WO2020135786A1 - 一种实时跟踪补偿的oam测量设备无关量子密钥分发系统及方法 - Google Patents

一种实时跟踪补偿的oam测量设备无关量子密钥分发系统及方法 Download PDF

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WO2020135786A1
WO2020135786A1 PCT/CN2019/129490 CN2019129490W WO2020135786A1 WO 2020135786 A1 WO2020135786 A1 WO 2020135786A1 CN 2019129490 W CN2019129490 W CN 2019129490W WO 2020135786 A1 WO2020135786 A1 WO 2020135786A1
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beam splitter
user
bob
alice
real
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PCT/CN2019/129490
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English (en)
French (fr)
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郭邦红
何翼龙
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华南师范大学
广东尤科泊得科技发展有限公司
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Priority to JP2021538487A priority Critical patent/JP7177419B2/ja
Priority to KR1020217024121A priority patent/KR20210135219A/ko
Publication of WO2020135786A1 publication Critical patent/WO2020135786A1/zh
Priority to US17/361,387 priority patent/US20220029798A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
    • G02B27/0068—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration having means for controlling the degree of correction, e.g. using phase modulators, movable elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/112—Line-of-sight transmission over an extended range
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/54—Intensity modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/614—Coherent receivers comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/70—Photonic quantum communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L63/00—Network architectures or network communication protocols for network security
    • H04L63/14—Network architectures or network communication protocols for network security for detecting or protecting against malicious traffic
    • H04L63/1408—Network architectures or network communication protocols for network security for detecting or protecting against malicious traffic by monitoring network traffic
    • H04L63/1416—Event detection, e.g. attack signature detection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L63/00—Network architectures or network communication protocols for network security
    • H04L63/14—Network architectures or network communication protocols for network security for detecting or protecting against malicious traffic
    • H04L63/1441—Countermeasures against malicious traffic
    • H04L63/145—Countermeasures against malicious traffic the attack involving the propagation of malware through the network, e.g. viruses, trojans or worms
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/0008—Synchronisation information channels, e.g. clock distribution lines
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/0075—Arrangements for synchronising receiver with transmitter with photonic or optical means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/32—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials
    • H04L9/3215—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials using a plurality of channels

Definitions

  • the invention belongs to the technical field of quantum information and optical communication, and relates to a real-time tracking and compensation OAM measurement equipment irrelevant quantum key distribution system and method.
  • QKD Quantum Key Distribution
  • DI-QKD Device-independent Quantum Key Distribution
  • the security of DI-QKD does not depend on the characteristics of the device, which means that even if the device is not ideal, quantum hackers cannot use this defect to steal any information. Therefore, DI-QKD can always guarantee unconditional theoretical security.
  • the realization of DI-QKD is a difficult challenge, which requires perfect Bell state measurement and very efficient single photon detection technology, which is difficult to achieve with existing technology.
  • MDI-QKD Measurement Device Independent Quantum Key Distribution
  • the protocol introduced a decoy state scheme, using phase randomization to make the photon state into a photon number mixed state, which can prevent photon number splitting attacks.
  • MDI-QKD implementation schemes such as polarization coding schemes, phase coding schemes and time-bin coding schemes.
  • the MDI-QKD protocol solves all the vulnerabilities in the measurement end of the quantum key system at one time, but there are still vulnerabilities affecting the security in the light source part, modulation part and side channel part.
  • the traditional MDI-QKD (patent: CN106712940) combined with the decoy state introduces a weak coherent light source, which reduces the light source requirements of the MDI-QKD system, but both users use separate light sources, and the spectrum of the emitted light is inconsistent. Using this difference, quantum hackers can distinguish the source of the photon, and then steal the user's key information.
  • the measurement unit of the system uses a pulse laser, polarization beam splitter and beam splitter to The pulse is transmitted to the user terminal.
  • the user end uses charge coupled device (CCD) and beam splitter for monitoring and synchronization, and deforms the mirror for phase distortion compensation.
  • CCD charge coupled device
  • the intensity modulator and spatial light modulator randomly generate deceptive states with orbital angular momentum of less than 1 photon.
  • Signal state photons are sent to the middle measuring unit.
  • the measurement unit measures the photon state sent by the user and publishes the measurement results. The user generates a consistent key locally after the process of base comparison and key negotiation according to the measured response.
  • Another object of the invention is to provide a real-time tracking and compensation OAM measurement equipment independent quantum key distribution method, which can naturally achieve spectral pattern matching, and can easily achieve real-time channel monitoring, pulse intensity and atmospheric turbulence intensity measurement And clock synchronization.
  • a real-time tracking-compensated OAM measurement equipment-independent quantum key distribution system including: user terminal Alice, user terminal Bob and measurement unit;
  • the user terminal Alice and the user terminal Bob are connected to the measurement unit through a quantum channel, where:
  • the measurement unit includes: first and second telescope systems, first 50:50 beam splitter, first polarization beam splitter, pulse laser, first to fourth mirrors, first and second MZ interferometers and first To the fourth single-photon detector; when the pulse laser of the measuring unit emits a fundamental mode Gaussian beam, it is first filtered by the first polarization beam splitter to reflect the fundamental mode Gaussian light with a vertical polarization mode to the first 50:
  • the 50 beam splitter is divided into two beams, which are respectively reflected by the first mirror and the second mirror, and finally collimated by the first telescope system and the second telescope system, and sent to the user terminal Alice and the user terminal through quantum channels, respectively.
  • Bob when the pulse laser of the measuring unit emits a fundamental mode Gaussian beam, it is first filtered by the first polarization beam splitter to reflect the fundamental mode Gaussian light with a vertical polarization mode to the first 50:
  • the 50 beam splitter is divided into two beams, which are respectively reflected by the first mirror and
  • the user terminal Alice and the user terminal Bob respectively send the strong pulse laser from the measurement unit to the channel unit for real-time monitoring of the channel environment, phase distortion compensation, and orbital angular momentum encoding, and then send it to the test unit;
  • the first telescope system and the second telescope system of the measurement unit receive the signal pulses from the user terminal Alice and the user terminal Bob, this signal pulse first reflects through the first mirror and the second mirror, and then Interference occurs at the third 50:50 beam splitter.
  • the interfering pulses are reflected by the third mirror and the fourth mirror, respectively, and enter the first MZ interferometer and the second MZ interferometer, respectively, and are interfered by the first MZ.
  • the instrument After the instrument is separated from the second MZ interferometer, it enters the first to fourth single-photon detectors to cause a response and output the measurement result; the user Alice and the user Bob follow the process of base comparison and key negotiation according to the measured response After that, a consistent key is generated locally.
  • the user end Alice includes: a third telescope system, a first narrow-band filter, a first beam splitter, a first charge coupled element (CCD), a first delayer, a second polarization beam splitter, a A deformable mirror, a second deformable mirror, a first half-wave plate, a first spatial light modulator and a first intensity modulator;
  • a third telescope system a first narrow-band filter, a first beam splitter, a first charge coupled element (CCD), a first delayer, a second polarization beam splitter, a A deformable mirror, a second deformable mirror, a first half-wave plate, a first spatial light modulator and a first intensity modulator;
  • CCD charge coupled element
  • the user end Bob includes: a fourth telescope system, a second narrow-band filter, a second beam splitter, a second charge-coupled element (CCD), a second delayer, a third polarization beam splitter, and a third deformable mirror , A fourth deformable mirror, a second half-wave plate, a second spatial light modulator and a second intensity modulator.
  • a fourth telescope system a second narrow-band filter, a second beam splitter, a second charge-coupled element (CCD), a second delayer, a third polarization beam splitter, and a third deformable mirror , A fourth deformable mirror, a second half-wave plate, a second spatial light modulator and a second intensity modulator.
  • CCD charge-coupled element
  • the first and second spatial light modulators and the first and second intensity modulators randomly modulate pulses;
  • the first and second spatial light modulators encode the orbital angular momentum
  • four states are randomly selected Encode one of them; where ⁇
  • both the third telescope system and the fourth telescope system include two confocal convex lenses for controlling the scale of the laser pulse and the far-field divergence angle of the laser beam; the first narrowband filter and the first Two narrow-band filters are used to filter out the light outside the communication band; the first beam splitter and the second beam splitter divide the incident pulsed laser into two strong and weak paths, which are a stronger upper branch and a weaker lower branch, respectively.
  • the first charge-coupled element (CCD) and the second charge-coupled element (CCD) are used to monitor the intensity of the laser pulse and the wavefront phase distortion caused by atmospheric turbulence in real time to compensate for clock synchronization and phase distortion of the lower branch Provide reference information; the second polarizing beam splitter and third polarizing beam splitter transmit horizontally polarized light and reflect vertical polarized light; the first deformable mirror, second deformable mirror, third deformable mirror and fourth deformable The mirror is also called wavefront corrector, which can change the phase structure of the incident wavefront according to
  • the third telescope system at the user end Alice receives the pulsed laser from the measurement unit, then filters the light outside the communication band through the first narrowband filter, and then splits the incident pulsed laser into a strong beam through the first beam splitter
  • the two weak paths are the stronger upper branch and the weaker lower branch;
  • the upper branch is connected to the first charge-coupled element for real-time monitoring of the intensity of the laser pulse and the wavefront phase distortion caused by atmospheric turbulence, Reference information is provided for clock synchronization and phase distortion compensation;
  • the lower branch is used to modulate the pulse loading phase information, which is connected to the first delayer, the second polarization beam splitter, the first deformable mirror, the first half-wave plate, the first A spatial light modulator, a first intensity modulator and a second deformable mirror;
  • the pulsed laser light separated into the lower branch first enters the first delayer, and after a certain time delay enters the second polarization beam splitter, the second polarization
  • the beam splitter reflects the pulsed laser
  • the first deformed mirror performs distortion compensation on the wavefront phase according to the reference information provided by the upper branch; the compensated pulsed laser will be reflected to the first half-wave plate, the first The half-wave plate reverses its polarization state by 90 degrees and enters the first spatial light modulator.
  • the first spatial light modulator encodes the orbital angular momentum of the pulse; the encoded pulse is modulated into different average photons by the first intensity modulator
  • the orbital angular momentum signal state and decoy state of several intensities are phase-corrected by the second deformable mirror, transmitted from the second polarizing beam splitter, passing through the first delayer, the first beam splitter and the first narrow-band filter Three telescope systems; finally the third telescope system collimates the signal state and the decoy state and sends it to the measurement unit.
  • Bob's fourth telescope system at the user end receives the pulsed laser light from the measurement unit, then filters the light outside the communication band through a second narrowband filter, and then splits the incident pulsed laser light into a strong beam through a second beam splitter
  • the weaker two paths are the stronger upper branch and the weaker lower branch;
  • the upper branch is connected to the second charge-coupled element for real-time monitoring of the intensity of the laser pulse and the wavefront phase distortion caused by atmospheric turbulence, is Reference information is provided for clock synchronization and phase distortion compensation;
  • the lower branch is used to modulate the pulse to load phase information, which is connected to the second delayer, the third polarization beam splitter, the third deformable mirror, the second half-wave plate, the first Two spatial light modulators and a second intensity modulator;
  • the pulse laser separated into the lower branch first enters the second delayer, and after a certain delay, enters the third polarization beam splitter, which will pulse The laser is reflected to the third deformable mirror.
  • the third deformable mirror performs distortion compensation on the wavefront phase according to the reference information provided by the upper branch.
  • the compensated pulsed laser will be reflected to the second half-wave plate. After the polarization state is reversed by 90 degrees, it enters the second spatial light modulator.
  • the second spatial light modulator encodes the orbital angular momentum of the pulse.
  • the encoded pulse is modulated by the second intensity modulator into an orbital angle of different average photon number intensity
  • the momentum signal state and decoy state are phase-corrected by the fourth deformable mirror, transmitted from the third polarization beam splitter, and reach the fourth telescope system through the second delay, second beam splitter and second narrow-band filter; finally The fourth telescope system collimates the signal state and the decoy state and sends it to the measurement unit.
  • the first charge coupled element (CCD) and the second charge coupled element (CCD) are used to monitor the intensity of the laser pulse and the wavefront phase distortion caused by atmospheric turbulence in real time, and provide reference information for clock synchronization and phase distortion compensation
  • the first, second deformable mirrors, and third and fourth deformable mirrors perform distortion compensation on the wavefront phase according to the reference information provided by the first charge-coupled element (CCD) and the second charge-coupled element (CCD), respectively.
  • the first and third deformable mirrors perform distortion compensation on the phase of the wavefront according to the phase distortion information provided by the upper branch, and the compensated laser returns to a state without phase distortion; the second and fourth deformable mirrors provide The phase distortion information corrects the wavefront phase so that the incident light produces a conjugate phase that is conjugate to the distortion phase.
  • the phase distortion caused by the environment such as atmospheric turbulence will be cancelled and the beam recovered To the state without phase distortion.
  • the first MZ interferometer includes a second 50:50 beam splitter, a third 50:50 beam splitter, a fifth mirror, a sixth mirror, a first Duff prism and a second Duff prism;
  • the second MZ interferometer includes a fourth 50:50 beam splitter, a fifth 50:50 beam splitter, a seventh mirror, an eighth mirror, a third Duff prism, and a fourth Duff prism.
  • the quantum channel is a free space channel or a fiber channel.
  • the first 50:50 beam splitter of the measuring unit erases the photon state path information so that the photon State is indistinguishable. Due to the HOM effect, the same photon state will be output from the same output port of the first 50:50 beam splitter, and different photon states will be output independently from each other.
  • the signal pulse is output from the upper and lower two ports of the first 50:50 beam splitter, reflected by the mirror, and enters the first MZ interferometer And the second MZ interferometer.
  • the effect of the first M-Z interferometer on input photons is as follows:
  • the state output by the M-Z interferometer is finally detected by the single photon detector and responds to the output result.
  • the response of the measurement unit is as follows:
  • the response of the first single photon detector or the third single photon detector is called “A response”, which means that the orbital angular momentum order l of the response photon is odd; the second single photon detector or the first The four single-photon detector response is called “B response”, which means that the orbital angular momentum order l of the responding photon is even; it can be seen that only "absence of AB response" can be coded under different interferometers.
  • the user terminal Alice and the user terminal Bob generate a consistent key locally based on the response of the measurement unit, after base comparison and key negotiation.
  • a real-time tracking-compensated OAM measurement device-independent quantum key distribution method is applied to a real-time tracking-compensated OAM measurement device-independent quantum key distribution system as described above.
  • the method includes the following steps:
  • the measuring unit emits strong laser pulses to user Alice and user Bob.
  • User Alice and user Bob use the pulses to perform clock synchronization and anti-eavesdropping monitoring, and at the same time estimate based on the degree of dispersion of the incident Gaussian pulse spot Atmospheric turbulence intensity; when the atmospheric turbulence intensity is below the threshold and no eavesdropping is monitored, the next step is performed;
  • Bit coding Alice and Bob at the user end randomly select the X or Y basis for information encoding, and use the spatial light modulator to randomly encode the bit information into 4 orbital angular momentum states, and then transmit it to the intermediate measurement Unit; where X base is ⁇
  • the measurement unit performs the measurement operation, and then announces which bits have been successfully detected, and announces its measurement results; the user Alice and the user Bob retain the above data, and discard the data of other code bits;
  • Base pairing User Alice and user Bob perform base pairing through a common channel, select the bits prepared under the same base, and negotiate bit flipping to ensure the consistency of the bits of both parties in the communication; after completing these operations, keep The data is used as the original key;
  • the user terminal Alice and the user terminal randomly select the orbital angular momentum state or the superposition state whose topological load is odd or even to encode, allowing the composition of any odd or even order orbital angular momentum state A group of mutually unbiased bases are encoded.
  • the user terminal of a real-time tracking and compensation OAM measurement device-independent quantum key distribution system uses two deformable mirrors and a CCD to form an adaptive optical system, which can track and monitor the phase distortion caused by atmospheric turbulence in real time and estimate the atmosphere The degree of turbulence and the distortion phase compensation in real time improve the anti-interference ability of the measurement equipment independent quantum key distribution system.
  • the pulse signals of both users are from the same laser, and their spectral modes are naturally the same, which has a very high guarantee during interferometric measurement.
  • Truth using this light source, you can easily implement real-time channel monitoring, prevent Trojan horse attacks, and easily synchronize clocks.
  • a real-time tracking-compensated OAM measurement device-independent quantum key distribution system and method of the present invention using photons with orbital angular momentum (OAM) as a carrier of information, capable of measuring without aligning the base reference system
  • OAM orbital angular momentum
  • the device-independent quantum key distribution improves the key rate; and the orbital angular momentum state has the characteristics of infinite dimensions, which makes the present invention have a very strong expansion ability, can be easily combined with the orbital angular momentum multiplexing/separation device, and increase the channel capacity ;
  • FIG. 1 is a structural block diagram of a measurement unit of the present invention
  • FIG. 2 is a structural block diagram of the user terminal Alice of the present invention
  • FIG. 3 is a structural block diagram of Bob of the user terminal of the present invention.
  • a real-time tracking and compensation OAM measurement device-independent quantum key distribution system includes: a user terminal Alice, a user terminal Bob and a measurement unit.
  • the user terminal Alice and the user terminal Bob are connected to the measurement unit through a quantum channel, where:
  • the quantum channel is a free-space channel or a fiber-optic channel.
  • a free-space channel is used as an example for description.
  • the measurement unit uses a pulsed laser to generate strong Gaussian pulses.
  • the Gaussian pulses are transmitted to the user end through the polarization beam splitter and beam splitter.
  • the user end uses charge-coupled components (CCD) and beam splitter for monitoring and synchronization.
  • CCD charge-coupled components
  • the deformable mirror performs phase distortion compensation on the distorted phase, and uses the intensity modulator and the spatial light modulator to randomly generate deceptive state and signal state photons with an orbital angular momentum of less than 1 photon number, and sends them to the intermediate measurement unit.
  • the measurement unit uses time The multiplexed single-photon detector measures the photon state sent by the user and publishes the measurement results. The user generates a consistent key locally after going through base comparison and negotiation processes based on the measured response.
  • the measurement unit includes: a first telescope system 301, a second telescope system 302, a first 50:50 beam splitter 305, a second 50:50 beam splitter 320, and a third 50:50 minute Beam splitter 325, fourth 50:50 beam splitter 330, fifth 50:50 beam splitter 335, first polarization beam splitter 306, pulse laser 307, first mirror 303, second mirror 304, third Mirror 308, fourth mirror 309, first MZ interferometer, second MZ interferometer, first single photon detector 326, second single photon detector 327, third single photon detector 336, and fourth single photon Probe 337.
  • the first telescope system 301 and the second telescope system 302 are mainly used for collimating light beams; the first polarization beam splitter 306 transmits horizontally polarized light and reflects vertically polarized light; and the pulse laser 307 serves as a pumping light source For pumping to generate fundamental mode Gaussian light;
  • the first MZ interferometer 340 includes a second 50:50 beam splitter 320, a third 50:50 beam splitter 325, a fifth mirror 321, and a sixth mirror 323, a first Duff prism 324 and a second Duff prism 322;
  • the second MZ interferometer 341 includes a fourth 50:50 beam splitter 330, a fifth 50:50 beam splitter 335, and a seventh reflector 331 ,
  • the first MZ interferometer 340 and the second MZ interferometer 341 are used to separate the orbital angular momentum order
  • the first Duff prism 324 when the relative angle of the first Duff prism 324 and the second Duff prism 322 in the two optical paths of the first MZ interferometer 340 is ⁇ /2, the first Duff prism 324.
  • the first single photon detector 326, the second single photon detector 327, the third single photon detector 336, and the fourth single photon detector 337 are used to detect single photon-level optical signals;
  • the user end Alice includes: a third telescope system 101, a first narrow-band filter 102, a first beam splitter 103, a first charge-coupled element (CCD) 104, and a first delay 105, The second polarization beam splitter 106, the first deformable mirror 107, the second deformable mirror 111, the first half-wave plate 108, the first spatial light modulator 109 and the first intensity modulator 110.
  • a third telescope system 101 a third telescope system 101, a first narrow-band filter 102, a first beam splitter 103, a first charge-coupled element (CCD) 104, and a first delay 105
  • CCD charge-coupled element
  • the client Bob includes: a fourth telescope system 201, a second narrow-band filter 202, a second beam splitter 203, a second charge-coupled element (CCD) 204, and a second delay 205, The third polarization beam splitter 206, the third deformable mirror 207, the fourth deformable mirror 211, the second half-wave plate 208, the second spatial light modulator 209, and the second intensity modulator 210.
  • CCD charge-coupled element
  • the third telescope system 101 and the fourth telescope system 201 each include two confocal convex lenses for controlling the scale of the laser pulse and the far-field divergence angle of the laser beam; the first narrowband filter 102 and the first The two narrow-band filters 202 are used to filter out the light outside the communication band; the first beam splitter 103 and the second beam splitter 203 divide the incident pulse laser into strong and weak paths, which are the stronger upper branch and the stronger Weak lower branch; the first charge-coupled element (CCD) 104 and the second charge-coupled element (CCD) 204 are used to monitor the intensity of the laser pulse and the wavefront phase distortion caused by atmospheric turbulence in real time, which is clock synchronization and down
  • the phase distortion compensation of the branch provides reference information; the second polarizing beam splitter 106 and the third polarizing beam splitter 206 transmit horizontally polarized light and reflect vertically polarized light; the first deformable mirror 107 and the second deformable mirror 111, the third deformable mirror 207 and
  • the pulse laser 307 of the measurement unit emits a fundamental mode Gaussian beam, which is first filtered by the first polarization beam splitter 306 to convert the polarization mode to vertically polarized fundamental mode Gaussian light Reflected to the first 50:50 beam splitter 305 and split into two beams, then collimated by the first telescope system 301 and the second telescope system 302 to control the divergence angle of the far field, and then sent to the user terminal Alice and the user through the quantum channel Bob
  • the third telescope system 101 of the user end Alice receives the pulsed laser light from the measurement unit, then passes through the first narrow-band filter 102 and the second narrow-band filter 202 to filter out the light outside the communication band, and then passes through
  • the first beam splitter 103 divides the incident pulsed laser into two strong and weak paths, namely a stronger upper branch and a weaker lower branch; the upper branch is connected to a first charge coupled element (CCD) 104 for Real-time monitoring of the intensity of the laser pulse and the wavefront phase distortion caused by atmospheric turbulence, providing reference information for clock synchronization and phase distortion compensation; the lower branch is used to modulate the pulse loading phase information, which is connected to the first delay 105, A two-polarization beam splitter 106, a first deformable mirror 107, a first half-wave plate 108, a first spatial light modulator 109 and a first intensity modulator 110, and a second deformable mirror 111.
  • CCD charge coupled element
  • the pulsed laser beam separated into the lower branch first enters the first delayer 105 and enters the second polarization beam splitter 106 after a certain time delay.
  • the second polarization beam splitter 106 reflects the pulsed laser beam to the first deformable mirror 107.
  • the first deformable mirror 107 performs distortion compensation on the wavefront phase according to the reference information provided by the upper branch, the compensated pulsed laser light will be reflected to the first half-wave plate 108, and the first half-wave plate 108 reverses its polarization state by 90 degrees
  • the first spatial light modulator 109 encodes the orbital angular momentum of the pulse.
  • the encoded pulse is modulated by the first intensity modulator 111 into orbital angular momentum signals of different average photon number intensities State and decoy state, through the second deformable mirror 111 for phase correction, transmitted from the second polarization beam splitter 106, through the first delay 105, the first beam splitter 103 and the first narrowband filter 102 to reach the third telescope
  • the system 101 and the third telescope system 101 collimate the signal state and the decoy state and send it to the measurement unit.
  • Bob’s fourth telescope system 201 receives the pulsed laser light from the measurement unit, then passes the second narrow-band filter 202 to filter out other light than the communication band, and then passes through the second beam splitter 203
  • the incident pulse laser is divided into two strong and weak paths, namely a stronger upper branch and a weaker lower branch; the upper branch is connected to a second charge coupled element (CCD) 204 for real-time monitoring of the intensity of the laser pulse And the wavefront phase distortion caused by atmospheric turbulence, providing reference information for clock synchronization and phase distortion compensation; the lower branch is used to modulate the pulse loading phase information, and is connected to the second delayer 205 and the third polarization beam splitter 206 in sequence , A third deformable mirror 207, a second half-wave plate 208, a second spatial light modulator 209 and a second intensity modulator 210, and a fourth deformable mirror 211.
  • CCD charge coupled element
  • the pulse laser separated into the lower branch first enters the second delay 205, and after a certain delay, enters the third polarization beam splitter 206, and the third polarization beam splitter 206 reflects the pulse laser to the third deformable mirror 207.
  • the third deformable mirror 207 performs distortion compensation on the wavefront phase according to the reference information provided by the upper branch, the compensated pulsed laser light will be reflected to the second half-wave plate 208, and the second half-wave plate 208 will reverse its polarization state by 90 degrees
  • the first spatial light modulator 209 encodes the orbital angular momentum of the pulse.
  • the encoded pulse is modulated by the second intensity modulator 210 into orbital angular momentum signals of different average photon number intensities State and decoy state, undergo phase correction through the fourth deformable mirror 211, transmit from the third polarization beam splitter 206, reach the fourth telescope through the second delay 205, the second beam splitter 203, and the second narrowband filter 202
  • the system 201 and the fourth telescope system 201 collimate the signal state and the decoy state and send it to the measurement unit.
  • first spatial light modulator 109 and the second spatial light modulator 209 encode the orbital angular momentum
  • four states are randomly selected One of them.
  • e> ⁇ is X group; Is Y-based;
  • e> represent orbital angular momentum states with odd and even topological loads, respectively.
  • the first telescope system 301 and the second telescope system 302 of the measurement unit respectively receive signal pulses from the user terminal Alice and the user terminal Bob.
  • This signal pulse is first reflected by the first mirror 303 and the second mirror 304 , Interfering at the first 50:50 beam splitter 305.
  • the first 50:50 beam splitter 305 erases the photon state path information, making the photon states indistinguishable. Due to the HOM effect, the same photon state will be output from the same output port of the first 50:50 beam splitter 305, and different photon states will be output independently from each other.
  • the signal pulse is output from the upper and lower two ports of the first 50:50 beam splitter 305, passes through the reflection of the third mirror 308 and the fourth mirror 309, and enters the first MZ interferometer 340 and the second MZ interferometer 341.
  • the effect of the first M-Z interferometer 340 on the input photon is as follows:
  • the above formula indicates that the probability of the photon output from the transmission end and the reflection end of the second 50:50 beam splitter 320 is 50%, where i represents the half-wave phase shift caused by the output of the reflection end.
  • the state output by the M-Z interferometer is finally detected by the single photon detector and responds to the output result.
  • the response of the measurement unit is as follows:
  • the first single photon detector 326 or the third single photon detector 336 responds is called “A response", indicating that the orbital angular momentum order l of the responding photon is odd;
  • the second single photon The detector 327 or the fourth single-photon detector 337 is called “B response” when responding, which means that the orbital angular momentum order l of the responding photon is even; it can be seen that only “under different interferometers, the AB response" can become code.
  • the user terminal Alice and the user terminal Bob generate a consistent key locally based on the response of the measurement unit, after base comparison and key negotiation.
  • an orbital angular momentum-based measurement device-independent quantum key distribution method which is applied to an orbital angular momentum-based measurement device-independent quantum key distribution system as described above, the method includes The following steps:
  • the measuring unit emits strong laser pulses to user Alice and user Bob.
  • User Alice and user Bob use the pulses to perform clock synchronization and anti-eavesdropping monitoring, and at the same time estimate based on the degree of dispersion of the incident Gaussian pulse spot Atmospheric turbulence intensity; when the atmospheric turbulence intensity is below the threshold and no eavesdropping is monitored, the next step is performed;
  • Bit coding Alice and Bob at the user end randomly select the X or Y basis for information encoding, and use the spatial light modulator to randomly encode the bit information into 4 orbital angular momentum states, and then transmit it to the intermediate measurement Unit; where X base is ⁇
  • the measurement unit performs the measurement operation, and then announces which bits have been successfully detected, and announces its measurement results; the user Alice and the user Bob retain the above data, and discard the data of other code bits;
  • Base pairing User Alice and user Bob perform base pairing through a common channel, select the bits prepared under the same base, and negotiate bit flipping to ensure the consistency of the bits of both parties in the communication; after completing these operations, keep The data is used as the original key;

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Abstract

本发明公开了一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统及方法，包括用户端Alice，用户端Bob和测量单元；用户端Alice和用户端Bob利用来自测量单元的强脉冲激光实现信道环境实时监测以及相位畸变补偿；测量单元采用达夫棱镜组成的M-Z干涉仪实现奇/偶轨道角动量阶数光子的分离，可对具有轨道角动量的光子进行Bell态的测量；本发明实现了基于轨道角动量的测量设备无关量子密钥分发，用户利用轨道角动量态进行编码，具有稳定性好，成码率高，扩展性强的特点。

Description

一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统及方法 技术领域
本发明属于量子信息与光通信技术领域，涉及一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统及方法。
背景技术
自1984年第一个量子密钥分发协议问世以来，量子密钥分发(Quantum Key Distribution，QKD)一直被认为是量子信息科学中一项非常可行的技术。QKD允许两个远程用户(Alice和bob)根据量子物理定律生成具有理论上无条件安全的密钥。然而，在现实环境下，理想模型和实际设备之间存在差距。例如，一个理想的QKD协议需要一个理想的单光子源和探测器来保证其安全性。以目前的技术来看，理想的单光子源和探测器是难以实现的。这些器件的不理想使得QKD系统容易受到各种攻击。例如，光子数分裂攻击、时移攻击和致盲攻击等。
为了克服这些困难，人们提出了设备无关的量子密钥分发的概念(Device independent Quantum Key Distribution，DI-QKD)。DI-QKD的安全性不取决于设备的特性，这意味着即使设备不理想，量子黑客也无法利用这一缺陷窃取到任何信息。因此，DI-QKD总是能保证无条件的理论安全。然而，DI-QKD的实现是一项艰难的挑战，它需要完美的Bell态测量和非常高效率的单光子检测技术，这是现有技术难以达到的。但最近提出的测量设备无关的量子密钥分发协议(Measurment Device Independent Quantum Key Distribution，MDI-QKD)，缩短了DI-QKD与实用化的距离，做到了部分QKD设备无关的量子通信，消除了所有与探测相关的安全漏洞。同时，该协议引入了诱骗态的方案，利用相位随机化使得光子态转化为光子数的混态，可很好预防光子数分裂攻击。人们已研发出多种MDI-QKD的实现方案，如偏振编码的方案、相位编码的方案和time-bin编码的方案等。
MDI-QKD协议一次性解决了量子密钥系统测量端的所有漏洞问题，但在光源部分、调制部分和边信道部分等依旧存在影响安全的漏洞。如，传统MDI-QKD(专利：CN106712940)结合诱骗态引入了弱相干光源，降低了MDI-QKD系统对光源的要求，但用户双方使用的是 各自独立的光源，各自发射光的光谱不一致。而利用这一差异，量子黑客可以区分光子的来源，进而窃取用户的密钥信息。针对光谱不一致的问题，人们提出了即插即用的MDI-QKD(文献：Liu,C.Q.at al.(2016).Polarization-Encoding-Based Measurement-Device-Independent Quantum Key Distribution with a Single Untrusted Source.Chinese Physics Letters,33(10).)，但其调制方案存在测量基参考系不完全匹配的问题，增加了误码率。对此，近期人们提出的基于轨道角动量态(OAM)编码的MDI-QKD方案(文献：Wang L,Zhao S M,Gong L Y,et al.Free-space measurement-device-independent quantum-key-distribution protocol using decoy states with orbital angular momentum[J].Chinese Physics B,2015,24(12):120307.)，解决了参考系不完全匹配的问题，减小了误码率，但存在光谱不一致的问题，并且针对信道环境也没有很好的监测方法和信号补偿方法，因此，弱信号量子密钥分发系统性能极容易受到外界环境的影响。
发明内容
本发明的目的在于克服上述现有技术的不足，提供一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，该系统的测量单元利用脉冲激光器、偏振分束器和分束器将强光脉冲传输至用户端。用户端利用电荷耦合元件(CCD)和分束器进行监测与同步，通过变形镜进行相位畸变补偿，利用强度调制器和空间光调制器随机产生光子数小于1的具有轨道角动量的诱骗态和信号态光子，发送到中间的测量单元。测量单元对用户发送的光子态进行测量，并公布测量结果，用户根据测量的响应情况，经过基的对比和密钥协商等过程后，在本地产生一致的密钥。
发明的又一目的是提出一种实时跟踪补偿的OAM测量设备无关量子密钥分发方法，可自然地实现光谱模式的匹配，同时可方便地实现实时的信道监测、脉冲强度和大气湍流强度的测量以及时钟同步等。
为达到上述发明目的，本发明的技术方案实现如下：
一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，包括：用户端Alice、用户端Bob和测量单元；
所述用户端Alice和用户端Bob通过量子信道与测量单元连接，其中：
所述测量单元包括：第一、二望远镜系统，第一50:50分束器，第一偏振分束器，脉冲激光器，第一至第四反射镜，第一、二M-Z干涉仪和第一至第四单光子探测器；所述测量 单元的脉冲激光器发出基模高斯光束时，先经过第一偏振分束器的筛选将偏振模式为竖直偏振的基模高斯光反射至第一50:50分束器分成两束，再分别经过第一反射镜和第二反射镜反射，最后通过所述第一望远镜系统和第二望远镜系统准直，通过量子信道分别发往用户端Alice和用户端Bob；
用户端Alice和用户端Bob分别对来自测量单元的强脉冲激光实现信道环境实时监测、相位畸变补偿以及轨道角动量的编码后发往测试单元；
所述测量单元的第一望远镜系统和第二望远镜系统分别接收来自用户端Alice和用户端Bob的信号脉冲时，此信号脉冲先经过所述第一反射镜和第二反射镜的反射，然后在第三50:50分束器处进行干涉，干涉后的脉冲分别经过第三反射镜和第四反射镜的反射，分别进入到第一M-Z干涉仪和第二M-Z干涉仪，被第一M-Z干涉仪和第二M-Z干涉仪分离后，进入第一至第四单光子探测器造成响应，输出测量结果；用户端Alice和用户端Bob根据测量的响应情况，经过基的对比和密钥协商等过程后，在本地产生一致的密钥。
优选地，所述用户端Alice包括：第三望远镜系统，第一窄带滤波器，第一分束器，第一电荷耦合元件(CCD)，第一延时器，第二偏振分束器，第一变形镜，第二变形镜，第一半波片，第一空间光调制器和第一强度调制器；
所述用户端Bob包括：第四望远镜系统，第二窄带滤波器，第二分束器，第二电荷耦合元件(CCD)，第二延时器，第三偏振分束器，第三变形镜，第四变形镜，第二半波片，第二空间光调制器和第二强度调制器。
优选地，所述第一、二空间光调制器与所述第一、二强度调制器对脉冲进行随机调制；
所述第一、二空间光调制器对轨道角动量进行编码时，随机选择四个态
Figure PCTCN2019129490-appb-000001
中的一个进行编码；其中{|o>，|e>}为X基；
Figure PCTCN2019129490-appb-000002
为Y基；|o>和
Figure PCTCN2019129490-appb-000003
代表比特0；|e>和
Figure PCTCN2019129490-appb-000004
代表比特1；|o>和|e>分别代表拓扑荷数为奇数和偶数的轨道角动量态；所述第一、二强度调制器精确产生不同平均光子数强度的诱骗态和信号态光子。
优选地，所述第三望远镜系统和第四望远镜系统均包括两个共焦的凸透镜，用于控制激光脉冲的尺度大小，控制激光光束的远场发散角；所述第一窄带滤波器和第二窄带滤波器用于滤除通信波段以外的光；所述第一分束器和第二分束器将入射脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述第一电荷耦合元件(CCD)和第二电荷耦合 元件(CCD)用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及下支路的相位畸变补偿提供参考信息；所述第二偏振分束器和第三偏振分束器透过水平偏振光，反射垂直偏振光；所述第一变形镜、第二变形镜，第三变形镜和第四变形镜又称波前校正器，可根据相位畸变的参考信息，改变光波波前传输的光程或改变传输媒介的折射率来改变入射光波波前的相位结构，从而达到对光波波面相位进行补偿的目的；所述第一半波片、第二半波片的主截面与入射光偏振面呈45度放置，可将入射光的偏振方向旋转90度；所述第一空间光调制器、第二空间光调制器为纯相位型反射式液晶空间光调制器，是一种基于液晶分子电致双折射效应的有源数字光学器件，用于调制光束的轨道角动量；所述第一强度调制器、第二强度调制器可精确产生不同平均光子数强度的诱骗态和信号态光子。
优选地，所述用户端Alice的第三望远镜系统接收来自测量单元的脉冲激光，然后经过第一窄带滤波器滤除通信波段以外的光，再经过第一分束器将入射的脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述上支路连接第一电荷耦合元件用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息；所述下支路用于调制脉冲加载相位信息，依次连接第一延时器、第二偏振分束器、第一变形镜、第一半波片、第一空间光调制器、第一强度调制器和第二变形镜；分离到下支路的脉冲激光先进入第一延时器，经过一定的时延后进入第二偏振分束器，第二偏振分束器将脉冲激光反射至第一变形镜，第一变形镜根据上支路提供的参考信息对波前相位进行畸变补偿；补偿后的脉冲激光将被反射至第一半波片，第一半波片将其偏振态翻转90度后进入第一空间光调制器，第一空间光调制器对脉冲进行轨道角动量的编码；编码后的脉冲通过第一强度调制器被调制成不同平均光子数强度的轨道角动量信号态与诱骗态，经过第二变形镜进行相位校正，从第二偏振分束器透射，通过第一延时器、第一分束器和第一窄带滤波器到达第三望远镜系统；最后第三望远镜系统对信号态和诱骗态进行准直，发往测量单元。
优选地，所述用户端Bob的第四望远镜系统接收来自测量单元的脉冲激光，然后经过第二窄带滤波器滤除通信波段以外的光，再经过第二分束器将入射的脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述上支路连接第二电荷耦合元件用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息；所述下支路用于调制脉冲加载相位信息，依次连接第二延时器、第三偏振分束 器、第三变形镜、第二半波片、第二空间光调制器和第二强度调制器；分离到下支路的脉冲激光先进入第二延时器，经过一定的时延后进入第三偏振分束器，第三偏振分束器将脉冲激光反射至第三变形镜，第三变形镜根据上支路提供的参考信息对波前相位进行畸变补偿，补偿后的脉冲激光将被反射至第二半波片，第二半波片将其偏振态翻转90度后进入第二空间光调制器，第二空间光调制器对脉冲进行轨道角动量的编码，编码后的脉冲通过第二强度调制器被调制成不同平均光子数强度的轨道角动量信号态与诱骗态，经过第四变形镜进行相位校正，从第三偏振分束器透射，通过第二延时器、第二分束器和第二窄带滤波器到达第四望远镜系统；最后第四望远镜系统对信号态和诱骗态进行准直，发往测量单元。
优选地，所述第一电荷耦合元件(CCD)和第二电荷耦合元件(CCD)用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息，所述第一、二变形镜和第三、四变形镜分别根据所述第一电荷耦合元件(CCD)和第二电荷耦合元件(CCD)提供的参考信息对波前相位进行畸变补偿。优选地，第一、三变形镜根据上支路提供的相位畸变信息对波前相位进行畸变补偿，补偿后的激光恢复到无相位畸变的状态；第二、四变形镜根据上支路提供的相位畸变信息对波前相位进行校正，使入射光产生与畸变相位共轭的共轭相位，当该光束通过原光路返回测量单元时，大气湍流等因环境造成的相位畸变将被抵消，光束恢复到无相位畸变状态。
优选地，第一M-Z干涉仪包括第二50:50分束器、第三50:50分束器、第五反射镜、第六反射镜、第一达夫棱镜和第二达夫棱镜；所述第二M-Z干涉仪包括第四50:50分束器、第五50:50分束器，第七反射镜、第八反射镜第三达夫棱镜和第四达夫棱镜。
优选地，所述量子信道为自由空间信道或光纤信道。
所述测量单元接收到来自用户端Alice和用户端Bob将的信号脉冲，并对其进行干涉测量时，所述测量单元的第一50:50分束器擦除了光子态路径信息，使得光子态不可区分。由于HOM效应，相同的光子态会从第一50:50分束器的同一输出端口输出，不同的光子态则相互独立输出。
具体地，所述信号脉冲在测量单元的第一50:50分束器干涉后，从第一50:50分束器的上下两端口输出，经过所述反射镜反射，进入第一M-Z干涉仪和第二M-Z干涉仪。
以第一干涉仪为例，第一M-Z干涉仪对输入光子的作用表示如下：
设入射到第一M-Z干涉仪输入端口的光子态为:
|φ> in＝|0>|1>
其中，|0>表示真空态，|1>表示单光子态。经过第二50:50分束器后光子态变为：
Figure PCTCN2019129490-appb-000005
上述式子表明光子从第二50:50分束器透射端和反射端输出的概率都是50％，其中i表示反射端输出时造成的半波相移。光子态再经过达夫棱镜模块的作用后，两条光路产生φ＝lα的相位差，此时光子态为：
Figure PCTCN2019129490-appb-000006
经过第三50:50分束器后光子态变为：
|φ> BS2＝1/2(1-e iφ)|0>|1>+i/2(1+e iφ)|1>|0>
若设α＝π，则：
轨道角动量阶数l为奇数时，|φ> BS2变为|0>|1>，光子从第三50:50分束器透射；
轨道角动量阶数l为偶数时，|φ> BS2变为|1>|0>，光子从第三50:50分束器反射。
所述M-Z干涉仪输出的态最终被单光子探测器探测，响应输出结果。具体地，测量单元响应的情况如下表：
Figure PCTCN2019129490-appb-000007
上表所示，其中，第一单光子探测器或第三单光子探测器响应时称为“A响应”，表示响应光子的轨道角动量阶数l为奇数；第二单光子探测器或第四单光子探测器响应时称为“B响应”，表示响应光子的轨道角动量阶数l为偶数；可以看出，只有“不同干涉仪下，AB响应”才可以成码。特别地，当来自用户端Alice和用户端Bob的光子都同时进入相同干涉仪时，无法形成单光子干涉现象，因此不能有效地对轨道角动量阶数l进行奇偶分离，造成探测器的随机响应，导致无法成码。“不同干涉仪下，AB响应”称为成功探测事件。
最后用户端Alice和用户端Bob根据测量单元的响应情况，经过基的对比和密钥协商等过程后，在本地产生一致的密钥。
一种实时跟踪补偿的OAM测量设备无关量子密钥分发方法，该方法应用于如上述所述 的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统中，该方法包括以下步骤：
S1、信道环境监测：测量单元向用户端Alice和用户端Bob发射强激光脉冲，用户端Alice和用户端Bob利用该脉冲进行时钟同步和防窃听监测，同时根据入射高斯脉冲的光斑的分散程度估计大气湍流强度；当大气湍流强度低于阈值且监测无窃听时，执行下一步；
S2、比特编码：用户端Alice和用户端Bob随机选择X基或Y基进行信息编码，利用空间光调制器将比特信息随机编码至4个轨道角动量态中，然后将其传输至中间的测量单元；其中X基为{|o>，|e>}；Y基为
Figure PCTCN2019129490-appb-000008
|o>和
Figure PCTCN2019129490-appb-000009
代表比特0；|e>和
Figure PCTCN2019129490-appb-000010
代表比特1；|o>和|e>分别代表拓扑荷数为奇数和偶数的轨道角动量态；
S3、Bell测量：测量单元执行测量操作，然后宣布哪些比特得到了成功的探测，同时公布它的测量结果；用户端Alice和用户端Bob保留以上数据，并丢弃其他码位的数据；
S4、对基：用户端Alice和用户端Bob通过公共信道进行对基，将相同基下制备的比特选择出来，并协商进行比特翻转，保证通信双方比特的一致性；在完成这些操作之后，保留下来数据被作为原始密钥；
S5、误码估计：用户端Alice和用户端Bob利用X基下获得的原始密钥生成最终的安全密钥，用Y基下获得的原始密钥作为测试比特，检测误码率，如果误码率高于阈值，说明存在窃听，放弃此次通信过程，否则保留剩余数据执行下一步；
S6、密钥协商：用户端Alice和用户端Bob利用公共经典信道对筛选后的数据进行纠错和私钥放大，经过数据协调后，用户端Alice和用户端Bob拥有一致的安全密钥。
优选地，进行所述比特编码时，用户端Alice和用户端Bob随机选择拓扑荷数为奇数或偶数的轨道角动量态或叠加态进行编码，允许以任意奇数或偶数阶的轨道角动量态组成一组相互无偏基进行编码。
与现有技术相比，本发明的有益效果为：
1、本发明一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统的用户端运用两个变形镜和CCD组成自适应光学系统，可对大气湍流引起的相位畸变进行实时跟踪监测，估计大气湍流程度，并且实时补偿畸变相位，提高了测量设备无关量子密钥分发系统的抗干扰能力。
2、本发明的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统中，用户双方的脉冲信号均来自同一激光器，它们的光谱模式是自然相同的，在干涉测量时具有极高的 保真度；利用该光源，可方便地实现实时的信道监测，防止特洛伊木马攻击，方便地进行时钟同步。
3、本发明的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统及方法，利用具有轨道角动量(OAM)的光子作为信息的载体，能够在不对准基参考系的情况下进行测量设备无关量子密钥分发，提高密钥速率；并且轨道角动量态具有无限维度的特性，使得本发明具有极强的扩展能力，可方便地结合轨道角动量的复用/分离装置，提高信道容量；
附图说明
图1为本发明测量单元的结构框图；
图2为本发明用户端Alice的结构框图；
图3为本发明用户端Bob的结构框图；
图4为本发明的系统工作原理图；
图5为本发明的系统工作流程图。
具体实施方式
下面结合附图对本发明的具体实施方式作进一步说明。
如图1至图3所示，一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，包括：用户端Alice、用户端Bob和测量单元。
所述用户端Alice和用户端Bob通过量子信道与测量单元连接，其中：
所述量子信道为自由空间信道或光纤信道，本方案以自由空间信道为例进行说明。
所述测量单元利用脉冲激光器产生强的高斯脉冲，高斯脉冲通过偏振分束器和分束器将传输至用户端，用户端利用电荷耦合元件(CCD)和分束器进行监测与同步，同时采用变形镜对畸变的相位进行相位畸变补偿，利用强度调制器和空间光调制器随机产生光子数小于1的具有轨道角动量的诱骗态和信号态光子，发送到中间的测量单元，测量单元利用时间复用的单光子探测器对用户发送的光子态进行测量，并公布测量结果，用户根据测量的响应情况进过基对比和协商等过程后，在本地产生一致的密钥。
如图1所示，所述测量单元包括：第一望远镜系统301、第二望远镜系统302，第一50:50分束器305、第二50:50分束器320、第三50:50分束器325、第四50:50分束器330、 第五50:50分束器335，第一偏振分束器306，脉冲激光器307，第一反射镜303、第二反射镜304，第三反射镜308、第四反射镜309、第一M-Z干涉仪、第二M-Z干涉仪、第一单光子探测器326、第二单光子探测器327、第三单光子探测器336和第四单光子探测器337。所述第一望远镜系统301、第二望远镜系统302主要用于光束的准直；所述第一偏振分束器306透过水平偏振光，反射垂直偏振光；所述脉冲激光器307作为泵浦光源，用于泵浦产生基模高斯光；所述第一M-Z干涉仪340包括第二50:50分束器320、第三50:50分束器325、第五反射镜321、第六反射镜323、第一达夫棱镜324和第二达夫棱镜322；所述第二M-Z干涉仪341包括第四50:50分束器330、第五50:50分束器335，第七反射镜331、第八反射镜333和、第三达夫棱镜332和第四达夫棱镜334；所述第一M-Z干涉仪340和第二M-Z干涉仪341用于分离轨道角动量阶数l为奇数和偶数的光子。以第一M-Z干涉仪340为例，第一M-Z干涉仪340两条光路中的第一达夫棱镜324和第二达夫棱镜322的相对角度为α/2时，所述第一达夫棱镜324、第二达夫棱镜322的作用等效于在其中一条光路加入旋转角度为α的光束旋转器，使轨道角动量为l的光子在干涉仪两条光路产生φ＝lα的相位差；所述第一单光子探测器326、第二单光子探测器327、第三单光子探测器336和第四单光子探测器337用于探测单光子量级的光信号；
如图2所示，所述用户端Alice包括：第三望远镜系统101，第一窄带滤波器102，第一分束器103，第一电荷耦合元件(CCD)104，第一延时器105，第二偏振分束器106，第一变形镜107，第二变形镜111，第一半波片108，第一空间光调制器109和第一强度调制器110。
如图3所示，所述用户端Bob包括：第四望远镜系统201，第二窄带滤波器202，第二分束器203，第二电荷耦合元件(CCD)204，第二延时器205，第三偏振分束器206，第三变形镜207，第四变形镜211，第二半波片208，第二空间光调制器209和第二强度调制器210。
所述第三望远镜系统101和第四望远镜系统201均包括两个共焦的凸透镜，用于控制激光脉冲的尺度大小，控制激光光束的远场发散角；所述第一窄带滤波器102和第二窄带滤波器202用于滤除通信波段以外的光；所述第一分束器103和第二分束器203将入射脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述第一电荷耦合元件(CCD)104和第二电荷耦合元件(CCD)204用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及下支路的相位畸变补偿提供参考信息；所述第二偏振分束器 106和第三偏振分束器206透过水平偏振光，反射垂直偏振光；所述第一变形镜107、第二变形镜111，第三变形镜207和第四变形镜211又称波前校正器，可根据相位畸变的参考信息，改变光波波前传输的光程或改变传输媒介的折射率来改变入射光波波前的相位结构，从而达到对光波波面相位进行补偿的目的；所述第一半波片108、第二半波片208的主截面与入射光偏振面呈45度放置，可将入射光的偏振方向旋转90度；所述第一空间光调制器109、第二空间光调制器209为纯相位型反射式液晶空间光调制器，是一种基于液晶分子电致双折射效应的有源数字光学器件，用于调制光束的轨道角动量；所述第一强度调制器110、第二强度调制器210可精确产生不同平均光子数强度的诱骗态和信号态光子。
如图4所示，在进行量子通信时，所述测量单元的脉冲激光器307发出基模高斯光束，先经过第一偏振分束器306的筛选，将偏振模式为竖直偏振的基模高斯光反射至第一50:50分束器305分成两束，再经过所述第一望远镜系统301、第二望远镜系统302准直，控制远场发散角，然后通过量子信道发往用户端Alice和用户端Bob；
如图2所示，所述用户端Alice的第三望远镜系统101接收来自测量单元的脉冲激光，然后经过第一窄带滤波器102、第二窄带滤波器202滤除通信波段以外的光，再经过第一分束器103将入射的脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述上支路连接第一电荷耦合元件(CCD)104用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息；所述下支路用于调制脉冲加载相位信息，依次连接第一延时器105、第二偏振分束器106、第一变形镜107、第一半波片108、第一空间光调制器109和第一强度调制器110和第二变形镜111。分离到下支路的脉冲激光先进入第一延时器105，经过一定的时延后进入第二偏振分束器106，第二偏振分束器106将脉冲激光反射至第一变形镜107，第一变形镜107根据上支路提供的参考信息对波前相位进行畸变补偿，补偿后的脉冲激光将被反射至第一半波片108，第一半波片108将其偏振态翻转90度后进入第一空间光调制器109，第一空间光调制器109对脉冲进行轨道角动量的编码，编码后的脉冲通过第一强度调制器111被调制成不同平均光子数强度的轨道角动量信号态与诱骗态，经过第二变形镜111进行相位校正，从第二偏振分束器106透射，通过第一延时器105、第一分束器103和第一窄带滤波器102到达第三望远镜系统101，第三望远镜系统101对信号态和诱骗态进行准直，发往测量单元。
如图3所示，所述户端Bob的第四望远镜系统201接收来自测量单元的脉冲激光，然后经过第二窄带滤波器202滤除通信波段以外的其他光，再经过第二分束器203将入射的 脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述上支路连接第二电荷耦合元件(CCD)204用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息；所述下支路用于调制脉冲加载相位信息，依次连接第二延时器205、第三偏振分束器206、第三变形镜207、第二半波片208、第二空间光调制器209和第二强度调制器210和第四变形镜211。分离到下支路的脉冲激光先进入第二延时器205，经过一定的时延后进入第三偏振分束器206，第三偏振分束器206将脉冲激光反射至第三变形镜207，第三变形镜207根据上支路提供的参考信息对波前相位进行畸变补偿，补偿后的脉冲激光将被反射至第二半波片208，第二半波片208将其偏振态翻转90度后进入第一空间光调制器209，第一空间光调制器209对脉冲进行轨道角动量的编码，编码后的脉冲通过第二强度调制器210被调制成不同平均光子数强度的轨道角动量信号态与诱骗态，经过第四变形镜211进行相位校正，从第三偏振分束器206透射，通过第二延时器205、第二分束器203和第二窄带滤波器202到达第四望远镜系统201，第四望远镜系统201对信号态和诱骗态进行准直，发往测量单元。
所述第一空间光调制器109和第二空间光调制器209对轨道角动量进行编码时，随机选择四个态
Figure PCTCN2019129490-appb-000011
中的一个进行编码。其中{|o>，|e>}为X基；
Figure PCTCN2019129490-appb-000012
为Y基；|o>和
Figure PCTCN2019129490-appb-000013
代表比特0；|e>和
Figure PCTCN2019129490-appb-000014
代表比特1；|o>和|e>分别代表拓扑荷数为奇数和偶数的轨道角动量态。
所述测量单元的第一望远镜系统301、第二望远镜系统302分别接收来自用户端Alice和用户端Bob的信号脉冲，此信号脉冲先经过所述第一反射镜303、第二反射镜304反射后，在第一50:50分束器305处干涉。所述第一50:50分束器305擦除了光子态路径信息，使得光子态不可区分。由于HOM效应，相同的光子态会从第一50:50分束器305的同一输出端口输出，不同的光子态则相互独立输出。
所述信号脉冲从第一50:50分束器305的上下两端口输出，通过所述第三反射镜308、第四反射镜309的反射，进入第一M-Z干涉仪340和第二M-Z干涉仪341。以第一M-Z干涉仪340为例。第一M-Z干涉仪340对输入光子的作用表示如下：
设入射到第一M-Z干涉仪340输入端口的光子态为：
|φ> in＝|0>|1>
其中，|0>表示真空态，|1>表示单光子态。经过第二50:50分束器320后光子态变为：
Figure PCTCN2019129490-appb-000015
上述式子表明光子从第二50:50分束器320透射端和反射端输出的概率都是50％，其中i表示反射端输出时造成的半波相移。光子态再经过第一达夫棱镜322、第二达夫棱镜324的作用后，两条光路产生φ＝lα的相位差，此时光子态为：
Figure PCTCN2019129490-appb-000016
经过第三50:50分束器325后光子态变为：
|φ> BS2＝1/2(1-e iφ)|0>|1>+i/2(1+e iφ)|1>|0>
若设α＝π，则：
轨道角动量阶数l为奇数时，|φ> BS2变为|0>|1>，光子从第三50:50分束器325透射；
轨道角动量阶数l为偶数时，|φ> BS2变为|1>|0>，光子从第三50:50分束器325反射。
所述M-Z干涉仪输出的态最终被单光子探测器探测，响应输出结果。具体地，测量单元响应的情况如下表：
Figure PCTCN2019129490-appb-000017
如上表所示，其中，所述第一单光子探测器326或第三单光子探测器336响应时称为“A响应”，表示响应光子的轨道角动量阶数l为奇数；第二单光子探测器327或第四单光子探测器337响应时称为“B响应”，表示响应光子的轨道角动量阶数l为偶数；可以看出，只有“不同干涉仪下，AB响应”才可以成码。特别地，当来自用户端Alice和用户端Bob的光子都同时进入相同干涉仪时，无法形成单光子干涉现象，因此不能有效地对轨道角动量阶数l进行奇偶分离，造成探测器的随机响应，导致无法成码。“不同干涉仪下，AB响应”称为成功探测事件。
最后用户端Alice和用户端Bob根据测量单元的响应情况，经过基的对比和密钥协商等过程后，在本地产生一致的密钥。
如图5所示，一种基于轨道角动量的测量设备无关量子密钥分发方法，该方法应用如上述所述的一种基于轨道角动量的测量设备无关量子密钥分发系统中，该方法包括以下步骤：
S1、信道环境监测：测量单元向用户端Alice和用户端Bob发射强激光脉冲，用户端Alice和用户端Bob利用该脉冲进行时钟同步和防窃听监测，同时根据入射高斯脉冲的光斑的分散程度估计大气湍流强度；当大气湍流强度低于阈值且监测无窃听时，执行下一步；
S2、比特编码：用户端Alice和用户端Bob随机选择X基或Y基进行信息编码，利用空间光调制器将比特信息随机编码至4个轨道角动量态中，然后将其传输至中间的测量单元；其中X基为{|o>，|e>}；Y基为
Figure PCTCN2019129490-appb-000018
|o>和
Figure PCTCN2019129490-appb-000019
代表比特0；|e>和
Figure PCTCN2019129490-appb-000020
代表比特1；|o>和|e>分别代表拓扑荷数为奇数和偶数的轨道角动量态；进行所述比特编码时，用户端Alice和用户端Bob随机选择拓扑荷数为奇数或偶数的轨道角动量态或叠加态进行编码，允许以任意奇数或偶数阶的轨道角动量态组成一组相互无偏基进行编码；
S3、Bell测量：测量单元执行测量操作，然后宣布哪些比特得到了成功的探测，同时公布它的测量结果；用户端Alice和用户端Bob保留以上数据，并丢弃其他码位的数据；
S4、对基：用户端Alice和用户端Bob通过公共信道进行对基，将相同基下制备的比特选择出来，并协商进行比特翻转，保证通信双方比特的一致性；在完成这些操作之后，保留下来数据被作为原始密钥；
S5、误码估计：用户端Alice和用户端Bob利用X基下获得的原始密钥生成最终的安全密钥，用Y基下获得的原始密钥作为测试比特，检测误码率，如果误码率高于阈值，说明存在窃听，放弃此次通信过程，否则保留剩余数据执行下一步；
S6、密钥协商：用户端Alice和用户端Bob利用公共经典信道对筛选后的数据进行纠错和私钥放大，经过数据协调后，用户端Alice和用户端Bob拥有一致的安全密钥。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何在本申请揭露的技术范围内的变化或替换，都应涵盖在本申请的保护范围之内。根据上述说明书的揭示和教导，本发明所属领域的技术人员还可以对上述实施方式进行变更和修改。因此，本发明并不局限于上面揭示和描述的具体实施方式，对发明的一些修改和变更也应当落入本发明的权利要求的保护范围内。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本发明构成任何限制。

Claims (10)

  1. 一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，包括：用户端Alice、用户端Bob和测量单元；
    所述用户端Alice和用户端Bob通过量子信道与测量单元连接，其中：
    所述测量单元包括：第一、二望远镜系统，第一50:50分束器，第一偏振分束器，脉冲激光器，第一至第四反射镜，第一、二M-Z干涉仪和第一至第四单光子探测器；
    所述测量单元的脉冲激光器发出基模高斯光束时，先经过第一偏振分束器的筛选将偏振模式为竖直偏振的基模高斯光反射至第一50:50分束器分成两束，再分别经过第一反射镜和第二反射镜反射，最后经过所述第一望远镜系统和第二望远镜系统进行准直，通过量子信道分别发往用户端Alice和用户端Bob；
    用户端Alice和用户端Bob分别对来自测量单元的脉冲激光实现信道环境实时监测、相位畸变补偿以及轨道角动量的编码后发往测试单元；
    所述测量单元的第一望远镜系统和第二望远镜系统分别接收来自用户端Alice和用户端Bob的信号脉冲时，此信号脉冲先经过所述第一反射镜和第二反射镜的反射，然后在第一50:50分束器处进行干涉，干涉后的脉冲分别经过第三反射镜和第四反射镜的反射，分别进入到第一M-Z干涉仪和第二M-Z干涉仪，被第一M-Z干涉仪和第二M-Z干涉仪分离后，分别进入第一至第四单光子探测器造成响应，输出测量结果；用户端Alice和用户端Bob根据测量的响应情况，经过基的对比和密钥协商等过程后，在本地产生一致的密钥。
  2. 如权利要求1所述的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，所述用户端Alice包括：第三望远镜系统，第一窄带滤波器，第一分束器，第一电荷耦合元件，第一延时器，第二偏振分束器，第一变形镜，第二变形镜，第一半波片，第一空间光调制器和第一强度调制器；
    所述用户端Bob包括：第四望远镜系统，第二窄带滤波器，第二分束器，第二电荷耦合元件，第二延时器，第三偏振分束器，第三变形镜，第四变形镜，第二半波片，第二空间光调制器和第二强度调制器。
  3. 如权利要求2所述的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，所述第一电荷耦合元件和第二电荷耦合元件用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息，所述第一、二变形镜和第三、四变形镜分别根据所述第一电荷耦合元件和第二电荷耦合元件提供的参考信息对波前相位进行畸变补偿。
  4. 如权利要求2所述的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，所述第一、二空间光调制器与所述第一、二强度调制器对脉冲进行随机调制；
    所述第一空间光调制器和第二空间光调制器对轨道角动量进行编码时，随机选择四个态
    Figure PCTCN2019129490-appb-100001
    中的一个进行编码；其中{|o>，|e>}为X基；
    Figure PCTCN2019129490-appb-100002
    为Y基；|o>和
    Figure PCTCN2019129490-appb-100003
    代表比特0；|e>和
    Figure PCTCN2019129490-appb-100004
    代表比特1；|o>和|e>分别代表拓扑荷数为奇数和偶数的轨道角动量态；所述第一、二强度调制器精确产生不同平均光子数强度的诱骗态和信号态光子。
  5. 如权利要求2所述的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，所述用户端Alice的第三望远镜系统接收来自测量单元的脉冲激光，然后经过第一窄带滤波器滤除通信波段以外的光，再经过第一分束器将入射的脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述上支路连接第一电荷耦合元件用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息；所述下支路用于调制脉冲加载相位信息，依次连接第一延时器、第二偏振分束器、第一变形镜、第一半波片、第一空间光调制器、第一强度调制器和第二变形镜；分离到下支路的脉冲激光先进入第一延时器，经过一定的时延后进入第二偏振分束器，第二偏振分束器将脉冲激光反射至第一变形镜，第一变形镜根据上支路提供的参考信息对波前相位进行畸变补偿；补偿后的脉冲激光将被反射至第一半波片，第一半波片将其偏振态翻转90度后进入第一空间光调制器，第一空间光调制器对脉冲进行轨道角动量的编码；编码后的脉冲通过第一强度调制器被调制成不同平均光子数强度的轨道角动量信号态与诱骗态，经过第二变形镜进行相位校正，从第二偏振分束器透射，通过第一延时器、第一分束器和第一窄带滤波器到达第三望远镜系统；最后第三望远镜系统对信号态和诱骗态进行准直，发往测量单元。
  6. 如权利要求2所述的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，所述用户端Bob的第四望远镜系统接收来自测量单元的脉冲激光，然后经过第二窄带滤波器滤除通信波段以外的光，再经过第二分束器将入射的脉冲激光分成强弱两路，分别为较强的上支路和较弱的下支路；所述上支路连接第二电荷耦合元件用于实时监测激光脉冲的强度以及大气湍流造成的波前相位畸变，为时钟同步以及相位畸变补偿提供参考信息；所述下支路用于调制脉冲加载相位信息，依次连接第二延时器、第三偏振分束器、 第三变形镜、第二半波片、第二空间光调制器和第二强度调制器；分离到下支路的脉冲激光先进入第二延时器，经过一定的时延后进入第三偏振分束器，第三偏振分束器将脉冲激光反射至第三变形镜，第三变形镜根据上支路提供的参考信息对波前相位进行畸变补偿，补偿后的脉冲激光将被反射至第二半波片，第二半波片将其偏振态翻转90度后进入第二空间光调制器，第二空间光调制器对脉冲进行轨道角动量的编码，编码后的脉冲通过第二强度调制器被调制成不同平均光子数强度的轨道角动量信号态与诱骗态，经过第四变形镜进行相位校正，从第三偏振分束器透射，通过第二延时器、第二分束器和第二窄带滤波器到达第四望远镜系统；最后第四望远镜系统对信号态和诱骗态进行准直，发往测量单元。
  7. 一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，第一M-Z干涉仪包括第二50:50分束器、第三50:50分束器、第五反射镜、第六反射镜、第一达夫棱镜和第二达夫棱镜；所述第二M-Z干涉仪包括第四50:50分束器、第五50:50分束器，第七反射镜、第八反射镜，第三达夫棱镜和第四达夫棱镜。
  8. 一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统，其特征在于，所述量子信道为自由空间信道或光纤信道；
  9. 一种实时跟踪补偿的OAM测量设备无关量子密钥分发方法，其特征在于，该方法应用于如权利要求1-8任意一项所述的一种实时跟踪补偿的OAM测量设备无关量子密钥分发系统中，该方法包括以下步骤：
    S1、信道环境监测：测量单元向用户端Alice和用户端Bob发射强激光脉冲，用户端Alice和用户端Bob利用该脉冲进行时钟同步和防窃听监测，同时根据入射高斯脉冲的光斑的分散程度估计大气湍流强度；当大气湍流强度低于阈值且监测无窃听时，执行下一步；
    S2、比特编码：用户端Alice和用户端Bob随机选择X基或Y基进行信息编码，利用空间光调制器将比特信息随机编码至4个轨道角动量态中，然后将其传输至中间的测量单元；其中X基为{|o>，|e>}；Y基为
    Figure PCTCN2019129490-appb-100005
    |o>和
    Figure PCTCN2019129490-appb-100006
    代表比特0；|e>和
    Figure PCTCN2019129490-appb-100007
    代表比特1；|o>和|e>分别代表拓扑荷数为奇数和偶数的轨道角动量态；
    S3、Bell测量：测量单元执行测量操作，然后宣布哪些比特得到了成功的探测，同时公布它的测量结果；用户端Alice和用户端Bob保留以上数据，并丢弃其他码位的数据；
    S4、对基：用户端Alice和用户端Bob通过公共信道进行对基，将相同基下制备的比特选择出来，并协商进行比特翻转，保证通信双方比特的一致性；在完成这些操作之后， 保留下来数据被作为原始密钥；
    S5、误码估计：用户端Alice和用户端Bob利用X基下获得的原始密钥生成最终的安全密钥，用Y基下获得的原始密钥作为测试比特，检测误码率，如果误码率高于阈值，说明存在窃听，放弃此次通信过程，否则保留剩余数据执行下一步；
    S6、密钥协商：用户端Alice和用户端Bob利用公共经典信道对筛选后的数据进行纠错和私钥放大，经过数据协调后，用户端Alice和用户端Bob拥有一致的安全密钥。
  10. 如权利要求9所述的一种实时跟踪补偿的OAM测量设备无关量子密钥分发方法，其特征在于，进行所述比特编码时，用户端Alice和用户端Bob随机选择拓扑荷数为奇数或偶数的轨道角动量态或叠加态进行编码，允许以任意奇数或偶数阶的轨道角动量态组成一组相互无偏基进行编码。
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