Quantum key sending end quantum state modulation method and device

Abstract

The invention relates to the technical field of quantum communication, and provides a quantum key sending end quantum state modulation method and device, and the method comprises the steps: obtaining pulse light which is periodic light generated through a coding laser; a first path of light and a second path of light are formed through the pulsed light, a first digital signal is generated based on the second path of light, the first digital signal is used for generating a random number, a first driving signal is generated based on the first digital signal, quantum state modulation is carried out on the first path of light based on the first driving signal, and quantum state modulation is carried out on the second path of light; the quantum state modulation signal is a signal distributed by a quantum key. The coding laser is used as a seed source to generate the random number, random data based on physical noise is replaced, quantum state modulation is carried out on the pulse light source through the random number, unpredictable characteristics are achieved, and safety can be improved.

Description

Technical Field

[0001] The present application relates to the field of quantum communication technology, and in particular to a quantum state modulation method and device for a quantum key transmitter. Background Art

[0002] Quantum secure communication technology is a communication technology based on the principles of quantum mechanics. It is used to protect the security of information transmission and ensure the security of information transmission by using the non-cloning of quantum states and the characteristics of quantum entanglement. Based on quantum key distribution (QKD) technology and the principle of one-time-pad cryptography, quantum secure communication can achieve secure transmission of information in public channels, securely share keys between users, and detect potential eavesdropping.

[0003] The quantum secure communication system is divided into a sending device and a receiving device. The sending device is used for modulation and transmission of quantum states, and the receiving device is used for demodulation and detection of quantum states. The sending device and the receiving device form a set of symmetric quantum keys through the quantum communication protocol.

[0004] The transmitting device needs a random number source when modulating the quantum state. Random number sources include pseudo-random number sources and true random number sources. For true random number sources, a random number generation method based on physical noise is adopted. However, a random number source based on physical noise is predictable under the condition that all physical conditions are known, resulting in low security. Summary of the invention

[0005] The present application provides a quantum state modulation method and device for a quantum key transmitter to solve the problem of low security.

[0006] In a first aspect, the present application provides a quantum state modulation method for a quantum key transmitter, comprising: Acquire pulsed light, wherein the pulsed light is periodic light generated by a coded laser; The pulsed light is used to form a first light path and a second light path; Generate a first digital signal based on the second light, where the first digital signal is used to generate a random number; generating a first driving signal based on the first digital signal; Based on the first driving signal, quantum state modulation is performed on the first light to generate a quantum state modulation signal, where the quantum state modulation signal is a signal for quantum key distribution.

[0007] Random numbers are generated by using a coded laser as a seed source to replace random data based on physical noise. In addition, quantum state modulation of the pulsed light source is achieved through random numbers, which has unpredictable characteristics and can improve security.

[0008] In some feasible embodiments, obtaining pulsed light includes: Acquire a second driving signal; When the second driving signal is at a low level, the pulse light outputs a periodic light, the initial phase of the periodic light is an undetermined value, and the pulses are emitted in a periodic manner; When the second driving signal is at a high level, the pulse light outputs random noise light, and the phase of the random noise light is a random phase.

[0009] In some feasible embodiments, forming the first light path and the second light path by the pulsed light includes: injecting the pulsed light onto a beam splitter; Acquire the type of the beam splitter, which is a symmetric beam splitter or an asymmetric beam splitter; Based on the type, the pulse light is divided into a first light path and a second light path by the beam splitter, wherein the first light path is light propagating along a reflection path, and the second light path is light propagating along a transmission path.

[0010] In some feasible embodiments, the generating a first digital signal based on the second light includes: Passing the second light through an unequal-arm interferometer to output a long-arm signal and a short-arm signal; The long arm signal and the short arm signal are combined and interfered at an output point to form an interference signal, wherein the amplitude of the interference signal is a random optical signal; Converting the interference signal into an electrical signal, wherein the electrical signal is an analog signal, and the amplitude of the electrical signal is proportional to the amplitude of the interference signal; converting the analog signal into a second digital signal; A first digital signal is generated by using the second digital signal.

[0011] In some feasible embodiments, generating a first driving signal based on the first digital signal includes: Generate a first control signal according to the first digital signal, wherein the first control signal is a control signal having a coding protocol; Based on the coding protocol, output a second driving signal according to the first control signal; A first driving signal is generated according to the second driving signal, wherein the first driving signal is a driving signal with multiple amplitudes.

[0012] In some feasible embodiments, based on the first driving signal, quantum state modulating the first light to generate a quantum state modulated signal includes: Applying the first driving signal to a modulator in an interferometer; The first light is quantum-modulated by the modulator to generate a quantum-modulated signal.

[0013] In some feasible embodiments, the performing quantum state modulation on the first light by the modulator to generate a quantum state modulation signal includes: modulating the quantum state of the first light according to the first driving signal to generate a modulated light signal; interfering the modulated optical signal with the first light to generate an interfered optical signal; The interfered optical signal is detected to extract the quantum state signal.

[0014] In a second aspect, the present application provides a quantum key sending end quantum state modulation device, comprising: A first controller is used to obtain pulse light, where the pulse light is periodic light generated by a coded laser; A beam splitter, used for forming the pulsed light into a first light path and a second light path; A random number generation module, used to generate a first digital signal based on the second light, wherein the first digital signal is used to generate a random number; A drive control module, configured to generate a first drive signal based on the first digital signal; A quantum state modulation module is used to perform quantum state modulation on the first light based on the first driving signal to generate a quantum state modulation signal, where the quantum state modulation signal is a signal for quantum key distribution.

[0015] In some feasible embodiments, the random number generation module includes: An unequal-arm interferometer, used for outputting a long-arm signal and a short-arm signal, and combining the long-arm signal and the short-arm signal, and interfering at an output point to form an interference signal, wherein the amplitude of the interference signal is a random optical signal; A detector, used to convert the interference signal into an electrical signal, wherein the electrical signal is an analog signal, and the amplitude of the electrical signal is proportional to the amplitude of the interference signal; A sampler, converting the analog signal into a second digital signal; A post-processing unit is used to generate a first digital signal through the second digital signal.

[0016] In some feasible embodiments, the drive control module includes: A coding controller, configured to generate a first control signal according to the first digital signal, wherein the first control signal is a control signal having a coding protocol; A second controller, configured to output a second driving signal according to the first control signal based on a coding protocol; The driving unit is used to generate a first driving signal according to a second driving signal, wherein the first driving signal is a multi-amplitude driving signal, and the driving unit includes a digital-to-analog converter and a radio frequency module.

[0017] It can be seen from the above technical solutions that the present application provides a quantum state modulation method and device for a quantum key transmitter, the method comprising: obtaining pulsed light, the pulsed light being periodic light generated by a coding laser; forming a first light path and a second light path through the pulsed light, generating a first digital signal based on the second light path, the first digital signal being used to generate a random number, generating a first drive signal based on the first digital signal, and performing quantum state modulation on the first light path based on the first drive signal to generate a quantum state modulation signal, the quantum state modulation signal being a signal for quantum key distribution. Random numbers are generated by using a coding laser as a seed source to replace random data based on physical noise, and quantum state modulation of a pulsed light source is achieved by using random numbers, which has unpredictable characteristics and can improve security. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 A schematic diagram of a flow chart of a quantum key transmitter quantum state modulation method provided in an embodiment of the present application; Figure 2 A schematic diagram of the relationship between the driving signal and the pulse light output provided in the embodiment of the present application; Figure 3 A schematic diagram of a process for generating an interference signal provided in an embodiment of the present application; Figure 4 A waveform diagram of a first driving signal provided in an embodiment of the present application; Figure 5 A timing relationship diagram of the first driving signal and the first light provided in an embodiment of the present application; Figure 6 This is a structural diagram of the quantum state modulation device at the quantum key sending end provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The following embodiments are described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following embodiments do not represent all embodiments consistent with the present application.

[0021] In quantum secure communication systems, the true random number source is directly related to the security of the generated quantum key. The reason for using a true random number source is to ensure that the generated key is truly unpredictable, thereby providing the highest security guarantee.

[0022] Pseudo-random number generators (PRNGs) rely on an initial value (seed) and generate sequences through a deterministic algorithm. If an attacker can learn the seed and algorithm, the subsequent random number sequence can be completely predicted. Therefore, pseudo-random number sources are not suitable for situations where security requirements are extremely high.

[0023] True random number generators (TRNGs) generate random numbers by exploiting the uncertainty in physical processes that are usually unpredictable, such as thermal noise, photoelectric effect, etc. Since these processes are random in nature, the generated random number sequences are also unpredictable.

[0024] In quantum communication systems, the source of true random numbers is based on physical noise. For example, random numbers can be generated using thermal noise of electronic components, quantum fluctuations of photons, etc. The randomness of these physical processes comes from the inherent uncertainty of quantum mechanics and cannot be predicted in theory.

[0025] Although physical noise itself is random, if the physical environment of the system changes (e.g., temperature, electromagnetic interference, etc.), it may affect the characteristics of the noise and thus the quality of the random numbers. In theory, if all physical conditions are known, the random number generation process based on physical noise is predictable, resulting in low security.

[0026] To solve the problem of low security, such as Figure 1 As shown, some embodiments of the present application provide a quantum state modulation method for a quantum key transmitter, including: S100: Obtain pulse light.

[0027] Pulsed light is generated by a coded laser. A laser encoder is a device used to generate and modulate optical signals. The laser encoder modulates the optical signal by converting the electrical signal into an optical signal, thereby generating optical pulses with specific coding. The laser encoder includes: a laser, a modulator, a drive circuit, and a control unit. The laser is used to generate a continuous or pulsed laser signal. The modulator modulates the laser signal according to the input electrical signal. The drive circuit generates and controls the electrical signal of the modulator. The control unit manages the operation of the entire system, including signal generation, modulation, and output control.

[0028] In this embodiment, the pulse light is driven by the first controller, and the pulse light is periodic light, but random noise light can also be output; Figure 2As shown, in some embodiments, periodic light or random noise light is obtained by the level of the second driving signal. Specifically, the second driving signal is obtained. When the second driving signal is at a low level, the pulse light outputs periodic light, the initial phase of the periodic light is an undetermined value, and the pulses are emitted periodically; when the second driving signal is at a high level, the pulse light outputs random noise light, and the phase of the random noise light is a random phase.

[0029] For periodic light and noise light, the pulse light in this embodiment is periodic light, which is used for quantum state modulation, and random number generation is achieved through the background noise of the periodic light (i.e., random noise light). By making full use of the periodic pulse and background noise of a periodic light, the hardware cost can be reduced.

[0030] The second driving signal is a driving signal output by the first controller. The first controller is connected to the pulse light source through a digital circuit or an analog circuit. The controller is responsible for generating a trigger signal to control the switching and modulation of the pulse light source.

[0031] The controller generates a periodic low-level signal to trigger the pulse light source to emit light pulses at fixed time intervals. The pulse light source outputs stable light pulses under the triggering of the low-level signal to ensure that the light intensity does not fluctuate significantly. The pulse light outputs periodic light with uncertain initial phase. The light pulses of periodic light with uncertain initial phase are emitted at a fixed period. The phase of each emitted light pulse is random or unpredictable, and the amplitude of the light pulse is relatively stable without significant fluctuations.

[0032] When the controller generates a high-level signal, it adjusts the laser's drive current or voltage to reduce the laser's output power to a lower level. At low levels, the laser's output power will be affected by various noise sources, such as temperature fluctuations, current fluctuations, etc., resulting in fluctuations in light intensity. At low levels, the laser's phase will also be affected by noise and become random.

[0033] S200: forming a first light path and a second light path by using pulse light.

[0034] Because it is necessary to use the periodic light and background noise of the pulse light separately, in this embodiment, the pulse light is divided into two paths of light by a beam splitter, namely the first path of light and the second path of light. In the process of preparing the quantum state, including the preparation of the single-photon state, the single-photon state can be used for quantum key distribution, quantum computing, quantum communication, quantum measurement and quantum storage, etc. The preparation of the single-photon state will make the final output light reach the single-photon state, so the amplitudes of the first path of light and the second path of light can be the same or different.

[0035] The amplitude can be determined by the splitting ratio of the beam splitter, wherein a beam splitter with a splitting ratio of 1:1 is a symmetrical beam splitter, and beam splitters with other splitting ratios are asymmetrical beam splitters. For example, the beam splitting ratio may be 2:8, 3:7, and the like.

[0036] The splitting ratio of a symmetrical beam splitter is 1:1, that is, the reflectivity and transmittance are 50% each, 50% of the light is reflected, 50% of the light is transmitted, and the intensity of the two output lights is equal. The splitting ratio of an asymmetrical beam splitter is not 1:1. For example, 2:8 is used. The reflectivity and transmittance are not equal. For example, 20% of the light is reflected, 80% of the light is transmitted, and the intensity of the two output lights is different.

[0037] In some embodiments, pulsed light is incident on a beam splitter, and then the type of the beam splitter is obtained. Based on the type of the beam splitter, the pulsed light is split into a first light path and a second light path by the beam splitter, wherein the type of the beam splitter is a symmetric beam splitter or an asymmetric beam splitter, the first light path is light propagating along a reflection path, and the second light path is light propagating along a transmission path. The first light path is used to modulate a quantum state, and the second light path is used to generate a random number.

[0038] Taking the beam splitter as a symmetrical beam splitter as an example, pulse light propagates along a certain direction and is incident on the beam splitter, 50% of the light is reflected and 50% of the light is transmitted, and reflected light is obtained, that is, the light propagating along the reflection path, and transmitted light is obtained, that is, the light propagating along the transmission path.

[0039] S300: Generate a first digital signal based on the second light.

[0040] The second light path is used to generate random numbers, including the following steps: S310: The second light path passes through an unequal-arm interferometer to output a long-arm signal and a short-arm signal.

[0041] The unequal-arm interferometer is used to generate interference signals. Through the unequal-arm interferometer, the input optical signal can be divided into two paths, which are recombined after passing through paths of different lengths to form an interference signal. Exemplarily, the second optical signal is divided into two optical signals, one optical signal propagates along the reflection path and enters the long arm, and the other optical signal propagates along the transmission path and enters the short arm. The reflected light propagates in the long arm, and the path is longer, while the transmitted light propagates in the short arm, and the path is shorter. Due to the different path lengths, there will be a phase difference when the two optical signals meet at the combiner. The phase difference can be calculated by the following formula: ; in, is the wave number, is the path length of the long arm, is the path length of the short arm.

[0042] S320: Combining the long-arm signal and the short-arm signal into a beam and interfering them at an output point to form an interference signal.

[0043] like Figure 3 As shown, the two optical signals are recombined and interfere at the combiner to form an interference signal a. The intensity of the interference signal can be expressed by the following formula: ; in, is the intensity of the long-arm optical signal, is the intensity of the short arm light signal.

[0044] The interference signal a forms interference at both the high-level and low-level amplitude positions. The amplitude of the interference signal is a random optical signal. When the phase difference is 0 or 2nπ, the interference intensity reaches its maximum value, which is the high-level amplitude position. When the phase difference is (2n+1)π, the interference intensity reaches its minimum value, which is the low-level amplitude position. Due to the difference in path length between the long arm and the short arm, the phase difference will randomly change with time and environmental conditions. At different times, the phase difference will randomly change between 0 and 2π, causing the intensity of the interference signal to randomly fluctuate between the maximum and minimum values. Since the interference signal a depends on the randomly changing phase difference, the amplitude of the interference signal a formed at the output point is random. The randomness of the interference signal a comes from the random change of the phase difference, causing the intensity of the interference signal to show random fluctuations at different time points.

[0045] S330: Convert the interference signal into an electrical signal.

[0046] The interference signal can be converted into an electrical signal b through a detector. The electrical signal b is an analog signal. The response characteristics of the detector can be represented by a constant η, which is called the quantum efficiency or responsivity of the detector. η represents the amplitude of the electrical signal b corresponding to the unit light intensity. The electrical signal b converted by the detector is proportional to the intensity of the interference signal a, see the following formula: ; Specifically, the photodetector converts the intensity of the optical signal into the amplitude of the electrical signal. The amplitude of the electrical signal b is proportional to the intensity of the interference signal a, and the proportionality coefficient is η, see the following formula: ; Since the intensity of interference signal a is random, the amplitude of electrical signal b will also fluctuate randomly. The randomness of electrical signal b comes from the random change of the phase difference of interference signal a. By utilizing the linear response characteristics of the detector, the randomness of the optical signal is converted into the randomness of the electrical signal.

[0047] S340: Convert the analog signal into a second digital signal.

[0048] The electrical signal b is converted into a digital signal, i.e., the second digital signal, using an analog-to-digital converter. The analog-to-digital converter samples the electrical signal b at a fixed sampling frequency to generate a series of discrete digital values. The sampling frequency is high to ensure that the rapid changes of the electrical signal b are captured. The digital value of each sampling point represents the amplitude of the electrical signal b at that moment.

[0049] S350: Generate a first digital signal using the second digital signal.

[0050] In some embodiments, denoising, filtering and randomness enhancement operations are performed on the second digital signal. Specifically, a digital filter is used to remove noise and interference in the sampled signal to improve signal quality, wherein the filtering method includes low-pass filtering, high-pass filtering and band-pass filtering.

[0051] In order to remove some non-random components, the second digital signal is further randomized. Randomness enhancement can make the generated random numbers have high randomness and low predictability. Randomness enhancement can be achieved through various methods, such as hash functions, chaos mapping and other algorithms.

[0052] Taking randomness enhancement through hash function as an example, the second digital signal can be converted into a 256-bit hash value with high randomness and anti-collision. Taking randomness enhancement through chaotic mapping as an example, a highly random sequence can be generated by utilizing the nonlinearity and sensitivity of the chaotic system.

[0053] After processing the second digital signal, a high-quality random number is generated, and the random number can be expressed by the following formula: ; Among them, f is the processing function of denoising, filtering and randomness enhancement operations.

[0054] The first digital signal d is a completely random digital signal and can be directly used in application scenarios that require high-quality random numbers. The signal d can be generated using a dedicated true random number generator (TRNG) or a quantum random number generator (QRNG).

[0055] S400: Generate a first driving signal based on the first digital signal.

[0056] In some embodiments, a first control signal is generated according to a first digital signal, the first control signal is a control signal having a coding protocol, and then based on the coding protocol, a second drive signal is output according to the first control signal, and a first drive signal is generated according to the second drive signal, the first drive signal is a multi-amplitude drive signal.

[0057] For the generated first digital signal d, a coding rule is selected according to a specific QKD (Quantum Key Distribution) protocol, for example, the BB84 protocol or the E91 protocol is selected. The BB84 protocol randomly selects a basis and a coding state, and then generates a control signal, namely, a first control signal e, which represents the selected basis and coding state. The E91 protocol randomly selects a Bell state and generates a control signal, namely, a first control signal e, which represents the selected Bell state. The control signal e is a set of control signals with a coding protocol.

[0058] The first driving signal is used to control the modulator. The first control signal is sent to the second controller. After receiving the first control signal, the second controller generates a set of driving signals f, namely the second driving signals. The driving signal f is used to output a multi-amplitude RF driving signal g, namely the first driving signal.

[0059] Taking the E91 protocol as an example, the first digital signal d is a series of random bits, such as: 01011010..., a Bell state is randomly selected for encoding, and the four Bell states can be represented as 00, 01, 10, 11. Every two bits of the random number signal d are used as a unit to represent the selection of a Bell state. For example, the random number signal d is 01011010..., which can be divided into 01, 01, 10, 10... The control signal e generated by the encoding controller represents the selected Bell state. For example, the control signal e can be represented as: 01, 01, 10, 10, and the control signal e is output to the second controller.

[0060] After the driving signal f is generated, the correspondence between the Bell state and the driving signal can be set. For example, 00 corresponds to the driving signal f1. According to each binary number in the control signal e, the corresponding driving signal is selected. For example, the control signal e is 01, 01, 10, ..., then the generated driving signal f is f2, f2, f3, ..., and then according to the received driving signal f, a set of multi-amplitude RF driving signals g are output.

[0061] The driving signal f generated by the second controller determines the amplitude of the RF driving signal g. Depending on the driving signal f, the RF driving signal g may have different amplitudes, forming a driving signal with multiple amplitudes.

[0062] like Figure 4 As shown in the figure, the randomness of the RF drive signal g comes from the amplitude of the signal a, and the amplitude of the signal a comes from the amplitude fluctuation and phase uncertainty of the low-level output of the pulse light source. This amplitude fluctuation and phase uncertainty are generated by the basic principles of quantum mechanics and have unmeasurable characteristics. Due to the randomness of quantum mechanics, the randomness of the signal g is true randomness and cannot be predicted by any method.

[0063] S500: Based on the first driving signal, quantum state modulate the first light to generate a quantum state modulation signal.

[0064] In some embodiments, the first driving signal is loaded on a modulator in the interferometer, and the first light is quantum-modulated by the modulator to generate a quantum-modulated signal. The Mach-Zehnder (AMZ) interferometer is an optical interferometer for generating and detecting interference signals. The AMZ interferometer includes two beam splitters, two reflectors, and a modulator. The modulator can be used to phase or amplitude modulate the optical signal, thereby realizing quantum state modulation.

[0065] In some embodiments, the quantum state of the first light is modulated according to the first driving signal to generate a modulated light signal, the modulated light signal is then interfered with the first light to generate an interfered light signal, and the interfered light signal is detected to extract the quantum state signal.

[0066] The modulator is used to modulate the phase or amplitude of the optical signal. In the AMZ interferometer, the modulator is located on an interferometer arm and modulates the quantum state by changing the phase or amplitude of the optical signal. A random RF drive signal g is loaded onto the modulator. The randomness of the signal g comes from the amplitude fluctuation and phase uncertainty of the signal a. These fluctuations and uncertainties are generated by the basic principles of quantum mechanics and have unmeasurable characteristics.

[0067] like Figure 5 As shown, the first light is an optical signal modulated by the modulator, and the optical signal passes through an interference arm of the AMZ interferometer. The modulator performs phase or amplitude modulation on the first light according to the loaded RF drive signal g. For example, if the modulator is a phase modulator, the amplitude change of the signal g will cause the phase of the optical signal to change. If the modulator is an amplitude modulator, the amplitude change of the signal g will cause the amplitude of the optical signal to change. The modulated first impulse light meets other optical signals at the beam combiner of the AMZ interferometer to form an interference signal. Due to the phase or amplitude change introduced by the modulator, the intensity and phase of the interference signal will change randomly, thereby realizing quantum state modulation of the first light.

[0068] When the signal g is loaded onto the modulator, the modulator will randomly modulate the phase or amplitude of the first light. This random modulation can increase the randomness of the optical signal, making it difficult for attackers to predict or copy the state of the optical signal. Through the random modulation of the signal g, optical signals with different quantum states can be generated at different time points. The generated quantum states are diverse, which can increase the security of key distribution.

[0069] The quantum state modulated signal is the signal for quantum key distribution. It is randomly modulated by the signal g, and the generated quantum state is highly random and unpredictable. This randomness can ensure the security of key distribution and guarantee the secure transmission of keys even in the presence of eavesdroppers.

[0070] Based on the above quantum key transmitter quantum state modulation method, Figure 6 As shown, some embodiments of the present application also provide a quantum key sending end quantum state modulation device, including: The first controller is used to obtain pulse light, where the pulse light is periodic light or random noise light. The first controller can be a CPU, a field programmable gate array (FPGA), etc.

[0071] The beam splitter is used to form the pulse light into a first light path and a second light path. The beam splitter is a semi-transparent mirror that can reflect part of the incident light and transmit the other part.

[0072] The random number generation module is used to generate a first digital signal based on the second light, and the first digital signal is used to generate a random number.

[0073] In some embodiments, the random number generation module includes: The unequal-arm interferometer is used to output a long-arm signal and a short-arm signal, and to combine the long-arm signal and the short-arm signal, and interfere at the output point to form an interference signal, the amplitude of the interference signal is a random optical signal.

[0074] The unequal-arm interferometer consists of a beam splitter, two paths of different lengths (long arm and short arm), and a beam combiner. The beam splitter splits the incident light into two paths, and the long arm and short arm light signals pass through paths of different lengths respectively. The beam combiner recombines the two light signals to form an interference signal.

[0075] The detector is used to convert the interference signal into an electrical signal, which is an analog signal, and the amplitude of the electrical signal is proportional to the amplitude of the interference signal; the detector can be a photodetector, such as a PIN photodiode or an avalanche photodiode, which converts the intensity of the optical signal into the amplitude of the electrical signal.

[0076] The sampler converts the analog signal into a second digital signal; the sampler is a high-speed ADC (Analog-to-Digital Converter). The high-speed ADC is an analog-to-digital converter, which is used to convert analog signals (such as actual electrical signals such as temperature, pressure, voltage, current, etc.) into digital signals. The high-speed ADC can sample analog signals at a very high rate, so that the high-frequency components in the analog signal can be captured. The high-speed ADC has a high resolution, which means that it can represent subtle changes in the analog signal. The high resolution helps reduce quantization errors and improve conversion accuracy. The high-speed ADC has a lower noise level, which helps reduce noise interference introduced during the conversion process and improves the signal-to-noise ratio of the signal.

[0077] The post-processing unit is used to generate the first digital signal through the second digital signal. The signal denoising can be performed by a low-pass, high-pass or band-pass filter, and the filtering can be performed by a software filter.

[0078] Also included is a driving control module for generating a first driving signal based on the first digital signal.

[0079] In some embodiments, the drive control module includes: The coding controller is used to generate a first control signal according to the first digital signal, wherein the first control signal is a control signal having a coding protocol.

[0080] The second controller is used to output a second driving signal according to the first control signal based on the coding protocol.

[0081] In some embodiments, the encoding controller and the second controller are CPU or FPGA, and the specific implementation method depends on the requirements and resources of the system.

[0082] The driving unit is used to generate a first driving signal according to the second driving signal, and the first driving signal is a multi-amplitude driving signal. The driving unit includes a digital-to-analog converter and a radio frequency module, wherein the high-speed DAC is used to convert the digital signal into an analog signal, and the radio frequency module is used to generate a radio frequency driving signal. The driving signal f is loaded onto the high-speed DAC, and the high-speed DAC converts the digital signal into an analog signal, and generates a radio frequency driving signal g according to the analog signal.

[0083] The quantum state modulation module is used to perform quantum state modulation on the first light based on the first driving signal to generate a quantum state modulation signal, where the quantum state modulation signal is a signal for quantum key distribution.

[0084] It can be understood that the two embodiments correspond to each other, and the contents described in the embodiment of the quantum state modulation method at the quantum key sending end will not be repeated in the embodiment of the quantum state modulation device at the quantum key sending end, and they can be referenced to each other.

[0085] The present application utilizes the phase noise of a coded laser to generate a random number source, thereby realizing quantum state modulation of a coded laser pulse light source. The coded laser is used as a seed source to generate quantum random numbers, thereby replacing the random number source based on physical noise in existing quantum secure communication products. The light intensity portion below the threshold current is driven to interfere, and its phase noise is converted into intensity information for sampling to obtain a quantum random number seed source. The two functions of random number generation and encoding are realized by one laser, thereby having the advantages of miniaturization, cost reduction, and high reliability. The application also realizes the generation of a group of random numbers by an optical signal below the threshold current in each pulse interval, thereby realizing modulation of the pulse coding information.

[0086] The present application provides a quantum state modulation method and device for a quantum key transmitter, the method comprising: obtaining pulsed light, the pulsed light being periodic light generated by a coding laser; forming a first light path and a second light path by the pulsed light, generating a first digital signal based on the second light path, the first digital signal being used to generate a random number, generating a first drive signal based on the first digital signal, and performing quantum state modulation on the first light path based on the first drive signal to generate a quantum state modulation signal, the quantum state modulation signal being a signal for quantum key distribution. Random numbers are generated by using a coding laser as a seed source to replace random data based on physical noise, and quantum state modulation of a pulsed light source is achieved by using random numbers, which has unpredictable characteristics and can improve security.

[0087] Similar parts between the embodiments provided in this application can be referenced to each other. The specific implementation methods provided above are only a few examples under the general concept of this application and do not constitute a limitation on the protection scope of this application. For those skilled in the art, any other implementation methods expanded based on the scheme of this application without creative work belong to the protection scope of this application.

Claims

1. A quantum key sending end quantum state modulation method, characterized in that: include: Acquire pulsed light, wherein the pulsed light is periodic light generated by a coded laser; The pulsed light is used to form a first light path and a second light path; Generate a first digital signal based on the second light, where the first digital signal is used to generate a random number; generating a first driving signal based on the first digital signal; Based on the first driving signal, quantum state modulation is performed on the first light to generate a quantum state modulation signal, where the quantum state modulation signal is a signal for quantum key distribution.

2. The quantum state modulation method of the quantum key transmitter according to claim 1, characterized in that: The step of obtaining pulsed light comprises: Acquiring a second driving signal; When the second driving signal is at a low level, the pulse light outputs a periodic light, the initial phase of the periodic light is an undetermined value, and the pulses are emitted in a periodic manner; When the second driving signal is at a high level, the pulse light outputs random noise light, and the phase of the random noise light is a random phase.

3. The quantum state modulation method of the quantum key transmitter according to claim 1, characterized in that: The forming of the first light path and the second light path by the pulse light comprises: injecting the pulsed light onto a beam splitter; Acquire the type of the beam splitter, which is a symmetric beam splitter or an asymmetric beam splitter; Based on the type, the pulse light is divided into a first light path and a second light path by the beam splitter, wherein the first light path is light propagating along a reflection path, and the second light path is light propagating along a transmission path.

4. The quantum state modulation method of the quantum key transmitter according to claim 1, characterized in that: The generating a first digital signal based on the second light comprises: Passing the second light through an unequal-arm interferometer to output a long-arm signal and a short-arm signal; The long arm signal and the short arm signal are combined and interfered at an output point to form an interference signal, wherein the amplitude of the interference signal is a random optical signal; Converting the interference signal into an electrical signal, wherein the electrical signal is an analog signal, and the amplitude of the electrical signal is proportional to the amplitude of the interference signal; converting the analog signal into a second digital signal; A first digital signal is generated by using the second digital signal.

5. The quantum state modulation method of the quantum key transmitter according to claim 1, characterized in that: The generating a first driving signal based on the first digital signal comprises: Generate a first control signal according to the first digital signal, wherein the first control signal is a control signal having a coding protocol; Based on the coding protocol, output a second driving signal according to the first control signal; A first driving signal is generated according to the second driving signal, wherein the first driving signal is a driving signal with multiple amplitudes.

6. The quantum state modulation method of the quantum key transmitter according to claim 1, characterized in that: The step of performing quantum state modulation on the first light based on the first driving signal to generate a quantum state modulation signal includes: Applying the first driving signal to a modulator in an interferometer; The first light is quantum-modulated by the modulator to generate a quantum-modulated signal.

7. The quantum state modulation method of the quantum key transmitter according to claim 6, characterized in that: The step of performing quantum state modulation on the first light by the modulator to generate a quantum state modulation signal includes: modulating the quantum state of the first light according to the first driving signal to generate a modulated light signal; interfering the modulated optical signal with the first light to generate an interfered optical signal; The interfered optical signal is detected to extract the quantum state signal.

8. A quantum key transmitter quantum state modulation device, characterized in that: include: A first controller is used to obtain pulse light, where the pulse light is periodic light generated by a coded laser; A beam splitter, used for forming the pulsed light into a first light path and a second light path; A random number generation module, used to generate a first digital signal based on the second light, wherein the first digital signal is used to generate a random number; A drive control module, configured to generate a first drive signal based on the first digital signal; A quantum state modulation module is used to perform quantum state modulation on the first light based on the first driving signal to generate a quantum state modulation signal, where the quantum state modulation signal is a signal for quantum key distribution.

9. The quantum key transmitter quantum state modulation device according to claim 8, characterized in that: The random number generation module comprises: An unequal-arm interferometer, used for outputting a long-arm signal and a short-arm signal, and combining the long-arm signal and the short-arm signal, and interfering at an output point to form an interference signal, wherein the amplitude of the interference signal is a random optical signal; A detector, used to convert the interference signal into an electrical signal, wherein the electrical signal is an analog signal, and the amplitude of the electrical signal is proportional to the amplitude of the interference signal; A sampler, converting the analog signal into a second digital signal; A post-processing unit is used to generate a first digital signal through the second digital signal.

10. The quantum state modulation device at the quantum key transmitting end according to claim 8, characterized in that: The drive control module comprises: A coding controller, configured to generate a first control signal according to the first digital signal, wherein the first control signal is a control signal having a coding protocol; A second controller, configured to output a second driving signal according to the first control signal based on a coding protocol; The driving unit is used to generate a first driving signal according to a second driving signal, wherein the first driving signal is a multi-amplitude driving signal, and the driving unit includes a digital-to-analog converter and a radio frequency module.

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