CN110518984A - Method for synchronizing time and system in a kind of quantum secret communication - Google Patents
Method for synchronizing time and system in a kind of quantum secret communication Download PDFInfo
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- CN110518984A CN110518984A CN201810488343.5A CN201810488343A CN110518984A CN 110518984 A CN110518984 A CN 110518984A CN 201810488343 A CN201810488343 A CN 201810488343A CN 110518984 A CN110518984 A CN 110518984A
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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
- H04B10/70—Photonic quantum communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
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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
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Abstract
The present invention provides method for synchronizing time and system in a kind of quantum secret communication, comprising steps of S1, output signal light and synchronizable optical；S2, by signal light with after synchronous optical coupling by same root less fundamental mode optical fibre transmission；S3, the signal light after coupling and synchronizable optical are received and is split signal light and synchronizable optical；S4, detectable signal light and synchronizable optical determine the link transmission delay between signal light light pulse and synchronizable optical light pulse, synchronize amendment to signal light；S5, frame number is carried out to synchronizable optical, and label is carried out to each signal light light pulse according to the synchronizable optical optical pulse time interval of each signal light light pulse and its affiliated frame；S6, the frame number for identifying synchronizable optical, the time interval of synchronizable optical light pulse of the measuring signal light light pulse apart from its affiliated frame；And the label of the signal light light pulse received according to time interval judgement；The label of the signal light light pulse received and the label of the signal light light pulse of transmission are corresponded.
Description
Technical field
The present invention relates to Technique on Quantum Communication fields, more particularly to the method for synchronizing time in a kind of quantum secret communication
And system.
Background technique
Quantum secret communication is based on fundamental principles of quantum mechanics, the characteristic with unconditional security.Quantum secret communication with
Single photon realizes that the information privacy between terminal is safely transmitted as carrier.Nearly more than ten years, Quantum Secure Communication are at full speed
Development, core quantum key distribution (QKD) have been realized in a series of engineering applications, are national security, finance, electric power etc.
Realm information business provides quantum safety guarantee.
Quantum key distribution is divided into transmitting terminal Alice and receiving end Bob, mostly uses single mode optical fiber as transmission channel.Hair
Sending end Alice randomly choose one group of basic vector ("+" basic vector or "×" basic vector) and some state under this basic vector to photon into
Row coding, can be obtained four kinds of polarization state photons, is horizontal state of polarization H (being denoted as →), perpendicular polarisation state V (being denoted as ↑) ,+45 ° respectively
Polarization state P (Ji Zuo ↗), -45 ° of polarization state N (Ji Zuo ↘).Photon receiving end Bob is received after transmission.Bob is received
To after photon, also randomly chooses one group of basic vector and measure, and measurement result is recorded.Alice and Bob selects basic vector
It is all random and mutually independent.
Then, Alice and Bob passes through classical channel progress basic vector comparison, i.e. Bob announces selected when its measurement photon
Basic vector, Alice compare the basic vector and its selected basic vector when sending photon of Bob selection, retain and select the identical data of basic vector,
The data of different basic vectors are selected to abandon.Then pass through error correction, privacy amplification and etc. obtain safe key.
QKD equipment needs to carry out self calibration before operating normally work.The work of QKD equipment Alignment mainly includes light intensity
Feedback, delayed sweep, polarization feedback and synchronous amendment.
Light intensity feedback function completes intensity stability maintenance, and the fluctuation that compensation intensity modulator is generated by external environment variation is allowed to
It is maintained at preset state.Delayed sweep function completes the optimization of the detection efficient to the snowslide single-photon detector of gate.Gate
The gate-control signal of single-photon detector passes through the delay chip of 4 road adjustable delays, and the delay value by adjusting the delay chip obtains
To detection efficient count rate curve and maximizing, the setting value of delay chip in this case is optimal value.Polarization feedback
Function completes polarization state monitoring and the feedback compensation of the QKD system signal pulse based on polarization encoder.
Finally, synchronizing amendment step.Synchronous debugging functions complete the time for the signal pulse that detector receives
Difference relative to synchronizable optical pulse arrival time measures, because optical fiber link and electronics circuit can be to signal lights and synchronizable optical
Generate different link delays.So starting synchronous amendment in system initialisation phase, obtained by synchronous debugging functions above-mentioned
Time difference can be used for subsequent judgement detection time position and send the relativeness between sequence location.
Synchronous debugging functions guarantee that quantum secret communication both sides Alice and Bob is carrying out the time synchronization in communication process,
Ensure that both sides are to carry out basic vector comparison for basic vector belonging to the same photon state, is not in dislocation.Clock Synchronization Technology is
The key technology of quantum secret communication system has decided on whether that safe quantum key can be generated.
Existing Clock Synchronization Technology mainly includes two kinds.First method is that transmission of quantum letter is distinguished by two optical fiber
Number light synchronization optical signal synchronous with clock.It is additional to occupy an optical fiber as synchronizable optical signal channel significant wastage optical fiber
Resource.Moreover, quantum signal light and synchronizable optical are transmitted in two optical fiber respectively, the transmission environment of the two is different, is being transmitted across
Haves the defects that relative phase shake in journey.Second is the method based on wavelength-division multiplex, by same root optical fiber come transmission quantity
Subsignal light and synchronizable optical.For example, synchronous optical wavelength is different from quantum signal optical wavelength, and synchronous light frequency proportion subsignal
Light frequency is much smaller.Synchronizable optical and quantum signal light are coupled into same root single mode optical fiber by wavelength division multiplexer to be transmitted.
Pass through the phase difference of time delay module control amount subsignal light and synchronizable optical, it is ensured that synchronous optical signal will not generate quantum signal light
Crosstalk.
For example, a length of 1550.12nm of quantum signal light wave, the repetition rate that shines is 40MHz, and synchronous optical wavelength is
1570nm, the repetition rate that shines are 100KHz.Quantum signal light of the synchronizable optical as reference signal, between two synchronous optical signals
It forms a frame and it is numbered.Bob receives synchronous optical signal and can determine affiliated quantum according to synchronizable optical number
Which frame signal light belongs to.The time slot between some quantum signal light and synchronizable optical is measured, again to determine the quantum signal
Light belong to the frame which, so as to realize the time synchronization between Alice and Bob.
Method for distinguishing transmission of quantum signal light and synchronizable optical using two optical fiber, fiber resource waste are serious.
Moreover, being affected by the external environment also different because quantum signal light is different with synchronizable optical transmission channel, cause the opposite phase of the two
The defect of position shake, and influence of the defect to high repetition frequency system is fatal.Wavelength-division multiplex is passed through for simple optical fiber
Technology by quantum signal light with synchronize be optically coupled into the method transmitted in same root optical fiber, although can realize well
Time synchronization between Alice and Bob, but because synchronizable optical needs additionally to occupy a wavelength channel, optical-fiber network medium wavelength money
Source is valuable and limited, occupies the establishment that wavelength channel is unfavorable for extensive quantum secret communication network.
Summary of the invention
In view of the foregoing deficiencies of prior art, the purpose of the present invention is to provide in a kind of quantum secret communication when
Between synchronous method and system, for solving the problems, such as that existing double-fiber simultaneous techniques and single fiber wavelength-division simultaneous techniques are individually present.
Method for transmitting signal light and synchronizable optical respectively using two optical fiber, fiber resource waste is serious, and signal light and
Synchronizable optical transmission channel is different, is affected by the external environment also different, easily causes the two relative phase shake；And simple optical fiber
The method for carrying out time synchronization by wavelength-division multiplex technique occupies wavelength channel, is unfavorable for extensive quantum secret communication network
Establishment.
The present invention provides the method for synchronizing time in a kind of quantum secret communication, comprising steps of S1, output signal light and same
Walk light；S2, by the signal light with after the synchronous optical coupling by same root less fundamental mode optical fibre transmission；S3, coupling is received
The signal light and the synchronizable optical are simultaneously split by the signal light and the synchronizable optical afterwards；S4, the detection signal
Light and the synchronizable optical determine the link transmission delay between the signal light light pulse and the synchronizable optical light pulse, to institute
It states signal light and synchronizes amendment；S5, frame number is carried out to the synchronizable optical, and according to each signal light light pulse and its
The synchronizable optical optical pulse time interval of affiliated frame carries out label to each signal light light pulse；S6, identification are described same
The frame number for walking light measured between time of the signal light light pulse apart from the synchronizable optical light pulse of its affiliated frame
Every；And the label of the signal light light pulse received according to time interval judgement；The signal light that will be received
The label of the signal light light pulse of the label and transmission of light pulse corresponds.
In one embodiment of the invention, the step S1 further include: the signal light is subjected to polarization state preparation and is declined
After subtracting, the other tetra- road polarised light of H, V, P, N of single-photon-level is prepared.
In one embodiment of the invention, the step S1 further include: the synchronizable optical of outgoing decays；It will decline
The mode of the synchronizable optical after subtracting is converted to higher order mode by basic mode.
In one embodiment of the invention, the step S1 further include: determine that the signal light light pulse is opposite when sending
In the first time interval of the synchronizable optical light pulse；The step S4 further include: determine signal light light pulse when reception
The second time interval relative to the synchronizable optical light pulse；According to the first time interval and second time interval it
Between difference determine the link transmission between the signal light light pulse and the synchronizable optical light pulse be delayed.
The present invention also provides the clock synchronization systems in a kind of quantum secret communication, comprising: synchronous light emitting devices is used
Frame number is carried out in outgoing synchronizable optical, and to the synchronizable optical；Signal light emitting end is used for output signal light, and according to described
The time interval of signal light light pulse and the synchronizable optical light pulse of its affiliated frame carries out label to each signal light light pulse；
Pattern multiplexer, for by the signal light with after the synchronous optical coupling by same root less fundamental mode optical fibre transmission；Mode
Demultiplexer, for receiving the signal light after coupling and the synchronizable optical and carrying out the signal light and the synchronizable optical
Beam splitting；PIN detector identifies the frame number of the synchronizable optical for detecting the synchronizable optical；Single-photon detector is used
In detecting the signal light, and measure between time of the signal light light pulse apart from the synchronizable optical light pulse of its affiliated frame
Every；And the label of the signal light light pulse received according to time interval judgement；The signal light that will be received
The label of the signal light light pulse of the label and transmission of light pulse corresponds；Correction module, for determining the signal
Link transmission delay between light light pulse and the synchronizable optical light pulse, synchronizes amendment to the signal light.
In one embodiment of the invention, the signal light emitting end further includes polarization state preparation and attenuation module, is used for
The signal light is subjected to polarization state preparation and decaying, prepares the other tetra- road polarised light of H, V, P, N of single-photon-level.
In one embodiment of the invention, the synchronous light emitting devices includes: synchronous optical transmitting set, for being emitted synchronization
Light；Optical attenuator, for the synchronizable optical of outgoing to decay；Mode converter, for the synchronization after decaying
The mode of light is converted to higher order mode by basic mode.
In one embodiment of the invention, the signal light emitting end is also used to determine signal light light pulse when transmission
First time interval relative to the synchronizable optical light pulse；The single-photon detector is also used to determine signal when reception
Second time interval of the light light pulse relative to the synchronizable optical light pulse；The correction module is also used to according to described first
Difference between time interval and second time interval determine the signal light light pulse and the synchronizable optical light pulse it
Between link transmission delay.
As described above, method for synchronizing time and system in a kind of quantum secret communication of the invention, have beneficial below
Effect:
Without increasing additional fiber channel, by mode division multiplexing device by quantum signal light with synchronize be optically coupled into it is same
Root fibre channel transmission, this measure dramatically save fiber resource.
Moreover, synchronizable optical is not take up wavelength channel for multichannel QKD wavelength-division multiplex system, being equivalent to reduces every road amount
The wavelength-division multiplex Insertion Loss of subsignal light improves every road QKD service feature, including at code rate, transmission range etc., extensive setting up
When quantum secret communication network, there is objective economic benefit.
Detailed description of the invention
Fig. 1 is shown as in the present invention process blocks schematic diagram of the method for synchronizing time in quantum secret communication.
Fig. 2 is shown as in the present invention structural schematic diagram of the clock synchronization system in quantum secret communication.
The light pulse that Fig. 3 is shown as transmitting terminal synchronizable optical and signal light when quantum secret communication in the present invention is synchronous to be corrected is shown
It is intended to.
The light pulse that Fig. 4 is shown as receiving end synchronizable optical and signal light when quantum secret communication in the present invention is synchronous to be corrected is shown
It is intended to.
The light pulse of transmitting terminal synchronizable optical and signal light is shown when Fig. 5 is shown as quantum secret communication time synchronization in the present invention
It is intended to.
The light pulse of receiving end synchronizable optical and signal light is shown when Fig. 6 is shown as quantum secret communication time synchronization in the present invention
It is intended to.
Specific embodiment
Illustrate embodiments of the present invention below by way of specific specific example, those skilled in the art can be by this specification
Other advantages and efficacy of the present invention can be easily understood for disclosed content.The present invention can also pass through in addition different specific realities
The mode of applying is embodied or practiced, the various details in this specification can also based on different viewpoints and application, without departing from
Various modifications or alterations are carried out under spirit of the invention.It should be noted that in the absence of conflict, following embodiment and implementation
Feature in example can be combined with each other.
It should be noted that illustrating the basic structure that only the invention is illustrated in a schematic way provided in following embodiment
Think, only shown in diagram then with related component in the present invention rather than component count, shape and size when according to actual implementation
Draw, when actual implementation kenel, quantity and the ratio of each component can arbitrarily change for one kind, and its assembly layout kenel
It is likely more complexity.
Referring to Fig. 1 to Fig. 6, it should however be clear that the appended diagram of this specification depicted structure, ratio, size etc., only to match
The revealed content of specification is closed, so that those skilled in the art understands and reads, is not intended to limit the invention implementable
Qualifications, therefore do not have technical essential meaning, the modification of any structure, the change of proportionate relationship or the adjustment of size,
In the case where not influencing the effect of present invention can be generated and the purpose that can reach, should all still fall in disclosed technology
In the range of Rong get Neng is covered.Meanwhile it is cited such as "upper", "lower", "left", "right", " centre " and " one " in this specification
Deng term, be merely convenient to being illustrated for narration, rather than to limit the scope of the invention, the change of relativeness
Or adjustment, under the content of no substantial changes in technology, when being also considered as the enforceable scope of the present invention.
As shown in Fig. 1 and Fig. 3 to 6, Fig. 1 is shown as in the present invention stream of the method for synchronizing time in quantum secret communication
Journey block diagram.Fig. 3 is shown as the light of transmitting terminal synchronizable optical and signal light when quantum secret communication in the present invention is synchronous to be corrected
Pulse schematic diagram.Fig. 4 is shown as the light arteries and veins of receiving end synchronizable optical and signal light when quantum secret communication in the present invention is synchronous to be corrected
Rush schematic diagram.Fig. 5 is shown as the light pulse of transmitting terminal synchronizable optical and signal light when quantum secret communication time synchronization in the present invention
Schematic diagram.The light pulse of receiving end synchronizable optical and signal light is shown when Fig. 6 is shown as quantum secret communication time synchronization in the present invention
It is intended to.The present invention provides the method for synchronizing time in a kind of quantum secret communication, comprising steps of
S1, output signal light and synchronizable optical；When initial outgoing, signal light and synchronizable optical are basic mode mode, after outgoing, together
Step light switchs to higher order mode, in one embodiment of this invention, step S1 further include: signal light is subjected to polarization state preparation and is declined
After subtracting, the other tetra- road polarised light of H, V, P, N of single-photon-level is prepared.In another embodiment of the invention, step S1 further include:
The synchronizable optical of outgoing is decayed；The mode of synchronizable optical after decaying is converted into higher order mode by basic mode.Of the invention
In another embodiment, step S1 further include: determine first time of the signal light light pulse relative to synchronizable optical light pulse when sending
Interval；
S2, by signal light with after synchronous optical coupling by same root less fundamental mode optical fibre transmission；Transmission channel is few mould light
Fibre, less fundamental mode optical fibre can realize multiplexing by increasing the mode for the light beam propagated in single-core fiber, improve transmission capacity
Under the premise of it is unobvious to the increase in demand of energy consumption.Compared with traditional single mode optical fiber, the mode field diameter of less fundamental mode optical fibre is bigger, can
Support more transmission modes, and decaying will not significantly increase.Compared with multimode fibre, less fundamental mode optical fibre transmission loss is smaller, passes
It is defeated apart from farther, the easily controllable coupling between reduction mode.
S3, the signal light after coupling and synchronizable optical are received and is split signal light and synchronizable optical；
S4, detectable signal light and synchronizable optical, determine between signal light and synchronizable optical link transmission delay, to signal light into
The synchronous amendment of row.In the starting of QKD equipment, equipment Alignment work will do it, wherein just containing synchronous amendment step.It synchronizes and repairs
Positive step be exactly in order to correct the different delay values that synchronizable optical and signal light introduce after optical fiber link and electronics circuit,
It lays the foundation for the time location of each signal light light pulse is accurately positioned.
S5, frame number is carried out to the synchronizable optical, and according to each signal light light pulse and its affiliated frame
Synchronizable optical optical pulse time interval carries out label to each signal light light pulse；
The frame number of S6, the identification synchronizable optical, measure the signal light light pulse apart from described in its affiliated frame
The time interval of synchronizable optical light pulse；And the label of the signal light light pulse received according to time interval judgement；
The label of the signal light light pulse received and the label of the signal light light pulse of transmission are corresponded.In this hair
In a bright embodiment, step S4 further include: determine that the signal light light pulse is relative to the synchronizable optical light pulse when reception
The second time interval；The signal light is determined according to the difference between the first time interval and second time interval
Link transmission delay between light pulse and the synchronizable optical light pulse.After completing synchronous amendment, sending cycle synchronizable optical and letter
Number light, synchronous light frequency are more much smaller than signal light frequency.Each synchronizable optical light pulse is followed by a string of signal light light pulses, composition
One frame light pulse signal.Sequence number is carried out to each synchronizable optical, and measures some signal light light pulse apart from frame where it
The time interval of synchronizable optical light pulse, that is, can determine the signal light light pulse belong to which frame which, the deadline is synchronous.
It is illustrated below with one embodiment of the invention, transmitting terminal goes out the signal light that emission mode is basic mode, by signal light
Polarization state preparation and attenuation module, prepare the other tetra- road polarised light of H, V, P, N of required single-photon-level.Synchronizable optical and signal light
Identical, the emission mode that goes out of synchronizable optical is basic mode.Synchronizable optical first passes through optical attenuator and carries out light intensity attenuation, then passes through mode
Converter is converted into LP11 mode or other higher order modes.Basic mode quantum signal light and high-order mode synchronizable optical pass through pattern multiplexer
Same root less fundamental mode optical fibre channel is coupled into be transmitted.In general, the link between signal light emitting end and pattern multiplexer can
Using single mode optical fiber or less fundamental mode optical fibre, the link between mode converter and pattern multiplexer uses less fundamental mode optical fibre.It is receiving
End, signal light and synchronizable optical are split by pattern demultiplexer, and the single-photon detector of signal light receiving end receives, together
It walks light and reception is detected by PIN detector.In general, single-mode optics can be used in the link between pattern demultiplexer and single-photon detector
Fine or less fundamental mode optical fibre, the link between pattern demultiplexer and PIN detector use less fundamental mode optical fibre.
As shown in Figures 3 to 6, for QKD equipment before operating normally work, system will do it initialization of calibration.It completes
After light intensity feedback, delayed sweep, polarization feedback, amendment step can be synchronized one by one for tetra- road signal light of H, V, P, N.With
For the signal light of the road H, synchronous light laser issues the recurrent pulse light that repetition rate is 100kHz, the road H signal light laser
The periodic pulse signal light that repetition rate is 100kHz is issued, synchronizable optical is identical with the wavelength of signal light.In transmitting terminal, signal light
Light pulse is fixed relative to synchronizable optical optical pulse time interval, is denoted as T1.
After optical fiber link and electronics circuit, synchronizable optical light pulse and signal light the light pulse delay detected is deposited
In difference.The time interval T2 of synchronizable optical light pulse and signal light light pulse is determined after repeatedly detecting statistics.Because of link
Postpone different, compared to the time interval T1 of synchronizable optical light pulse and signal light light pulse in transmitting terminal, is introduced in receiving end
Time interval difference DELTA T.Because determining that signal light light pulse sequence number is to rely on to measure itself and affiliated frame in receiving end
The time interval of synchronizable optical light pulse is completed.For some light pulse of transmitting terminal, with synchronizable optical optical pulse time interval
For T1, and in receiving end, the signal light light pulse and synchronizable optical optical pulse time interval detected becomes T2, T1 and T2 phase
Poor Δ T.Therefore when actually determining signal light light pulse position, need to deduct Δ T.Modified purpose is synchronized exactly for receiving end
The time interval " recovery " of signal light light pulse and synchronizable optical light pulse is at the time interval in transmitting terminal, to guarantee to detect
The sequence number for the signal light light pulse arrived and the sequence number of signal light light pulse of transmitting terminal are consistent.
After completing synchronous amendment, transmitting terminal carries out sequence number to each synchronizable optical light pulse.According to each signal light
Each signal light light pulse is numbered in light pulse and the synchronizable optical optical pulse time interval of its affiliated frame.Transmitting terminal is to two
It is first frame and the second frame that synchronizable optical light pulse is numbered respectively.It is and same for second signal light light pulse a in first frame
Step light light pulse a time interval is Ta, for the 4th signal light light pulse b in the second frame, when with synchronizable optical light pulse b
Between between be divided into Tb.Signal light light pulse a is numbered according to the synchronizable optical light pulse a of frame where it and determined its institute in receiving end
Belong to first frame, measures it and can determine it for second light pulse in first frame with synchronizable optical light pulse a time interval Ta.For letter
Number light light pulse b numbers according to the synchronizable optical light pulse b of frame where it and determines its affiliated second frame, measures itself and synchronizable optical light
Pulse b time interval Tb can determine it for the 4th light pulse in the second frame.In this way, guarantee the signal light light pulse that detects with
The signal light light pulse of transmitting terminal corresponds, and is not in dislocation, achievees the purpose that time synchronization.Time synchronization can ensure
Transmitting terminal and receiving end carry out being the photon state for the same photon when basic vector comparison, and guarantee system can normally generate safety
Quantum key.
Shown in Fig. 2 to 6, Fig. 2 is shown as in the present invention structural schematic diagram of the clock synchronization system in quantum secret communication.
Fig. 3 is shown as the light pulse schematic diagram of transmitting terminal synchronizable optical and signal light when quantum secret communication in the present invention is synchronous to be corrected.Fig. 4
It is shown as the light pulse schematic diagram of receiving end synchronizable optical and signal light when quantum secret communication in the present invention is synchronous to be corrected.Fig. 5 is aobvious
It is shown as the light pulse schematic diagram of transmitting terminal synchronizable optical and signal light when quantum secret communication time synchronization in the present invention.Fig. 6 is shown
For in the present invention when quantum secret communication time synchronization receiving end synchronizable optical and signal light light pulse schematic diagram.The present invention also mentions
Supply the clock synchronization system in a kind of quantum secret communication, comprising:
Synchronous light emitting devices carries out frame number for being emitted synchronizable optical, and to synchronizable optical；Signal light emitting end, is used for
Output signal light, and according to the time interval of signal light light pulse and the synchronizable optical light pulse of its affiliated frame to each signal light light
Pulse carries out label；When initial outgoing, signal light and synchronizable optical are basic mode mode, and after outgoing, synchronizable optical switchs to higher order mode,
In one embodiment of this invention, signal light emitting end further includes polarization state preparation and attenuation module, for carrying out signal light
Polarization state preparation and decaying, prepare the other tetra- road polarised light of H, V, P, N of single-photon-level.In another embodiment of the invention,
Synchronous light emitting devices includes: synchronous optical transmitting set, for being emitted synchronizable optical；Optical attenuator, synchronizable optical for that will be emitted into
Row decaying；Mode converter, for the mode of the synchronizable optical after decaying to be converted to higher order mode by basic mode.Of the invention another
In one embodiment, signal light emitting end be also used to determine send when signal light light pulse relative to synchronizable optical light pulse first when
Between be spaced.
Pattern multiplexer, for by signal light with after synchronous optical coupling by same root less fundamental mode optical fibre transmission；Transmission
Channel is less fundamental mode optical fibre, and less fundamental mode optical fibre can realize multiplexing by increasing the mode for the light beam propagated in single-core fiber, mention
It is unobvious to the increase in demand of energy consumption under the premise of high-transmission capacity.Compared with traditional single mode optical fiber, the mould field of less fundamental mode optical fibre
Diameter is bigger, can support more transmission modes, and decaying will not significantly increase.Compared with multimode fibre, less fundamental mode optical fibre is passed
Defeated loss is smaller, and transmission range is farther, the easily controllable coupling between reduction mode.
Pattern demultiplexer, for receiving the signal light after coupling and synchronizable optical and being divided signal light and synchronizable optical
Beam.
PIN detector identifies the frame number of synchronizable optical for detecting synchronizable optical.
Single-photon detector for detecting the signal light, and measures the signal light light pulse apart from its affiliated frame
The time interval of the synchronizable optical light pulse；And the mark of the signal light light pulse received according to time interval judgement
Number；The label of the signal light light pulse received and the label of the signal light light pulse of transmission are corresponded.
Correction module, for determining that the link transmission between the signal light light pulse and the synchronizable optical light pulse is prolonged
When, amendment is synchronized to the signal light.
In the starting of QKD equipment, equipment Alignment work will do it, wherein just containing synchronous amendment step.Synchronous amendment
Step is exactly
The time location that each signal light light pulse is accurately positioned lays the foundation.
In one embodiment of this invention, the single-photon detector is also used to determine signal light light pulse when reception
The second time interval relative to the synchronizable optical light pulse；The correction module is also used to according to the first time interval
Difference between second time interval determines the link between the signal light light pulse and the synchronizable optical light pulse
Transmission delay.After completing synchronous amendment, it is more much smaller than signal light frequency to synchronize light frequency for sending cycle synchronizable optical and signal light.
Each synchronizable optical light pulse forms a frame light pulse signal followed by a string of signal light light pulses.Sequence is carried out to each synchronizable optical
Column number, and measure the time interval of synchronizable optical light pulse of some signal light light pulse apart from frame where it, that is, it can determine this
Which frame signal light light pulse belongs to, and which is a, and the deadline is synchronous.
It is illustrated below with one embodiment of the invention, transmitting terminal goes out the signal light that emission mode is basic mode, by signal light
Polarization state preparation and attenuation module, prepare the other tetra- road polarised light of H, V, P, N of required single-photon-level.Synchronizable optical and signal light
Identical, the emission mode that goes out of synchronizable optical is basic mode.Synchronizable optical first passes through optical attenuator and carries out light intensity attenuation, then passes through mode
Converter is converted into LP11 mode or other higher order modes.Basic mode quantum signal light and high-order mode synchronizable optical pass through pattern multiplexer
Same root less fundamental mode optical fibre channel is coupled into be transmitted.In general, the link between signal light emitting end and pattern multiplexer can
Using single mode optical fiber or less fundamental mode optical fibre, the link between mode converter and pattern multiplexer uses less fundamental mode optical fibre.It is receiving
End, signal light and synchronizable optical are split by pattern demultiplexer, and the single-photon detector of signal light receiving end receives, together
It walks light and reception is detected by PIN detector.In general, single-mode optics can be used in the link between pattern demultiplexer and single-photon detector
Fine or less fundamental mode optical fibre, the link between pattern demultiplexer and PIN detector use less fundamental mode optical fibre.
As shown in Figures 3 to 6, for QKD equipment before operating normally work, system will do it initialization of calibration.It completes
After light intensity feedback, delayed sweep, polarization feedback, amendment step can be synchronized one by one for tetra- road signal light of H, V, P, N.With
For the signal light of the road H, synchronous light laser issues the recurrent pulse light that repetition rate is 100kHz, the road H signal light laser
The periodic pulse signal light that repetition rate is 100kHz is issued, synchronizable optical is identical with the wavelength of signal light.In transmitting terminal, signal light
Light pulse is fixed relative to synchronizable optical optical pulse time interval, is denoted as T1.
After optical fiber link and electronics circuit, synchronizable optical light pulse and signal light the light pulse delay detected is deposited
In difference.The time interval T2 of synchronizable optical light pulse and signal light light pulse is determined after repeatedly detecting statistics.Because of link
Postpone different, compared to the time interval T1 of synchronizable optical light pulse and signal light light pulse in transmitting terminal, is introduced in receiving end
Time interval difference DELTA T.Because determining that signal light light pulse sequence number is to rely on to measure itself and affiliated frame in receiving end
The time interval of synchronizable optical light pulse is completed.For some light pulse of transmitting terminal, with synchronizable optical optical pulse time interval
For T1, and in receiving end, the signal light light pulse and synchronizable optical optical pulse time interval detected becomes T2, T1 and T2 phase
Poor Δ T.Therefore when actually determining signal light light pulse position, need to deduct Δ T.Modified purpose is synchronized exactly for receiving end
The time interval " recovery " of signal light light pulse and synchronizable optical light pulse is at the time interval in transmitting terminal, to guarantee to detect
The sequence number for the signal light light pulse arrived and the sequence number of signal light light pulse of transmitting terminal are consistent.
After completing synchronous amendment, transmitting terminal carries out sequence number to each synchronizable optical light pulse.According to each signal light
Each signal light light pulse is numbered in light pulse and the synchronizable optical optical pulse time interval of its affiliated frame.Transmitting terminal is to two
It is first frame and the second frame that synchronizable optical light pulse is numbered respectively.It is and same for second signal light light pulse a in first frame
Step light light pulse a time interval is Ta, for the 4th signal light light pulse b in the second frame, when with synchronizable optical light pulse b
Between between be divided into Tb.Signal light light pulse a is numbered according to the synchronizable optical light pulse a of frame where it and determined its institute in receiving end
Belong to first frame, measures it and can determine it for second light pulse in first frame with synchronizable optical light pulse a time interval Ta.For letter
Number light light pulse b numbers according to the synchronizable optical light pulse b of frame where it and determines its affiliated second frame, measures itself and synchronizable optical light
Pulse b time interval Tb can determine it for the 4th light pulse in the second frame.In this way, guarantee the signal light light pulse that detects with
The signal light light pulse of transmitting terminal corresponds, and is not in dislocation, achievees the purpose that time synchronization.Time synchronization can ensure
Transmitting terminal and receiving end carry out being the photon state for the same photon when basic vector comparison, and guarantee system can normally generate safety
Quantum key.
In conclusion method for synchronizing time and system in quantum secret communication of the invention, without increasing additional light
Fine channel, by mode division multiplexing device by quantum signal light with synchronize be optically coupled into same root fibre channel transmission, this measure is very big
Ground saves fiber resource.Moreover, synchronizable optical is not take up wavelength channel for multichannel QKD wavelength-division multiplex system, it is equivalent to reduction
The wavelength-division multiplex Insertion Loss of the road Liao Mei quantum signal light improves every road QKD service feature, including at code rate, transmission range etc., in group
When building extensive quantum secret communication network, there is objective economic benefit.So the present invention effectively overcomes in the prior art
Various shortcoming and have high industrial utilization value.
The above-described embodiments merely illustrate the principles and effects of the present invention, and is not intended to limit the present invention.It is any ripe
The personage for knowing this technology all without departing from the spirit and scope of the present invention, carries out modifications and changes to above-described embodiment.Cause
This, institute is complete without departing from the spirit and technical ideas disclosed in the present invention by those of ordinary skill in the art such as
At all equivalent modifications or change, should be covered by the claims of the present invention.
Claims (8)
1. the method for synchronizing time in a kind of quantum secret communication, which is characterized in that comprising steps of
S1, output signal light and synchronizable optical；
S2, by the signal light with after the synchronous optical coupling by same root less fundamental mode optical fibre transmission；
S3, the signal light after coupling and the synchronizable optical are received and is split the signal light and the synchronizable optical；
S4, the signal light and the synchronizable optical are detected, determined between the signal light light pulse and the synchronizable optical light pulse
Link transmission delay, amendment is synchronized to the signal light；
S5, frame number is carried out to the synchronizable optical, and described synchronous with its affiliated frame according to each signal light light pulse
Light optical pulse time interval carries out label to each signal light light pulse；
The frame number of S6, the identification synchronizable optical, measure the synchronization of the signal light light pulse apart from its affiliated frame
The time interval of light light pulse；And the label of the signal light light pulse received according to time interval judgement；It will connect
The label of the signal light light pulse of the label and transmission of the signal light light pulse received corresponds.
2. the method for synchronizing time in quantum secret communication according to claim 1, which is characterized in that the step S1 is also
Include:
After the signal light is carried out polarization state preparation and decayed, the other tetra- road polarised light of H, V, P, N of single-photon-level is prepared.
3. the method for synchronizing time in quantum secret communication according to claim 1, which is characterized in that the step S1 is also
Include:
The synchronizable optical of outgoing is decayed；The mode of the synchronizable optical after decaying is converted into high-order mode by basic mode
Formula.
4. the method for synchronizing time into quantum secret communication described in 3 any one according to claim 1, which is characterized in that
The step S1 further include: determine when sending between first time of the signal light light pulse relative to the synchronizable optical light pulse
Every；
The step S4 further include:
Determine second time interval of the signal light light pulse relative to synchronizable optical light pulse when receiving；
The signal light light pulse and institute are determined according to the difference between the first time interval and second time interval
State the link transmission delay between synchronizable optical light pulse.
5. the clock synchronization system in a kind of quantum secret communication characterized by comprising
Synchronous light emitting devices carries out frame number for being emitted synchronizable optical, and to the synchronizable optical；
Signal light emitting end is used for output signal light, and according to the synchronizable optical light arteries and veins of the signal light light pulse and its affiliated frame
The time interval of punching carries out label to each signal light light pulse；
Pattern multiplexer, for by the signal light with after the synchronous optical coupling by same root less fundamental mode optical fibre transmission；
Pattern demultiplexer, for receiving the signal light after coupling and the synchronizable optical and by the signal light and described same
Step light is split；
PIN detector identifies the frame number of the synchronizable optical for detecting the synchronizable optical；
Single-photon detector for detecting the signal light, and measures the signal light light pulse apart from described in its affiliated frame
The time interval of synchronizable optical light pulse；And the label of the signal light light pulse received according to time interval judgement；
The label of the signal light light pulse received and the label of the signal light light pulse of transmission are corresponded；
Correction module is right for determining that the link transmission between the signal light light pulse and the synchronizable optical light pulse is delayed
The signal light synchronizes amendment.
6. the clock synchronization system in quantum secret communication according to claim 5, which is characterized in that the signal light hair
Penetrating end further includes polarization state preparation and attenuation module, for preparing list for signal light progress polarization state preparation and decaying
The tetra- road polarised light of H, V, P, N of photon level.
7. the clock synchronization system in quantum secret communication according to claim 5, which is characterized in that the synchronizable optical hair
Injection device includes:
Synchronous optical transmitting set, for being emitted synchronizable optical；
Optical attenuator, for the synchronizable optical of outgoing to decay；
Mode converter, for the mode of the synchronizable optical after decaying to be converted to higher order mode by basic mode.
8. according to the clock synchronization system in quantum secret communication described in claim 5 to 7 any one, which is characterized in that
The signal light light pulse that the signal light emitting end is also used to determine when sending relative to the synchronizable optical light pulse first
Time interval；
The single-photon detector is also used to determine that the signal light light pulse is relative to the synchronizable optical light pulse when reception
Second time interval；
The correction module is also used to determine institute according to the difference between the first time interval and second time interval
State the link transmission delay between signal light light pulse and the synchronizable optical light pulse.
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