Quantum interference based geographically distributed multi-node network signal synchronization apparatus

Abstract

This application discloses a multi-node network signal synchronization device based on quantum interference, comprising: an optical frequency comb generation module, a filtering module, and an adjustment module deployed locally at each node, and an interference module deployed outside the nodes; the optical frequency comb generation modules of any two nodes performing signal synchronization are used to generate independent optical frequency combs locally at each node, wherein the optical frequency combs achieve frequency alignment by locking the pump laser frequency with the repetition frequency of the optical frequency comb; the filtering module is used to filter out the same-frequency comb teeth assigned to any two nodes from their respective optical frequency combs; the interference module is used to perform beam interference on the same-frequency comb teeth of any two nodes and send the relative time deviation between the optical signals of any two nodes to the adjustment module of the target node among the two nodes; the adjustment module is used to adjust according to the relative time deviation. This application solves the problems of single point of failure and poor network topology flexibility in star network architecture.

Description

Technical Field

[0001] This application relates to the fields of quantum information technology and precision measurement technology, and in particular to a remote multi-node network signal synchronization device based on quantum interference. Background Technology

[0002] High-precision signal synchronization is a key foundational technology supporting the reliable operation of modern information networks (such as communication, navigation, distributed sensing, and computing). In the field of quantum information technology, cutting-edge applications such as distributed quantum computing, quantum sensor networks, and multi-user quantum secure communication all require extremely high-precision synchronization between multiple nodes distributed within the network.

[0003] Currently, a star-shaped network architecture is commonly used to share a quantum source to achieve high-precision synchronization between quantum network nodes. However, this network architecture requires a central node, and synchronization between all nodes must be relayed through the central node. This increases the dependence on the central node, resulting in poor topological flexibility of the quantum network. Furthermore, it also suffers from a single point of failure problem, meaning that if the central node fails, the entire quantum network will be paralyzed. Summary of the Invention

[0004] In view of this, this application provides a multi-node network signal synchronization device based on quantum interference, which mainly solves the problems of single point of failure and poor network topology flexibility in the existing star network architecture.

[0005] This application provides a multi-node network signal synchronization device based on quantum interference. The device includes: an optical frequency comb generation module, a filtering module, and an adjustment module deployed locally at each node, and an interference module deployed outside the node. The optical frequency comb generation module and the filtering module of each node are respectively connected to the input end of the interference module, and the output end of the interference module is connected to the adjustment module of each node. The optical frequency comb generation module of any two nodes that perform signal synchronization is used to generate independent optical frequency combs locally on the node. The optical frequency combs are frequency aligned by locking the pump laser frequency and the repetition frequency of the optical frequency comb. The filtering modules of any two nodes are respectively used to filter out the same frequency comb teeth allocated to the two nodes from their respective optical frequency combs; The interference module is used to perform beam interferometry on the same frequency combs of any two nodes, and determine the relative time deviation between the optical signals of any two nodes through interferometric measurement; and send the relative time deviation to the adjustment module of the target node among the two nodes. The adjustment module of the target node is used to adjust the local clock phase or optical path delay according to the relative time deviation in order to achieve signal synchronization.

[0006] Optionally, the device further includes: an output detection module deployed locally at each node, wherein the optical frequency comb generation module, the output detection module, and the filtering processing module of each node are connected in sequence; The output detection modules of any two nodes are respectively used to filter out the pump laser and the auxiliary laser from their respective optical frequency combs to obtain the processed optical frequency combs; The filtering modules of any two nodes are respectively used to filter out the same frequency comb teeth assigned to the two nodes from their respective processed optical frequency combs.

[0007] Optionally, the optical frequency comb generation module corresponding to each node includes: an optical frequency comb frequency locking submodule and an optical frequency comb generation submodule, wherein the output end of the optical frequency comb frequency locking submodule is connected to the input end of the optical frequency comb generation submodule, and the output end of the optical frequency comb generation submodule is connected to the filtering processing module; The frequency locking submodules of any two nodes are used to lock the repetition frequency of the pump laser and the optical frequency comb, respectively. The optical frequency comb generation submodules of any two nodes are respectively used to generate the optical frequency comb through an auxiliary laser heating scheme.

[0008] Optionally, the optical frequency comb frequency locking submodule includes: a first tunable laser, an acousto-optic modulator, a first fiber coupler, a Fabry-Perot cavity, an acetylene gas chamber, a photodetector, and a servo connected in sequence. The output terminal of the servo is connected to the input terminal of the first tunable laser and the input terminal of a voltage-controlled oscillator, respectively. The output terminal of the voltage-controlled oscillator is connected to the input terminal of the acousto-optic modulator. The output terminal of the first fiber coupler and the output terminal of a microwave signal generator are connected to the input terminal of an electro-optic modulator, respectively. The output terminal of the electro-optic modulator is connected to the optical frequency comb generation submodule.

[0009] Optionally, the optical frequency comb generation submodule includes: a second tunable laser, a first polarization controller, a first erbium-doped fiber amplifier, a first fiber circulator, and an optical microcavity connected in sequence. The output end of the first fiber circulator is connected to the output detection module, the input end of the optical microcavity is connected to the output end of the second fiber circulator, the input end of the second fiber circulator is connected to the output end of the second erbium-doped fiber amplifier, the input end of the second erbium-doped fiber amplifier is connected to the output end of the second polarization controller, and the input end of the second polarization controller is connected to the output end of the optical frequency comb frequency locking submodule. The pump laser output from the optical frequency comb frequency locking submodule and the auxiliary laser generated by the second tunable laser are coupled into the optical microcavity to generate the optical frequency comb.

[0010] Optionally, the output detection module corresponding to each node includes: a second fiber coupler, a first dense wavelength division multiplexer, a second dense wavelength division multiplexer, and a third fiber coupler connected in sequence. The output end of the second fiber coupler is connected to a spectrometer, and the output end of the third fiber coupler is connected to a power meter and the filtering module, respectively. The spectrometer is used to monitor the spectrum of the optical frequency comb. The first dense wavelength division multiplexer and the second dense wavelength division multiplexer are used to filter out the pump laser and the auxiliary laser from the optical frequency comb, respectively.

[0011] Optionally, the filtering module corresponding to each node includes: a filtering submodule, an encoding submodule, and a polarization control submodule connected in sequence, wherein the input end of the filtering submodule is connected to the output end of the output detection module, and the output end of the polarization control submodule is connected to the input end of the interference module; The filtering submodules of any two nodes are respectively used to filter out the same frequency comb teeth assigned to the two nodes from the processed optical frequency comb; The encoding submodules of any two nodes are respectively used to load quantum information into the same frequency comb teeth to obtain the same frequency comb teeth after quantum information loading; The polarization control submodules of any two nodes are respectively used to attenuate the light intensity of the same frequency comb after the quantum information is loaded to the weak coherence state level, adjust the delay of the two photons through the adjustable delay line, and adjust the polarization of the two photons to be consistent through the polarization maintaining beam splitter. The interference module is used to perform beam interferometry on the attenuated co-frequency combs of any two nodes, and determine the relative time deviation between the optical signals of any two nodes through interferometric measurement; and send the relative time deviation to the adjustment module of the target node among the two nodes.

[0012] Optionally, the filtering submodule includes: a programmable optical filter and a third polarization controller connected together, wherein the input terminal of the programmable optical filter is connected to the output terminal of the output detection module, and the output terminal of the third polarization controller is connected to the input terminal of the encoding submodule.

[0013] Optionally, the encoding submodule includes an intensity modulator and an arbitrary waveform generator, wherein the optical signal input terminal of the intensity modulator is connected to the output terminal of the filtering submodule, the radio frequency signal input terminal of the intensity modulator is connected to the output terminal of the arbitrary waveform generator, and the optical signal output terminal of the intensity modulator is connected to the polarization control submodule.

[0014] Optionally, the polarization control submodule includes: an adjustable delay line, an adjustable optical attenuator, and a polarization beam splitter connected in sequence.

[0015] Optionally, the interference module includes: an interference submodule, a detection submodule, and a signal processing submodule connected in sequence; The interference submodule is used to perform beam-combining interference on the same frequency comb teeth of any two nodes to obtain a combined photon; The detection submodule is used to perform coincidence count measurement on the combined photons to obtain interference fringes and locate the coincidence count minimum point. Based on the interference fringes and the coincidence count minimum point, the relative time deviation between any two node optical signals is calculated. The signal processing submodule is used to convert the relative time deviation into an error control signal and feed the error control signal back to the adjustment module of the target node; The adjustment module of the target node is used to adjust the local clock phase or optical path delay according to the error control signal to achieve signal synchronization.

[0016] Optionally, the interference submodule includes a polarization-maintaining beam splitter, the input of which is connected to the filtering module.

[0017] Optionally, the detection submodule includes: a fourth polarization controller, a fifth polarization controller, a first superconducting nanowire single-photon detector, a second superconducting nanowire single-photon detector, and a time-to-digital converter. The input terminals of the fourth polarization controller and the fifth polarization controller are respectively connected to the output terminals of the interference submodule. The output terminal of the fourth polarization controller is connected to the input terminal of the first superconducting nanowire single-photon detector, and the output terminal of the fifth polarization controller is connected to the input terminal of the second superconducting nanowire single-photon detector. The output terminals of the first superconducting nanowire single-photon detector and the second superconducting nanowire single-photon detector are respectively connected to the time-to-digital converter.

[0018] By employing the above technical solutions, this application provides a multi-node network signal synchronization device based on quantum interference. Compared with existing technologies, by deploying an optical frequency comb generation module, a filtering module, and an adjustment module locally on each node, and deploying an interference module outside the node, it is possible to configure an independent light source for each node. At the same time, by utilizing the inherent multi-wavelength characteristics of the optical frequency comb, it is possible to allocate exclusive communication wavelengths for communication between different node pairs, i.e., co-frequency comb teeth, thereby realizing a decentralized synchronization architecture. In this application, synchronization can be directly established between any two nodes without the need for relay through a central node. Therefore, the network topology is more flexible, and it also solves the single point of failure problem of star network architecture.

[0019] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This paper presents a simplified structural diagram of a multi-node network signal synchronization device based on quantum interference, according to an embodiment of this application. Figure 2 The network architecture diagram of the remote multi-node network signal synchronization device based on quantum interference provided in the embodiments of this application is shown. Figure 3 This paper shows a schematic diagram of the structure of a multi-node network signal synchronization device based on quantum interference provided in an embodiment of this application. Figure 4 A detailed structural schematic diagram of the multi-node network signal synchronization device based on quantum interference provided in this application embodiment is shown. Figure 5 This paper illustrates a specific implementation structure diagram of the quantum interference-based remote multi-node network signal synchronization device provided in an embodiment of this application. Figure 6 A schematic diagram of the off-site optical frequency comb spectrum provided in an embodiment of this application is shown; Figure 7 A schematic diagram of the HOM interference fringe pattern of the third comb tooth provided in an embodiment of this application is shown. Detailed Implementation

[0021] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0022] The existing star network architecture suffers from single point of failure and poor network topology flexibility.

[0023] To address the aforementioned problems, this invention provides a remote multi-node network signal synchronization device based on quantum interference, such as... Figure 1As shown, the device includes: an optical frequency comb generation module, a filtering module, and an adjustment module deployed locally at each node; and an interference module deployed outside the nodes. The optical frequency comb generation module and filtering module of each node are each connected to the input of the interference module, and the output of the interference module is connected to the adjustment module of each node. The optical frequency comb generation modules of any two nodes performing signal synchronization are each used to generate independent optical frequency combs locally at each node. The optical frequency combs achieve frequency alignment by locking the pump laser frequency to the repetition frequency of the optical frequency comb. The filtering modules of the two nodes are each used to filter out comb teeth of the same frequency assigned to the two nodes from their respective optical frequency combs. The interference module is used to perform beam interferometry on the comb teeth of the two nodes and determine the relative time deviation between the optical signals of the two nodes through interferometry. The relative time deviation is sent to the adjustment module of the target node among the two nodes. The adjustment module of the target node is used to adjust the local clock phase or optical path delay according to the relative time deviation to achieve signal synchronization.

[0024] In this embodiment of the invention, the number of nodes in the quantum network is at least two, and any two nodes can be synchronized.

[0025] Specifically, the quantum interference-based remote multi-node network signal synchronization device of this invention deploys an optical frequency comb generation module, a filtering module, and an adjustment module locally on each node, while deploying an interference module externally to each node. This design architecture equips each node with an independent and frequency-aligned optical frequency comb, as well as an independent encoder, thereby enabling signal synchronization between any two nodes. Figure 2 As shown, the codes are 1, 2, 3, Representing comb teeth, the same code indicates that different nodes use the corresponding comb teeth for signal synchronization. For example... Figure 2 As shown, each node only needs 5 comb teeth to achieve signal synchronization between 6 nodes. For example, nodes A and B can use comb tooth 1 for signal synchronization, and nodes A and F can use comb tooth 5 for signal synchronization. To achieve signal synchronization between any two nodes, this embodiment of the invention pre-assigns at least one pair of same-frequency comb teeth to any two nodes. For example, to synchronize nodes A and B, comb tooth 1 is pre-assigned to nodes A and B. Then, the filtering module uses a programmable filter to filter out the assigned same-frequency comb teeth from the optical frequency combs of nodes A and B respectively, so as to achieve signal synchronization.

[0026] It should be noted that the synchronization device in this embodiment of the invention utilizes the multi-wavelength parallel processing capability of the optical frequency comb, enabling it to support parallel synchronization operations of multiple node pairs. The system capacity expands linearly with the number of wavelengths. Figure 1The device structure of this embodiment is illustrated using only one node pair (node ​​A and node B) as an example.

[0027] The core of this invention lies in using frequency-aligned independent optical frequency combs as carriers for multi-wavelength parallel synchronization, using interferometric measurement results as ultra-sensitive time deviation probes, and combining feedback control to construct a distributed, precision synchronization architecture based on the principle of quantum interference.

[0028] In some embodiments, such as Figure 3 As shown, the device further includes: an output detection module deployed locally at each node, wherein the optical frequency comb generation module, output detection module, and filtering processing module of each node are connected in sequence; the output detection modules of any two nodes are respectively used to filter out the pump laser and auxiliary laser from their respective optical frequency combs to obtain the processed optical frequency comb; the filtering processing modules of any two nodes are respectively used to filter out the same frequency comb teeth allocated to the any two nodes from their respective processed optical frequency combs.

[0029] The following uses any two nodes ( Figure 2 Taking nodes A and B as examples, we can illustrate the generation and frequency alignment process of the optical frequency comb at each node, as well as the signal synchronization process between different nodes.

[0030] like Figure 4 As shown, the optical frequency comb generation module corresponding to each node includes: an optical frequency comb frequency locking submodule and an optical frequency comb generation submodule. The output end of the optical frequency comb frequency locking submodule is connected to the input end of the optical frequency comb generation submodule, and the output end of the optical frequency comb generation submodule is connected to the filtering processing module. The optical frequency comb frequency locking submodules of any two nodes are used to lock the repetition frequency of the pump laser and the optical frequency comb, respectively. The optical frequency comb generation submodules of any two nodes are used to generate the optical frequency comb through an auxiliary laser heating scheme.

[0031] Specifically, the output of the optical frequency comb generation submodule is connected to the input of the detection module, and the output of the detection module is connected to the input of the filtering module. The optical frequency comb generation submodule uses an auxiliary laser heating method to configure an independent optical frequency comb source for each node in the network. The optical frequency comb frequency locking submodule can achieve precise frequency alignment between the optical frequency combs of all nodes by dual-free locking of the pump laser frequency and the optical frequency comb repetition frequency.

[0032] The optical frequency comb frequency locking submodules deployed locally on Node A and Node B have the same structure and working principle, such as... Figure 5As shown, the optical frequency comb frequency locking submodule includes: a first tunable laser 201, 501; an acousto-optic modulator (AOM) 202, 502; a first fiber coupler 203, 503; a Fabry-Perot cavity (FP cavity) 204, 504; an acetylene gas chamber (C2H2) 205, 505; a photodetector (PD) 206, 506; and a servo 207, 507, connected in sequence. The output terminals of the servos 207, 507 are respectively connected to the first tunable laser... The input terminals of lasers 201 and 501 are connected to the input terminals of voltage-controlled oscillators (VCOs) 208 and 508. The output terminals of VCOs 208 and 508 are connected to the input terminals of acousto-optic modulators 202 and 502. The output terminals of the first fiber couplers 203 and 503 and the output terminals of microwave signal generators (RFs) 210 and 510 are respectively connected to the input terminals of electro-optic modulators (EOMs) 209 and 509. The output terminals of electro-optic modulators 209 and 509 are connected to the optical frequency comb generation submodule.

[0033] Specifically, the pump laser output from the first tunable lasers 201 and 501 is frequency-shifted by the acousto-optic modulators 202 and 205. The frequency shift amount is determined according to the frequency set by the voltage-controlled oscillator 208 and 508. In this embodiment of the invention, the frequency shift amount is preferably set to 185Hz. Then, it is split into two paths by the first fiber coupler 203 and 503. One path is transmitted to the Fabry-Perot cavity (FP cavity) 204 and 504. The reflected light after resonance in the cavity is input to the acetylene gas chamber (C2H2) 205 and 505. The transmitted light from the acetylene gas chamber (C2H2) 205 and 505 is output to the photodetector (PD) 206 and 506 and converted into an electrical signal. The servo units 207 and 507 output a control voltage according to the electrical signal to drive the voltage-controlled oscillator 208 and 508 to generate a radio frequency signal, which is fed back to the acousto-optic modulator 202 and 502 for frequency modulation. The other input from the branch of the first fiber coupler 203, 503 is modulated by electro-optic modulators (EOMs) 209, 509. The modulated pump laser is then input to the optical frequency comb generation submodule. In this embodiment of the invention, the microwave drive signal of the electro-optic modulators 209, 509 is set with reference to the high-stability clock source RF (microwave signal generator) 210, 510 of the satellite communication signal. Preferably, the frequency of the microwave signal is set to 12.5Hz. Through modulation, the frequency difference between the fourth-order sideband and the pump laser can be made approximately 50 GHz, which is consistent with the repetition frequency of the optical frequency comb. In this embodiment of the invention, by carefully adjusting the microwave frequency and power, the soliton repetition frequency can be automatically locked.

[0034] The optical frequency comb frequency locking submodule of this invention locks to the FP cavity and acetylene gas chamber through PDH frequency locking technology, which can lock the pump frequency of the two locations. By injecting a microwave source into the electro-optic modulator to modulate the fourth-order sideband, the repetition frequency can be locked. The above-mentioned dual-degree-of-freedom locking of the pump laser frequency and the optical frequency comb repetition frequency can achieve precise frequency alignment between all node optical frequency combs, thereby establishing a basis for frequency indistinguishability for subsequent interference.

[0035] The optical frequency comb generation submodules deployed locally on nodes A and B have identical structures and operating principles, such as... Figure 5 As shown, the optical frequency comb generation submodule includes: a second tunable laser 101, 401, a first polarization controller 102, 402, a first erbium-doped fiber amplifier (EDFA) 103, 403, a first fiber optic circulator (CIR) 104, 404, and an optical microcavity 105, 405 connected in sequence. The output terminals of the first fiber optic circulator 104, 404 are connected to the output detection module, and the input terminals of the optical microcavities 105, 405 are connected to the output terminals of the second fiber optic circulator 108, 408. The input terminals of shapers 108 and 408 are connected to the output terminals of the second erbium-doped fiber amplifiers (EDFAs) 107 and 407. The input terminals of the second erbium-doped fiber amplifiers 107 and 407 are connected to the output terminals of the second polarization controllers 106 and 406. The input terminals of the second polarization controllers 106 and 406 are connected to the output terminal of the optical frequency comb frequency locking submodule. The pump laser output from the optical frequency comb frequency locking submodule and the auxiliary laser generated by the second tunable laser are coupled into the optical microcavity to generate the optical frequency comb.

[0036] Specifically, the output ends of the first fiber optic circulators 104 and 404 are connected to the output detection module, and the optical frequency combs generated in the optical microcavities 105 and 405 enter the output detection module through the first fiber optic circulators (CIRs) 104 and 404. The input ends of the second polarization controllers 106 and 406 are connected to the electro-optic modulators 209 and 509 in the frequency-locked submodule of the optical frequency comb.

[0037] The optical microcavities 105 and 405 include silicon nitride microring cavities, which are butterfly-shaped packaged to reduce the impact of the external environment on the stability of the optical frequency comb. Specifically, the optical microcavities 105 and 405 can be microring resonators (MRRs).

[0038] This invention employs an auxiliary laser heating method to generate an optical frequency comb. The first tunable lasers 201 and 501 used to generate the pump laser are specifically NKT lasers, preferably with a wavelength of 1550.12 nm and a linewidth of less than 10 Hz, which enhances the stability of the generated optical frequency comb. The second tunable lasers 101 and 401 used to generate the auxiliary laser are also specifically NKT lasers, preferably with a wavelength of 1540.75 nm. The auxiliary laser is used to keep the microcavity self-heated and locked.

[0039] In this embodiment of the invention, the optical frequency combs generated by nodes A and B are produced in two independent optical microcavities 105 and 405 (microring resonators MRR) with identical design parameters. Both the MRRs of nodes A and B are silicon nitride microring cavities with free spectral widths FSR1 = 49.743 GHz and FSR2 = 49.742 GHz, and a quality factor Q1 = 6.1 × 10⁻⁶. 6 Q2 = 5.9 × 10 6 .

[0040] When using auxiliary laser heating to generate an optical frequency comb, the auxiliary laser link is first configured. Specifically, the wavelength of the auxiliary laser output from the second tunable lasers 101 and 401 is adjusted to 1540.75nm. The polarization of the auxiliary laser is adjusted to match the TE mode of the optical microcavities 105 and 405 by the first polarization controllers 102 and 402. Then, the auxiliary laser signal is input to the first erbium-doped fiber amplifiers (EDFAs) 103 and 403 for amplification, and the output powers of the first erbium-doped fiber amplifiers 103 and 403 are set to 550mW and 750mW, respectively. Finally, the auxiliary laser enters the optical microcavities 105 and 405 through the first fiber circulators 104 and 404. The pump laser link is then configured. Specifically, the pump laser wavelength output from the first tunable lasers 201 and 501 is adjusted to 1550.12 nm. The polarization of the pump laser is adjusted to match the TE mode of the optical microcavities 105 and 405 by the second polarization controllers 106 and 406. The pump laser signal is then input to the second erbium-doped fiber amplifiers (EDFAs) 107 and 407 for amplification. The output powers of the second erbium-doped fiber amplifiers 107 and 407 are set to 900 mW and 500 mW, respectively. Finally, the pump laser enters the optical microcavities 105 and 405 through the second fiber circulators 108 and 408.

[0041] With the above setup, the pump laser is first coupled into optical microcavities 105 and 405, and the output wavelengths of the first tunable lasers 201 and 501 are adjusted to keep the pump laser in the red detuned region of the resonance peak, maintaining a constant pump laser wavelength of 1550.12 nm and output power. Then, an auxiliary laser is coupled into the optical microcavities 105 and 405 from the opposite direction to the pump laser, thereby maintaining intracavity thermal balance during the generation of the Kerr soliton optical comb. Next, the frequency of the second tunable lasers 101 and 401 is slowly decreased, causing the auxiliary laser to enter the blue detuned region of the resonance peak. Finally, the frequency of the tunable lasers 101 and 401 is increased until the pump laser stabilizes in the red detuned region of the resonance peak, thus generating a dissipative Kerr soliton optical comb.

[0042] This invention employs an auxiliary laser heating method to bring the pump laser into a red detuned state in a soliton state. This auxiliary laser heating method allows the microcavity to remain self-thermally locked, effectively stabilizing the pump detuning and suppressing soliton pulse width variations caused by random pump laser frequency drift. In fact, the pump laser is already locked to the ultrastable cavity and acetylene chamber using PDH locking technology, resulting in a very stable frequency. The auxiliary laser heating method further suppresses pump frequency jitter.

[0043] In some embodiments, such as Figure 5 As shown, the output detection module corresponding to each node includes: a second fiber coupler 301, 601, a first dense wavelength division multiplexer 303, 603, a second dense wavelength division multiplexer 304, 604, and a third fiber coupler 305, 605 connected in sequence. The output ends of the second fiber couplers 301, 601 are connected to spectrometers 302, 602. The output ends of the third fiber couplers 305, 605 are connected to power meters 306, 606, and the filtering module, respectively. The spectrometers 302, 602 are used to monitor the spectrum of the optical frequency comb. The first dense wavelength division multiplexers 303, 603 and the second dense wavelength division multiplexers 304, 604 are used to filter out pump laser and auxiliary laser from the optical frequency comb, respectively.

[0044] Specifically, the optical frequency comb from optical microcavities 105 and 405 is extracted. The optical frequency comb is split into two paths by the second fiber coupler 301 and 601. One path is sent to the spectrometer 302 and 602. The spectrum of the output optical frequency comb is observed by the spectrometer 302 and 602. When the optical frequency comb spectrum has a smooth envelope, soliton mode locking is completed. The other path enters the first dense wavelength division multiplexer 303 and 603. The second dense wavelength division multiplexer 304 and 604 filter out the pump-assisted laser and the auxiliary laser. The resulting optical frequency comb is split into two paths by the third fiber coupler 305 and 605. One path enters the power meter 306 and 606 to measure the power of the optical frequency comb. The other path is output to the filtering processing module for signal synchronization.

[0045] In this embodiment of the invention, the frequency of the auxiliary laser is reduced at a rate of 5 MHz / s, and then the spectrum in the spectrometer is observed, such as... Figure 6 As shown, after a smooth envelope appears, the frequency scan is stopped, at which point mode-locking of the dissipative Kerr soliton optical comb is achieved.

[0046] In some embodiments, such as Figure 4 As shown, the filtering module corresponding to each node includes: a filtering submodule, an encoding submodule, and a polarization control submodule connected in sequence. The input of the filtering submodule is connected to the output of the output detection module, and the output of the polarization control submodule is connected to the input of the interference module. The filtering submodules of any two nodes are respectively used to filter out the same-frequency comb teeth assigned to the two nodes from the processed optical frequency comb. The encoding submodules of any two nodes are respectively used to load quantum information into the same-frequency comb teeth to obtain quantum information-loaded same-frequency comb teeth. The polarization control submodules of any two nodes are respectively used to attenuate the light intensity of the quantum information-loaded same-frequency comb teeth to a weakly coherent state level, adjust the delay of the two photons through an adjustable delay line, and adjust the polarization consistency of the two photons through a polarization-maintaining beam splitter. The interference module is used to perform beam combining interference on the attenuated same-frequency comb teeth of the two nodes, and determine the relative time deviation between the optical signals of the two nodes through interferometry. The relative time deviation is sent to the adjustment module of the target node among the two nodes.

[0047] In some embodiments, the filtering submodules deployed locally on node A and node B have exactly the same structure and operating principle, such as... Figure 5 As shown, the filtering submodule includes: programmable optical filters (WSS) 701 and 702 and third polarization controllers (PC) 703 and 704 connected together. The input terminals of the programmable optical filters (WSS) 701 and 702 are connected to the output terminals of the output detection module, and the output terminals of the third polarization controllers 703 and 704 are connected to the input terminals of the encoding submodule.

[0048] Specifically, the input terminals of programmable optical filters (WSS) 701 and 702 are connected to the output terminals of the third fiber couplers 305 and 605 in the output detection module. The two optical frequency combs are filtered out by the programmable optical filters 701 and 702 to produce corresponding comb teeth of the same frequency. Then, the polarization state of the comb teeth is adjusted by the third polarization controllers 703 and 704, and then input to the input encoding submodule.

[0049] In some embodiments, the structure and working principle of the encoding submodules deployed locally on node A and node B are exactly the same, such as Figure 5 As shown, the encoding submodule includes: intensity modulators (IM) 801 and 802 and arbitrary waveform generators (AWG) 803 and 804. The optical signal input terminals of the intensity modulators 801 and 802 are connected to the output terminals of the filtering submodule. The radio frequency signal input terminals of the intensity modulators 801 and 802 are connected to the output terminals of the arbitrary waveform generators. The optical signal output terminals of the intensity modulators 801 and 802 are connected to the polarization control submodule.

[0050] Specifically, the input terminals of intensity modulators 801 and 802 are connected to the output terminals of the third polarization controllers 703 and 704 in the filtering submodule. The same-frequency comb teeth filtered out by the filtering submodule are respectively fed into intensity modulators (IM) 801 and 802 for modulation, and the output pulse width and repetition frequency are set by arbitrary waveform generators 803 and 804. The output pulse width is preferably 150 ps and the repetition frequency is preferably 10 MHz, that is, the continuous comb teeth are modulated into pulse wave packets.

[0051] In some embodiments, the polarization control submodules deployed locally on node A and node B have identical structures and operating principles, such as... Figure 5 As shown, the polarization control submodule includes: an adjustable delay line Delay 901, adjustable optical attenuators (VOA) 902 and 903, and polarization beam splitters (PBS) 904 and 905 connected in sequence.

[0052] Specifically, the adjustable delay line Delay 901 is connected to the output of the intensity modulator 802 in the encoding submodule, and the input of the adjustable optical attenuator 903 is connected to the output of the intensity modulator 801 in the encoding submodule. The adjustable optical attenuators (VOA) 902 and 903 attenuate the quantum information-loaded coherent comb teeth to a weakly coherent state level, with the photon count of each comb tooth attenuated to 300±20 k. The adjustable delay line Delay 901 compensates for the optical signal delay difference, and the polarization states of the two photons are adjusted by polarization beam splitters 904 and 905. The electrically controlled adjustable delay lines (901 and 903) of this embodiment have a wide delay adjustment range and high adjustment accuracy.

[0053] The overall processing flow of the filtering module is as follows: First, a programmable optical filter is used to select the same frequency comb teeth from the optical frequency combs of the two nodes and adjust their polarization state. Then, the light is cut into pulses by an intensity modulator and finally attenuated to a weak coherence level by an adjustable optical attenuator as the signal to be synchronized.

[0054] In some embodiments, such as Figure 4 As shown, the interference module includes: an interference submodule, a detection submodule, and a signal processing submodule connected in sequence; the interference submodule is used to perform beam interference on the same-frequency combs of any two nodes to obtain a beamed photon; the detection submodule is used to perform coincidence count measurement on the beamed photon to obtain interference fringes and locate the coincidence count minimum point, and calculate the relative time deviation between the optical signals of any two nodes based on the interference fringes and the coincidence count minimum point; the signal processing submodule is used to convert the relative time deviation into an error control signal and feed the error control signal back to the adjustment module of the target node; the adjustment module of the target node is used to adjust the local clock phase or optical path delay according to the error control signal, thereby driving the relative time deviation to tend to zero, realizing and maintaining signal synchronization between the two nodes.

[0055] Specifically, the input of the interference submodule is connected to the polarization control submodules deployed locally at nodes A and B, respectively, and the output of the signal processing submodule is connected to the input of the adjustment modules deployed locally at nodes A and B, respectively.

[0056] In some embodiments, such as Figure 5 As shown, the interference submodule includes a polarization-maintaining beam splitter (PMS) 906, the input of which is connected to the filtering module.

[0057] Specifically, the input of polarization-maintaining beam splitter 906 is connected to the outputs of polarization beam splitters 904 and 905 in the polarization control submodule, respectively. The same-frequency comb teeth of nodes A and B enter the polarization-maintaining beam splitter 906 to achieve interference beam combining.

[0058] In some embodiments, such as Figure 5As shown, the detection submodule includes: a fourth polarization controller (PC) 1001, a fifth polarization controller (PC) 1002, a first superconducting nanowire single-photon detector (SNSPD) 1003, a second superconducting nanowire single-photon detector (SNSPD) 1004, and a time-to-digital converter (TDC) 1005. The input terminals of the fourth polarization controller 1001 and the fifth polarization controller 1002 are respectively connected to the output terminals of the interference submodule. The output terminal of the fourth polarization controller 1001 is connected to the input terminal of the first superconducting nanowire single-photon detector 1003. The output terminal of the fifth polarization controller 1002 is connected to the input terminal of the second superconducting nanowire single-photon detector 1004. The output terminals of the first superconducting nanowire single-photon detector 1003 and the second superconducting nanowire single-photon detector 1004 are respectively connected to the time-to-digital converter 1005.

[0059] The superconducting nanowire single-photon detector in this embodiment of the invention features high detection efficiency, low dark count rate, and low time jitter. The time-to-digital converter 1005 has high time resolution and a high coincidence count upper limit. Furthermore, the fourth polarization controller 1001 and the fifth polarization controller 1002 can be embedded microprocessors, which can convert relative time deviations into proportional-integral-derivative control signals by running control algorithms.

[0060] Specifically, the input terminals of the fourth polarization controller 1001 and the fifth polarization controller 1002 are respectively connected to the output terminals of the polarization-maintaining beam splitter 906. The combined photons undergo phase, power, and photon number matching via the fourth polarization controller 1001 and the fifth polarization controller 1002, and are then detected by the first superconducting nanowire single-photon detector 1003 and the second superconducting nanowire single-photon detector 1004. A time-to-digital converter 1005 performs two-photon coincidence counting. The average dark count of the first superconducting nanowire single-photon detector 1003 and the second superconducting nanowire single-photon detector 1004 is approximately 60 times / second, which is negligible when measuring the visibility of HOM interference fringes. Figure 7 The HOM interference fringe for the third comb tooth is estimated to be 45.5 ± 0.04%.

[0061] The above example of synchronizing node A and node B illustrates the structure and principle of the synchronization device in this embodiment of the invention. For multi-node networks, by allocating combs of different wavelengths to different node pairs and utilizing wavelength division multiplexing technology, the HOM interferometry and synchronization feedback processes of multiple node pairs can be carried out in parallel within the same optical fiber infrastructure without interference. This efficiently achieves synchronization between any node pairs in the entire network, greatly improving the system's scalability and resource utilization.

[0062] This invention provides a quantum interference-based remote multi-node network signal synchronization device. By deploying an optical frequency comb generation module, a filtering module, and an adjustment module locally at each node, and an interference module externally to each node, it can configure an independent light source for each node. Simultaneously, utilizing the inherent multi-wavelength characteristics of the optical frequency comb, it can allocate dedicated communication wavelengths (i.e., co-frequency comb teeth) for communication between different node pairs, thereby achieving a decentralized synchronization architecture. In this application, synchronization can be directly established between any two nodes without the need for a central node relay, thus making the network topology more flexible and solving the single point of failure problem of star network architectures. Furthermore, the synchronization accuracy of this invention directly depends on the width of the HOM interference fringes (the coherence time of the photons used), and by utilizing the optical frequency comb teeth cut to ultrashort pulses, the synchronization accuracy can theoretically be improved to the femtosecond level, breaking through the accuracy limits of traditional synchronization methods. Furthermore, the visibility of HOM interference is extremely sensitive to disturbances in the photon state. Any eavesdropping, interception, or strong light injection attack targeting the synchronization signal (weakly coherent photons) will disrupt the quantum properties of the photons, leading to an abnormal decrease in interference visibility. This will be detected in real time and an alarm will be sent, thus providing an inherent physical layer security guarantee for the synchronization process. Moreover, this embodiment of the invention does not require a low-jitter, highly stable direct fiber optic link between nodes to transmit the reference clock signal. It only utilizes existing fiber optic links to transmit weak light pulses for interference. The final synchronization accuracy is determined by local interferometry and feedback control. Therefore, the absolute stability requirement for link transmission delay is greatly reduced, improving engineering practicality.

[0063] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application. Those skilled in the art will understand that the modules in the apparatus of the embodiment can be distributed within the apparatus of the embodiment as described, or can be modified to be located in one or more apparatuses different from this embodiment. The modules of the above-described embodiment can be combined into one module, or further divided into multiple sub-modules.

[0064] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A quantum interference based geographically distributed multi-node network signal synchronization apparatus, comprising: include: The optical frequency comb generation module, filtering module, and adjustment module are deployed locally at each node, and an interference module is deployed outside the node. The optical frequency comb generation module and filtering module of each node are connected to the input end of the interference module, and the output end of the interference module is connected to the adjustment module of each node. The optical frequency comb generation module of any two nodes that perform signal synchronization is used to generate independent optical frequency combs locally on the node. The optical frequency combs are frequency aligned by locking the pump laser frequency and the repetition frequency of the optical frequency comb. The filtering modules of any two nodes are respectively used to filter out the same frequency comb teeth allocated to the two nodes from their respective optical frequency combs; The interference module is used to perform beam interferometry on the same frequency combs of any two nodes, and determine the relative time deviation between the optical signals of any two nodes through interferometric measurement; and send the relative time deviation to the adjustment module of the target node among the two nodes. The adjustment module of the target node is used to adjust the local clock phase or optical path delay according to the relative time deviation in order to achieve signal synchronization.

2. The apparatus according to claim 1, characterized in that, The device further includes: an output detection module deployed locally at each node, wherein the optical frequency comb generation module, the output detection module, and the filtering processing module of each node are connected in sequence; The output detection modules of any two nodes are respectively used to filter out the pump laser and the auxiliary laser from their respective optical frequency combs to obtain the processed optical frequency combs; The filtering modules of any two nodes are respectively used to filter out the same frequency comb teeth assigned to the two nodes from their respective processed optical frequency combs.

3. The apparatus according to claim 2, characterized in that, The optical frequency comb generation module corresponding to each node includes: an optical frequency comb frequency locking submodule and an optical frequency comb generation submodule. The output end of the optical frequency comb frequency locking submodule is connected to the input end of the optical frequency comb generation submodule, and the output end of the optical frequency comb generation submodule is connected to the filtering module. The frequency locking submodules of any two nodes are used to lock the repetition frequency of the pump laser and the optical frequency comb, respectively. The optical frequency comb generation submodules of any two nodes are respectively used to generate the optical frequency comb through an auxiliary laser heating scheme.

4. The apparatus according to claim 3, characterized in that, The optical frequency comb frequency locking submodule includes: a first tunable laser, an acousto-optic modulator, a first fiber coupler, a Fabry-Perot cavity, an acetylene gas chamber, a photodetector, and a servo unit connected in sequence. The output terminal of the servo unit is connected to the input terminal of the first tunable laser and the input terminal of a voltage-controlled oscillator, respectively. The output terminal of the voltage-controlled oscillator is connected to the input terminal of the acousto-optic modulator. The output terminal of the first fiber coupler and the output terminal of a microwave signal generator are connected to the input terminal of an electro-optic modulator, respectively. The output terminal of the electro-optic modulator is connected to the optical frequency comb generation submodule.

5. The apparatus according to claim 3, characterized in that, The optical frequency comb generation submodule includes: a second tunable laser, a first polarization controller, a first erbium-doped fiber amplifier, a first fiber circulator, and an optical microcavity connected in sequence. The output end of the first fiber circulator is connected to the output detection module. The input end of the optical microcavity is connected to the output end of the second fiber circulator. The input end of the second fiber circulator is connected to the output end of the second erbium-doped fiber amplifier. The input end of the second erbium-doped fiber amplifier is connected to the output end of the second polarization controller. The input end of the second polarization controller is connected to the output end of the optical frequency comb frequency locking submodule. The pump laser output from the optical frequency comb frequency locking submodule and the auxiliary laser generated by the second tunable laser are coupled into the optical microcavity to generate the optical frequency comb.

6. The apparatus according to claim 2, characterized in that, The output detection module corresponding to each node includes: a second fiber coupler, a first dense wavelength division multiplexer, a second dense wavelength division multiplexer, and a third fiber coupler connected in sequence. The output end of the second fiber coupler is connected to a spectrometer, and the output end of the third fiber coupler is connected to a power meter and the filtering module, respectively. The spectrometer is used to monitor the spectrum of the optical frequency comb. The first dense wavelength division multiplexer and the second dense wavelength division multiplexer are used to filter out the pump laser and the auxiliary laser from the optical frequency comb, respectively.

7. The apparatus according to claim 2, characterized in that, The filtering module corresponding to each node includes: a filtering submodule, an encoding submodule, and a polarization control submodule connected in sequence. The input end of the filtering submodule is connected to the output end of the output detection module, and the output end of the polarization control submodule is connected to the input end of the interference module. The filtering submodules of any two nodes are respectively used to filter out the same frequency comb teeth assigned to the two nodes from the processed optical frequency comb; The encoding submodules of any two nodes are respectively used to load quantum information into the same frequency comb teeth to obtain the same frequency comb teeth after quantum information loading; The polarization control submodules of any two nodes are respectively used to attenuate the light intensity of the same frequency comb after the quantum information is loaded to the weak coherence state level, adjust the delay of the two photons through the adjustable delay line, and adjust the polarization of the two photons to be consistent through the polarization maintaining beam splitter. The interference module is used to perform beam interferometry on the attenuated co-frequency combs of any two nodes, and determine the relative time deviation between the optical signals of any two nodes through interferometric measurement; and send the relative time deviation to the adjustment module of the target node among the two nodes.

8. The apparatus according to claim 7, characterized in that, The filtering submodule includes: a programmable optical filter and a third polarization controller connected together, wherein the input terminal of the programmable optical filter is connected to the output terminal of the output detection module, and the output terminal of the third polarization controller is connected to the input terminal of the encoding submodule; and / or The encoding submodule includes: an intensity modulator and an arbitrary waveform generator; the optical signal input terminal of the intensity modulator is connected to the output terminal of the filtering submodule; the radio frequency signal input terminal of the intensity modulator is connected to the output terminal of the arbitrary waveform generator; and the optical signal output terminal of the intensity modulator is connected to the polarization control submodule; and / or The polarization control submodule includes: an adjustable delay line, an adjustable optical attenuator, and a polarization beam splitter connected in sequence.

9. The apparatus according to claim 1, characterized in that, The interference module includes: an interference submodule, a detection submodule, and a signal processing submodule connected in sequence; The interference submodule is used to perform beam-combining interference on the same frequency comb teeth of any two nodes to obtain a combined photon; The detection submodule is used to perform coincidence count measurement on the combined photons to obtain interference fringes and locate the coincidence count minimum point. Based on the interference fringes and the coincidence count minimum point, the relative time deviation between any two node optical signals is calculated. The signal processing submodule is used to convert the relative time deviation into an error control signal and feed the error control signal back to the adjustment module of the target node; The adjustment module of the target node is used to adjust the local clock phase or optical path delay according to the error control signal to achieve signal synchronization.

10. The apparatus according to claim 9, characterized in that, The interferometric submodule includes: a polarization-maintaining beam splitter, the input of which is connected to the filtering module; and / or The detection submodule includes: a fourth polarization controller, a fifth polarization controller, a first superconducting nanowire single-photon detector, a second superconducting nanowire single-photon detector, and a time-to-digital converter. The input terminals of the fourth and fifth polarization controllers are respectively connected to the output terminals of the interference submodule. The output terminal of the fourth polarization controller is connected to the input terminal of the first superconducting nanowire single-photon detector, and the output terminal of the fifth polarization controller is connected to the input terminal of the second superconducting nanowire single-photon detector. The output terminals of the first and second superconducting nanowire single-photon detectors are respectively connected to the time-to-digital converter.

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