Method, device and equipment for generating target evaluation light pulses

Abstract

The application discloses a target evaluation light pulse generation method, device and equipment, which is used in a quantum key distribution system and comprises the following steps: generating light pulses constituting a first light emission sequence; modulating the light pulses constituting the first light emission sequence to generate light pulses constituting a second light emission sequence, wherein the light pulses in the second light emission sequence have different encoding states; and according to the evaluation requirements, extinguishing the light pulses with non-target encoding states in the second light emission sequence and retaining the light pulses with target encoding states to generate target evaluation light pulses constituting a third light emission sequence. The application can obtain more accurate state parameters of the light pulse signals of each encoding state without changing the normal working state of the light source module of the quantum key distribution system, so as to meet the evaluation requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of quantum secure communication, and in particular to a method and device for generating target evaluation light pulses for a quantum key distribution system. BACKGROUND

[0002] Quantum Key Distribution (QKD) technology has attracted wide attention because it can generate completely consistent unconditionally secure keys between the two communicating parties. Since the BB84 scheme was proposed in 1984, various theoretical schemes have been perfected, and the technology has gradually matured and moved towards practical application. The fundamental difference between quantum key distribution and classical key systems is that quantum key distribution uses single photons or entangled photon pairs as the carrier of the key, and the three basic principles of quantum mechanics (i.e., the Heisenberg uncertainty principle, the measurement collapse theory, and the quantum no-cloning theorem) ensure the unbreakable and unbreakable nature of the process, thereby providing a more secure key system.

[0003] Currently, since the single photon source technology cannot meet the practical requirements, the practical quantum key distribution system uses a coherent light source with strong attenuation to obtain weak coherent light. However, weak coherent state light contains multiple photon components with a certain probability, so the eavesdropper can perform a separation photon number attack, which greatly limits the security code rate. In this context, people have proposed decoy state BB84 quantum key distribution protocols to defend against attacks. Specifically, by randomly doping some decoy light of different intensities in the signal light emitted by the laser, the influence of the channel and the eavesdropper on the light pulse is monitored. Combined with the decoy state technology, even if a weak coherent light source is used, the code rate of the BB84 protocol is almost the same as that of the protocol using an ideal single photon source. Therefore, in the laboratory and engineering practice, the decoy state BB84 quantum key distribution protocol is widely adopted.

[0004] The quantum key distribution system based on the BB84 quantum key distribution protocol includes a light source module and a modulation module in the transmitting end light source part. The light source module emits light signals, and the modulation module performs quantum state modulation and intensity modulation (i.e., decoy state modulation) on the emitted light signals. The quantum state modulation includes four different quantum states in phase or polarization, i.e., phase state (temporal phase state) or polarization state, which can be represented by two random numbers. The intensity modulation includes multiple different intensities, such as typical signal states, decoy states, and vacuum states. The three different intensities are generally set according to a certain ratio, such as 6:1:1, which requires three random numbers to represent. Taking the polarization encoding method and the decoy state ratio of 6:1:1 as an example, the light emission encoding method is as follows: Figure 1The polarizations H, V, P and N represent the four kinds of polarizations of the light signals emitted by the light source part of the transmitting end of the quantum key distribution system, respectively.

[0005] With the development of quantum key distribution technology, the importance of evaluating its actual security is increasingly highlighted. When performing indistinguishable quantum evaluation on the random states of each encoding of the quantum key distribution system, the light source part of the transmitting end of the quantum key distribution system usually emits light of a specific state, such as only signal state light, to perform relevant physical quantity measurement, for example, measuring the wavelength, amplitude, timing and other state parameters of the specific state light, while other non-specific states are avoided from causing interference or errors during measurement by not emitting light. Specifically, the external evaluation software issues an instruction to emit a certain specific state light, and the light source part of the transmitting end of the quantum key distribution system outputs the specific state light required for evaluation according to the received instruction.

[0006] Figure 2 The light emission sequence and the timing of the modulation of the light source module of the transmitting end of the quantum key distribution system when extracting the specific state light (e.g., signal state light S or polarization state light H) required for evaluation in the prior art are shown in the timing diagram. Specifically, the process of extracting the specific state light required for evaluation in the prior art mainly includes the following steps (the order of steps S3 and S4 can be interchanged):

[0007] Step S1: The evaluation software issues an instruction that the evaluation target is a certain specific state light (specific encoding);

[0008] Step S2: The light source module of the transmitting end of the quantum key distribution system emits light only at the specific state (specific encoding) position according to the random encoding, and does not emit light at the remaining non-specific state position, thereby forming a light emission sequence; or the light source module can emit periodic light of the specific state;

[0009] Step S3: The light pulses of the light emission sequence are modulated into corresponding signal states, decoy states or vacuum states by the decoy state modulation module, i.e., intensity modulation is performed on the light pulses;

[0010] Step S4: The light emission sequence modulated in step 3 is modulated into corresponding polarization states or phase states by the quantum state modulation module, i.e., quantum state modulation is performed on the light pulses;

[0011] Step S5: Output the specific state light pulses modulated by the decoy state modulation and the quantum state modulation, which are required for evaluation.

[0012] Note that, Figure 2The solid line block in the middle represents a specific state light pulse (e.g., polarization state H or signal state S) required for measurement, while the dashed line block represents a light pulse (e.g., polarization states V, P, N, or decoy state D and vacuum state V) not required for measurement.

[0013] However, in the normal working phase, the light emission mode of the light source module of the quantum key distribution system is a true random sequence (i.e., a random light pulse controlled based on a random number), and the intensity modulation and quantum state modulation are both realized by external modulation; without loss of generality, the light source module can emit periodic light. Figure 3 A comparison diagram of the light emission sequence output by the light source module in the normal working phase of the quantum key distribution system and the light emission sequence output by the light source module in the prior art measurement phase is shown. As shown in Figure 3 The light emission sequence of the light source module in the prior art measurement phase and the true random (including periodic) light emission sequence in the normal working phase of the system are inconsistent. Specifically, the prior art changes the state of the light source module in the normal working phase, so that the light emission sequence of the output light source does not emit light at the non-required state position (as shown by the dashed line in Figure 3 The state parameters (such as wavelength, amplitude, timing, etc.) of the light source are usually closely related to the light emission sequence, and if the duty cycles of the light pulse signals with different encoding states (such as the four polarization states H, V, P, and N) are different, the state parameters of the respective light emission sequences can be different. Therefore, the light emission mode of the prior art (i.e., emitting light only at the specific state position required for measurement) can cause the measurement result to deviate from the actual working state of the quantum key distribution system, especially when measuring the consistency of the modes of each encoding state (e.g., wavelength mode, time mode, etc.), the different duty cycles result in different light emission sequences of the light source, so that the measurement results of the state parameters of the light pulse signals of each encoding state are affected by the different light emission sequences, resulting in differences, which cannot reflect the consistency of the encoding state itself, and finally can cause a false judgment of the security of the quantum key distribution system. SUMMARY

[0014] To solve the above problems, the present application provides a method, device and equipment for generating target measurement light pulses for a quantum key distribution system, which can obtain more accurate state parameters of the light pulse signals of each encoding state without changing the working state of the light source module of the transmitting end of the quantum key distribution system, to meet the requirements of measurement.

[0015] Embodiments of the present application provide a method for generating target evaluation light pulses, which is used in a quantum key distribution system, comprising: generating light pulses constituting a first light emission sequence; modulating the light pulses constituting the first light emission sequence to generate light pulses constituting a second light emission sequence, wherein the light pulses in the second light emission sequence have different encoding states; and according to an evaluation requirement, extinguishing the light pulses in the second light emission sequence having non-target encoding states and retaining the light pulses having target encoding states to generate target evaluation light pulses constituting a third light emission sequence.

[0016] Further, the encoding states include at least one of quantum states and intensity states.

[0017] Further, the method further comprises at least one of quantum state modulation and intensity modulation of the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the quantum state modulation comprises polarization quantum state modulation, time phase quantum state modulation or phase quantum state modulation of the light pulses in the first light emission sequence.

[0018] Further, the method further comprises: quantum state modulation and / or intensity modulation of the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different quantum states and / or intensity states; and according to the evaluation requirement, extinguishing the light pulses in the second light emission sequence having non-target quantum states and / or intensity states and retaining the light pulses having target quantum states and / or intensity states to generate the target evaluation light pulses.

[0019] Further, the method further comprises: when the evaluation requirement indicates that the target evaluation light pulses are light pulses having target quantum states, quantum state modulation of the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different quantum states; and through the intensity modulation, modulating the light pulses in the second light emission sequence having target quantum states to have preset intensity states and modulating the light pulses in the second light emission sequence having non-target quantum states to have non-preset intensity states, wherein the non-preset intensity states are extinction states.

[0020] Further, the method further comprises: when the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target intensity state, intensity-modulating the light pulses in the first light-emitting sequence to generate the second light-emitting sequence, wherein the light pulses in the second light-emitting sequence have different intensity states; modulating the light pulses with the target intensity state in the second light-emitting sequence into a preset temporal quantum state and modulating the light pulses with a non-target intensity state in the second light-emitting sequence into a non-pre-set temporal quantum state through the temporal phase quantum state modulation; and extinguishing the light pulses with the non-pre-set temporal quantum state through an optical attenuator, thereby retaining the light pulses with the preset temporal quantum state.

[0021] Further, the method further comprises: when the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target intensity state, intensity-modulating the light pulses in the first light-emitting sequence to generate the second light-emitting sequence, wherein the light pulses in the second light-emitting sequence have different intensity states; modulating the light pulses with the target intensity state in the second light-emitting sequence into a preset polarization quantum state and modulating the light pulses with a non-target intensity state in the second light-emitting sequence into a non-pre-set polarization quantum state through the polarization quantum state modulation; and retaining the light pulses with the preset polarization quantum state and extinguishing the light pulses with the non-pre-set polarization quantum state through a polarization filter.

[0022] Embodiments of the present application also provide a device for generating a target evaluation light pulse, used in a quantum key distribution system, comprising: a light source module for emitting light pulses constituting a first light-emitting sequence; a modulation module for modulating the light pulses in the first light-emitting sequence to generate light pulses constituting a second light-emitting sequence, wherein the light pulses in the second light-emitting sequence have different encoding states; and an extinction module for extinguishing light pulses with a non-target encoding state in the second light-emitting sequence and retaining light pulses with a target encoding state according to an evaluation requirement to generate target evaluation light pulses constituting a third light-emitting sequence; and a control module for sending control signals to the light source module, the modulation module and the extinction module to drive the light source module, the modulation module and the extinction module to work cooperatively.

[0023] Further, the encoding state comprises at least one of a quantum state and an intensity state.

[0024] Further, the modulation module comprises a quantum state modulation unit and / or a state of polarization modulation unit, for performing quantum state modulation and / or intensity modulation on the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different quantum states and / or intensity states; and the extinction module is an extinction modulator, for performing extinction on the light pulses in the second light emission sequence having non-target quantum states and / or intensity states and retaining the light pulses having target quantum states and / or intensity states according to the evaluation requirement, to generate the target evaluation light pulses.

[0025] Further, the modulation module comprises a quantum state modulation unit, for performing quantum state modulation on the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different quantum states; and the extinction module comprises a state of polarization modulation unit, for modulating the light pulses in the second light emission sequence having target quantum states to have preset intensity states, and modulating the light pulses in the second light emission sequence having non-target quantum states to have non-preset intensity states, wherein the non-preset intensity states are extinction states.

[0026] Further, the modulation module comprises a state of polarization modulation unit, for performing intensity modulation on the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different intensity states; and the extinction module comprises a time phase quantum state modulation unit, for modulating the light pulses in the second light emission sequence having target intensity states to have preset time quantum states, and modulating the light pulses in the second light emission sequence having non-target intensity states to have non-preset time quantum states, wherein the extinction module further comprises an optical attenuator, for performing extinction on the light pulses having non-preset time quantum states, thereby retaining the light pulses having preset time quantum states.

[0027] Further, the modulation module comprises a state of polarization modulation unit, for performing intensity modulation on the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different intensity states; and the extinction module comprises a time phase quantum state modulation unit, for modulating the light pulses in the second light emission sequence having target intensity states to have preset time quantum states, and modulating the light pulses in the second light emission sequence having non-target intensity states to have non-preset time quantum states, wherein the extinction module further comprises an optical attenuator, for performing extinction on the light pulses having non-preset time quantum states, thereby retaining the light pulses having preset time quantum states.

[0028] The embodiment of the present application also provides an optical pulse emitting device for a quantum key distribution system, which comprises the device for generating target evaluation optical pulses according to any one of the embodiments.

[0029] The present application has the advantage that the method, device and equipment for generating target evaluation optical pulses for a quantum key distribution system can not change the normal working state of the light source module during evaluation, extract the light in the specific state required for evaluation through the light extraction modulation device, eliminate other light not required for evaluation, and make the evaluation result better reflect the state parameters (such as wavelength, amplitude, timing, etc.) of the optical pulse signals in each encoding state, so as to obtain the security evaluation result of the quantum key distribution system in the real working state. BRIEF DESCRIPTION OF DRAWINGS

[0030] The technical scheme and other beneficial effects of the present application will be apparent through the following detailed description of the specific embodiments of the present application in combination with the accompanying drawings.

[0031] Figure 1 A table showing an exemplary light emitting encoding mode of a quantum key distribution system based on the BB84 quantum key distribution protocol of the decoy state is shown.

[0032] Figure 2 An exemplary light emitting sequence output by a light source module of a quantum key distribution system and a timing diagram of modulation when extracting the light in the specific state required for evaluation in the prior art are shown.

[0033] Figure 3 A comparison diagram of the light emitting sequence output by the light source module in the normal working phase of the quantum key distribution system and the light emitting sequence output by the light source module in the evaluation phase in the prior art is shown.

[0034] Figure 4 A structural schematic diagram of the device for generating target evaluation optical pulses for a quantum key distribution system provided by the embodiment of the present application is shown.

[0035] Figure 5 A structural schematic diagram of the first specific embodiment of the device for generating target evaluation optical pulses for a quantum key distribution system provided by the present application is shown.

[0036] Figure 6 A structural schematic diagram of the second specific embodiment of the device for generating target evaluation optical pulses for a quantum key distribution system provided by the present application is shown.

[0037] Figure 7 A structural schematic diagram of the third specific embodiment of the device for generating target evaluation optical pulses for a quantum key distribution system provided by the present application is shown.

[0038] Figure 8A flowchart of a method for generating target evaluation light pulses for a quantum key distribution system is shown.

[0039] Figure 9 A timing diagram of a modulation voltage corresponding to a light emission sequence when a light extraction modulator multiplexes a quantum state modulation unit to extract a specific quantum state light pulse as a light pulse required for evaluation is shown.

[0040] Figure 10 A timing diagram of a modulation voltage corresponding to a light emission sequence when a light extraction modulator multiplexes a quantum state modulation unit to extract a specific quantum state light pulse as a light pulse required for evaluation is shown.

[0041] Figure 11 A timing diagram of a modulation voltage corresponding to a light emission sequence when a light extraction modulator multiplexes a quantum state modulation unit to extract a specific quantum state light pulse as a light pulse required for evaluation is shown. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0043] The terms "first", "second", "third", and the like (if any) in the specification and claims of the present application and the drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the objects thus described can be interchanged under appropriate circumstances. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. Some block diagrams shown in the drawings are functional entities, which do not necessarily have to correspond to physically or logically independent entities. These functional entities can be implemented in the form of software, or in one or more hardware circuits or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] To make the objectives, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] Figure 4 A schematic diagram of the structure of an apparatus 100 for generating target evaluation optical pulses for a quantum key distribution system, provided by an embodiment of the present invention, is shown. Figure 4 As shown, the device 100 includes a light source module 10 for emitting light pulses constituting a first emission sequence; a modulation module 20 for modulating the light pulses in the first emission sequence to generate light pulses constituting a second emission sequence, wherein the light pulses in the second emission sequence have different encoding states; an extinction module 40 for extincting the light pulses in the second emission sequence with non-target encoding states and retaining the light pulses with target encoding states according to the evaluation requirements, so as to generate target evaluation light pulses constituting a third emission sequence; and a control module 30 for sending control signals to the light source module 10, the modulation module 20 and the extinction module 40 to drive the light source module 10, the modulation module 20 and the extinction module 40 to work together.

[0047] Specifically, the basic working principle of the device 100 for generating target evaluation light pulses includes: when the device 100 receives an evaluation requirement of evaluation software, the control module 30 outputs a control signal according to the evaluation requirement to drive the light source module 10 to output light pulses constituting a first light-emitting sequence in a random light mode, and the control module 30 drives the modulation module 20 to modulate the light pulses of the first light-emitting sequence in quantum state and / or intensity to generate light pulses constituting a second light-emitting sequence with different quantum states and / or intensity states; then, the control module 30 outputs a control signal according to the evaluation requirement to drive the extinction module 40 to extinguish the light pulses with non-target quantum states and / or intensity states in the second light-emitting sequence and retain the light pulses with target quantum states and / or intensity states to generate target evaluation light pulses constituting a third light-emitting sequence; wherein the control module 30 further sends control signals to the light source module 10, the modulation module 20 and the extinction module 40, which further includes: outputting control signals to the light source module 10, the modulation module 20 and the extinction module 40 according to the evaluation requirement, so that the light source module 10, the modulation module 20 and the extinction module 40 can work cooperatively.

[0048] In the device 100 disclosed in the present application, the extinction module 40 is an extinction modulator 40 that can realize extinction. The extinction modulator 40 can be an electro-optical modulator or other type of modulator (for example, an intensity modulator IM or an intensity modulation module based on a Sagnac interferometer) as shown in Figure 5 which is arranged outside the light source part 50 of the transmission end of the quantum key distribution system, or can be multiplexed with the modulation module 20 inside the light source part 50 of the transmission end as shown in Figure 6 and Figure 7 The extinction modulator 40 adjusts the amplitude, phase, polarization and other characteristics of the light pulses according to the encoding drive, and in particular, the amplitude modulation (i.e., intensity modulation) can realize the extinction and retention operation of the light pulses without affecting the characteristics of the light pulses themselves.

[0049] Figure 5 The structure schematic diagram of the first specific embodiment of the device 100 for generating target evaluation light pulses for a quantum key distribution system provided by the present application is shown. In this embodiment, the device 100 includes a light source part 50 of a transmission end of a quantum key distribution system and an extinction modulator 40 connected thereto. The light source part 50 of the transmission end includes a light source module 10, a modulation module 20 connected to the light source module 10, and a control module 30 connected to the light source module 10 and the modulation module 20, wherein the modulation module 20 includes a decoy state modulation unit 21 and / or a quantum state modulation unit 22.

[0050] In this embodiment, when the device 100 receives the evaluation requirements from the evaluation software, the control module 30 outputs a control signal according to the evaluation requirements to control the light source module 10 to output light pulses constituting the first emission sequence in a random light mode, and outputs them to the modulation module 20 for quantum state and / or intensity modulation. The decoy state modulation unit 21 and / or quantum state modulation unit 22 in the modulation module 20 maintain the random modulation mode unchanged. The light extraction modulator 40 receives the light pulses constituting the second emission sequence output by the modulation module 20 after quantum state and / or intensity modulation, and performs an extinction operation on the light pulses of the second emission sequence according to the control signal output by the control module 30 to generate the target evaluation light pulse constituting the third emission sequence. In this way, more accurate state parameters of the light pulses of the target encoded state can be obtained without changing the normal operating state of the light source module 10, thus meeting the evaluation requirements.

[0051] The light-extracting modulator 40 can also receive evaluation requirements from a control device (not shown in the figure) located outside the quantum key distribution system, or the light-extracting modulator 40 itself can have a control unit that can receive evaluation requirements from the evaluation software and perform extinction operations on the light pulses modulated by quantum states and / or intensity. It should be noted that the light-extracting modulator 40 and related control devices need to maintain clock synchronization with the light source module 10, the modulation module 20, and the control module 30.

[0052] Figure 6 This diagram illustrates a second specific embodiment of the apparatus 100 for generating target evaluation optical pulses in a quantum key distribution system provided by the present invention. In this embodiment, the apparatus 100 is... Figure 5 The transmitter light source section 50 of the quantum key distribution system shown has an optical extraction modulator 40 that is a multiplexed version of the quantum state modulation unit 22 in the modulation module 20. The quantum state modulation unit 22 can be a time-phase quantum state modulation unit or a polarization quantum state modulation unit. Figure 6 As shown, when measuring the state of light of different intensities (deceptive states), the light source module 10 outputs light pulses in a random light mode and keeps the random modulation mode of the deceptive state modulation unit 21 in the modulation module 20 unchanged, and uses the quantum state modulation unit 22 as the light extraction modulator 40 to perform light extraction operation.

[0053] Figure 7 This diagram illustrates a third specific embodiment of the apparatus 100 for generating target evaluation optical pulses for a quantum key distribution system provided by the present invention. In this embodiment, the apparatus 100 is... Figure 5 The transmitter light source section 50 of the quantum key distribution system shown includes an optical extraction modulator 40, which is a multiplexed version of the decoy state modulation unit 21 in the modulation module 20. (As shown...) Figure 7As shown, when measuring different phase or polarization quantum states (such as...) Figure 1 When the light is in the state of H-polarized light, the light source module 10 outputs in random light mode, while keeping the random modulation mode of the quantum state modulation unit 22 in the modulation module 20 unchanged, and using the decoy state modulation unit 21 as the light extraction modulator 40 to perform light extraction operation.

[0054] like Figure 6 and Figure 7 The device 100 shown (i.e., the transmitter light source section 50) can obtain more accurate state parameters of the light pulse of the target encoded state without changing the normal working state of the light source module 10, thus meeting the evaluation requirements. At the same time, it does not require setting up an additional active light-extracting modulator. It can simply reuse the existing active modulation module in the system. For example, for polarization quantum state modulation, an additional passive polarization filter device can be added; for time phase quantum state modulation, an attenuator on the interferometer arm corresponding to the unpreset time state can be added to achieve light extraction.

[0055] Figure 8 A schematic flowchart of a target evaluation light pulse generation method provided by an embodiment of the present invention is shown. The method includes the following steps: S10, generating light pulses constituting a first emission sequence; S11, modulating the light pulses constituting the first emission sequence to generate light pulses constituting a second emission sequence, wherein the light pulses in the second emission sequence have different encoding states; and S12, according to evaluation requirements, extinguishing the light pulses in the second emission sequence that have non-target encoding states and retaining the light pulses that have target encoding states to generate target evaluation light pulses constituting a third emission sequence.

[0056] Specifically, while referring to Figures 4 to 8 In step S10, the control module 30 outputs a driving signal according to the emission state instruction of the evaluation software to control the light source module 10 to output light pulses constituting the first emission sequence, which is consistent with the normal working state of the quantum key distribution system (e.g., random light mode). The light source module 10 does not change the state parameters of the output light pulses (such as timing, wavelength, amplitude, etc.).

[0057] In step S11, the control module 30 outputs a signal to the modulation module 20 according to the received evaluation requirements, so that the modulation module 20 performs at least one of quantum state modulation and intensity modulation on the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the quantum state modulation includes polarization quantum state modulation, time phase quantum state modulation or phase quantum state modulation on the light pulses in the first light emission sequence.

[0058] In step S12, the control module 30 outputs a signal to the light extraction modulator 40 according to the received evaluation requirement signal, and the light extraction modulator 40 extracts the light pulses with non-target quantum states in the second light sequence and retains the light pulses with target quantum states to generate the target evaluation light pulses constituting the third light sequence.

[0059] In further embodiments, when the light extraction modulator 40 is an external electro-optical modulator or other type of modulator of the quantum key distribution system as shown in Figure 5 In further embodiments, when the light extraction modulator 40 is an external electro-optical modulator or other type of modulator of the quantum key distribution system as shown in

[0060] In further embodiments, when the light extraction modulator 40 is an external electro-optical modulator or other type of modulator of the quantum key distribution system as shown in

[0061] It should be understood that the number of random different signals outputted by the control module 30 matches the number of quantum states, the number of decoy states, and the number of the above-mentioned 4 or 3 is only an example and not a limitation. In addition, the control module 30 can also control the quantum state modulation unit 22 and the decoy state modulation unit 21 to work in a non-random modulation mode (i.e., the voltage of the driving voltage sequence needs to be changed, etc.) to output light pulses of specific states. Specifically, the control module 30 outputs specific signals (for example, outputs extinction modulation signals corresponding to the modulation signals) to the decoy state modulation unit 21 or the quantum state modulation unit 22 of the modulation module 20 according to the evaluation requirement, so that the decoy state modulation unit 21 or the quantum state modulation unit 22 generates a specific pulse voltage that acts on the light pulse sequence to generate signals with specific quantum states or intensity states.

[0062] In further embodiments, when the extinction modulator 40 is a multiplexing of the modulation module 20 inside the quantum key distribution system as shown in Figure 6 or Figure 7 , that is, the quantum state modulation unit 22 is a time-phase quantum state modulation unit or a polarization quantum state modulation unit, steps S11 and S12 further comprise:

[0063] When the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target quantum state, the quantum state modulation is performed on the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different quantum states; and the intensity modulation is performed on the light pulses with the target quantum state in the second light emission sequence to have a preset intensity state, and the light pulses with a non-target quantum state in the second light emission sequence are modulated to have a non-pre-set intensity state, wherein the non-pre-set intensity state is an extinction state.

[0064] When the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target intensity state, the intensity modulation is performed on the light pulses in the first light emission sequence to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different intensity states; the polarization quantum state modulation is performed on the light pulses with the target intensity state in the second light emission sequence to have a preset polarization quantum state, and the light pulses with a non-target intensity state in the second light emission sequence are modulated to have a non-pre-set polarization quantum state; and the polarization filter is used to retain the light pulses with the preset polarization quantum state and to perform extinction on the light pulses with the non-pre-set polarization quantum state.

[0065] When the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target intensity state, the light pulses in the first light emission sequence are intensity-modulated to generate the second light emission sequence, wherein the light pulses in the second light emission sequence have different intensity states; the light pulses with the target intensity state in the second light emission sequence are modulated into a preset time quantum state by the time phase quantum state modulation, and the light pulses with a non-target intensity state in the second light emission sequence are modulated into a non-pre-set time quantum state; and the light pulses with the non-pre-set time quantum state are extinguished by the optical attenuator, so as to retain the light pulses with the preset time quantum state.

[0066] The following will be described in combination with Figures 9 to 11 The process of extracting different quantum states or decoy state light pulses as the light pulses required for evaluation will be described in detail below.

[0067] Figure 9 The timing diagram of the modulation voltage corresponding to the light emission sequence when the decoy state modulation unit of the extraction light modulator multiplexing is used to extract H polarization state light pulses as the light pulses required for evaluation is shown.

[0068] Meanwhile, reference is made to Figure 7 and Figure 9 When the light pulses required for evaluation are specific quantum state light pulses, such as H polarization state light pulses of a polarization system, first, the light source module 10 is kept to output a light pulse sequence in a random light mode, and the random modulation state of the quantum state modulation unit 22 in the modulation module 20 is unchanged, i.e., four different random signals are output by the control module 30 to the quantum state modulation unit 22, so that the quantum state modulation unit 22 generates four different random pulse voltages, i.e., V0, V π , V π / 2 , V 3π / 2 , which act on the light pulse sequence output by the light source module 10, respectively, to generate a light pulse sequence with four different polarization quantum state signals, wherein the voltages corresponding to the H, V, P, and N polarization states are V0, V π , V π / 2 , and V 3π / 2 , respectively. Next, the H polarization state light pulses modulated by the quantum state modulation unit 22 are modulated into a light-retaining state with light when the decoy state modulation unit 21 performs decoy state modulation (i.e., intensity modulation); and the light pulses of other polarization states except the H polarization state light pulses are modulated into an extinction state with minimum light intensity when the decoy state modulation unit 21 performs decoy state modulation. Thus, the specific H polarization state light pulses can be retained, and the other polarization state light pulses can be eliminated.

[0069] According to the modulation of the quantum state modulation unit 22 (i.e. the pulse voltage sequence, etc.), the control module 30 generates a corresponding extinction modulation signal and outputs it to the decoy state modulation unit 21 to generate two kinds of decoy state modulation voltages, which act on the H polarization state light pulses and the non-H polarization state light pulses in the light pulse sequence modulated by the quantum state modulation unit 22, respectively, to generate a light emission sequence with two light pulse intensities, which are set to "light" and "extinction" intensity states, respectively. Note that the specific intensities of "light" and "extinction" are not limited here. Preferably, the light intensity of the "light" state is close to the maximum light intensity, and the "extinction" state is close to zero light intensity.

[0070] It should be understood that similarly, if the extinction modulator 40 multiplexes the decoy state modulation unit 21 to extract the phase state light pulse as the light pulse required for evaluation, the quantum state modulation unit 22 needs to generate four different random pulse voltages to act on the light pulse sequence output by the light source module 10, to generate a light pulse sequence with four different phases of quantum state signals. The phase state light pulse required for evaluation modulated by the quantum state modulation unit 22 is modulated to have a light reserved state when the decoy state modulation unit 21 performs decoy state modulation (i.e. intensity modulation); and the other phase state light pulses except the quantum state light pulse required for evaluation are modulated to have an extinction state with minimum light intensity when the decoy state modulation unit 21 performs decoy state modulation. The specific modulation method is similar to that of extracting the H polarization state light pulse as the light pulse required for evaluation, which will not be described here.

[0071] Figure 10 The timing diagram of the modulation voltage corresponding to the light emission sequence when the extinction modulator multiplexes the quantum state modulation unit to extract the D decoy state light pulse as the light pulse required for evaluation is shown, wherein the quantum state modulation unit is a time phase quantum state modulation unit.

[0072] Meanwhile, referring to Figure 6 and Figure 10 When the light pulse required for evaluation is a specific intensity (decoy state) light pulse, such as a D decoy state light pulse, first, the light source module 10 is kept to output a light pulse sequence in a random light mode, and the random modulation state of the decoy state modulation unit 21 in the modulation module 20 is unchanged, i.e. three different random signals are output by the control module 30 to the decoy state modulation unit 21, so that the decoy state modulation unit 21 generates three different random pulse voltages, which act on the light pulse sequence output by the light source module 10, to generate a signal (decoy state signal) with three different intensities, i.e. signal state, decoy state and vacuum state, in which Figure 10S, D and V, respectively. Next, the D decoy state light pulse modulated by the decoy state modulation unit 21 is modulated into a first time state (indicated as "reserved") when it passes through the time-phase quantum state modulation unit 22; while other light pulses except the D decoy state light pulse are modulated into other time states (indicated as "extinction") except the first time state.

[0073] Specifically, as shown in FIG. 2, the D decoy state light pulse modulated by the decoy state modulation unit 21 is modulated into a T0 time state when it passes through the time-phase quantum state modulation unit 22; while other light pulses except the D decoy state light pulse are modulated into another T1 time state. Subsequently, the extinction of the T1 time state is realized by increasing the attenuation value of the adjustable optical attenuator (VOA) on the corresponding path of the unequal arm interferometer inside the time-phase quantum state modulation unit 22. Figure 10

[0074] Among them, similar to the above multiplex decoy state modulation unit 21, according to the modulation condition (i.e. pulse voltage sequence, etc.) of the decoy state modulation unit 21, the control module 30 generates the corresponding extinction modulation signal and outputs it to the time-phase quantum state modulation unit 22 to generate two kinds of time-phase quantum state modulation voltages, which respectively act on the D decoy state light pulse and the non-D decoy state light pulse in the light pulse sequence modulated by the decoy state modulation unit 21, to correspondingly generate the light emission sequence of light pulses with T0 time state and T1 time state.

[0075] Figure 11 FIG. 6 shows the timing diagram of the modulation voltage of the extinction modulator multiplex quantum state modulation unit according to another embodiment of the present application for extracting the D decoy state light pulse as the light pulse required for evaluation, wherein the quantum state modulation unit is a polarization quantum state modulation unit.

[0076] Meanwhile, referring to FIGS. 1, 2, 3, 4, 5 and 6, Figure 6 and Figure 11 When the light pulse required for evaluation is a light pulse with a specific intensity (decoy state), such as a D decoy state light pulse, first, the light source module 10 is kept to output the light pulse sequence in a random light mode, and the random modulation state of the decoy state modulation unit 21 in the modulation module 20 is unchanged, i.e. the control module 30 outputs three different random signals to the decoy state modulation unit 21, so that the decoy state modulation unit 21 generates three different random pulse voltages, which respectively act on the light pulse sequence output by the light source module 10, to generate signals (decoy state signals) with three different intensities, i.e. signal state, decoy state and vacuum state, in which Figure 11 ​S, D and V, respectively. Next, the D decoy state light pulse modulated by the decoy state modulation unit 21 is modulated into a first polarization state (indicated as "reserved") when passing through the polarization quantum state modulation unit 22; while other light pulses except the D decoy state light pulse are modulated into other polarization states (indicated as "extinguished") except the first polarization state.

[0077] Specifically, the D decoy state light pulse modulated by the decoy state modulation unit 21 is modulated into an H polarization state when passing through the polarization quantum state modulation unit 22; while other light pulses except the D decoy state light pulse are modulated into other polarization states (e.g., V polarization state) different from the H polarization state. Subsequently, the other polarization states are extinguished by a passive polarization filter device. For example, the polarization filter device is a polarization beam splitter (PBS) which is set to allow the H polarization state to pass through and be reserved, while other polarization states (e.g., V polarization state) are not allowed to pass through and are extinguished.

[0078] It should be understood that when the polarization quantum state modulation unit 22 modulates the quantum state, a polarization state other than the H polarization state can be modulated as the "reserved" polarization state, and the polarization filter device (e.g., PBS) in the subsequent optical path needs to be adjusted to match the "reserved" polarization state and to extinguish other polarization states other than the "reserved" polarization state. Meanwhile, the selection of the "reserved" polarization state does not affect the security evaluation result.

[0079] In the above method, similar to the multiplex decoy state modulation unit 21, according to the modulation condition (i.e., pulse voltage sequence, etc.) of the decoy state modulation unit 21, the control module 30 generates a corresponding extinction modulation signal and outputs it to the polarization quantum state modulation unit 22 to generate two polarization quantum state modulation voltages (e.g., corresponding to H polarization state and V polarization state, respectively), which act on the D decoy state light pulse and the non-D decoy state light pulse in the light pulse sequence modulated by the decoy state modulation unit 21 to correspondingly generate a light emission sequence with H polarization state and V polarization state.

[0080] It should be understood that in the above method, the "extinguished" in the "reserved" and "extinguished" in the above method means that the light pulse does not exist, and the "reserved" means that the light pulse is output; and the quantum state or decoy state indicated by the dashed box means that the light pulse of the quantum state or decoy state will be extinguished in the subsequent steps. Figures 9 to 11 The above method of extracting light is not limited to extracting a certain state alone, and can measure the measured light state according to any combination of encoding, which can prove the authenticity and reliability of the measurement result.

[0081]

[0082] ​The method of generating a certain state of light can also be used in the quantum key distribution system calibration feedback stage, such as the polarization feedback stage, only to send out a certain state of light.

[0083] It should be noted that although the light extraction modulator is a modulation module of the multiplexed quantum key distribution system itself, the random control signal and the corresponding modulation voltage acting on the modulation module may be different from those in the normal working stage of the quantum key distribution system, and appropriate values need to be configured so that a high extinction ratio is achieved for states other than the specific state. For example, in normal operation, the decoy state modulation unit modulates the three different intensities of signal state, decoy state, and vacuum state according to a ratio of 6:1:1, while in the intensity modulation of the multiplexed decoy state modulation unit, the measured target quantum state and other quantum states are light and extinction states, respectively. For the case of balanced distribution of quantum states, the vacuum ratio is 3 / 4, which is different from the ratio in the normal operation described above. At the same time, multiplexing the existing quantum state modulation unit and decoy state modulation unit of the system can reduce the complexity of the system and the complexity of the evaluation.

[0084] Specifically, if quantum state light pulses need to be measured, the decoy state modulation unit is multiplexed so that the light pulses of other states except the measured quantum state are extinguished. If decoy state light pulses need to be measured, the quantum state modulation unit is multiplexed so that the light pulses of other states except the measured decoy state are extinguished. For a time-phase encoding system, when the time-phase quantum state modulation unit is multiplexed, a certain time state is first modulated, and then the time state inside the time-phase quantum state modulation unit is attenuated through a VOA on the path in the interferometer to achieve extinction. For a polarization encoding system, when the polarization quantum state modulation unit is multiplexed, a certain polarization state is first modulated, and then an additional passive polarization filter device is used to retain the polarization state, and the remaining polarization states are not transparent and are extinguished.

[0085] In another embodiment, an optical pulse emitting device for a quantum key distribution system is provided, which includes the above-mentioned device for generating target evaluation optical pulses.

[0086] As can be seen from the above, since the light emission sequence of the light source in the existing technology evaluation stage and the true random (including periodic) light emission sequence in the system normal working stage can be different, the true working state cannot be represented, the measurement results of the state parameters (for example, wavelength, amplitude, timing, etc.) of the light pulses of each encoding state cannot accurately reflect the true working state of the measured object, and thus the security of the quantum key distribution system can be easily misjudged. In contrast, the method, device and emitting equipment for generating the evaluation light pulse proposed in the application, in the evaluation, the light emitted by the light source module of the quantum key distribution system is always consistent with the state in the normal working state of the system; at the same time, the non-evaluation-required light is removed by the light extraction modulator, and the specific state-required light is reserved, so as to generate the specific state-required light. The light extraction modulator has little additional influence on the measured parameters (such as timing, wavelength, amplitude, etc.) of the measured object (for example, the light pulses of each encoding state), and thus the evaluation results can accurately reflect the measured object and obtain the security evaluation results in the true working state.

[0087] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware, and the computer program can be stored in a non-volatile computer readable storage medium. When the computer program is executed, the processes of the above-mentioned embodiments can be included. Any reference to memory, storage, database or other medium used in the embodiments provided in the present application can include non-volatile and / or volatile memory. The non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. The volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM) and memory bus dynamic RAM (RDRAM) and the like.

[0088] The above describes in detail the method, device and equipment for generating target evaluation light pulses of a quantum key distribution system provided by the embodiments of the present application. The principles and implementation manners of the present application are described by using specific examples. The above description of the embodiments is only used to help understand the technical solutions of the present application and the core ideas thereof. Those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for generating target evaluation optical pulses for use in a quantum key distribution system, characterized in that, include: Generates light pulses that constitute the first emission sequence; The light pulses constituting the first emission sequence are modulated to generate light pulses constituting the second emission sequence, wherein the light pulses in the second emission sequence have different encoding states; as well as According to the evaluation requirements, the light pulses with non-target encoded states in the second emission sequence are extinguished, while the light pulses with target encoded states are retained, in order to generate the target evaluation light pulses that constitute the third emission sequence.

2. The method for generating target evaluation light pulses as described in claim 1, characterized in that, The encoded state includes at least one of a quantum state and a strength state.

3. The method for generating target evaluation light pulses as described in claim 1, characterized in that, The method further includes performing at least one of quantum state modulation and intensity modulation on the light pulses in the first emission sequence to generate the second emission sequence, wherein the quantum state modulation includes polarization quantum state modulation, time phase quantum state modulation, or phase quantum state modulation on the light pulses in the first emission sequence.

4. The method for generating target evaluation light pulses as described in claim 3, characterized in that, The method further includes: The light pulses in the first emission sequence are subjected to quantum state modulation and / or intensity modulation to generate the second emission sequence, wherein the light pulses in the second emission sequence have different quantum states and / or intensity states; and According to the evaluation requirements, the light pulses in the second emission sequence that have non-target quantum states and / or intensity states are extinguished, while the light pulses that have target quantum states and / or intensity states are retained, in order to generate the target evaluation light pulse.

5. The method for generating target evaluation light pulses as described in claim 3, characterized in that, The method further includes: When the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target quantum state, the light pulses in the first emission sequence are quantum-state modulated to generate the second emission sequence, wherein the light pulses in the second emission sequence have different quantum states; and The intensity modulation modulates the light pulses in the second emission sequence that have the target quantum state into a preset intensity state, and modulates the light pulses in the second emission sequence that have the non-target quantum state into a non-preset intensity state, wherein the non-preset intensity state is an extinction state.

6. The method for generating target evaluation light pulses as described in claim 3, characterized in that, The method further includes: When the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target intensity state, the light pulses in the first emission sequence are intensity modulated to generate the second emission sequence, wherein the light pulses in the second emission sequence have different intensity states; The light pulses in the second emission sequence with a target intensity state are modulated into a preset time quantum state by the time-phase quantum state modulation, and the light pulses in the second emission sequence with a non-target intensity state are modulated into a non-preset time quantum state; and The light pulse with a non-preset time quantum state is extinct by an optical attenuator, thereby preserving the light pulse with a preset time quantum state.

7. The method for generating target evaluation light pulses as described in claim 3, characterized in that, The method further includes: When the evaluation requirement indicates that the target evaluation light pulse is a light pulse with a target intensity state, the light pulses in the first emission sequence are intensity modulated to generate the second emission sequence, wherein the light pulses in the second emission sequence have different intensity states; The light pulses in the second emission sequence with a target intensity state are modulated into a preset polarization quantum state by the polarization quantum state modulation, and the light pulses in the second emission sequence with a non-target intensity state are modulated into a non-preset polarization quantum state; and The light pulses with preset polarization quantum states are retained by a polarization filter, and the light pulses with non-preset polarization quantum states are extinct.

8. An apparatus for generating target evaluation optical pulses for use in a quantum key distribution system, characterized in that, include: The light source module is used to emit light pulses that constitute the first light emission sequence; A modulation module is used to modulate the light pulses in the first emission sequence to generate light pulses constituting a second emission sequence, wherein the light pulses in the second emission sequence have different encoding states; as well as The extinction module is used to extinct the light pulses with non-target encoded states in the second emission sequence and retain the light pulses with target encoded states according to the evaluation requirements, so as to generate the target evaluation light pulses that constitute the third emission sequence. as well as The control module is used to send control signals to the light source module, the modulation module and the extinction module to drive the light source module, the modulation module and the extinction module to work together.

9. The apparatus for generating target evaluation light pulses as described in claim 8, characterized in that, The encoded state includes at least one of a quantum state and a strength state.

10. The apparatus for generating target evaluation light pulses as described in claim 8, characterized in that, The modulation module includes a quantum state modulation unit and / or a decoy state modulation unit, respectively used to perform quantum state modulation and / or intensity modulation on the light pulses in the first emission sequence to generate the second emission sequence, wherein the light pulses in the second emission sequence have different quantum states and / or intensity states; and The extinction module is a light-extracting modulator used to extinct light pulses with non-target quantum states and / or intensity states in the second emission sequence and retain light pulses with target quantum states and / or intensity states according to the evaluation requirements, so as to generate the target evaluation light pulse.

11. The apparatus for generating target evaluation light pulses as described in claim 8, characterized in that, The modulation module includes a quantum state modulation unit for quantum state modulation of the light pulses in the first emission sequence to generate the second emission sequence, wherein the light pulses in the second emission sequence have different quantum states; as well as The extinction module includes a decoy state modulation unit, which modulates the light pulses with target quantum states in the second emission sequence into a preset intensity state, and modulates the light pulses with non-target quantum states in the second emission sequence into a non-preset intensity state, wherein the non-preset intensity state is an extinction state.

12. The apparatus for generating target evaluation light pulses as described in claim 8, characterized in that, The modulation module includes a decoy state modulation unit for intensity modulation of light pulses in the first emission sequence to generate a second emission sequence, wherein the light pulses in the second emission sequence have different intensity states; and The extinction module includes a time-phase quantum state modulation unit, which modulates the light pulses in the second emission sequence with a target intensity state into a preset time quantum state, and modulates the light pulses in the second emission sequence with a non-target intensity state into a non-preset time quantum state. The extinction module also includes a light attenuator, which is used to extinct the light pulses with the non-preset time quantum state, thereby retaining the light pulses with the preset time quantum state.

13. The apparatus for generating target evaluation light pulses as described in claim 8, characterized in that, The modulation module includes a decoy state modulation unit for intensity modulation of light pulses in the first emission sequence to generate a second emission sequence, wherein the light pulses in the second emission sequence have different intensity states; and The extinction module includes a polarization quantum state modulation unit, used to modulate light pulses with a target intensity state in the second emission sequence into light pulses with a preset polarization quantum state, and to modulate light pulses with a non-target intensity state in the second emission sequence into light pulses with a non-preset polarization quantum state. The extinction module also includes a polarization filter, used to retain the light pulses with the preset polarization quantum state and to extinct the light pulses with the non-preset polarization quantum state.

14. An optical pulse emitting device for a quantum key distribution system, characterized in that, The device includes the apparatus for generating target evaluation light pulses as described in any one of claims 8 to 13.

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