WO2021128557A1 - 量子通信光路系统和量子通信方法 - Google Patents

量子通信光路系统和量子通信方法 Download PDF

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Publication number
WO2021128557A1
WO2021128557A1 PCT/CN2020/076326 CN2020076326W WO2021128557A1 WO 2021128557 A1 WO2021128557 A1 WO 2021128557A1 CN 2020076326 W CN2020076326 W CN 2020076326W WO 2021128557 A1 WO2021128557 A1 WO 2021128557A1
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optical signal
optical
polarization
signal pulse
sub
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PCT/CN2020/076326
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English (en)
French (fr)
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龙桂鲁
殷柳国
戚若阳
张浩然
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清华大学
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Publication of WO2021128557A1 publication Critical patent/WO2021128557A1/zh
Priority to US17/844,064 priority Critical patent/US20220321234A1/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
    • 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
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
    • 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
    • H04B10/506—Multiwavelength 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
    • H04B10/70—Photonic quantum communication

Definitions

  • This application relates to the field of quantum communication, and in particular to a quantum communication optical system and a quantum communication method.
  • Quantum communication refers to a new type of communication method that uses quantum entanglement effects for information transmission.
  • the most commonly used encoding methods are phase encoding and polarization encoding.
  • quantum communication based on phase encoding is a secure communication method that can be stably transmitted in optical fibers.
  • the two-way quantum communication in the quantum communication optical system requires the optical signal to return along the original path for decoding.
  • the electro-optical modulator will interfere with the optical signal of the loop, which in turn causes the problem of serial mode in the optical signal circuit of the dual-channel quantum communication system.
  • the quantum communication optical path system includes a light source module, an intensity polarization modulation module, a polarization maintaining interference ring, a phase intensity modulation module, a first isolator, a first polarization beam splitter, a second isolator, a beam splitter, and a second polarization splitter. Beamer, 90° Faraday rotator and second phase modulator.
  • the input end of the intensity polarization modulation module is connected to the output end of the light source module, and is used for intensity modulation and polarization modulation of the optical signal pulse.
  • the first end of the polarization-maintaining interference ring is connected to the output end of the intensity polarization modulation module.
  • the input end of the phase intensity modulation module is connected to the third end of the polarization-maintaining interference ring, and is used for phase modulation and intensity modulation of the optical signal pulse passing through the polarization-maintaining interference ring.
  • the input terminal of the first isolator is connected to the output terminal of the intensity modulation module.
  • the first end of the first polarization beam splitter is connected to the output end of the first isolator.
  • the input end of the second isolator is connected to the third end of the first polarization beam splitter, and the output end of the second isolator is connected to the fourth end of the polarization-maintaining interference ring.
  • the first end of the beam splitter and the second end of the first polarization beam splitter are connected through a communication channel.
  • the first end of the second polarization beam splitter is connected to the third end of the beam splitter.
  • the first end of the second phase modulator is connected to the second end of the second polarization beam splitter.
  • the first end of the 90° Faraday rotator is connected to the second end of the second phase modulator.
  • the second end of the 90° Faraday rotator is connected to the third end of the second polarization beam splitter.
  • the quantum communication optical path system further includes a first single photon detector.
  • the first single-photon detector is connected to the second end of the polarization-maintaining interference ring.
  • the quantum communication optical path system further includes a second single-photon detector.
  • the second single-photon detector is connected to the second end of the beam splitter.
  • the quantum communication optical path system further includes an optical circulator.
  • the first end of the optical circulator is connected to the output end of the intensity polarization modulation module, and the second end of the optical circulator is connected to the first end of the polarization-maintaining interference ring.
  • the quantum communication optical path system further includes a third single-photon detector.
  • the third single-photon detector is connected to the third end of the optical circulator.
  • the intensity polarization modulation module includes an adjustable attenuator, a polarization modulator, and a third polarization beam splitter.
  • the input end of the adjustable attenuator is connected to the output end of the light source module.
  • the input end of the polarization modulator is connected to the output end of the adjustable attenuator.
  • the input end of the third polarization beam splitter is connected to the output end of the polarization modulator.
  • the output end of the third polarization beam splitter is connected to the first end of the optical circulator.
  • the phase intensity modulation module includes a first phase modulator.
  • the input end of the first phase modulator is connected to the third end of the polarization-maintaining interference loop, and the output end of the first phase modulator is connected to the input end of the first isolator.
  • the phase intensity modulation module further includes an intensity modulator.
  • the input end of the intensity modulator is connected to the output end of the first phase modulator, and the output end of the intensity modulator is connected to the input end of the first isolator.
  • the quantum communication optical path system further includes a polarization maintaining fiber.
  • the light source module, the intensity polarization modulation module, the polarization maintaining interference ring, the phase intensity modulation module, the first isolator, and the first polarization beam splitter are connected by the polarization maintaining fiber .
  • this application provides a quantum communication method, including:
  • the receiving end provides an optical signal pulse, and performs intensity modulation and polarization modulation on the optical signal pulse;
  • S30 Perform phase modulation and intensity modulation on the first optical signal pulse and the second optical signal pulse, respectively, and combine the phase modulation and intensity modulation on the first optical signal pulse and the second optical signal The pulse is transmitted to the sender through the communication channel;
  • S50 Perform security detection according to the first detected optical signal, and divide the second optical signal into two second sub-optical signals;
  • S60 Perform security detection according to the third detection optical signal, and divide the fourth optical signal into two fourth sub optical signals;
  • S70 Perform phase modulation and polarization rotation of one of the second optical sub-signals by 90° in sequence to form a first sub-detection optical signal among the two second optical sub-signals, and perform the other second sub-optical signal in sequence.
  • the polarization state is rotated by 90° and the phase is modulated to form a second sub-detection light signal, and the first sub-detection light signal and the second sub-detection light signal are combined into a first detection light signal pulse;
  • S80 Perform phase modulation and polarization rotation of one of the fourth sub-optical signals by 90° in sequence to form a third sub-detection optical signal among the two fourth sub-optical signals, and perform the other fourth sub-optical signal in sequence.
  • the polarization state is rotated by 90° and the phase is modulated to form a fourth sub-detection light signal, and the third sub-detection light signal and the fourth sub-detection light signal are combined into a second detection light signal pulse;
  • S90 Transmit the first detection light signal pulse and the second detection light signal pulse to the receiving end through a communication channel for detection, and reversely decode the code modulation performed by the transmitting end.
  • the intensity modulation of the first optical signal pulse and the second optical signal pulse includes:
  • the first optical signal pulse is eliminated, and the second optical signal pulse remains unchanged.
  • the intensity modulation of the first optical signal pulse and the second optical signal pulse includes:
  • the first optical signal pulse remains unchanged, and the second optical signal pulse is eliminated.
  • the intensity modulation of the first optical signal pulse and the second optical signal pulse includes:
  • the light intensity of the first optical signal pulse is eliminated by half, and the light intensity of the second optical signal pulse is eliminated by half.
  • the phase modulation of the first optical signal pulse and the second optical signal pulse includes:
  • the phase modulation of the first optical signal pulse and the second optical signal pulse includes:
  • the phase modulation of the first optical signal pulse and the second optical signal pulse includes:
  • performing phase modulation on the two second optical sub-signals and the two fourth optical sub-signals includes:
  • performing phase modulation on the two second optical sub-signals and the two fourth optical sub-signals includes:
  • performing phase modulation on the two second optical sub-signals and the two fourth optical sub-signals includes:
  • performing phase modulation on the two second optical sub-signals and the two fourth optical sub-signals includes:
  • the optical signal pulse is emitted by the Bob end light source.
  • the PMI polarization-maintaining interference ring is divided into two pulses before and after, that is, the first optical signal pulse is the prepulse, and the second pulse is the prepulse.
  • the light signal pulse is the post pulse.
  • the first optical signal pulse (pre-pulse) and the second optical signal pulse (post-pulse) undergo phase modulation and intensity modulation by the phase intensity modulation module, which can be understood as the preprocessing of the pulse signal. Then it is passed to Alice's end via the communication channel.
  • the beam splitter separates part of the optical signal (that is, the first detection optical signal and the third detection optical signal). Light signal), and perform safety inspection.
  • the remaining optical signals i.e., the second optical signal and the fourth optical signal
  • the second polarization beam splitter in the loop the loop formed by the second phase modulator, the second polarization beam splitter and the 90° Faraday rotator.
  • the remaining optical signals (that is, the second optical signal and the fourth optical signal) are phase-encoded through the Faraday rotating mirror and the electro-optical phase modulator in different directions to form the first detection optical signal pulse and the second detection optical signal pulse, and then through communication
  • the channel is passed to Bob's end.
  • the first probe light signal pulse and the second probe light signal pulse After the first probe light signal pulse and the second probe light signal pulse arrive at the Bob end, they will bypass the phase intensity modulation module (intensity modulator and phase modulator) via the first polarization beam splitter and directly reach the PMI polarization-maintaining interference ring. And according to the difference between the phase pre-modulation of the Bob end and the phase encoding of the Alice end, the first detection light signal pulse and the second detection light signal pulse will be transmitted from the first end (port 1) or the second end (port 2) of the PMI polarization-maintaining interference ring. ) Exits and reaches different single-photon detectors. At this time, according to the response of different single-photon detectors and the pre-modulation of the light pulse, the Bob end can reversely decode the code of the light pulse at the Alice end, thereby realizing quantum communication.
  • phase intensity modulation module intensity modulator and phase modulator
  • the second polarization beam splitter passes through the electro-optic phase modulator from two directions along the loop at the same time for encoding, and through the action of the second polarization beam splitter and the 90° Faraday rotator, the optical signal (ie The polarization of the first probe light signal pulse and the second probe light signal pulse) when it returns to the Bob end through the communication channel is exactly 90° different from the polarization when emitted from the Bob end, so that the optical signal (that is, the first probe light signal pulse and the first probe light signal pulse)
  • the second detection optical signal pulse can bypass the phase intensity modulation module (intensity modulator and phase modulator) through the first polarization beam splitter and directly reach the PMI polarization-maintaining interference ring, thereby solving the problem of serial mode in the optical signal loop and greatly improving The modulation speed of the circuit.
  • Fig. 1 is a schematic diagram of a quantum communication optical path system provided by this application.
  • FIG. 2 is a schematic diagram of the optical signal trend of the quantum communication optical path system provided by this application.
  • FIG. 3 is a schematic diagram of optical signal conversion of the quantum communication optical path system provided by this application.
  • Fig. 4 is a schematic diagram of a pre-modulated optical signal in the quantum communication optical path system provided by this application.
  • the quantum communication optical path system 100 includes a light source module 110, an intensity polarization modulation module 120, a polarization maintaining interference ring 140, a phase intensity modulation module 150, a first isolator 170, a first polarization beam splitter 180, a second isolator 190, The beam splitter 210, the second polarization beam splitter 220, the 90° Faraday rotator 230, and the second phase modulator 240.
  • the input end of the intensity polarization modulation module 120 is connected to the output end of the light source module 110, and is used for intensity modulation and polarization modulation of the optical signal pulse.
  • the first end of the polarization-maintaining interference ring 140 is connected to the output end of the intensity polarization modulation module 120.
  • the input end of the phase intensity modulation module 150 is connected to the third end of the polarization-maintaining interference ring 140, and is used for phase modulation and intensity modulation of the optical signal pulse passing through the polarization-maintaining interference ring 140.
  • the input terminal of the first isolator 170 is connected to the output terminal of the phase intensity modulation module 150.
  • the first end of the first polarization beam splitter 180 is connected to the output end of the first isolator 170.
  • the input end of the second isolator 190 is connected to the third end of the first polarization beam splitter 180, and the output end of the second isolator 190 is connected to the fourth end of the polarization maintaining interference ring 140.
  • the first end of the beam splitter 210 and the second end of the first polarization beam splitter 180 are connected through a communication channel.
  • the first end of the second polarization beam splitter 220 is connected to the third end of the beam splitter 210.
  • the first end of the second phase modulator 240 is connected to the second end of the second polarization beam splitter 220.
  • the first end of the 90° Faraday rotator 230 is connected to the second end of the second phase modulator 240.
  • the second end of the 90° Faraday rotator 230 is connected to the third end of the second polarization beam splitter 220.
  • the light source module 110 at the receiving end is used to emit light signal pulses.
  • the input end of the intensity polarization modulation module 120 is connected to the output end of the light source module 110, and is used for intensity modulation and polarization modulation of the optical signal pulse.
  • the first end of the polarization-maintaining interference ring 140 is connected to the output end of the intensity polarization modulation module 120, and is used to divide the optical signal pulse passing through the intensity polarization modulation module 120 into a first optical signal pulse and a second optical signal pulse. Signal pulse.
  • the second optical signal pulse has a time delay with respect to the first optical signal pulse.
  • the input end of the phase intensity modulation module 150 is connected to the third end of the polarization-maintaining interference ring 140, and is used to perform phase modulation and intensity modulation on the first optical signal pulse and the second optical signal pulse, respectively.
  • the input end of the first isolator 170 is connected to the output end of the phase intensity modulation module 150, and is used to block the transmission direction of the intensity-modulated first optical signal pulse and the second optical signal pulse, so that The light path can only pass through in one direction.
  • first optical signal pulse and the second optical signal pulse passing through the first isolator 170 pass through the first polarization beam splitter 180 in one direction, they are transmitted to the transmitting end (Alice end) through the channel. ⁇ 210 ⁇ Beam 210.
  • the first end of the beam splitter 210 is connected to the second end of the first polarization beam splitter 180, and is used to divide the first optical signal pulse transmitted through the channel after the polarization beam splitter 180 into The first detection optical signal and the second optical signal divide the second optical signal pulse transmitted through the channel through the polarization beam splitter 180 into a third detection optical signal and a fourth optical signal.
  • the first end of the second polarization beam splitter 220 is connected to the third end of the beam splitter 210 for dividing the second optical signal into two second optical sub-signals.
  • the fourth optical signal is divided into two fourth sub-optical signals.
  • One of the two second optical sub-signals is transmitted to the second polarization beam splitter 220 through the second phase modulator 240 and the 90° Faraday rotator 230 in sequence.
  • the three ends form the first sub-detection light signal.
  • the other second sub-light signal is transmitted to the second end of the second polarization beam splitter 220 after passing through the 90° Faraday rotator 230 and the second phase modulator 240 to form a second sub-detection light signal.
  • the first sub-detection light signal and the second sub-detection light signal are combined into a first detection light signal pulse after passing through the second polarization beam splitter 220.
  • One of the two fourth optical sub-signals is transmitted to the second polarization beam splitter 220 through the second phase modulator 240 and the 90° Faraday rotator 230 in sequence.
  • the three ends form the third sub-detection light signal.
  • the other fourth sub-optical signal is transmitted to the second end of the second polarization beam splitter 220 through the 90° Faraday rotator 230 and the second phase modulator 240 to form a fourth sub-detection optical signal .
  • the third sub-detection light signal and the fourth sub-detection light signal are combined into a second detection light signal pulse after passing through the second polarization beam splitter 220.
  • the first detection light signal pulse is transmitted through the beam splitter 210 to the second end of the first polarization beam splitter 180 through a channel, and then passes through the first polarization beam splitter 180 and the second polarization beam splitter 180.
  • the isolator 190 is transmitted to the polarization-maintaining interference ring 140 for detection.
  • the second probe light signal pulse is transmitted through the beam splitter 210 to the second end of the first polarization beam splitter 180 through the channel, and then passes through the first polarization beam splitter 180 and the second polarization beam splitter 180.
  • the isolator 190 is transmitted to the polarization-maintaining interference ring 140 for detection.
  • the second isolator 190 is used to block the transmission direction, so that only one direction of the optical path can pass.
  • the optical signal pulse is emitted by the Bob end light source.
  • the PMI polarization-maintaining interference ring 140 is divided into two pulses before and after, that is, the first optical signal pulse is the first pulse. Pulse, the second light signal pulse is the post pulse.
  • the first optical signal pulse (pre-pulse) and the second optical signal pulse (post-pulse) undergo phase modulation and intensity modulation by the phase intensity modulation module 150, which can be understood as preprocessing of the pulse signal. Then it is passed to Alice's end via the communication channel.
  • the beam splitter 210 separates part of the optical signal (that is, the first detection optical signal and the third optical signal). Detect light signal), perform safety inspection.
  • the remaining optical signals that is, the second optical signal and the fourth optical signal
  • the second polarization beam splitter 220 in the loop the second phase modulator 240, the second polarization beam splitter 220, and the 90° Faraday rotator 230.
  • the first detection light signal pulse and the second detection light signal pulse After the first detection light signal pulse and the second detection light signal pulse arrive at the Bob end, they will bypass the phase intensity modulation module 150 (intensity modulator 152 and phase modulator 151) through the first polarization beam splitter 180 and directly reach the PMI polarization maintaining Interference ring 140. And according to the difference between the phase pre-modulation of the Bob end and the phase encoding of the Alice end, the first detection light signal pulse and the second detection light signal pulse will be transmitted from the first end (port 1) or the second end (port 1) of the PMI polarization-maintaining interference ring 140. 2) Exit and reach different single photon detectors. At this time, according to the response of different single-photon detectors and the pre-modulation of the light pulse, the Bob end can reversely decode the code of the light pulse at the Alice end, thereby realizing quantum communication.
  • the second polarization beam splitter 220 passes through the electro-optic phase modulator 240 from two directions along the loop at the same time for encoding, and through the second polarization beam splitter 220 and the 90° Faraday rotator 230,
  • the polarization of the optical signal i.e., the first detection light signal pulse and the second detection light signal pulse
  • the signal pulse and the second detection light signal pulse can pass through the first polarization beam splitter 180 to bypass the phase intensity modulation module 150 (intensity modulator 152 and phase modulator 151) directly to the PMI polarization-maintaining interference ring 140, thereby solving the problem of light
  • the serial mode problem of the signal loop greatly improves the modulation speed of the circuit.
  • the quantum communication optical path system 100 further includes a first single-photon detector 141, a second single-photon detector 250, an optical circulator 130, and a third single-photon detector 131.
  • the first single-photon detector 141 is connected to the second end of the polarization-maintaining interference ring 140.
  • the second single-photon detector 250 is connected to the second end of the beam splitter 210.
  • the first end of the optical circulator 130 is connected to the output end of the intensity polarization modulation module 120, and the second end of the optical circulator 130 is connected to the first end of the polarization-maintaining interference ring 140.
  • the third single-photon detector 131 is connected to the third end of the optical circulator 130.
  • the first single photon detector 141, the second single photon detector 250, and the third single photon detector 131 are used for APD detection.
  • the second single-photon detector 250 is connected to the second end of the beam splitter 210, and is used to transmit the optical signal from the Bob end to the Alice end via a communication channel and is split by the beam splitter 210. The signal is checked for safety.
  • the first single-photon detector 141 is connected to the second end of the polarization-maintaining interference ring 140, and the third single-photon detector 131 is connected to the third end of the optical circulator 130.
  • the first single photon detector 141 and the third single photon detector 131 are used to transmit the optical signal from the Alice end to the Bob end via the communication channel, and bypass the phase intensity modulation module 150 (intensity modulator 152 and After the phase modulator 151) directly reaches the PMI polarization-maintaining interference ring 140, the optical signal emitted through the first port or the second port is detected.
  • the security detection of the quantum communication optical path system 100 is performed on the Alice side, and the decoding and security capacity analysis are performed on the Bob side.
  • the number of particles in the front and rear pulses of the optical signal is used as the orthogonal basis vector for detection safety, and the relative phase of the front and rear pulses is used as the carrier of the load code.
  • the intensity polarization modulation module 120 includes an adjustable attenuator 121, a polarization modulator 122 and a third polarization beam splitter 123.
  • the input end of the adjustable attenuator 121 is connected to the output end of the light source module 110.
  • the input end of the polarization modulator 122 is connected to the output end of the adjustable attenuator 121.
  • the input end of the third polarization beam splitter 123 is connected to the output end of the polarization modulator 122.
  • the output end of the third polarization beam splitter 123 is connected to the first end of the optical circulator 130.
  • variable optical attenuator 121 (Variable Optical Attenuator, VOA) realizes real-time control of the signal by attenuating the transmission optical power.
  • the polarization modulator 122 (PC) can realize polarization modulation of light.
  • the phase intensity modulation module 150 includes a first phase modulator 151 and an intensity modulator 152.
  • the input end of the first phase modulator 151 is connected to the third end of the polarization-maintaining interference ring 140.
  • the input terminal of the intensity modulator 152 is connected to the output terminal of the first phase modulator 151.
  • the quantum communication optical path system 100 further includes a polarization maintaining fiber.
  • the light source module 110, the intensity polarization modulation module 120, the polarization-maintaining interference ring 140, the phase intensity modulation module 150, the first isolator 170, and the first polarization beam splitter 180 pass between The polarization maintaining fiber is connected.
  • this application provides a quantum communication method, including:
  • the receiving end provides an optical signal pulse, and performs intensity modulation and polarization modulation on the optical signal pulse;
  • S30 Perform phase modulation and intensity modulation on the first optical signal pulse and the second optical signal pulse, respectively, and combine the phase modulation and intensity modulation on the first optical signal pulse and the second optical signal The pulse is transmitted to the sender through the communication channel;
  • S50 Perform security detection according to the first detected optical signal, and divide the second optical signal into two second sub-optical signals;
  • S60 Perform security detection according to the third detection optical signal, and divide the fourth optical signal into two fourth sub optical signals;
  • S70 Perform phase modulation and polarization rotation of one of the second optical sub-signals by 90° in sequence to form a first sub-detection optical signal among the two second optical sub-signals, and perform the other second sub-optical signal in sequence.
  • the polarization state is rotated by 90° and the phase is modulated to form a second sub-detection light signal, and the first sub-detection light signal and the second sub-detection light signal are combined into a first detection light signal pulse;
  • S80 Perform phase modulation and polarization rotation of one of the fourth sub-optical signals by 90° in sequence to form a third sub-detection optical signal among the two fourth sub-optical signals, and perform the other fourth sub-optical signal in sequence.
  • the polarization state is rotated by 90° and the phase is modulated to form a fourth sub-detection light signal, and the third sub-detection light signal and the fourth sub-detection light signal are combined into a second detection light signal pulse;
  • S90 Transmit the first detection light signal pulse and the second detection light signal pulse to the receiving end through a communication channel for detection, and reversely decode the code modulation performed by the transmitting end.
  • the Bob end can be triggered by a pulse laser at a repetition frequency of 32 MHz to send out light signal pulses.
  • the trigger signal is collected as the trigger clock signal of the electro-optic modulator on the Bob end and the single photon detector.
  • the optical signal pulse passes through the adjustable attenuator 121, the polarization modulator 122, and the third polarization beam splitter 123 in sequence, the optical signal pulse is intensity modulated and polarization modulated.
  • the optical signal pulse after passing through the third polarization beam splitter 123 is modulated by a polarization-maintaining interference ring 140 (PMI) with an arm length difference of 3 meters to a front-to-back time difference of about 15 nanoseconds.
  • a polarization-maintaining interference ring 140 (PMI) with an arm length difference of 3 meters to a front-to-back time difference of about 15 nanoseconds.
  • the second optical signal pulse has a time delay with respect to the first optical signal pulse.
  • the PMFC in the polarization-maintaining interference ring 140 (PMI) is a polarization-maintaining 50:50 beam splitter.
  • the intensity modulator 152 modulates the first optical signal pulse and the second optical signal pulse according to the required preprocessing, respectively.
  • the required pre-processing can be constant intensity, halved intensity, and complete extinction.
  • the first optical signal pulse is eliminated, the second optical signal pulse remains unchanged, and the corresponding information is encoded as 0.
  • the second optical signal pulse is eliminated, the first optical signal pulse remains unchanged, and the corresponding information is coded as 1.
  • the light intensity of the first optical signal pulse is eliminated by half, and the light intensity of the second optical signal pulse is eliminated by half, and the corresponding information is encoded as 0.
  • the required pre-processing may be to change the phase of the ⁇ and not to change the phase, respectively.
  • the phase of the second optical signal pulse remains unchanged, that is, the phase is not changed, and the corresponding information is encoded as 0.
  • the first optical signal pulse changes the phase ⁇ or the second optical signal pulse changes the phase ⁇ , that is, the relative phase is changed, and the corresponding information is encoded as 1.
  • the first optical signal pulse and the second optical signal pulse are pre-modulated at the Bob end into a form of front and rear pulses with adjustable relative phases, and are transmitted to the sending end (Alice end) through a communication channel.
  • the first optical signal pulse transmitted to the Alice end is divided into a first detection optical signal and a second optical signal via the beam splitter 210.
  • the second optical signal pulse is divided into a third detection optical signal and a fourth optical signal.
  • part of the optical signals (first detection optical signal, third detection optical signal) are split through the beam splitter 210, and the detection signals (first detection optical signal, third detection optical signal) are paired with the single-photon detector 250.
  • the second optical signal is divided into two second optical sub-signals by the second polarization beam splitter 220.
  • the fourth optical signal is divided into two fourth sub-optical signals.
  • one of the two second optical sub-signals is sequentially phase-modulated and the polarization state is rotated by 90° to form a first sub-detection optical signal.
  • the other second sub-optical signal is sequentially rotated by 90° in polarization state and phase-modulated to form a second sub-detection optical signal.
  • the first sub-detection light signal and the second sub-detection light signal are combined into a first detection light signal pulse.
  • one of the fourth sub-optical signals of the two fourth sub-optical signals is sequentially phase-modulated and the polarization state is rotated by 90° to form a third sub-detection optical signal.
  • the other fourth sub-optical signal is sequentially polarized by 90° and phase-modulated to form a fourth sub-detection optical signal, and the third sub-detection optical signal and the fourth sub-detection optical signal are combined into a fourth sub-detection optical signal.
  • the phases of the two second optical sub-signals are kept unchanged. Or, changing the phase of the two second optical sub-signals.
  • the first optical signal pulse transmitted to the Alice end is the remaining light split by the beam splitter 210, that is, the two second sub-optical signals. Without changing the phase, the corresponding information is encoded as 0, and when the phase of ⁇ is changed, the corresponding information is encoded as 1.
  • the phases of the two fourth optical sub-signals are kept unchanged. Or, changing the phase of the two fourth optical sub-signals.
  • the second optical signal pulse transmitted to the Alice end is the remaining light split by the beam splitter 210, that is, the two fourth sub-optical signals. Without changing the phase, the corresponding information is encoded as 0, and when the phase of ⁇ is changed, the corresponding information is encoded as 1.
  • the loop formed by the second phase modulator 240, the second polarization beam splitter 220, and the 90° Faraday rotator 230 makes the front and back pulses transmitted to the Alice end (the first optical signal pulse And the second optical signal pulse) to perform two relative phase modulations.
  • the loop (the loop formed by the second phase modulator 240, the second polarization beam splitter 220, and the 90° Faraday rotator 230) extends in different directions and passes through the Faraday rotator and the electro-optical phase modulator to carry out the remaining optical signals.
  • Phase encoding operation After passing through the loop, after being combined by the second polarization beam splitter 220, the first detection light signal pulse and the second detection light signal pulse are formed. And the first detection light signal pulse and the second detection light signal pulse are transmitted to the Bob terminal via the communication channel.
  • the first probe light signal pulse and the second probe light signal pulse are transmitted to the receiving end (Bob end) through the communication channel, they pass through the first polarization beam splitter 180.
  • the intensity modulator 152 and the phase modulator 151 directly reach the PMI polarization-maintaining interference ring 140.
  • the first PMFC divides the first detection light signal pulse and the second detection light signal pulse (front and back pulses) returned via the Alice end into two paths.
  • the first probe light signal pulse (pre-pulse) at the 3m optical fiber and the second probe light signal pulse (post-pulse) will reach the second PMFC at the same time.
  • the first probe light signal pulse and the second probe light signal pulse will be transmitted from the first end (port 1) of the PMI polarization-maintaining interference ring 140 or The second end (port 2) exits and reaches a different single-photon detector.
  • the corresponding information code is 0 or the corresponding information code is 1 and exits from port 1 or port 2, and reaches the corresponding third single-photon detector 131 and first single-photon detector 141. Probe.
  • the information corresponding to the two is XORed, and the solution can be reversed. Alice’s end encodes the light pulses to realize quantum communication.
  • the above steps S10 to S90 are repeated at a repetition frequency of 32 MHz to perform communication for a period of time, and both the Alice end and the Bob end record the results detected by the detector.
  • the Alice side publishes the detection result of the corresponding detection signal and the modulation information coding of the coded signal at the corresponding time position, and both parties can calculate
  • the security capacity of the output channel is finally successfully shared according to the pre-appointed key extraction method.
  • the quantum communication optical path system 100 and the quantum communication method in the above embodiment can solve the problems of high bit error rate, real-time compensation and loop burst mode in a series of quantum communication protocols, so that the quantum communication system It can run more stably, accurately and at high speed.
  • the quantum communication optical system 100 can realize deterministic key transmission and direct transmission of information in the quantum circuit.
  • FIG. 4 a schematic diagram of an optical signal after pre-modulation through a quantum communication optical path system.
  • the quantum state of the optical signal is shown in Figure 4, and the test bit (TestBit) is divided into only the front pulse s and only the back pulse l.
  • the signal bit (Signal Bit) means that the intensity of the pre-pulse s and the post-pulse l becomes half of the original, and the relative phase ⁇ can be set to 0 and ⁇ respectively.

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Abstract

本申请公开一种量子通信光路系统和量子通信方法，使得光信号经第一偏振分束器绕过相位强度调制模块直接到达PMI保偏干涉环，从而解决了光信号回路串模的问题，大大提高了电路的调制速度。

Description

量子通信光路系统和量子通信方法
相关申请
本申请要求2019年12月23日申请的，申请号为2019113356958，名称为“量子通信光路系统和量子通信方法”的中国专利申请的优先权，在此将其全文引入作为参考。
技术领域
本申请涉及量子通信领域，特别是涉及一种量子通信光路系统和量子通信方法。
背景技术
量子通信是指利用量子纠缠效应进行信息传递的一种新型的通讯方式。在量子保密通信技术中，最常用的编码方式为相位编码与偏振编码。其中，基于相位编码的量子通信是一种在光纤中可以稳定传输的保密通信方式。
量子通信光路系统中双路的量子通信需要让光信号沿原路返回进行解码操作。然而，传统的量子通信光路系统在光信号传输过程中，电光调制器会干扰到回路的光信号，进而导致双路量子通信系统的光信号回路串模的问题。
申请内容
有鉴于此，本申请公开一种量子通信光路系统。所述量子通信光路系统包括光源模块、强度偏振调制模块、保偏干涉环、相位强度调制模块、第一隔离器、第一偏振分束器、第二隔离器、分束器、第二偏振分束器、90°法拉第旋镜以及第二相位调制器。所述强度偏振调制模块输入端与所述光源模块输出端连接，用于将所述光信号脉冲进行强度调制与偏振调制。所述保偏干涉环第一端与所述强度偏振调制模块输出端连接。所述相位强度调制模块输入端与所述保偏干涉环第三端连接，用于将经所述保偏干涉环的所述光信号脉冲进行相位调制与强度调制。所述第一隔离器输入端与所述强度调制模块输出端连接。所述第一偏振分束器第一端与所述第一隔离器输出端连接。所述第二隔离器输入端与所述第一偏振分束器第三端连接，所述第二隔离器输出端与所述保偏干涉环第四端连接。
所述分束器第一端与所述第一偏振分束器第二端通过通信信道连接。所述第二偏振分束器第一端与所述分束器第三端连接。所述第二相位调制器第一端与所述第二偏振分束器第二端连接。所述90°法拉第旋镜第一端与所述第二相位调制器第二端连接。所述90° 法拉第旋镜第二端与所述第二偏振分束器第三端连接。
在其中一个实施例中，所述量子通信光路系统还包括第一单光子探测器。所述第一单光子探测器与所述保偏干涉环第二端连接。
在其中一个实施例中，所述量子通信光路系统还包括第二单光子探测器。所述第二单光子探测器与所述分束器第二端连接。
在其中一个实施例中，所述量子通信光路系统还包括光环行器。所述光环行器第一端与所述强度偏振调制模块输出端连接，所述光环行器第二端与所述保偏干涉环第一端连接。
在其中一个实施例中，所述量子通信光路系统还包括第三单光子探测器。所述第三单光子探测器与所述光环行器第三端连接。
在其中一个实施例中，所述强度偏振调制模块包括可调衰减器、偏振调制器以及第三偏振分束器。所述可调衰减器输入端与所述光源模块输出端连接。所述偏振调制器输入端与所述可调衰减器输出端连接。所述第三偏振分束器输入端与所述偏振调制器输出端连接。所述第三偏振分束器输出端与所述光环行器第一端连接。
在其中一个实施例中，所述相位强度调制模块包括第一相位调制器。所述第一相位调制器输入端与所述保偏干涉环第三端连接，所述第一相位调制器输出端与所述第一隔离器输入端连接。
在其中一个实施例中，所述相位强度调制模块还包括强度调制器。所述强度调制器输入端与所述第一相位调制器输出端连接，所述强度调制器输出端与所述第一隔离器输入端连接。
在其中一个实施例中，所述量子通信光路系统还包括保偏光纤。所述光源模块、所述强度偏振调制模块、所述保偏干涉环、所述相位强度调制模块、所述第一隔离器以及所述第一偏振分束器之间通过所述保偏光纤连接。
在其中一个实施例中，本申请提供一种量子通信方法，包括：
S10，接收端提供光信号脉冲，并将所述光信号脉冲进行强度调制与偏振调制；
S20，将经过强度调制与偏振调制后的所述光信号脉冲分为第一光信号脉冲与第二光信号脉冲，所述第二光信号脉冲相对于所述第一光信号脉冲具有时间延迟；
S30，将所述第一光信号脉冲与所述第二光信号脉冲分别进行相位调制与强度调制，并将经过相位调制与强度调制后的所述第一光信号脉冲与所述第二光信号脉冲通过通信信道传输至发送端；
S40，将传输至发送端的所述第一光信号脉冲分为第一检测光信号和第二光信号，将 传输至发送端的所述第二光信号脉冲分为第三检测光信号和第四光信号；
S50，根据所述第一检测光信号进行安全性检测，并将所述第二光信号分为两个第二子光信号；
S60，根据所述第三检测光信号进行安全性检测，并将所述第四光信号分为两个第四子光信号；
S70，将两个所述第二子光信号中一个所述第二子光信号依次进行相位调制与偏振态旋转90°形成第一子探测光信号，另一个所述第二子光信号依次进行偏振态旋转90°与相位调制形成第二子探测光信号，并将所述第一子探测光信号与所述第二子探测光信号合束为第一探测光信号脉冲；
S80，将两个所述第四子光信号中一个所述第四子光信号依次进行相位调制与偏振态旋转90°形成第三子探测光信号，另一个所述第四子光信号依次进行偏振态旋转90°与相位调制形成第四子探测光信号，并将所述第三子探测光信号与所述第四子探测光信号合束为第二探测光信号脉冲；
S90，将所述第一探测光信号脉冲与所述第二探测光信号脉冲通过通信信道传输至接收端进行探测，并反解出发送端进行的编码调制。
在其中一个实施例中，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行强度调制包括：
消除所述第一光信号脉冲，所述第二光信号脉冲保持不变。
在其中一个实施例中，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行强度调制包括：
所述第一光信号脉冲保持不变，消除所述第二光信号脉冲。
在其中一个实施例中，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行强度调制包括：
将所述第一光信号脉冲的光强消除一半，且将所述第二光信号脉冲的光强消除一半。
在其中一个实施例中，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行相位调制包括：
将所述第二光信号脉冲的相位保持不变。
在其中一个实施例中，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行相位调制包括：
将所述第一光信号脉冲改变Π相位。
在其中一个实施例中，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲 进行相位调制包括：
将所述第二光信号脉冲改变Π相位。
在其中一个实施例中，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
将两个所述第二子光信号的相位保持不变。
在其中一个实施例中，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
将两个所述第二子光信号改变Π相位。
在其中一个实施例中，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
将两个所述第四子光信号的相位保持不变。
在其中一个实施例中，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
将两个所述第四子光信号改变Π相位。
本申请提供一种上述量子通信光路系统和量子通信方法。通过上述所述量子通信光路系统，光信号脉冲由Bob端光源发出，经强度及偏振调制后，由PMI保偏干涉环分为前后两个脉冲，即第一光信号脉冲为前脉冲，第二光信号脉冲为后脉冲。第一光信号脉冲(前脉冲)与第二光信号脉冲(后脉冲)经所述相位强度调制模块进行相位调制与强度调制，可以理解为脉冲信号的预处理。然后经通信信道传递到Alice端。
经过相位调制与强度调制的第一光信号脉冲(前脉冲)与第二光信号脉冲(后脉冲)到达Alice端后经由分束器分出部分光信号(即第一检测光信号和第三检测光信号)，进行安全性检测。其余光信号(即第二光信号和第四光信号)经第二偏振分束器在环路(第二相位调制器、第二偏振分束器以及90°法拉第旋镜形成的环路)延不同方向经过法拉第旋转镜和电光相位调制器对其余光信号(即第二光信号和第四光信号)进行相位编码操作，形成第一探测光信号脉冲和第二探测光信号脉冲，之后经由通信信道传递到Bob端。
第一探测光信号脉冲和第二探测光信号脉冲到达Bob端后，会经由第一偏振分束器绕过相位强度调制模块(强度调制器和相位调制器)直接到达PMI保偏干涉环。并根据Bob端的相位预调制和Alice端的相位编码的不同，第一探测光信号脉冲和第二探测光信号脉冲会从PMI保偏干涉环的第一端(端口1)或者第二端(端口2)出射，到达不同的单光子探测器。此时，Bob端根据不同的单光子探测器的响应和光脉冲的预调制，可反解出Alice端对光脉冲的编码，从而实现量子通信。
因此，在Alice端经第二偏振分束器从两个方向沿环路同时经过电光相位调制器进行编码，并通过第二偏振分束器与90°法拉第旋镜的作用，使得光信号(即第一探测光信号脉冲和第二探测光信号脉冲)通过通信信道返回Bob端时的偏振恰好与从Bob端射出时的偏振相差90°角，使得光信号(即第一探测光信号脉冲和第二探测光信号脉冲)可以经第一偏振分束器绕过相位强度调制模块(强度调制器和相位调制器)直接到达PMI保偏干涉环，从而解决了光信号回路串模的问题，大大提高了电路的调制速度。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据公开的附图获得其他的附图。
图1为本申请提供的量子通信光路系统的示意图。
图2为本申请提供的量子通信光路系统的光信号走向示意图。
图3为本申请提供的量子通信光路系统的光信号变换示意图。
图4为本申请提供的量子通信光路系统中预调制后的光信号示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
为了使本申请的目的、技术方案及优点更加清楚明白，以下通过实施例，并结合附图，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本申请，并不用于限定本申请。
请参见图1-3，本申请提供一种量子通信光路系统100。所述量子通信光路系统100包括光源模块110、强度偏振调制模块120、保偏干涉环140、相位强度调制模块150、第一隔离器170、第一偏振分束器180、第二隔离器190、分束器210、第二偏振分束器220、90°法拉第旋镜230以及第二相位调制器240。所述强度偏振调制模块120输入端与所述光源模块110输出端连接，用于将所述光信号脉冲进行强度调制与偏振调制。所述保偏干涉环140第一端与所述强度偏振调制模块120输出端连接。所述相位强度调制模块150输 入端与所述保偏干涉环140第三端连接，用于将经所述保偏干涉环140的所述光信号脉冲进行相位调制与强度调制。所述第一隔离器170输入端与所述相位强度调制模块150输出端连接。所述第一偏振分束器180第一端与所述第一隔离器170输出端连接。所述第二隔离器190输入端与所述第一偏振分束器180第三端连接，所述第二隔离器190输出端与所述保偏干涉环140第四端连接。
所述分束器210第一端与所述第一偏振分束器180第二端通过通信信道连接。所述第二偏振分束器220第一端与所述分束器210第三端连接。所述第二相位调制器240第一端与所述第二偏振分束器220第二端连接。所述90°法拉第旋镜230第一端与所述第二相位调制器240第二端连接。所述90°法拉第旋镜230第二端与所述第二偏振分束器220第三端连接。
本实施例中，接收端(Bob端)所述光源模块110用于发出光信号脉冲。所述强度偏振调制模块120输入端与所述光源模块110输出端连接，用于将所述光信号脉冲进行强度调制与偏振调制。所述保偏干涉环140第一端与所述强度偏振调制模块120输出端连接，用于将经过所述强度偏振调制模块120的所述光信号脉冲分为第一光信号脉冲与第二光信号脉冲。所述第二光信号脉冲相对于所述第一光信号脉冲具有时间延迟。所述相位强度调制模块150输入端与所述保偏干涉环140第三端连接，用于将所述第一光信号脉冲与所述第二光信号脉冲分别进行相位调制与强度调制。所述第一隔离器170输入端与所述相位强度调制模块150输出端连接，用于将经过强度调制的所述第一光信号脉冲与所述第二光信号脉冲的传输方向进行阻隔，使得光路只有一个方向能通过。
经过所述第一隔离器170的所述第一光信号脉冲与所述第二光信号脉冲单向经过所述第一偏振分束器180后，通过信道传输至发送端(Alice端)的分束器210。所述分束器210第一端与所述第一偏振分束器180第二端连接，用于将经所述偏振分束器180后并通过信道传输的所述第一光信号脉冲分为第一检测光信号和第二光信号，将经所述偏振分束器180后并通过信道传输的所述第二光信号脉冲分为第三检测光信号和第四光信号。
所述第二偏振分束器220第一端与所述分束器210第三端连接，用于将所述第二光信号分为两个第二子光信号。将所述第四光信号分为两个第四子光信号。两个所述第二子光信号中一个所述第二子光信号依次经所述第二相位调制器240与所述90°法拉第旋镜230后传输至所述第二偏振分束器220第三端，形成第一子探测光信号。另一个所述第二子光信号依次经所述90°法拉第旋镜230与所述第二相位调制器240后传输至所述第二偏振分束器220第二端，形成第二子探测光信号。所述第一子探测光信号与所述第二子探测光信号经所述第二偏振分束器220后合束为第一探测光信号脉冲。
两个所述第四子光信号中一个所述第四子光信号依次经所述第二相位调制器240与所述90°法拉第旋镜230后传输至所述第二偏振分束器220第三端，形成第三子探测光信号。另一个所述第四子光信号经所述90°法拉第旋镜230与所述第二相位调制器240后传输至所述第二偏振分束器220第二端，形成第四子探测光信号。所述第三子探测光信号与所述第四子探测光信号经所述第二偏振分束器220后合束为第二探测光信号脉冲。
所述第一探测光信号脉冲经所述分束器210后并通过信道传输至所述第一偏振分束器180第二端，并经所述第一偏振分束器180与所述第二隔离器190传输至所述保偏干涉环140进行探测。
所述第二探测光信号脉冲经所述分束器210后并通过信道传输至所述第一偏振分束器180第二端，并经所述第一偏振分束器180与所述第二隔离器190传输至所述保偏干涉环140进行探测。
其中，所述第二隔离器190用于对传输方向进行阻隔，使得光路只有一个方向能通过。
所以，通过上述所述量子通信光路系统100，光信号脉冲由Bob端光源发出，经强度及偏振调制后，由PMI保偏干涉环140分为前后两个脉冲，即第一光信号脉冲为前脉冲，第二光信号脉冲为后脉冲。第一光信号脉冲(前脉冲)与第二光信号脉冲(后脉冲)经所述相位强度调制模块150进行相位调制与强度调制，可以理解为脉冲信号的预处理。然后经通信信道传递到Alice端。
经过相位调制与强度调制的第一光信号脉冲(前脉冲)与第二光信号脉冲(后脉冲)到达Alice端后经由分束器210分出部分光信号(即第一检测光信号和第三检测光信号)，进行安全性检测。其余光信号(即第二光信号和第四光信号)经第二偏振分束器220在环路(第二相位调制器240、第二偏振分束器220以及90°法拉第旋镜230形成的环路)延不同方向经过法拉第旋转镜和电光相位调制器对其余光信号(即第二光信号和第四光信号)进行相位编码操作，形成第一探测光信号脉冲和第二探测光信号脉冲，之后经由通信信道传递到Bob端。
第一探测光信号脉冲和第二探测光信号脉冲到达Bob端后，会经由第一偏振分束器180绕过相位强度调制模块150(强度调制器152和相位调制器151)直接到达PMI保偏干涉环140。并根据Bob端的相位预调制和Alice端的相位编码的不同，第一探测光信号脉冲和第二探测光信号脉冲会从PMI保偏干涉环140的第一端(端口1)或者第二端(端口2)出射，到达不同的单光子探测器。此时，Bob端根据不同的单光子探测器的响应和光脉冲的预调制，可反解出Alice端对光脉冲的编码，从而实现量子通信。
因此，在Alice端经第二偏振分束器220从两个方向沿环路同时经过电光相位调制器 240进行编码，并通过第二偏振分束器220与90°法拉第旋镜230的作用，使得光信号(即第一探测光信号脉冲和第二探测光信号脉冲)通过通信信道返回Bob端时的偏振恰好与从Bob端射出时的偏振相差90°角，使得光信号(即第一探测光信号脉冲和第二探测光信号脉冲)可以经第一偏振分束器180绕过相位强度调制模块150(强度调制器152和相位调制器151)直接到达PMI保偏干涉环140，从而解决了光信号回路串模的问题，大大提高了电路的调制速度。
在一个实施例中，所述量子通信光路系统100还包括第一单光子探测器141、第二单光子探测器250、光环行器130以及第三单光子探测器131。所述第一单光子探测器141与所述保偏干涉环140第二端连接。所述第二单光子探测器250与所述分束器210第二端连接。所述光环行器130第一端与所述强度偏振调制模块120输出端连接，所述光环行器130第二端与所述保偏干涉环140第一端连接。所述第三单光子探测器131与所述光环行器130第三端连接。
本实施例中，所述第一单光子探测器141、所述第二单光子探测器250以及所述第三单光子探测器131用于进行APD检测。其中，所述第二单光子探测器250与所述分束器210第二端连接，用于对Bob端光信号经由通信信道传至Alice端并由所述分束器210分出的部分光信号进行安全性检测。所述第一单光子探测器141与所述保偏干涉环140第二端连接，所述第三单光子探测器131与所述光环行器130第三端连接。所述第一单光子探测器141和所述第三单光子探测器131，用于对Alice端光信号经由通信信道传至Bob端后，并绕过相位强度调制模块150(强度调制器152和相位调制器151)直接到达PMI保偏干涉环140后，经第一端口或者第二端口出射的光信号进行探测。
此时，所述量子通信光路系统100的安全性检测在Alice端进行，解码以及安全容量分析在Bob端进行。光信号的前后脉冲的粒子数作为检测安全性的正交基矢，前后脉冲的相对相位作为加载编码的载体。
在一个实施例中，所述强度偏振调制模块120包括可调衰减器121、偏振调制器122以及第三偏振分束器123。所述可调衰减器121输入端与所述光源模块110输出端连接。所述偏振调制器122输入端与所述可调衰减器121输出端连接。所述第三偏振分束器123输入端与所述偏振调制器122输出端连接。所述第三偏振分束器123输出端与所述光环行器130第一端连接。
其中，可调衰减器121(Variable Optical Attenuator，VOA)，通过衰减传输光功率来实现对信号的实时控制。所述偏振调制器122(PC)，可以实现对光进行偏振调制。
在一个实施例中，所述相位强度调制模块150包括第一相位调制器151与强度调制器 152。所述第一相位调制器151输入端与所述保偏干涉环140第三端连接。所述强度调制器152输入端与所述第一相位调制器151输出端连接。
在一个实施例中，所述量子通信光路系统100还包括保偏光纤。所述光源模块110、所述强度偏振调制模块120、所述保偏干涉环140、所述相位强度调制模块150、所述第一隔离器170以及所述第一偏振分束器180之间通过所述保偏光纤连接。
请参见图2-3，在一个实施例中，本申请提供一种量子通信方法，包括：
S10，接收端提供光信号脉冲，并将所述光信号脉冲进行强度调制与偏振调制；
S20，将经过强度调制与偏振调制后的所述光信号脉冲分为第一光信号脉冲与第二光信号脉冲，所述第二光信号脉冲相对于所述第一光信号脉冲具有时间延迟；
S30，将所述第一光信号脉冲与所述第二光信号脉冲分别进行相位调制与强度调制，并将经过相位调制与强度调制后的所述第一光信号脉冲与所述第二光信号脉冲通过通信信道传输至发送端；
S40，将传输至发送端的所述第一光信号脉冲分为第一检测光信号和第二光信号，将传输至发送端的所述第二光信号脉冲分为第三检测光信号和第四光信号；
S50，根据所述第一检测光信号进行安全性检测，并将所述第二光信号分为两个第二子光信号；
S60，根据所述第三检测光信号进行安全性检测，并将所述第四光信号分为两个第四子光信号；
S70，将两个所述第二子光信号中一个所述第二子光信号依次进行相位调制与偏振态旋转90°形成第一子探测光信号，另一个所述第二子光信号依次进行偏振态旋转90°与相位调制形成第二子探测光信号，并将所述第一子探测光信号与所述第二子探测光信号合束为第一探测光信号脉冲；
S80，将两个所述第四子光信号中一个所述第四子光信号依次进行相位调制与偏振态旋转90°形成第三子探测光信号，另一个所述第四子光信号依次进行偏振态旋转90°与相位调制形成第四子探测光信号，并将所述第三子探测光信号与所述第四子探测光信号合束为第二探测光信号脉冲；
S90，将所述第一探测光信号脉冲与所述第二探测光信号脉冲通过通信信道传输至接收端进行探测，并反解出发送端进行的编码调制。
在所述S10中，在Bob端可以通过脉冲激光器以32MHz的重复频率触发，发出光信号脉冲。并同时采集触发信号作为Bob端的电光调制器以及单光子探测器的触发时钟信号。通过光信号脉冲依次经过所述可调衰减器121、所述偏振调制器122以及所述第三偏振分 束器123后，对所述光信号脉冲进行强度调制与偏振调制。
在所述S20中，将经过所述第三偏振分束器123后的所述光信号脉冲，通过臂长差为3米的保偏干涉环140(PMI)调制为前后时差约为15纳秒的前后脉冲，即所述第一光信号脉冲与所述第二光信号脉冲。此时，所述第二光信号脉冲相对于所述第一光信号脉冲具有时间延迟。并且，其中所述保偏干涉环140(PMI)中PMFC为保偏的50：50分束器。
在所述S30中，通过所述强度调制器152，对所述第一光信号脉冲与所述第二光信号脉冲分别按所需预处理进行调制。具体地，所需预处理可以分别为强度不变、强度减半和完全消光等。相应地，消掉第一光信号脉冲，第二光信号脉冲保持不变，对应信息编码为0。或者，消掉第二光信号脉冲，第一光信号脉冲不变，对应信息编码为1。或者，第一光信号脉冲的光强消除一半，第二光信号脉冲的光强消除一半，对应信息编码为0。
然后，通过所述第一相位调制器151，对所述第一光信号脉冲与所述第二光信号脉冲分别按所需预处理进行调制。具体地，所需预处理可以分别为改变Π相位和不改变相位。相应地，第二光信号脉冲的相位保持不变，即不改变相位，对应信息编码为0。或者，第一光信号脉冲改变Π相位或第二光信号脉冲改变Π相位，即改变相对相位，对应信息编码为1。
所述第一光信号脉冲与所述第二光信号脉冲在Bob端预调制为前后脉冲且相对相位可调的形式，通过通信信道传输至发送端(Alice端)。
在所述S40中，将传输至Alice端的所述第一光信号脉冲，经由所述分束器210分为第一检测光信号和第二光信号。将所述第二光信号脉冲分为第三检测光信号和第四光信号。此时，经由所述分束器210分出部分光信号(第一检测光信号、第三检测光信号)用单光子探测器250对检测信号(第一检测光信号、第三检测光信号)进行安全性检测，并将触发信号作为时钟信号与Alice端的相位调制器进行始终同步。
在所述S50和S60中，通过所述第二偏振分束器220将所述第二光信号分为两个第二子光信号。将所述第四光信号分为两个第四子光信号。
在所述S70中，将两个所述第二子光信号中一个所述第二子光信号依次进行相位调制与偏振态旋转90°形成第一子探测光信号。另一个所述第二子光信号依次进行偏振态旋转90°与相位调制形成第二子探测光信号。将所述第一子探测光信号与所述第二子探测光信号合束为第一探测光信号脉冲。
在所述S80中，将两个所述第四子光信号中一个所述第四子光信号依次进行相位调制与偏振态旋转90°形成第三子探测光信号。另一个所述第四子光信号依次进行偏振态旋转90°与相位调制形成第四子探测光信号，并将所述第三子探测光信号与所述第四子探测光 信号合束为第二探测光信号脉冲。
通过所述第二相位调制器240进行相位调制时，将两个所述第二子光信号的相位保持不变。或者，将两个所述第二子光信号改变Π相位。此时，传输至Alice端的所述第一光信号脉冲，经由所述分束器210分出的其余光，即两个所述第二子光信号。不改变相位，对应信息编码为0，改变Π相位，对应信息编码为1。
通过所述第二相位调制器240进行相位调制时，将两个所述第四子光信号的相位保持不变。或者，将两个所述第四子光信号改变Π相位。此时，传输至Alice端的所述第二光信号脉冲，经由所述分束器210分出的其余光，即两个所述第四子光信号。不改变相位，对应信息编码为0，改变Π相位，对应信息编码为1。
因此，通过所述第二相位调制器240、所述第二偏振分束器220以及所述90°法拉第旋镜230形成的环路，使得传输至Alice端的前后脉冲(所述第一光信号脉冲和所述第二光信号脉冲)进行相对相位的两种调制。
此时，在环路(第二相位调制器240、第二偏振分束器220以及90°法拉第旋镜230形成的环路)延不同方向经过法拉第旋转镜和电光相位调制器对其余光信号进行相位编码操作。经环路之后，通过所述第二偏振分束器220合并后，形成所述第一探测光信号脉冲和所述第二探测光信号脉冲。并将所述第一探测光信号脉冲和所述第二探测光信号脉冲，经由通信信道传递到Bob端。
在所述S90中，将所述第一探测光信号脉冲与所述第二探测光信号脉冲通过通信信道传输至接收端(Bob端)后，经所述第一偏振分束器180绕过所述强度调制器152和所述相位调制器151直接到达所述PMI保偏干涉环140。在所述PMI保偏干涉环140中，第一个PMFC会把经Alice端的返回的所述第一探测光信号脉冲和所述第二探测光信号脉冲(前后脉冲)分为两路，经过多3米光纤处的所述第一探测光信号脉冲(前脉冲)，与所述第二探测光信号脉冲(后脉冲)将同时达到第二个PMFC。此时，根据所述第一探测光信号脉冲(前脉冲)和所述第二探测光信号脉冲(后脉冲)的相对相位0或Π，在出口(端口1或端口2)一路干涉相消或加强，一路干涉加强或相消。从而，根据Bob端的相位预调制和Alice端的相位编码的不同，所述第一探测光信号脉冲和所述第二探测光信号脉冲会从PMI保偏干涉环140的第一端(端口1)或者第二端(端口2)出射，到达不同的单光子探测器。
此时，可以理解为：对应信息编码为0或对应信息编码为1从端口1或端口2出射，并到达相应的所述第三单光子探测器131和所述第一单光子探测器141进行探测。同时，在Bob端根据所述第三单光子探测器131和所述第一单光子探测器141的响应以及在Bob 端光脉冲的预调制，两者对应的信息进行异或计算，可反解出在Alice端对光脉冲进行的编码，从而实现量子通信。
在一个实施例中，以32MHz的重复频率重复以上步骤S10～S90，进行一段时间的通信，Alice端和Bob端都将探测器探测到的结果记录下来。根据Bob端公布的对应探测信号的预调制与时间位置以及一部分编码信号的预调制与探测结果，Alice端公布对应探测信号的探测结果与相应时间位置的编码信号的调制信息编码，双方即可计算出信道的安全容量，最终按照事先约定好的密钥提取方式成功共享密钥。
因此，通过上述实施例中的所述量子通信光路系统100和所述量子通信方法可以解决在一系列量子通信协议中误码率高、需要实时补偿以及回路脉冲串模的问题，使得量子通信系统可以更加稳定、精确和高速地运行。同时，作为量子安全直接通信DL04协议发展出的新光路系统，所述量子通信光路系统100能实现确定性的密钥传输以及信息在量子线路中的直接传输功能。
请参见图4，在一个实施例中，通过量子通信光路系统，预调制后的光信号示意图。此时，预调制后，光信号量子态如图4所示，检测比特(TestBit)分为只有前脉冲s和只有后脉冲l。信号比特(Signal Bit)为前脉冲s和后脉冲l强度变为原来一半，相对相位θ可以分别取0和Π。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本申请专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。
最后，还需要说明的是，在本文中，诸如第一和第二等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或者暗示这些实体或操作之间存在任何这种实际的关系或者顺序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、物品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、物品或者设备所固有的要素。在没有更多限制的情况下，由语句“包括一个……”限定的要素，并不排除在包括所述要素的过程、方法、物品或者设备中还存在另外的相同要素。
本说明书中各个实施例采用递进的方式描述，每个实施例重点说明的都是与其他实施 例的不同之处，各个实施例之间相同相似部分互相参见即可。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本申请。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本申请的精神或范围的情况下，在其它实施例中实现。因此，本申请将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (20)

  1. 一种量子通信光路系统，其特征在于，包括：
    光源模块(110)，用于发出光信号脉冲；
    强度偏振调制模块(120)，所述强度偏振调制模块(120)输入端与所述光源模块(110)输出端连接，用于将所述光信号脉冲进行强度调制与偏振调制；
    保偏干涉环(140)，所述保偏干涉环(140)第一端与所述强度偏振调制模块(120)输出端连接；
    相位强度调制模块(150)，所述相位强度调制模块(150)输入端与所述保偏干涉环(140)第三端连接，用于将经所述保偏干涉环(140)的所述光信号脉冲进行相位调制与强度调制；
    第一隔离器(170)，所述第一隔离器(170)输入端与所述相位强度调制模块(150)输出端连接；
    第一偏振分束器(180)，所述第一偏振分束器(180)第一端与所述第一隔离器(170)输出端连接；
    第二隔离器(190)，所述第二隔离器(190)输入端与所述第一偏振分束器(180)第三端连接，所述第二隔离器(190)输出端与所述保偏干涉环(140)第四端连接；
    分束器(210)，所述分束器(210)第一端与所述第一偏振分束器(180)第二端通过通信信道连接；
    第二偏振分束器(220)，所述第二偏振分束器(220)第一端与所述分束器(210)第三端连接；
    第二相位调制器(240)，所述第二相位调制器(240)第一端与所述第二偏振分束器(220)第二端连接；
    90°法拉第旋镜(230)，所述90°法拉第旋镜(230)第一端与所述第二相位调制器(240)第二端连接，所述90°法拉第旋镜(230)第二端与所述第二偏振分束器(220)第三端连接。
  2. 如权利要求1所述的量子通信光路系统，其特征在于，还包括：
    第一单光子探测器(141)，与所述保偏干涉环(140)第二端连接。
  3. 如权利要求1所述的量子通信光路系统，其特征在于，还包括：
    第二单光子探测器(250)，与所述分束器(210)第二端连接。
  4. 如权利要求1所述的量子通信光路系统，其特征在于，还包括：
    光环行器(130)，所述光环行器(130)第一端与所述强度偏振调制模块(120)输出端连接，所述光环行器(130)第二端与所述保偏干涉环(140)第一端连接。
  5. 如权利要求4所述的量子通信光路系统，其特征在于，还包括：
    第三单光子探测器(131)，与所述光环行器(130)第三端连接。
  6. 如权利要求4所述的量子通信光路系统，其特征在于，所述强度偏振调制模块(120)包括：
    可调衰减器(121)，所述可调衰减器(121)输入端与所述光源模块(110)输出端连接；
    偏振调制器(122)，所述偏振调制器(122)输入端与所述可调衰减器(121)输出端连接；
    第三偏振分束器(123)，所述第三偏振分束器(123)输入端与所述偏振调制器(122)输出端连接，所述第三偏振分束器(123)输出端与所述光环行器(130)第一端连接。
  7. 如权利要求1所述的量子通信光路系统，其特征在于，所述相位强度调制模块(150)包括：
    第一相位调制器(151)，所述第一相位调制器(151)输入端与所述保偏干涉环(140)第三端连接，所述第一相位调制器(151)输出端与所述第一隔离器(170)输入端连接。
  8. 如权利要求7所述的量子通信光路系统，其特征在于，所述相位强度调制模块(150)还包括：
    强度调制器(152)，所述强度调制器(152)输入端与所述第一相位调制器(151)输出端连接，所述强度调制器(152)输出端与所述第一隔离器(170)输入端连接。
  9. 如权利要求1所述的量子通信光路系统，其特征在于，还包括保偏光纤，所述光源模块(110)、所述强度偏振调制模块(120)、所述保偏干涉环(140)、所述相位强度调制模块(150)、所述第一隔离器(170)以及所述第一偏振分束器(180)之间通过所述保偏光纤连接。
  10. 一种量子通信方法，其特征在于，包括：
    S10，接收端提供光信号脉冲，并将所述光信号脉冲进行强度调制与偏振调制；
    S20，将经过强度调制与偏振调制后的所述光信号脉冲分为第一光信号脉冲与第二光信号脉冲，所述第二光信号脉冲相对于所述第一光信号脉冲具有时间延迟；
    S30，将所述第一光信号脉冲与所述第二光信号脉冲分别进行相位调制与强度调制，并将经过相位调制与强度调制后的所述第一光信号脉冲与所述第二光信号脉冲通过通信信道传输至发送端；
    S40，将传输至发送端的所述第一光信号脉冲分为第一检测光信号和第二光信号，将传输至发送端的所述第二光信号脉冲分为第三检测光信号和第四光信号；
    S50，根据所述第一检测光信号进行安全性检测，并将所述第二光信号分为两个第二子光信号；
    S60，根据所述第三检测光信号进行安全性检测，并将所述第四光信号分为两个第四子光信号；
    S70，将两个所述第二子光信号中一个所述第二子光信号依次进行相位调制与偏振态旋转90°形成第一子探测光信号，另一个所述第二子光信号依次进行偏振态旋转90°与相位调制形成第二子探测光信号，并将所述第一子探测光信号与所述第二子探测光信号合束为第一探测光信号脉冲；
    S80，将两个所述第四子光信号中一个所述第四子光信号依次进行相位调制与偏振态旋转90°形成第三子探测光信号，另一个所述第四子光信号依次进行偏振态旋转90°与相位调制形成第四子探测光信号，并将所述第三子探测光信号与所述第四子探测光信号合束为第二探测光信号脉冲；
    S90，将所述第一探测光信号脉冲与所述第二探测光信号脉冲通过通信信道传输至接收端进行探测，并反解出发送端进行的编码调制。
  11. 如权利要求10所述的量子通信方法，其特征在于，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行强度调制包括：
    消除所述第一光信号脉冲，所述第二光信号脉冲保持不变。
  12. 如权利要求10所述的量子通信方法，其特征在于，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行强度调制包括：
    所述第一光信号脉冲保持不变，消除所述第二光信号脉冲。
  13. 如权利要求10所述的量子通信方法，其特征在于，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行强度调制包括：
    将所述第一光信号脉冲的光强消除一半，且将所述第二光信号脉冲的光强消除一半。
  14. 如权利要求10所述的量子通信方法，其特征在于，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行相位调制包括：
    将所述第二光信号脉冲的相位保持不变。
  15. 如权利要求10所述的量子通信方法，其特征在于，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行相位调制包括：
    将所述第一光信号脉冲改变Π相位。
  16. 如权利要求10所述的量子通信方法，其特征在于，在所述S30中，将所述第一光信号脉冲与所述第二光信号脉冲进行相位调制包括：
    将所述第二光信号脉冲改变Π相位。
  17. 如权利要求10所述的量子通信方法，其特征在于，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
    将两个所述第二子光信号的相位保持不变。
  18. 如权利要求10所述的量子通信方法，其特征在于，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
    将两个所述第二子光信号改变Π相位。
  19. 如权利要求10所述的量子通信方法，其特征在于，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
    将两个所述第四子光信号的相位保持不变。
  20. 如权利要求10所述的量子通信方法，其特征在于，在所述S70和S80中，将两个所述第二子光信号和两个所述第四子光信号进行相位调制包括：
    将两个所述第四子光信号改变Π相位。
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