CN209517161U - A kind of coalescing network system of quantum communications and the transmission of quantum time-frequency - Google Patents
A kind of coalescing network system of quantum communications and the transmission of quantum time-frequency Download PDFInfo
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- CN209517161U CN209517161U CN201822278497.XU CN201822278497U CN209517161U CN 209517161 U CN209517161 U CN 209517161U CN 201822278497 U CN201822278497 U CN 201822278497U CN 209517161 U CN209517161 U CN 209517161U
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Abstract
The utility model discloses the coalescing network systems of a kind of quantum communications and the transmission of quantum time-frequency, Quantum repeater unit emits entangled photon pairs, two quantum terminal units are respectively sent to through transmission unit, quantum terminal unit reflection input photon simultaneously returns to quantum relay unit via transmission unit.Quantum repeater unit carries out HOM interferometry to entangled photon pairs, and adjusts optical path time delay, is repeatedly measured to obtain HOM recess maximum value, realizes optical-circuit balance.Subsequent signal laser sends laser pulse and is sent to quantum terminal unit through transmission unit, quantum terminal unit encodes input optical pulse and sends back Quantum repeater unit via transmission channel, after Quantum repeater unit obtains a result and passes through classical channel announcement acquisition key, it is synchronous that clock is carried out by classical channel and using optical channel monitor, the key that Time-Frequency Information is distributed by QKD encrypts, and solves the information security issue of Time-Frequency Information and realize quantum communications to merge with what quantum time-frequency transmitted.
Description
Technical field
Originally practical to be related to quantum information and technical field of photo communication, in particular to it is kept pouring in when a kind of quantum communications are with quantum
Defeated coalescing network system.
Background technique
Temporal frequency is a critically important parameter；Time and frequency standard is delivered in high-accuracy time dissemination system also to Guan Chong
It wants, is all widely used in numerous areas such as positioning, navigation, communications.Time and Frequency Synchronization technology refers to through certain means, will locate
The time frequency signal that clock in strange land generates is compared, and forms the process of unified time and frequency standards.Precise navigation be unable to do without standard
True time service service, and the basic demand of time service service is that clock is synchronous.
With the continuous development of atomic clock technology, the frequency uncertainty of optical frequency atomic clock reaches 10-18.Existing time-frequency
Simultaneous techniques can no longer meet the demand of high precision clock comparison, need to the Time and Frequency Synchronization that development has more high-transmission stability
Method.The Fibre Optical Communication Technology of rapid development is relied on, the Time and Frequency Synchronization technology based on optical fiber is come into being.Optical fiber is as a kind of big
The transmission medium of bandwidth, high-speed has become at present the most huge communications infrastructure in the world.China is newly-built within 2017
7,050,000 kilometers of lightguide cable link length, national lightguide cable link total length is up to 37,470,000 kilometers., isolation low using fiber transmission attenuation
The advantages such as electrical noise, widely distributed, time-frequency network of the construction based on optical fiber have reality and important meaning.
Quantum communications are considered as the developing direction of future communications, wherein quantum key distribution (Quantum Key
Distribution, QKD allow the password being perfectly safe in Sharing Theory between the end legitimate user Alice and the end Bob, in conjunction with one
Secondary one close encryption system realizes evincible unique secure communication at present.By the development in more than 30 years, QKD is at present
Measuring device independent protocol (MDI, the Measurement Device Independent) stage is entered, in conjunction with trick state skill
Art, MDI-QKD disposably close the defect of detector and solve the multi-photon content problem of weak coherent state single-photon source, at
For the most scheme of practical prospect at present, the network integration of quantum communications and the transmission of quantum time-frequency is current urgent need to resolve
Accurate time service, the important exploration of time service safety-critical technical problem.
But the quantum state that the end Alice and the end Bob issue in measuring device independent protocol third party Charlie measure at
Function, it is desirable that reach time of photon, frequency spectrum, polarization isotype must exactly match.Firstly, the end Alice and the end Bob with
The distance between Charlie be not it is completely the same, need accurately to be delayed so that photon arrival time is aligned completely.Secondly,
The end Alice and the end Bob use different lasers, and frequency spectrum is not identical.Third, because of the birefringence effect of optical fiber, very
Be difficult to guarantee photon polarization state stablizes transmission.Although phase code can be used, phase drift, time jitter are limited
The raising of QKD system performance, secret-key rate are lower.
Meanwhile in the prior art, the measurement as patent 201510008068.9 attempts to solve phase-modulated polarized coding is set
Standby independent protocol stability problem, but communication distance is artificially shortened into half.
In the prior art, as earliest propose plug and play scheme Gisin group, University of Geneva (document:
Muller A,Herzog T,Huttner B,etal."plug and play"systems for quantum
Cryptography [J] .Applied physics Letters, 1997,70:793-795) by the way of phase code,
Patent 201610700278.9 is further improved, and uses time phase coding mode, and main purpose is to solve to polarize in optical fiber
The problem of jitter compensation, but it is not directed to the unrelated scheme of measuring device.
Plug and play scheme can use the consistency that same laser realizes the parameters such as photon frequency spectrum, but due to communication
Both sides be not at a distance from relaying it is full symmetric, cause HOM interference to compare decline.Different wave length is generally used in experiment at present
Independent light pulse the synchronization of communicating pair is realized using wavelength-division multiplex, consume wavelength resource.However as the network user
Increase, especially in classical and quantum communications converged network, each wavelength is valuable resource, and the above method is obviously not
Economy is also infeasible.
MDI-QKD is higher for clock synchronization requirement, and the safety of time-frequency transmission is not possible to ensure completely at present, in conjunction with
Advantage and time-frequency the transmission synchronization accuracy of QKD information security are high a little, the network of fusion quantum communications and the transmission of quantum time-frequency
It temporarily there are no relevant programme proposition.
Utility model content
The utility model is made in view of the above problems, it is therefore an objective to overcome the deficiencies of the prior art and provide a kind of quantum
The coalescing network system of communication and the transmission of quantum time-frequency solves the clock synchronization issue and time-frequency net of MDI-QKD in practical application
The information security issue of network.
To achieve the above object, the utility model provides the following technical solutions: a kind of quantum communications and quantum time-frequency transmit
Coalescing network system, including quantum terminal unit, Quantum repeater unit and transmission unit, the quantum terminal unit include
The end Alice and the end Bob；
The Quantum repeater unit includes that the end Alice and the end Bob are mutual with the quantum terminal unit by transmission unit
Connection；
The end quantum terminal unit Alice and the end Bob respectively include four port circulators, the 4th polarization beam apparatus, method
Draw eyeglass, the second beam splitter, optical channel monitor, optoisolator, phase-modulator, light polarization modulator, intensity modulator, can
Controlled attenuator and clock, four port circulator pass through all the way optical fiber successively with the second beam splitter, optoisolator, phase-modulation
Device, light polarization modulator, intensity modulator are connected with adjustable attenuator ending, and the 4th polarization beam apparatus is connected with light in turn again
Channel monitor and clock；Another way is sequentially connected the 4th polarization beam apparatus and faraday's eyeglass；
The Quantum repeater unit includes measuring instrument, quantum entanglement light source and quantum communications light source；
The quantum entanglement light source is for generating signal photon and idler photon entangled photon pairs；The quantum communications light source
For generating communication pulse laser；The measuring instrument measures the signal photon and idler photon of entangled photon pairs while right
The communication pulse laser of input carries out Bell state measurement；
Transmission unit is used for transmission laser pulse while the Quantum repeater unit and the end quantum terminal unit Alice is arranged
Time delay between the end Bob.
Quantum repeater unit emits entangled photon pairs pulse, and wherein signal photon reaches quantum terminal unit through transmission unit
Alice, idler photon reach quantum terminal unit Bob through transmission unit.Alice and Bob reflect signal photon and ideler frequency respectively
Photon returns to quantum relay unit through former link, and it is dry that Quantum repeater unit is HOM to the signal photon and idler photon that are reflected back
It relates to, obtains interference pattern.Transmission unit repeatedly reconciles the time delay between two optical paths, and Step wise approximation obtains the maximum of HOM recess
Value, thinks that the light path of two optical paths is completely the same at this time, and the time that Alice and Bob reaches Charlie is essentially equal.Alice and
Bob carries out clock using Optical Supervisory Channel and synchronizes.
Quantum key distribution is carried out below:
Quantum repeater unit emits two-way light pulse, and light pulse described in two-way is sent to quantum terminal unit through transmission unit
Alice and Bob, and encoded and reflected in the quantum terminal unit, return to the amount through transmission unit again after reflection
Sub- relay unit.
The Quantum repeater unit Charlie is analyzed by the laser pulse after quantum terminal unit coding, is obtained
Measurement result, and measurement result is announced by classical channel, classical channel here is common signal channel, such as is broadcasted.
The multiple quantum terminal unit measurement of comparison result and the local information for preparing quantum state obtain screening code, and
Bit error rate detection is carried out to the screening code, if it is considered to safety, then communicate success, if it is considered to it is dangerous, it is logical to abandon this
Letter, restarts.
The Quantum repeater unit is connect with transmission unit by fiber channel；
The quantum terminal unit is connect with transmission unit by fiber channel；
The quantum terminal unit is connect with Quantum repeater unit by transmission unit.
Preferably, the quantum entanglement light source includes pump laser, nonlinear crystal, the first narrow band filter, second
Narrow band filter.The pumping pulse laser of the pump laser transmitting 790nm, incident nonlinear crystal generate similar in frequency
Entangled photon pairs enter transmission unit through the first narrow band filter, the second narrow band filter respectively.
Preferably, the transmission unit receives quantum relay unit and generates entangled photon pairs, and wherein signal photon is through first
After bundling device enters first annular device, enters the first optical fiber link through automatically controlled optical delay line and be sent to the quantum terminal unit
Alice, idler photon enter the second circulator by the second bundling device, enter the second optical fiber link through manual variable optical delay line
It is sent to the quantum terminal unit Bob, two quantum terminal units are by the pulse-echo, and the pulse of reflection is through excess
After subchannel transmission, respectively through first annular device, the second circulator, transmit in the Quantum repeater unit；
Preferably, the quantum communications light source includes laser and polarization beam apparatus, and laser emits 1550nm wave band
Pulse laser, after polarization beam apparatus, horizontal polarization light enters transmission unit；
Preferably, the transmission unit receives the communication laser pulse of quantum relay unit, is divided into two by the first beam splitter
Road, wherein entering the first optical fiber link through automatically controlled optical delay line after pulse enters first annular device by the first bundling device all the way
It is sent to the quantum terminal unit Alice, another way pulse enters the second circulator by the second bundling device, through adjustable manually
Optical delay line enters the second optical fiber link and is sent to the quantum terminal unit Bob, quantum the terminal unit Alice and Bob
By the pulse-echo, the pulse of reflection is after quantum channel transmits, respectively through the first annular device, the second annular
Device transmits in the Quantum repeater unit；
The Quantum repeater unit includes measuring instrument, and the pulse that the measuring instrument is passed to transmission unit carries out projection survey
Amount obtains and measures determining quantum state, and the quantum terminal unit prepares quantum state by the quantum state for measuring determination and locally
Information comparison obtains screening code, and by the classical channel communication of certification, a part of estimating bit error rate in code, and root are screened in selection
According to the mode computation theoretical value for inveigling state, if the bit error rate is lower than theoretical value, then it is assumed that safety continues subsequent processing, if accidentally
Code rate is higher than theoretical value, then it is assumed that there are security risk, abandons this communication.
Preferably, the signal photon and idler photon that the measuring instrument is used to be passed to transmission unit carry out HOM interference and survey
Amount obtains delay time and interference to the relationship compared.
Specifically, first annular device and the second circulator are for being isolated emergent light and reflected light.
Preferably, the quantum terminal unit includes four port circulators, the 4th polarization beam apparatus, faraday's eyeglass, the
Two beam splitters, optical channel monitor, optoisolator, phase random device, intensity modulator, light polarization modulator and variable optical attenuation
Device；
After the pulse enters quantum terminal unit, four port circulators are introduced into, the 4th polarization beam splitting is then passed to
Device, later by faraday's lens reflecting, return to four port circulators and enter the second beam splitter, be divided into two-way, enter light all the way and supervise
Device is controlled, sequentially enters optoisolator, phase random device, light polarization modulator, intensity modulator and variable optical attenuator all the way.
Specifically, four port circulator is used to adjust the walking path of photon.
Faraday's eyeglass for compensating the polarization shake in transmission process automatically.
Second beam splitter is the beam splitter of 10:90, and transmitted light is used for quantum key distribution, and reflected light is supervised for channel
Control device.
Light monitor is for the optical power levels in monitoring and controlling channels, for adjusting variable optical attenuator to guarantee average photon
Number is designated value；After the completion of optical path adjusting, light monitor is used for time synchronization.
The optoisolator is used to guarantee the one-way transmission of light, and emergent light and reflected light is isolated.
The phase of the phase random device Stochastic Modulation light pulse is between [0,2 π], to meet wanting for Number State
It asks.
Light pulse can be modulated into level at random by the light polarization modulator, vertically ,+45 degree and -45 degree polarization states.
The intensity modulator is signal state or trick state for regulating and controlling light pulse.Variable optical attenuator guarantees the amount of being reflected into
The average pulse number of photons of subchannel is less than 1.
Preferably, the measuring instrument includes third beam splitter, the first polarization beam apparatus, the second polarization beam apparatus, the first list
Photon detector, the second single-photon detector, third single-photon detector, the 4th single-photon detector and coincidence counting device；
Pulse through faraday's lens reflecting, successively by the second beam splitter, optoisolator, phase random device, partially
Shake modulator, intensity modulator, and into adjustable attenuator, the pulse through overdamping is synchronized to be sent to measuring instrument.
The third beam splitter receives the entangled photon pairs from transmission unit, and the quantum being formed on third beam splitter is dry
It relates to, by the evolution of the first polarization beam apparatus, the second polarization beam apparatus, into the first single-photon detector, the second single-photon detecting
It surveys device, third single-photon detector and the 4th single-photon detector and generates response；Coincidence counting device is to photon counting and accords with
Measurement is closed, HOM interference pattern is obtained.
Specifically, the third beam splitter is the beam splitter of 50:50.
First polarization beam apparatus, the second polarization beam apparatus transmission level polarised light reflect orthogonal polarized light.
First single-photon detector, the second single-photon detector, third single-photon detector, the 4th single-photon detector are
Threshold detector, for having detected whether photon arrival.
The coincidence counting device judges measurement result according to the response of single-photon detector.
The coalescing network system and method transmitted according to above-mentioned quantum communications with quantum time-frequency include:
The laser that Quantum repeater unit is included sends laser pulse, and it is identical to be divided into two-way intensity through the first beam splitter
Light pulse.
Two light pulses are connected to quantum channel after passing through first annular device and the second circulator respectively.
Quantum channel gives light pulses to quantum terminal unit.
Normalization factor is not considered, at this point, the quantum state of photon are as follows:
| ψ >=| H >+| V >.
Wherein, H indicates that horizontal polarization light, V indicate orthogonal polarized light.
4th polarization beam apparatus transmits the horizontal polarisation component in input pulse as photon to be modulated, and quantum state becomes:
| ψ >=| H >.
Orthogonal polarized light is converted to by faraday's lens reflecting, then after reflected light is isolated in optoisolator, by phase
Position modulator Stochastic Modulation photon phase [0,2 π], makes it meet the condition of Number State (Fock state).
Light polarization modulator Stochastic Modulation is one of horizontal, vertical ,+45 degree, -45 four polarization states of degree, and quantum state becomes:
| ψ >=| H >, | V >, |+>, | ->.
It is signal state or trick state that intensity modulator, which is randomly provided pulse, and adjustable attenuator is according to Line Attenuation and input light
Average photon number is set designated value by power, and if signal photon is 0.4/pulse, trick state photon is 0.05/pulse.
Assuming that two quantum states of input quantum terminal unit Alice and Bob are equal are as follows:
| ψ >=| H >.
The joint quantum state then exported from adjustable optical attenuator are as follows:
Photon is by the sub- relay unit of quantum channel back amount, and reaching measuring instrument, (measuring instrument is analyzed using Bell state
Instrument) when, combine evolution of quantum state are as follows:
Wherein:
φi, i=a, b are the phases of phase-modulator Stochastic Modulation；
μ, ν are respectively the average photon number of two quantum terminal units output；
ηi, i=a, b are total losses caused by optical device in optical path and fiber channel.
Measuring instrument measures input quantum state.
When:
First single-photon detector, the 4th single-photon detector；
Second single-photon detector, third single-photon detector；
Any group respond expression quantum state simultaneously are as follows:
When:
First single-photon detector, the second single-photon detector；
Third single-photon detector, the 4th single-photon detector；
Any group respond expression quantum state simultaneously are as follows:
Both the above situation thinks to measure successfully.Quantum repeater unit Charlie announces measurement result by common signal channel.
Communicating pair Alice and Bob according to Charlie announce as a result, comparison local information after, to local quantum state table
The bit information shown does not do operation or does bit reversal operation, and MDI-QKD (using explanation in Chinese) completes key distribution, concrete mode
As shown in the table.
If should be noted that, using+45 ° of diagonal base and -45 ° of polarization states, theory shows the error code of diagonal base
Rate is greater than straight line base, therefore diagonal base can be used for estimated bit error, but is not used in generation key.
Similarly, the case where light polarization modulator is modulated when two quantum terminal units are other quantum states can be analyzed.
According to mentioned above principle, two quantum terminal units obtain just key, carry out bit error rate estimation, if verification passes through,
Two quantum terminal units obtain final key by secrecy error correction and enhancing.
The beneficial effects of the utility model are:
1. the utility model carries out quantum communications and the transmission of quantum time-frequency using same physical network simultaneously, physics has been saved
Fiber resource the utility model is compensated automatically using faraday's eyeglass, and design is returned toward optical path elimination because two-fold caused by optical fiber link
Problem is penetrated, device is simple, low in cost.
2. the laser light source of the utility model is to have good stability and consistency using single laser and drop
Low cost；The utility model method unrelated using measuring device, can eliminate detector side channel bring QKD safety
Problem.
3. the utility model is improved using the synchronous optical-circuit balance realizing measuring device independent protocol and requiring of quantum clock
Synchronization accuracy, the key pair quantum time-frequency transmission information encryption that the utility model is generated using QKD, ensure that the peace of Time-Frequency Information
Quan Xing.
Detailed description of the invention
Fig. 1 is the structural block diagram of the MDI-QKD quantum terminal unit of the utility model；
Fig. 2 is the structural block diagram of the measuring instrument of the utility model；
Fig. 3 is the structural block diagram of the quantum entanglement light source of the utility model；
Fig. 4 is the structural block diagram of the quantum communications light source of the utility model；
Fig. 5 is the transmission unit structural block diagram of the utility model；
Fig. 6 is the working principle overall structure block diagram of Tthe utility model system.
The corresponding component names of each label are as follows in attached drawing:
Quantum terminal unit 1, four port circulators 101, the 4th polarization beam apparatus 102, faraday's eyeglass 103, second point
Beam device 104, optical channel monitor 105, optoisolator 106, phase-modulator 107, light polarization modulator 108, intensity modulator
109, adjustable attenuator 110, clock 111；
Measuring instrument 2, third beam splitter 201, the first polarization beam apparatus 202, the second polarization beam apparatus 203, the first single photon
Detector 211, the second single-photon detector 212, third single-photon detector 213, the 4th single-photon detector 214 meet meter
Number device 221；
Quantum entanglement light source 3, pump laser 301, nonlinear crystal 302, the first narrow band filter 303, the second narrowband
Filter 304；
Quantum communications light source 4, telecommunication laser 401, third polarization beam apparatus 402；
Transmission unit 5, the first beam splitter 501, the first bundling device 511, the second wave bundling device 512, first annular device 521,
Second circulator 522,531, manual adjustable optical delay line 532, the first optical fiber link 541, the second optical fiber link 542.
Specific embodiment
Specific embodiment of the present utility model is described further with reference to the accompanying drawing:
As shown in Figures 1 to 6, the coalescing network system of a kind of quantum communications and the transmission of quantum time-frequency is present embodiments provided,
Work step is as follows:
Pump laser (Ti:Sapphire laser Mode-locked laser device, Femto Lasers) 301 issues the laser pulse of 790nm,
It is incident on nonlinear crystal 302 (TypeII phase matched PPKTP), generates entangled photon pairs, wherein signal photon and ideler frequency light
Son respectively enters the first narrow band filter 303 and the second narrow band filter 304 filtering pump light and stray light, subsequently into transmission
Unit 5.Signal photon and idler photon are separately sent to by transmission unit 5 by the first bundling device 511 and the second bundling device 512
First annular device 521 and the second circulator 522, automatically controlled optical delay line 531 and the first optical fiber link 541, adjustable light delay manually
Line 532 and the second optical fiber link 542 are sent to quantum terminal unit Alice and Bob.
Signal photon and idler photon are respectively via circulator 101, the 4th polarization beam apparatus 102, by faraday's eyeglass 103
Quantum relay unit 6 is returned along original optical path after reflection.
The measuring instrument 2 of Quantum repeater unit 6 receives and measures the HOM effect of entangled photon pairs, specially signal photon and
Idler photon enters measuring instrument by the input port of third beam splitter 201 respectively, interference is generated on third beam splitter 201, respectively
Enter the first single-photon detector 211, the second single photon after being developed by the first polarization beam apparatus 202, the second polarization beam apparatus 203
Detector 212, third single photon detection 213, the 4th single-photon detector 214 are detected and are identified, finally by coincidence counting device 221
Carry out coincidence measurement.
Transmission unit 5 adjusts automatically controlled optical delay line, be arranged between quantum relay unit and two quantum terminal units when
Prolong, measuring instrument 2 measures again.Maximum value repeated multiple times, that gradually HOM is recessed after all.
When coincidence counting device obtains HOM recess maximum value, it is believed that two optical-circuit balances, photon reach two amounts simultaneously
Sub- terminal unit.Quantum key distribution is carried out in next step.
Signal laser (PDL808SepiaPicoquant) 401 issues the laser pulse of 1550nm, and the pulse passes through
After third polarization beam apparatus 402, transmission level polarised light enters transmission unit 5.Transmission unit 5 receives the pulse, by second
Beam splitter 501 divides for two-way, enters first annular device 521 through the first bundling device 511 all the way, through automatically controlled optical delay line 531 and the
One optical fiber link 541 is sent to quantum terminal unit Alice, and another way enters the second circulator 522, warp through the second bundling device 512
Manual variable optical delay line 532 and the second optical fiber link 542 are sent to quantum terminal unit Bob.
The end quantum terminal unit Alice and the end quantum terminal unit Bob, for receiving the letter of quantum relay unit 6
It feels the pulse punching.Four port circulators 101 are used to form photon walking path, and the 4th polarization beam apparatus 102 is used to form horizontal polarization
Light, faraday's eyeglass 103 are used for the polarization shake in compensated fiber link, the second beam splitter 104 for separate section photon
In monitoring, optical channel monitor 105 is for the optical power levels in monitoring and controlling channels, phase-modulator (Photline MPZ) 107
Random loading impulse phase [0,2 π] is used to meet the requirement of Number State, light polarization modulator (General PhotonicsMPC)
108 for being at random modulated to input photon:
| ψ >=| H >, | V >, |+>, | ->,
Pulse labeling is to inveigle state or signal state, adjustable attenuator 110 by intensity modulator (Photline MXAN) 109
Guarantee photon average is designated value, and optical channel monitor 105 is distributed according to the number of photons of Analysis of optical power pulse, faraday mirror
The polarization state of input light is rotated by 90 ° by piece 103, the birefringence effect in compensated optical fiber.Last quantum terminal unit is flat by output
For equal number of photons less than 1, Stochastic Modulation is the photon of horizontal, vertical ,+45 degree, -45 degree quantum states, part for labeled as
State is inveigled, signal state is partially labeled as.Above-mentioned photon returns to quantum relay unit 3 by quantum channel 4, synchronous to enter measuring instrument
2。
The Quantum repeater unit 3 receives two photons of the quantum terminal unit through ovennodulation, input measurement instrument 2.
The photon of 2 pairs of measuring instrument inputs is analyzed, and is below the quantum state point of two quantum terminal units output
Not are as follows:
I.e. photon is all modulated to horizontal polarization, two quantum ends of 107 Stochastic Modulation of phase-modulator by light polarization modulator 108
The phase of end unit 1 is respectively φa、φb, 110 collective effect of intensity modulator 109 and adjustable attenuator, so that two quantum ends
The average photon number of end unit 1 is respectively μ, ν.Joint quantum state are as follows:
Decay by fiber channel, combine evolution of quantum state are as follows:
ηa、ηbTotal losses caused by fiber channel and device respectively between two quantum terminal units 1 and tester 2.
After impulsive synchronization described in two-way enters the tester 2, third beam splitter, which is received, tangles light from transmission unit
Sub right, the quantum interference being formed on third beam splitter, by the evolution of the first polarization beam apparatus, the second polarization beam apparatus, into
Enter the first single-photon detector, the second single-photon detector, third single-photon detector and the 4th single-photon detector and generates sound
It answers；Coincidence counting device is to photon counting and carries out coincidence measurement.
Measuring instrument 2 to above-mentioned joint quantum measurement, when:
First single-photon detector 211, the 4th single-photon detector 214；
Second single-photon detector 212, third single-photon detector 213；
Any group respond expression quantum state simultaneously are as follows:
When:
First single-photon detector 211, the second single-photon detector 212；
Third single-photon detector 213, the 4th single-photon detector 214；
Any group respond expression quantum state simultaneously are as follows:
Both the above situation thinks to measure successfully.Quantum repeater unit 6 announces measurement result.
Two quantum terminal units 1 comparison measurement results and the local information for preparing quantum state respectively, can be obtained
Source code, then abandon those and measure unsuccessful data, obtain screening code.
For two quantum terminal units 1 respectively by the classical channel communication of certification, a part estimation in code is screened in selection
The bit error rate, and according to the mode (weak trick state+vacuum state, double trick states, single trick state) for inveigling state, computational theory value.If
The bit error rate is lower than theoretical value, then it is assumed that safety continues to post-process.If the bit error rate is higher than theoretical value, then it is assumed that it is hidden to there is safety
Suffer from, abandons this communication.
After error rate test passes through, two quantum terminal units 1 by the classical channel communication of certification, use respectively
Classical algorithm, preferably hash algorithm carry out error correction.
After error correction passes through, two quantum terminal units 1 respectively by the classical channel communication of certification, to the data of reservation into
Row secrecy enhancing, that is, abandon a part of data, so that the information that listener-in obtains is approximately 0, obtain safe quantum key.
Finally, the distribution of quantum key is realized between two quantum terminal units 1.
According to the disclosure and teachings of the above specification, the utility model those skilled in the art can also be to above-mentioned reality
The mode of applying is changed and is modified.Therefore, the utility model is not limited to specific embodiment disclosed and described above, right
Some modifications and changes of utility model should also be as falling into the protection scope of the claims of the present utility model.In addition, although
It is used some specific terms in this specification, these terms are merely for convenience of description, does not constitute to utility model
Any restrictions.
Claims (10)
1. the coalescing network system of a kind of quantum communications and the transmission of quantum time-frequency, it is characterised in that: including quantum terminal unit, amount
Sub- relay unit and transmission unit, the quantum terminal unit include the end Alice and the end Bob；
The Quantum repeater unit includes that the end Alice and the end Bob are connected with each other by transmission unit and the quantum terminal unit；
The end quantum terminal unit Alice and the end Bob respectively include four port circulators, the 4th polarization beam apparatus, faraday
Eyeglass, optical channel monitor, optoisolator, phase-modulator, light polarization modulator, intensity modulator, adjustable declines at the second beam splitter
Subtract device and clock, four port circulator pass through all the way optical fiber successively with the second beam splitter, optoisolator, phase-modulator,
Light polarization modulator, intensity modulator and adjustable attenuator join end to end；Another way be sequentially connected the 4th polarization beam apparatus and
Faraday's eyeglass；Second beam splitter is connected with optical channel monitor and clock in turn again；
The Quantum repeater unit includes measuring instrument, quantum entanglement light source and quantum communications light source；
The quantum entanglement light source is for generating signal photon and idler photon entangled photon pairs；The quantum communications light source is used for
Generate communication pulse laser；The measuring instrument measures while to input the signal photon and idler photon of entangled photon pairs
Communication pulse laser carry out Bell state measurement；
Transmission unit be used for transmission laser pulse and meanwhile be arranged the Quantum repeater unit and the end quantum terminal unit Alice and
Time delay between the end Bob.
2. the coalescing network system of quantum communications according to claim 1 and the transmission of quantum time-frequency, it is characterised in that: institute, institute
It states signal photon and is sent to quantum terminal unit Alice via transmission unit, idler photon is sent to quantum via transmission unit
Terminal unit Bob；
Quantum the terminal unit Alice and Bob reflect signal photon and idler photon respectively, by the transmission unit along former light
Road return measurement instrument；
The quantum communications light source sends pulse laser, into transmission unit after be divided into two-way, be sent to quantum terminal list all the way
First Alice is sent to quantum terminal unit Bob all the way；Quantum the terminal unit Alice and Bob respectively compile laser pulse
Code, by transmission unit along original optical path return measurement instrument.
3. the coalescing network system of quantum communications according to claim 2 and the transmission of quantum time-frequency, it is characterised in that: described
Measuring instrument includes third beam splitter, the first polarization beam apparatus, the second polarization beam apparatus, the first single-photon detector, the second monochromatic light
Sub- detector, third single-photon detector, the 4th single-photon detector and coincidence counting device；
The entangled photon pairs of the third beam splitter reception from transmission unit, the quantum interference being formed on third beam splitter,
By the evolution of the first polarization beam apparatus, the second polarization beam apparatus, into the first single-photon detector, the second single photon detection
Device, third single-photon detector and the 4th single-photon detector generate response；Coincidence counting device is to photon counting and meets
Measurement, obtains HOM interference pattern.
4. the coalescing network system of quantum communications according to claim 2 and the transmission of quantum time-frequency, it is characterised in that: described
Quantum entanglement light source includes pump laser, nonlinear crystal, the first narrow band filter and the second narrow band filter；
Pump laser emits pulse pump light, and pulse pump light is incident on nonlinear crystal, generates signal light similar in frequency
Son and idler photon entangled photon pairs, signal photon enter transmission unit through the first narrow band filter, and idler photon is narrow through second
Band filter enters transmission unit；
Wherein narrow band filter is for filtering pump light and stray light.
5. the coalescing network system of quantum communications according to claim 2 and the transmission of quantum time-frequency, it is characterised in that: described
Quantum communications light source includes pulse laser and third polarization beam apparatus；
The pulse laser sends the pulse laser of 1550nm communication wavelengths, through third polarization beam apparatus, transmission level polarization
Transmission unit is sent to after light；
Wherein third polarization beam apparatus transmission level polarised light reflects orthogonal polarized light.
6. the coalescing network system of quantum communications according to claim 1 and the transmission of quantum time-frequency, it is characterised in that: described
Transmission unit includes the first beam splitter, the first bundling device, the second bundling device, first annular device, the second circulator, the delay of automatically controlled light
Line, manually adjustable optical delay line, the first optical fiber link and the second optical fiber link；
First bundling device receives the signal photon from Quantum repeater unit, is delayed through first annular device into automatically controlled light
Line, the first optical fiber link are transmitted to the end quantum terminal unit Alice；
Second bundling device receives the idler photon from Quantum repeater unit, enters manual tunable optical through the second circulator and prolongs
When line, the second optical fiber link be transmitted to the end quantum terminal unit Bob；
First beam splitter receives the laser pulse of the 1550nm communication band from Quantum repeater unit, is divided into two-way, a routing
First bundling device, first annular device are transmitted to the end quantum terminal unit Alice through automatically controlled optical delay line, the first optical fiber link, separately
One the second bundling device of routing, the second circulator are transmitted to quantum terminal unit through manual tunable optical delay line, the second optical fiber link
The end Bob；
After the end quantum terminal unit Alice carries out information coding to laser pulse, further through first optical fiber link, electricity
Control optical delay line, first annular device are transmitted back to the Quantum repeater unit；
After the end quantum terminal unit Bob carries out information coding to laser pulse, further through second optical fiber link, manually
Adjustable optical delay line, the second circulator are transmitted back to the Quantum repeater unit.
7. the coalescing network system of quantum communications according to claim 1 and the transmission of quantum time-frequency, it is characterised in that: described
The quantum end terminal unit Alice or the end Bob receive the laser pulse from Quantum repeater unit by transmission, by four ports
Circulator enters the 4th polarization beam apparatus, then compensates to polarize caused by environment as faraday's eyeglass and drift about, and is reflected into four ends
Mouth circulator reaches the second beam splitter, is divided into two-way in the second beam splitter: wherein entering optical channel monitor all the way for monitoring
The optical power of input；Another way enters optoisolator isolation reflected light, subsequently enters phase random device, Stochastic Modulation light pulse
Phase is the requirement of [0,2 π] to meet Number State, is then horizontal (H) by light polarization modulator Stochastic Modulation photon, vertical
(V) ,+45 degree, -45 degree polarization states are loaded as inveigling state or signal state using intensity modulator, finally pass through variable optical attenuation
Device forms weak coherent laser pulse signal of the average photon number less than 1.
8. the coalescing network system of quantum communications according to claim 7 and the transmission of quantum time-frequency, it is characterised in that: described
Four port circulators are used to adjust the walking path of photon；Faraday's eyeglass for compensating the polarization in transmission process automatically
Shake.
9. the coalescing network system of quantum communications according to claim 7 and the transmission of quantum time-frequency, it is characterised in that: described
Second beam splitter is the beam splitter of 10:90, and beam splitting forms transmitted light and reflected light, and the transmitted light is used for quantum key distribution,
Reflected light is used for channel monitoring；
The optical channel monitor guarantees average for the optical power levels in monitoring and controlling channels for adjusting variable optical attenuator
Number of photons is designated value.
10. the coalescing network system of quantum communications according to claim 7 and the transmission of quantum time-frequency, it is characterised in that: institute
It is synchronous for clock to state optical channel monitor；The optoisolator is used to guarantee the one-way transmission of light, and emergent light and reflection is isolated
Light.
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