Light source device and QKD system and method suitable for double-arm channel structure QKD protocol

Abstract

The invention provides an injection locking light source device suitable for a double-arm channel structure QKD (quantum key distribution) protocol, a corresponding QKD system and an anti-injection attack method. According to the injection locking light source device, a multi-stage cascaded slave laser structure is introduced into a transmitting end to generate a laser signal for quantum state preparation; and meanwhile, the optical power of the slave laser signal is amplified to a preset value before the slave laser signal is used for a subsequent injection locking process, so that the influence of the power change of the slave laser signal on the power of a next-stage slave laser signal generated based on the injection locking process realized by the slave laser signal is eliminated. Therefore, not only is the injection port of the slave laser for the quantum state prevented from being exposed outside, but also the light intensity control range related to the master laser signal (which is attack light during attack) can be reduced by means of the multi-stage cascade injection locking scheme with the built-in optical power amplification process, and the influence of external injection attack can be weakened or eliminated to the greatest extent.

Description

Technical Field

[0001] This invention relates to the field of quantum key distribution (QKD) technology, specifically to an injection-locked light source device suitable for a two-arm channel structure QKD protocol, a corresponding QKD system, and a method for resisting injection attacks. Background Technology

[0002] Current QKD protocols include preparation-measurement protocols using single-arm channel structures, entanglement-measurement protocols using dual-arm channel structures, and MDI-QKD protocols using dual-arm channel structures, such as the standard Measurement Device Independent QKD (MDI-QKD) protocol, the Two-Field QKD (TF-QKD) protocol, and the Mode Matching QKD (MP-QKD) protocol, which falls between the two. Among these, the TF-QKD protocol is currently the most advantageous QKD scheme for long-distance fiber optic applications. Theoretically, TF-QKD has demonstrated its advantages in long-distance operation and high security. Scientific experiments have verified the advanced performance of the TF-QKD protocol, and field experiments have experimentally verified its practical feasibility, thus paving the way for the practical application of long-distance fiber optic QKD.

[0003] The MDI-QKD protocol, which uses a dual-arm channel structure, is based on interference from independent light sources. The dual-arm channel structure forms a "giant interferometer." The performance of this interferometer is affected by the different sources of the two interference pulses, thus requiring a light source locking technique to address this issue.

[0004] like Figure 1 The structural principle diagram of the dual-arm channel structure QKD protocol is shown. For example, in the TF-QKD protocol, the two transmitters, Alice and Bob, use independent light sources to generate independent optical pulses. These pulses arrive at the receiver, Charlie, along different paths, Alice-Charlie and Bob-Charlie. Therefore, the two optical pulses before interference are different in both their source and transmission path, and their global phases before interference cannot be canceled, thus affecting interference and requiring monitoring and feedback. The contribution of the global phase difference includes the phase difference contributed by the independent light sources and the phase difference contributed by the independent channels. The frequency-locked phase-locked technology of the light sources can control the initial laser phase difference and laser frequency difference between the two independent light sources.

[0005] The purpose of light source frequency-locked phase-locked technology is to ensure a fixed laser phase difference and a consistent laser frequency difference, exhibiting twin characteristics. According to its technical system, light source frequency-locked phase-locked technology can be divided into three categories: time-frequency disissemination-based technology, optical phase-locked loop (OPLL), and laser injection technology. Among these, laser injection technology is the simplest to operate and most readily practical. Figure 2 As shown in the principle framework diagram, in the injection-locking scheme, the master laser is placed at the Charlie end. By directly injecting the master laser into the slave lasers at the Alice and Bob ends, the phases of the slave lasers at the Alice and Bob ends can be locked to the phase of the master laser at the Charlie end. This method achieves laser phase locking without active compensation.

[0006] However, existing injection-locking schemes may have security vulnerabilities. For example, an attacker could use a specific attack beam and adjust its intensity to alter the actual intensity of the laser in the Alice or Bob terminal, thus deviating from the expected intensity of the decoy state theory (generally resulting in an actual intensity higher than the expected intensity), leading to real-world security risks. Therefore, the security of injection-locking technology remains to be addressed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes an injection-locked light source device, a corresponding QKD system, and an anti-injection attack method suitable for a dual-arm channel structure QKD protocol. When implementing the transmitter light source using injection locking, a multi-stage cascaded slave laser structure is introduced at the transmitter to generate the laser signal for quantum state preparation. Simultaneously, the optical power of the slave laser signal is amplified to a preset value before being used in the subsequent injection-locking process, eliminating the influence of slave laser signal power variations on the power of the next-stage slave laser signal generated based on it in the injection-locking process. This not only avoids exposing the injection port of the slave laser used for quantum states to the outside, but also, through this multi-stage cascaded injection-locking scheme with built-in optical power amplification, reduces the intensity control range related to the master laser signal (which becomes the attack beam during an attack), minimizing or eliminating the impact of external injection attacks.

[0008] Specifically, the first aspect of the present invention relates to a QKD system based on a dual-arm channel structure, which includes two transmitting ends and a receiving end;

[0009] The receiving end is equipped with a main laser and a beam splitting module. The main laser is configured to output a main laser signal, and the beam splitting module is configured to split the main laser signal into two main laser signal components and transmit them to two transmitting ends respectively.

[0010] The transmitting end is equipped with a slave laser module, which includes N cascaded slave lasers, where N is a positive integer greater than 1;

[0011] The first of the N slave lasers is configured to generate a first-level slave laser signal using the master laser signal component in an injection-locked manner;

[0012] The (i+1)th of the N slave lasers is configured to generate the (i+1)th level slave laser signal using the i-th level slave laser signal generated by the i-th slave laser, in an injection-locked manner, where i is a natural number from 1 to N-1;

[0013] An optical amplification module is provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers. This module is used to amplify the optical power of the k-th slave laser signal to a preset value before it enters the (k+1)-th slave laser. The value of k is one or more natural numbers from 1 to N-1.

[0014] Furthermore, the slave laser module further includes a channel compensation module configured to perform at least one of polarization feedback, light intensity amplification, and noise filtering on the main laser signal component; and / or, an attenuator for the power-amplified slave laser signal is further provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers; and / or, an optical amplifier is provided between the main laser and the slave laser module.

[0015] Furthermore, the laser module also includes N optical transmission units, each having three ports and configured such that optical signals entering from port 1 are output from port 2, and optical signals entering from port 2 are output from port 3.

[0016] The j-th of the N optical transmission units is configured to allow an optical signal to be injected into the j-th of the N slave lasers via ports 1 and 2, and the j-th level slave laser signal output from the j-th of the N slave lasers is output via ports 2 and 3, where j is a natural number from 1 to N; and,

[0017] The optical amplification module is located between the third port of the k-th optical transmission unit and the first port of the (k+1)-th optical transmission unit.

[0018] Preferably, the optical transmission unit is a beam splitter or an optical fiber circulator.

[0019] Optionally, the QKD system of the present invention may employ the MDI-QKD protocol, the TF-QKD protocol, or the MP-QKD protocol.

[0020] A second aspect of the invention relates to an injection-locked light source device suitable for the QKD protocol of a dual-arm channel structure, comprising a master laser, a beam splitter module, and two slave laser modules;

[0021] The main laser is configured to output the main laser signal;

[0022] The beam splitting module is configured to split the main laser signal into two main laser signal components and transmit them to two slave laser modules respectively.

[0023] The slave laser module includes N cascaded slave lasers, where N is a positive integer greater than 1;

[0024] The first of the N slave lasers is configured to generate a first-level slave laser signal using the master laser signal component in an injection-locked manner;

[0025] The (i+1)th of the N slave lasers is configured to generate the (i+1)th level slave laser signal using the i-th level slave laser signal generated by the i-th slave laser, in an injection-locked manner, where i is a natural number from 1 to N-1;

[0026] An optical amplification module is provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers. This module is used to amplify the optical power of the k-th slave laser signal to a preset value before it enters the (k+1)-th slave laser. The value of k is one or more natural numbers from 1 to N-1.

[0027] Preferably, the optical amplification module is configured to amplify the laser signal to a power saturation state.

[0028] Furthermore, the laser module also includes N optical transmission units, each having three ports and configured such that optical signals entering from port 1 are output from port 2, and optical signals entering from port 2 are output from port 3.

[0029] The j-th of the N optical transmission units is configured to allow an optical signal to be injected into the j-th of the N slave lasers via ports 1 and 2, and the j-th level slave laser signal output from the j-th of the N slave lasers is output via ports 2 and 3, where j is a natural number from 1 to N; and,

[0030] The optical amplification module is located between the third port of the k-th optical transmission unit and the first port of the (k+1)-th optical transmission unit.

[0031] Preferably, the optical transmission unit is a beam splitter or an optical fiber circulator.

[0032] Furthermore, the slave laser module further includes a channel compensation module configured to perform at least one of polarization feedback, intensity amplification, and noise filtering on the master laser signal component; and / or, the QKD protocol is an MDI-QKD protocol, a TF-QKD protocol, or an MP-QKD protocol; and / or, an attenuator for the power-amplified slave laser signal is further provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers; and / or, an optical amplifier is provided between the master laser and the slave laser module.

[0033] A third aspect of the present invention relates to a method for resisting injection attacks applicable to the QKD protocol with a two-arm channel structure, comprising the following steps:

[0034] The main laser signal output from the main laser is divided into two main laser signal components, which are then transmitted to two different transmitters.

[0035] In each of the two transmitting ends, N cascaded slave lasers are configured. The first of the N slave lasers generates a first-level slave laser signal using the master laser signal component in an injection-locked manner. The (i+1)th of the N slave lasers generates an (i+1)th-level slave laser signal using the i-th-level slave laser signal in an injection-locked manner, where i is a natural number from 1 to N-1. Before the k-th-level slave laser signal enters the (k+1)-th slave laser, its optical power is amplified to a preset value using an optical amplification module. N is a positive integer greater than 1, and k takes one or more natural numbers from 1 to N-1.

[0036] Quantum states are prepared from laser signals using the Nth level.

[0037] Furthermore, the anti-injection attack method of the present invention further includes the steps of performing polarization feedback, light intensity amplification, and noise filtering on the main laser signal component; and / or, attenuating the power-amplified slave laser signal; and / or, amplifying the main laser signal and / or the main laser signal component; and / or, the preset value is a power saturation value.

[0038] Preferably, the anti-injection attack method of the present invention can be implemented using the QKD system of the present invention. Attached Figure Description

[0039] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This diagram illustrates the structural principle of the existing dual-arm channel structure QKD protocol.

[0042] Figure 2 A schematic diagram illustrating the principle framework of a prior art injection locking scheme is shown.

[0043] Figure 3 A schematic diagram of the injection-locked light source device according to the present invention, applicable to the QKD protocol of a dual-arm channel structure, is shown. Detailed Implementation

[0044] In the following description, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example in order to fully convey the spirit of the invention to those skilled in the art. Therefore, the invention is not limited to the embodiments disclosed herein.

[0045] Figure 3 A schematic diagram of the injection-locked light source device according to the present invention, applicable to the QKD protocol of a dual-arm channel structure, is shown.

[0046] like Figure 3 As shown, the injection-locked light source device of the present invention may include a master laser #0, a beam splitting module and two slave laser modules.

[0047] In a QKD system based on a dual-arm channel structure, which includes a receiver and two transmitters (e.g., Alice / Bob), the master laser #0 and the beam splitter module can be located in the receiver, while the two slave laser modules can be located in the two transmitters respectively.

[0048] like Figure 3 As shown, after the main laser #0 generates and outputs the main laser signal, the beam splitting module divides the main laser signal into two main laser signal components and transmits them to two transmitters respectively, so as to inject them into the corresponding two slave laser modules.

[0049] As an example, a beam splitter module can be implemented using a beam splitter (BS).

[0050] Preferably, an optical amplifier can be placed between the master laser #0 and the slave laser module to amplify the master laser signal (components) and compensate for the attenuation of the channel itself to ensure the success of the first-stage injection locking based on the master laser signal components. This preferred configuration is particularly advantageous for applications involving long-distance channels.

[0051] See also Figure 3 The slave laser module of the present invention may include N cascaded slave lasers (e.g., first slave laser #1, second slave laser #2, ...), where N is a positive integer greater than 1.

[0052] In the slave laser module, the first of the N slave lasers (e.g., slave laser #1) will generate and output the first-level slave laser signal using the master laser signal component in an injection-locked manner.

[0053] In a cascaded configuration, the (i+1)th slave laser in the laser module (e.g., the second slave laser #2) can allow the injection of the i-th level slave laser signal generated by the i-th slave laser. This i-th level slave laser signal is then used to generate the (i+1)-th level slave laser signal in an injection-locked manner, where i is a natural number from 1 to N-1. Finally, the laser module outputs the N-th level slave laser signal, which can be used for applications such as the preparation of quantum states.

[0054] To improve resistance to injection attacks, in the slave laser module of the present invention, an optical amplification module (e.g., an optical amplifier) ​​is also provided between two adjacent cascaded slave lasers (e.g., the kth and k+1th slave lasers) to amplify the optical power of the slave laser signal generated by the previous stage slave laser to a preset (fixed) value before it is used in the injection locking process, thereby eliminating the influence of the power variation of the slave laser signal on the power of the next stage slave laser signal generated based on the injection locking process.

[0055] According to the present invention, an optical amplification module can be arranged between one or more sets of two adjacent cascaded slave lasers. For example, an optical amplification module can be arranged between the first (i.e., when k takes the value of 1) slave laser (slave laser #1) and the second slave laser (slave laser #2) to amplify the optical power of the first-stage slave laser signal to a preset value by using the optical amplification module before the first-stage slave laser signal enters the second slave laser. At the same time, an optical amplification module can also be arranged between the second (i.e., when k takes the value of 2) slave laser (slave laser #2) and the third slave laser (not shown) to amplify the optical power of the second-stage slave laser signal to a preset value by using the optical amplification module before the second-stage slave laser signal enters the third slave laser. Therefore, those skilled in the art can know that k can take one or more natural numbers from 1 to N - 1. When the number of values of k is 1, it means that an optical amplification module is only arranged between one set of two adjacent cascaded slave lasers. When the number of values of k is multiple, it means that optical amplification modules are respectively arranged between the corresponding multiple sets of two adjacent cascaded slave lasers.

[0056] Furthermore, the optical amplification module is preferably arranged to amplify the slave laser signal to (close to) the power saturation state, that is, the preset value is the power saturation value. With the above-mentioned cascaded slave laser structure, for the last-stage (the Nth stage) slave laser (the optical signal generated and output by which will be used for quantum state preparation), its injection port only allows the injection of the slave laser signal output by the previous-stage slave laser and is not exposed to the outside, thus reducing the potential risk (the power of the quantum optical laser changes greatly due to the injection locking attack) when the port is exposed to the outside. At the same time, in this N (N > 1)-stage cascaded slave laser structure, the controlled change of the optical intensity caused by injection locking will be weaker stage by stage. That is, if the optical intensity change range of the master laser is G0, the optical intensity change range G1 of the first-stage slave laser #1 is G1 < G0, and correspondingly, the optical intensity change range G2 of the second-stage slave laser #2 is G2 < G1. On this basis, by means of the optical amplification module arranged between, for example, slave laser #1 and slave laser #2, the optical power of the slave laser signal emitted from slave laser #1 is amplified to a preset value (preferably the power saturation value), and the optical power of the slave laser emitted from slave laser #1 before amplification can be within a large power range and finally mapped to the preset power value (such as the power saturation value) after amplification. At this time, the optical power change range G1' of the slave laser signal emitted from slave laser #1 before being injected into slave laser #2 will be further reduced, that is, G1' < G1 (when there is no optical amplification), and finally, the optical power change range after slave laser #I is injected into slave laser #2 can be further reduced to G2' < G2 (when there is no optical amplification).

[0057] Therefore, by setting an N-stage cascaded slave laser structure with a built-in optical power amplification process as the light source for the quantum state at the transmitting end, even if an attacker attempts to adjust the intensity of the attack light (which is equivalent to the main laser signal component at this time) to change the intensity of the quantum state in the transmitting end to carry out an attack, the range of light intensity variation caused by the intensity modulation of the attack light can be effectively reduced (theoretically minimized), thus eliminating the attack effect.

[0058] Those skilled in the art will understand that, in order to achieve the injection-locked emission mode, the wavelength of the master laser #0 needs to be selected such that the difference between it and the wavelength of the first-stage slave laser #1 meets the injection-locking requirement, and the wavelength of the i-th-stage slave laser needs to be selected such that the difference between it and the wavelength of the (i+1)-th-stage slave laser meets the injection-locking requirement.

[0059] As an example, the master laser #0 can adopt a continuous light emission mode, and the slave lasers can adopt either a continuous light emission mode or a pulsed light emission mode. When all slave lasers adopt a pulsed light emission mode, the relative delay between the pulsed light signals of the slave lasers should be set such that the pulsed light signal of the i-th slave laser can cover the pulsed light signal of the (i+1)-th slave laser in time, thereby satisfying the injection locking requirement.

[0060] Optionally, corresponding to the optical amplification module, an attenuator can be provided between two adjacent cascaded slave lasers (e.g., the k-th slave laser and the (k+1)-th slave laser) among the N slave lasers. This attenuator is positioned after the optical amplification module in the direction of the slave laser signal transmission and is used to provide appropriate attenuation to the power-amplified slave laser signal as needed, so that the optical power of the slave laser signal is at a level suitable for successful injection locking of the next-stage slave laser. Those skilled in the art will understand that such an attenuator is unnecessary, as the power-amplified slave laser signal may already meet the power requirements of the corresponding injection locking process without attenuation.

[0061] See further Figure 3 In the slave laser module of the present invention, N slave lasers can be cascaded using N optical transmission units to achieve the required structure.

[0062] like Figure 3 As shown, the optical transmission unit can have three ports, configured such that an optical signal entering from port 1 is output from port 2, and an optical signal entering from port 2 is output from port 3. Correspondingly, in the slave laser module, the j-th optical transmission unit (j being a natural number from 1 to N) among the N slave lasers is configured to allow an optical signal to be injected into the j-th slave laser among the N slave lasers via ports 1 and 2, and the j-th stage slave laser signal output from the j-th slave laser among the N slave lasers is output via ports 2 and 3, thereby achieving the desired cascaded structure.

[0063] Accordingly, the optical amplification module can be set between the 3rd port of the kth optical transmission unit and the 1st port of the (k+1)th optical transmission unit, that is, between the 3rd port of one of two adjacent optical transmission units and the 1st port of the other.

[0064] As an example, the optical transmission unit can be a fiber optic circulator (FCIR) or a beam splitter.

[0065] Therefore, in Figure 3 In the slave laser module shown, when the master laser signal component arrives at the slave laser module, it first enters the slave laser #1 through the first and second ports of the optical transmission unit #1 to inject and lock the slave laser #1; the locked slave laser #1 then generates the first-level slave laser signal in the manner of injection locking.

[0066] The first-stage laser signal is output through ports 2 and 3 and then transmitted toward slave laser #2. After being amplified by the optical amplifier module and optionally attenuated by the attenuator, the first-stage laser signal enters slave laser #2 through ports 1 and 2 of the optical transmission unit #2, and is injected and locked into slave laser #2. The locked slave laser #2 then generates the second-stage laser signal in the manner of injection locking.

[0067] The second-stage laser signal is output through ports 2 and 3 and then transmitted to the next-stage laser or used to prepare quantum states.

[0068] See also Figure 3 Furthermore, a channel compensation module can be set in the laser module to perform at least one of polarization feedback, light intensity amplification, and noise filtering on the main laser signal component, thereby improving the performance of the main laser signal.

[0069] In addition to the injection-locked light source device and corresponding QKD system based on the dual-arm channel structure QKD protocol described above, this invention also discloses an anti-injection attack method for the dual-arm channel structure QKD protocol, which is particularly suitable for implementation using the QKD system or light source device of this invention.

[0070] Based on a similar principle, the anti-injection attack method of the present invention provides a laser signal for quantum state preparation by utilizing a multi-level injection locking method to resist injection locking attacks against QKD systems based on a two-arm channel structure.

[0071] Specifically, in the anti-injection attack method of the present invention, the main laser signal output by the main laser is first divided into two main laser signal components, which are then transmitted to two transmitting ends respectively. Preferably, in long-distance channel applications, the main laser signal (components) is amplified to compensate for the attenuation of the channel itself, ensuring the success of the first-level injection lock.

[0072] By setting N cascaded slave lasers in each of the two transmitting ends, the first of the N slave lasers generates a first-level slave laser signal using the master laser signal component in an injection-locked manner, and the (i+1)th of the N slave lasers generates an (i+1)th-level slave laser signal using the i-th-level slave laser signal in an injection-locked manner, ultimately obtaining the N-th-level slave laser signal. Before the k-th-level slave laser signal enters the (k+1)-th slave laser, its optical power can be amplified to a preset value using an optical amplification module, where k takes one or more natural numbers from 1 to N-1.

[0073] Therefore, by utilizing the Nth-level slave laser signal to prepare the quantum state, the optical signal used for preparing the quantum state can be avoided by directly generating it from the injected attack light. This effectively eliminates the influence of the attack light on the intensity of the quantum state signal, thus achieving resistance to injection attacks. Particularly innovative is the use of a laser signal k from the previous-level slave laser k to achieve the injection locking process for slave laser k+1. This involves using an optical amplification module to amplify the optical power of the slave laser signal to, for example, an optimal power saturation state. This ensures that the slave laser signal before amplification can be mapped to a saturation power over a wide power range, thereby maximally eliminating the intensity control range associated with the main laser signal (which becomes the attack light during an attack), thus providing optimal defense against external injection attacks.

[0074] Furthermore, the anti-injection attack method of the present invention may also include at least one of polarization feedback, light intensity amplification, and noise filtering of the main laser signal component to improve the performance of the main laser signal.

[0075] Furthermore, the anti-injection attack method of the present invention may also include the step of attenuating the power-amplified laser signal so that its power value is suitable for the subsequent injection locking process.

[0076] Those skilled in the art will understand that the light source, QKD system, and anti-injection attack method proposed in this invention can be applied to any QKD protocol based on a dual-arm channel structure, including but not limited to MDI-QKD protocol, TF-QKD protocol, or MP-QKD protocol.

[0077] Although the present invention has been described above with reference to the accompanying drawings and specific embodiments, those skilled in the art will readily recognize that the above embodiments are merely exemplary and used to illustrate the principles of the present invention. They do not limit the scope of the present invention. Those skilled in the art can make various combinations, modifications and equivalent substitutions to the above embodiments without departing from the spirit and scope of the present invention.

Claims

1. A QKD system based on a dual-arm channel structure, comprising two transmitters and two receivers; The receiver includes a main laser and a beam splitter module. The main laser is configured to output a main laser signal, and the beam splitting module is configured to split the main laser signal into two main laser signal components and transmit them to two transmitting ends respectively. The transmitting end is equipped with a slave laser module, which includes N cascaded slave lasers, where N is a positive integer greater than 1; The first of the N slave lasers is configured to generate a first-level slave laser signal using the master laser signal component in an injection-locked manner; The (i+1)th of the N slave lasers is configured to generate the (i+1)th level slave laser signal using the i-th level slave laser signal generated by the i-th slave laser, in an injection-locked manner, where i is a natural number from 1 to N-1; An optical amplification module is provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers. This module is used to amplify the optical power of the k-th slave laser signal to a preset value before it enters the (k+1)-th slave laser. The value of k is one or more natural numbers from 1 to N-1.

2. The QKD system as described in claim 1, wherein, The slave laser module further includes a channel compensation module configured to perform at least one of polarization feedback, intensity amplification, and noise filtering on the main laser signal component; and / or An attenuator for the power-amplified slave laser signal is further provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers; and / or, An optical amplifier is provided between the master laser and the slave laser module.

3. The QKD system as described in claim 1, wherein, The laser module also includes N optical transmission units, each having three ports and configured such that optical signals entering from port 1 are output from port 2, and optical signals entering from port 2 are output from port 3. The j-th of the N optical transmission units is configured to allow an optical signal to be injected into the j-th of the N slave lasers via ports 1 and 2, and the j-th level slave laser signal output from the j-th of the N slave lasers is output via ports 2 and 3, where j is a natural number from 1 to N; and, The optical amplification module is located between the third port of the k-th optical transmission unit and the first port of the (k+1)-th optical transmission unit.

4. The QKD system as described in claim 3, wherein, The optical transmission unit is a beam splitter or an optical fiber circulator.

5. The QKD system as described in any one of claims 1-4, wherein it employs the MDI-QKD protocol, the TF-QKD protocol, or the MP-QKD protocol.

6. An injection-locked light source device suitable for the QKD protocol of a dual-arm channel structure, comprising a master laser, a beam splitter module, and two slave laser modules; The main laser is configured to output the main laser signal; The beam splitting module is configured to split the main laser signal into two main laser signal components and transmit them to two slave laser modules respectively. The slave laser module includes N cascaded slave lasers, where N is a positive integer greater than 1; The first of the N slave lasers is configured to generate a first-level slave laser signal using the master laser signal component in an injection-locked manner; The (i+1)th of the N slave lasers is configured to generate the (i+1)th level slave laser signal using the i-th level slave laser signal generated by the i-th slave laser, in an injection-locked manner, where i is a natural number from 1 to N-1; in, An optical amplification module is provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers. This module is used to amplify the optical power of the k-th slave laser signal to a preset value before it enters the (k+1)-th slave laser. The value of k is one or more natural numbers from 1 to N-1.

7. The injection locking light source device as described in claim 6, wherein, The optical amplification module is configured to amplify the laser signal to a power saturation state.

8. The injection locking light source device as described in claim 6, wherein, The laser module also includes N optical transmission units, each having three ports and configured such that optical signals entering from port 1 are output from port 2, and optical signals entering from port 2 are output from port 3. The j-th of the N optical transmission units is configured to allow an optical signal to be injected into the j-th of the N slave lasers via ports 1 and 2, and the j-th level slave laser signal output from the j-th of the N slave lasers is output via ports 2 and 3, where j is a natural number from 1 to N; and, The optical amplification module is located between the third port of the k-th optical transmission unit and the first port of the (k+1)-th optical transmission unit.

9. The injection locking light source device as described in claim 8, wherein, The optical transmission unit is a beam splitter or an optical fiber circulator.

10. The injection-locking light source device as described in claim 6, wherein, The slave laser module further includes a channel compensation module, which is configured to perform at least one of polarization feedback, light intensity amplification, and noise filtering on the main laser signal component. And / or, the QKD protocol is an MDI-QKD protocol, a TF-QKD protocol, or an MP-QKD protocol; And / or, an attenuator for the power-amplified slave laser signal is further provided between the k-th slave laser and the (k+1)-th slave laser among the N slave lasers; And / or, an optical amplifier is provided between the master laser and the slave laser module.

11. A method for resisting injection attacks applicable to the QKD protocol with a two-arm channel structure, comprising the following steps: The main laser signal output from the main laser is divided into two main laser signal components, which are then transmitted to two different transmitters. In each of the two transmitting ends, N cascaded slave lasers are configured. The first of the N slave lasers generates a first-level slave laser signal using the master laser signal component in an injection-locked manner. The (i+1)th of the N slave lasers generates an (i+1)th-level slave laser signal using the i-th-level slave laser signal in an injection-locked manner, where i is a natural number from 1 to N-1. Before the k-th-level slave laser signal enters the (k+1)-th slave laser, its optical power is amplified to a preset value using an optical amplification module. N is a positive integer greater than 1, and k takes one or more natural numbers from 1 to N-1. Quantum states are prepared from laser signals using the Nth level.

12. The anti-injection attack method as described in claim 11, further comprising the step of performing at least one of polarization feedback, intensity amplification, and noise filtering on the main laser signal component; And / or, the step of attenuating the power-amplified laser signal; And / or, the step of amplifying the main laser signal and / or the main laser signal components; And / or, the preset value is the power saturation value.

13. The anti-injection attack method as described in claim 11, which is implemented by means of the QKD system as described in any one of claims 1-5.

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