Coherent ising machine system based on hollow-core fiber loop and operation acceleration optimization method
The coherent Ising machine system constructed using hollow fiber loops solves the problems of computational accuracy and environmental stability caused by solid fiber, achieving high signal-to-noise ratio and fast solution, thus improving the computational performance of the coherent Ising machine.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TIANFU JIANGXI LAB
- Filing Date
- 2026-03-06
- Publication Date
- 2026-06-30
Smart Images
Figure CN122316488A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of optical computing and quantum heuristic computing, and particularly to a coherent Ising machine system based on a hollow fiber loop and a computation acceleration optimization method. Background Technology
[0002] Coherent Ising Machine (CIM), as an emerging non-von Neumann computing architecture, uses coherent optical pulses with phase bistable characteristics to simulate Ising spins and solves complex combinatorial optimization problems through iterative evolution in fiber loops. In order to realize the computation of large-scale variables, CIM usually adopts time division multiplexing (TDM) technology and uses several kilometers of optical fiber as an optical delay storage medium to accommodate tens of thousands of spin pulses.
[0003] However, existing coherent Ising timer systems generally use standard single-mode fiber (SMF) to construct delay lines, which introduces several inherent technical drawbacks due to its physical characteristics. Specifically, firstly, the silica core of the solid fiber exhibits a strong Kerr nonlinear effect. In long-distance cyclic iterations, to avoid the accumulation of phase noise caused by self-phase modulation, the injected optical power must be strictly limited to a low level, typically below 7 ohms. The low-power operation mode of dBm makes the measurement end limited by the electronic thermal noise floor of the detector, making it difficult to obtain a sufficient signal-to-noise ratio. This directly leads to a decrease in the accuracy of spin state identification and makes it prone to getting trapped in local optima when dealing with complex optimization problems. Secondly, the high thermo-optic coefficient of solid fiber makes long-distance delay lines extremely sensitive to ambient temperature fluctuations. In order to maintain coherence, the system has to be equipped with highly complex active frequency stabilization hardware and redundant calibration algorithms, which significantly increases physical cost and time overhead. In addition, the group refractive index of standard single-mode fiber results in an optical transmission speed of only about 68% of the speed of light in vacuum. The physical layer iteration delay becomes a bottleneck to improve the computing speed. Finally, although hollow fiber has theoretical advantages in terms of low nonlinearity and low delay, directly splicing solid fiber will directly introduce coupling loss and coherent interference due to problems such as mode field mismatch and Fresnel reflection, making it difficult to apply directly to the existing coherent Ising machine architecture.
[0004] Therefore, a coherent Ising machine system that overcomes the nonlinear threshold limitation and solves the system stability problem under high power operation in order to achieve high-performance coherent computing is urgently needed. Summary of the Invention
[0005] To address the shortcomings of the existing technologies, this invention provides a coherent Ising machine system based on hollow fiber loops and a computation acceleration optimization method, which solves the technical problems of limited computational accuracy, severe phase noise accumulation, and poor environmental stability in existing coherent Ising machine systems based on solid fiber loops.
[0006] The present invention provides a coherent Ising machine system based on a hollow fiber loop, comprising: a light source module for outputting light pulses with high coherence and stable polarization state; A coherent pulse generation module, connected to the light source module, is used to convert the light pulse into a light pulse sequence with phase bistable characteristics, wherein each light pulse in the light pulse sequence corresponds to an Ising spin; The fiber optic loop module, connected to the coherent pulse generation module, is used to provide a fiber optic loop to store and support the cyclic iterative evolution of the optical pulse sequence in the fiber optic loop. The measurement and feedback module, connected to the optical fiber loop module, is used to perform phase measurement on the optical pulse sequence and calculate a feedback signal according to a preset coupling matrix, wherein the feedback signal is used to modulate the optical pulse sequence; The main transmission medium of the optical fiber loop is hollow optical fiber, which is configured to support optical pulse transmission with an average power higher than the power level limited by the nonlinear threshold of solid optical fiber. The fiber optic loop module also includes a low-reflection interconnect unit for connecting the hollow fiber and other optical devices within the system.
[0007] Another aspect of the present invention provides a computational acceleration optimization method for a coherent Ising machine system based on a hollow-core fiber loop, applicable to any of the aforementioned coherent Ising machine systems based on hollow-core fiber loops, comprising: The time slot allocation within the optical fiber loop is determined based on the problem to be solved, so as to establish the time-domain mapping between the optical pulse and the Ising spin, and the interaction matrix is preloaded. A sequence of optical pulses representing the Ising spin is injected into the optical fiber loop, and the average power of the optical pulse sequence is controlled to be higher than the nonlinear threshold of the solid fiber and above the electronic thermal noise floor of the measurement unit, so that the optical pulse sequence is iteratively transmitted under the high nonlinear threshold characteristics in the hollow fiber. A portion of the optical pulses is extracted from the optical fiber loop, and the phase state of the portion of the optical pulses is measured using the measurement unit under shot noise-limited conditions to obtain a signal-to-noise ratio higher than the electronic thermal noise limit; The feedback signal is generated by calculating the feedback quantity based on the phase state and the interaction matrix, and the feedback signal is modulated onto the optical pulse in the optical fiber loop to guide the Ising spin to evolve towards the lowest energy state. When the phase state remains stable during a preset number of iterations, the system is determined to have converged, and the final spin configuration is output as the solution to the problem to be solved.
[0008] The coherent Ising machine system and computation acceleration optimization method based on hollow fiber loops provided by this invention firstly, utilizes the low nonlinear coefficient of hollow fiber, enabling the system to operate at power levels higher than the nonlinear threshold of solid fiber without nonlinear phase shift accumulation. This supports low-noise delay lines ranging from several kilometers to tens of kilometers, accommodates spin variables in the tens of thousands, and, through high-power operation, allows the measurement feedback module to avoid electronic thermal noise, improving the signal-to-noise ratio by 3%. The improvements over dB significantly enhance spin state identification capabilities, reduce feedback errors, and increase the success rate of global optimal solution search. Secondly, considering the low intrinsic thermo-optic coefficient of hollow-core fiber, the sensitivity of long-distance delay lines to ambient temperature is greatly reduced, effectively suppressing phase decoherence caused by optical path drift, ensuring the physical consistency of large-scale pulse sequences in thousands of iterations, and reducing the dependence on high-frequency active phase-locked loops and precise temperature control algorithms, simplifying the hardware architecture and improving the reliability of operation in industrial environments. In addition, the low-reflection interconnection mechanism eliminates parasitic oscillation noise that is easily triggered under high-power operation, ensuring the purity of coherent pulses during phase-sensitive amplification, so that the system is not disturbed by feedback noise in the coherent superposition and evolution of spin states under high energy gain. Finally, the improved probe signal-to-noise ratio and reduced physical layer phase noise enable the system to converge to the energy ground state with more accurate gradient guidance. Combined with the characteristic that the signal transmission speed of hollow-core fiber is close to the speed of light in a vacuum, the physical delay of a single iteration is significantly shortened, and the total solution time for handling large-scale high-density spin interaction problems is greatly reduced. The aforementioned system supports high-power, high-precision computing and large-scale expansion, enhances phase stability and long-term environmental stability, achieves a low-noise evolution environment under high gain, and optimizes computational efficiency and convergence speed.
[0009] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.
[0010] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0011] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 A schematic diagram of the overall structure of a coherent Ising machine system based on a hollow fiber optic loop in one embodiment provided in this application; Figure 2 A flowchart illustrating a computational acceleration optimization method for a coherent Ising machine system based on a hollow fiber loop, provided in one embodiment of this application; Figure 3The graph shows the variation of relative photon count fluctuations at the output of a solid single-mode fiber system over time. Figure 4 A graph showing the variation of relative photon count fluctuation over time in the output of a coherent Ising machine system based on a hollow fiber loop, provided in one embodiment of this application; Figure 5 The graph shows the change in double coincidence count over time for a solid single-mode fiber system. Figure 6 A graph showing the variation of the double coincidence count over time in a coherent Ising machine system based on a hollow fiber loop, provided in one embodiment of this application. Detailed Implementation
[0012] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 this invention.
[0013] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.
[0014] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0015] This invention provides, in one aspect, a coherent Ising machine system based on a hollow-core fiber loop, such as... Figure 1As shown, the system includes: a light source module for outputting optical pulses with high coherence and stable polarization states; a coherent pulse generation module connected to the light source module for converting the optical pulses into a sequence of optical pulses with phase bistable characteristics, wherein each optical pulse in the sequence corresponds to an Ising spin; an optical fiber loop module connected to the coherent pulse generation module for providing an optical fiber loop to store and support the cyclic iterative evolution of the optical pulse sequence within the optical fiber loop; and a measurement and feedback module connected to the optical fiber loop module for performing phase measurements on the optical pulse sequence and calculating a feedback signal based on a preset coupling matrix, wherein the feedback signal is used to modulate the optical pulse sequence; wherein the main transmission medium of the optical fiber loop is hollow-core optical fiber, which is configured to support optical pulse transmission with an average power higher than the power level limited by the nonlinear threshold of solid-core optical fiber; the optical fiber loop module also includes low-reflection interconnect units for connecting the hollow-core optical fiber and other optical devices within the system.
[0016] The coherent Ising phase detector system based on hollow fiber loops provided by this invention, firstly, utilizes the low nonlinear coefficient of hollow fiber, enabling the system to operate at power levels exceeding the nonlinear threshold of solid fiber without nonlinear phase shift accumulation. It supports low-noise delay lines ranging from several kilometers to tens of kilometers, accommodates spin variables in the tens of thousands, and, through high-power operation, allows the measurement feedback module to avoid electronic thermal noise, improving the signal-to-noise ratio by 3%. The improvements over dB significantly enhance spin state identification capabilities, reduce feedback errors, and increase the success rate of global optimal solution search. Secondly, considering the low intrinsic thermo-optic coefficient of hollow-core fiber, the sensitivity of long-distance delay lines to ambient temperature is greatly reduced, effectively suppressing phase decoherence caused by optical path drift, ensuring the physical consistency of large-scale pulse sequences in thousands of iterations, and reducing the dependence on high-frequency active phase-locked loops and precise temperature control algorithms, simplifying the hardware architecture and improving the reliability of operation in industrial environments. In addition, the low-reflection interconnection mechanism eliminates parasitic oscillation noise that is easily triggered under high-power operation, ensuring the purity of coherent pulses during phase-sensitive amplification, so that the system is not disturbed by feedback noise in the coherent superposition and evolution of spin states under high energy gain. Finally, the improved probe signal-to-noise ratio and reduced physical layer phase noise enable the system to converge to the energy ground state with more accurate gradient guidance. Combined with the characteristic that the signal transmission speed of hollow-core fiber is close to the speed of light in a vacuum, the physical delay of a single iteration is significantly shortened, and the total solution time for handling large-scale high-density spin interaction problems is greatly reduced. The aforementioned system supports high-power, high-precision computing and large-scale expansion, enhances phase stability and long-term environmental stability, achieves a low-noise evolution environment under high gain, and optimizes computational efficiency and convergence speed.
[0017] The hollow fiber is configured to support the transmission of optical pulses with an average power higher than the power level limited by the nonlinear threshold of the solid fiber in the fiber loop. In a preferred embodiment of the invention, the average power is not less than 15 dBm, so as to give full play to the high nonlinear threshold advantage of the hollow fiber and achieve an effective improvement in the signal-to-noise ratio.
[0018] Specifically, in the above embodiments, the light source module includes: a mode-locked laser for outputting optical pulses; and a Dither-and-Lock frequency stabilization circuit, which is connected to the mode-locked laser and the fiber optic loop respectively, for locking the phase relationship between the fiber cavity length of the fiber optic loop and the repetition frequency of the optical pulses output by the mode-locked laser.
[0019] In this embodiment, the mode-locked laser is a high repetition rate mode-locked laser, whose repetition rate can be selected, for example but not limited to, from 500 MHz to 5 GHz, and the center wavelength is set to 775 nm. It is used to output optical pulses as the pump source for the subsequent coherent pulse generation module. The Dither-and-Lock frequency stabilization circuit is connected to the mode-locked laser and the fiber loop respectively. It is used to lock the phase relationship between the fiber cavity length of the fiber loop and the repetition frequency of the optical pulses output by the mode-locked laser. Through the active locking control of the frequency stabilization circuit, it can ensure that the fiber cavity length and the pulse repetition frequency are strictly matched, thereby ensuring that the time-division multiplexed multi-pulse sequence maintains stable synchronization in long-term cyclic iterations of more than a thousand times, which significantly improves the operational reliability and coherent evolution quality of the system.
[0020] Specifically, in the above embodiments, the coherent pulse generation module includes a phase-sensitive amplifier based on optical nonlinear effects, used to generate degenerate signal light pulses through a degenerate optical parametric oscillation process under pump light excitation, wherein the phase of the degenerate signal light pulses is locked to a state with a phase difference of 0 or π from that of the pump light, so as to form a light pulse sequence with phase bistable characteristics; the phase-sensitive amplifier is a periodically polarized lithium niobate waveguide.
[0021] In this embodiment, the phase-sensitive amplifier is specifically a periodically polarized lithium niobate waveguide (PPLN); the coherent pulse generation module uses the PPLN waveguide as its core device, and this waveguide operates in phase-sensitive amplification mode, forming a degenerate optical parametric oscillator; when the highly coherent pump light pulse output from the light source module is injected into the waveguide, under the nonlinear interaction satisfying the phase-matching condition, the degenerate optical parametric oscillation process is triggered, generating a degenerate signal light pulse with a frequency half that of the pump light, i.e., a degenerate optical parametric oscillation pulse. This process is essentially a phase-sensitive amplification process; specifically, the signal... The phase of the signal light is strictly locked to the phase reference of the pump light, and there are only two stable phase states, namely, a phase difference of 0 or π from the pump light, with a phase difference of 180° between them. Therefore, each degenerate optical parametric oscillation pulse naturally possesses phase bistable characteristics, which can be directly used to encode the "+1" and "-1" states of the Ising spin. Based on this, by controlling the injection timing of the pump light, a series of time-division multiplexed degenerate optical parametric oscillation pulses can be generated in the fiber loop, thereby forming an optical pulse sequence with phase bistable characteristics, where each optical pulse corresponds to an independent Ising spin.
[0022] Specifically, in the above embodiments, the low-reflection interconnect unit includes at least one of the following: a beveled fusion splice structure, an end-face anti-reflection coating structure, and a lens coupling structure, used to control the return loss at the interface between the hollow fiber and other optical devices to be not less than 40 dB, preferably not less than 50 dB, so as to suppress parasitic oscillations.
[0023] Furthermore, the hollow fiber is a microstructured clad hollow fiber, and the light guiding mechanism of the hollow fiber includes at least one of photonic bandgap light guiding, anti-resonance reflection light guiding, suppression coupling light guiding, or Bragg reflection light guiding; the hollow fiber is selected from one of double-nested anti-resonance nodeless fiber, single-ring anti-resonance fiber, Kagome fiber, photonic bandgap fiber, or Bragg fiber; the core filling medium of the hollow fiber is gas, and the nonlinear coefficient and thermo-optic coefficient of the hollow fiber are both lower than those of solid fiber.
[0024] Furthermore, the fiber optic loop module is encapsulated in a soundproof and heat-insulating shielded box with temperature control function.
[0025] In this embodiment, the main transmission medium of the fiber optic loop module can be a typical double-nested anti-resonant nodeless fiber. The core filling medium of this type of fiber is a gas, such as air. Its light guiding mechanism is based on the anti-resonant reflection effect, rather than the traditional total internal reflection. Therefore, it has extremely low nonlinear coefficient and extremely low thermo-optic coefficient, both significantly lower than solid fiber. This enables it to support stable transmission of optical pulses with an average power of not less than 15 dBm in the loop and effectively suppresses the accumulation of nonlinear noise such as self-phase modulation. At the same time, the optical path drift caused by ambient temperature fluctuations is greatly reduced, significantly improving the phase stability of long-term iterative evolution.
[0026] Furthermore, the highly symmetrical microstructure of double-nested anti-resonant nodeless fibers endows them with excellent polarization preservation and high-order mode suppression capabilities, maintaining pure fundamental mode transmission even under temperature changes or mechanical disturbances, effectively avoiding mode crosstalk interference on spin coding and feedback accuracy. Among these, the guiding mechanism of single-ring anti-resonant fibers and Kagome fibers is also based on anti-resonant reflection, while the guiding mechanism of photonic bandgap fibers is based on photonic bandgap, and the guiding mechanism of Bragg fibers is based on Bragg reflection. These fibers also use gas as the core medium and share common advantages such as low nonlinearity, low thermal sensitivity, and wideband low-loss transmission.
[0027] Furthermore, a low-reflection interconnection unit is provided at the interface between the hollow fiber and other optical devices in the system. This interconnection unit can be implemented by at least one of the following: a beveled fusion splice structure, an anti-reflection coating structure on the end face, and a lens coupling structure. This ensures that the return loss at the connection interface is not less than 40 dB, preferably more than 50 dB. This effectively eliminates Fresnel reflection and parasitic oscillation noise that are easily triggered under high-power operation conditions, ensuring the phase purity of the coherent pulse during phase-sensitive amplification and cyclic iteration, and avoiding feedback noise interference with the coherent superposition and evolution of the spin state.
[0028] To further enhance the system's ability to isolate itself from environmental disturbances, the fiber optic loop module is encapsulated in a soundproof and heat-insulating shielded box with temperature control. Specifically, through passive vibration isolation, sound insulation, and active temperature control, it provides a stable thermal and mechanical working environment for long-distance fiber optic delay lines. This complements the inherent low thermal sensitivity of hollow fiber, jointly ensuring the physical consistency and long-term operational reliability of large-scale pulse sequences in thousands of iterations.
[0029] Specifically, in the above embodiments, the measurement and feedback module includes: an optical coupler connected to the optical fiber loop for extracting a portion of the optical pulses from the optical fiber loop; a measurement unit connected to the optical coupler for measuring the phase or amplitude of the extracted portion of the optical pulses and outputting the measurement results; a processing unit connected to the measurement unit for receiving the measurement results and performing multiplication operations of the Ising model coupling matrix to generate a feedback signal; and a modulator connected to both the processing unit and the optical fiber loop for loading the feedback signal onto the optical pulses in the optical fiber loop.
[0030] In this embodiment, the optical coupler is preferably a 90:10 fiber optic coupler, whose input end is connected to the fiber optic loop to extract a portion of the optical pulses from the loop as measurement samples. The optical coupler branches out 10% of the optical energy in the loop to the measurement branch, while the remaining 90% continues to circulate and evolve within the loop. This ensures sufficient probe power for spin state discrimination while maintaining controllable energy loss in the main loop. The measurement unit can employ a balanced homodyne detector, capable of extracting the in-phase or quadrature components of the optical pulses with shot noise-limited sensitivity, thereby accurately determining the Ising spin state corresponding to each optical pulse. The analog electrical signal output by the measurement unit is digitized by an analog-to-digital converter to form a measurement result characterizing the current spin configuration. The processing unit is preferably implemented using a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), such as... Figure 1 As shown, the system specifically includes a high-speed ADC, an FPGA, and a high-speed DAC connected in sequence. These are used to convert the analog signal output by the measurement unit into a digital signal, and after processing, the generated feedback signal digital value is converted into an analog voltage. During the system initialization phase, the coupling matrix of the Ising model of the combinatorial optimization problem to be solved is pre-stored in the memory of the processing unit. In each iteration, the processing unit performs matrix-vector multiplication operations in parallel according to the real-time input phase state of each spin, quickly calculates the feedback amount that each spin should receive, and generates the corresponding feedback signal digital value accordingly. This digital value is then converted into an analog modulation voltage by a digital-to-analog converter. The modulator can be an electro-optic intensity modulator or a phase modulator. Based on the analog feedback voltage output by the processing unit, it precisely modulates the amplitude or phase of the optical pulse in the corresponding time slot in the loop, thereby achieving injection locking or coherent coupling and guiding the Ising spin system to evolve towards the lowest Hamiltonian energy state.
[0031] As a preferred embodiment of the present invention, the system further includes a management unit physically connected to the optical fiber loop for dynamic compensation of residual environmental disturbances in the loop. Although hollow-core optical fibers inherently possess low thermal sensitivity, polarization preservation, and weak dispersion characteristics, in large-scale, ultra-long-term high-speed iterative operation, minute environmental changes may still accumulate with the number of cycles, resulting in phase errors. Therefore, the management unit is further configured as at least one of the following: a dispersion management unit for compensating for residual dispersion effects in the loop, ensuring that optical pulses in different time slots maintain accurate time-domain alignment after thousands of cycles; a polarization management unit for actively correcting minute polarization state drift caused by mechanical stress or temperature gradients, maintaining high interference efficiency in the phase-sensitive amplification process; and a temperature management unit that works in conjunction with the temperature control system of the encapsulation shielding box to finely adjust local temperature fluctuations, further suppressing optical path drift. Through the selection and dynamic compensation of the above management units, the system can maintain the inherent advantages of hollow-core optical fibers while further suppressing residual disturbances, thereby supporting stable, high-fidelity coherent evolution at larger spin numbers and longer iteration times.
[0032] In a preferred embodiment of the present invention, the system continuously evolves the optical pulse sequence in the optical fiber loop through an iterative closed-loop mechanism of injection, circulation, measurement, and feedback to search for the global ground state of the Ising Hamiltonian. Specifically, thanks to the extremely low nonlinear coefficient of the hollow-core optical fiber, the system can withstand the stable transmission of optical pulses with an average power of up to 15 dBm in the loop without triggering nonlinear effects such as self-phase modulation that would lead to signal degradation. The high-power operation mode allows the operating point of the measurement feedback module to break through the electronic thermal noise limit and enter the shot noise-limited region, thereby obtaining a power level exceeding 3. The high signal-to-noise ratio (SNR) directly improves the accuracy of spin-state phase interpretation, significantly enhances the system's ability to sense energy gradients, and thus improves the ground-state convergence probability and solution quality. Furthermore, the hollow-core fiber used in this embodiment not only possesses high nonlinear threshold characteristics, but its highly symmetrical microstructure also endows the system with excellent additional performance. On the one hand, the fiber has a natural ability to suppress birefringence effects caused by temperature changes and mechanical disturbances, and the polarization state remains highly stable during long-term operation without the need for complex active polarization control. On the other hand, its anti-resonant light guiding mechanism has a strong attenuation effect on higher-order spatial modes, ensuring that only the fundamental mode propagates effectively in the loop, effectively suppressing mode crosstalk and mode noise, and preventing them from interfering with the accurate encoding and high-fidelity feedback of the spin state. These characteristics together ensure the physical consistency and computational reliability of the system in large-scale, long-term iterative evolution.
[0033] Another aspect of the present invention provides a computation acceleration optimization method for a coherent Ising machine system based on a hollow-core fiber loop. The method is applied to any of the aforementioned coherent Ising machine systems based on a hollow-core fiber loop, comprising: determining the time slot allocation within the fiber loop based on the problem to be solved, to establish a time-domain mapping between optical pulses and Ising spins, and preloading the interaction matrix; injecting an optical pulse sequence representing the Ising spin into the fiber loop, controlling the average power of the optical pulse sequence to be higher than the nonlinear threshold of the solid fiber and above the electronic thermal noise floor of the measurement unit, so that the optical pulse sequence is iteratively transmitted under the high nonlinear threshold characteristics in the hollow fiber; extracting a portion of the optical pulses in the fiber loop, and measuring the phase state of the portion of the optical pulses using the measurement unit under shot noise-limited conditions to obtain a signal-to-noise ratio higher than the electronic thermal noise limit; calculating the feedback quantity based on the phase state and the interaction matrix to generate a feedback signal, and modulating the feedback signal onto the optical pulses in the fiber loop to guide the Ising spin to evolve towards the lowest energy state; when the phase state remains stable in a preset number of iterations, determining that the system has converged, and outputting the final spin configuration as the solution to the problem to be solved.
[0034] Furthermore, the optical power of some optical pulses is configured to be higher than the electronic thermal noise equivalent power of the measurement unit, so that the phase measurement process is under shot noise-limited conditions.
[0035] This embodiment provides a computation acceleration optimization method for a coherent Ising machine system based on a hollow-core fiber loop hardware architecture. The specific control flow is as follows: Figure 2 As shown, the method for achieving fast solutions to complex combinatorial optimization problems includes the following steps: Step 1: Problem Mapping and System Initialization; The interaction matrix of the MAX-CUT problem or other combinatorial optimization problem to be solved is preloaded into the FPGA of the measurement and feedback module. The light source module is started and outputs stable continuous light. The coherent pulse generation module generates 10,000 initial phase random coherent light pulses according to the preset time slot allocation. Each pulse represents a spin variable to be solved.
[0036] Step 2: High-power energy level injection and evolution; The generated pulse sequence is injected into the hollow fiber loop, and the optical amplifier in the FPGA adjusts the loop to directly increase the average power of the pulse sequence to a high level. Since the hollow fiber has extremely high nonlinear phase shift suppression capability, the pulse can be iterated at a high power far exceeding the upper limit of the solid fiber, and will not trigger nonlinear effects that cause phase disorder.
[0037] Step 3: Precise measurement of spin phase; In each cycle, the measurement and feedback module extracts a small portion of the light energy from the loop. Since the injected power is at a high energy level of over 15 dBm, the pulse intensity received by the detector is significantly higher than the electronic thermal noise floor of the detector itself. The detection system spontaneously enters the shot noise-limited working region. The measurement and feedback module performs high-fidelity sampling of the in-phase component of each pulse and uses the improved signal-to-noise ratio gain of over 3 dB to accurately determine the current phase polarity of each spin.
[0038] Step 4: Feedback calculation based on high-quality signal-to-noise ratio; The FPGA calculates the feedback force on each spin in real time based on the high-precision spin state obtained in Step 3 and the pre-loaded interaction matrix. Since the measurement data is subject to very low noise interference, the calculated feedback quantity can accurately reflect the descent gradient of the Ising Hamiltonian. The feedback pulse is modulated and injected into the loop, and coherently superimposed with the evolving spin pulse, guiding the system to jump to a lower energy state.
[0039] Step 5: Self-sustaining evolution of phase stability; During thousands of cyclic iterations, utilizing the extremely low thermal sensitivity of hollow fiber, the system does not need to perform high-frequency cavity length compensation operations. The pulse sequence evolves rapidly under near-vacuum light speed transmission conditions. Furthermore, because physical layer noise is suppressed to an extremely low level, the system can more sensitively perceive subtle fluctuations on the potential energy surface, thereby effectively escaping local optima.
[0040] Step Six: Convergence Determination and Result Reading; When the detected pulse phase sequence remains stable for 100 consecutive cycles, the system is determined to have reached convergence. The measurement and feedback module outputs the final phase-locking result, which corresponds to the optimal or near-optimal solution of the problem. Experiments have shown that, under the same computational accuracy requirements, the high-power operation mechanism described in this embodiment can reduce the number of iterations by more than 10% compared to the low-power operation mode.
[0041] This invention also provides a comparative test of the stability of single-mode fiber (SMF) and hollow fiber. Specifically, a 1 km long Coherent Ising Machine (CIM) loop system was built, using commercial SMF-28e and hollow fiber as the loop medium. Except for the transmission fiber, the other components of the system, including the mode-locked laser, PPLN waveguide, phase modulator, photodetector, etc., and the operating conditions were kept consistent. The entire experiment was conducted in a normal laboratory room temperature environment, with a temperature fluctuation range of approximately 20 ℃ to 23 ℃.
[0042] Among them, the analysis of polarization stability test results is as follows: Figure 3As shown, when using SMF, the relative photon count fluctuation of the system output exhibits significant fluctuations over time, decreasing from approximately 100% initially to a minimum of 83% within 7 hours, with a maximum fluctuation amplitude of 17%. This indicates that the fluctuation trend is highly correlated with room temperature changes; the count decreases as the temperature rises and rises as the temperature falls, suggesting that the polarization state of the light field in the SMF is severely affected by thermally induced birefringence, leading to unstable nonlinear gain. In contrast, as... Figure 4 As shown, when hollow fiber is used, the relative photon count fluctuation is maintained at almost 100% within 7 hours, with a fluctuation amplitude of less than ±1%. Even during periods of drastic room temperature changes, there is no significant attenuation. This indicates that the optical field in hollow fiber mainly propagates in the air core, and its refractive index is not sensitive to temperature changes. Furthermore, the anti-resonance effect generated at the interface between the glass cladding and the air core effectively suppresses stress-induced birefringence, thereby achieving extremely high polarization stability.
[0043] Higher-order modes (HOMs) elicit behavioral responses, for example Figure 5 As shown, when using SMF, the two-fold coincidences detected by the system fluctuated drastically over 7 hours, dropping from an initial approximately 6000 coincidences / 15 seconds to a minimum of approximately 2000 coincidences / 15 seconds, a decrease of over 60%. This phenomenon was synchronized with room temperature changes, indicating that SMF easily excites higher-order modes under temperature variations, causing mode crosstalk, disrupting the spatiotemporal coherence of the optical pulse, and severely affecting the stable evolution of the DOPO spin state; while... Figure 6 As shown, when using hollow fiber, the double coincidence count remained within a stable range of approximately 2300–2700 times / 15 seconds throughout the entire test, with a fluctuation range of less than ±8%, which is far superior to the SMF system. Despite significant fluctuations in room temperature, the HOM response of the hollow fiber system was almost unaffected, indicating that it has excellent mode selectivity and resistance to environmental interference.
[0044] In summary, the above experimental results fully demonstrate that, under the same environmental disturbance conditions, replacing traditional standard single-mode fiber with the hollow-core fiber of this application can significantly suppress polarization drift and higher-order mode excitation caused by temperature changes, enabling the CIM system to maintain stable nonlinear gain and coherent evolution process during long-term operation. This effect is difficult to achieve with existing CIM systems based on solid single-mode fiber, reflecting the substantial progress of this invention in improving the stability of quantum computing systems.
[0045] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A coherent Ising machine system based on a hollow-core fiber loop, characterized in that, include: The light source module is used to output light pulses with high coherence and stable polarization state; A coherent pulse generation module, connected to the light source module, is used to convert the light pulse into a light pulse sequence with phase bistable characteristics, wherein each light pulse in the light pulse sequence corresponds to an Ising spin; The fiber optic loop module, connected to the coherent pulse generation module, is used to provide a fiber optic loop to store and support the cyclic iterative evolution of the optical pulse sequence in the fiber optic loop. The measurement and feedback module, connected to the optical fiber loop module, is used to perform phase measurement on the optical pulse sequence and calculate a feedback signal according to a preset coupling matrix, wherein the feedback signal is used to modulate the optical pulse sequence; The main transmission medium of the optical fiber loop is hollow optical fiber, which is configured to support optical pulse transmission with an average power higher than the power level limited by the nonlinear threshold of solid optical fiber. The fiber optic loop module also includes a low-reflection interconnect unit for connecting the hollow fiber and other optical devices within the system.
2. The coherent Ising machine system based on a hollow-core fiber loop according to claim 1, characterized in that, The hollow fiber is a microstructured clad hollow fiber, and the light guiding mechanism of the hollow fiber includes at least one of photonic bandgap light guiding, anti-resonance reflection light guiding, suppression coupling light guiding, or Bragg reflection light guiding. The hollow fiber is selected from one of the following: double-nested anti-resonance nodeless fiber, single-ring anti-resonance fiber, Kagome fiber, photonic bandgap fiber, or Bragg fiber. The core of the hollow optical fiber is filled with gas, and the nonlinear coefficient and thermo-optic coefficient of the hollow optical fiber are both lower than those of the solid optical fiber.
3. The coherent Ising machine system based on a hollow fiber optic loop according to claim 1, characterized in that, The low-reflection interconnect unit includes at least one of the following: a beveled fusion splice structure, an end-face anti-reflection coating structure, and a lens coupling structure, used to control the return loss at the interface between the hollow fiber and other optical devices to be no less than 40 dB, so as to suppress parasitic oscillations.
4. The coherent Ising machine system based on a hollow-core fiber loop according to claim 1, characterized in that, The coherent pulse generation module includes a phase-sensitive amplifier based on optical nonlinear effects, used to generate degenerate signal light pulses through a degenerate optical parametric oscillation process under pump light excitation, wherein the phase of the degenerate signal light pulses is locked to a state where the phase difference from the pump light is 0 or π, so as to form the light pulse sequence with phase bistable characteristics. The phase-sensitive amplifier is a periodically polarized lithium niobate waveguide.
5. The coherent Ising machine system based on a hollow-core fiber loop according to claim 1, characterized in that, The measurement and feedback module includes: An optical coupler, connected to the optical fiber loop, is used to extract a portion of the optical pulse from the optical fiber loop; The measurement unit, connected to the optical coupler, is used to measure the phase or amplitude of a portion of the extracted optical pulses and output the measurement results. A processing unit, connected to the measurement unit, is used to receive the measurement results and perform multiplication operations on the Ising model coupling matrix to generate a feedback signal; A modulator, connected to both the processing unit and the optical fiber loop, is used to load the feedback signal onto the optical pulse in the optical fiber loop.
6. The coherent Ising machine system based on a hollow-core fiber loop according to claim 1, characterized in that, The light source module includes: A mode-locked laser is used to output optical pulses; A frequency stabilization circuit is connected to both the mode-locked laser and the fiber optic loop, and is used to lock the phase relationship between the fiber cavity length of the fiber optic loop and the repetition frequency of the optical pulses output by the mode-locked laser.
7. The coherent Ising machine system based on a hollow-core fiber loop according to claim 1, characterized in that, The fiber optic loop module is encapsulated in a soundproof and heat-insulating shielded box with temperature control function.
8. The coherent Ising machine system based on a hollow-core fiber loop according to any one of claims 1 to 7, characterized in that, Also includes: The management unit operates on the optical fiber loop and is used to dynamically compensate for residual environmental disturbances in the optical fiber loop. The management unit is at least one of a dispersion management unit, a polarization management unit, and a temperature management unit.
9. A computational acceleration optimization method for a coherent Ising machine system based on a hollow-core fiber loop, characterized in that, Implemented using a coherent Ising machine system based on a hollow-core fiber loop as described in any one of claims 1 to 8, comprising: The time slot allocation within the optical fiber loop is determined based on the problem to be solved, so as to establish the time-domain mapping between the optical pulse and the Ising spin, and the interaction matrix is preloaded. A sequence of optical pulses representing the Ising spin is injected into the optical fiber loop, and the average power of the optical pulse sequence is controlled to be higher than the nonlinear threshold of the solid fiber and above the electronic thermal noise floor of the measurement unit, so that the optical pulse sequence is iteratively transmitted under the high nonlinear threshold characteristics in the hollow fiber. A portion of the optical pulses is extracted from the optical fiber loop, and the phase state of the portion of the optical pulses is measured using the measurement unit under shot noise-limited conditions to obtain a signal-to-noise ratio higher than the electronic thermal noise limit; The feedback signal is generated by calculating the feedback quantity based on the phase state and the interaction matrix, and the feedback signal is modulated onto the optical pulse in the optical fiber loop to guide the Ising spin to evolve towards the lowest energy state. When the phase state remains stable during a preset number of iterations, the system is determined to have converged, and the final spin configuration is output as the solution to the problem to be solved.
10. The method according to claim 9, characterized in that, The optical power of the partial optical pulse is configured to be higher than the electronic thermal noise equivalent power of the measurement unit, so that the phase measurement process is under shot noise-limited conditions.