Quantum key distribution device, receiver and quantum key distribution system

Abstract

This application provides a quantum key distribution device, a receiver, and a quantum key distribution system, which can be applied in the field of quantum communication network technology. The quantum key distribution device includes a light source, a modulator, a processor, and an optical phased array. The light source is configured to generate laser light and split it into pilot light and signal light. The modulator is configured to modulate the signal light to generate quantum signal light. The processor is configured to generate a phase control signal. The optical phased array is configured to transmit the pilot light and quantum signal light to the receiver located at a spatial orientation corresponding to the phase control signal, under the control of the phase control signal. The receiver receives the pilot light and quantum signal light and generates local oscillator light using a local laser. A detector coherently detects the pilot light, quantum signal light, and local oscillator light, outputting a detection electrical signal. The processor obtains the quantum key based on the detection electrical signal.

Description

Technical Field

[0001] At least one embodiment of this application relates to the field of quantum communication network technology, specifically to a quantum key distribution device, a receiver, and a quantum key distribution system. Background Technology

[0002] Quantum key distribution (QKD) provides a key generation method for communicating parties based on quantum state transmission and measurement processes, and has application requirements in high-security communication, temporary communication access, mobile platform communication, and free-space communication scenarios. In practical applications, QKD can be implemented based on fixed transmission media or free-space links. Different technical paths differ in terms of deployment flexibility, link establishment methods, terminal size, pointing control methods, and multi-user access capabilities. In free-space access scenarios, communication objects may be located in different spatial orientations, and the number and positional relationships of access objects may change over time, affecting the stability of system operation due to link pointing, link maintenance, and access switching.

[0003] Fixed-link quantum key distribution relies on pre-deployed transmission paths, resulting in insufficient deployment flexibility. Point-to-point free-space quantum key distribution, while capable of establishing free-space links, suffers from poor network scalability and scheduling flexibility during multi-receiver switching. Mechanical pointing control, though capable of adjusting beam direction, is bulky, has high inertia, slow response, and poor continuity during multi-target switching. For multi-receiver free-space access scenarios, none of the above methods can meet the practical requirements of dynamic access, continuous link switching, and miniaturized deployment. Summary of the Invention

[0004] In view of the above problems, this application provides a quantum key distribution device, a receiver, and a quantum key distribution system.

[0005] According to a first aspect of this application, a quantum key distribution device is provided. The quantum key distribution device includes a light source, a modulator, a processor, and an optical phased array.

[0006] The light source is configured to generate laser light and split the laser light into pilot light and signal light.

[0007] The modulator is configured to modulate the signal light to generate quantum signal light.

[0008] The processor is configured to generate phase control signals.

[0009] An optical phased array is configured to send pilot light and quantum signal light to a receiver located at a spatial orientation corresponding to the phase control signal under the control of a phase control signal, so that the receiver can obtain a quantum key based on the pilot light and quantum signal light. The quantum key is obtained by coherent detection between the quantum signal light and the local oscillator light in the receiver that is phase-compensated based on the pilot light.

[0010] According to an embodiment of this application, the light source includes a laser and a beam splitter. The laser is configured to generate laser light. The beam splitter is configured to split the laser beam into pilot light and signal light. The energy of the pilot light is greater than the energy of the signal light.

[0011] According to embodiments of this application, the modulator includes an orthogonal modulator. The quantum key distribution device further includes a quantum random number generator and an attenuator. The quantum random number generator is configured to generate quantum random numbers. The orthogonal modulator is configured to modulate the signal light according to the quantum random numbers. The attenuator is configured to attenuate the modulated signal light to obtain quantum signal light.

[0012] According to embodiments of this application, an optical phased array is configured to: transmit pilot light in a first time period and transmit quantum signal light in a second time period different from the first time period, or transmit pilot light in a first polarization state and simultaneously transmit quantum signal light in a second polarization state different from the first polarization state.

[0013] According to an embodiment of this application, the processor is further configured to generate phase control signals corresponding to multiple different spatial orientations at different time periods, so as to send pilot light and quantum signal light to receivers located at multiple different spatial orientations at different time periods.

[0014] According to embodiments of this application, the processor is also configured to transmit different preset numbers of quantum frames to multiple receivers in different spatial orientations.

[0015] According to an embodiment of this application, the processor is further configured to generate a phase compensation signal based on the combined distribution of atmospheric wavefront distortion and optical phased array hardware errors, so that the optical phased array performs wavefront distortion compensation on multiple array elements of the optical phased array under the control of the phase compensation signal.

[0016] According to a second aspect of this application, a receiving end is provided. The receiving end includes a signal receiver, a local laser, a detector, and a processing unit.

[0017] The signal receiver is configured to receive pilot light and quantum signal light transmitted by the quantum key distribution device, wherein the pilot light and quantum signal light are sourced from the same light source, and the quantum signal light is modulated.

[0018] The local laser is configured to generate native oscillator light.

[0019] The detector is configured to coherently detect the pilot light, quantum signal light, and local oscillator light, and output a detection electrical signal.

[0020] The processing unit is configured to obtain a quantum key based on the probe electrical signal; wherein the quantum key is obtained by coherent detection between the quantum signal light and the local oscillator light in the receiver, which is phase-compensated based on the pilot light.

[0021] According to an embodiment of this application, the processing unit is further configured to obtain a quantum key by: performing frequency offset estimation and phase compensation based on information about the pilot light in the probe electrical signal; obtaining an initial quantum key based on interference information about the quantum signal light and the local oscillator light in the probe electrical signal; and obtaining the quantum key through classical channel authentication.

[0022] According to a third aspect of this application, a quantum key distribution system is provided. The quantum key distribution system includes the aforementioned quantum key distribution device and the aforementioned receiver.

[0023] According to embodiments of this application, the light source divides the laser into pilot light and signal light. The signal light is modulated to generate quantum signal light. The processor controls the optical phased array to transmit both types of light beams, achieving beam pointing adjustment without mechanical components, adapting to the spatial orientation of multiple receivers. The same light source allows the receiver to use the pilot light for phase compensation, reducing phase drift and frequency offset effects and ensuring quantum key generation. The processor can transmit different numbers of quantum frames to multiple receivers at different times, realizing time-slot switching and frame number adjustment, improving the flexibility of multi-terminal access scheduling. In addition, the processor can generate phase compensation signals based on atmospheric distortion and hardware errors, controlling the optical phased array to perform wavefront distortion compensation, maintaining the receiver's reception stability in free-space channels. Attached Figure Description

[0024] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0025] Figure 1 A schematic diagram of the structure of a quantum key distribution system according to an embodiment of this application is shown.

[0026] Figure 2 The schematic diagram illustrates the principle of a free-space continuous-variable quantum access network based on an optical phased array according to an embodiment of this application.

[0027] Figure 3 A schematic diagram of the structure of an optical phased array according to an embodiment of this application is shown.

[0028] Figure 4A schematic diagram of the structure of an optical phased array according to an embodiment of this application is shown.

[0029] Figure 5 A schematic diagram of a receiving end according to an embodiment of this application is shown;

[0030] Explanation of reference numerals in the attached figures:

[0031] Quantum key distribution device-1; transmit beam generation component-11; host computer-12; optical phased array-13; beam splitter component-131; controller-132; output component-133; array unit-1331; receiver-2; signal receiver-21; local laser-22; detector-23; processing unit-24; output port-D; phase shifter-PS. Detailed Implementation

[0032] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a comprehensive understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms "comprising," "including," etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0034] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0035] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0036] This application provides a quantum key distribution device. The quantum key distribution device includes a light source, a modulator, a processor, and an optical phased array.

[0037] A light source is configured to generate laser light and split it into pilot light and signal light. A modulator is configured to modulate the signal light to generate quantum signal light. A processor is configured to generate a phase control signal. An optical phased array is configured, under the control of the phase control signal, to send the pilot light and quantum signal light to a receiver located at a spatial orientation corresponding to the phase control signal, so that the receiver obtains a quantum key based on the pilot light and quantum signal light. The quantum key is obtained based on coherent detection between the quantum signal light and the local oscillator light at the receiver, which is phase-compensated based on the pilot light.

[0038] In embodiments of this application, the light source is used to provide the basic optical signal for generating pilot light and quantum signal light. The light source can be an optical component capable of generating laser light and splitting or branching the laser output. Exemplarily, the light source may include at least one of a laser, a beam splitter, an optical fiber coupler, and a power conditioner, and may also include an optical combination structure capable of providing light input to subsequent modulators and optical phased arrays.

[0039] In embodiments of this application, pilot light is used to provide phase reference recovery information to the receiving end. Pilot light can be a reference light signal that is from the same source as the quantum signal light or has a phase correlation relationship. For example, pilot light can be formed by splitting the laser output from a laser using a beam splitter, and then transmitted to the receiving end together with the quantum signal light using time-division multiplexing or polarization multiplexing.

[0040] In embodiments of this application, the signal light is used to form quantum signal light after modulation. The signal light can be a light signal to be modulated, output from a light source and input to a modulator. Exemplarily, the signal light can be a continuous wave light signal, or a light signal that has been intensity-adjusted or optically path-selected.

[0041] In embodiments of this application, quantum signal light is used to carry information required for quantum key distribution. The quantum signal light can be an optical signal obtained by modulating signal light with a modulator. Exemplarily, the quantum signal light can be a continuous variable quantum signal light obtained by loading quantum random numbers onto an orthogonal modulator, or it can be a weak optical signal that meets the requirements for quantum key distribution after attenuation processing.

[0042] In embodiments of this application, the processor is used to generate phase control signals for controlling an optical phased array. The processor may be a computing or control unit capable of generating phase control information based on the spatial orientation of the receiver, access scheduling information, or beam pointing requirements. Exemplarily, the processor may include a host computer, a microprocessor, a digital signal processor, a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or a combination of the above devices.

[0043] In embodiments of this application, a phase control signal is used to control the phase state of an optical phased array. The phase control signal can be a control signal capable of enabling the optical phased array to form a target wavefront distribution. Exemplarily, the phase control signal can be a phase control matrix, array element phase loading values, or digital control data capable of controlling the phase difference between multiple array elements.

[0044] In embodiments of this application, an optical phased array is used to change the emission directions of pilot light and quantum signal light according to a phase control signal. The optical phased array can be an optical emission structure comprising multiple array units capable of phase modulation. Exemplarily, the optical phased array may include a beam splitter, a controller, and an output component; the output component may include multiple array units, each of which can output a phase-modulated optical signal.

[0045] In embodiments of this application, spatial orientation is used to represent the free-space position and direction of the receiver relative to the quantum key distribution device. Spatial orientation can be a beam pointing target determined by the receiver's position, angle, orientation information, or spatial coordinate information. For example, spatial orientation can correspond to one receiver or any target receiver among multiple receivers.

[0046] Figure 1 A schematic diagram of the structure of a quantum key distribution system according to an embodiment of this application is shown.

[0047] like Figure 1 As shown, the quantum key distribution device 1 can transmit a transmission beam to the receiver 2 located at a corresponding spatial orientation. The transmission beam may include pilot light and quantum signal light. The quantum key distribution device 1 may include a transmission beam generation component 11, a processor 12, and an optical phased array 14. The transmission beam generation component 11 can be used to generate a transmission beam including pilot light and quantum signal light. The processor 12 is used to generate a phase control signal. The optical phased array 14 can transmit the transmission beam to the receiver 2 at the corresponding spatial orientation under the control of the phase control signal.

[0048] In embodiments of this application, the transmit beam generating component 11 may include at least a portion of the structure of a light source 111 and a modulator 112. The transmit beam generated by the transmit beam generating component 11 includes pilot light and quantum signal light. The optical phased array 13 adjusts the wavefront distribution of the transmit beam according to the phase control signal, so that the pilot light and quantum signal light are pointed to the corresponding receiver 2.

[0049] Figure 2 The schematic diagram illustrates the principle of a free-space continuous-variable quantum access network based on an optical phased array according to an embodiment of this application.

[0050] like Figure 2As shown, at the central node Alice, laser 1, after being split by a beam splitter, can form pilot light and signal light. The signal light, based on quantum random numbers generated by a quantum random number generator, is modulated by an orthogonal modulator and then processed by an attenuator to form quantum signal light. After the pilot light and quantum signal light enter the optical phased array, they can be directed to the corresponding receiver Bobi under the control of the phase control signal generated by the phase control component. The receiver Bobi receives the optical signal transmitted from free space through a receiving telescope and obtains the detection electrical signal based on the local oscillator light generated by the local laser 2 through a heterodyne detection structure.

[0051] According to a specific embodiment of this application, laser light is generated from the same light source and divided into pilot light and signal light. The signal light is modulated to carry quantum key information. A processor generates a phase control signal, and an optical phased array simultaneously transmits pilot light and quantum signal light to the corresponding spatial orientation, so that the transmission direction is achieved by phase control. Since the transmission direction of the optical phased array can change with the phase control signal, the quantum key distribution device can switch beam pointing between receivers at different spatial orientations. Because the pilot light and quantum signal light are transmitted together, the receiver can perform phase reference recovery based on the pilot light and obtain the quantum key based on the quantum signal light. Therefore, according to the embodiments of this disclosure, quantum key distribution in free space scenarios can be supported and the access requirements of multiple spatial orientation receivers can be adapted.

[0052] In some embodiments of this application, the light source includes a laser and a beam splitter. The laser is configured to generate laser light. The beam splitter is configured to split the laser light into pilot light and signal light. The energy of the pilot light is greater than the energy of the signal light.

[0053] In embodiments of this application, a laser is used to generate a basic output of a light source. The laser can be a device capable of generating coherent laser light. Exemplarily, the laser can be a narrow-linewidth laser, a continuous-wave laser, or other laser generating device suitable for quantum key distribution systems.

[0054] In embodiments of this application, a beam splitter is used to split a laser beam into pilot light and signal light. The beam splitter can be an optical device capable of splitting an input laser beam into at least two output beams according to a predetermined power distribution relationship. Exemplarily, the beam splitter can be a fiber optic beam splitter, a spatial optical beam splitter, an integrated optical waveguide beam splitter, or other structures capable of achieving optical power distribution.

[0055] In embodiments of this application, the energy of the pilot light is greater than that of the signal light, which makes the pilot light easier to identify at the receiving end and for phase reference recovery. The pilot light's energy being greater than the signal light's energy can be achieved by the pilot light's power, pulse energy, or average intensity being higher than the corresponding parameters of the signal light. For example, the beam splitter can employ a non-uniform beam splitting method, allocating a higher proportion of laser energy to the pilot light path and a lower proportion to the signal light path.

[0056] like Figure 2 As shown, laser 1 outputs laser light, and a beam splitter splits the laser light into two paths: one path forms a pilot beam, and the other forms a signal beam. The pilot beam can directly participate in subsequent multiplexing and transmission without quantum random number modulation, while the signal beam can enter an orthogonal modulator and be modulated into quantum signal light. Through this optical path configuration, the pilot beam and the signal beam originate from the same laser 1, enabling the receiver to use the phase reference information provided by the pilot beam to compensate for the coherent detection of the quantum signal beam.

[0057] By generating laser light and splitting it into pilot and signal beams using a beam splitter, both a reference optical path and a quantum signal optical path can be obtained simultaneously from the same light source. Since the pilot and signal beams originate from the same source, the pilot beam provides phase reference information associated with the quantum signal beam. Furthermore, the pilot beam has higher energy than the signal beam, reducing the difficulty for the receiver to extract pilot-related information from the received signal, thus providing a signal basis for frequency offset estimation and phase compensation. Therefore, this configuration of the light source supports phase reference recovery before coherent detection of the quantum signal beam at the receiver and provides the receiving conditions for subsequent quantum key generation.

[0058] In some embodiments of this application, the modulator includes an orthogonal modulator. The quantum key distribution device further includes a quantum random number generator and an attenuator. The quantum random number generator is configured to generate quantum random numbers. The orthogonal modulator is configured to modulate the signal light according to the quantum random numbers. The attenuator is configured to attenuate the modulated signal light to obtain quantum signal light.

[0059] In embodiments of this application, a quadrature modulator is used to modulate the quadrature components of the signal light. The quadrature modulator can be a modulation device capable of independently modulating the in-phase and quadrature components of the optical field. Exemplarily, the quadrature modulator can be an I / Q modulator, or an integrated modulation structure capable of implementing in-phase and quadrature branch modulation.

[0060] In embodiments of this application, a quantum random number generator is used to generate random numbers required for modulating signal light. The quantum random number generator can be a device or module that outputs random numbers based on a quantum random process. Exemplarily, the quantum random number generator can output random number pairs for in-phase component modulation and quadrature component modulation, or it can output random modulation data for driving a quadrature modulator.

[0061] In embodiments of this application, an attenuator is used to attenuate modulated signal light. The attenuator can be an optical device that reduces the energy, power, or average photon number of the optical signal. Exemplarily, the attenuator can be an adjustable optical attenuator, a fixed optical attenuator, or an integrated optical attenuation structure.

[0062] like Figure 2 As shown, a quantum random number generator can generate quantum random numbers, and an orthogonal modulator can modulate the signal light according to these quantum random numbers. The signal light modulated by the orthogonal modulator can then enter an attenuator, which attenuates the modulated signal light to obtain quantum signal light. The quantum signal light then enters an optical phased array together with the pilot light and is transmitted to the receiver Bobi via a free-space channel.

[0063] In embodiments of this application, the quantum random number may include random numbers used to modulate the in-phase and quadrature components. The quadrature modulator can control the two quadrature components of the signal light according to the aforementioned random numbers, enabling the modulated signal light to carry the information required for continuous-variable quantum key distribution. After the attenuator attenuates the modulated signal light, it ensures that the quantum signal light meets the requirements for subsequent transmission and coherent detection.

[0064] Generating quantum random numbers using a quantum random number generator provides a basis for random modulation of signal light. Modulating the signal light using an orthogonal modulator based on these quantum random numbers allows the signal light to carry quantum key distribution information related to its in-phase and quadrature components. Attenuating the modulated signal light using an attenuator transforms it into quantum signal light. Since the quantum signal light is obtained by modulation and attenuation of quantum random numbers, the receiver can obtain a detection electrical signal related to the quantum signal light after coherent detection, thus providing a data basis for initial quantum key generation.

[0065] In some embodiments of this application, the optical phased array is configured to: transmit pilot light in a first time period and transmit quantum signal light in a second time period different from the first time period, or transmit pilot light in a first polarization state and simultaneously transmit quantum signal light in a second polarization state different from the first polarization state.

[0066] In embodiments of this application, a first time period is used to transmit pilot light. The first time period can be a time interval in the transmission sequence used to transmit phase reference information. Exemplarily, the first time period can be a pilot time slot in a quantum frame, or a reference light transmission period set before or after the transmission of quantum signal light.

[0067] In embodiments of this application, the second time period is used to transmit quantum signal light. The second time period can be a time interval in the transmission sequence used to transmit quantum signal information. Exemplarily, the second time period can be a quantum signal time slot in a quantum frame, or a transmission period that is adjacent to or spaced apart from the first time period.

[0068] In embodiments of this application, a first polarization state is used to carry pilot light, and a second polarization state is used to carry quantum signal light. The first polarization state and the second polarization state can be different from each other and distinguishable by the receiving end. For example, the first polarization state can be a horizontal polarization state, and the second polarization state can be a vertical polarization state; the first polarization state can also be a first circular polarization state, and the second polarization state can also be a second circular polarization state, as long as they can be used to distinguish between pilot light and quantum signal light.

[0069] In embodiments of this application, pilot light and quantum signal light can be transmitted together using time-division multiplexing. Time-division multiplexing is used to transmit pilot light and quantum signal light separately in different time intervals. Time-division multiplexing can be a transmission method that distinguishes between the two types of optical signals by allocating time resources. For example, an optical phased array can transmit pilot light at the beginning of a quantum frame and quantum signal light at the end; or it can transmit pilot light and quantum signal light separately in two adjacent transmission time slots.

[0070] In embodiments of this application, pilot light and quantum signal light can also be transmitted together using polarization multiplexing. Polarization multiplexing is used to distinguish pilot light and quantum signal light by different polarization states. Polarization multiplexing can be a transmission method that uses polarization dimensions to carry different optical signals within the same or overlapping time range. For example, pilot light can be transmitted in a first polarization state, and quantum signal light can be transmitted in a second polarization state. The receiving end can use a polarization separation structure to extract pilot light and quantum signal light separately.

[0071] like Figure 2 As shown, the pilot light and quantum signal light can undergo time-division multiplexing or polarization multiplexing before entering the optical phased array, or they can maintain the corresponding multiplexing relationship in the transmission path of the optical phased array. The optical phased array transmits the multiplexed pilot light and quantum signal light to the receiver Bobi. After receiving the two types of optical signals, the receiver Bobi can perform frequency offset estimation and phase compensation based on the pilot light, and generate a detection electrical signal based on the coherent detection results of the quantum signal light and the local oscillator light.

[0072] Since pilot light and quantum signal light can be distinguished by time or polarization, the receiver can perform phase reference recovery and quantum signal detection respectively, reducing the possibility of confusion between the two types of optical signal processing, and providing a signal distinction basis for the acquisition of probe electrical signals and the generation of quantum keys.

[0073] In some embodiments of this application, the processor is further configured to generate phase control signals corresponding to multiple different spatial orientations at different time periods, so as to send pilot light and quantum signal light to receivers located at multiple different spatial orientations at different time periods.

[0074] In the embodiments of this application, different time periods are used to correspond to the access times of different receiving ends. Different time periods can be transmission time intervals allocated by the processor for receiving ends in different spatial orientations. For example, a first receiving end can correspond to a first access time period, a second receiving end can correspond to a second access time period, and a third receiving end can correspond to a third access time period.

[0075] In embodiments of this application, multiple different spatial orientations are used to represent different directions of multiple receivers relative to the quantum key distribution device. These multiple different spatial orientations can be a set of beam-pointing targets formed by the positions, angles, or spatial coordinates of the multiple receivers. For example, the multiple receivers can be located at different azimuth angles, different elevation angles, or different free-space positions.

[0076] In embodiments of this application, the processor can generate a corresponding phase control signal based on the spatial orientation of the receiving end. The corresponding phase control signal can be a control signal that enables the optical phased array to transmit pilot light and quantum signal light to the corresponding receiving end. For example, the processor can generate a first phase control signal in a first time period, causing the optical phased array to point towards a first receiving end; and generate a second phase control signal in a second time period, causing the optical phased array to point towards a second receiving end.

[0077] like Figure 1 As shown, the quantum key distribution device 1 can transmit pilot light and quantum signal light to multiple receivers 2 at different spatial orientations via an optical phased array 13. Combined with... Figure 2 The central node Alice can direct the optical signal to the target receiver Bob1 through Bob8 using an optical phased array. After the processor loads different phase control signals at different times, the transmit beam of the optical phased array can be switched from the direction corresponding to one receiver to the direction corresponding to another receiver.

[0078] In embodiments of this application, multiple receivers can share a single quantum key distribution device. The quantum key distribution device transmits pilot light and quantum signal light to a first receiver during a first time period, transmits pilot light and quantum signal light to a second receiver during a second time period, and continues to transmit pilot light and quantum signal light to other receivers in subsequent time periods. Each receiver can receive the optical signal during its corresponding time period and obtain the quantum key based on the pilot light and quantum signal light.

[0079] According to embodiments of this disclosure, by combining time scheduling and phase control, the quantum key distribution device is equipped with the ability to connect multiple receivers and can reduce the need to configure an independent transmitter for each receiver.

[0080] In some embodiments of this application, the processor is also configured to transmit different preset numbers of quantum frames to multiple receivers in different spatial orientations.

[0081] In the embodiments of this application, a quantum frame is a transmission unit used to carry pilot light and quantum signal light. A quantum frame can be an optical signal transmission structure organized according to a preset timing sequence. Exemplarily, a quantum frame may include at least one of a pilot light transmission segment, a quantum signal light transmission segment, and a synchronization information segment, and may also include multiple quantum signal light pulses or multiple sampling units. A quantum frame is a standardized timing pulse data packet, composed of a synchronization control frame and a quantum bit payload paired together. The quantum frame achieves frame synchronization through hardware timing and can also be referred to as a hardware frame.

[0082] In embodiments of this application, the preset quantity is used to represent the number of quantum frames continuously transmitted to a certain receiving end. The preset quantity may be the number of frames determined by the processor based on the receiving end's needs, link status, or scheduling policy. For example, a first receiving end may correspond to a first preset quantity, and a second receiving end may correspond to a second preset quantity. The first preset quantity and the second preset quantity may be the same or different.

[0083] In embodiments of this application, transmitting different preset numbers of quantum frames to multiple receivers in different spatial orientations can be achieved by the quantum key distribution device not frequently switching frame by frame between each receiver, but by continuously sending a preset number of quantum frames to a receiver after completing beam pointing at that receiver, and then switching to the next receiver. For example, when the first receiver requires more quantum signal optical data, more quantum frames can be configured; when the second receiver has lower access requirements or a better link condition, fewer quantum frames can be configured.

[0084] like Figure 2As shown, the central node Alice can first point the optical phased array to Bob1 and send a preset number of hardware frames to Bob1; after completion, the processor updates the phase control signal, causing the optical phased array to point to Bob2, and sends another preset number of hardware frames to Bob2. The above process can be executed in a polling manner among multiple receiving ends.

[0085] In the embodiments of this application, the number of hardware frames can be determined according to a network scheduling strategy. The network scheduling strategy may consider the number of receivers, receiver priority, link status, access request volume, or key requirement. The processor can determine the preset number corresponding to different receivers based on the above information, and control the optical phased array to send the corresponding number of hardware frames in the corresponding time period.

[0086] Since optical phased arrays need to update phase control signals when switching receivers, switching receivers every few data transmissions could increase the switching interval. However, continuously transmitting a preset number of hardware frames in the direction corresponding to one receiver before switching to the next can reduce the idle time caused by frequent switching. Therefore, different preset numbers of hardware frames can make the scheduling of multiple receiver access more flexible and improve the adaptability of free-space quantum key distribution devices to the needs of different receivers.

[0087] In some embodiments of this application, the processor is further configured to generate a phase compensation signal based on the combined distribution of atmospheric wavefront distortion and optical phased array hardware errors, so that the optical phased array performs wavefront distortion compensation on multiple array elements of the optical phased array under the control of the phase compensation signal.

[0088] In embodiments of this application, atmospheric wavefront distortion is used to represent the phase change on the optical wavefront caused by atmospheric disturbances during free-space transmission. Atmospheric wavefront distortion can be wavefront distortion caused by refractive index fluctuations, airflow disturbances, or changes in the propagation path when an optical signal passes through a free-space channel. Exemplarily, atmospheric wavefront distortion can manifest as wavefront tilt, local phase fluctuations, or beam spread trends.

[0089] In embodiments of this application, optical phased array hardware error is used to represent phase deviation caused by differences in the components of the optical phased array itself. Optical phased array hardware error can be a phase shift caused by inconsistencies in array unit response, differences in output path length, phase shifter control errors, or manufacturing errors. For example, hardware error can include phase response deviations between array units, output port position errors, or phase shifter phase loading errors.

[0090] In embodiments of this application, the integrated distribution is used to represent the phase deviation distribution jointly formed by atmospheric wavefront distortion and optical phased array hardware errors. The integrated distribution can be a compensation basis obtained by comprehensively considering the effects of free-space channel and device errors. Exemplarily, the integrated distribution can be obtained from wavefront sensor measurement results, system calibration results, feedback signals, or processor calculation results.

[0091] In embodiments of this application, a phase compensation signal is used to compensate and control the array elements of an optical phased array. The phase compensation signal can be a control signal used to cancel or reduce phase deviations corresponding to the overall distribution. Exemplarily, the phase compensation signal may include the compensated phase value of each array element, or it may include a compensation control amount superimposed on the beam pointing phase control signal.

[0092] In embodiments of this application, the array unit is used to output a phase-modulated optical signal. The array unit can be a basic transmitting unit in an optical phased array used to form an output wavefront. Exemplarily, the array unit may include an output port and a phase shifter, and may also include a waveguide, a coupling structure, and a phase modulation structure.

[0093] Figure 3 A schematic diagram of the structure of an optical phased array according to an embodiment of this application is shown.

[0094] like Figure 3 As shown, the optical phased array 13 may include a beam splitter 131, a controller 132, and an output component 133. The beam splitter 131 can distribute the input optical signal to multiple output paths. The controller 132 can control the phase state of the output paths according to the phase control signal or phase compensation signal generated by the processor. The output component 133 can output phase-modulated pilot light and quantum signal light.

[0095] Figure 4 A schematic diagram of the structure of an optical phased array according to an embodiment of this application is shown.

[0096] like Figure 4 As shown, the output component 133 may include multiple array units 1331. Each array unit 1331 may include an output port D and a phase shifter PS. The phase shifter PS may be located behind the output port D, or positioned to perform phase modulation on the optical signal output from the corresponding output port D. The output port D can be used to directly output an optical signal. By controlling the phase states of the multiple phase shifters PS, the optical signals output from the multiple output ports D can be made to form a predetermined wavefront.

[0097] In the embodiments of this application, when the processor generates a phase compensation signal based on the combined distribution of atmospheric wavefront distortion and optical phased array hardware errors, the controller 132 can load the phase compensation signal to the phase shifter PS of the corresponding array unit 1331. The phase shifter PS compensates and adjusts the phase of the optical signal in the corresponding output path, so that the optical signals output from the output port D are spatially superimposed to form a compensated transmission wavefront.

[0098] By generating a phase compensation signal based on the combined distribution of atmospheric wavefront distortion and optical phased array hardware errors, the processor can simultaneously consider wavefront variations caused by the free-space channel and phase deviations caused by the optical phased array's own hardware. By loading the phase compensation signal onto multiple array elements, the optical phased array can compensate for the phase of the output optical signal of each array element. Since the output optical fields of multiple array elements collectively form the transmitted wavefront, compensating for the phase of the array elements can alter the spatial distribution of the overall transmitted wavefront. Therefore, wavefront distortion compensation can reduce the impact of free-space propagation disturbances and hardware errors on the receiving state of pilot light and quantum signal light, facilitating phase reference recovery and coherent detection at the receiver.

[0099] The embodiments of this application also provide a receiving end.

[0100] Figure 5 A schematic diagram of a receiving end according to an embodiment of this application is shown.

[0101] like Figure 5 As shown, receiver 2 includes signal receiver 21, local laser 22, detector 23 and processing unit 24.

[0102] A signal receiver is configured to receive pilot light and quantum signal light transmitted by a quantum key distribution device. The pilot light and quantum signal light originate from the same source, and the quantum signal light is modulated. A local laser is configured to generate local oscillator light. A detector is configured to coherently probe the pilot light, quantum signal light, and local oscillator light, outputting a probe electrical signal. A processing unit is configured to obtain the quantum key based on the probe electrical signal. The quantum key is obtained through coherent probe between the quantum signal light and the local oscillator light at the receiver, which is phase-compensated based on the pilot light.

[0103] In embodiments of this application, a signal receiver is used to receive pilot light and quantum signal light transmitted from free space. The signal receiver can be a receiving component capable of collecting, coupling, or guiding free-space light signals into the optical path of the receiving end. Exemplarily, the signal receiver may include at least one of a receiving telescope, a space optical coupler, a filter assembly, and an optical fiber coupling assembly.

[0104] In embodiments of this application, a local laser is used to generate local oscillator light. The local laser can be a laser located locally at the receiving end and used to generate coherent detection reference light. Exemplarily, the local laser can be a narrow-linewidth laser, a continuous-wave laser, or a reference light source capable of coherently detecting quantum signal light.

[0105] In embodiments of this application, the local oscillator light is used for coherent detection with the quantum signal light. The local oscillator light can be a reference light in the detector used to interfere with the quantum signal light. Exemplarily, the local oscillator light can be input into the detector after frequency offset correction or phase compensation based on pilot light related information.

[0106] In embodiments of this application, a detector is used to convert the coherent detection results of quantum signal light and local oscillator light into a detection electrical signal. The detector can be a device or module capable of achieving optical coherent detection and outputting an electrical signal. Exemplarily, the detector can be a heterodyne detector, a balanced detector, or a detection structure including an optical mixing component and an electrical signal acquisition component.

[0107] In embodiments of this application, a probe electrical signal is used by the processing unit to generate a quantum key. The probe electrical signal can be an electrical signal output by a detector after coherently probing the quantum signal light and the local oscillator light. Exemplarily, the probe electrical signal may include orthogonal component measurement information, pilot-related information, or a data sequence for subsequent key generation.

[0108] Combination Figure 2 The receiver Bobi represents any one of Bob1 to Bob8. The receiver Bobi can receive pilot light and quantum signal light from the Alice end via a receiving telescope. Laser 2 in the receiver Bobi can generate local oscillator light. The heterodyne detection structure can coherently detect the quantum signal light and the local oscillator light, and output a detection electrical signal. The receiver processing unit can obtain the quantum key based on the detection electrical signal.

[0109] In the embodiments of this application, the pilot light and the quantum signal light are from the same source, enabling the receiver to obtain phase reference information related to the quantum signal light through the pilot light. The receiver can perform phase compensation on the local oscillator light or detection data based on the pilot light, and then use the compensated local oscillator light to perform coherent detection on the quantum signal light.

[0110] In embodiments of this application, a quantum key distribution device may include a light source, a modulator, a processor, and an optical phased array. The light source generates laser light and splits it into pilot light and signal light. The modulator modulates the signal light to generate quantum signal light. The processor generates a phase control signal. Under the control of the phase control signal, the optical phased array transmits the pilot light and quantum signal light to a receiver located at a spatial orientation corresponding to the phase control signal. The receiver obtains the quantum key based on the pilot light and quantum signal light.

[0111] Therefore, the receiver structure can work in conjunction with the pilot light and quantum signal light sent by the quantum key distribution device to achieve coherent reception and quantum key generation after free space transmission.

[0112] In some embodiments of this application, the processing unit is further configured to obtain a quantum key according to the following operations: performing frequency offset estimation and phase compensation based on information about the pilot light in the probe electrical signal; obtaining an initial quantum key based on interference information about the quantum signal light and the local oscillator light in the probe electrical signal; and obtaining the quantum key through classical channel authentication.

[0113] In embodiments of this application, the information about the pilot light in the probe electrical signal can be used to carry information for frequency offset estimation and phase compensation at the receiver. For example, the information about the pilot light in the probe electrical signal may include frequency offset information, phase drift information, or reference sequence information required for phase reference recovery.

[0114] In embodiments of this application, frequency offset estimation is used to determine the frequency offset between the local reference light at the receiver and the received optical signal. Frequency offset estimation can be a process by which the receiver estimates the frequency difference based on information from the auxiliary pilot signal light. Exemplarily, frequency offset estimation can be obtained by performing frequency domain analysis, phase change analysis, or digital signal processing on the pilot-related electrical signal.

[0115] In the embodiments of this application, phase compensation is used to reduce the impact of phase drift on coherent detection results. Phase compensation can be a process of correcting the phase of the local oscillator light or the phase of the detection electrical signal based on information from the auxiliary pilot signal light. Exemplarily, phase compensation can be achieved by adjusting the phase of the local oscillator light, or by performing digital phase correction on the acquired detection electrical signal.

[0116] In embodiments of this application, the initial quantum key is used for subsequent authentication and processing. The initial quantum key can be a preliminary data sequence obtained based on the interference information between the quantum signal light and the local oscillator light. Exemplarily, the initial quantum key can be continuous variable data formed after data processing of the orthogonal component measurement sequence, or it can be key candidate data after quantization processing.

[0117] In embodiments of this application, classical channel authentication is used to authenticate subsequent information exchanges between the communicating parties. Classical channel authentication can be an identity authentication, data comparison, or post-processing authentication process performed through a classical communication link during quantum key distribution. Exemplarily, classical channel authentication can be used in conjunction with parameter estimation, information negotiation, error correction, or security enhancement processes.

[0118] like Figure 2 As shown, after the heterodyne detector structure of the receiver Bobi outputs a probe electrical signal, the processor can first extract the information of the auxiliary pilot signal light from the probe electrical signal and complete frequency offset estimation and phase compensation. After compensation, the processor can obtain the initial quantum key based on the interference information of the quantum signal light and the local oscillator light. Subsequently, the receiver Bobi can authenticate with the transmitter Alice through a classical channel and perform subsequent processing to obtain the quantum key.

[0119] In the embodiments of this application, frequency offset estimation and phase compensation can be performed before quantum signal light data processing, or they can be performed alternately with quantum signal light data processing. The processor can establish a phase compensation amount based on the information of the auxiliary pilot signal light and apply the compensation amount to the probe electrical signal corresponding to the quantum signal light. Then, the processor performs data processing on the compensated probe electrical signal to obtain the initial quantum key.

[0120] The above processing sequence connects the phase reference function of the pilot light, the key-carrying function of the quantum signal light, and the classical channel authentication function, thus forming a complete processing path from detecting electrical signals to quantum keys.

[0121] This application also provides a quantum key distribution system. The quantum key distribution system includes the quantum key distribution device and the receiving end as described in any of the above embodiments.

[0122] In embodiments of this application, a quantum key distribution system is used to establish a free-space quantum key distribution link between a quantum key distribution device and a receiver. The quantum key distribution system can be a system formed by the cooperation of a transmitting device, a receiving device, and a communication channel for classical channel authentication. Exemplarily, the quantum key distribution system may include a quantum key distribution device and a receiver, or it may include a quantum key distribution device and multiple distributed receivers.

[0123] In embodiments of this application, a quantum key distribution device is used to generate and transmit pilot light and quantum signal light. A receiving end is used to receive the pilot light and quantum signal light, and perform coherent detection based on the local oscillator light to obtain the quantum key. The quantum key distribution device and the receiving end can transmit the pilot light and quantum signal light through a free-space channel, and perform authentication or subsequent processing through a classical channel.

[0124] like Figure 1 As shown, a quantum key distribution system may include a quantum key distribution device 1 and a receiver 2. The quantum key distribution device 1 can transmit a transmission beam to the receiver 2 at a corresponding spatial location via an optical phased array 13. Figure 2 The central node Alice can act as a quantum key distribution device, and Bobi can act as a receiver. The central node Alice sends pilot light and quantum signal light to Bobi through an optical phased array, and Bobi completes the reception and detection through a receiving telescope, a local laser 2, and a heterodyne detection structure.

[0125] In some embodiments of this application, the quantum key distribution system may include multiple receivers. A processor can generate phase control signals corresponding to multiple receivers at different spatial orientations at different time periods. An optical phased array can transmit pilot light and quantum signal light to multiple receivers at different time periods. Multiple receivers can receive the pilot light and quantum signal light at their respective corresponding time periods and obtain the quantum key respectively.

[0126] In some embodiments of this application, the quantum key distribution system can be used on fixed ground platforms, mobile platforms, temporary access platforms, or other free-space communication scenarios. The quantum key distribution device can act as a central node, and multiple receivers can be distributed in different spatial locations. The processor adjusts the emission direction of the optical phased array through phase control signals, enabling the system to switch access between different receivers.

[0127] In some embodiments of this application, the quantum key distribution system may perform the following process:

[0128] In step S10, the light source of the quantum key distribution device generates laser light and splits the laser light into pilot light and signal light.

[0129] In step S20, the modulator modulates the signal light to generate quantum signal light.

[0130] In step S30, the processor generates a phase control signal based on the spatial orientation of the target receiver.

[0131] In step S40, the optical phased array transmits pilot light and quantum signal light to the target receiver under the control of the phase control signal.

[0132] In step S50, the signal receiver at the target receiver receives the pilot light and the quantum signal light.

[0133] In step S60, the local laser at the target receiver generates local oscillator light, and the detector uses the local oscillator light, which is phase-compensated based on pilot light, to coherently detect the quantum signal light and output a detection electrical signal.

[0134] In step S70, the processor at the target receiver obtains the quantum key based on the probe electrical signal.

[0135] In some embodiments of this application, when multiple receivers are present, the quantum key distribution system can also perform the following process: The processor generates a phase control signal corresponding to the current target receiver in the current time period and controls the optical phased array to send pilot light and quantum signal light to the current target receiver; after the current target receiver completes reception, the processor generates a phase control signal corresponding to the next target receiver in the next time period and controls the optical phased array to send pilot light and quantum signal light to the next target receiver. Through this method, multiple receivers can sequentially access the quantum key distribution system.

[0136] In some embodiments of this application, the quantum key distribution system can also perform a wavefront distortion compensation process. The processor generates a phase compensation signal based on the combined distribution of atmospheric wavefront distortion and optical phased array hardware errors, and the optical phased array performs wavefront distortion compensation on multiple array elements based on the phase compensation signal. The wavefront distortion compensation process can be performed concurrently with the beam pointing control process, or it can be performed before transmitting the pilot light and quantum signal light.

[0137] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application.

[0138] The embodiments of this application have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Although each embodiment has been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Without departing from the scope of this application, those skilled in the art can make various substitutions and modifications, all of which should fall within the scope of this application.

Claims

1. A quantum key distribution device, characterized in that, The quantum key distribution device includes: A light source is configured to generate laser light and split the laser light into pilot light and signal light; A modulator is configured to modulate the signal light to generate quantum signal light; The processor is configured to generate phase control signals; and An optical phased array is configured to transmit the pilot light and the quantum signal light to a receiver located at a spatial orientation corresponding to the phase control signal under the control of the phase control signal, so that the receiver obtains a quantum key based on the pilot light and the quantum signal light; wherein the quantum key is obtained by coherent detection between the quantum signal light and the local oscillator light in the receiver that is phase-compensated based on the pilot light.

2. The quantum key distribution device according to claim 1, characterized in that, The light source includes: A laser is configured to generate the laser. A beam splitter is configured to split the laser beam into pilot light and signal light, wherein the energy of the pilot light is greater than the energy of the signal light.

3. The quantum key distribution device according to claim 1, characterized in that, The modulator includes a quadrature modulator; The quantum key distribution device also includes: A quantum random number generator is configured to generate quantum random numbers, wherein the orthogonal modulator is configured to modulate the signal light according to the quantum random numbers; An attenuator is configured to attenuate the modulated signal light to obtain the quantum signal light.

4. The quantum key distribution device according to claim 1, characterized in that, The optical phased array is configured to: transmit the pilot light in a first time period and transmit the quantum signal light in a second time period different from the first time period, or transmit the pilot light in a first polarization state and simultaneously transmit the quantum signal light in a second polarization state different from the first polarization state.

5. The quantum key distribution device according to claim 1, characterized in that, The processor is also configured to generate phase control signals corresponding to multiple different spatial orientations at different time periods, so as to transmit the pilot light and the quantum signal light to the receiving end located at the multiple different spatial orientations at the different time periods.

6. The quantum key distribution device according to claim 1, characterized in that, The processor is also configured to transmit different preset numbers of quantum frames to receivers in multiple different spatial orientations.

7. The quantum key distribution device according to claim 1, characterized in that, The processor is also configured to generate a phase compensation signal based on the combined distribution of atmospheric wavefront distortion and optical phased array hardware errors, so that the optical phased array, under the control of the phase compensation signal, performs wavefront distortion compensation on multiple array elements of the optical phased array.

8. A receiving end, characterized in that, The receiving end includes: A signal receiver is configured to receive pilot light and quantum signal light transmitted by a quantum key distribution device, wherein the pilot light and the quantum signal light are emitted from the same source, and the quantum signal light is modulated. The local laser is configured to generate a native oscillator. The detector is configured to coherently detect the pilot light, the quantum signal light, and the local oscillator light, and output a detection electrical signal; The processing unit is configured to obtain a quantum key based on the probed electrical signal; wherein the quantum key is obtained by coherent detection between the quantum signal light and the local oscillator light in the receiver that is phase-compensated based on the pilot light.

9. The receiving end according to claim 8, characterized in that, The processing unit is also configured to obtain the quantum key according to the following operations: Based on the information about the pilot light in the probe electrical signal, frequency offset estimation and phase compensation are performed; Based on the interference information of the probe electrical signal regarding the quantum signal light and the local oscillator light, the initial quantum key is obtained; The quantum key is obtained through classical channel authentication.

10. A quantum key distribution system, characterized in that, The quantum key distribution system includes a quantum key distribution device as described in any one of claims 1-7 and a receiver as described in any one of claims 8-9.

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