Quantum receiving apparatus and method, and laser terminal

Abstract

The present application relates to the technical field of quantum communications, and in particular, to a quantum receiving apparatus and method, and a laser terminal, which are used for reducing deployment cost of a telescope, and reducing response speed and time jitter of a detection module while improving a code rate of quantum key distribution. The quantum receiving apparatus comprises: a receiving array composed of multiple telescopes, used to receive quantum light emitted by a quantum transmitting apparatus by means of a quantum channel; a detection array composed of multiple detection modules, the multiple detection modules being corresponding one-to-one with the multiple telescopes, each detection module being used to detect a light beam output by a corresponding telescope; and a detection selection module, separately connected to the multiple detection modules, and used to select a target detection module from the multiple detection modules on the basis of a detection result of the multiple detection modules, and determine an output result on the basis of the detection result of the target detection module.

Description

A quantum receiving device, method and laser terminal

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese Patent Application No. 202411519408.X, filed on October 28, 2024, entitled "A Quantum Receiving Device, Method and Laser Terminal", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of quantum communication technology, and in particular to a quantum receiving device, method and laser terminal. Background Technology

[0004] Quantum key distribution (QKD) is a key technology in quantum communication. Based on the physical laws of quantum mechanics, it securely distributes encryption keys between two communicating parties. Discrete quantum key distribution typically uses the quantum states (such as polarization states) of a single photon to modulate bit information (i.e., binary numbers). However, single-photon transmission of bit information faces the problem of low key generation rate (i.e., low key distribution rate), especially for free-space channels. Single-photon transmission is affected by the atmospheric channel environment, resulting in low received power at the receiver, which is even more detrimental to key generation.

[0005] Currently, the code generation rate can be directly improved by increasing the receiver gain and the photon emission repetition frequency of the quantum light source at the transmitter. On the one hand, the receiver gain can be increased by increasing the aperture of the telescope at the receiver. However, increasing the aperture of the telescope increases its size and weight, usually requiring customization, and the installation process and maintenance are more complex, resulting in high deployment costs. On the other hand, increasing the photon emission repetition frequency of the quantum light source will increase the requirements for the response speed and timing jitter of the detector at the receiver, and the detection difficulty will increase accordingly. Generally, as the photon emission repetition frequency increases, detectors with higher response speeds and lower timing jitter are required. Summary of the Invention

[0006] This application provides a quantum receiving device, method, and laser terminal, which can improve the quantum key distribution coding rate while reducing the deployment cost of the telescope and reducing the requirements for the response speed and time jitter of the detection module.

[0007] In a first aspect, embodiments of this application provide a quantum receiving device, comprising:

[0008] A receiving array consisting of multiple telescopes is used to receive quantum light;

[0009] A detection array consisting of multiple detection modules, each of which corresponds one-to-one with a multiple telescope, with each detection module used to detect the beam output by the corresponding telescope;

[0010] The detection selection module is connected to the plurality of detection modules respectively, and is used to select a target detection module from the plurality of detection modules according to the detection results of the plurality of detection modules, and determine the output result according to the detection results of the target detection module.

[0011] In this embodiment, receiving quantum light from different angles or paths using a receiving array composed of multiple telescopes increases the receiving gain, thereby improving the quantum key generation rate without increasing the aperture of a single telescope. This reduces the deployment cost of a single telescope, increases deployment flexibility, and facilitates large-scale production. Simultaneously, using multiple detection modules to detect quantum light and selecting the detection result of a target detection module from the results of multiple modules enables time-division detection of quantum light. This allows the high-repetition-frequency quantum light to be evenly distributed across each of the multiple detection modules, reducing the time jitter requirement for each module and lowering the detection difficulty. This facilitates increasing the photon emission repetition frequency of the quantum light source, thereby improving the quantum key generation rate.

[0012] In one optional implementation, it further includes a plurality of polarization-maintaining elements located between the plurality of telescopes and the plurality of detection modules, wherein the plurality of polarization-maintaining elements correspond one-to-one with the plurality of telescopes;

[0013] Each polarization-maintaining element is used to couple the beam output from the corresponding telescope to the corresponding detection module.

[0014] In one alternative implementation, the polarization-maintaining element includes a free-space polarization-maintaining mirror assembly or a polarization-maintaining fiber optic link.

[0015] In one alternative implementation, each detection module includes a polarization-maintaining beam splitter and multiple single-photon detectors;

[0016] The polarization-maintaining beam splitter is used to split the received beam into multiple beams with different polarization states.

[0017] Each single-photon detector is used to detect the power of one beam of light.

[0018] In one optional implementation, the detection selection module is specifically used for:

[0019] Select the target detection module containing the single-photon detector with the highest detection power from among the multiple detection modules;

[0020] Select one beam from the multiple beams detected by the multiple single-photon detectors of the target detection module, and use the polarization state of the selected beam as the output result.

[0021] In one optional implementation, it further includes a control module connected to the detection selection module and a laser communication module connected to the control module;

[0022] The control module is used to acquire the output result of the detection selection module and control the laser communication module to send the output result.

[0023] In one optional implementation, the laser communication module includes an optical communication component, an optical fiber amplifier, and an optical antenna;

[0024] The optical communication component is used to convert the output result into an optical signal;

[0025] The fiber amplifier is used to enhance the optical signal;

[0026] The optical antenna is used to transmit enhanced optical signals.

[0027] In one alternative implementation, each telescope has an aperture on the order of tens or hundreds of millimeters.

[0028] In one alternative implementation, the receiving array composed of the plurality of telescopes includes a one-dimensional linear array, a two-dimensional planar array, or a three-dimensional array.

[0029] Secondly, embodiments of this application provide a quantum receiving method, including:

[0030] The quantum receiving device receives quantum light emitted by the quantum transmitting device through a receiving array composed of multiple telescopes;

[0031] The quantum receiving device uses multiple detection modules to detect the light beams received by the corresponding telescopes; wherein, each of the multiple detection modules corresponds one-to-one with the multiple telescopes.

[0032] The quantum receiving device selects a target detection module from the plurality of detection modules based on the detection results of the target detection module, and determines the output result based on the detection results of the target detection module.

[0033] In one optional implementation, the step of detecting the beams received by the corresponding telescopes through multiple detection modules includes:

[0034] Each detection module splits the beam received by the corresponding telescope into multiple beams with different polarization states, and uses multiple single-photon detectors to detect the power of their respective beams.

[0035] In one optional implementation, the quantum receiving device selects a target detection module from the plurality of detection modules based on the detection results of the target detection module, and determines an output result based on the detection results of the target detection module, including:

[0036] The quantum receiving device selects the target detection module containing the single-photon detector with the highest detection power from the plurality of detection modules;

[0037] Select one beam from the multiple beams detected by the multiple single-photon detectors of the target detection module, and use the polarization state of the selected beam as the output result.

[0038] Thirdly, embodiments of this application provide a laser terminal, including any of the quantum receiving devices described in the first aspect.

[0039] The beneficial effects of the second and third aspects can be referred to the content described in the first aspect above, and will not be repeated here. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0041] Figure 1 is a schematic diagram of the principle of discrete quantum key distribution provided in an embodiment of this application;

[0042] Figure 2 is a schematic diagram of a quantum receiving device provided in an embodiment of this application;

[0043] Figure 3 is a schematic diagram of the arrangement of a telescope array provided in an embodiment of this application;

[0044] Figure 4A is a schematic diagram of the connection between a telescope and a detection module provided in an embodiment of this application;

[0045] Figure 4B is a schematic diagram of another connection between a telescope and a detection module provided in an embodiment of this application;

[0046] Figure 5 is a schematic diagram of a detection module provided in an embodiment of this application;

[0047] Figure 6 is a schematic diagram of another quantum receiving device provided in an embodiment of this application;

[0048] Figure 7 is a flowchart of a quantum receiving method provided in an embodiment of this application;

[0049] Figure 8 is a schematic diagram of a quantum emission device provided in an embodiment of this application;

[0050] Figure 9 is a schematic diagram of a modulation module provided in an embodiment of this application;

[0051] Figure 10 is a schematic diagram of the structure of a laser terminal provided in an embodiment of this application. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this application. Obviously, the described embodiments are only some embodiments of the technical solutions of this application, and not all embodiments. Based on the embodiments recorded in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the technical solutions of this application.

[0053] To facilitate understanding of the technical solutions provided in the embodiments of this application, the background technology related to the embodiments of this application will be introduced first.

[0054] Quantum key distribution (QKD) is a key technology in quantum communication. Based on the physical laws of quantum mechanics, it securely distributes keys between two communicating parties. Discrete quantum key distribution typically uses the quantum states (such as polarization states) of a single photon to modulate bit information (i.e., binary numbers). The following example, based on the BB84 protocol, illustrates the quantum key distribution process with reference to Figure 1.

[0055] During the preparation phase, the sender (usually called Alice) generates a random bit sequence called the raw key. For each random bit, Alice randomly chooses to encode it using either the Z-basis (standard basis) or the X-basis (Hadamard basis). The Z-basis consists of two quantum states: |0> and |1>. When the bit information is modulated based on polarization state, |0> is usually represented by the horizontal polarization state (H) and |1> by the vertical polarization state (V). The X-basis also consists of two quantum states: |+> or |->. |+> is usually represented by the +45 degree polarization state and |-> by the -45 degree polarization state.

[0056] As shown in Figure 1, during the transmission phase, Alice encodes each random bit into a corresponding quantum state according to the selected basis (Z basis or X basis) and sends it to the receiver (usually called Bob) through a quantum channel (such as optical fiber or free space). For example, if the random bit is 0 and the basis is Z, then |0> (i.e., a single photon in a horizontally polarized state) is sent; if the bit is 1 and the basis is Z, then |1> (i.e., a single photon in a vertically polarized state) is sent; if the bit is 0 and the basis is X, then |+> (i.e., a single photon in a +45 degree polarized state) is sent; and if the bit is 1 and the basis is X, then |-> (i.e., a single photon in a -45 degree polarized state) is sent.

[0057] During the receiving phase, Bob doesn't know the basis Alice is using, so he randomly chooses either the Z basis or the X basis to measure the received single photon. If Bob chooses the correct basis (the same basis as Alice), he will measure the correct random bits; if Bob chooses the wrong basis, he will get a random result.

[0058] During the public comparison phase, Alice and Bob publicly compare their chosen bases via classic channels (such as telephone, internet, broadcast, etc.), but do not disclose the specific measurement results. Only when Alice and Bob choose the same base are the corresponding random bits valid, and these random bits are retained to form part of the shared key. Other random bits are discarded.

[0059] However, single-photon transmission of bit information faces the problem of low key generation rate (i.e., low key distribution rate), especially for free-space channels. Single-photon transmission is affected by the atmospheric channel environment, resulting in low received power at the receiver, which is even more unfavorable for key generation. By increasing the total number of photons received at the receiver, the key generation rate of single-photon transmission of bit information can be improved; specifically, the total number of photons received at the receiver can be calculated by the following formula (1):

[0060] in, The total number of photons received is given, and the received optical power is proportional to the total number of photons received. R is the signal state scaling factor, and N is the signal state scaling factor. pulse Let f be the average number of photons per pulse, f be the photon repetition frequency of the light source, and L be the total link loss (dB value). Equation (1) shows that increasing the photon repetition frequency f or decreasing the total link loss L can increase the number of photons received at the receiver. The total link loss is related to factors such as transmit gain, receive gain, and channel attenuation. Increasing the transmit gain or receive gain can significantly reduce the total link attenuation. The transmit gain or receive gain is directly proportional to the telescope aperture. Taking the receive gain as an example, the receive gain G can be calculated using the following equation (2). r D is the aperture of the receiving telescope, and λ is the wavelength.

[0061] It is evident that the code generation rate can be directly improved by increasing the receiving gain at the receiver and the photon emission repetition frequency of the quantum light source at the transmitter. On the one hand, the receiving gain can be increased by increasing the aperture of the telescope at the receiver. However, increasing the aperture of a single telescope (e.g., 1m) will increase the size and weight of the telescope, usually requiring customization. As is well known in the art, custom-made telescopes with apertures of 1m and above have huge raw material costs, long production cycles, and complex processes, installations, and maintenance, resulting in high deployment costs. On the other hand, increasing the photon emission repetition frequency of the quantum light source will increase the requirements for the response speed and timing jitter of the detector at the receiver, correspondingly increasing the detection difficulty. Generally, as the photon emission repetition frequency increases, detectors with higher response speeds and lower timing jitter are required.

[0062] In view of this, embodiments of this application provide a quantum receiving device, including a receiving array composed of multiple telescopes and a detection array composed of multiple detection modules, with each telescope and detection module corresponding one-to-one. By receiving quantum light from different angles or paths through the receiving array composed of multiple telescopes, the receiving capability of a single large-aperture telescope can be achieved, thereby increasing the receiving gain and improving the quantum key generation rate, without increasing the aperture of a single telescope. This reduces the deployment cost of a single telescope, improves deployment flexibility, and facilitates large-scale production. Simultaneously, multiple detection modules are used to detect quantum light, and the detection result of a target detection module is selected from the detection results of multiple detection modules, thereby achieving time-division detection of quantum light. This allows the high-repetition-frequency quantum light to be evenly distributed across each of the multiple detection modules, reducing the time jitter requirement for each detection module and lowering the detection difficulty for each module. This facilitates increasing the photon emission repetition frequency of the quantum light source to improve the quantum key generation rate.

[0063] The structure of the quantum receiving device provided in the embodiments of this application will be described in detail below.

[0064] As shown in Figure 2, a quantum receiving device 10 provided in this application embodiment includes: a receiving array 11 composed of multiple telescopes, a detection array 12 composed of multiple detection modules, and a detection selection module 13; wherein, the multiple detection modules correspond one-to-one with the multiple telescopes, and the detection selection module 13 is connected to the multiple detection modules respectively.

[0065] The receiving array 11 is used to receive quantum light; each detection module in the detection array 12 is used to detect the beam output by the corresponding telescope; the detection selection module 13 is used to select a target detection module from multiple detection modules based on the detection results of multiple detection modules, and determine the output result based on the detection results of the target detection module.

[0066] In this system, the quantum light received by the receiving array 11 can be a single photon. At any given moment, one of the multiple telescopes may receive the single photon. To determine which telescope received the single photon, a target detection module can be selected from the multiple detection modules based on their detection results. Specifically, each detection module may include at least a single-photon detector, which can detect the power of the received beam. The detection selection module 13 can select the target detection module with the highest detection power (i.e., the highest output current) from the multiple detection modules. Furthermore, when the quantum light emitted by the quantum emission device is not a single photon, some of the multiple telescopes may receive the single photon. In this case, the target detection module with the highest detection power can also be selected from the multiple detection modules.

[0067] Optionally, the aperture of each telescope can be in the range of tens of millimeters or hundreds of millimeters. Specifically, existing small-aperture commercial telescopes can be used, which are small in size and weight, flexible and portable, easy to deploy, low in cost, and can be mass-produced.

[0068] In some possible implementations, the receiving array 11 composed of multiple telescopes can be a one-dimensional linear array, a two-dimensional planar array, or a three-dimensional array. A one-dimensional linear array refers to multiple telescopes arranged in a straight line, a two-dimensional planar array refers to multiple telescopes arranged in a plane, and a three-dimensional array refers to multiple telescopes arranged in three-dimensional space. For example, Figure 3 shows possible arrangements of a one-dimensional linear array and a two-dimensional planar array. Besides the grid shape shown in Figure 3, the two-dimensional planar array can also be other shapes, such as a ring array or a Y-shaped array. Furthermore, the array composed of multiple telescopes can also be a randomly distributed array; this is not limited.

[0069] Compared to a single small-aperture telescope, the embodiments of this application utilize a receiver array composed of multiple small-aperture telescopes to receive quantum light diversityably, which significantly increases the receiving gain and is beneficial for improving the quantum key generation rate. Compared to a single large-aperture telescope, receiving quantum light diversity through an array of multiple small-aperture telescopes can achieve the same receiving gain as a single large-aperture telescope, while reducing deployment costs, increasing deployment flexibility, and facilitating large-scale production.

[0070] In one optional embodiment, the quantum receiving device further includes a plurality of polarization-maintaining elements located between a plurality of telescopes and a plurality of detection modules, wherein each polarization-maintaining element corresponds one-to-one with a plurality of telescopes, and each polarization-maintaining element is used to couple the beam output by the corresponding telescope to the corresponding detection module.

[0071] Optionally, each polarization-maintaining element includes a free-space optical polarization-maintaining mirror group or a polarization-maintaining fiber link, which can keep the polarization state of the beam output by the telescope unchanged. The free-space optical polarization-maintaining mirror group can specifically be a lens group. As shown in Figure 4A, each telescope and its corresponding detection module can transmit the beam through the free-space optical lens group. As shown in Figure 4B, each telescope and its corresponding detection module can also transmit the beam through the polarization-maintaining fiber link, thereby ensuring that the polarization direction of the beam output by the telescope remains unchanged, so as to facilitate the subsequent detection of the beam's polarization state.

[0072] In one alternative implementation, each detection module may include a polarization-maintaining beam splitter and multiple single-photon detectors; the polarization-maintaining beam splitter is used to split the received beam into multiple beams with different polarization states; each single-photon detector is used to detect the power of one beam.

[0073] Different polarization states can be selected as needed, such as horizontal polarization, vertical polarization, +45-degree polarization, and -45-degree polarization. Besides these linear polarization states, circular polarization can also be included; there is no limitation on this. The number of single-photon detectors is the same as the number of beams with different polarization states; that is, each single-photon detector is used to detect the power of a beam with one polarization state. Specifically, the single-photon detector includes a photodiode and circuitry.

[0074] For example, as shown in Figure 5, each detection module includes a polarization-maintaining beam splitter and four single-photon detectors. The polarization-maintaining beam splitter can split the received light beam into four beams: a beam with a horizontal polarization state, a beam with a vertical polarization state, a beam with a +45-degree polarization state, and a beam with a -45-degree polarization state. In this case, the polarization-maintaining beam splitter can include a beam splitter, a first polarization-maintaining beam splitter, and a second polarization-maintaining beam splitter. The first and second polarization-maintaining beam splitters can utilize the polarization characteristics of light to separate light with different polarization directions, splitting it into different paths according to the polarization state. Specifically, the beam splitter splits the received light beam into two beams: one beam is split into a horizontally polarized beam and a vertically polarized beam by the first polarization-maintaining beam splitter, and the other beam is split into a +45-degree polarized beam and a -45-degree polarized beam by the second polarization-maintaining beam splitter.

[0075] In this embodiment, each detection module can split the received beam into multiple beams with different polarization states through a polarization-maintaining beam splitter. Then, multiple single-photon detectors detect the power of their respective beams, thereby facilitating the detection of the power of the received beams in different polarization states and obtaining the detection results.

[0076] In one optional implementation, the detection selection module 13 is specifically used to select the target detection module containing the single-photon detector with the highest detection power from among multiple detection modules; then, it selects one beam from the multiple beams detected by the multiple single-photon detectors of the target detection module, and takes the polarization state of the selected beam as the output result.

[0077] Specifically, the detection selection module 13 can employ processing circuitry, such as a Field-Programmable Gate Array (FPGA) circuit, etc., without limitation. After selecting the target detection module from multiple detection modules, a beam can be randomly selected from the multiple beams detected by the multiple single-photon detectors of the target detection module to output the polarization state of that beam. Specifically, during quantum key distribution, the receiver can send the polarization state output by the quantum receiver to the transmitter, so that the transmitter can compare the polarization state of the quantum light emitted by the quantum transmitter with the polarization state output by the quantum receiver. If they match, the random bit corresponding to that polarization state is retained for subsequent quantum key generation.

[0078] In this embodiment, the quantum receiving device receives quantum light through a receiving array composed of multiple telescopes, which significantly increases the receiving gain and is beneficial for improving the quantum key generation rate, without increasing the aperture of a single telescope. This reduces the deployment cost of a single telescope, improves deployment flexibility, and facilitates large-scale production. Simultaneously, using a detection array composed of multiple detection modules to detect quantum light reduces the requirements for the response speed and timing jitter of a single detection module, meeting the receiving conditions for increasing the photon repetition frequency at the transmitting end and improving the quantum key distribution rate.

[0079] In some embodiments, as shown in FIG6, the quantum receiving device further includes a control module 14 connected to the detector selection module 13 and a laser communication module 15 connected to the control module 14; the control module 14 is used to acquire the output result of the detector selection module 13 and control the laser communication module 15 to send the output result.

[0080] Optionally, the laser communication module 15 includes an optical communication component 151, an optical fiber amplifier 152, and an optical antenna 153 connected in sequence; the optical communication component 151 is used to convert the output result into an optical signal; the optical fiber amplifier 152 is used to enhance the optical signal; and the optical antenna 153 is used to transmit the enhanced optical signal.

[0081] The optical communication component 151 specifically includes a light source, a modulator, etc., used for transmitting and receiving optical signals in the optical fiber. The control module 14 can use existing controllers, such as programmable logic controllers, microcontrollers, etc., and there is no limitation on this.

[0082] During quantum key distribution, each time the quantum receiver 10 receives quantum light, it obtains a corresponding output result (such as the selected polarization state) by detecting the quantum light. The control module 14 is used to send each obtained output result to the transmitting end (such as another laser terminal) where the quantum transmitter is located via the laser communication module 15. Specifically, the control module 14 can send the output result to the transmitting end after obtaining each output result, or it can send multiple output results to the transmitting end together. In addition, in order to enable the transmitting end to distinguish the quantum light corresponding to multiple output results, each output result can be packaged with the detection time of the corresponding quantum light, and each data packet can be sent to the transmitting end.

[0083] The transmitting end can compare the polarization state of the quantum light transmitted multiple times with the above multiple output results one by one, and send the comparison results to the laser terminal (i.e., the receiving end). The laser communication module 15 of the laser terminal can receive the comparison results and send the comparison results to the control module 14. The control module 14 can determine the quantum key based on the comparison results.

[0084] Based on the same inventive concept, this application also provides a quantum receiving method. The principle of this method in solving the problem is similar to that of the quantum receiving device in the above embodiments. Therefore, the implementation of this method can refer to the implementation of the above device, and the repeated parts will not be described again.

[0085] As shown in Figure 7, an embodiment of this application provides a quantum receiving method, including the following steps S701-S703:

[0086] S701, the quantum receiving device receives quantum light emitted by the quantum transmitting device through a receiving array composed of multiple telescopes.

[0087] S702, the quantum receiving device detects the light beams received by the corresponding telescopes through multiple detection modules; wherein, the multiple detection modules correspond one-to-one with the multiple telescopes;

[0088] In one optional implementation, multiple detection modules are used to detect the beams received by the corresponding telescopes, specifically including:

[0089] Each detection module splits the beam received by the corresponding telescope into multiple beams with different polarization states, and uses multiple single-photon detectors to detect the power of their respective beams.

[0090] S703, The quantum receiving device selects a target detection module from the multiple detection modules based on the detection results of the target detection module, and determines the output result based on the detection results of the target detection module;

[0091] In one optional implementation, the quantum receiving device selects the detection result of one detection module from the detection results of multiple detection modules, specifically including:

[0092] The quantum receiving device selects the target detection module containing the single-photon detector with the highest detection power from multiple detection modules, selects one beam from the multiple beams detected by the multiple single-photon detectors of the target detection module, and outputs the polarization state of the selected beam.

[0093] The quantum receiving device in this embodiment can receive quantum light emitted by the quantum transmitting device, as shown in FIG8. The quantum transmitting device 80 includes:

[0094] Quantum Light Source 81, used to generate quantum light;

[0095] Random number generator 82 is used to generate random bits;

[0096] Modulation module 83 is used to modulate quantum light based on random bits;

[0097] Optical antenna 84 is used to emit modulated quantum light.

[0098] The quantum light source can generate quantum light with a photon number that follows a Poisson distribution using a high repetition frequency. By setting the mean of the Poisson distribution, the average photon number is made close to that of a single photon. The modulation module 83 can use different polarization states of the single photon to encode random bits, i.e., binary numbers 0 or 1. That is, according to the value of the random bit, the single photon is modulated into different polarization states. Specifically, existing modulation methods can be used, such as polarization modulation methods. The quantum light can specifically be a single photon, and the single photon is modulated into the corresponding polarization state according to the value of the random bit. For example, when the transmitter selects the Z-based, when the value of the random bit is 0, the single photon is modulated into a horizontal polarization state, and when the value of the random bit is 1, the single photon is modulated into a vertical polarization state; or, when the transmitter selects the X-based, when the value of the random bit is 0, the single photon is modulated into a +45 degree polarization state, and when the value of the random bit is 1, the single photon is modulated into a -45 degree polarization state.

[0099] For example, as shown in Figure 9, the modulation module 83 includes an intensity modulator 831, a polarization control module 832, and a phase modulator 833. The single-photon signal generated by the quantum light source is intensity modulated by the intensity modulator, which achieves intensity modulation by driving signals of different magnitudes of voltage. The modulated single-photon signal output by the intensity modulator is then passed through the polarization control module 832, which includes components such as a polarization beam splitter and a polarization rotator. The polarization control module 832 splits the modulated single-photon signal into two signals. One of the signals is phase modulated by the phase modulator, which achieves phase modulation by driving signals of different magnitudes of voltage. After that, the phase-modulated signal and the other signal have different phase delays. The phase-modulated signal and the other signal are then combined to obtain the polarization-modulated single-photon signal. The polarization state of the modulated signal can be determined based on the phase delay.

[0100] The quantum receiving device in this embodiment of the application receives modulated single photons emitted by a quantum transmitting device through an array of multiple telescopes. Multiple detection modules then detect the beam received by the corresponding telescopes. Finally, the detection result of a target detection module is selected from the detection results of the multiple detection modules to obtain the output result. Specifically, each detection module splits the received beam into multiple beams with different polarization states, and multiple single-photon detectors detect the power of each beam. The target detection module, containing the single-photon detector with the highest detection power, is selected from the multiple beams detected by the single-photon detectors of the target detection module. The polarization state of the selected beam is then used as the output result.

[0101] In a quantum key distribution scenario, the quantum transmitter at the sending end can send modulated single photons multiple times to the quantum receiver at the receiving end. Each time the quantum receiver receives a single photon, it can obtain a corresponding output result, specifically the selected polarization state. The receiver can send the selected polarization states multiple times to the transmitter, so that the transmitter can compare the polarization states of the multiple single photons sent with those selected by the receiver, and send the comparison results back to the receiver. The receiver uses the random bits corresponding to the polarization states that match (i.e., the polarization states sent by the transmitter and the polarization states selected by the receiver match) as part of the key, thereby determining the quantum key for encrypted communication between the transmitter and receiver.

[0102] Based on the same inventive concept, this application also provides a laser terminal, which includes, but is not limited to, a communication terminal, for example, a receiver in a quantum key distribution scenario. As shown in FIG10, the laser terminal includes the quantum receiving device 10 in the above embodiment, and also includes a key storage device 20 connected to the control module 14 of the quantum receiving device 10; after determining the quantum key, the control module 14 can store the quantum key in the key storage device 20 to facilitate subsequent encrypted communication with the sender using the quantum key. Specifically, the key storage device 20 can be an existing memory, and there is no limitation thereto.

[0103] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0104] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

A quantum receiving device, characterized in that, include: A receiving array consisting of multiple telescopes is used to receive quantum light; A detection array consisting of multiple detection modules, each of which corresponds one-to-one with a multiple telescope, with each detection module used to detect the beam output by the corresponding telescope; The detection selection module is connected to the plurality of detection modules respectively, and is used to select a target detection module from the plurality of detection modules according to the detection results of the plurality of detection modules, and determine the output result according to the detection results of the target detection module. The apparatus according to claim 1, characterized in that, It also includes a plurality of polarization-maintaining elements located between the plurality of telescopes and the plurality of detection modules, wherein each of the plurality of polarization-maintaining elements corresponds one-to-one with the plurality of telescopes; Each polarization-maintaining element is used to couple the beam output from the corresponding telescope to the corresponding detection module. The apparatus according to claim 2 is characterized in that, The polarization-maintaining element is a free-space optical polarization-maintaining mirror group or a polarization-maintaining fiber link. The apparatus according to claim 1, characterized in that, Each detection module includes a polarization-maintaining beam splitter and multiple single-photon detectors; The polarization-maintaining beam splitter is used to split the received beam into multiple beams with different polarization states. Each single-photon detector is used to detect the power of its corresponding beam. The apparatus according to claim 4, characterized in that, The detection selection module is specifically used for: Select the target detection module containing the single-photon detector with the highest detection power from among the multiple detection modules; Select one beam from the multiple beams detected by the multiple single-photon detectors of the target detection module, and use the polarization state of the selected beam as the output result. The apparatus according to any one of claims 1 to 5 is characterized in that, It also includes a control module connected to the detection selection module and a laser communication module connected to the control module; The control module is used to acquire the output result of the detection selection module and control the laser communication module to send the output result. The apparatus according to claim 6, characterized in that, The laser communication module includes an optical communication component, an optical fiber amplifier, and an optical antenna; The optical communication component is used to convert the output result into an optical signal; The fiber amplifier is used to enhance the optical signal; The optical antenna is used to transmit enhanced optical signals. The apparatus according to any one of claims 1 to 5 is characterized in that, Each telescope has an aperture on the order of tens or hundreds of millimeters. The apparatus according to any one of claims 1 to 5 is characterized in that, The receiving array composed of multiple telescopes includes a one-dimensional linear array, a two-dimensional planar array, or a three-dimensional array. A quantum receiving method, characterized in that, include: The quantum receiving device receives quantum light emitted by the quantum transmitting device through a receiving array composed of multiple telescopes; The quantum receiving device uses multiple detection modules to detect the light beams received by the corresponding telescopes; wherein, each of the multiple detection modules corresponds one-to-one with the multiple telescopes. The quantum receiving device selects a target detection module from the multiple detection modules based on the detection results of the target detection module, and determines the output result based on the detection results of the target detection module. The method according to claim 10, characterized in that, The step of detecting the beams received by the corresponding telescopes through multiple detection modules includes: Each detection module splits the beam received by the corresponding telescope into multiple beams with different polarization states, and uses multiple single-photon detectors to detect the power of their respective beams. The method according to claim 10, characterized in that, The quantum receiving device selects a target detection module from the multiple detection modules based on their detection results, and determines the output result based on the detection results of the target detection module, including: The quantum receiving device selects the target detection module containing the single-photon detector with the highest detection power from the plurality of detection modules; Select one beam from the multiple beams detected by the multiple single-photon detectors of the target detection module, and use the polarization state of the selected beam as the output result. A laser terminal, characterized in that, Includes the quantum receiving device according to any one of claims 1 to 9.

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