CN116827541A - Quantum key distribution transmitting terminal based on real-time generation of quantum random numbers - Google Patents
Quantum key distribution transmitting terminal based on real-time generation of quantum random numbers Download PDFInfo
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- 230000010287 polarization Effects 0.000 claims abstract description 107
- 230000003287 optical effect Effects 0.000 claims abstract description 40
- 101100028789 Arabidopsis thaliana PBS1 gene Proteins 0.000 claims abstract description 38
- 101100139907 Arabidopsis thaliana RAR1 gene Proteins 0.000 claims abstract description 25
- 101100028790 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) PBS2 gene Proteins 0.000 claims abstract description 25
- 239000011159 matrix material Substances 0.000 claims description 12
- 101100448366 Arabidopsis thaliana GH3.12 gene Proteins 0.000 claims description 11
- 239000000835 fiber Substances 0.000 claims description 10
- 239000013307 optical fiber Substances 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 9
- 238000012805 post-processing Methods 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 230000002452 interceptive effect Effects 0.000 claims description 3
- 238000005070 sampling Methods 0.000 claims description 3
- 238000012545 processing Methods 0.000 abstract description 4
- 239000004973 liquid crystal related substance Substances 0.000 description 16
- 238000001514 detection method Methods 0.000 description 8
- 230000002238 attenuated effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000005684 electric field Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005610 quantum mechanics Effects 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
- H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
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- 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
- H04B10/508—Pulse generation, e.g. generation of solitons
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/54—Intensity modulation
- H04B10/541—Digital intensity or amplitude modulation
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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
- H04L9/0861—Generation of secret information including derivation or calculation of cryptographic keys or passwords
- H04L9/0869—Generation of secret information including derivation or calculation of cryptographic keys or passwords involving random numbers or seeds
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L2209/00—Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
- H04L2209/08—Randomization, e.g. dummy operations or using noise
Abstract
The invention belongs to the technical field of secret communication, and discloses a quantum key distribution transmitting end based on real-time generation of quantum random numbers, which comprises a laser LD, a first polarization beam splitter PBS1, a first beam splitter BS1, a first reflection module, a second polarization beam splitter PBS2, an intensity modulator IM, a phase modulator PM, an adjustable optical attenuator VOA, a photoelectric detector PD and a main control module. Compared with the prior art, the invention has the advantages that one path of output optical signals which are not used by the reflective interferometer are reflected back to the interferometer to interfere by the multiplexing laser to obtain the random light intensity signals generated by random phase fluctuation of the laser, the random light intensity signals are converted into random electric signals by the high-speed photoelectric detector, and the random signal acquisition processing module and the QKD main control module are integrated, so that the quantum random number and the quantum key distribution can be carried out simultaneously. The photoelectric detector can be used for realizing high-speed quantum random number generation, and can meet the requirements of quantum key distribution decoy state modulation and quantum state coding.
Description
Technical Field
The invention relates to the technical field of secret communication, in particular to a quantum key distribution transmitting end based on real-time generation of quantum random numbers.
Background
Quantum key distribution (quantum key distribution, QKD) can provide unconditionally secure key distribution for both parties in remote communications, with information theory security guaranteed by the basic principles of quantum mechanics. At present, the BB84 protocol quantum key distribution system is mature and becomes practical. The sender of existing QKD systems typically employs an independent random number generator to generate random numbers for decoy-state, quantum-state selection. One type is commonly used with various sources of physical random numbers, which are relatively high in rate, but are poorly secure. If a higher security high-speed quantum random number generator (quantum random number generator, QRNG) is employed, additional lasers, interferometers or other optical devices, and separate data acquisition and processing modules are required, greatly increasing the complexity and cost of the QKD system.
In order to solve the above problems, patent CN112994877B provides a scheme for switching quantum random number generation and quantum key distribution processes based on an optical switch, however, two processes cannot be performed simultaneously in the scheme, and only a laser is multiplexed to perform quantum random number generation, and in addition, a quantum random number generation scheme of photon arrival time is adopted, a time-to-digital converter and a single photon avalanche diode are required, and the scheme has the disadvantages of low speed, high complexity and the like. The QRNG based on vacuum fluctuation is integrated at the QKD transmitting end in the patents CN113037468B and CN112968768B, however, the solution needs a homodyne detector reaching the shot noise limit, and it is difficult to meet the high-speed requirement.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a quantum key distribution transmitting end based on real-time generation of quantum random numbers.
The technical scheme of the invention is realized as follows:
a quantum key distribution transmitting end based on real-time generation of quantum random numbers comprises a laser LD, a first polarization beam splitter PBS1, a first beam splitter BS1, a first reflection module, a second polarization beam splitter PBS2, an intensity modulator IM, a phase modulator PM, an adjustable optical attenuator VOA, a photoelectric detector PD and a main control module;
the laser LD is connected with a port I of the first polarization beam splitter PBS1, and a port II and a port III of the first polarization beam splitter PBS1 are correspondingly connected with a port I of the first beam splitter BS1 and the first reflection module respectively; the second port, the third port and the fourth port of the first beam splitter BS1 are correspondingly connected with the first port of the second polarization beam splitter PBS2, the first port of the second reflection module and the second port of the second reflection module through optical fibers with different lengths respectively; the second port and the third port of the second polarization beam splitter PBS2 are respectively and correspondingly connected with one end of the intensity modulator IM and the photoelectric detector PD; the other end of the intensity modulator IM is connected with the phase modulator PM and then is connected with one end of the adjustable optical attenuator VOA; the other end of the variable optical attenuator VOA is used as an output port of the transmitting end;
the laser LD is used for generating optical pulses with random phases with period T;
the first polarization beam splitter PBS1 is used for transmitting horizontally polarized light pulses;
the first beam splitter BS1 and the second reflection module form a reflection type unequal arm interferometer with the arm length delay time of T/2, and the reflection type unequal arm interferometer is used for splitting an optical pulse incident to a first port of the first beam splitter BS1 into a first component and a second component;
the first component and the second component both comprise two sub-pulses with the time difference of T/2 and are in a vertical polarization state, and are emitted from a port I and a port II of the first beam splitter BS1 respectively;
the first polarization beam splitter PBS1 is further configured to reflect the first component incident from the second port thereof to the first reflection module, and reflect the first component reflected by the first reflection module to the first port of the first beam splitter BS 1;
the reflective unequal-arm interferometer is further used for interfering the light pulses with different phases in the first component to generate a horizontal polarized random light intensity signal emitted from the second port of the first beam splitter BS 1;
the second polarizing beam splitter PBS2 is used to transmit the random light intensity signal of horizontal polarization to the photodetector PD and reflect the second component of vertical polarization to the intensity modulator IM;
the photodetector PD is configured to convert a random light intensity signal into an electrical signal;
the intensity modulator IM is used for randomly modulating the second component into a signal state or a decoy state;
the phase modulator PM is used for phase encoding the second component;
the variable optical attenuator VOA is used for attenuating the second component subjected to phase encoding to the single photon magnitude to generate a quantum state;
the main control module is used for triggering the laser; the method comprises the steps of generating initial random bits, performing analog-to-digital conversion on an electric signal of a photoelectric detector PD, sampling, and obtaining a quantum random number through a post-processing algorithm; and for providing the intensity modulator IM and the phase modulator PM with drive voltages based on the quantum random numbers generated in real time.
Preferably, the first reflective module is a mirror M.
Preferably, the first reflection module is a second beam splitter BS2, and two output ports of the second beam splitter BS2 are directly connected through polarization maintaining fibers to form a first annular structure.
Preferably, the first reflection module is a circulator CIR, and a port one and a port three of the circulator CIR are directly connected through a polarization maintaining fiber to form a second annular structure.
Preferably, the second reflecting module comprises a first faraday mirror FM1 and a second faraday mirror FM2 respectively connected to port three and port four of the first beam splitter BS 1.
Preferably, the second reflection module includes a first quarter-wave plate mirror QM1 and a second quarter-wave plate mirror QM2 respectively connected to the third port and the fourth port of the first beam splitter BS 1.
Preferably, the second reflection module is a third polarization beam splitter PBS3, two input ports of the third polarization beam splitter PBS3 are respectively connected with a port three and a port four of the first beam splitter BS1 correspondingly, and two output ports of the third polarization beam splitter PBS3 are directly connected through polarization maintaining fibers to form a third annular structure.
Preferably, the post-processing algorithm is a Toeplitz matrix algorithm based on a fast fourier transform: constructing a Toeplitz matrix, and multiplying the Toeplitz matrix with the original random sequence to obtain the extracted quantum random number.
Preferably, an optical fiber isolator is further arranged between the laser LD and the first port one of the first polarization beam splitter PBS1, for passing the light pulse emitted by the laser and isolating the light signal from the first port one of the first polarization beam splitter PBS 1.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a quantum key distribution transmitting end based on real-time generation of quantum random numbers, which is characterized in that a path of output optical signals which are not used by a reflective interferometer are reflected back to the interferometer to interfere by a multiplexing laser to obtain random light intensity signals generated by random phase fluctuation of the laser, the random light intensity signals are converted into random electric signals by a high-speed photoelectric detector, and a random signal acquisition processing module is integrated with a QKD main control module, so that the quantum random numbers and the quantum key distribution can be simultaneously carried out, and the complexity and the cost of a system are reduced. In addition, the photoelectric detector can be used for realizing high-speed quantum random number generation, and the requirements of quantum key distribution decoy state modulation and quantum state coding can be met.
Drawings
FIG. 1 is a schematic block diagram of a quantum key distribution transmitting end based on real-time generation of quantum random numbers;
FIG. 2 is a schematic representation of the evolution of a first component and a second component in the present invention;
FIG. 3 is a schematic block diagram of a first embodiment of a quantum key distribution transmitting end based on real-time generation of quantum random numbers according to the present invention;
FIG. 4 is a schematic block diagram of a second embodiment of a quantum key distribution transmitting end based on real-time generation of quantum random numbers according to the present invention;
fig. 5 is a schematic block diagram of a third embodiment of a quantum key distribution transmitting end based on real-time generation of quantum random numbers.
Detailed Description
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.
As shown in fig. 1, a quantum key distribution transmitting end based on real-time generation of quantum random numbers comprises a laser LD, a first polarization beam splitter PBS1, a first beam splitter BS1, a first reflection module, a second polarization beam splitter PBS2, an intensity modulator IM, a phase modulator PM, an adjustable optical attenuator VOA, a photoelectric detector PD and a main control module;
the laser LD is connected with a port I of the first polarization beam splitter PBS1, and a port II and a port III of the first polarization beam splitter PBS1 are correspondingly connected with a port I of the first beam splitter BS1 and the first reflection module respectively; the second port, the third port and the fourth port of the first beam splitter BS1 are correspondingly connected with the first port of the second polarization beam splitter PBS2, the first port of the second reflection module and the second port of the second reflection module through optical fibers with different lengths respectively; the second port and the third port of the second polarization beam splitter PBS2 are respectively and correspondingly connected with one end of the intensity modulator IM and the photoelectric detector PD; the other end of the intensity modulator IM is connected with the phase modulator PM and then is connected with one end of the adjustable optical attenuator VOA; the other end of the variable optical attenuator VOA is used as an output port of the transmitting end;
the laser LD is used for generating optical pulses with random phases with period T;
the first polarization beam splitter PBS1 is used for transmitting horizontally polarized light pulses;
the first beam splitter BS1 and the second reflection module form a reflection type unequal arm interferometer with the arm length delay time of T/2, and the reflection type unequal arm interferometer is used for splitting an optical pulse incident to a first port of the first beam splitter BS1 into a first component and a second component;
the first component and the second component both comprise two sub-pulses with the time difference of T/2 and are in a vertical polarization state, and are emitted from a port I and a port II of the first beam splitter BS1 respectively;
the first polarization beam splitter PBS1 is further configured to reflect the first component incident from the second port thereof to the first reflection module, and reflect the first component reflected by the first reflection module to the first port of the first beam splitter BS 1;
the reflective unequal-arm interferometer is further used for interfering the light pulses with different phases in the first component to generate a horizontal polarized random light intensity signal emitted from the second port of the first beam splitter BS 1;
the second polarizing beam splitter PBS2 is used to transmit the random light intensity signal of horizontal polarization to the photodetector PD and reflect the second component of vertical polarization to the intensity modulator IM;
the photodetector PD is configured to convert a random light intensity signal into an electrical signal;
the intensity modulator IM is used for randomly modulating the second component into a signal state or a decoy state;
the phase modulator PM is used for phase encoding the second component;
the variable optical attenuator VOA is used for attenuating the second component subjected to phase encoding to the single photon magnitude to generate a quantum state;
the main control module is used for triggering the laser; the method comprises the steps of generating initial random bits, performing analog-to-digital conversion on an electric signal of a photoelectric detector PD, sampling, and obtaining a quantum random number through a post-processing algorithm; and for providing the intensity modulator IM and the phase modulator PM with drive voltages based on the quantum random numbers generated in real time.
The specific working principle is as follows:
the main control module triggers the laser LD to generate horizontal polarized light pulse with random phase and period T, the pulse is directly transmitted from a first port to a second port of the first polarization beam splitter PBS1, enters a reflective unequal arm interferometer with arm length delay time difference T/2 formed by the first beam splitter BS1 and the second reflective module, and is split into a first component and a second component; the first component and the second component both comprise two sub-pulses with a time difference of T/2 and are both vertically polarized, exiting from port one and port two of the first beam splitter BS1, respectively. The evolution of the first and second components is shown in fig. 2.
The first component is incident to the port II of the first polarization beam splitter PBS1, reflected to the port III thereof, reflected back to the port III of the first polarization beam splitter PBS1 after reaching the first reflection module, still vertically polarized, reflected to the port II, and then reaching the port I of the first beam splitter BS1 again, and enters the reflective unequal arm interferometer, wherein the component of the long walking arm lags the component of the short walking arm by T/2 time during emergent, so that the ith light pulse of the short walking arm interferes with the ith-1 light pulse of the long walking arm, and the (i+1) light pulse of the short walking arm interferes with the ith light pulse of the long walking arm, thereby realizing interference between adjacent light pulses generated by the laser. For the interference between the ith light pulse of the short arm and the ith light pulse of the long arm, as the two light pulses have the same initial phase, the phase difference between the two light pulses is determined by the optical path difference of the long and short arms of the interferometer, and the phase drift of the interferometer is relatively slow, so that the interference result can be regarded as a direct current component and can be directly filtered. The polarization of the first component is rotated by 90 degrees after being reflected by the second reflection module, and the first component is changed into horizontal polarization, and the two interference results are transmitted from the first polarization beam splitter PBS1 and the second polarization beam splitter PBS2 respectively. The interference result transmitted from the first polarization beam splitter PBS1 may be isolated by the optical fiber isolator so as not to affect the laser LD; the interference result transmitted from the second polarization beam splitter PBS2 enters the photodetector PD for detection.
Pulsed lasers produce light pulse signals of horizontal polarization with random phase whose electric field can be written as
Wherein, the liquid crystal display device comprises a liquid crystal display device,the amplitude, frequency and phase of the optical pulse signal are respectively. The adjacent light pulses are interfered, and the obtained interference result is that
The random electric signal generated after the direct current component is detected and filtered by the photoelectric detector PD is
Wherein, the liquid crystal display device comprises a liquid crystal display device,for the detection efficiency of the photodetector PD, < >>Is the phase difference between adjacent optical pulse signals.
The random electric signal is converted into a digital signal through an analog-to-digital conversion module, namely, the original random bit is obtained, then the randomness of the random original random bit is extracted according to a post-processing algorithm such as toeplitz matrix multiplication and the like, and finally, the quantum random number with true randomness is output.
Each pulse of the second component comprises two sub-pulses with a time interval of T/2 as the previous time pattern respectivelyAnd the latter time mode->The light enters the first port of the second polarization beam splitter PBS2, is reflected to the second port, enters the intensity modulator IM and is modulated into a signal state or a decoy state, and after the phase difference between the two sub-pulses is modulated by the phase modulator PM, the light is attenuated to a single photon level by the adjustable optical attenuator VOA to generate a quantum state of
I.e. phase encoding is achieved.
The main control module converts the quantum random number generated in real time into corresponding driving voltage for the intensity modulator IM to randomly modulate the signal state or the decoy state, and the phase modulator PM to randomly modulate the phase.
As shown in fig. 3, embodiment one:
the first reflecting module is a reflecting mirror M.
The second reflection module includes a first faraday mirror FM1 and a second faraday mirror FM2 respectively connected to a third port and a fourth port of the first beam splitter BS 1.
An embodiment of the method comprises the following specific working procedures:
the main control module triggers the laser LD to generate horizontal polarized light pulse with random phase and period T, the pulse is directly transmitted from a first port to a second port of the first polarization beam splitter PBS1, enters a reflective unequal arm interferometer with arm length delay time difference T/2 formed by the first beam splitter BS1, the first Faraday reflector FM1 and the second Faraday reflector FM2, and is split into a first component and a second component; the first component and the second component both comprise two sub-pulses with a time difference of T/2 and are both vertically polarized, exiting from port one and port two of the first beam splitter BS1, respectively.
The first component is incident to the port II of the first polarization beam splitter PBS1, reflected to the port III thereof, reflected back to the port III of the first polarization beam splitter PBS1 after reaching the reflector M, still vertically polarized, reflected to the port II, and then again reaching the port I of the first beam splitter BS1, and enters the reflective unequal arm interferometer, wherein the component of the long walking arm lags the component of the short walking arm by T/2 time during emergent, so that the ith light pulse of the short walking arm interferes with the ith-1 light pulse of the long walking arm, and the (i+1) light pulse of the short walking arm interferes with the ith light pulse of the long walking arm, thereby realizing interference between adjacent light pulses generated by the laser. For the interference between the ith light pulse of the short arm and the ith light pulse of the long arm, as the two light pulses have the same initial phase, the phase difference between the two light pulses is determined by the optical path difference of the long and short arms of the interferometer, and the phase drift of the interferometer is relatively slow, so that the interference result can be regarded as a direct current component and can be directly filtered. The first component is reflected by the first faraday mirror FM1 and the second faraday mirror FM2, and then the polarization is rotated by 90 ° to become horizontal polarization, and the two interference results are transmitted from the first polarizing beam splitter PBS1 and the second polarizing beam splitter PBS2, respectively. The interference result transmitted from the first polarization beam splitter PBS1 may be isolated by the optical fiber isolator so as not to affect the laser LD; the interference result transmitted from the second polarization beam splitter PBS2 enters the photodetector PD for detection.
Pulsed lasers produce light pulse signals of horizontal polarization with random phase whose electric field can be written as
Wherein, the liquid crystal display device comprises a liquid crystal display device,the amplitude, frequency and phase of the optical pulse signal are respectively. The adjacent light pulses are interfered, and the obtained interference result is that
The random electric signal generated after the direct current component is detected and filtered by the photoelectric detector PD is
Wherein, the liquid crystal display device comprises a liquid crystal display device,for the detection efficiency of the photodetector PD, < >>Is the phase difference between adjacent optical pulse signals.
The random electric signal is converted into a digital signal through an analog-to-digital conversion module, namely, the original random bit is obtained, then the randomness of the random original random bit is extracted according to a post-processing algorithm such as toeplitz matrix multiplication and the like, and finally, the quantum random number with true randomness is output.
Each pulse of the second component comprises two sub-pulses with a time interval of T/2 as the previous time pattern respectivelyAnd the latter time mode->The light enters the first port of the second polarization beam splitter PBS2, is reflected to the second port, enters the intensity modulator IM and is modulated into a signal state or a decoy state, and after the phase difference between the two sub-pulses is modulated by the phase modulator PM, the light is attenuated to a single photon level by the adjustable optical attenuator VOA to generate a quantum state of
I.e. phase encoding is achieved.
The main control module converts the quantum random number generated in real time into corresponding driving voltage for the intensity modulator IM to randomly modulate the signal state or the decoy state, and the phase modulator PM to randomly modulate the phase.
As shown in fig. 4, embodiment two:
the first reflection module is a second beam splitter BS2, and two output ports of the second beam splitter BS2 are directly connected through polarization maintaining fibers to form a first annular structure.
The second reflection module includes a first quarter-wave plate mirror QM1 and a second quarter-wave plate mirror QM2 respectively connected to the third port and the fourth port of the first beam splitter BS 1.
The second specific working process of the embodiment comprises the following steps:
the main control module triggers the laser LD to generate horizontal polarized light pulse with a period of T and a random phase, the horizontal polarized light pulse is directly transmitted from a first port to a second port of the first polarization beam splitter PBS1, enters a reflective unequal arm interferometer with an arm length delay difference of T/2 formed by the first beam splitter BS1, the first quarter wave plate reflector QM1 and the second quarter wave plate reflector QM2, and is split into a first component and a second component; the first component and the second component each comprise two sub-pulses with a time difference T/2, exiting from port one and port two of the first beam splitter BS1, respectively. The transmission matrix of QM can be written as
The horizontal polarization becomes vertical polarization after its action and the vertical polarization becomes horizontal polarization. Thus, both the first and second components are vertically polarized.
The first component is incident on port two of the first polarizing beam splitter PBS1 and is reflected to port three thereof. Then, the two components reach the second beam splitter BS2, are split into two components with the same amplitude, and respectively propagate in opposite directions in the first annular structure, so that the two components undergo the same phase change, and return to the second beam splitter BS2 again to interfere at the same time, and all the components can exit from an input port of the second beam splitter BS2 due to the phase difference of 0, namely, the reflection of the first component is completed, and the polarization remains unchanged.
The first component is then reflected back to port three of the first polarization beam splitter PBS1, still vertically polarized, reflected to port two, and then again to port one of the first beam splitter BS1, into the reflective unequal arm interferometer, where the component of the long walking arm lags the component of the short walking arm by T/2 of the time when exiting, so that the i-1 th light pulse of the short walking arm interferes with the i-1 th light pulse of the long walking arm, and the i+1 th light pulse of the short walking arm interferes with the i-th light pulse of the long walking arm, thereby achieving interference between adjacent light pulses generated by the laser. For the interference between the ith light pulse of the short arm and the ith light pulse of the long arm, as the two light pulses have the same initial phase, the phase difference between the two light pulses is determined by the optical path difference of the long and short arms of the interferometer, and the phase drift of the interferometer is relatively slow, so that the interference result can be regarded as a direct current component and can be directly filtered. The first component is reflected by the first faraday mirror FM1 and the second faraday mirror FM2, and then the polarization is rotated by 90 ° to become horizontal polarization, and the two interference results are transmitted from the first polarizing beam splitter PBS1 and the second polarizing beam splitter PBS2, respectively. The interference result transmitted from the first polarization beam splitter PBS1 may be isolated by the optical fiber isolator so as not to affect the laser LD; the interference result transmitted from the second polarization beam splitter PBS2 enters the photodetector PD for detection.
Pulsed lasers produce light pulse signals of horizontal polarization with random phase whose electric field can be written as
Wherein, the liquid crystal display device comprises a liquid crystal display device,the amplitude, frequency and phase of the optical pulse signal are respectively. The adjacent light pulses are interfered, and the obtained interference result is that
The random electric signal generated after the direct current component is detected and filtered by the photoelectric detector PD is
Wherein, the liquid crystal display device comprises a liquid crystal display device,for the detection efficiency of the photodetector PD, < >>Is the phase difference between adjacent optical pulse signals.
The random electric signal is converted into a digital signal through an analog-to-digital conversion module, namely, the original random bit is obtained, then the randomness of the random original random bit is extracted according to a post-processing algorithm such as toeplitz matrix multiplication and the like, and finally, the quantum random number with true randomness is output.
Each pulse of the second component comprises two sub-pulses with a time interval of T/2 as the previous time pattern respectivelyAnd the latter time mode->The first port incident on the second polarization beam splitter PBS2 is reflected to the end thereofA second port, then enters an intensity modulator IM to be modulated into a signal state or a decoy state, and after the phase difference between two sub-pulses is modulated by the phase modulator PM, the phase difference is attenuated to the single photon magnitude by a tunable optical attenuator VOA to generate a quantum state of
I.e. phase encoding is achieved.
The main control module converts the quantum random number generated in real time into corresponding driving voltage for the intensity modulator IM to randomly modulate the signal state or the decoy state, and the phase modulator PM to randomly modulate the phase.
As shown in fig. 5, embodiment three:
the first reflection module is a circulator CIR, and a port I and a port III of the circulator CIR are directly connected through a polarization maintaining fiber to form a second annular structure.
The second reflection module is a third polarization beam splitter PBS3, two input ports of the third polarization beam splitter PBS3 are respectively correspondingly connected with a port III and a port IV of the first beam splitter BS1, and two output ports of the third polarization beam splitter PBS3 are directly connected through polarization maintaining fibers to form a third annular structure.
The third specific working procedure of the embodiment comprises the following steps:
the main control module triggers the laser LD to generate horizontal polarized light pulse with a random phase and a period of T, the horizontal polarized light pulse is directly transmitted from a first port to a second port of the first polarization beam splitter PBS1, enters a reflective unequal arm interferometer with an arm length delay time of T/2 formed by the first beam splitter BS1 and the third polarization beam splitter PBS3, and is split into a first component and a second component; the first component and the second component each comprise two sub-pulses with a time difference T/2, exiting from port one and port two of the first beam splitter BS1, respectively. Since the third annular structure formed by connecting the two output ports of the third polarization beam splitter PBS3 through the polarization maintaining fiber corresponds to the function of QM, the transmission matrix can be written as
The horizontal polarization becomes vertical polarization after its action and the vertical polarization becomes horizontal polarization. Thus, both the first and second components are vertically polarized.
The first component is incident on port two of the first polarizing beam splitter PBS1 and is reflected to port three thereof. And then the light reaches the second port of the circulator CIR, exits from the third port of the circulator CIR, is transmitted to the first port of the circulator CIR along the second annular structure formed by the polarization maintaining optical fiber, and finally exits from the second port of the circulator CIR, so that the reflection of the first component is finished, and the polarization is kept unchanged.
The first component is then reflected back to port three of the first polarization beam splitter PBS1, still vertically polarized, reflected to port two, and then again to port one of the first beam splitter BS1, into the reflective unequal arm interferometer, where the component of the long walking arm lags the component of the short walking arm by T/2 of the time when exiting, so that the i-1 th light pulse of the short walking arm interferes with the i-1 th light pulse of the long walking arm, and the i+1 th light pulse of the short walking arm interferes with the i-th light pulse of the long walking arm, thereby achieving interference between adjacent light pulses generated by the laser. For the interference between the ith light pulse of the short arm and the ith light pulse of the long arm, as the two light pulses have the same initial phase, the phase difference between the two light pulses is determined by the optical path difference of the long and short arms of the interferometer, and the phase drift of the interferometer is relatively slow, so that the interference result can be regarded as a direct current component and can be directly filtered. The first component is reflected by the first faraday mirror FM1 and the second faraday mirror FM2, and then the polarization is rotated by 90 ° to become horizontal polarization, and the two interference results are transmitted from the first polarizing beam splitter PBS1 and the second polarizing beam splitter PBS2, respectively. The interference result transmitted from the first polarization beam splitter PBS1 may be isolated by the optical fiber isolator so as not to affect the laser LD; the interference result transmitted from the second polarization beam splitter PBS2 enters the photodetector PD for detection.
Pulsed lasers produce light pulse signals of horizontal polarization with random phase whose electric field can be written as
Wherein, the liquid crystal display device comprises a liquid crystal display device,the amplitude, frequency and phase of the optical pulse signal are respectively. The adjacent light pulses are interfered, and the obtained interference result is that
The random electric signal generated after the PD is detected by the photoelectric detector and the direct current component is filtered is
Wherein, the liquid crystal display device comprises a liquid crystal display device,for the detection efficiency of the photodetector PD, < >>Is the phase difference between adjacent optical pulse signals.
The random electric signal is converted into a digital signal through an analog-to-digital conversion module, namely, the original random bit is obtained, then the randomness of the random original random bit is extracted according to a post-processing algorithm such as toeplitz matrix multiplication and the like, and finally, the quantum random number with true randomness is output.
Each pulse of the second component comprises two sub-pulses with a time interval of T/2 as the previous time pattern respectivelyAnd the latter time mode->The first light incident on the first port of the second polarization beam splitter PBS2 is reflected to the second port thereof, then enters the intensity modulator IM to be modulated into a signal state or a decoy state, and then is modulated by the phase modulator PM to form two signalsAfter the phase difference between the sub-pulses, the phase difference is attenuated to the single photon magnitude by the adjustable optical attenuator VOA, and the quantum state is generated
I.e. phase encoding is achieved.
The main control module converts the quantum random number generated in real time into corresponding driving voltage for the intensity modulator IM to randomly modulate the signal state or the decoy state, and the phase modulator PM to randomly modulate the phase.
By integrating the embodiments of the invention, the invention provides a quantum key distribution transmitting end based on real-time generation of quantum random numbers, which reflects one path of output optical signals which are not used by a reflective interferometer back to the interferometer for interference by a multiplexing laser to obtain random light intensity signals generated by random phase fluctuation of the laser, converts the random light intensity signals into random electric signals by a high-speed photoelectric detector, integrates a random signal acquisition processing module with a QKD main control module, can realize simultaneous quantum random number and quantum key distribution, and reduces the complexity and cost of a system. In addition, the photoelectric detector can be used for realizing high-speed quantum random number generation, and the requirements of quantum key distribution decoy state modulation and quantum state coding can be met.
Claims (9)
1. The quantum key distribution transmitting end based on real-time generation of the quantum random number is characterized by comprising a laser LD, a first polarization beam splitter PBS1, a first beam splitter BS1, a first reflection module, a second polarization beam splitter PBS2, an intensity modulator IM, a phase modulator PM, an adjustable optical attenuator VOA, a photoelectric detector PD and a main control module;
the laser LD is connected with a port I of the first polarization beam splitter PBS1, and a port II and a port III of the first polarization beam splitter PBS1 are correspondingly connected with a port I of the first beam splitter BS1 and the first reflection module respectively; the second port, the third port and the fourth port of the first beam splitter BS1 are correspondingly connected with the first port of the second polarization beam splitter PBS2, the first port of the second reflection module and the second port of the second reflection module through optical fibers with different lengths respectively; the second port and the third port of the second polarization beam splitter PBS2 are respectively and correspondingly connected with one end of the intensity modulator IM and the photoelectric detector PD; the other end of the intensity modulator IM is connected with the phase modulator PM and then is connected with one end of the adjustable optical attenuator VOA; the other end of the variable optical attenuator VOA is used as an output port of the transmitting end;
the laser LD is used for generating optical pulses with random phases with period T;
the first polarization beam splitter PBS1 is used for transmitting horizontally polarized light pulses;
the first beam splitter BS1 and the second reflection module form a reflection type unequal arm interferometer with the arm length delay time of T/2, and the reflection type unequal arm interferometer is used for splitting an optical pulse incident to a first port of the first beam splitter BS1 into a first component and a second component;
the first component and the second component both comprise two sub-pulses with the time difference of T/2 and are in a vertical polarization state, and are emitted from a port I and a port II of the first beam splitter BS1 respectively;
the first polarization beam splitter PBS1 is further configured to reflect the first component incident from the second port thereof to the first reflection module, and reflect the first component reflected by the first reflection module to the first port of the first beam splitter BS 1;
the reflective unequal-arm interferometer is further used for interfering the light pulses with different phases in the first component to generate a horizontal polarized random light intensity signal emitted from the second port of the first beam splitter BS 1;
the second polarizing beam splitter PBS2 is used to transmit the random light intensity signal of horizontal polarization to the photodetector PD and reflect the second component of vertical polarization to the intensity modulator IM;
the photodetector PD is configured to convert a random light intensity signal into an electrical signal;
the intensity modulator IM is used for randomly modulating the second component into a signal state or a decoy state;
the phase modulator PM is used for phase encoding the second component;
the variable optical attenuator VOA is used for attenuating the second component subjected to phase encoding to the single photon magnitude to generate a quantum state;
the main control module is used for triggering the laser; the method comprises the steps of generating initial random bits, performing analog-to-digital conversion on an electric signal of a photoelectric detector PD, sampling, and obtaining a quantum random number through a post-processing algorithm; and for providing the intensity modulator IM and the phase modulator PM with drive voltages based on the quantum random numbers generated in real time.
2. The quantum key distribution transmitting terminal based on real-time generation of quantum random numbers according to claim 1, wherein the first reflection module is a mirror M.
3. The quantum key distribution transmitting end based on real-time generation of quantum random numbers according to claim 1, wherein the first reflection module is a second beam splitter BS2, and two output ports of the second beam splitter BS2 are directly connected through polarization maintaining fibers to form a first annular structure.
4. The quantum key distribution transmitting terminal based on real-time generation of quantum random numbers according to claim 1, wherein the first reflection module is a circulator CIR, and a port one and a port three of the circulator CIR are directly connected through a polarization maintaining fiber to form a second annular structure.
5. The quantum key distribution transmitting terminal based on real-time generation of quantum random numbers according to claim 1 or 2 or 3 or 4, wherein the second reflection module comprises a first faraday mirror FM1 and a second faraday mirror FM2 respectively connected to a third port and a fourth port of the first beam splitter BS 1.
6. The quantum key distribution transmitting terminal based on real-time generation of quantum random numbers according to claim 1 or 2 or 3 or 4, wherein the second reflection module comprises a first quarter-wave plate mirror QM1 and a second quarter-wave plate mirror QM2 respectively connected to a third port and a fourth port of the first beam splitter BS 1.
7. The quantum key distribution transmitting end based on real-time generation of quantum random numbers according to claim 1, 2, 3 or 4, wherein the second reflection module is a third polarization beam splitter PBS3, two input ports of the third polarization beam splitter PBS3 are respectively connected with a port three and a port four of the first beam splitter BS1 correspondingly, and two output ports of the third polarization beam splitter PBS3 are directly connected through polarization maintaining fibers to form a third annular structure.
8. The quantum key distribution transmitting end based on real-time generation of quantum random numbers according to claim 7, wherein the post-processing algorithm is a Toeplitz matrix algorithm based on fast fourier transform: constructing a Toeplitz matrix, and multiplying the Toeplitz matrix with the original random sequence to obtain the extracted quantum random number.
9. The quantum key distribution transmitting terminal based on real-time generation of quantum random numbers according to claim 8, wherein an optical fiber isolator is further disposed between the laser LD and the port one of the first polarization beam splitter PBS1, for passing the light pulse emitted by the laser and isolating the light signal from the port one of the first polarization beam splitter PBS 1.
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