter 1601, second variable optical attenuator 1602, second optical power detector 1603, first polarization rotation beam splitter 2101, seventeenth beam splitter 2102, eighteenth beam splitter 2103, thirteenth thermally tunable phase shifter 2104, fourteenth thermally tunable phase shifter 2105.The fifteenth thermally tunable phase shifter 2106, the sixteenth thermally tunable phase shifter 2107, the second polarization rotating beam splitter 2201, the nineteenth beam splitter 2202, the twenty-first beam splitter 2203, the seventeenth thermally tunable phase shifter 2204, the eighteenth thermally tunable phase shifter 2205, the nineteenth thermally tunable phase shifter 2206, and the twentieth thermally tunable phase shifter 2207;

[0046] The communication user Alice includes: a first intensity modulation module 2, a second intensity modulation module 3, a third intensity modulation module 4, a phase modulation module 5, and an attenuation monitoring module 6; the communication user Bob includes: a first intensity modulation module 12, a second intensity modulation module 13, a third intensity modulation module 14, a phase modulation module 15, and an attenuation monitoring module 16; the third party Charlie includes: a PC1 module 21, a PC2 module 22, a twenty-first thermally tuned phase shifter 23, a twenty-second thermally tuned phase shifter 24, a first single-photon detector 25, a second single-photon detector 26, a twenty-first beam splitter 27, a third single-photon detector 28, and a fourth single-photon detector 29;

[0047] The first intensity modulation module 2 of the communication user Alice is connected to the second intensity modulation module 3, the second intensity modulation module 3 is connected to the third intensity modulation module 4, the third intensity modulation module 4 is connected to the phase modulation module 5, the phase modulation module 5 is connected to the attenuation monitoring module 6, the attenuation monitoring module 6 is connected to the third fiber coupler 9, the third fiber coupler 9 is connected to the PC1 module 21 of the third party Charlie through the first commercial fiber 10, the PC1 module 21 is connected to the first single-photon detector 25 and the twenty-first thermally tuned phase shifter 23 respectively, and the twenty-first thermally tuned phase shifter 23 is connected to the twenty-first beam splitter 27;

[0048] The first intensity modulation module 12 of the communication user Bob is connected to the second intensity modulation module 13, the second intensity modulation module 13 is connected to the third intensity modulation module 14, the third intensity modulation module 14 is connected to the phase modulation module 15, the phase modulation module 15 is connected to the attenuation monitoring module 16, the attenuation monitoring module 16 is connected to the sixth fiber coupler 19, the sixth fiber coupler 19 is connected to the PC2 module 22 of the third party Charlie through the second commercial fiber 20, the PC2 module 22 is connected to the second single-photon detector 26 and the twelfth thermally tuned phase shifter 24 respectively, the twelfth thermally tuned phase shifter 24 is connected to the eleventh beam splitter 27, and the eleventh beam splitter 27 is connected to the third single-photon detector 28 and the fourth single-photon detector 29 respectively;

[0049] The first intensity modulation module 2 of the communication user Alice includes: a first beam splitter 201 and a second beam splitter 202. Two optical arms are provided between the first beam splitter 201 and the second beam splitter 202. A first thermally tunable phase shifter 203 and a first carrier dispersive phase shifter 204 are connected in series on the first optical arm. A second thermally tunable phase shifter 205 and a second carrier dispersive phase shifter 206 are connected in series on the second optical arm. The first thermally tunable phase shifter 203 and the second thermally tunable phase shifter 205 are both connected to the first beam splitter 201, and the first carrier dispersive phase shifter 204 and the second carrier dispersive phase shifter 206 are both connected to the second beam splitter 202.

[0050] The second intensity modulation module 3 for communication user Alice includes: a third beam splitter 301 and a fourth beam splitter 302. Two optical arms are provided between the third beam splitter 301 and the fourth beam splitter 302. A third thermally tuned phase shifter 303 and a third carrier dispersive phase shifter 304 are connected in series on the first optical arm. A fourth thermally tuned phase shifter 305 and a fourth carrier dispersive phase shifter 306 are connected in series on the second optical arm. The third thermally tuned phase shifter 303 and the fourth thermally tuned phase shifter 305 are both connected to the third beam splitter 301, and the third carrier dispersive phase shifter 304 and the fourth carrier dispersive phase shifter 306 are both connected to the fourth beam splitter 302. The second beam splitter 202 is connected to the third beam splitter 301.

[0051] The third intensity modulation module 4 of the communication user Alice includes: a fifth beam splitter 401 and a sixth beam splitter 402. Two optical arms are provided between the fifth beam splitter 401 and the sixth beam splitter 402. A fifth thermally tuned phase shifter 403 and a fifth carrier dispersive phase shifter 404 are connected in series on the first optical arm. A sixth thermally tuned phase shifter 405 and a sixth carrier dispersive phase shifter 406 are connected in series on the second optical arm. The fifth thermally tuned phase shifter 403 and the sixth thermally tuned phase shifter 405 are both connected to the fifth beam splitter 401. The fifth carrier dispersive phase shifter 404 and the sixth carrier dispersive phase shifter 406 are both connected to the sixth beam splitter 402. A fourth beam splitter 302 is connected to the fifth beam splitter 401.

[0052] The phase modulation module 5 for communication user Alice includes: a seventh carrier dispersive phase shifter 501, an eighth carrier dispersive phase shifter 502, and a ninth carrier dispersive phase shifter 503. The seventh carrier dispersive phase shifter 501 is connected to the eighth carrier dispersive phase shifter 502, and the eighth carrier dispersive phase shifter 502 is connected to the ninth carrier dispersive phase shifter 503. The seventh carrier dispersive phase shifter 501 is connected to the sixth beam splitter 402, and the ninth carrier dispersive phase shifter 503 is connected to the seventh beam splitter 7.

[0053] The attenuation monitoring module 6 for communication user Alice includes: an eighth beam splitter 601, a first variable optical attenuator 602, and a first optical power detector 603. The eighth beam splitter 601 is connected to the first variable optical attenuator 602 and the first optical power detector 603, respectively. The first variable optical attenuator 602 is connected to the seventh beam splitter 7. The eighth beam splitter 601 is also connected to a second fiber optic coupler 8 and a third fiber optic coupler 9.

[0054] PC1 module 21 includes: a first polarization rotating beam splitter 2101, a seventeenth beam splitter 2102, and an eighteenth beam splitter 2103. Two optical arms are provided between the first polarization rotating beam splitter 2101 and the seventeenth beam splitter 2102. A thirteenth thermally tunable phase shifter 2104 is provided on the first optical arm, and a fourteenth thermally tunable phase shifter 2105 is provided on the second optical arm. Two optical arms are provided between the seventeenth beam splitter 2102 and the eighteenth beam splitter 2103. A fifteenth thermally tunable phase shifter 2106 is provided on the first optical arm, and a sixteenth thermally tunable phase shifter 2107 is provided on the second optical arm. The first polarization rotating beam splitter 2101 is connected to a third fiber coupler 9 via a first commercial optical fiber 10.

[0055] The eighteenth beam splitter 2103 is connected to the twenty-first thermally tuned phase shifter 23 and the first single-photon detector 25, respectively.

[0056] The first intensity modulation module 12 for communication user Bob includes a ninth beam splitter 1201 and a tenth beam splitter 1202. Two optical arms are provided between the ninth beam splitter 1201 and the tenth beam splitter 1202. A seventh thermally tunable phase shifter 1203 and a tenth carrier dispersive phase shifter 1204 are connected in series on the first optical arm. An eighth thermally tunable phase shifter 1205 and an eleventh carrier dispersive phase shifter 1206 are connected in series on the second optical arm. The seventh thermally tunable phase shifter 1203 and the eighth thermally tunable phase shifter 1205 are both connected to the ninth beam splitter 1201, and the tenth carrier dispersive phase shifter 1204 and the eleventh carrier dispersive phase shifter 1206 are both connected to the tenth beam splitter 1202. The ninth beam splitter 1201 is connected to a fourth fiber coupler 11.

[0057] The second intensity modulation module 13 for communication user Bob includes an eleventh beamsplitter 1301 and a twelfth beamsplitter 1302. Two optical arms are provided between the eleventh and twelfth beamsplitters 1301 and 1302. A ninth thermally tuned phase shifter 1303 and a twelfth carrier dispersive phase shifter 1304 are connected in series on the first optical arm. A tenth thermally tuned phase shifter 1305 and a thirteenth carrier dispersive phase shifter 1306 are connected in series on the second optical arm. The ninth and tenth thermally tuned phase shifters 1303 and 1305 are both connected to the eleventh beamsplitter 1301, and the twelfth and thirteenth carrier dispersive phase shifters 1304 and 1306 are both connected to the twelfth beamsplitter 1302. The tenth beamsplitter 1202 is connected to the eleventh beamsplitter 1301.

[0058] The third intensity modulation module 14 for communication user Bob includes a 13th beam splitter 1401 and a 14th beam splitter 1402. Two optical arms are provided between the 13th beam splitter 1401 and the 14th beam splitter 1402. An 11th thermally tuned phase shifter 1403 and a 14th carrier dispersive phase shifter 1404 are connected in series on the first optical arm. A 12th thermally tuned phase shifter 1405 and a 15th carrier dispersive phase shifter 1406 are connected in series on the second optical arm. The 11th and 12th thermally tuned phase shifters 1403 and 1405 are both connected to the 13th beam splitter 1401. The 14th and 15th carrier dispersive phase shifters 1404 and 1406 are both connected to the 14th beam splitter 1402. The 12th beam splitter 1302 is connected to the 13th beam splitter 1401.

[0059] The phase modulation module 15 for communication user Bob includes a sixteenth carrier dispersive phase shifter 1501, a seventeenth carrier dispersive phase shifter 1502, and an eighteenth carrier dispersive phase shifter 1503; the sixteenth carrier dispersive phase shifter 1501 is connected to the seventeenth carrier dispersive phase shifter 1502, and the seventeenth carrier dispersive phase shifter 1502 is connected to the eighteenth carrier dispersive phase shifter 1503; the sixteenth carrier dispersive phase shifter 1501 is connected to the fourteenth beam splitter 1402, and the eighteenth carrier dispersive phase shifter 1503 is connected to the fifteenth beam splitter 17;

[0060] The attenuation monitoring module 16 for communication user Bob includes: a sixteenth beam splitter 1601, a second variable optical attenuator 1602, and a second optical power detector 1603. The sixteenth beam splitter 1601 is connected to the second variable optical attenuator 1602 and the second optical power detector 1603, respectively. The second variable optical attenuator 1602 is connected to the fifteenth beam splitter 17. A fifth fiber coupler 18 and a sixth fiber coupler 19 are connected to the sixteenth beam splitter 1601, respectively.

[0061] PC2 module 22 includes: a second polarization rotating beam splitter 2201, a nineteenth beam splitter 2202, and a twenty-tenth beam splitter 2203. Two optical arms are provided between the second polarization rotating beam splitter 2201 and the nineteenth beam splitter 2202. A seventeenth thermally tunable phase shifter 2204 is provided on the first optical arm, and an eighteenth thermally tunable phase shifter 2205 is provided on the second optical arm. Two optical arms are provided between the nineteenth beam splitter 2202 and the twenty-tenth beam splitter 2203. A nineteenth thermally tunable phase shifter 2206 is provided on the first optical arm, and a twentieth thermally tunable phase shifter 2207 is provided on the second optical arm. The second polarization rotating beam splitter 2201 is connected to a sixth fiber coupler 19 via commercial optical fiber 20.

[0062] The second beam splitter 2203 is connected to the second twelfth thermally tuned phase shifter 24 and the second single-photon detector 26, respectively.

[0063] Example 2

[0064] Referring to the following steps, this is the second embodiment of the present invention. This embodiment provides a dual-field quantum key distribution system based on thin-film lithium niobate integration, including: encoding the quantum states of the integrated dual-field quantum key distribution communication users Alice and Bob, and decoding the quantum states of the third party Charlie.

[0065] S1. The continuous light emitted by the external laser of the Alice chip of the communication user is coupled into the waveguide through the first fiber coupler 1, and then modulates the thermally tuned phase shifter of each intensity modulation module to maximize the output light intensity and compensate for the initial phase difference caused by the waveguide and other devices.

[0066] Similarly, the continuous light emitted by the external laser of the Bob chip in the communication user is coupled into the waveguide through the first fiber coupler 11, and then modulated by the thermally tuned phase shifter of each intensity modulation module to maximize the output light intensity and compensate for the initial phase difference caused by the waveguide and other devices.

[0067] S2. The continuous light emitted by the external laser of the communication user Alice chip is coupled into the waveguide through the first fiber coupler 1, and then modulated into pulse light by the first intensity modulation module 2 by adjusting the phase difference between the first carrier dispersive phase shifter 204 and the second carrier dispersive phase shifter 206 to 0 or π.

[0068] Similarly, the continuous light emitted by the external laser of the Bob chip of the communication user is coupled into the waveguide through the first fiber coupler 11, and then modulated into pulse light by the first intensity modulation module 12 by adjusting the phase difference between the tenth carrier dispersive phase shifter 1204 and the eleventh carrier dispersive phase shifter 1206 to 0 or π.

[0069] S3. The pulsed light modulated by the first intensity modulation module 2 at the Alice end enters the second intensity modulation module 3 and the third intensity modulation module 4 for decoy state intensity modulation. By adjusting the phase difference between the third carrier dispersive phase shifter 304 and the fourth carrier dispersive phase shifter 306, and the phase difference between the fifth carrier dispersive phase shifter 404 and the sixth carrier dispersive phase shifter 406, the intensity of the signal state and the decoy state is made to meet the experimental requirements.

[0070] Similarly, the pulsed light modulated by the first intensity modulation module 12 at the Bob end enters the second intensity modulation module 13 and the third intensity modulation module 14 for decoy state intensity modulation. By adjusting the phase difference between the twelfth carrier dispersive phase shifter 1304 and the thirteenth carrier dispersive phase shifter 1306, and the phase difference between the fourteenth carrier dispersive phase shifter 1404 and the fifteenth carrier dispersive phase shifter 1406, the intensity of the signal state and the decoy state is made to meet the experimental requirements.

[0071] S4. After intensity modulation of the signal state and decoy state is completed at the Alice end, the pulsed light enters the phase modulation module 5 for phase modulation, realizing... 16 phase adjustments;

[0072] Similarly, after intensity modulation of the signal state and decoy state is completed at the Bob end, the pulsed light enters the phase modulation module 15 for phase modulation, realizing... 16 phase adjustments;

[0073] S5. At the Alice end, the pulse light output by the phase modulation module 5 is attenuated to the single photon level by the first variable optical attenuator 602 in the attenuation monitoring module 6 and then output by the eighth beam splitter 601. The laser outside the chip enters the chip through the third fiber coupler 9 and is transmitted to the PC1 module 21 through the first commercial fiber optic cable 10.

[0074] Similarly, at the Bob end, the pulse light output from the phase modulation module 15 is attenuated to the single-photon level by the second variable optical attenuator 1602 in the attenuation monitoring module 16 and then output by the sixteenth beam splitter 1601. The laser outside the chip enters the chip through the sixth fiber coupler 19 and is transmitted to the PC2 module 22 through the second commercial fiber optic cable 20.

[0075] S6. The light transmitted to the PC1 module 21 through the first commercial optical fiber 10 is split into two beams by the first polarization rotating beam splitter 2101. By adjusting the thirteenth thermally tuned phase shifter 2104 and the fourteenth thermally tuned phase shifter 2105, as well as the fifteenth thermally tuned phase shifter 2106 and the sixteenth thermally tuned phase shifter 2107, all photons are output from the lower arm of the beam splitter 2103, thus completing the polarization state compensation.

[0076] Similarly, the light transmitted to the PC2 module 22 through the second commercial optical fiber 20 is split into two beams by the second polarization rotating beam splitter 2102. By adjusting the seventeenth thermally tuned phase shifter 2204, the eighteenth thermally tuned phase shifter 2205, the nineteenth thermally tuned phase shifter 2206, and the twentieth thermally tuned phase shifter 2207, all photons are output from the lower arm of the beam splitter 2203, thus completing the polarization state compensation.

[0077] S7. Finally, after phase compensation is completed by adjusting the twenty-first thermally tuned phase shifter 23 and the twenty-second thermally tuned phase shifter 24, the phase is fed into the twenty-first beam splitter 27 for interference and recorded by the third single-photon detector 28 and the fourth single-photon detector 29.

[0078] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0079] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0080] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0081] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0082] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0083] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A dual-field quantum key distribution system based on thin-film lithium niobate integration, characterized in that, include: The system architecture for both communication users Alice and Bob includes a first intensity modulation module, a second intensity modulation module, a third intensity modulation module, a phase modulation module, and an attenuation monitoring module connected in sequence. The third-party Charlie includes the PC1 module, the PC2 module, the twenty-first thermally tuned phase shifter, the twenty-second thermally tuned phase shifter, the first single-photon detector, the second single-photon detector, the twenty-first beam splitter, the third single-photon detector, and the fourth single-photon detector; The first intensity modulation module of the communication user Alice is connected to the second intensity modulation module, the second intensity modulation module is connected to the third intensity modulation module, the third intensity modulation module is connected to the phase modulation module, the phase modulation module is connected to the attenuation monitoring module, the attenuation monitoring module is connected to the third fiber coupler, the third fiber coupler is connected to the PC1 module of the third party Charlie through the first commercial fiber, the PC1 module is connected to the first single-photon detector and the twenty-first thermally tunable phase shifter, and the twenty-first thermally tunable phase shifter is connected to the twenty-first beam splitter; the first intensity modulation module of the communication user Bob is connected to the second intensity modulation module. The control module is connected to the second intensity modulation module, the second intensity modulation module is connected to the third intensity modulation module, the third intensity modulation module is connected to the phase modulation module, the phase modulation module is connected to the attenuation monitoring module, the attenuation monitoring module is connected to the sixth fiber coupler, the sixth fiber coupler is connected to the third-party Charlie's PC2 module through the second commercial fiber, the PC2 module is connected to the second single-photon detector and the twenty-twelfth thermally tuned phase shifter respectively, the twenty-twelfth thermally tuned phase shifter is connected to the twenty-first beam splitter, and the twenty-first beam splitter is connected to the third single-photon detector and the fourth single-photon detector respectively; The two communicating users, Alice and Bob, as well as the third party Charlie, are all integrated on a thin-film lithium niobate material platform.

2. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in claim 1, characterized in that, The first intensity modulation module of the communication user Alice includes: a first beam splitter and a second beam splitter; Two optical arms are provided between the first beam splitter and the second beam splitter. A first thermally tunable phase shifter and a first carrier dispersive phase shifter are connected in series on the first optical arm, and a second thermally tunable phase shifter and a second carrier dispersive phase shifter are connected in series on the second optical arm. The first thermally tunable phase shifter and the second thermally tunable phase shifter are both connected to the first beam splitter, and the first carrier dispersive phase shifter and the second carrier dispersive phase shifter are both connected to the second beam splitter. The first beam splitter is connected to a first optical fiber coupler.

3. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in claim 2, characterized in that, The second intensity modulation module of the communication user Alice includes: a third beam splitter and a fourth beam splitter; Two optical arms are provided between the third and fourth beam splitters. A third thermally tunable phase shifter and a third carrier dispersive phase shifter are connected in series on the first optical arm, and a fourth thermally tunable phase shifter and a fourth carrier dispersive phase shifter are connected in series on the second optical arm. Both the third and fourth thermally tunable phase shifters are connected to the third beam splitter, and both the third and fourth carrier dispersive phase shifters are connected to the fourth beam splitter. The second beam splitter is connected to the third beam splitter.

4. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in claim 3, characterized in that, The third intensity modulation module of the communication user Alice includes: a fifth beam splitter and a sixth beam splitter; Two optical arms are provided between the fifth and sixth beam splitters. A fifth thermally tunable phase shifter and a fifth carrier dispersive phase shifter are connected in series on the first optical arm, and a sixth thermally tunable phase shifter and a sixth carrier dispersive phase shifter are connected in series on the second optical arm. Both the fifth and sixth thermally tunable phase shifters are connected to the fifth beam splitter, and both the fifth and sixth carrier dispersive phase shifters are connected to the sixth beam splitter. The fourth beam splitter is connected to the fifth beam splitter.

5. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in claim 4, characterized in that, The phase modulation module of the communication user Alice includes: a seventh carrier dispersive phase shifter, an eighth carrier dispersive phase shifter, and a ninth carrier dispersive phase shifter; The seventh carrier dispersive phase shifter is connected to the eighth carrier dispersive phase shifter, and the eighth carrier dispersive phase shifter is connected to the ninth carrier dispersive phase shifter; the seventh carrier dispersive phase shifter is connected to the sixth beam splitter, and the ninth carrier dispersive phase shifter is connected to the seventh beam splitter.

6. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in claim 5, characterized in that, The attenuation monitoring module for the communication user Alice includes: an eighth beam splitter, a first variable optical attenuator, and a first optical power detector; The eighth beam splitter is connected to the first variable optical attenuator and the first optical power detector, respectively. The first variable optical attenuator is connected to the seventh beam splitter. The eighth beam splitter is also connected to the second fiber coupler and the third fiber coupler, respectively.

7. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in claim 1, characterized in that, The third-party Charlie PC1 module includes: a first polarization rotating beam splitter, a seventeenth beam splitter, and an eighteenth beam splitter; Two optical arms are provided between the first polarization rotating beam splitter and the seventeenth beam splitter. A thirteenth thermally tunable phase shifter is provided on the first optical arm, and a fourteenth thermally tunable phase shifter is provided on the second optical arm. Two optical arms are provided between the seventeenth and eighteenth beam splitters. A fifteenth thermally tunable phase shifter is provided on the first optical arm, and a sixteenth thermally tunable phase shifter is provided on the second optical arm. The first polarization rotating beam splitter is connected to a third fiber coupler via a first commercial fiber. The eighteenth beam splitter is connected to the twenty-first thermally tunable phase shifter and the first single-photon detector, respectively.

8. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in claim 1, characterized in that, include: Second polarization rotating beam splitter, nineteenth beam splitter, and twentieth beam splitter; Two optical arms are provided between the second polarization rotating beamsplitter and the nineteenth beamsplitter. A seventeenth thermally tunable phase shifter is provided on the first optical arm, and an eighteenth thermally tunable phase shifter is provided on the second optical arm. Two optical arms are provided between the nineteenth beamsplitter and the twentyth beamsplitter. A nineteenth thermally tunable phase shifter is provided on the first optical arm, and a twentieth thermally tunable phase shifter is provided on the second optical arm. The second polarization rotating beamsplitter is connected to a sixth fiber coupler via a second commercial fiber. The second beamsplitter is connected to a twenty-second thermally tunable phase shifter and a second single-photon detector, respectively.

9. The dual-field quantum key distribution system based on thin-film lithium niobate integration as described in any one of claims 1 to 8, characterized in that, The two communicating users, Alice and Bob, as well as the third party Charlie, are all integrated on a thin-film lithium niobate material platform, including: all connections are made via lithium niobate optical waveguides.

Images