Miniaturized quantum key distribution system and method

Abstract

The application belongs to the technical field of quantum secure communication, and discloses a miniaturized quantum key distribution system and method, wherein a system transmitting module and a system receiving module transmit quantum signals through free space, and complete classical communication through a public channel; the system generates and updates shared keys based on a polarization encoding BB84 protocol; the transmitting module comprises an LED array, a driving circuit and a beam combining and collimating module; the receiving module comprises a focusing and beam splitting module, a single photon detection array module and a collecting and processing circuit; compared with the prior art, the application uses commercial off-the-shelf components, greatly reduces the hardware cost, solves the problem of high price of the existing system, can be integrated into a handheld device, meets the portable demand of consumer-level applications, realizes stable operation under shadow sunlight conditions through narrowband filtering, temperature control and dynamic gate width adjustment, expands the application scenarios, realizes continuous security protection through regular key "recharge", and promotes the civilianization of quantum encryption technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of quantum secure communication, in particular to a miniaturized quantum key distribution system and method. BACKGROUND

[0002] Quantum key distribution has information theory security, and its security is guaranteed by the basic principles of quantum mechanics, and can resist threats from quantum computers, and plays an important role in secure communication. The most mature quantum key distribution (QKD) protocol is BB84 protocol, which has entered the practical stage. However, the existing QKD system has the following defects: first, the cost is high, and customized special components are used, and the price is expensive; second, the volume is large, and the optical system and control circuit are complex, and it is difficult to integrate into a small device; third, the environmental adaptability is poor, and most free space QKD systems can only work at night or in low background light conditions, which limits the application scene; fourth, the popularization is insufficient, and there is a lack of miniaturized and low-cost solutions for ordinary consumers, which cannot meet the security needs of daily transactions, online payments and other scenes.

[0003] With the rapid development of electronic commerce and mobile payment, the fraud risk of "cardless transaction" and other scenes continues to rise, and a high-security, low-cost and easy-to-popularize encryption technology is urgently needed. Therefore, developing a compact, low-cost and sunlight working QKD system is of great significance for promoting the popularization of quantum encryption technology. SUMMARY

[0004] In view of the above defects of the prior art, the present application provides a miniaturized quantum key distribution system and method.

[0005] The technical scheme of the present application is as follows:

[0006] A miniaturized quantum key distribution system, comprising a transmitting module Alice and a receiving module Bob, the transmitting module and the receiving module transmit quantum signals through free space, and complete classical communication through a public channel, and the system realizes generation and update of shared keys based on polarization encoding BB84 protocol;

[0007] The transmitting module comprises an LED array, a driving circuit and a beam combining and collimating module,

[0008] The LED array comprises four LEDs, and a polarizing plate is attached to the light emitting surface of each LED, and the polarization directions are H (0°), D (45°), V (90°) and A (135°), respectively, for generating corresponding four polarization states;

[0009] The driving circuit is used for controlling each LED to emit pulsed light of two intensities, which are used to generate signal states and decoy states, respectively.

[0010] The beam combining collimation module comprises a diffraction grating, a filter and a collimation lens;

[0011] The diffraction grating is used for combining the light beams generated by the four LEDs into one light beam;

[0012] The filter is used for filtering the combined light beam into a narrow linewidth light signal;

[0013] The collimation lens is used for realizing light beam collimation and emitting the quantum signal light beam into a free space channel;

[0014] The receiving module comprises a focusing beam splitting module, a single photon detection array module and an acquisition processing circuit;

[0015] The focusing beam splitting module comprises a focusing lens, a filter and a diffraction grating;

[0016] The focusing lens is used for receiving the light beam transmitted by the free space channel and realizing light beam convergence;

[0017] The filter is used for filtering background light noise;

[0018] The diffraction grating is used for uniformly splitting the filtered light beam into four spatially separated light beams;

[0019] The single photon detection array module comprises four avalanche photodiodes (APDs), and a polarizer is attached in front of the light sensitive surface of each APD, and the polarization directions are H (0°), D (45°), V (90°) and A (135°) respectively, which are used for detecting the polarization states of the four light beams;

[0020] The acquisition processing circuit is used for acquiring and processing the detection counts generated by the four APDs.

[0021] Preferably, the system further comprises a matching software, and the matching software comprises a synchronization calibration module, an error correction module and a privacy amplification module;

[0022] The synchronization calibration module determines the transmission starting point by searching for a time tag frequency mutation, realizes clock synchronization based on a 200 ns pulse period, and completes accurate time alignment through random subset correlation analysis;

[0023] The error correction module adopts an LDPC algorithm to complete one-way error correction through the transmission of an error correction syndrome by the transmitting end;

[0024] The privacy amplification module determines a compression ratio based on a security key rate formula, removes potential eavesdropping information and optimizes key security.

[0025] Preferably, the diffraction grating of the transmitting module and the receiving module is a Dammam grating, which divides the incident light beam into a 1*4 linear array light path, realizes random base vector selection, and the efficiency of the polarization encoding BB84 protocol is 25%, which is suitable for the low loss characteristics of short distance transmission scene.

[0026] Preferably, the optical components of the transmitting module and the receiving module are holographic diffraction gratings, which divide the incident light beam into a 2*2 matrix light path, realize random base vector selection, and the efficiency of the polarization encoding BB84 protocol is 25%, which is suitable for the low loss characteristics of short distance transmission scene.

[0027] Preferably, the LED is an AlInGaP micro red-orange light LED, and the light intensity is balanced by adjusting the working current of each diode, the average pulse width is 2.4ns, the repetition frequency is 10MHz, and the average single pulse photon number of the signal state and the decoy state is 0.3 and 0.1 respectively.

[0028] Preferably, the narrow-band filter of the transmitting module and the receiving module is 632.8+3nm, which is used to suppress background light interference.

[0029] Preferably, the transmitting module can be integrated into a handheld device such as a mobile phone, and the receiving module is integrated into a fixed terminal such as an ATM machine, the handheld device and the fixed terminal use IrDA infrared or Bluetooth as a public channel to realize key "recharge" and transaction encryption, and the effective transmission distance of the system is within 1 meter.

[0030] The application also discloses a quantum key distribution method, comprising the following steps:

[0031] S1: initialization, the transmitting end and the receiving end share an initial key;

[0032] S2: quantum transmission, the transmitting end generates a random bit string, controls the LED to emit a photon pulse in a corresponding polarization state, the receiving end selects a measurement base vector through a grating, and a single-photon detection array records the photon arrival time and polarization information;

[0033] S3: base vector comparison, the receiving end informs the transmitting end of the measurement base vector through a public channel, the transmitting end feeds back the bit position corresponding to the correct base vector, and the original key is obtained by screening by both parties;

[0034] S4: synchronization and error correction, clock and data alignment are realized through a synchronization calibration module, and error correction is completed by using an LDPC algorithm;

[0035] S5: privacy amplification, potential eavesdropping information is removed, and a final secure key is generated;

[0036] S6: Key update, repeat steps S2-S5 to realize the periodic "recharge" of the key.

[0037] Compared with the prior art, the present application has the following advantages:

[0038] Cost advantage: using commercial off-the-shelf components (LED, avalanche photodiode, digital I / O card, etc.) instead of custom components, significantly reducing hardware costs and solving the problem of high prices of existing systems.

[0039] Compactness: simplify the optical structure by using holographic diffraction gratings, and the emission module and the receiving module are small in size and can be integrated into handheld devices, meeting the portability requirements of consumer-level applications.

[0040] Environmental adaptability: through narrowband filtering, temperature control and dynamic gate width adjustment, stable operation under shadow daylight conditions is realized, and the application scenarios are expanded.

[0041] Ease of popularization: adapt to consumer-level scenarios such as ATM transactions and online payments, and realize continuous security protection through periodic key "recharge", promoting the civilianization of quantum encryption technology. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The present application discloses a miniaturized quantum key distribution system, which comprises a transmitting module Alice, a receiving module Bob and a supporting software system.

[0043] Figure 2 The present application discloses a miniaturized quantum key distribution system, which comprises a transmitting module Alice, a receiving module Bob and a supporting software system.

[0044] Figure 3 The present application discloses a miniaturized quantum key distribution system, which comprises a transmitting module Alice, a receiving module Bob and a supporting software system. DETAILED DESCRIPTION

[0045] The present application will be described clearly and completely in combination with the drawings in the embodiments of the present application.

[0046] The present application discloses a miniaturized quantum key distribution system, which comprises a transmitting module Alice, a receiving module Bob and a supporting software system.

[0047] The transmitting module comprises a light-emitting diode (LED) array, a driving circuit and a beam combining and collimating module,

[0048] The LED array comprises four LEDs, and a polarizing plate is attached to the light-emitting surface of each LED, and the polarization directions are H (0°), D (45°), V (90°) and A (135°), respectively, for generating corresponding four polarization states.

[0049] The driving circuit is used for controlling each LED to emit pulsed light of two intensities, respectively used for generating a signal state and a decoy state;

[0050] The beam combining and collimating module comprises a diffraction grating, a filter and a collimating lens;

[0051] The diffraction grating is used for combining the light beams generated by the four LEDs into one light beam;

[0052] The filter is used for filtering the combined light beam into a narrow linewidth optical signal;

[0053] The collimating lens is used for realizing light beam collimation and emitting the quantum signal light beam into a free space channel;

[0054] The receiving module comprises a focusing and splitting module, a single photon detection array module and an acquisition and processing circuit;

[0055] The focusing and splitting module comprises a focusing lens, a filter and a diffraction grating;

[0056] The focusing lens is used for receiving the light beam transmitted by the free space channel and realizing light beam convergence;

[0057] The filter is used for filtering background light noise;

[0058] The diffraction grating is used for uniformly splitting the filtered light beam into four spatially separated light beams;

[0059] The single photon detection array module comprises four avalanche photodiodes (APDs), and a polarizer is attached in front of the light sensitive surface of each APD, and the polarization directions are H (0°), D (45°), V (90°) and A (135°), respectively, which are used for detecting the polarization states of the four light beams;

[0060] The acquisition and processing circuit is used for acquiring and processing the detection counts generated by the four APDs.

[0061] The matching software system comprises a synchronization calibration module, an error correction module and a privacy amplification module;

[0062] The synchronization calibration module determines the transmission starting point by searching for a time tag frequency mutation, realizes clock synchronization based on a 200 ns pulse period, and completes accurate time alignment through random subset correlation analysis;

[0063] The error correction module adopts an LDPC algorithm, and completes one-way error correction through the transmission of an error correction check sub by the transmitting end;

[0064] The privacy amplification module determines the compression ratio based on a security key rate formula, removes potential eavesdropping information and optimizes key security.

[0065] The working process is as follows:

[0066] The emission module randomly lights up one LED in the LED array through the driving circuit, emits a light pulse signal, and generates a signal state or a decoy state by randomly selecting one of the two driving currents to control the intensity of the light signal emitted by the LED. Among them, the larger of the two driving currents corresponds to the signal state, and the smaller corresponds to the decoy state.

[0067] Since a polarizer is attached to the light-emitting surface of each LED, the polarization directions are H (0°), D (45°), V (90°), and A (135°), respectively. The light beams emitted by the four LEDs can produce corresponding four polarization states H, D, V, and A after passing through the polarizers, and then be combined into one beam through the diffraction grating. The light beam contains polarization-encoded quantum state light pulses.

[0068] The diffraction grating is composed of a large number of parallel slits with equal width and equal spacing (or transparent / opaque periodic structures). The spacing between the slits is called the "grating constant" (d). When incident light passes through each slit, single-slit diffraction occurs, and multiple-slit interference occurs between the diffraction lights of different slits. By designing the grating constant d, the slit width a, and the grating material, the light intensities of multiple diffraction orders (±1, ±2) are made consistent, and the useless 0-order light is suppressed, thereby realizing uniform distribution of incident light in four directions.

[0069] The grating constant d is matched with the wavelength λ of the incident light, satisfying the grating equation d・sinθ = mλ (m is the diffraction order, and θ is the diffraction angle), ensuring the orderly separation of the required diffraction light. The ratio of the slit width a to the grating constant d (a / d) is controlled to adjust the light intensity of each diffraction order through the envelope of single-slit diffraction, such as using an optimized a / d ratio to make the light intensities of ±1 and ±2 orders equal.

[0070] Although the light path is combined through the diffraction grating, since only one LED is lit up at a time, only the light signal of one LED, i.e., one polarization state, will appear in the combined light path.

[0071] The light signal after combining passes through a narrow-band filter and a collimating lens to produce a parallel light beam for emission into a free-space channel.

[0072] In the receiving module, the polarization-encoded quantum state light pulse passes through the focusing lens to realize beam convergence, and passes through the narrow-band filter to filter out the background light noise, and then passes through the diffraction grating to realize four-way beam splitting. Each way enters the APD with a polarization direction of H or D or V or A, realizing random base vector selection and polarization state measurement. Since the probability of each polarization-encoded quantum state entering the four light paths through the diffraction grating is equal, the polarization-encoded BB84 protocol efficiency of the system is 25%, which is suitable for the low-loss characteristics of short-distance transmission scenarios.

[0073] After the transmitting module and the receiving module transmit quantum signals through free space, both parties transmit classical information through public channels such as the Internet, IrDA infrared, or Bluetooth, including performing base selection, error correction, and privacy amplification, and completing key generation based on the BB84 protocol.

[0074] In the software system, the synchronization calibration module realizes precise synchronization through time tag analysis and clock drift compensation; the error correction module uses the LDPC algorithm to reduce the number of interactions and improve error correction efficiency; and the privacy amplification module removes eavesdropping information based on the security key rate formula to ensure key security.

[0075] As shown in FIG. 1, Figure 1 Embodiment One:

[0076] The diffraction gratings of the transmitting module and the receiving module are both Dammann gratings DG, which divide the incident light beam into a 1×4 linear array of light paths, realizing random base vector selection. The polarization-encoded BB84 protocol efficiency is 25%, which is suitable for the low-loss characteristics of short-distance transmission scenarios.

[0077] The LEDs are AlInGaP micro red-orange light LEDs. The light intensity is balanced by adjusting the working current of each diode. The average pulse width is 2.4 ns, the repetition frequency is 10 MHz, and the average number of single pulses of signal state and decoy state is 0.3 and 0.1, respectively.

[0078] The narrow-band filters of the transmitting module and the receiving module are 632.8±3nm, which are used to suppress background light interference.

[0079] The three-dimensional schematic diagram of the optical module of Embodiment One is shown in FIG. 3. Figure 2 The working process is as follows:

[0080] The transmitting module randomly lights up one LED in the LED array through the driving circuit to emit a light pulse signal. The LEDs are AlInGaP micro red-orange light LEDs. The light intensity is balanced by adjusting the working current of each diode. The average pulse width is 2.4 ns, the repetition frequency is 10 MHz, and the average number of single pulses of signal state and decoy state is 0.3 and 0.1, respectively.

[0081] Since there is a polarizer adhered to the light-emitting surface of each LED, the polarization directions are H (0°), D (45°), V (90°), and A (135°), respectively. The light beams emitted by the four LEDs can generate four corresponding polarization states H, D, V, and A, respectively, after passing through the polarizers. Subsequently, the light beams are combined into one beam by the diffraction grating DG1. The light beam contains polarization-encoded quantum state light pulses.

[0082] The diffraction grating is a 1x4 diffraction grating composed of a large number of parallel slits with equal width and equal spacing (or transparent / non-transparent periodic structures). The spacing between the slits is referred to as the "grating constant" (d). When the incident light passes through each slit, single-slit diffraction occurs. The diffraction light of different slits will produce multi-slit interference. By designing the grating constant d, the slit width a, and the grating material, the light intensity of multiple diffraction orders (±1, ±2 orders) is made consistent, while the useless 0 order light is suppressed, thereby achieving uniform distribution of the incident light in four directions.

[0083] The grating constant d is matched with the wavelength λ of the incident light, satisfying the grating equation d・sinθ = mλ (m is the diffraction order, and θ is the diffraction angle), ensuring the orderly separation of the required diffraction light. The ratio of the slit width a to the grating constant d (a / d) is controlled to adjust the light intensity of each diffraction order through the envelope of single-slit diffraction. For example, by using an optimized a / d ratio, the light intensity of ±1 and ±2 orders is equalized.

[0084] Although the light path is combined by the diffraction grating, only one LED light signal, i.e., one polarization state, will appear in the combined light path at a time since only one LED is turned on at a time.

[0085] After the combined light signal passes through the narrow-band filter F1 and the collimating lens, a parallel light beam is generated and emitted into the free-space channel.

[0086] In the receiving module, the polarization-encoded quantum state light pulses are focused by the focusing lens, and the background light noise is filtered out by the narrow-band filter F2. Then, the light pulses are split into four beams by the diffraction grating DG2, and each beam enters the APD with a polarizer adhered to the surface of the APD, with the polarization direction being H, D, V, or A. This realizes random basis selection and polarization state measurement. Since each polarization-encoded quantum state has an equal probability of entering the four light paths through the diffraction grating, the efficiency of the polarization-encoded BB84 protocol of the system is 25%, which is suitable for low-loss short-distance transmission scenarios.

[0087] After the transmitting module and the receiving module transmit quantum signals through free space, both sides transmit classical information through public channels such as the Internet, IrDA infrared or Bluetooth, including performing base, error correction and privacy amplification, and completing key generation based on the BB84 protocol.

[0088] In the software system, the synchronization calibration module realizes precise synchronization through time tag analysis and clock drift compensation; the error correction module adopts the LDPC algorithm to reduce the number of interactions and improve error correction efficiency; and the privacy amplification module removes eavesdropped information based on the security key rate formula to ensure key security. Embodiment

[0089] The optical components of the transmitting module and the receiving module both adopt holographic diffraction gratings, which divide the incident light beam into a 2x2 matrix light path to realize random base vector selection, and the polarization encoding BB84 protocol has an efficiency of 25%, which is suitable for low-loss characteristics in short-distance transmission scenarios.

[0090] The LED is an AlInGaP micro red-orange light LED, and light intensity balance is achieved by adjusting the operating current of each diode, with an average pulse width of 2.4 ns, a repetition frequency of 10 MHz, and an average number of single pulses of 0.3 and 0.1 for signal state and decoy state, respectively, to ensure system security.

[0091] The narrow-band filter of the transmitting module and the receiving module is 632.8±3nm, which is used to suppress background light interference.

[0092] The transmitting module can be integrated into a handheld device such as a mobile phone, and the receiving module can be integrated into a fixed terminal such as an ATM machine, and the handheld device and the fixed terminal use IrDA infrared or Bluetooth as a public channel to realize key "recharge" and transaction encryption, and the effective transmission distance of the system is within 1 meter.

[0093] The three-dimensional schematic diagram of the optical module is shown in Figure 3 The working process is as follows:

[0094] The transmitting module randomly lights up one LED in the LED array through the driving circuit to emit an optical pulse signal. The LED is an AlInGaP micro red-orange light LED, and light intensity balance is achieved by adjusting the operating current of each diode, with an average pulse width of 2.4 ns, a repetition frequency of 10 MHz, and an average number of single pulses of 0.3 and 0.1 for signal state and decoy state, respectively.

[0095] Since a polarizer is attached to the light-emitting surface of each LED, the polarization directions are H (0°), D (45°), V (90°), and A (135°), respectively. The light beams emitted by the four LEDs can generate four corresponding polarization states H, D, V, and A, respectively, after passing through the polarizers. Subsequently, the light beams are combined into one beam by the holographic diffraction grating HDG1. The light beam contains polarization-encoded quantum state light pulses.

[0096] The holographic diffraction grating is a 2x2 diffraction grating that needs to achieve two-dimensional orthogonal beam splitting (e.g., horizontal and vertical directions, corresponding to ±1 level x ±1 level, a total of 4 beams). The grating needs to be designed as a two-dimensional periodic structure (e.g., a cross-shaped square lattice period). The grating constants in the two orthogonal directions need to be matched to ensure that the 4 beams are symmetrically emitted along the X and Y axes, thereby achieving uniform distribution of the incident light in four directions.

[0097] Although the light path is combined by the diffraction grating, only one LED's light signal, i.e., one polarization state, will appear in the combined light path because only one LED is turned on at a time.

[0098] The combined light signal passes through the narrow-band filter F1 and is collimated by the collimating lens to produce a parallel light beam that is emitted into the free-space channel.

[0099] In the receiving module, the polarization-encoded quantum state light pulses are focused by the focusing lens to converge the light beam, and the background light noise is filtered out by the narrow-band filter F2. Then, the light pulses are split into four paths by the HDG2, and each path enters the APD with a polarizer attached to the H, D, V, or A direction, respectively, to realize random basis selection and polarization state measurement. Since each polarization-encoded quantum state has an equal probability of entering the four paths through the diffraction grating, the efficiency of the polarization-encoded BB84 protocol of the system is 25%, which is suitable for low-loss characteristics in short-distance transmission scenarios.

[0100] After transmitting the quantum signals through the free space by the transmitting module and the receiving module, both parties transmit classical information, including basis selection, error correction, and privacy amplification, through public channels such as the Internet, IrDA infrared, or Bluetooth, to complete key generation based on the BB84 protocol.

[0101] In the software system, the synchronization calibration module achieves precise synchronization through time tag analysis and clock drift compensation. The error correction module uses the LDPC algorithm to reduce the number of interactions and improve error correction efficiency. The privacy amplification module removes eavesdropped information based on the security key rate formula to ensure the security of the secret key.

[0102] According to the principles and embodiments of the present application, commercial off-the-shelf components are used to replace customized components, greatly reducing the hardware cost and solving the problem of high cost of the existing system; the holographic diffraction grating simplifies the optical structure, the transmitting module and the receiving module are small in size and can be integrated into a handheld device, meeting the portable demand of consumer-level applications; through narrowband filtering, temperature control and dynamic gate width adjustment, stable operation under shadow sunlight conditions is realized, and the application scenarios are expanded; the present application is suitable for consumer-level scenarios such as ATM transactions and online payments, and through regular key "recharge", continuous security protection is realized, and the popularization of quantum encryption technology is promoted.

Claims

1. A miniaturized quantum key distribution system, characterized by, The system comprises a transmitting module Alice and a receiving module Bob, the transmitting module and the receiving module transmit quantum signals through free space, and complete classical communication through a public channel, and the system realizes generation and update of shared keys based on a polarization encoding BB84 protocol; The transmitting module comprises an LED array, a driving circuit and a beam combining and collimating module, The LED array comprises four LEDs, and a polarizing plate is attached to the light emitting surface of each LED, and the polarization directions are H (0°), D (45°), V (90°) and A (135°) respectively, for generating corresponding four polarization states; The driving circuit is used for controlling each LED to emit pulsed light of two intensities, which are respectively used for generating a signal state and a decoy state; The beam combining and collimating module comprises a diffraction grating, a filter and a collimating lens; The diffraction grating is used for combining the light beams generated by the four LEDs into one light beam; The filter is used for filtering the combined light beam into a narrow linewidth optical signal; The collimating lens is used for realizing beam collimation and transmitting the quantum signal light beam into a free space channel; The receiving module comprises a focusing and beam splitting module, a single photon detection array module and a collection and processing circuit; The focusing and beam splitting module comprises a focusing lens, a filter and a diffraction grating; The focusing lens is used for receiving the light beam transmitted in the free space channel and realizing beam convergence; The filter is used for filtering background light noise; The diffraction grating is used for uniformly splitting the filtered light beam into four spatially separated light beams; The single photon detection array module comprises four avalanche photodiodes (APDs), and a polarizing plate is attached to the light sensitive surface of each APD, and the polarization directions are H (0°), D (45°), V (90°) and A (135°) respectively, for detecting the polarization states of the four light beams; The collection and processing circuit is used for collecting and processing the detection counts generated by the four APDs.

2. The miniaturized quantum key distribution system of claim 1, wherein The system further comprises a matching software, and the matching software comprises a synchronization calibration module, an error correction module and a privacy amplification module; The synchronization calibration module determines a transmission starting point by searching for a time tag frequency mutation, realizes clock synchronization based on a 200 ns pulse period, and completes accurate time alignment through random subset correlation analysis; The error correction module adopts an LDPC algorithm, and completes one-way error correction through transmission of an error correction check subcode by the transmitting end; The privacy amplification module determines a compression ratio based on a secure key rate formula, removes potential eavesdropping information, and optimizes key security.

3. The miniaturized quantum key distribution system of claim 2, wherein The diffraction gratings of the transmitting module and the receiving module are both Dammann gratings, the Dammann gratings divide the incident light beam into a 1×4 linear array light path, realize random base vector selection, and the polarization encoding BB84 protocol has an efficiency of 25%, which is suitable for low loss characteristics of short distance transmission scenarios.

4. The miniaturized quantum key distribution system of claim 2, wherein, The optical components of the transmitting module and the receiving module are both holographic diffraction gratings, the gratings divide the incident light beam into a 2×2 matrix light path, realize random base vector selection, and the polarization encoding BB84 protocol has an efficiency of 25%, which is suitable for low loss characteristics of short distance transmission scenarios.

5. The miniaturized quantum key distribution system of claim 3, wherein The LED is a miniature red-orange light LED of AlInGaP, and the light intensity is balanced by adjusting the working current of each diode. The output pulse width is 2.4 ns on average, the repetition frequency is 10 MHz, and the average single-pulse photon numbers of the signal state and the decoy state are 0.3 and 0.1 respectively.

6. The miniaturized quantum key distribution system of claim 4, wherein, The narrow-band optical filter of the transmitting module and the receiving module is 632.8±3 nm, which is used for suppressing background light interference.

7. The miniaturized quantum key distribution system of claim 2, wherein The transmitting module is integrated in a handheld device, and the receiving module is integrated in a fixed terminal. The handheld device and the fixed terminal use IrDA infrared or Bluetooth as a public channel to realize key "recharge" and transaction encryption. The effective transmission distance of the system is within 1 meter.

8. A quantum key distribution method, employing the system of any one of claims 2-7, characterized in that, The method comprises the following steps: S1: initialization, the transmitting end and the receiving end share an initial key; S2: quantum transmission, the transmitting end generates a random bit string, controls the LED to emit a photon pulse of a corresponding polarization state, the receiving end selects a measurement basis vector through an optical grating, and a single-photon detection array records the photon arrival time and polarization information; S3: basis vector comparison, the receiving end informs the transmitting end of the measurement basis vector through a public channel, the transmitting end feeds back the bit position corresponding to the correct basis vector, and the original key is obtained by screening by both parties; S4: synchronization and error correction, clock and data alignment are realized through a synchronization calibration module, and error correction is completed by using an LDPC algorithm; S5: privacy amplification, potential eavesdropping information is removed, and a final secure key is generated; S6: key update, steps S2-S5 are repeated to realize periodic "recharge" of the key.

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