Spin-orbit micro-laser, high-dimensional quantum key distribution system and method

Abstract

The application discloses a spin-orbit micro-laser, a high-dimensional quantum key distribution system and a method. The spin-orbit micro-laser comprises a semiconductor substrate, at least two optical resonant cavities on the semiconductor substrate, and a coupling unit for introducing adjustable non-Hermite coupling between and / or in the optical resonant cavities. The spin-orbit micro-laser of the application can directly generate N>=4-dimensional spin-orbit photonic quantum states on a chip without external state modulation devices, and the system complexity is reduced. The time-space characteristics of all generated quantum states are consistent, and the transmission and detection error rates are reduced. The adjustable non-Hermite coupling can realize nanosecond-level fast switching of quantum states, and the key generation rate is improved. The high-dimensional quantum state transmitter is integrated on a micron-level chip, and the volume is reduced by several orders of magnitude compared with a free space system, thereby laying a foundation for realizing a chipped QKD terminal and large-scale production.

Description

Technical Field

[0001] This invention relates to the field of quantum communication technology, and in particular to a spin-orbit microlaser, a high-dimensional quantum key distribution system, and a high-dimensional quantum key distribution method. Background Technology

[0002] Quantum Key Distribution Network (QKD) is theoretically an unconditionally secure communication technology. Most QKD systems utilize two-dimensional qubits, with an information capacity limit of one qubit per photon, and are relatively sensitive to channel noise. High-dimensional QKD, by leveraging qubits, can increase the information capacity per photon to [a higher level]. This approach, which increases the number of bits and exhibits a higher noise tolerance threshold, is an important direction for breaking through the existing performance bottleneck of QKD.

[0003] Currently, schemes for realizing high-dimensional quantum key distribution (HD-QKD) mainly fall into two categories:

[0004] 1. Free-space optics approach: This approach utilizes bulk optical elements such as spatial light modulators and q-plates to manipulate the orbital angular momentum and spin angular momentum of photons to prepare high-dimensional states. While flexible, this approach suffers from large system size, requires precise optical alignment, is extremely sensitive to environmental vibrations and disturbances, and exhibits poor long-term stability. More importantly, its manipulation complexity increases exponentially with dimension N. Growth makes it difficult to achieve miniaturization, integration, and large-scale practical deployment.

[0005] 2. Traditional integrated photonics approach: This typically employs a cascaded network of Mach-Zehnder interferometers to synthesize high-dimensional quantum states. While this approach has integration potential, it requires at least... The presence of individual phase modulators and coherent interference units results in a large chip area, high power consumption, severe crosstalk between units, and insertion loss that accumulates with dimensionality. This limits its ability to expand to higher dimensions and its capacity for high-speed dynamic reconfiguration.

[0006] Furthermore, there is an inherent contradiction between state generation and state transmission in the above schemes. For example, the complex structured light field generated by the free-space scheme is prone to mode coupling, distortion, and walk-off in atmospheric turbulence or optical fibers, leading to an increase in the bit error rate at the receiver. This often requires complex adaptive optics or post-selection techniques for compensation, further increasing the complexity and instability of the system.

[0007] Therefore, the relevant technologies lack a solution that can achieve compact integration, dynamic controllability, and robust intrinsic transmission of high-dimensional quantum states at the physical source. Summary of the Invention

[0008] In one embodiment of the present invention, the present invention is proposed to solve at least one of the above-mentioned problems. According to a first aspect of the present invention, a spin-orbit microlaser is provided, comprising: Semiconductor substrate; At least two optical resonant cavities are located on the semiconductor substrate; Coupling units for introducing tunable non-Hermitian coupling between and / or within the optical resonant cavities.

[0009] In one embodiment of the present invention, the optical resonant cavity is a micro-ring resonant cavity; The inner wall of the micro-ring resonator is etched with an angular grating, which is used to couple the whispering gallery mode in the cavity into an outgoing beam perpendicular to the plane of the semiconductor substrate, and to give the outgoing beam a defined orbital angular momentum quantum number.

[0010] In one embodiment of the present invention, the coupling unit includes a plurality of helical waveguides and a plurality of pump electrodes; The spiral waveguide is evanescently coupled or directly connected to different spatial positions of the two micro-ring resonators to inject pump energy into the micro-ring resonators. By adjusting the pump intensity and spatial distribution, the non-Hermitian coupling between the micro-ring resonators is dynamically controlled to lasing out spin-orbit photon quantum states. The pump electrode is connected to each of the spiral waveguides in a one-to-one correspondence, and is used to inject pump current into the corresponding spiral waveguide.

[0011] In one embodiment of the present invention, the number of helical waveguides is four, and they are arranged on the semiconductor substrate in a 90-degree rotational symmetry manner.

[0012] According to a second aspect of the present invention, a high-dimensional quantum key distribution system is provided, the system comprising: a transmitter, a receiver, a classical channel, a quantum channel, and a control and processing unit; The transmitting end includes the aforementioned spin-orbit microlaser and adjustable attenuator; The spin-orbit microlaser is used to generate spin-orbit photon quantum states in N≥4-dimensional Hilbert space, and dynamically generates and switches quantum states by controlling the non-Hermitian coupling between internal modes, and outputs corresponding lasing pulses. The adjustable attenuator, connected to the spin-orbit microlaser, is used to modulate the lasing pulse into a weakly coherent pulse containing a signal state, a decoy state, and a vacuum state. The receiver, connected to the transmitter via the classical channel and the quantum channel, includes: a spin-orbit mode sorter and one or more single-photon detectors; The spin-orbit mode sorter is used to perform mode sorting on the weakly coherent pulses; The single-photon detector is connected to the spin-orbit mode sorter and is used to perform single-photon detection on the sorted photons and output a detection event signal. The control and processing unit is connected to the transmitter and the receiver respectively, and is used to control the pump sequence and intensity of the transmitter, and generate a security key by performing a post-processing protocol of basis vector comparison, decoy state analysis, error correction and privacy amplification based on the detection event signal and through the classical channel.

[0013] In one embodiment of the present invention, the different spin-orbit photon quantum states generated by the spin-orbit microlaser have the same spatial mode and temporal waveform, and propagate in the transmission medium with the same phase velocity and group velocity.

[0014] In one embodiment of the present invention, the transmitting end further includes: a decoy state generation and control module; The decoy state generation and control module is connected to the adjustable attenuator and is used to adjust the attenuation of the adjustable attenuator to alternately output signal state, decoy state and vacuum state pulses with different average photon numbers.

[0015] In one embodiment of the present invention, the strength of the signal state is greater than the strength of the decoy state, and the strength of the decoy state is greater than the strength of the vacuum state; The intensity of the signal state is less than 1, and the intensity of the vacuum state is equal to 0.

[0016] According to a third aspect of the present invention, a high-dimensional quantum key distribution method is provided, which is applied to the above-described high-dimensional quantum key distribution system, the method comprising: The control and processing unit controls the spin-orbit microlaser to generate spin-orbit photon quantum states in N≥4-dimensional Hilbert space, and dynamically generates and switches quantum states by regulating the non-Hermitian coupling between the modes inside the spin-orbit microlaser, and outputs corresponding lasing pulses. The adjustable attenuator modulates the lasing pulse into a weakly coherent pulse that includes a signal state, a decoy state, and a vacuum state; The transmitter transmits the weakly coherent pulse to the receiver via a quantum channel; A spin-orbit mode sorter performs mode sorting on the weakly coherent pulses; One or more single-photon detectors perform single-photon detection on the sorted photons and output detection event signals to the control and processing unit; The control and processing unit generates a security key based on the detected event signal and by performing post-processing protocols such as basis vector comparison, decoy state analysis, error correction, and privacy amplification through the classical channel.

[0017] According to embodiments of the present invention, the spin-orbit microlaser, high-dimensional quantum key distribution system, and method eliminate the bulky free-space state preparation components and complex interferometer networks, enabling the direct generation of N≥4 dimensional spin-orbit photonic quantum states on a chip without the need for external state modulation devices, thus reducing system complexity. All generated quantum states exhibit consistent spatiotemporal characteristics, reducing transmission and detection error rates. Tunable non-Hermitian coupling enables nanosecond-level rapid switching of quantum states, improving the key generation rate. Integrating a high-dimensional quantum state transmitter onto a micrometer-scale chip reduces the volume by several orders of magnitude compared to free-space systems, laying the foundation for realizing chip-based QKD terminals and large-scale production. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a spin-orbit microlaser provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a microring resonator provided in an embodiment of the present invention; Figure 3 This is a diagram showing the result of an 8×8 probability detection matrix provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a high-dimensional quantum key distribution system provided in an embodiment of the present invention; Figure 5 The figure shows the test results of system performance varying with channel conditions according to an embodiment of the present invention. Figure 6(a) is a graph showing the change of the bit error rate of a quantum bit over time according to an embodiment of the present invention; Figure 6(b) shows the change of quantum state utilization over time according to an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described herein, all other embodiments obtained by those skilled in the art without inventive effort should fall within the protection scope of the present invention.

[0021] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0022] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0023] To fully understand this invention, a detailed structure will be presented in the following description to illustrate the technical solution proposed by this invention. Optional embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0024] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] To reduce the complexity of HD-QKD systems, the first aspect of this invention provides a spin-orbit microlaser, such as... Figure 1 As shown, the spin-orbit microlaser 101 includes:

[0026] Semiconductor substrate 1011.

[0027] As an example, the semiconductor substrate 1011 is an InP-based or GaAs-based single-crystal semiconductor substrate.

[0028] At least two optical resonant cavities 1012 are located on a semiconductor substrate 1011.

[0029] It is worth mentioning that the optical resonator 1012 can generate up to 2-dimensional quantum states. Through mode coupling and coherent superposition of two optical resonators 1012, high-dimensional spin-orbit photon quantum states in N≥4-dimensional Hilbert space can be constructed, thereby meeting the requirements of high-dimensional quantum key distribution.

[0030] It should be noted that, Figure 1 The number of optical resonators 1012 given is 2, which is only an example. The specific number of optical resonators 1012 can be determined according to the actual application.

[0031] Coupling unit 1013 for introducing tunable non-Hermitian coupling between and / or within optical resonant cavities 1012.

[0032] Preferably, the material platform adopts a III-V group semiconductor material system, such as an active gain region based on InGaAsP multiple quantum wells, operating in the 1550nm communication band.

[0033] The spin-orbit microlaser of this invention eliminates the need for bulky free-space state preparation components and complex interferometer networks, enabling the direct generation of N≥4 dimensional spin-orbit photonic quantum states on a chip without the need for external state modulation devices, thus reducing system complexity. All generated quantum states exhibit consistent spatiotemporal characteristics, reducing transmission and detection error rates. Tunable non-Hermitian coupling enables nanosecond-level rapid switching of quantum states, improving key generation rates. Integrating a high-dimensional quantum state transmitter onto a micrometer-scale chip reduces the size by several orders of magnitude compared to free-space systems, laying the foundation for chip-based QKD terminals and large-scale production.

[0034] In some embodiments, the optical resonant cavity 1012 is a micro-ring resonant cavity.

[0035] like Figure 2 As shown, the inner wall of the micro-ring resonator is etched with an angular grating 10121. The angular grating 10121 is used to couple the whispering gallery mode in the cavity into an outgoing beam perpendicular to the plane of the semiconductor substrate 1011, and to give the outgoing beam a defined orbital angular momentum quantum number.

[0036] Specifically, the period of the angular grating 10121 is determined by the target orbital angular momentum mode, which is used to selectively couple a specific whispering galvanic mode in the cavity into a beam emitted in the vertical direction and to give it a defined OAM (Orbital Angular Momentum) quantum number (e.g., ℓ=±2).

[0037] It is worth mentioning that, in principle, the non-Hermitian coupled microcavity architecture can be extended to 8-dimensional, 16-dimensional or even higher-dimensional QKD systems by increasing the number of microrings and optimizing the coupling network, thereby continuously improving the single-photon information capacity.

[0038] In this embodiment, the angular grating 10121 etched on the inner wall of the micro-ring resonator can realize efficient vertical emission of the whispering-gallery mode on a single integrated chip and deterministically endow the emitted beam with the quantum number of orbital angular momentum without the need for external modulation devices, laying the core foundation for the direct generation of spin-orbit high-dimensional quantum states.

[0039] In some embodiments, the coupling unit 1013 includes a plurality of helical waveguides 10131 and a plurality of pump electrodes 10132.

[0040] The helical waveguide 10131 is evanescently coupled or directly connected to two micro-ring resonators at different spatial locations to inject pump energy into the micro-ring resonators. By modulating the pump intensity and spatial distribution, the non-Hermitian coupling between the micro-ring resonators is dynamically controlled to lasing out spin-orbit photon quantum states.

[0041] Specifically, the helical waveguide 10131 dynamically modulates the non-Hermitian gauge field by controlling the pump, thereby directly lasing out the spin-orbit quantum state of the target.

[0042] Pump electrodes 10132 and helical waveguides 10131 are connected in a one-to-one correspondence and are used to inject pump current into the corresponding helical waveguides 10131.

[0043] As an example, by independently changing the injection current of the four pump electrodes 10132, the complex coupling coefficient between the two microring resonators can be dynamically controlled, thereby changing the amplitude and phase distribution of the optical field within the microring, and ultimately realizing the lasing and switching of high-dimensional spin-orbit photon quantum states.

[0044] In this embodiment, the non-Hermitian coupling between micro-ring resonators can be precisely controlled by employing a helical waveguide 10131, directly lasing spin-orbit photon quantum states to achieve dynamic switching of quantum states, thereby improving device integration and operational stability. Furthermore, high-dimensional states can be controlled with only a few pump electrodes 10132, resulting in a complexity far lower than traditional interferometer solutions.

[0045] In some embodiments, the number of helical waveguides 10131 is four, and they are arranged on the semiconductor substrate 1011 in a 90-degree rotational symmetry manner.

[0046] Specifically, such as Figure 1 As shown, the four spiral waveguides 10131 are arranged in two columns with complete vertical symmetry: the upper left and upper right spiral waveguides 10131 are coupled to the upper regions of the two micro-ring resonators respectively; the lower left and lower right spiral waveguides 10131 are coupled to the lower regions of the two micro-ring resonators respectively.

[0047] As an example, the spin-orbit microlaser of this invention can employ a dual-microring resonator structure. Each microring resonator supports two sets of orthogonal polarization modes: left-handed and right-handed circular polarization. Combined with the orbital angular momentum mode generated by the mode selection of the angular grating 10121, the entire spin-orbit microlaser can achieve lasing of four spin-orbit eigenmodes, denoted as: |ψ1>=|+2,↺>, |ψ2>=|-2,↻>, |ψ3>=|-2,↺>, and |ψ4>=|+2,↻>. These four modes constitute a four-dimensional Hilbert space. By applying pumps with different spatial distributions and intensities to the four helical waveguides 10131, non-Hermitian coupling between modes can be dynamically introduced and controlled. This coupling is equivalent to applying a programmable "gauge field". By pre-calibrating a set of pump patterns, arbitrary quantum states in this four-dimensional space can be directly and coherently lased. In particular, it can stably las-emit all eight states of two sets of non-orthogonal bases used in the 4D BB84 protocol.

[0048] It is worth mentioning that the spin-orbit microlaser in the above example has the following key characteristics:

[0049] 1. Direct generation of quantum states: The quantum state is generated by the laser itself, without the need for a subsequent, complex state preparation optical system.

[0050] 2. Dynamic reconstruction of quantum states: Quantum states can be switched on the nanosecond scale by changing the electric pump current or the external optical pump pattern.

[0051] 3. Same-velocity propagation: Since all four eigenmodes share the same spatial and temporal characteristics of the resonant cavity, any quantum state generated by their linear superposition has the exact same spatial intensity distribution, wavefront phase, and pulse time-domain shape. Therefore, they propagate in free space at the same phase velocity and group velocity, completely avoiding relative phase drift and pulse broadening (walk-off) during transmission.

[0052] Next, the fabrication and basic characterization of the spin-orbit microlaser 101 in the embodiments of the present invention will be described in detail:

[0053] Fabrication process: On a 200nm thick InGaAsP multi-quantum-well epitaxial wafer, electron beam lithography and inductively coupled plasma deep etching were used to fabricate a wafer as shown in the image. Figure 1 The spin-orbit microlaser 101 shown is shown.

[0054] Key parameters: microring radius R = 20 μm, waveguide width 500 nm, inner wall angular grating period 620 nm, etching depth 150 nm. Four helical waveguides 10131 are arranged in a 90-degree rotational symmetry manner. The overall chip size is 250 μm × 250 μm.

[0055] Test System: A 1064nm nanosecond pulsed laser was used as the optical pump source. A programmable two-dimensional pump pattern was generated by a spatial light modulator and focused by an objective lens onto four spiral waveguide 10131 regions on the chip. The microlaser emitted light at 1547nm. The emitted light was then bandpass filtered and attenuated before entering the free-space channel.

[0056] Results: By loading eight different pre-calibrated pump patterns, all eight quantum states of the two defined sets of 4D MUBs were successfully and stably lased. The system was fully characterized, and an 8×8 probability probe matrix was measured (see [link to relevant documentation]). Figure 3 The calculated average qubit error rate is 12.0%, significantly lower than the 18.9% security threshold of the four-dimensional BB84 protocol against coherent attacks. The fidelity between the experimental matrix and the theoretical ideal matrix reaches 0.967, demonstrating the high fidelity of quantum state generation and manipulation.

[0057] Experimental data verified the system's low error rate performance and long-distance key generation capability. In the figure, 1.0 corresponds to the probability of the ground state or maximum emission efficiency; 0.5 represents the probability of the superposition state or partial emission efficiency, reflecting quantum interference effects; and 0.0 represents the probability of the excited state or zero emission, used to describe decay or blocking states.

[0058] It should be noted that in quantum key distribution, these values ​​are related to the probability of photon emission or the bit error rate calibration.

[0059] In addition, the present invention also provides a high-dimensional quantum key distribution system, such as Figure 4 As shown, the high-dimensional quantum key distribution system includes: a transmitter 10, a receiver 20, a classical channel 30, a quantum channel 40, and a control and processing unit 50.

[0060] The transmitter 10 includes the aforementioned spin-orbit microlaser 101 and adjustable attenuator 102.

[0061] The spin-orbit microlaser 101 is used to generate spin-orbit photon quantum states in N≥4-dimensional Hilbert space, and dynamically generates and switches quantum states by controlling the non-Hermitian coupling between internal modes, and outputs corresponding lasing pulses.

[0062] The adjustable attenuator 102 is connected to the spin-orbit microlaser 101 to modulate the lasing pulse into a weakly coherent pulse containing a signal state, a decoy state, and a vacuum state.

[0063] Specifically, the input of the adjustable attenuator 102 is coupled to the output of the spin-orbit microlaser 101 via a single-mode fiber.

[0064] As an example, the adjustable attenuator 102 can modulate the lasing pulse into three intensity levels—signal state, decoy state, and vacuum state—according to a preset decoy state protocol timing sequence under the control of the control and processing unit 50.

[0065] The receiver 20 is connected to the transmitter 10 through a classical channel 30 and a quantum channel 40, and includes a spin-orbit mode sorter 201 and one or more single-photon detectors 202.

[0066] The spin-orbit mode sorter 201 is used for mode sorting of weakly coherent pulses.

[0067] Preferably, the spin-orbit mode sorter 201 can be an optical element based on diffraction optics or mode transformation.

[0068] The single-photon detector 202 is connected to the spin-orbit mode sorter 201 to perform single-photon detection on the sorted photons and output a detection event signal.

[0069] Specifically, the single-photon detector 202 is connected one-to-one with each output channel of the spin-orbit mode sorter 201 to detect the sorted single photons, convert the optical signal into an electrical signal, and output the detection event signal to the control and processing unit 50.

[0070] The control and processing unit 50 is connected to the transmitter 10 and the receiver 20 respectively. It is used to control the pump sequence and intensity of the transmitter 10, and generate a security key by performing post-processing protocols such as basis vector comparison, decoy state analysis, error correction and privacy amplification through the classical channel 30 based on the detection event signal.

[0071] It should be noted that, for the transmitter 10, the control and processing unit 50 controls the four pump electrodes 10132 of the spin-orbit microlaser 101 through the generated high-precision pump current timing signal to achieve dynamic generation and switching of high-dimensional quantum states; it also generates weakly coherent pulses of signal state, decoy state, and vacuum state according to the decoy state protocol timing by controlling the attenuation of the adjustable attenuator 102. For the receiver 20, the control and processing unit 50 achieves random switching between two sets of non-orthogonal measurement bases by controlling the measurement base selection of the spin-orbit mode sorter 201; it also records the time, channel, and measurement base information of each detection event by acquiring the detection event signal output by the single-photon detector 202.

[0072] The quantum channel 40 can be a free space or fiber optic link connecting the transmitter 10 and the receiver 20, used to transmit weak coherent pulses carrying quantum information.

[0073] The classical channel 30 is used to transmit control signals, synchronization signals, and classical information required for key post-processing. This classical information may include the pump sequence synchronization signal from the transmitter 10, the measurement basis selection signal from the receiver 20, basis vector comparison data, error correction and verification data, and privacy amplification parameters.

[0074] The high-dimensional quantum key distribution system of this invention directly generates high-dimensional spin-orbit quantum states through a spin-orbit microlaser, eliminating the need for external complex state modulation devices, thus simplifying the system structure and improving integration and stability. Nanosecond-level quantum state switching is achieved through electrically controlled non-Hermitian coupling, increasing the key generation rate, and ensuring consistent transmission characteristics across all quantum states, thereby reducing the system's bit error rate.

[0075] In some embodiments, the different spin-orbit photon quantum states generated by the spin-orbit microlaser 101 have the same spatial mode and temporal waveform, and propagate in the transmission medium at the same phase velocity and group velocity.

[0076] In this embodiment, the quantum state's "same speed propagation" characteristic greatly reduces the system's requirements for optical path alignment, making it insensitive to environmental disturbances.

[0077] In some embodiments, the transmitter 10 further includes a decoy state generation and control module.

[0078] The decoy state generation and control module is connected to the adjustable attenuator 102 and is used to adjust the attenuation of the adjustable attenuator 102 to alternately output signal state, decoy state and vacuum state pulses with different average photon numbers.

[0079] Specifically, the intensity μ of the signal state is greater than the intensity ν of the decoy state, and the intensity of the decoy state is greater than the intensity of the vacuum state.

[0080] The intensity of the signal state is less than 1, and the intensity of the vacuum state is equal to 0, i.e., 0 < ν < μ < 1.

[0081] In this embodiment, the decoy state generation and control module can effectively resist photon number splitting attacks by adjusting the adjustable attenuator 102 to alternately output three-state pulses, thus ensuring the unconditional security of the high-dimensional quantum key distribution system.

[0082] Next, the high-dimensional quantum key distribution system of the present invention will be described using real-time decoy state HD-QKD and distance simulation experiments:

[0083] Experimental parameters: The average photon number in the signal state was set to μ=0.18, and the average photon number in the decoy state was set to ν=0.09. An adjustable neutral density filter was inserted in the free-space optical path between the transmitter 10 and the receiver 20 to simulate additional channel loss from 0dB to 8dB.

[0084] Experimental procedure: Under each loss setting, a continuous key distribution experiment was conducted for 20 to 80 minutes, and the time stamps and strength stamps of all probe events were recorded.

[0085] Data Analysis and Results: Post-processing was performed on each dataset to calculate the security key rate. Results are as follows: Figure 5 As shown, even with an equivalent channel loss of up to 8 dB (corresponding to atmospheric transmission of approximately 80 km in clear weather), the system can still generate a positive secure key rate. Simultaneously, the measured QBER remains below the security threshold under all loss conditions. Experimental data points are compared with those based on actual system parameters (detector efficiency η≈0.011, dark count rate Y0≈1.7×10⁻⁻⁻⁴). 5 The theoretical simulation curves show a high degree of agreement, verifying the effectiveness of the system model and its potential for long-distance operation.

[0086] Next, long-term stability testing will be conducted on the above system:

[0087] Test conditions: The transmitter 10 and receiver 20 were fixed on the experimental platform, all adjustable attenuators 102 were removed, and a stable direct optical path connection was established. The system ran continuously for 200 minutes, performing real-time key distribution.

[0088] Monitoring metrics: The average QBER (Quantum Bit Error Rate) and signal state gain are calculated in real-time within a 5-minute time window. .

[0089] Results: As shown in Figures 6(a)-(b), the system performance remained highly stable throughout the testing period. The mean QBER was 0.134, and the standard deviation was 0.014; the mean... The value is (3.78±0.12)×10⁻³. No significant performance degradation or fluctuation was observed, which fully demonstrates that the transmitter based on the integrated microlaser has excellent long-term alignment stability and output consistency, which is difficult to achieve with traditional free-space systems.

[0090] In addition, the present invention also provides a high-dimensional quantum key distribution method, which is applied to the above-mentioned high-dimensional quantum key distribution system. The high-dimensional quantum key distribution method includes:

[0091] S1, the control and processing unit controls the spin-orbit microlaser to generate spin-orbit photon quantum states in N≥4-dimensional Hilbert space, and dynamically generates and switches quantum states by regulating the non-Hermitian coupling between modes inside the spin-orbit microlaser, and outputs corresponding lasing pulses.

[0092] S2, the adjustable attenuator modulates the lasing pulse into a weakly coherent pulse containing signal state, decoy state and vacuum state.

[0093] S3, the transmitter transmits weakly coherent pulses to the receiver through a quantum channel.

[0094] S4, the spin-orbit mode sorter, performs mode sorting on weakly coherent pulses.

[0095] S5, one or more single-photon detectors perform single-photon detection on the sorted photons and output the detection event signal to the control and processing unit.

[0096] S6, the control and processing unit generates a security key based on the detected event signal and by performing post-processing protocols such as basis vector comparison, decoy state analysis, error correction, and privacy amplification through a classical channel.

[0097] It should be noted that other specific implementations of the high-dimensional quantum key distribution method of the present invention can be found in the specific implementations of the high-dimensional quantum key distribution system of the above embodiments of the present invention.

[0098] Next, taking the running of the improved 4D BB84 protocol and the integration of decoy state methods to resist photon number splitting attacks as an example, the specific process of this method will be explained:

[0099] 1. The transmitter randomly selects one of two predefined non-orthogonal bases and randomly selects a 4D quantum state under that base for emission.

[0100] 2. At the same time, the transmitter randomly sets the intensity of each pulse to one of three levels: signal state, decoy state, and vacuum state.

[0101] 3. The receiver randomly selects a base pair to measure the received photons.

[0102] 4. In the post-processing stage, both parties disclose the intensity level and measurement basis used for all pulses, but retain specific state information and discard basis mismatch and undetected data.

[0103] 5. Using the count rate and bit error rate statistics of the signal state, decoy state, and vacuum state, estimate the gain and bit error rate contributed solely by the single photon pulse.

[0104] 6. Based on this estimate, calculate the unconditionally secure key rate, perform error correction and privacy amplification, and finally generate a secure key.

[0105] Although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above exemplary embodiments are merely illustrative and are not intended to limit the scope of this application. Various changes and modifications can be made therein by those skilled in the art without departing from the scope and spirit of this application. All such changes and modifications are intended to be included within the scope of this application as claimed in the appended claims.

[0106] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0107] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed.

[0108] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0109] Similarly, it should be understood that, in order to streamline this application and aid in understanding one or more of the various inventive aspects, features of this application may sometimes be grouped together in a single embodiment, figure, or description thereof in the description of exemplary embodiments of this application. However, this approach should not be construed as reflecting an intention that the claimed application requires more features than are expressly recited in each claim. Rather, as reflected in the corresponding claims, its inventive point lies in solving the corresponding technical problem with features fewer than all features of a single disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0110] Those skilled in the art will understand that, apart from the mutual exclusion of features, all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or elements of any method or apparatus so disclosed may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0111] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0112] The various component embodiments of this application can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some modules according to the embodiments of this application. This application can also be implemented as an apparatus program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such an implementation of this application can be stored on a computer-readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0113] It should be noted that the above embodiments are illustrative of this application and not limiting of it, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0114] The above description is merely a specific embodiment or illustration of the embodiments of this application. The scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A spin-orbit microlaser, characterized in that, include: Semiconductor substrate; At least two optical resonant cavities are located on the semiconductor substrate; Coupling units for introducing tunable non-Hermitian coupling between and / or within the optical resonant cavities.

2. The spin-orbit microlaser according to claim 1, characterized in that, The optical resonant cavity is a micro-ring resonant cavity; The inner wall of the micro-ring resonator is etched with an angular grating, which is used to couple the whispering gallery mode in the cavity into an outgoing beam perpendicular to the plane of the semiconductor substrate, and to give the outgoing beam a defined orbital angular momentum quantum number.

3. The spin-orbit microlaser according to claim 2, characterized in that, The coupling unit includes multiple helical waveguides and multiple pump electrodes; The spiral waveguide is evanescently coupled or directly connected to different spatial positions of the two micro-ring resonators to inject pump energy into the micro-ring resonators. By adjusting the pump intensity and spatial distribution, the non-Hermitian coupling between the micro-ring resonators is dynamically controlled to lasing out spin-orbit photon quantum states. The pump electrode is connected to each of the spiral waveguides in a one-to-one correspondence, and is used to inject pump current into the corresponding spiral waveguide.

4. The spin-orbit microlaser according to claim 3, characterized in that, The number of spiral waveguides is four, and they are arranged on the semiconductor substrate in a 90-degree rotational symmetry manner.

5. A high-dimensional quantum key distribution system, characterized in that, The system includes: a transmitter, a receiver, a classical channel, a quantum channel, and a control and processing unit; The transmitting end includes a spin-orbit microlaser and an adjustable attenuator as described in any one of claims 1-4; The spin-orbit microlaser is used to generate spin-orbit photon quantum states in N≥4-dimensional Hilbert space, and dynamically generates and switches quantum states by controlling the non-Hermitian coupling between internal modes, and outputs corresponding lasing pulses. The adjustable attenuator, connected to the spin-orbit microlaser, is used to modulate the lasing pulse into a weakly coherent pulse containing a signal state, a decoy state, and a vacuum state. The receiver, connected to the transmitter via the classical channel and the quantum channel, includes: a spin-orbit mode sorter and one or more single-photon detectors; The spin-orbit mode sorter is used to perform mode sorting on the weakly coherent pulses; The single-photon detector is connected to the spin-orbit mode sorter and is used to perform single-photon detection on the sorted photons and output a detection event signal. The control and processing unit is connected to the transmitter and the receiver respectively, and is used to control the pump sequence and intensity of the transmitter, and generate a security key by performing a post-processing protocol of basis vector comparison, decoy state analysis, error correction and privacy amplification based on the detection event signal and through the classical channel.

6. The high-dimensional quantum key distribution system according to claim 5, characterized in that, The different spin-orbit photon quantum states generated by the spin-orbit microlaser have the same spatial mode and temporal waveform, and propagate in the transmission medium with the same phase velocity and group velocity.

7. The high-dimensional quantum key distribution system according to claim 5, characterized in that, The transmitter also includes: a decoy state generation and control module; The decoy state generation and control module is connected to the adjustable attenuator and is used to adjust the attenuation of the adjustable attenuator to alternately output signal state, decoy state and vacuum state pulses with different average photon numbers.

8. The high-dimensional quantum key distribution system according to claim 5, characterized in that, The strength of the signal state is greater than the strength of the decoy state, and the strength of the decoy state is greater than the strength of the vacuum state; The intensity of the signal state is less than 1, and the intensity of the vacuum state is equal to 0.

9. A high-dimensional quantum key distribution method, characterized in that, This method is applied to a high-dimensional quantum key distribution system according to any one of claims 5-8, the method comprising: The control and processing unit controls the spin-orbit microlaser to generate spin-orbit photon quantum states in N≥4-dimensional Hilbert space, and dynamically generates and switches quantum states by regulating the non-Hermitian coupling between the modes inside the spin-orbit microlaser, and outputs corresponding lasing pulses. The adjustable attenuator modulates the lasing pulse into a weakly coherent pulse that includes a signal state, a decoy state, and a vacuum state; The transmitter transmits the weakly coherent pulse to the receiver via a quantum channel; A spin-orbit mode sorter performs mode sorting on the weakly coherent pulses; One or more single-photon detectors perform single-photon detection on the sorted photons and output detection event signals to the control and processing unit; The control and processing unit generates a security key based on the detected event signal and by performing post-processing protocols such as basis vector comparison, decoy state analysis, error correction, and privacy amplification through the classical channel.

Images