Miniaturized quantum key distribution system and method

Abstract

The invention belongs to the technical field of quantum security communication, and discloses a miniaturized quantum key distribution system and method, a system transmitting module and a receiving module perform quantum signal transmission through a free space, classic communication is completed through a public channel, and the system realizes generation and updating of a shared key based on a polarization coding BB84 protocol. The transmitting module comprises an LED array, a driving circuit and a beam combining and collimating module, and the receiving module comprises a focusing and beam splitting module, a single-photon detection array module and an acquisition and processing circuit. Compared with the prior art, commercial ready-made components are adopted, the hardware cost is greatly reduced, and the problem that an existing system is high in price is solved; the system can be integrated into a handheld device, and the portable requirement of consumer-level applications is met; through narrow-band filtering, temperature control and dynamic door width adjustment, stable work under the shadow sunlight condition is realized, and the application scene is expanded; and continuous security assurance is realized through regular key recharging, and civilization of the quantum encryption technology is promoted.

Description

Technical Field

[0001] This invention relates to the field of quantum secure communication technology, and in particular to a miniaturized quantum key distribution system and method. Background Technology

[0002] Quantum key distribution (QKD) possesses theoretical information security, guaranteed by the fundamental principles of quantum mechanics, and can resist threats from quantum computers, playing a crucial role in secure communication. The most mature QKD protocol is BB84, which has already entered the practical application stage. However, existing QKD systems suffer from the following drawbacks: First, they are costly, employing customized, specialized components that are expensive; second, they are bulky, with complex optical systems and control circuits that are difficult to integrate into small devices; third, they have poor environmental adaptability, with most free-space QKD systems only able to operate at night or in low-background-light conditions, limiting their application scenarios; and fourth, they lack widespread adoption, lacking miniaturized, low-cost solutions for ordinary consumers, failing to meet the security needs of everyday transactions, online payments, and other scenarios.

[0003] With the rapid development of e-commerce and mobile payments, the risk of fraud in scenarios such as "cardless transactions" continues to rise, creating an urgent need for a highly secure, low-cost, and easily accessible encryption technology. Therefore, developing a compact, low-cost QKD system that can operate under sunlight is of great significance for promoting the civilian application of quantum encryption technology. Summary of the Invention

[0004] In view of the above-mentioned defects in the existing technology, the present invention proposes a miniaturized quantum key distribution system and method.

[0005] The technical solution of this invention is implemented as follows: A miniaturized quantum key distribution system includes a transmitting module Alice and a receiving module Bob. The transmitting and receiving modules transmit quantum signals in free space and complete classical communication through a common channel. The system generates and updates a shared key based on the polarization coding BB84 protocol. The transmitting module includes an LED array, a driving circuit, and a beam combining and collimating module. The LED array contains four LEDs, with a polarizer attached to the light-emitting surface of each LED. The polarization directions are H (0°), D (45°), V (90°), and A (135°), respectively, to generate the corresponding four polarization states. The driving circuit is used to control each LED to emit pulse light of two intensities, which are used to generate a signal state and a decoy state, respectively. The beam combining and collimating module includes a diffraction grating, a filter, and a collimating lens; A diffraction grating is used to combine the beams generated by four LEDs into a single beam. Filters are used to filter the combined beam into a narrow linewidth optical signal; Collimating lenses are used to collimate light beams, enabling the transmission of quantum signal beams into free-space channels. The receiving module includes a focusing and splitting module, a single-photon detection array module, and a data acquisition and processing circuit. The focusing and beam-splitting module includes a focusing lens, a filter, and a diffraction grating; A focusing lens is used to receive light beams transmitted through a free-space channel, thereby converging the light beams. The filter is used to filter out background light noise; A diffraction grating is used to uniformly split a filtered beam into four spatially separated beams. The single-photon detection array module contains four avalanche photodiodes (APDs). A polarizer is attached to the front of each APD photosensitive surface, with polarization directions of H (0°), D (45°), V (90°), and A (135°), respectively, to detect the polarization state of the four beams. The acquisition and processing circuit is used to acquire and process the detection counts generated by the four APDs.

[0006] Preferably, the system further includes supporting software, which includes a synchronization calibration module, an error correction module, and a privacy amplification module; The synchronization calibration module determines the transmission start point by searching for abrupt changes in the time stamp frequency, achieves clock synchronization based on a 200ns pulse period, and completes precise time alignment through random subset correlation analysis. The error correction module uses the LDPC algorithm to complete one-way error correction by sending error correction checksums through the transmitter. The privacy amplification module determines the compression ratio based on the security key rate formula, removes potential eavesdropping information, and optimizes key security.

[0007] Preferably, both the transmitting module and the receiving module use damman gratings for their diffraction gratings. The damman gratings divide the incident beam into a 1×4 linear array optical path to achieve random basis selection. The polarization coding BB84 protocol has an efficiency of 25%, which is suitable for the low-loss characteristics of short-distance transmission scenarios.

[0008] Preferably, the optical components of both the transmitting module and the receiving module adopt holographic diffraction gratings. The gratings divide the incident beam into a 2×2 matrix optical path to achieve random basis selection. The polarization coding BB84 protocol has an efficiency of 25% and is adapted to the low-loss characteristics of short-distance transmission scenarios.

[0009] Preferably, the LED is an AlInGaP miniature red-orange LED, and the light intensity balance is achieved by adjusting the operating current of each diode. The average output pulse width is 2.4ns, the repetition frequency is 10MHz, and the average number of photons per pulse in the signal state and the decoy state are 0.3 and 0.1, respectively.

[0010] Preferably, the narrowband filters of the transmitting and receiving modules are 632.8±3nm, used to suppress background light interference.

[0011] Preferably, 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. The handheld device and the fixed terminal use IrDA infrared or Bluetooth as a common channel to realize key "recharge" and transaction encryption. The effective transmission distance of the system is within 1 meter.

[0012] This invention also discloses a quantum key distribution method, comprising the following steps: S1: Initialization, the transmitter and receiver share the initial key; S2: Quantum transmission, the transmitter generates a random bit string, controls the corresponding polarization state of the LED to emit photon pulses, the receiver selects the measurement basis vector through a grating, and the single photon detection array records the photon arrival time and polarization information; S3: Basis vector comparison. The receiver informs the transmitter of the measured basis vectors through a common channel. The transmitter feeds back the bit positions corresponding to the correct basis vectors. Both parties filter to obtain the original key. S4: Synchronization and error correction. Clock and data alignment is achieved through a synchronization calibration module, and error correction is completed using the LDPC algorithm. S5: Privacy enhancement, removal of potential eavesdropping information, and generation of the final security key; S6: Key update, repeat steps S2-S5 to achieve periodic "recharge" of the key.

[0013] Compared with the prior art, the present invention has the following beneficial effects: Cost advantage: By using commercially available off-the-shelf components (LEDs, avalanche photodiodes, digital I / O cards, etc.) to replace custom components, hardware costs are significantly reduced, solving the problem of high prices in existing systems.

[0014] Compactness: The optical structure is simplified by using a holographic diffraction grating, and the transmitting and receiving modules are small in size and can be integrated into handheld devices to meet the portability requirements of consumer applications.

[0015] Environmental adaptability: Stable operation under shaded and sunlight conditions is achieved through narrowband filtering, temperature control, and dynamic gate width adjustment, expanding application scenarios.

[0016] Easy to adopt: It is compatible with consumer-level scenarios such as ATM transactions and online payments, and achieves continuous security through regular key "recharge", promoting the civilian application of quantum encryption technology. Attached Figure Description

[0017] Figure 1 This is a principle block diagram of a first embodiment of the miniaturized quantum key distribution system of the present invention; Figure 2 This is a three-dimensional schematic diagram of the optical module in Embodiment 1 of the present invention; Figure 3 This is a three-dimensional schematic diagram of the optical module in Embodiment 2 of the present invention. Detailed Implementation

[0018] The present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0019] This invention discloses a miniaturized quantum key distribution system, including a transmitting module Alice, a receiving module Bob, and a supporting software system. The transmitting module and the receiving module transmit quantum signals through free space and complete classical communication through a common channel. The system realizes the generation and updating of shared keys based on the polarization coding BB84 protocol. The transmitting module includes a light-emitting diode (LED) array, a driving circuit, and a beam combining and collimating module. The LED array contains four LEDs, with a polarizer attached to the light-emitting surface of each LED. The polarization directions are H (0°), D (45°), V (90°), and A (135°), respectively, to generate the corresponding four polarization states. The driving circuit is used to control each LED to emit pulse light of two intensities, which are used to generate a signal state and a decoy state, respectively. The beam combining and collimating module includes a diffraction grating, a filter, and a collimating lens; A diffraction grating is used to combine the beams generated by four LEDs into a single beam. Filters are used to filter the combined beam into a narrow linewidth optical signal; Collimating lenses are used to collimate light beams, enabling the transmission of quantum signal beams into free-space channels. The receiving module includes a focusing and splitting module, a single-photon detection array module, and a data acquisition and processing circuit. The focusing and beam-splitting module includes a focusing lens, a filter, and a diffraction grating; A focusing lens is used to receive light beams transmitted through a free-space channel, thereby converging the light beams. The filter is used to filter out background light noise; A diffraction grating is used to uniformly split a filtered beam into four spatially separated beams. The single-photon detection array module contains four avalanche photodiodes (APDs). A polarizer is attached to the front of each APD photosensitive surface, with polarization directions of H (0°), D (45°), V (90°), and A (135°), respectively, to detect the polarization state of the four beams. The acquisition and processing circuit is used to acquire and process the detection counts generated by the four APDs.

[0020] The supporting software system includes a synchronous calibration module, an error correction module, and a privacy amplification module; The synchronization calibration module determines the transmission start point by searching for abrupt changes in the time stamp frequency, achieves clock synchronization based on a 200ns pulse period, and completes precise time alignment through random subset correlation analysis. The error correction module uses the LDPC algorithm to complete one-way error correction by sending error correction checksums through the transmitter. The privacy amplification module determines the compression ratio based on the security key rate formula, removes potential eavesdropping information, and optimizes key security.

[0021] The work process is as follows: The transmitting module randomly lights one LED in the LED array via a driving circuit, emitting a light pulse signal. It then generates either a signal state or a decoy state by randomly selecting one of two driving currents to control the intensity of the emitted light signal. The larger of the two driving currents corresponds to the signal state, and the smaller one corresponds to the decoy state.

[0022] Since a polarizer is attached to the light-emitting surface of each LED, with polarization directions of H (0°), D (45°), V (90°), and A (135°), the light beams emitted by the four LEDs can generate four corresponding polarization states H, D, V, and A after passing through the polarizers. Then, they are combined into a beam by a diffraction grating, and this beam contains polarization-coded quantum state light pulses.

[0023] A diffraction grating consists of a large number of parallel slits (or a periodic structure of alternating transparent and opaque slits) of equal width and spacing. The slit spacing is called the "grating constant" (d). When incident light passes through each slit, single-slit diffraction occurs. Multi-slit interference occurs between the diffracted light from different slits. By designing the grating constant d, the slit width a, and the grating material, the light intensity of multiple diffraction orders (±1, ±2 orders) can be made to be consistent, while suppressing useless 0th order light, thereby achieving uniform distribution of incident light in four directions.

[0024] The grating constant d is matched with the incident light wavelength λ, satisfying the grating equation d・sinθ = mλ (where m is the diffraction order and θ is the diffraction angle), ensuring the ordered separation of diffracted light of the desired order. The ratio (a / d) of the slit width a to the grating constant d is controlled, and the light intensity of each diffraction order is adjusted by the envelope of single-slit diffraction. For example, an optimized a / d ratio can be used to make the intensity of ±1 and ±2 orders equal.

[0025] Although the optical path achieves beam combining through a diffraction grating, since only one LED is lit at a time, only one LED's light signal will appear in the beam combining optical path, which is a polarization state.

[0026] The combined optical signal passes through a narrow-bandwidth filter and a collimating lens to generate a parallel beam that is then emitted into the free-space channel.

[0027] In the receiving module, the polarization-coded quantum state light pulses are focused by a focusing lens, and background noise is filtered out by a narrow-band filter. Then, the beam is split into four paths by a diffraction grating. Each path enters an APD (Optical Pointer) with a polarization direction of H, D, V, or A, enabling random basis selection and polarization state measurement. Since each polarization-coded quantum state has an equal probability of entering all four optical paths through the diffraction grating, the system's polarization-coded BB84 protocol has an efficiency of 25%, making it suitable for low-loss short-distance transmission scenarios.

[0028] After the transmitting and receiving modules transmit quantum signals in free space, they transmit classical information through public channels such as the Internet, IrDA infrared, or Bluetooth, including basis matching, error correction, and privacy amplification, and complete key generation based on the BB84 protocol.

[0029] 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; and the privacy amplification module uses a security key rate formula to remove eavesdropping information and ensure key security.

[0030] like Figure 1 As shown, Example 1: Both the transmitting and receiving modules use damman gratings (DG) for their diffraction. The damman grating divides the incident beam into a 1×4 linear array optical path to achieve random basis selection. The polarization coding BB84 protocol has an efficiency of 25% and is adapted to the low-loss characteristics of short-distance transmission scenarios.

[0031] The LED is an AlInGaP miniature red-orange LED. The light intensity balance is achieved by adjusting the operating current of each diode. The average output pulse width is 2.4ns, the repetition frequency is 10MHz, and the average number of photons per pulse in the signal state and the decoy state are 0.3 and 0.1, respectively.

[0032] The narrowband filters of the transmitting and receiving modules are 632.8±3nm, used to suppress background light interference. Example 1: 3D schematic diagram of the optical module (as shown below) Figure 2 As shown, the working process is as follows: The transmitting module randomly lights one LED in the LED array through the driving circuit to emit a light pulse signal. The LED is an AlInGaP miniature red-orange LED. The light intensity balance is achieved by adjusting the operating current of each diode. The average output pulse width is 2.4ns, the repetition frequency is 10MHz, and the average number of photons per pulse in the signal state and the decoy state are 0.3 and 0.1, respectively.

[0033] Since a polarizer is attached to the light-emitting surface of each LED, with polarization directions of H (0°), D (45°), V (90°), and A (135°), the light beams emitted by the four LEDs can generate four corresponding polarization states H, D, V, and A after passing through the polarizers. Then, they are combined into a beam by the Dammann grating DG1, which contains polarization-coded quantum state light pulses.

[0034] A Damman grating is a 1×4 diffraction grating composed of a large number of parallel slits (or a periodic structure of alternating transparent and opaque slits) of equal width and spacing. The slit spacing is called the "grating constant" (d). When incident light passes through each slit, single-slit diffraction occurs. Multi-slit interference occurs between the diffracted light from different slits. By designing the grating constant d, the slit width a, and the grating material, the light intensity of multiple diffraction orders (±1, ±2 orders) can be made to be consistent, while suppressing useless 0th order light, thereby achieving uniform distribution of incident light in four directions.

[0035] The grating constant d is matched with the incident light wavelength λ, satisfying the grating equation d・sinθ = mλ (where m is the diffraction order and θ is the diffraction angle), ensuring the ordered separation of diffracted light of the desired order. The ratio (a / d) of the slit width a to the grating constant d is controlled, and the light intensity of each diffraction order is adjusted by the envelope of single-slit diffraction. For example, an optimized a / d ratio can be used to make the intensity of ±1 and ±2 orders equal.

[0036] Although the optical path achieves beam combining through a diffraction grating, since only one LED is lit at a time, only one LED's light signal will appear in the beam combining optical path, which is a polarization state.

[0037] The combined optical signal passes through a narrow-bandwidth filter F1 and a collimating lens to generate a parallel beam that is then emitted into the free-space channel.

[0038] In the receiving module, the polarization-coded quantum state light pulses are focused by a focusing lens, and background noise is filtered out by a narrowband filter F2. Then, the beam is split into four paths by a Dammann grating DG2, with each path entering an APD (Optical Pointer) with polarization directions H, D, V, or A, enabling random basis selection and polarization state measurement. Since each polarization-coded quantum state has an equal probability of entering all four optical paths through the diffraction grating, the system's polarization-coded BB84 protocol has an efficiency of 25%, making it suitable for low-loss short-distance transmission scenarios.

[0039] After the transmitting and receiving modules transmit quantum signals in free space, they transmit classical information through public channels such as the Internet, IrDA infrared, or Bluetooth, including basis matching, error correction, and privacy amplification, and complete key generation based on the BB84 protocol.

[0040] 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; and the privacy amplification module uses a security key rate formula to remove eavesdropping information and ensure key security. Example

[0041] Both the transmitting and receiving modules employ holographic diffraction gratings in their optical components. These gratings divide the incident beam into a 2×2 matrix optical path, enabling random basis selection. The polarization coding BB84 protocol has an efficiency of 25%, adapting to the low-loss characteristics of short-distance transmission scenarios.

[0042] The LED is an AlInGaP miniature red-orange LED. The light intensity balance is achieved by adjusting the operating current of each diode. The average output pulse width is 2.4ns, the repetition frequency is 10MHz, and the average number of photons per pulse in the signal state and the decoy state are 0.3 and 0.1, respectively, ensuring system safety.

[0043] The narrowband filters of the transmitting and receiving modules are 632.8±3nm, used to suppress background light interference.

[0044] The transmitting module can be integrated into handheld devices such as mobile phones, and the receiving module can be integrated into fixed terminals such as ATMs. The handheld devices and fixed terminals use IrDA infrared or Bluetooth as a common channel to realize key "recharge" and transaction encryption. The effective transmission distance of the system is within 1 meter.

[0045] Example 2: Three-dimensional schematic diagram of the optical module (as shown below) Figure 3 As shown, the working process is as follows: The transmitting module randomly lights one LED in the LED array through the driving circuit to emit a light pulse signal. The LED is an AlInGaP miniature red-orange LED. The light intensity balance is achieved by adjusting the operating current of each diode. The average output pulse width is 2.4ns, the repetition frequency is 10MHz, and the average number of photons per pulse in the signal state and the decoy state are 0.3 and 0.1, respectively.

[0046] Since a polarizer is attached to the light-emitting surface of each LED, with polarization directions of H (0°), D (45°), V (90°), and A (135°), the light beams emitted by the four LEDs can generate four corresponding polarization states H, D, V, and A after passing through the polarizers. Then, they are combined into a beam by the holographic diffraction grating HDG1, and this beam contains polarization-coded quantum state light pulses.

[0047] The holographic diffraction grating is a 2×2 diffraction grating that needs to achieve two-dimensional orthogonal beam splitting (e.g., horizontal + vertical direction, corresponding to ±1 order × ±1 order, a total of 4 beams). The grating needs to be designed as a two-dimensional periodic structure (e.g., cross-shaped or square lattice periodicity). The grating constants of the two orthogonal directions need to be matched to ensure that the 4 beams of light are symmetrically emitted along the positive and negative directions of the X and Y axes, thereby achieving uniform distribution of the incident light in four directions.

[0048] Although the optical path achieves beam combining through a diffraction grating, since only one LED is lit at a time, only one LED's light signal will appear in the beam combining optical path, which is a polarization state.

[0049] The combined optical signal passes through a narrow-bandwidth filter F1 and a collimating lens to generate a parallel beam that is then emitted into the free-space channel.

[0050] In the receiving module, the polarization-coded quantum state light pulses are focused by a focusing lens, and background noise is filtered out by a narrowband filter F2. Then, the beam is split into four paths by an HDG2, with each path entering an APD (Optical Pointer) with polarization directions of H, D, V, or A, enabling random basis selection and polarization state measurement. Since each polarization-coded quantum state has an equal probability of entering all four optical paths through the diffraction grating, the system's polarization-coded BB84 protocol has an efficiency of 25%, making it suitable for low-loss short-distance transmission scenarios.

[0051] After the transmitting and receiving modules transmit quantum signals in free space, they transmit classical information through public channels such as the Internet, IrDA infrared, or Bluetooth, including basis matching, error correction, and privacy amplification, and complete key generation based on the BB84 protocol.

[0052] 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; and the privacy amplification module uses a security key rate formula to remove eavesdropping information and ensure key security.

[0053] Based on the principles and embodiments of this invention, it can be seen that this invention uses commercially available components to replace customized components, significantly reducing hardware costs and solving the problem of high prices in existing systems; it simplifies the optical structure through holographic diffraction gratings, and the transmitting and receiving modules are compact and can be integrated into handheld devices, meeting the portability requirements of consumer applications; through narrowband filtering, temperature control, and dynamic gate width adjustment, it achieves stable operation under shaded and sunlight conditions, expanding application scenarios; it is suitable for consumer scenarios such as ATM transactions and online payments, and achieves continuous security through periodic key "recharge," promoting the civilian application of quantum encryption technology.

Claims

1. A miniaturized quantum key distribution system, characterized in that, The system includes a transmitting module Alice and a receiving module Bob. The transmitting and receiving modules transmit quantum signals through free space and complete classical communication through a common channel. The system generates and updates a shared key based on the polarization coding BB84 protocol. The transmitting module includes an LED array, a driving circuit, and a beam combining and collimating module. The LED array contains four LEDs, with a polarizer attached to the light-emitting surface of each LED. The polarization directions are H (0°), D (45°), V (90°), and A (135°), respectively, to generate the corresponding four polarization states. The driving circuit is used to control each LED to emit pulse light of two intensities, which are used to generate a signal state and a decoy state, respectively. The beam combining and collimating module includes a diffraction grating, a filter, and a collimating lens; A diffraction grating is used to combine the beams generated by four LEDs into a single beam. Filters are used to filter the combined beam into a narrow linewidth optical signal; Collimating lenses are used to collimate light beams, enabling the transmission of quantum signal beams into free-space channels. The receiving module includes a focusing and splitting module, a single-photon detection array module, and a data acquisition and processing circuit. The focusing and beam-splitting module includes a focusing lens, a filter, and a diffraction grating; A focusing lens is used to receive light beams transmitted through a free-space channel, thereby converging the light beams. The filter is used to filter out background light noise; A diffraction grating is used to uniformly split a filtered beam into four spatially separated beams. The single-photon detection array module contains four avalanche photodiodes (APDs). A polarizer is attached to the front of each APD photosensitive surface, with polarization directions of H (0°), D (45°), V (90°), and A (135°), respectively, to detect the polarization state of the four beams. The acquisition and processing circuit is used to acquire and process the detection counts generated by the four APDs.

2. The miniaturized quantum key distribution system according to claim 1, characterized in that, The system also includes supporting software, which includes a synchronization calibration module, an error correction module, and a privacy amplification module. The synchronization calibration module determines the transmission start point by searching for abrupt changes in the time stamp frequency, achieves clock synchronization based on a 200ns pulse period, and completes precise time alignment through random subset correlation analysis. The error correction module uses the LDPC algorithm to complete one-way error correction by sending error correction checksums through the transmitter. The privacy amplification module determines the compression ratio based on the security key rate formula, removes potential eavesdropping information, and optimizes key security.

3. The miniaturized quantum key distribution system according to claim 2, characterized in that, Both the transmitting and receiving modules use Dammann gratings for their diffraction. The Dammann gratings divide the incident beam into a 1×4 linear array optical path to achieve random basis selection. The polarization coding BB84 protocol has an efficiency of 25% and is adapted to the low-loss characteristics of short-distance transmission scenarios.

4. The miniaturized quantum key distribution system according to claim 2, characterized in that, Both the transmitting and receiving modules employ holographic diffraction gratings in their optical components. These gratings divide the incident beam into a 2×2 matrix optical path, enabling random basis selection. The polarization coding BB84 protocol has an efficiency of 25%, adapting to the low-loss characteristics of short-distance transmission scenarios.

5. The miniaturized quantum key distribution system according to claim 3, characterized in that, The LED is an AlInGaP miniature red-orange LED. The light intensity balance is achieved by adjusting the operating current of each diode. The average output pulse width is 2.4ns, the repetition frequency is 10MHz, and the average number of photons per pulse in the signal state and the decoy state are 0.3 and 0.1, respectively.

6. The miniaturized quantum key distribution system according to claim 4, characterized in that, The narrowband filters of the transmitting and receiving modules are 632.8±3nm, used to suppress background light interference.

7. The miniaturized quantum key distribution system according to claim 1, characterized in that, The transmitting module is integrated into the handheld device, and the receiving module is integrated into the fixed terminal. The handheld device and the fixed terminal use IrDA infrared or Bluetooth as a common 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 described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Initialization, the transmitter and receiver share the initial key; S2: Quantum transmission, the transmitter generates a random bit string, controls the corresponding polarization state of the LED to emit photon pulses, the receiver selects the measurement basis vector through a grating, and the single photon detection array records the photon arrival time and polarization information; S3: Basis vector comparison. The receiver informs the transmitter of the measured basis vectors through a common channel. The transmitter feeds back the bit positions corresponding to the correct basis vectors. Both parties filter to obtain the original key. S4: Synchronization and error correction. Clock and data alignment is achieved through a synchronization calibration module, and error correction is completed using the LDPC algorithm. S5: Privacy enhancement, removal of potential eavesdropping information, and generation of the final security key; S6: Key update, repeat steps S2-S5 to achieve periodic "recharge" of the key.

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