WO2018130052A1 - 一种相位偏振多自由度调制qkd网络系统及方法 - Google Patents

一种相位偏振多自由度调制qkd网络系统及方法 Download PDF

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WO2018130052A1
WO2018130052A1 PCT/CN2017/117394 CN2017117394W WO2018130052A1 WO 2018130052 A1 WO2018130052 A1 WO 2018130052A1 CN 2017117394 W CN2017117394 W CN 2017117394W WO 2018130052 A1 WO2018130052 A1 WO 2018130052A1
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polarization
wavelength
pulse
bob
phase
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PCT/CN2017/117394
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English (en)
French (fr)
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郭邦红
胡敏
张盼盼
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华南师范大学
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Priority to EP17891613.6A priority Critical patent/EP3570485B1/en
Priority to KR1020197002931A priority patent/KR102155350B1/ko
Priority to US16/314,858 priority patent/US11070370B2/en
Priority to AU2017392255A priority patent/AU2017392255B2/en
Priority to JP2019502561A priority patent/JP6666514B2/ja
Publication of WO2018130052A1 publication Critical patent/WO2018130052A1/zh

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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
    • 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
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/021—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
    • H04J14/0212—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM] using optical switches or wavelength selective switches [WSS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/0282—WDM tree architectures
    • 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

Definitions

  • the invention relates to the field of quantum secure communication and optical fiber communication technology in the field of communication, in particular to a phase polarization multi-degree-of-freedom modulation QKD network system and a key distribution method.
  • quantum signal modulation generally adopts a single degree of freedom modulation such as polarization, phase, frequency, and intensity.
  • Polarization modulation of an optical signal means loading information by adjusting the polarization direction of the light.
  • two linear polarization states of photons are used for encoding. Since the polarization state of light is susceptible to stress birefringence and polarization mode dispersion in the optical fiber during transmission, and environmental interference, polarization compensation or other A method to ensure polarization stability.
  • Phase modulation refers to the use of the phase of light to encode information.
  • the phase modulation principle of quantum communication is mainly based on the Mach-Zehnder interferometer, and the core device is a phase modulator.
  • phase modulation scheme was based on a single equal arm M-Z interferometer. Due to the influence of the environment, the arm length difference of the two arms will be unstable, and the phase difference will also drift, and the interference effect will be seriously affected, especially for the transmission of longer distances, the interference effect is worse. Later, people proposed a double unequal arm M-Z interference system. The time disturbance on the overlapping portion of the fiber has the same effect on the two pulses, and the interference stability is greatly improved. However, even with the dual unequal arm M-Z interferometer, small changes in arm length can cause a drop in interference contrast.
  • the M-Z interferometer QKD system generally adopts the BB84 protocol and the B92 protocol.
  • the security of the system is based on the fact that Eve cannot know exactly the base used by the legitimate communication party to encode and detect the information.
  • the BB84 protocol and the B92 protocol when the password is finally formed, the comparison between the coding base and the measurement base is performed, so the protocol efficiency is not high and the coding rate is low, which cannot meet the practical application requirements.
  • the differential phase coding inherits the advantages of fast encoding speed, strong anti-interference ability and extreme transmission distance. It is suitable for realizing in the optical fiber line and greatly improves the code generation efficiency.
  • Differential phase encoding uses two pulses before and after to carry information. The pulse experiences the same phase and polarization changes in the fiber, which is insensitive to various interferences in the fiber, thereby improving the stability of the system.
  • Orbital angular momentum has multiple degrees of freedom, enabling high dimensionality The encoding of the sub-information.
  • the orbital angular momentum multi-degree of freedom modulation is mainly applied to quantum free space communication and classic multi-channel high-speed communication.
  • a phase-polarized multi-degree-of-freedom modulation QKD network system is to be developed to realize one-to-many communication.
  • the users are relatively independent, ensuring that the key generation rate of a single user is stable and does not decrease as the number of users increases, thereby achieving a secure, stable, and efficient transmission of the quantum key distribution network system.
  • the object of the present invention is to overcome the deficiencies of the prior art and propose a phase polarization multi-degree of freedom modulation QKD network system and method.
  • the phase polarization multi-degree-of-freedom modulation QKD network system and method use a multi-wavelength pulse generated by a single-source multi-wavelength laser as a multi-user information transmission carrier to transmit each wavelength pulse to different legal users to realize one-to-many communication.
  • the users are relatively independent, ensuring that the key generation rate of a single user is stable and does not decrease as the number of users increases. Thereby achieving a safe, stable and efficient transmission of the quantum key distribution network system.
  • phase-polarized multi-degree-of-freedom modulation multi-user quantum key distribution network system adopts a new quantum information coding method, that is, adopts differential phase coding and simultaneous polarization coding, which can effectively reduce the instability caused by external conditions.
  • the bit error rate improves the security and stability of the system and increases the photon utilization from the original 0.5 to 2.
  • the existing differential phase and polarization coded composite QKD scheme is improved, the quantum key generation rate is improved, and the waiting time of each communication time slot is shortened.
  • the system uses a single-source multi-wavelength laser, an attenuator, a polarization beam splitter, a combiner, a phase modulator, and a polarization controller as carriers for multi-user information transmission.
  • the phase difference between the upper and lower arms is loaded with one information bit, and the pulse polarization state loads another information bit.
  • Each wavelength pulse is transmitted to a different legal user through a wavelength division multiplexing unit, and corresponding polarization demodulation and phase demodulation are performed.
  • Each user is relatively independent, ensuring that the key generation rate of a single user is stable.
  • a phase polarization multi-degree-of-freedom modulation QKD network system includes an Alice control end, a wavelength division multiplexing unit and a multi-user Bob end, and the Alice end is connected to the multi-user Bob end through a wavelength division multiplexing unit.
  • the Alice end includes a multi-wavelength laser generating device, an attenuator, a first polarizing beam splitter, a first beam combiner, a phase modulator, a first polarization controller, and a second polarization controller;
  • the wavelength division multiplexing unit includes a wavelength selection device
  • the multi-user Bob end includes a plurality of unit Bob users receiving different wavelengths, and the unit Bob user ends each include a second polarization beam splitter, a third polarization controller, a fourth polarization controller, and a third polarization beam splitter.
  • the multi-wavelength laser generating device generates a pulse train having a plurality of wavelengths, which are then attenuated by the attenuator into a single photon pulse, the single photon pulse being split into vertical polarization and horizontal polarization pulses by the first polarization beam splitter,
  • the polarization controller and the second polarization controller perform pulse polarization rotation, and the last two pulses enter the Bob end in the same polarization state;
  • Multi-wavelength laser pulses having the same polarization are transmitted to the wavelength routing device, and the unit Bob user terminal of the corresponding wavelength is selected according to the wavelength addressing manner, and the second polarization beam splitter of the user terminal of the unit Bob is subjected to polarization demodulation when the polarization is performed.
  • the bit is "0"
  • the horizontal polarization pulse is selected to pass through the third polarization controller
  • the polarization bit is "1”
  • the vertical polarization pulse is selected to pass through the fourth polarization controller
  • the third polarization beam splitter After outputting from the third polarization controller, two paths of the upper arm path and the lower arm path are formed through the third polarization beam splitter: wherein the upper arm path: the pre-pulse reaches the second beam combiner through a delay; the lower arm path : the post-pulse directly reaches the second combiner, the two beams of the upper arm path and the lower arm path interfere at the second combiner, and then the first photon detector and the random modulation according to the phase difference The second photon detector makes an identification response;
  • the fourth polarization beam splitter After outputting from the fourth polarization controller, two paths of the upper arm path and the lower arm path are formed through the fourth polarization beam splitter: wherein the upper arm path: the pre-pulse reaches the third combiner through a delay; the lower arm path : the post-pulse directly reaches the third combiner, the two beams of the upper arm path and the lower arm path interfere at the third combiner, and then the third photon detector is based on a randomly modulated phase difference The fourth photon detector makes an identification response.
  • the upper arm path has a delay of one T greater than the lower arm path.
  • the first polarization controller rotates the pulse polarization
  • the second polarization controller rotates the pulse polarization Where n is "0" or "1", respectively.
  • the wavelength routing device is a wavelength division multiplexer, an arrayed waveguide grating, a Bragg grating or a wavelength selective switch.
  • the multi-wavelength laser generating device comprises a multi-wavelength pulsed laser and a wavelength selector, the multi-wavelength pulsed laser generating a coherent multi-wavelength pulsed laser that satisfies simultaneous communication of a plurality of unit Bob users, and then selecting by the wavelength The device selects so that the Bob user of the corresponding wavelength selects the pulsed laser of the corresponding wavelength.
  • the wavelength selector selects the wavelength by means of a second-order equally-frequency interval.
  • the first photon detector, the second photon detector, the third photon detector, and the fourth photon detector The response according to the phase difference of the pulse is: when the phase difference of the two consecutive pulses is 0, the first detector responds, the measurement result is “00”, the second detector responds, and the measurement result “01”; When the phase difference between two consecutive pulses is ⁇ , the third detector responds with a measurement result of “10”, and the fourth detector responds with a measurement result of “11”.
  • the unit Bob client is Bobn, where n is a non-zero natural number.
  • Fiber length test and pulse delay setting The Alice end sends a set of pulses, and each unit Bob user end determines the length of the fiber in the link by measuring the arrival time of the pulse, according to each unit between the Bob user end and the Alice end. Length relationship, preset the fiber length of each unit Bob user end, and set the delay between the upper arm path and the lower arm path of each unit Bob user end;
  • the wavelength selector selects a wavelength pulse suitable for use by each unit Bob user end according to the wavelength allocation plan, and pulse light of different wavelengths is allocated to the corresponding unit Bob user end to perform one-to-many network communication. ;
  • the multi-wavelength pulse generating device generates a pulse, the pulse period is greater than the delay time T; after the attenuator, it attenuates to a single photon level, and then enters the upper arm path through the first polarization beam splitter respectively
  • the lower arm path forms two pulses of delay T, arrives at the first combiner, then sequentially passes through the phase modulator, the first polarization modulator and the second polarization modulation to perform phase polarization modulation, so that they
  • the same polarization state transmission is finally subjected to polarization demodulation and phase demodulation through each unit Bob user end;
  • each unit Bob client records the response of the detector, and records the moments of response of the first photon detector, the second photon detector, the third photon detector and the fourth photon detector Transmitting, by the Alice end, the time of the response of the first photon detector, the second photon detector, the third photon detector, and the fourth photon detector to the Alice end, according to the data sent by the user end of each unit Bob , keep the corresponding key string, and let the rest go.
  • each unit Bob client there is key sharing between each unit Bob client:
  • the security key priority is: Bobi>Bobj
  • Bobj shares the Bobi key
  • the Alice end acts as the intermediate node.
  • the Alice and Bobj keys are used to encrypt the Alice and Bobi keys, and then the encrypted The Bobi key is sent to Bobj.
  • Bobj decrypts it and gets the Bobi key, so that the key is shared with Bobi.
  • the key sharing between the Bob users of each unit is exclusive: the key of a certain unit Bob client can only be shared with one unit Bob client, and can no longer be shared with other unit Bob users after sharing.
  • the invention has the beneficial effects of the invention: 1.
  • the invention adopts a phase polarization multi-degree-of-freedom modulation QKD network system and a key distribution method, can realize one-to-many quantum key sharing, effectively expands information transmission capacity, and is suitable for phase polarization.
  • the present invention adopts a phase and polarization joint modulation method to transmit two information bits by transmitting one photon, and the photon utilization rate is increased from 0.5 to 2; compared with the existing scheme, the scheme reduces device usage and simplifies the structure. And improve the continuity, effectiveness and key generation rate of information.
  • the invention adopts 4 electronic detectors to wait for measurement in 8 time slots per communication, and waits for measurement in 12 time slots for each communication compared with the existing scheme, and the bit error rate caused by the dark count of the detector is reduced. 33.3%, making the system more efficient and stable.
  • the invention adopts the classical DPS quantum key distribution method, and the phase difference of the two branch coherent pulses with the coding interval T (ie, the delay T, T is the picosecond magnitude), so that each phase difference is used as a phase encoding. Effectively resists split photon attacks and sequence attacks, reducing the efficiency of eavesdropper Eve.
  • 1 is a structural block diagram of a wavelength division multiplexing unit and a multi-user Bob end of the present invention
  • FIG. 2 is a block diagram of a phase modulation and polarization modulation structure of the Alice terminal of the present invention
  • FIG. 3 is a block diagram of a Bob-side polarization demodulation and phase demodulation structure according to the present invention.
  • FIG. 4 is a block diagram showing the working principle of the present invention.
  • Figure 5 is a flow chart of the operation of the present invention.
  • the corresponding names of the components are: common optical fiber-101, wavelength routing device-102, dedicated optical fiber-103, 104, 105;
  • Second polarization beam splitter-301, third polarization controller-302, fourth polarization controller-307, third polarization beam splitter-303, fourth polarization beam splitter-308, second beam combiner-304 The third beam combiner-309, the first photon detector-305, the second photon detector-306, the third photon detector-310, and the fourth photon detector-311.
  • the present invention is a point-to-multipoint networking manner, and in particular can be further extended to a multi-point to multi-point manner.
  • the described embodiment is only one of the one-to-many ways of the present invention. Obviously, it can be easily extended to more applications.
  • a phase polarization multi-degree-of-freedom modulation QKD network system includes an Alice control end, a wavelength division multiplexing unit and a multi-user Bob end, and the Alice end passes the wavelength division multiplexing unit and the multi-user Bob end. connection.
  • the Alice end includes a multi-wavelength laser generating device 201, an attenuator 202, a first polarizing beam splitter 203, a first beam combiner 204, a phase modulator 205, a first polarization controller 206, and a second polarization controller 207;
  • the wavelength division multiplexing unit includes a wavelength selection device
  • the multi-user Bob end includes a plurality of unit Bob users receiving different bands, and the unit Bob users each include a second polarization beam splitter 301, a third polarization controller 302, a fourth polarization controller 307, and a third polarization.
  • the multi-wavelength laser generating device generates a pulse train having a plurality of wavelengths, and then is attenuated by the attenuator 202 into a single photon pulse, and the single photon pulse is split into vertical polarization and horizontal polarization pulses by the first polarization beam splitter 203.
  • Reaching the first polarization controller 206 and the second polarization controller 207 respectively for pulse polarization rotation, and the last two pulses enter the Bob end with the same polarization state;
  • Multi-wavelength laser pulses having the same polarization are transmitted to the wavelength routing device 102, and the unit Bob user terminal of the corresponding wavelength is selected according to the wavelength addressing manner, and the second polarization beam splitter 301 of the unit Bob user terminal is subjected to polarization demodulation.
  • the polarization bit is "0"
  • the horizontal polarization pulse is selected to pass through the third polarization controller 302
  • the polarization bit is "1”
  • the vertical polarization pulse is selected to pass through the fourth polarization controller 307;
  • the third polarization beam splitter 303 After outputting from the third polarization controller, two paths of the upper arm path and the lower arm path are formed through the third polarization beam splitter 303: wherein the upper arm path: the pre-pulse reaches the second beam combiner 304 through a delay; Arm path: the post pulse directly reaches the second combiner 304, the two beams of the upper arm path and the lower arm path interfere at the second combiner 304, and then the first according to the phase difference of the random modulation Photon detector 305 and second photon detector 306 make an identification response;
  • the fourth beam splitter 308 After outputting from the fourth polarization controller 307, the fourth beam splitter 308 forms two paths of the upper arm path and the lower arm path: wherein the upper arm path: the pre-pulse reaches the third combiner 309 after delay; Lower arm path: the post pulse directly reaches the third combiner 309, and two beams of the upper arm path and the lower arm path occur at the third combiner 309 Interference and then the third photon detector 310 and the fourth photon detector 311 make an identification response based on the phase difference of the random modulation.
  • the present invention is a point-to-multipoint networking manner, and in particular can be further extended to a multi-point to multi-point manner.
  • the described embodiment is only one of the one-to-many ways of the present invention. Obviously, it can be easily extended to more applications.
  • the Alice end acts as a transmitter for the pulse signal, and has a multi-wavelength light source, which is capable of generating pulse signals of different bands that satisfy the simultaneous communication of the Bob users of the plurality of units.
  • Each unit Bob client can be assigned a signal of a certain wavelength, and it has a wide applicability to the pulse wavelength, that is, after adjusting the allocation of signal wavelengths between the Bob users of each unit in the wavelength planning process, each unit Bob user
  • the terminal can still work normally.
  • the common optical fiber 101 in Fig. 1 is commonly used by users, and the optical fibers 103, 104, and 105 are dedicated optical fibers for each user, and the sum of the dedicated optical fibers and the shared optical fibers 101 of each user is defined as the distance per user.
  • the wavelength routing device 102 is used between the control terminal Alice and the user terminal Bob to control the path selection of each wavelength pulse signal.
  • FIG. 2 is a schematic diagram of an embodiment of a phase polarization multi-degree-of-freedom modulation QKD network system and method Alice end of the present invention.
  • the Alice end of the system performs phase modulation and polarization modulation on a single photon.
  • Polarization state is The 45° pump light is attenuated to a single photon pulse F(x,t)
  • the single photon pulse is split into two pulses by the first polarization beam splitter 203, and the two pulses have a delay of T.
  • the pulse form becomes
  • the first polarization controller (PC1) 206 rotates the polarization of the delay pulse At this point the pulse is
  • the second polarization controller (PC2) 207 rotates the polarization of the short circuit pulse At this point the pulse is n takes the value "0" or "1".
  • the multi-wavelength laser 201 generates a pulse train having a plurality of wavelengths ( ⁇ 1, ⁇ 2, ⁇ 3, ... ⁇ n), wherein the generated multi-wavelength pulsed laser is polarized to 45°, the pulse period is greater than the delay T, and is attenuated by the attenuator 202.
  • the single photon pulse is divided into horizontally polarized and vertically polarized pulses by the first polarization beam splitter 203, and enters the upper arm path and the lower arm path, respectively, wherein the upper arm path is delayed by T through the lower arm path.
  • the two pulses then pass through a phase modulator 205 which randomly modulates the phase of k ⁇ (k takes 0 or 1) for both pulses.
  • the first polarization controller 206 rotates the pulse polarization.
  • the second polarization controller 207 rotates the pulse polarization Where n is "0" or "1", respectively.
  • the two pulses are transmitted through the fiber to the multi-user Bob end in the same polarization state.
  • FIG. 3 is a schematic diagram of an embodiment of a phase-polarized multi-degree-of-freedom modulation QKD network system and method of the present invention. Taking Bob1 as an example, polarization demodulation and phase demodulation are performed on the Bob1 end.
  • the first photon detector D1 responds, and the corresponding key is "00" at this time;
  • the second photon detector D2 responds, and the corresponding key is "01" at this time.
  • n When n takes "0", two pulses with a time interval T pass through the second polarization beam splitter 301 to enter the third polarization controller 302 in a horizontal polarization state; when n takes "1", the time interval is two of T
  • the pulses enter the polarization controller 307 through the second polarization beam splitter 301 in a vertical polarization state.
  • the third polarization controller 302 only rotates the fast axis pulse polarization It becomes vertical polarization; the vertical polarization pulse is reflected by the third polarization beam splitter 303, passes through the delay T into the second beam combiner 304; the horizontal polarization pulse is directly transmitted through the third polarization beam splitter 303 into the second beam combiner 304.
  • the fourth polarization controller 307 only rotates the slow axis pulse polarization
  • the horizontal polarization is directly transmitted through the fourth polarization beam splitter 308 into the third beam combiner 309; the vertical polarization pulse is reflected by the fourth polarization beam splitter 308, and enters the third beam combiner 309 via the delay T. .
  • the two pulsed lights that meet at the second combiner 304 interfere with each other, and the first photon detector 305 or the second photon detector 306 responds according to a randomly modulated phase difference of 0 or ⁇ .
  • the two pulsed lights that meet at the third combiner 309 interfere with each other, and the third photon detector 310 or the fourth detector 311 responds according to the phase difference 0 or ⁇ of the random modulation.
  • FIG. 4 is a block diagram of a working principle of a phase polarization multi-degree-of-freedom modulation QKD network system and method, including an Alice control end, a wavelength division multiplexing unit, and a multi-user Bob end, and the Alice end is connected to the multi-user Bob end through a wavelength division multiplexing unit.
  • the Alice end phase-modulates and polarization-modulates the single photon separately, and enters the multi-user unit Bob-side polarization demodulation and phase demodulation via the quantum channel.
  • the specific modulation and demodulation process has been described in detail in FIG. 2 and FIG. 3, and details are not described herein again.
  • FIG. 5 is a key distribution method applied to the above phase polarization multi-degree-of-freedom modulation QKD network system, including the following step:
  • Fiber length test and pulse delay setting The Alice end sends a set of pulses, and each unit Bob user end determines the length of the fiber in the link by measuring the arrival time of the pulse, according to each unit between the Bob user end and the Alice end. Length relationship, preset the fiber length of each unit Bob user end, and set the delay between the upper arm path and the lower arm path of each unit Bob user end;
  • the wavelength selector selects a wavelength pulse suitable for use by each unit Bob user end according to the wavelength allocation plan, and pulse light of different wavelengths is allocated to the corresponding unit Bob user end to perform one-to-many network communication. ;
  • the multi-wavelength pulse generating device generates a pulse, the pulse period is greater than the delay time T; after the attenuator, it attenuates to a single photon level, and then enters the upper arm path through the first polarization beam splitter respectively
  • the lower arm path forms two pulses of delay T, arrives at the first combiner, then sequentially passes through the phase modulator, the first polarization modulator and the second polarization modulation to perform phase polarization modulation, so that they
  • the same polarization state transmission is finally subjected to polarization demodulation and phase demodulation through each unit Bob user end;
  • each unit Bob client records the response of the detector, and records the moments of response of the first photon detector, the second photon detector, the third photon detector and the fourth photon detector Transmitting, by the Alice end, the time of the response of the first photon detector, the second photon detector, the third photon detector, and the fourth photon detector to the Alice end, according to the data sent by the user end of each unit Bob , keep the corresponding key string, and let the rest go.
  • the security key priority is: Bobi>Bobj
  • Bobj shares the Bobi key
  • the Alice end acts as the intermediate node.
  • the Alice and Bobj keys are used to encrypt the Alice and Bobi keys, and then the encrypted The Bobi key is sent to Bobj.
  • Bobj decrypts it and gets the Bobi key, so that the key is shared with Bobi.
  • the key sharing between the Bob users of each unit is exclusive: the key of a certain unit Bob client can only be shared with one unit Bob client, and can no longer be shared with other unit Bob users after sharing.
  • the invention has the beneficial effects: 1.
  • the phase polarization multi-degree-of-freedom modulation QKD network system adopted by the invention can realize one-to-many quantum key sharing, effectively expands information transmission capacity, and is suitable for phase polarization multi-degree-of-freedom modulation QKD. Program and other QKD solutions.
  • the present invention adopts a phase and polarization joint modulation method to transmit two information bits by transmitting one photon, and the photon utilization rate is increased from 0.5 to 2; compared with the existing scheme, the scheme reduces device usage and simplifies the structure. And improve the continuity, effectiveness and key generation rate of information.
  • the invention adopts 4 electronic detectors to wait for measurement in 8 time slots per communication, and waits for measurement in 12 time slots for each communication compared with the existing scheme, and the bit error rate caused by the dark count of the detector is reduced. 33.3%, making the system more efficient and stable.
  • the invention adopts the classical DPS quantum key distribution method, and the phase difference of the two branch coherent pulses with the coding interval T (ie, the delay T, T is the picosecond magnitude), so that each phase difference is used as a phase encoding. Effectively resists split photon attacks and sequence attacks, reducing the efficiency of eavesdropper Eve.

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Abstract

本发明涉及一种相位偏振多自由度调制量子密钥分发(QKD)网络系统及方法，包括Alice发送端、波分复用(WDM)单元和多用户Bob端，Alice端通过波分复用单元与多用户Bob端连接，所述Alice端包括多波长激光产生装置、衰减器、第一偏振分束器、第一合束器、相位调制器、第一、第二偏振控制器；所述波分复用单元包括波长选择装置；所述多用户Bob端包括接收不同波段的若干单元Bob用户端，所述单元Bob用户端均包括第二、第三和第四偏振控制器、第三、第四偏振分束器、第二、第三合束器、第一至第四光子探测器。本发明采用的QKD网络系统，能够实现一对多的量子密钥共享，有效地扩大了信息传递容量，适用于相位偏振多自由度调制QKD方案及其它QKD方案。

Description

一种相位偏振多自由度调制QKD网络系统及方法 技术领域
本发明涉及通信领域中的量子保密通信以及光纤通信技术领域，具体是相位偏振多自由度调制QKD网络系统及密钥分发方法。
背景技术
目前，量子信号调制普遍采用偏振、相位、频率、强度等单一自由度调制。光信号的偏振调制是指通过调节光的偏振方向实现对信息的加载。通常采用光子的两个线偏振态进行编码，由于光的偏振态在传输过程中易受光纤中的应力双折射和偏振模色散等因素的影响以及环境的干扰，一般需要进行偏振补偿或者其他能够确保偏振稳定的方法。相位调制是指利用光的相位来编码信息。量子通信的相位调制原理上主要是基于Mach-Zehnder干涉仪，核心器件是相位调制器。最早提出的相位调制方案是基于单个等臂M-Z干涉仪。由于受环境影响，两臂的臂长差会不稳定，相位差也就会产生漂移，干涉效果就会受到严重影响，尤其对于较长距离的传输，干涉效果更差。后来，人们提出了双不等臂M-Z干涉系统，光纤重合部分上的时间扰动对两个脉冲的影响相同，干涉稳定性有了很大的提高。然而，即使使用双不等臂M-Z干涉仪，臂长的微小变化也会引起干涉对比度下降。
M-Z干涉仪QKD系统一般采用的是BB84协议、B92协议，系统的安全性基于Eve不能确切知道合法通信方对信息进行的编码和探测时使用的基。另一方面，采用BB84协议、B92协议的系统，在最终形成密码时，要进行编码基与测量基的比对，因此协议效率不高，成码率低，尚不能满足实际应用需求。差分相位编码继承了相位编码方案编码速度快、抗干扰能力强和极限传输距离远的优点，适合实现于光纤线路中，对码生成效率有很大的提高。差分相位编码利用前后两个脉冲差携带信息，脉冲在光纤中会经历相同的相位和偏振变化，对光纤中的各种干扰不敏感，从而提高了系统的稳定性。
2006年唐志列等人发表的《位相调制偏振态的量子编码器和解码器及其应用》提出了一种新的相位调制偏振编码的量子密钥分发方法，虽然具有较高的稳定性，但其进行的六态量子编码器和解码器的量子保密通信光子利用率较低。2014年12月王金东等人发表的《相位调制偏振编码的四态量子编码器和解码器及量子密钥分发系统》，通过相位调制器调制某一线偏振光的相位从而达到改变两线偏光相位差，最后实现偏振编码，也只是利用偏振这一单自由度作为信息载体进行的量子传输。而轨道角动量具有多自由度，能够实现高维量 子信息的编码。但轨道角动量多自由度调制主要应用于量子自由空间通信、经典多通道高速通信。
基于上述现有技术的现状，有待开发一种相位偏振多自由度调制QKD网络系统，实现一对多的通信。且各用户相对独立，保证单用户的密钥生成率稳定，不会随着用户的增加而减小，从而实现量子密钥分发网络系统安全、稳定、高效的传输。
发明内容
本发明目的是克服现有技术的不足，提出一种相位偏振多自由度调制QKD网络系统及方法。该相位偏振多自由度调制QKD网络系统及方法，通过单光源多波长激光器产生的多波长脉冲作为多用户信息传输载体，将各个波长脉冲发送到不同的合法用户，实现一对多的通信。且各用户相对独立，保证单用户的密钥生成率稳定，不会随着用户的增加而减小。从而实现量子密钥分发网络系统安全、稳定、高效的传输。另外，该相位偏振多自由度调制的多用户量子密钥分发网络系统采用一种新的量子信息编码方式，即采用差分相位编码同时偏振编码的方式，能有效减少因外界条件不稳定带来的误码率，提高系统的安全性和稳定性，并且将光子利用率由原来的0.5提高到2。改进了现有的差分相位与偏振编码复合QKD方案，提高了量子密钥生成率，缩短了每次通信时隙等待时间。
该系统将单光源多波长激光器、衰减器、偏振分束器、合束器、相位调制器、偏振控制器作为多用户信息传输的载体。其中经过上下两臂前后脉冲具有的相位差加载一个信息比特，同时脉冲偏振态加载另一个信息比特。通过波分复用单元将各个波长脉冲发送到不同的合法用户，进行相应的偏振解调和相位解调。各用户相对独立，保证单用户的密钥生成率稳定。
为达到上述目的，本发明采用的技术方案如下：
一种相位偏振多自由度调制QKD网络系统，包括Alice控制端、波分复用单元和多用户Bob端，Alice端通过波分复用单元与多用户Bob端连接，
所述Alice端包括多波长激光产生装置、衰减器、第一偏振分束器、第一合束器、相位调制器、第一偏振控制器和第二偏振控制器；
所述波分复用单元包括波长选择装置；
所述多用户Bob端包括接收不同波长的若干单元Bob用户端，所述单元Bob用户端均包括第二偏振分束器、第三偏振控制器、第四偏振控制器、第三偏振分束器、第四偏振分束器、第二合束器、第三合束器、第一光子探测器、第二光子探测器、第三光子探测器和 第四光子探测器；
所述多波长激光产生装置产生具有多个波长的脉冲串，然后经所述衰减器衰减为单光子脉冲，单光子脉冲经过所述第一偏振分束器分成垂直偏振和水平偏振脉冲，所述垂直偏振和水平偏振脉冲分别通过上臂路径和下臂路径进入到所述第一合束器合束；再经过所述相位调制器对脉冲随机调制kπ(k＝0，1)相位分别到达第一偏振控制器和第二偏振控制器进行脉冲偏振旋转，最后两脉冲以相同的偏振态进入Bob端；
具有相同偏振的多波长激光脉冲传输到波长路由装置，根据波长寻址的方式选择相应波长的单元Bob用户端，经过所述单元Bob用户端的第二偏振分束器，进行偏振解调，当偏振比特为“0”时，选择水平偏振脉冲经过所述第三偏振控制器；当偏振比特为“1”时，选择垂直偏振脉冲经过所述第四偏振控制器；
从第三偏振控制器输出后，经过所述第三偏振分束器形成上臂路径和下臂路径两条路径：其中上臂路径：前脉冲经过延时到达所述第二合束器；下臂路径：后脉冲直接到达所述第二合束器，上臂路径和下臂路径的两束光在所述第二合束器处发生干涉，然后根据随机调制的相位差所述第一光子探测器和第二光子探测器做出识别响应；
从第四偏振控制器输出后，经过所述第四偏振分束器形成上臂路径和下臂路径两条路径：其中上臂路径：前脉冲经过延时到达所述第三合束器；下臂路径：后脉冲直接到达所述第三合束器，上臂路径和下臂路径的两束光在所述第三合束器处发生干涉，然后根据随机调制的相位差所述第三光子探测器和第四光子探测器做出识别响应。
优选地，所述上臂路径比下臂路径多了一个T的延时。
优选地，所述第一偏振控制器将脉冲偏振旋转
Figure PCTCN2017117394-appb-000001
所述第二偏振控制器将脉冲偏振旋转
Figure PCTCN2017117394-appb-000002
其中n的取值分别为“0”或“1”。
优选地，所述波长路由装置为波分复用器、阵列波导光栅、布拉格光栅或者波长选择开关。
优选地，所述的多波长激光产生装置包括多波长脉冲激光器和波长选择器，所述多波长脉冲激光器产生满足多个单元Bob用户端同时通信的相干多波长脉冲激光，然后通过所述波长选择器进行选择，使相应波长的单元Bob用户端选择相应波长的脉冲激光。
优选地，所述波长选择器采用二级等差频率间隔的方式选择波长。
优选地，所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器 依据脉冲的相位差做出响应为：当两个连续脉冲的相位差为0时，所述第一探测器响应，测量结果为“00”，第二探测器响应，测量结果“01”；当两个连续脉冲的相位差为π时，所述第三探测器响应，测量结果为“10”，第四探测器响应，测量结果为“11”。
优选地，所述单元Bob用户端为Bobn，其中n为非零自然数。
一种应用上述的相位偏振多自由度调制QKD网络系统的方法，包括以下步骤：
S1.硬件配置初始化：检查Alice端和各个单元Bob用户端的软硬件设施，查看设备是否能正常运转，设定正确的工作电压和适宜的工作温度；
S2.系统噪声测试：在Alice端不发射激光脉冲串的前提下，即脉冲串数为零时，测试系统噪声水平；
S3.光纤长度测试及脉冲延时设置：所述Alice端发送一组脉冲，各个单元Bob用户端通过测量脉冲到达时刻，确定链路中光纤的长度，根据各个单元Bob用户端与Alice端之间的长度关系，预设各个单元Bob用户端的光纤长度，设置各个单元Bob用户端的上臂路径与下臂路径之间的延时；
S4.波长寻址:所述波长选择器根据波长分配规划挑选适合于各个单元Bob用户端使用的波长脉冲，不同波长的脉冲光被分配进入对应的单元Bob用户端，进行一对多的网络通信；
S5.密钥发送：所述多波长脉冲产生装置产生脉冲，脉冲周期大于延时T；经过所述衰减器后衰减到单光子水平，然后通过所述第一偏振分束器分别进入上臂路径和下臂路径形成延时为T的两个脉冲，到达第一合束器合束，接着依次经过所述相位调制器、第一偏振调制器和第二偏振调制其进行相位偏振调制，使它们以相同的偏振态传输最后经过各个单元Bob用户端进行偏振解调和相位解调；
S6.密钥筛选与成码：各个单元Bob用户端记录探测器的响应，并且记录所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器响应的时刻，将所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器响应的时刻发送到所述Alice端，所述Alice端根据各个单元Bob用户端发送的数据，保留相应的密钥串，其余舍去。
优选地，各个单元Bob用户端之间存在密钥共享：
当安全密钥优先权为：Bobi>Bobj时，Bobj共享Bobi的密钥，Alice端作为中间节点，首先使用Alice端与Bobj的密钥对Alice端与Bobi的密钥进行加密，然后将加密的Bobi密钥发送给Bobj，Bobj收到密文后解密，得到Bobi的密钥，这样便与Bobi共享了密钥；
各个单元Bob用户端之间的密钥共享具有排他性：某一单元Bob用户端的密钥只能与一个单元Bob用户端进行共享，共享之后不能再与其他的单元Bob用户端共享。
本发明的有益效果：1.本发明采用相位偏振多自由度调制QKD网络系统及密钥分发方法，能够实现一对多的量子密钥共享，有效地扩大了信息传递容量，适用于相位偏振多自由度调制QKD方案及其它QKD方案。
2.本发明采用相位和偏振联合调制方法，通过传递一个光子来实现传递两个信息比特，光子利用率由0.5提高到2；与现有方案相比，本方案减少了器件使用，简化结构，并提高了信息的连续性、有效性和密钥生成率。
3.本发明采用4个电子探测器每次通信在8个时隙等待测量，相比于现有方案每次通信在12个时隙等待测量，由探测器暗计数引起的误码率减小了33.3％，使系统更加高效稳定。本发明采用经典DPS量子密钥分发方式，通过编码间隔为T(即延时T，T为皮秒量级)的两支路相干脉冲的相位差，使每个相位差作为一个相位编码，可有效抵御分光子攻击和序列攻击，降低窃听者Eve的效率。
附图说明
图1为本发明的波分复用单元与多用户Bob端的结构框图；
图2为本发明的Alice端相位调制、偏振调制结构框图；
图3为本发明的Bob端偏振解调、相位解调结构框图；
图4为本发明的工作原理框图；
图5为本发明的工作流程图。
图中各部件名称对应标号：公共光纤-101，波长路由装置-102，专用光纤-103、104、105；
多波长激光器-201、衰减器-202、第一偏振分束器-203、第一合束器-204、相位调制器-205、第一偏振控制器-206，第二偏振控制器-207；
第二偏振分束器-301、第三偏振控制器-302、第四偏振控制器-307、第三偏振分束器-303、第四偏振分束器-308、第二合束器-304、第三合束器-309、第一光子探测器-305、第二光子探测器-306、第三光子探测器-310，第四光子探测器-311。
具体实施方式
附图仅用于示例性说明，不能理解为对本专利的限制；
下面结合附图和实施例对本发明的技术方案做进一步的说明。
本发明是一种点对多点的组网方式，特别地可以进一步延伸到多点对多点的方式。所描述的实施例只是本发明一对多方式中的一种，显然地，它可以较易地扩展到更多应用，一个较具代表性的波分复用量子密钥分发网络示意图如图1所示。
如图1-图4所示，一种相位偏振多自由度调制QKD网络系统，包括Alice控制端、波分复用单元和多用户Bob端，Alice端通过波分复用单元与多用户Bob端连接。
所述Alice端包括多波长激光产生装置201、衰减器202、第一偏振分束器203、第一合束器204、相位调制器205、第一偏振控制器206和第二偏振控制器207；
所述波分复用单元包括波长选择装置；
所述多用户Bob端包括接收不同波段的若干单元Bob用户端，所述单元Bob用户端均包括第二偏振分束器301、第三偏振控制器302、第四偏振控制器307、第三偏振分束器303、第四偏振分束器308、第二合束器304、第三合束器309、第一光子探测器305、第二光子探测器306、第三光子探测器310和第四光子探测器311；
本系统的工作过程如下：
所述多波长激光产生装置产生具有多个波长的脉冲串，然后经所述衰减器202衰减为单光子脉冲，单光子脉冲经过所述第一偏振分束器203分成垂直偏振和水平偏振脉冲，所述垂直偏振和水平偏振脉冲分别通过上臂路径和下臂路径进入到所述第一合束器204合束；再经过所述相位调制器205对脉冲随机调制kπ(k＝0，1)相位分别到达第一偏振控制器206和第二偏振控制器207进行脉冲偏振旋转，最后两脉冲以相同的偏振态进入Bob端；
具有相同偏振的多波长激光脉冲传输到波长路由装置102，根据波长寻址的方式选择相应波长的单元Bob用户端，经过所述单元Bob用户端的第二偏振分束器301，进行偏振解调，当偏振比特为“0”时，选择水平偏振脉冲经过所述第三偏振控制器302；当偏振比特为“1”时，选择垂直偏振脉冲经过所述第四偏振控制器307；
从第三偏振控制器输出后，经过所述第三偏振分束器303形成上臂路径和下臂路径两条路径：其中上臂路径：前脉冲经过延时到达所述第二合束器304；下臂路径：后脉冲直接到达所述第二合束器304，上臂路径和下臂路径的两束光在所述第二合束器304处发生干涉，然后根据随机调制的相位差所述第一光子探测器305和第二光子探测器306做出识别响应；
从第四偏振控制器307输出后，经过所述第四偏振分束器308形成上臂路径和下臂路径两条路径：其中上臂路径：前脉冲经过延时到达所述第三合束器309；下臂路径：后脉冲直接到达所述第三合束器309，上臂路径和下臂路径的两束光在所述第三合束器309处发生 干涉，然后根据随机调制的相位差所述第三光子探测器310和第四光子探测器311做出识别响应。
下面结合附图和实施例对本发明的技术方案做进一步的说明。
本发明是一种点对多点的组网方式，特别地可以进一步延伸到多点对多点的方式。所描述的实施例只是本发明一对多方式中的一种，显然地，它可以较易地扩展到更多应用，一个较具代表性的波分复用量子密钥分发网络示意图如图1所示。
图1中，Alice端作为脉冲信号的发射方，拥有一个多波长光源，能够产生满足多个单元Bob用户端同时通信使用的不同波段的脉冲信号。每个单元Bob用户端可以分配到某一波长的信号，且其对脉冲波长具有较宽适用性，即在波长规划过程中调整各单元Bob用户端之间信号波长的分配后，各单元Bob用户端仍然可以正常工作。图1中公共光纤101为各用户共同使用，光纤103、104和105为每个用户的专用光纤，每个用户的专用光纤和共用光纤101之和定义为每个用户的距离。波长路由装置102用在控制端Alice和用户端Bob之间，控制各波长脉冲信号的路径选择。
图2，本发明相位偏振多自由度调制QKD网络系统及方法Alice端的实施例示意图。该系统Alice端对单光子进行相位调制和偏振调制。
下面具体地描述调制过程:
偏振态为
Figure PCTCN2017117394-appb-000003
的45°泵浦光，衰减为单光子脉冲F(x，t)|π/4＞,其中
Figure PCTCN2017117394-appb-000004
为高斯脉冲。该单光子脉冲经过第一偏振分束器203被分为两路脉冲，两路脉冲具有T的延时。当延时为T的两脉冲通过相位调制器PM(θi＝kπ,k取值“0”或“1”)后，脉冲形式分别变为
Figure PCTCN2017117394-appb-000005
第一偏振控制器(PC1)206对延时脉冲偏振旋转
Figure PCTCN2017117394-appb-000006
Figure PCTCN2017117394-appb-000007
此时脉冲为
Figure PCTCN2017117394-appb-000008
第二偏振控制器(PC2)207对短路脉冲偏振旋转
Figure PCTCN2017117394-appb-000009
此时脉冲为
Figure PCTCN2017117394-appb-000010
n取值“0”或“1”。
所述多波长激光器201产生具有多个波长(λ1、λ2、λ3……λn)的脉冲串，其中所产生的多波长脉冲激光偏振为45°，脉冲周期大于延时T，经衰减器202衰减为单光子脉冲；单光子脉冲经过第一偏振分束器203分成水平偏振和垂直偏振的脉冲，分别进入上臂途径和下臂途径，其中上臂途径比下臂途径脉冲经过T的延时。随后两脉冲通过相位调制器205，相位调制器205对两脉冲随机调制kπ的相位(k取0或者1)。当两个脉冲同时到达第一偏振控制器206和第二偏振控制器207时(即两偏振控制器间的间距产生T的延时)，第一偏 振控制器206将脉冲偏振旋转
Figure PCTCN2017117394-appb-000011
第二偏振控制器207将脉冲偏振旋转
Figure PCTCN2017117394-appb-000012
其中n的取值分别为“0”或“1”。此时，两脉冲以相同的偏振态经光纤传输进入多用户Bob端。
图3，本发明相位偏振多自由度调制QKD网络系统及方法Bob端的实施例示意图。以Bob1为例，对Bob1端进行偏振解调和相位解调。
下面具体地描述解调过程:
当n＝0时，两脉冲光经过第三偏振控制器PC3，脉冲形式变为
Figure PCTCN2017117394-appb-000013
Figure PCTCN2017117394-appb-000014
此时垂直偏振光经过延时T，变为
Figure PCTCN2017117394-appb-000015
脉冲
Figure PCTCN2017117394-appb-000016
与
Figure PCTCN2017117394-appb-000017
合束。
当时，第一光子探测器D1响应，此时对应密钥为“00”；
当时，第二光子探测器D2响应，此时对应密钥为“01”。
同理，n＝1时，若第三光子探测器D3响应，对应的密钥为“10”；若第四光子探测器响应，对应的密钥为“11”。
当n取“0”时，时间间隔为T的两个脉冲以水平偏振态经过第二偏振分束器301进入第三偏振控制器302；当n取“1”时，时间间隔为T的两个脉冲以垂直偏振态经过第二偏振分束器301进入偏振控制器307。第三偏振控制器302只将快轴脉冲偏振旋转
Figure PCTCN2017117394-appb-000018
变为垂直偏振；垂直偏振脉冲经过第三偏振分束器303反射，经过延时T进入第二合束器304；水平偏振脉冲经过第三偏振分束器303直接透射进入第二合束器304。第四偏振控制器307只将慢轴脉冲偏振旋转
Figure PCTCN2017117394-appb-000019
变为水平偏振；水平偏振脉冲经过第四偏振分束器308直接透射进入第三合束器309；垂直偏振脉冲经过第四偏振分束器308反射，经过延时T进入第三合束器309。在第二合束器304相遇的两个脉冲光发生干涉，依据随机调制的相位差0或π，第一光子探测器305或第二光子探测器306做出响应。同理，在第三合束器309相遇的两个脉冲光发生干涉，依据随机调制的相位差0或π，第三光子探测器310或第四探测器311做出响应。
图4，相位偏振多自由度调制QKD网络系统及方法工作原理框图，包括Alice控制端、波分复用单元和多用户Bob端，Alice端通过波分复用单元与多用户Bob端连接。其中Alice端对单光子分别相位调制和偏振调制，经量子信道进入多用户单元Bob端偏振解调和相位解调。具体的调制解调过程在图2、图3已详细说明，这里不再赘述。
图5，一种应用于上述相位偏振多自由度调制QKD网络系统的密钥分发方法，包括以下 步骤：
S1.硬件配置初始化：检查Alice端和各个单元Bob用户端的软硬件设施，查看设备是否能正常运转，设定正确的工作电压和适宜的工作温度；
S2.系统噪声测试：在Alice端不发射激光脉冲串的前提下，即脉冲串数为零时，测试系统噪声水平；
S3.光纤长度测试及脉冲延时设置：所述Alice端发送一组脉冲，各个单元Bob用户端通过测量脉冲到达时刻，确定链路中光纤的长度，根据各个单元Bob用户端与Alice端之间的长度关系，预设各个单元Bob用户端的光纤长度，设置各个单元Bob用户端的上臂路径与下臂路径之间的延时；
S4.波长寻址:所述波长选择器根据波长分配规划挑选适合于各个单元Bob用户端使用的波长脉冲，不同波长的脉冲光被分配进入对应的单元Bob用户端，进行一对多的网络通信；
S5.密钥发送：所述多波长脉冲产生装置产生脉冲，脉冲周期大于延时T；经过所述衰减器后衰减到单光子水平，然后通过所述第一偏振分束器分别进入上臂路径和下臂路径形成延时为T的两个脉冲，到达第一合束器合束，接着依次经过所述相位调制器、第一偏振调制器和第二偏振调制其进行相位偏振调制，使它们以相同的偏振态传输最后经过各个单元Bob用户端进行偏振解调和相位解调；
S6.密钥筛选与成码：各个单元Bob用户端记录探测器的响应，并且记录所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器响应的时刻，将所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器响应的时刻发送到所述Alice端，所述Alice端根据各个单元Bob用户端发送的数据，保留相应的密钥串，其余舍去。
各个单元Bob用户端之间存在密钥共享：
当安全密钥优先权为：Bobi>Bobj时，Bobj共享Bobi的密钥，Alice端作为中间节点，首先使用Alice端与Bobj的密钥对Alice端与Bobi的密钥进行加密，然后将加密的Bobi密钥发送给Bobj，Bobj收到密文后解密，得到Bobi的密钥，这样便与Bobi共享了密钥；
各个单元Bob用户端之间的密钥共享具有排他性：某一单元Bob用户端的密钥只能与一个单元Bob用户端进行共享，共享之后不能再与其他的单元Bob用户端共享。
本发明的有益效果：1.本发明采用的相位偏振多自由度调制QKD网络系统，能够实现一对多的量子密钥共享，有效地扩大了信息传递容量，适用于相位偏振多自由度调制QKD 方案及其它QKD方案。
2.本发明采用相位和偏振联合调制方法，通过传递一个光子来实现传递两个信息比特，光子利用率由0.5提高到2；与现有方案相比，本方案减少了器件使用，简化结构，并提高了信息的连续性、有效性和密钥生成率。
3.本发明采用4个电子探测器每次通信在8个时隙等待测量，相比于现有方案每次通信在12个时隙等待测量，由探测器暗计数引起的误码率减小了33.3％，使系统更加高效稳定。本发明采用经典DPS量子密钥分发方式，通过编码间隔为T(即延时T，T为皮秒量级)的两支路相干脉冲的相位差，使每个相位差作为一个相位编码，可有效抵御分光子攻击和序列攻击，降低窃听者Eve的效率。
附图中描述位置关系仅用于示例性说明，不能理解为对本专利的限制。
显然，本发明的上述实施例仅仅是为了清楚地说明本发明所作的举例，而并非是对本发明的实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动。这里无需也无法对所有的实施方式予以穷举。凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明权利要求的保护范围之内。

Claims (10)

  1. 一种相位偏振多自由度调制QKD网络系统，包括Alice控制端、波分复用单元和多用户Bob端，Alice端通过波分复用单元与多用户Bob端连接，其特征在于：
    所述Alice端包括多波长激光产生装置、衰减器、第一偏振分束器、第一合束器、相位调制器、第一偏振控制器和第二偏振控制器；
    所述波分复用单元包括波长选择装置；
    所述多用户Bob端包括接收不同波段的若干单元Bob用户端，所述单元Bob用户端均包括第二偏振分束器、第三偏振控制器、第四偏振控制器、第三偏振分束器、第四偏振分束器、第二合束器、第三合束器、第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器；
    所述多波长激光产生装置产生具有多个波长的脉冲串，然后经所述衰减器衰减为单光子脉冲，单光子脉冲经过所述第一偏振分束器分成垂直偏振和水平偏振脉冲，所述垂直偏振和水平偏振脉冲分别通过上臂路径和下臂路径进入到所述第一合束器合束；再经过所述相位调制器对脉冲随机调制kπ(k＝0，1)相位分别到达第一偏振控制器和第二偏振控制器进行脉冲偏振旋转，最后两脉冲以相同的偏振态进入所述多用户Bob端；
    具有相同偏振的多波长激光脉冲传输到波长路由装置，根据波长寻址的方式选择相应波长的单元Bob用户端，经过所述单元Bob用户端的第二偏振分束器，进行偏振解调，当偏振比特为“0”时，选择水平偏振脉冲经过所述第三偏振控制器；当偏振比特为“1”时，选择垂直偏振脉冲经过所述第四偏振控制器；
    从第三偏振控制器输出后，经过所述第三偏振分束器形成上臂路径和下臂路径两条路径：其中上臂路径：前脉冲经过延时到达所述第二合束器；下臂路径：后脉冲直接到达所述第二合束器，上臂路径和下臂路径的两束光在所述第二合束器处发生干涉，然后根据随机调制的相位差所述第一光子探测器和第二光子探测器做出识别响应；
    从第四偏振控制器输出后，经过所述第四偏振分束器形成上臂路径和下臂路径两条路径：其中上臂路径：前脉冲经过延时到达所述第三合束器；下臂路径：后脉冲直接到达所述第三合束器，上臂路径和下臂路径的两束光在所述第三合束器处发生干涉，然后根据随机调制的相位差所述第三光子探测器和第四光子探测器做出识别响应。
  2. 如权利要求1所述的一种相位偏振多自由度调制QKD网络系统，其特征在于，所述上臂路径比下臂路径多了一个T的延时。
  3. 如权利要求1所述的一种相位偏振多自由度调制QKD网络系统，其特征在于，所述 第一偏振控制器将脉冲偏振旋转
    Figure PCTCN2017117394-appb-100001
    所述第二偏振控制器将脉冲偏振旋转
    Figure PCTCN2017117394-appb-100002
    其中n的取值分别为“0”或“1”。
  4. 如权利要求1所述的相位偏振多自由度调制QKD网络系统，其特征在于，所述波长路由装置为波分复用器、阵列波导光栅、布拉格光栅或者波长选择开关。
  5. 如权利要求1所述的相位偏振多自由度调制QKD网络系统，其特征在于，所述的多波长激光产生装置包括多波长脉冲激光器和波长选择器，所述多波长脉冲激光器产生满足多个单元Bob用户端同时通信的相干多波长脉冲激光，然后通过所述波长选择器进行选择，使各个单元Bob用户端选择相应波长的脉冲激光。
  6. 如权利要求5所述的相位偏振多自由度调制QKD网络系统，其特征在于，所述波长选择器采用二级等差频率间隔的方式选择波长。
  7. 如权利要求1所述的相位偏振多自由度调制QKD网络系统，其特征在于，所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器依据脉冲的相位差做出响应为：当两个连续脉冲的相位差为0时，所述第一探测器响应，测量结果为“00”，第二探测器响应，测量结果“01”；当两个连续脉冲的相位差为π时，所述第三探测器响应，测量结果为“10”，第四探测器响应，测量结果为“11”。
  8. 如权利要求1所述的相位偏振多自由度调制QKD网络系统，其特征在于，所述单元Bob用户端为Bobn，其中n为非零自然数。
  9. 一种应用权利要求1-8任一项所述的相位偏振多自由度调制QKD网络系统及方法，其特征在于，包括以下步骤：
    S1.硬件配置初始化：检查Alice端和各个单元Bob用户端的软硬件设施，查看设备是否能正常运转，设定正确的工作电压和适宜的工作温度；
    S2.系统噪声测试：在Alice端不发射激光脉冲串的前提下，即脉冲串数为零时，测试系统噪声水平；
    S3.光纤长度测试及脉冲延时设置：所述Alice端发送一组脉冲，各个单元Bob用户端通过测量脉冲到达时刻，确定链路中光纤的长度，根据各个单元Bob用户端与Alice端之间的长度关系，预设各个单元Bob用户端的光纤长度，设置各个单元Bob用户端的上臂路径与下臂路径之间的延时；
    S4.波长寻址:所述波长选择器根据波长分配规划挑选适合于各个单元Bob用户端使用的波长脉冲，不同波长的脉冲光被分配进入对应的单元Bob用户端，进行一对多的网络通信；
    S5.密钥发送：所述多波长脉冲产生装置产生脉冲，脉冲周期大于延时T；经过所述衰减器后衰减到单光子水平，然后通过所述第一偏振分束器分别进入上臂路径和下臂路径形成延时为T的两个脉冲，到达第一合束器合束，接着依次经过所述相位调制器、第一偏振调制器和第二偏振调制其进行相位偏振调制，使它们以相同的偏振态传输最后经过各个单元Bob用户端进行偏振解调和相位解调；
    S6.密钥筛选与成码：各个单元Bob用户端记录探测器的响应，并且记录所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器响应的时刻，将所述第一光子探测器、第二光子探测器、第三光子探测器和第四光子探测器响应的时刻发送到所述Alice端，所述Alice端根据各个单元Bob用户端发送的数据，保留相应的密钥串，其余舍去。
  10. 如权利要求9所述的一种相位偏振多自由度调制量子密钥分发方法，其特征在于，各个单元Bob用户端之间存在密钥共享：
    当安全密钥优先权为：Bobi>Bobj时，Bobj共享Bobi的密钥，Alice端作为中间节点，首先使用Alice端与Bobj的密钥对Alice端与Bobi的密钥进行加密，然后将加密的Bobi密钥发送给Bobj，Bobj收到密文后解密，得到Bobi的密钥，这样便与Bobi共享了密钥；
    各个单元Bob用户端之间的密钥共享具有排他性：某一单元Bob用户端的密钥只能与一个单元Bob用户端进行共享，共享之后不能再与其他的单元Bob用户端共享。
PCT/CN2017/117394 2017-01-16 2017-12-20 一种相位偏振多自由度调制qkd网络系统及方法 WO2018130052A1 (zh)

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US16/314,858 US11070370B2 (en) 2017-01-16 2017-12-20 Phase and polarization multi-degree-of-freedom modulated QKD network system and method
AU2017392255A AU2017392255B2 (en) 2017-01-16 2017-12-20 Phase and polarization multi-degree-of-freedom modulated qkd network system and method
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