Quantum key distribution method and system under free space channel

Abstract

The invention provides a quantum key distribution method and system under a free space channel. A transmitting device is used for controlling a first quantum state transmitter to transmit quantum light under the free space channel according to a first transmitting side random state base; the receiving equipment is used for controlling the ith quantum state receiver to receive quantum light according to the ith receiving side random state base, and i is larger than or equal to 1 and smaller than or equal to N; the receiving equipment is used for transmitting the ith receiving side random state base to the transmitting equipment through a classical channel; the transmitting equipment is used for feeding back a first transmitting side random state base to the receiving equipment through a classic channel after receiving the ith receiving side random state base; and under the condition that the first transmitting side random state base is the same as the ith receiving side random state base, the transmitting equipment is used for generating a current quantum key according to the quantum light transmitted by the first quantum state transmitter, and the receiving equipment is used for generating the current quantum key according to the quantum light received by the ith quantum state receiver, so that the key generation rate is increased.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication, and in particular to a quantum key distribution method and system in a free space channel. Background Art

[0002] Quantum Key Distribution (QKD) is a confidential communication method that uses quantum systems as information carriers for transmission and then extracts shared security keys. For example, single photons are used as carriers, the sender loads encoded information, and the receiver detects decoded information to extract shared security keys.

[0003] Quantum key distribution is an important branch of quantum information technology. The transmission channels of quantum key distribution equipment mainly include optical fiber channels and free space channels. Quantum key distribution under free space channels can be applied to satellites, drones and other scenarios. The information carrier of free space quantum key distribution is mainly attenuated laser beams.

[0004] Currently, quantum key distribution devices in satellite and drone scenarios all adopt a single-transmit and single-receive method. However, since laser beams in free space inevitably diverge, the photons at the transmitting end cannot be fully received, resulting in a reduced key generation rate. Summary of the invention

[0005] The object of the present invention is to provide a quantum key distribution method and system under a free space channel to at least partially improve the above-mentioned problems.

[0006] In order to achieve the above purpose, the technical solution adopted by the embodiment of the present invention is as follows:

[0007] In a first aspect, an embodiment of the present invention provides a quantum key distribution system in a free space channel, the quantum key distribution system comprising a transmitting device and a receiving device, the transmitting device is provided with a first quantum state transmitter, and the receiving device is provided with N quantum state receivers;

[0008] The transmitting device is used to control the first quantum state transmitter to transmit quantum light in a free space channel according to the first transmitting side random state basis;

[0009] The receiving device is used to control the i-th quantum state receiver to receive quantum light according to the i-th receiving side random state basis, where 1≤i≤N;

[0010] The receiving device is used to transmit the i-th receiving side random state basis to the transmitting device through a classical channel;

[0011] The transmitting device is used for feeding back the first transmitting side random state base to the receiving device through a classical channel after receiving the i-th receiving side random state base;

[0012] When the first transmitting side random state base is the same as the i-th receiving side random state base, the transmitting device is used to generate a current quantum key based on the quantum light emitted by the first quantum state transmitter, and the receiving device is used to generate a current quantum key based on the quantum light received by the i-th quantum state receiver.

[0013] Optionally, when the first transmitting side random state basis is the same as the i-th receiving side random state basis, the transmitting device is used to look up quantum light and key mapping information, and determine a quantum key that matches the quantum light emitted by the first quantum state transmitter as the current quantum key; the receiving device is used to look up quantum light and key mapping information, and determine a quantum key that matches the quantum light received by the i-th quantum state receiver as the current quantum key.

[0014] Optionally, in a case where the first transmitting-side random state base is different from all receiving-side random state bases, the transmitting device and the receiving device are configured to determine that the base matching fails.

[0015] Optionally, the transmitting device is provided with M quantum state transmitters;

[0016] The transmitting device is used to control the j-th quantum state transmitter to transmit quantum light in a free space channel according to the j-th transmitting side random state basis within the j-th interval of the current quantum light emission cycle;

[0017] The receiving device is used to control the i-th quantum state receiver to receive quantum light in the j-th interval according to the i-th receiving side random state basis, where 1≤j≤M;

[0018] The receiving device is used to transmit the i-th receiving side random state basis corresponding to the j-th interval to the transmitting device through a classical channel;

[0019] After receiving the i-th receiving-side random state base corresponding to the j-th interval, the transmitting device feeds back the j-th transmitting-side random state base to the receiving device through a classical channel;

[0020] When the i-th receiving side random state basis corresponding to the j-th interval is the same as the j-th transmitting side random state basis, the transmitting device is used to generate the j-th interval quantum key according to the quantum light transmitted by the j-th quantum state transmitter in the j-th interval; the receiving device is used to generate the j-th interval quantum key according to the quantum light received by the i-th quantum state receiver in the j-th interval.

[0021] Optionally, the transmitting device and the receiving device are used to sort multiple interval quantum keys generated in the current quantum light emission cycle, and call the interval quantum keys generated in the current quantum light emission cycle according to the sorting.

[0022] Optionally, the transmitting device includes a first controller and M quantum state transmitters, the first controller is connected to the M quantum state transmitters respectively, and the first controller is connected to the receiving device through a classical channel communication.

[0023] Optionally, the receiving device includes a second controller and N quantum state receivers, the second controller is connected to the N quantum state receivers respectively, and the second controller is connected to the transmitting device through a classical channel communication.

[0024] Optionally, the M quantum state transmitters and the N quantum state receivers are time synchronized at preset periodic intervals.

[0025] In a second aspect, an embodiment of the present invention provides a quantum key distribution method under a free space channel, which is applied to the above-mentioned quantum key distribution system, and the method includes:

[0026] The transmitting device controls the first quantum state transmitter to transmit quantum light in a free space channel according to the first transmitting side random state basis;

[0027] The receiving device controls the i-th quantum state receiver to receive quantum light according to the i-th receiving side random state basis, where 1≤i≤N;

[0028] The receiving device transmits the i-th receiving-side random state basis to the transmitting device through a classical channel;

[0029] After receiving the i-th receiving-side random state base, the transmitting device feeds back the first transmitting-side random state base to the receiving device through a classical channel;

[0030] When the first transmitting side random state base is the same as the i-th receiving side random state base, the transmitting device generates a current quantum key based on the quantum light emitted by the first quantum state transmitter, and the receiving device generates a current quantum key based on the quantum light received by the i-th quantum state receiver.

[0031] Optionally, the step of the transmitting device generating a current quantum key according to the quantum light emitted by the first quantum state transmitter, and the receiving device generating a current quantum key according to the quantum light received by the i-th quantum state receiver includes:

[0032] The transmitting device searches for quantum light and key mapping information, and determines a quantum key that matches the quantum light emitted by the first quantum state transmitter as the current quantum key;

[0033] The receiving device searches for quantum light and key mapping information, and determines a quantum key that matches the quantum light received by the i-th quantum state receiver as the current quantum key.

[0034] Compared with the prior art, an embodiment of the present invention provides a quantum key distribution method and system under a free space channel, wherein a transmitting device is used to control a first quantum state transmitter to transmit quantum light under a free space channel according to a first transmitting side random state basis; a receiving device is used to control an i-th quantum state receiver to receive quantum light according to an i-th receiving side random state basis, wherein 1≤i≤N; the receiving device is used to transmit the i-th receiving side random state basis to the transmitting device through a classical channel; the transmitting device is used to feed back the first transmitting side random state basis to the receiving device through a classical channel after receiving the i-th receiving side random state basis; when the first transmitting side random state basis is the same as the i-th receiving side random state basis, the transmitting device is used to generate a current quantum key according to the quantum light emitted by the first quantum state transmitter, and the receiving device is used to generate a current quantum key according to the quantum light received by the i-th quantum state receiver, thereby increasing the key generation rate.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 One of the structural schematic diagrams of the quantum key distribution system provided in an embodiment of the present invention.

[0038] Figure 2 The second structural diagram of the quantum key distribution system provided in an embodiment of the present invention.

[0039] Figure 3 The third structural diagram of the quantum key distribution system provided for an embodiment of the present invention.

[0040] Figure 4 A schematic diagram of a flow chart of a quantum key distribution method provided in an embodiment of the present invention.

[0041] In the figure: 10 - transmitting device; 20 - receiving device; 101 - quantum state transmitter; 102 - first controller; 201 - quantum state receiver; 202 - second controller. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0045] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0046] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0047] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0049] In order to improve the key generation rate, the embodiment of the present invention provides a quantum key distribution system under a free space channel, please refer to Figure 1 , Figure 1 This is one of the structural diagrams of the quantum key distribution system provided by the embodiment of the present invention. The quantum key distribution system includes a transmitting device 10 and a receiving device 20, and the transmitting device 10 is provided with one or more quantum state transmitters 101. Figure 1 In the example, the transmitting device 10 is provided with one quantum state transmitter 101, that is, the first quantum state transmitter 101. When the transmitting device 10 is provided with M quantum state transmitters 101, it can be represented as the jth quantum state transmitter 101, 1≤j≤M. The receiving device 20 is provided with N quantum state receivers 201, which can be represented as the i-th quantum state receiver 201, where 1≤i≤N.

[0050] The transmitting device 10 and the receiving device 20 are communicatively connected via a classical channel.

[0051] The transmitting device 10 is used to control the first quantum state transmitter 101 to transmit quantum light in a free space channel according to the first transmitting side random state basis.

[0052] The quantum state transmitter 101 can be, but is not limited to, a telescope system of satellite-to-ground free-space QKD.

[0053] Optionally, the quantum key distribution system can be but is not limited to using the polarization BB84 protocol. The polarization BB84 protocol corresponds to the Z basis {0 degrees, 90 degrees} and the X basis {45 degrees, 135 degrees}, and there are a total of 4 polarization states.

[0054] The first emission side random state basis may be a Z basis or an X basis, and the first emission side random state basis may change at different time points. When the first emission side random state basis is a Z basis, the quantum light emitted by the first quantum state emitter 101 is a quantum light in a 0-degree polarization state or a quantum light in a 90-degree polarization state; when the first emission side random state basis is an X basis, the quantum light emitted by the first quantum state emitter 101 is a quantum light in a 45-degree polarization state or a quantum light in a 135-degree polarization state.

[0055] The receiving device 20 is used to control the i-th quantum state receiver 201 to receive quantum light according to the i-th receiving side random state basis, where 1≤i≤N.

[0056] The random state basis of the i-th receiving side may be a Z basis or an X basis, and the random state basis of the i-th receiving side may change at different time points.

[0057] The receiving device 20 is used to transmit the i-th receiving-side random state basis to the transmitting device 10 through a classical channel.

[0058] Optionally, the receiving device 20 transmits the i-th receiving-side random state basis in the current quantum light emission period to the transmitting device 10 through a classical channel.

[0059] The transmitting device 10 is used to feed back the first transmitting side random state base to the receiving device 20 through the classical channel after receiving the i-th receiving side random state base.

[0060] Optionally, the transmitting device 10 feeds back the first transmitting-side random state basis in the current quantum light emission cycle to the receiving device 20 via a classical channel.

[0061] The transmitting device 10 and the receiving device 20 can determine whether the first transmitting side random state basis and the i-th receiving side random state basis in the current quantum light emission cycle are the same. If they are the same, it means that the i-th quantum state receiver 201 can successfully and accurately obtain the quantum light emitted by the first quantum state transmitter 101 in the current quantum light emission cycle, and can generate a quantum key based on it. The specific process is as follows.

[0062] When the first transmitting side random state base is the same as the i-th receiving side random state base, the transmitting device 10 is used to generate the current quantum key based on the quantum light emitted by the first quantum state transmitter 101, and the receiving device 20 is used to generate the current quantum key based on the quantum light received by the i-th quantum state receiver 201.

[0063] Among them, the current quantum key is the quantum key corresponding to the quantum light in the current quantum light emission period.

[0064] Taking the polarization BB84 protocol as an example, it is assumed that the receiving device 20 is provided with two quantum state receivers 201, namely the first quantum state receiver 201 and the second quantum state receiver 201. The first quantum state transmitter 101 is named Alice, the first quantum state receiver 201 is named Bob, and the second quantum state receiver 201 is named Charlie. In the current quantum light emission cycle, Alice, Bob, and Charlie independently and randomly select one of the X basis or the Z basis, and the selection probability is 50%.

[0065] According to the protocol rules, when the basis vector of the photon sent by Alice is the same as the measurement basis vector selected by Bob / Charlie, the basis matching is successful, and the key can be successfully generated in this case. When the basis vector sent by Alice is different from that of Bob and Charlie, the basis matching fails, and the key cannot be generated in this case. The specific basis selection is as follows in Table 1:

[0066] Table 1

[0067] Alice Bob Charlie Can a key be generated? X X X Can X X Z Can X Z X Can X Z Z no Z X X no Z X Z Can Z Z X Can Z Z Z Can

[0068] As can be seen from Table 1, there are 8 base selection situations for Alice, Bob, and Charlie, and the probability of these 8 situations occurring is the same. There are 6 situations in total that can successfully generate keys, so the probability of successfully generating keys is 75%.

[0069] For a single receiving end mechanism, the basis is as follows in Table 2:

[0070] Table 2

[0071] Alice Bob Can a key be generated? X X Can X Z no Z X no Z Z Can

[0072] As can be seen from Table 2, there are 4 base selection situations for Alice and Bob, and the probability of these 4 situations occurring is the same. There are 2 situations in total that can successfully generate keys, so the probability of successfully generating keys is 50%.

[0073] It can be seen from the above two tables that, assuming that the efficiency of multiple receiving ends is the same as that of a single receiving end, the base matching success rate of the single receiving end scheme is 50%, and the base matching success rate of the dual receiving end scheme is 75%. The dual receiving end scheme increases the key generation rate.

[0074] In an optional embodiment, when the first transmitting side random state base is the same as the i-th receiving side random state base, the transmitting device 10 is used to look up the quantum light and key mapping information, and determine the quantum key that matches the quantum light emitted by the first quantum state transmitter 101 as the current quantum key; the receiving device 20 is used to look up the quantum light and key mapping information, and determine the quantum key that matches the quantum light received by the i-th quantum state receiver 201 as the current quantum key.

[0075] Optionally, when the first transmitting-side random state basis is different from all receiving-side random state bases, the transmitting device 10 and the receiving device 20 fail to determine the basis, and the current quantum light emission cycle does not generate a quantum key.

[0076] In order to further improve the probability of generating quantum keys, the present invention also provides an optional implementation method, please refer to Figure 2 , Figure 2 The second structural diagram of the quantum key distribution system provided by the embodiment of the present invention. The transmitting device 10 is provided with M quantum state transmitters 101.

[0077] The transmitting device 10 is used to control the jth quantum state transmitter 101 to transmit quantum light in a free space channel according to the jth transmitting side random state basis within the jth interval of the current quantum light emission cycle.

[0078] The current quantum light emission cycle is divided into M intervals. In the current quantum light emission cycle, the M quantum state emitters 101 are time-division multiplexed according to the intervals, and only one quantum state emitter 101 works in each interval.

[0079] The receiving device 20 is used to control the i-th quantum state receiver 201 to receive quantum light in the j-th interval according to the i-th receiving side random state basis, where 1≤j≤M.

[0080] In each interval, the N quantum state receivers 201 need to remain in working state.

[0081] The receiving device 20 is used to transmit the i-th receiving-side random state basis corresponding to the j-th interval to the transmitting device 10 through the classical channel.

[0082] After receiving the i-th receiving-side random state base corresponding to the j-th interval, the transmitting device 10 feeds back the j-th transmitting-side random state base to the receiving device 20 through the classical channel.

[0083] When the random state basis of the i-th receiving side corresponding to the j-th interval is the same as the random state basis of the j-th transmitting side, the transmitting device 10 is used to generate the quantum key of the j-th interval based on the quantum light emitted by the j-th quantum state transmitter 101 in the j-th interval; the receiving device 20 is used to generate the quantum key of the j-th interval based on the quantum light received by the i-th quantum state receiver 201 in the j-th interval.

[0084] Optionally, the transmitting device 10 and the receiving device 20 are used to sort multiple interval quantum keys generated in the current quantum light emission cycle, and call the interval quantum keys generated in the current quantum light emission cycle according to the sorting.

[0085] Please refer to Figure 3 , Figure 3 The third structural diagram of the quantum key distribution system provided by the embodiment of the present invention. In an optional implementation, the transmitting device 10 includes a first controller 102 and M quantum state transmitters 101, the first controller 102 is connected to the M quantum state transmitters 101 respectively, and the first controller 102 is connected to the receiving device 20 via a classical channel communication.

[0086] Please continue to refer to Figure 3 The receiving device 20 includes a second controller 202 and N quantum state receivers 201. The second controller 202 is connected to the N quantum state receivers 201 respectively, and the second controller 202 is connected to the transmitting device 10 through classical channel communication.

[0087] Optionally, the second controller 202 is communicatively connected to the first controller 102 via a classical channel.

[0088] Optionally, the M quantum state transmitters 101 and the N quantum state receivers 201 are time synchronized at preset periodic intervals.

[0089] The embodiment of the present invention further provides a quantum key distribution method under a free space channel, which can be applied to but not limited to the above-mentioned quantum key distribution system, please refer to Figure 4 , Figure 4 A schematic flow chart of a quantum key distribution method under a free space channel provided by an embodiment of the present invention. The quantum key distribution method under a free space channel includes: S310, S320, S330, S340 and S350, which are specifically described as follows.

[0090] S310, the transmitting device controls the first quantum state transmitter to transmit quantum light in a free space channel according to the first transmitting side random state basis.

[0091] S320, the receiving device controls the i-th quantum state receiver to receive quantum light according to the i-th receiving side random state basis.

[0092] Among them, 1≤i≤N.

[0093] S330, the receiving device transmits the i-th receiving-side random state basis to the transmitting device through the classical channel.

[0094] S340, after receiving the i-th receiving-side random state base, the transmitting device feeds back the first transmitting-side random state base to the receiving device through the classical channel.

[0095] S350, when the random state base of the first transmitting side is the same as the random state base of the i-th receiving side, the transmitting device generates the current quantum key according to the quantum light emitted by the first quantum state transmitter, and the receiving device generates the current quantum key according to the quantum light received by the i-th quantum state receiver.

[0096] Optionally, the steps in which the transmitting device generates a current quantum key according to the quantum light emitted by the first quantum state transmitter, and the receiving device generates a current quantum key according to the quantum light received by the i-th quantum state receiver include: S351 and S352, as follows.

[0097] S351, the transmitting device searches for the mapping information between quantum light and key, and determines the quantum key that matches the quantum light emitted by the first quantum state transmitter as the current quantum key.

[0098] S352, the receiving device searches for the quantum light and key mapping information, and determines the quantum key that matches the quantum light received by the i-th quantum state receiver as the current quantum key.

[0099] It should be noted that the quantum key distribution method under the free space channel provided in this embodiment can perform the functional purposes shown in the above-mentioned quantum key distribution system embodiment under the free space channel to achieve the corresponding technical effects. For the sake of brief description, for the parts not mentioned in this embodiment, please refer to the corresponding contents in the above-mentioned embodiments.

[0100] In summary, an embodiment of the present invention provides a quantum key distribution method and system under a free space channel, wherein a transmitting device is used to control the first quantum state transmitter to transmit quantum light under a free space channel according to the first transmitting side random state basis; a receiving device is used to control the i-th quantum state receiver to receive quantum light according to the i-th receiving side random state basis, wherein 1≤i≤N; the receiving device is used to transmit the i-th receiving side random state basis to the transmitting device through a classical channel; the transmitting device is used to feed back the first transmitting side random state basis to the receiving device through a classical channel after receiving the i-th receiving side random state basis; when the first transmitting side random state basis is the same as the i-th receiving side random state basis, the transmitting device is used to generate a current quantum key according to the quantum light emitted by the first quantum state transmitter, and the receiving device is used to generate a current quantum key according to the quantum light received by the i-th quantum state receiver, thereby increasing the key generation rate.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0102] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A quantum key distribution system in a free space channel, characterized in that: The quantum key distribution system comprises a transmitting device and a receiving device, wherein the transmitting device is provided with a first quantum state transmitter, and the receiving device is provided with N quantum state receivers; The transmitting device is used to control the first quantum state transmitter to transmit quantum light in a free space channel according to the first transmitting side random state basis; The receiving device is used to control the i-th quantum state receiver to receive quantum light according to the i-th receiving side random state basis, where 1≤i≤N; The receiving device is used to transmit the i-th receiving side random state basis to the transmitting device through a classical channel; The transmitting device is used for feeding back the first transmitting side random state base to the receiving device through a classical channel after receiving the i-th receiving side random state base; When the first transmitting side random state base is the same as the i-th receiving side random state base, the transmitting device is used to generate a current quantum key based on the quantum light emitted by the first quantum state transmitter, and the receiving device is used to generate a current quantum key based on the quantum light received by the i-th quantum state receiver.

2. The quantum key distribution system under free space channel according to claim 1, characterized in that: When the first transmitting side random state basis is the same as the i-th receiving side random state basis, the transmitting device is used to search for quantum light and key mapping information, and determine the quantum key that matches the quantum light emitted by the first quantum state transmitter as the current quantum key; the receiving device is used to search for quantum light and key mapping information, and determine the quantum key that matches the quantum light received by the i-th quantum state receiver as the current quantum key.

3. The quantum key distribution system under free space channel as claimed in claim 1, characterized in that: In a case where the first transmitting-side random state basis is different from all receiving-side random state basis, the transmitting device and the receiving device are configured to determine that basis matching has failed.

4. The quantum key distribution system under free space channel according to claim 1, characterized in that: The transmitting device is provided with M quantum state transmitters; The transmitting device is used to control the jth quantum state transmitter to transmit quantum light in a free space channel according to the jth transmitting side random state basis within the jth interval of the current quantum light emission cycle; The receiving device is used to control the i-th quantum state receiver to receive quantum light in the j-th interval according to the i-th receiving side random state basis, where 1≤j≤M; The receiving device is used to transmit the i-th receiving side random state basis corresponding to the j-th interval to the transmitting device through a classical channel; After receiving the i-th receiving-side random state base corresponding to the j-th interval, the transmitting device feeds back the j-th transmitting-side random state base to the receiving device through a classical channel; When the i-th receiving side random state basis corresponding to the j-th interval is the same as the j-th transmitting side random state basis, the transmitting device is used to generate the j-th interval quantum key according to the quantum light transmitted by the j-th quantum state transmitter in the j-th interval; the receiving device is used to generate the j-th interval quantum key according to the quantum light received by the i-th quantum state receiver in the j-th interval.

5. The quantum key distribution system under free space channel as claimed in claim 4, characterized in that: The transmitting device and the receiving device are used to sort multiple interval quantum keys generated in the current quantum light emission cycle, and call the interval quantum keys generated in the current quantum light emission cycle according to the sorting.

6. The quantum key distribution system under free space channel as claimed in claim 4, characterized in that: The transmitting device includes a first controller and M quantum state transmitters, the first controller is connected to the M quantum state transmitters respectively, and the first controller is connected to the receiving device through a classical channel communication.

7. The quantum key distribution system under a free space channel according to any one of claims 1 to 6, characterized in that: The receiving device includes a second controller and N quantum state receivers, the second controller is connected to the N quantum state receivers respectively, and the second controller is connected to the transmitting device through a classical channel communication.

8. The quantum key distribution system under free space channel as claimed in claim 4, characterized in that: The M quantum state transmitters and the N quantum state receivers are time synchronized at preset periodic intervals.

9. A quantum key distribution method in a free space channel, characterized in that: The quantum key distribution system applied to any one of claims 1 to 8, wherein the method comprises: The transmitting device controls the first quantum state transmitter to transmit quantum light in a free space channel according to the first transmitting side random state basis; The receiving device controls the i-th quantum state receiver to receive quantum light according to the i-th receiving side random state basis, where 1≤i≤N; The receiving device transmits the i-th receiving-side random state basis to the transmitting device through a classical channel; After receiving the i-th receiving-side random state base, the transmitting device feeds back the first transmitting-side random state base to the receiving device through a classical channel; When the first transmitting side random state base is the same as the i-th receiving side random state base, the transmitting device generates a current quantum key based on the quantum light emitted by the first quantum state transmitter, and the receiving device generates a current quantum key based on the quantum light received by the i-th quantum state receiver.

10. The quantum key distribution method under free space channel according to claim 9, characterized in that: The step of the transmitting device generating a current quantum key according to the quantum light emitted by the first quantum state transmitter, and the receiving device generating a current quantum key according to the quantum light received by the i-th quantum state receiver comprises: The transmitting device searches for quantum light and key mapping information, and determines a quantum key that matches the quantum light emitted by the first quantum state transmitter as the current quantum key; The receiving device searches for quantum light and key mapping information, and determines a quantum key that matches the quantum light received by the i-th quantum state receiver as the current quantum key.

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