CN208849779U - A kind of phase decoding device and quantum key distribution system - Google Patents
A kind of phase decoding device and quantum key distribution system Download PDFInfo
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- CN208849779U CN208849779U CN201821752688.9U CN201821752688U CN208849779U CN 208849779 U CN208849779 U CN 208849779U CN 201821752688 U CN201821752688 U CN 201821752688U CN 208849779 U CN208849779 U CN 208849779U
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Abstract
The utility model proposes a kind of phase decoding device and quantum key distribution systems.The phase decoding device is used to carry out phase decoding to input optical pulse, comprising: beam splitter；Bundling device；And merge with beam splitter optocoupler and two optical paths of bundling device optical coupling, beam splitter is coupled to bundling device through two optical paths, at least one of beam splitter front end or two optical paths be upper to have a phase-modulator, and two of them optical path and optical device thereon are configured so as to differ the integral multiple of 2 π during each comfortable beam splitter beam splitting of two orthogonal polarisation states of input optical pulse closes beam to bundling device through the phase difference of two optic paths.The utility model can effectively solve light pulse polarization state and change the influence generated to system stability at random, realize the stable phase angle decoding of environment resistant interference.In addition, unequal arm Mach-Zender interferometer can be used in the utility model, light pulse need to only pass through a phase-modulator in decoding, reduce the insertion loss of receiving end, improve system effectiveness.
Description
Technical field
The utility model relates to optical transport private communication technology field more particularly to a kind of phase decoding method, apparatus and
Quantum key distribution system.
Background technique
Based on quantum key distribution technology and one time cryptosystem principle, quantum secret communication can realize letter in overt channel
The safe transmission of breath, and gradually move towards application.For the phase code quantum key distribution system based on unequal arm interferometer
System, during light pulse is through Fiber quantum transmission, because there are non-circular symmetrical, the fiber core refractive index edges in section for optical fiber fabrication
The non-idealities such as radially non-uniform distribution and optical fiber are influenced by temperature, strain, bending etc. in the actual environment and are generated double
Refraction effect, polarization state of the light pulse when reaching receiving end can occur to change at random, cause phase decoding interferometer output knot
Fruit is unstable, and this phenomenon is obvious as the increase of fiber distance deteriorates.
Propose a kind of unequal arm faraday-Michelson's interferometer in the prior art, can make light pulse by
Fiber channel random birefringence and derived from this polarization state change influence when, still keep result of interference stablize output.But this
Kind interferometer loss is big, and wherein the Insertion Loss of phase-modulator is one of the principal element caused compared with lossy.Specifically, working as phase
When position modulator is placed in an arm of interferometer, light pulse can be by phase-modulator twice, to cause to do due to carrying out transmission back
The loss of interferometer is larger, and system effectiveness is relatively low.
Utility model content
The main purpose of the utility model is that propose a kind of phase decoding method, apparatus and quantum key distribution system,
To solve interference output knot in receiving end caused by changing in the application of phase code quantum key distribution because of polarization state above-mentioned
The unstable problem of fruit.
The utility model provides at least following technical scheme:
1. a kind of phase decoding device carries out phase solution for the input optical pulse all the way to incident random polarization state
Code, which is characterized in that the phase decoding device includes: beam splitter；Bundling device；And merge with the beam splitter optocoupler and institute
Two optical paths of bundling device optical coupling are stated, wherein the beam splitter is coupled to the bundling device through two optical paths, wherein institute
Stating has a phase-modulator at least one optical path in beam splitter front end or two optical paths, wherein described two
Optical path and optical device thereon are configured so that each leisure beam splitter of two orthogonal polarisation states of the input optical pulse point
The phase difference through two optic paths differs the integral multiple of 2 π during beam to bundling device conjunction beam.
2. phase decoding device according to scheme 1, which is characterized in that two optical paths are free space optical path,
Optical device in two optical paths is that non-birefringent optical device and/or polarization keep optical device.
3. phase decoding device according to scheme 1, which is characterized in that two optical paths are polarization maintaining optical fibre optical path,
Optical device in two optical paths is that polarization keeps optical device and/or non-birefringent optical device.
4. the phase decoding device according to scheme 2 or 3, which is characterized in that the phase decoding device further include:
Polarization maintaining optical fibre stretcher, the polarization maintaining optical fibre stretcher are located in any optical path in two optical paths；And/or
Birefringent phase modulator, the birefringent phase modulator are located in any optical path in two optical paths.
5. phase decoding device according to scheme 1, which is characterized in that the phase decoding device uses unequal arm horse
The structure of conspicuous-Zeng Deer interferometer or unequal arm Michelson's interferometer.
6. according to phase decoding device described in scheme 1 or 3 or 5, which is characterized in that the phase decoding device is not using
The structure of equiarm Mach-Zender interferometer, two optical paths are polarization maintaining optical fibre optical path, wherein the polarization-maintaining of two optical paths
The difference of fiber lengths is the integral multiple of beat length of polarization maintaining optical fiber.
7. according to phase decoding device described in scheme 1 or 3 or 5, which is characterized in that the phase decoding device is not using
The structure of equiarm Michelson's interferometer, two optical paths are polarization maintaining optical fibre optical path, wherein the polarization-maintaining light of two optical paths
The difference of fine length is the integral multiple of the half of beat length of polarization maintaining optical fiber.
8. the phase decoding device according to scheme 1 or 5, which is characterized in that the phase decoding device is used and differed
The structure of arm Michelson's interferometer, the bundling device and the beam splitter are same device, and the phase decoding device also wraps
It includes:
Two reflecting mirrors, described two reflecting mirrors are located in two optical paths, and being respectively used to will be from described point
The two-way light pulse of beam device come through two optic paths is reflected back the bundling device,
Wherein the input port of the unequal arm Michelson's interferometer and output port are same port, the phase solution
Code device further include:
Optical circulator, the optical circulator are located at the beam splitter front end, and the optical circulator has first port, second
Port and third port, the first port are optically coupled to described point for receiving the input optical pulse, the second port
Beam device, the third port is for exporting.
9. a kind of quantum key distribution system characterized by comprising single-photon source is optically coupled to the single-photon source
Phase encoder, quantum channel, any phase decoding device in single-photon detector and scheme 1~8, wherein described
Phase decoding device is coupled to the phase encoder through the quantum channel, and the single-photon detector is coupled to the phase
Decoding apparatus.
10. quantum key distribution system according to scheme 9, which is characterized in that the phase encoder uses scheme 1
Any phase decoding device in~8.
As previously mentioned, in general, can cause to be transmitted to receiving end because of environment influence when light pulse is through Fiber quantum transmission
The polarization state of light pulse generate random variation, influence quantum secret communication system job stability.The utility model can be effective
It solves input optical pulse polarization state and changes the influence generated to system stability at random, realize what transmission fiber environmental disturbances were immunized
Stable phase angle decoding.In addition, the utility model does not constrain the type for the interferometer that phase decoding device uses, can be used most
Common unequal arm Mach-Zender interferometer reduce light pulse need to only by a phase-modulator in decoding
The insertion loss of receiving end, appreciably improves system effectiveness.The utility model makes it possible to provide a kind of stabilization of filter with low insertion loss
Highly effective quantum key distribution system technical solution.In addition, the embodiment of the utility model is easily achieved.
Detailed description of the invention
Fig. 1 is the flow chart of the phase decoding method of one preferred embodiment of the utility model；
Fig. 2 is the composed structure schematic diagram of the phase decoding device of one preferred embodiment of the utility model；
Fig. 3 is the composed structure schematic diagram of the phase decoding device of another preferred embodiment of the utility model；
Fig. 4 is the composed structure schematic diagram of the phase decoding device of another preferred embodiment of the utility model；
Fig. 5 is the composed structure schematic diagram of the quantum key distribution system of one preferred embodiment of the utility model.
Specific embodiment
Specifically describe the preferred embodiment of the utility model with reference to the accompanying drawing, wherein attached drawing constitutes the one of the application
Part, and be used to illustrate the principles of the present invention together with the embodiments of the present invention.For purpose of clarity and simplification, when
When it may make the theme of the utility model smudgy, to the detailed tool of the known function and structure of device described herein
Body explanation will be omitted.
A kind of phase decoding method of one preferred embodiment of the utility model as shown in Figure 1, specifically includes the following steps:
Step S101: being two-way light pulse by the beam splitting of input optical pulse all the way of incident random polarization state.
Specifically, the polarization state of incident input optical pulse can be random polarization state, it can regard orthogonal inclined by two as
Polarization state composition.Naturally, the two-way light pulse that beam splitting obtains can also be regarded as equally by identical with incident input optical pulse
Two orthogonal polarisation state compositions.
Step S102: transmitting the obtained two-way light pulse of beam splitting in two optical paths respectively, and by this two-way light arteries and veins
Beam output is closed after rushing in row relative time delay.
In the method, can before beam splitting to the input optical pulse before beam splitting according to quantum key distribution agreement into
Row phase-modulation, or beam splitting to close beam during in the two-way light pulse at least all the way light pulse according to quantum
Key distribution protocol carries out phase-modulation.
Here, relative time delay and phase-modulation are carried out according to the requirement and regulation of quantum key distribution agreement, are not made herein
It is described in detail.
In the method, each comfortable beam splitting of two orthogonal polarisation states of input optical pulse is controlled to closing during beam through institute
The phase difference for stating two optic paths differs the integral multiple of 2 π.
For example, it is assumed that the two orthogonal polarisation states are respectively x-polarisation state and y-polarisation state, by x-polarisation state beam splitting extremely
The phase meter through two optic paths is shown as Δ x during closing beam, by y-polarisation state through two during beam splitting to conjunction beam
The phase meter of optic path is shown as Δ y, then each comfortable beam splitting of the two of light pulse orthogonal polarisation state is to during closing beam
The integral multiple that phase difference through two optic paths differs 2 π can indicate are as follows:
Δ x-Δ y=2 π .m,
Wherein m is integer, can be positive integer, negative integer or zero.
In a kind of possible embodiment, beam splitting and two optical paths closed between beam include for the input optical pulse
Two orthogonal polarisation states there are have to there are two orthogonal polarisation states in birefringent optical path and/or this two optical paths
Birefringent optical device.In this case, each comfortable beam splitting of two orthogonal polarisation states for controlling the input optical pulse is extremely closed
It includes: to keep the two cross-polarizations respectively that phase difference during beam through two optic paths, which differs the integral multiple of 2 π,
When transmitting in two optical paths, polarization state is constant during each comfortable beam splitting to conjunction beam of state；And there are birefringent for adjustment
Optical path length and/or birefringent size there are birefringent optical device so that each comfortable point of the two orthogonal polarisation states
Phase difference during Shu Zhihe beam through two optic paths differs the integral multiple of 2 π.Optionally, this can by with
Under any realization: i) configure polarization maintaining optical fibre optical path for two optical paths, the optical device in the polarization maintaining optical fibre optical path matched
It is set to non-birefringent optical device and/or polarization keeps optical device；Ii free space optical path) is configured by two optical paths, it will
Optical device in two optical paths is configured to polarization and keeps optical device.Herein, " polarization maintaining optical fibre optical path " refers to using polarization-maintaining
The optical path or polarization maintaining optical fibre of light transmission fiber pulse connect the optical path to be formed." non-birefringent optical device " refers to for different inclined
Polarization state (for example, two orthogonal polarisation states) has the optical device of identical refractive index.In addition, polarization keeps optical device alternatively referred to as to protect
Polarizing device.
In a kind of possible embodiment, free space optical path can be configured by two optical paths, by described two
Optical device in optical path is configured to non-birefringent optical device.In this case, each comfortable beam splitting of the two orthogonal polarisation states is extremely
When transmitting in two optical paths, polarization state is remained unchanged during conjunction beam, and each comfortable point of the two orthogonal polarisation states
Phase difference through two optic paths during Shu Zhihe beam can be identical.
In a kind of possible realization, polarization maintaining optical fibre stretcher is configured at least one optical path in two optical paths
And/or birefringent phase modulator.Polarization maintaining optical fibre stretcher is suitable for adjusting the polarization maintaining optical fibre length of the optical path where it.It is birefringent
Phase-modulator is suitable for applying different adjustable phase-modulations to by its two orthogonal polarisation states, thus can be provided to
Through two optical paths biography during each comfortable beam splitting to conjunction beam of two orthogonal polarisation states of influence and adjustment input optical pulse
The difference of defeated phase difference.For example, birefringent phase modulator can be lithium niobate phase modulator, niobic acid is applied to by control
The voltage of crystalline lithium, the phase-modulation that can be respectively subjected to two orthogonal polarisation states by the phase-modulator are controlled
System and adjustment.Birefringent phase modulator can be used for influencing and adjusting two orthogonal polarisation states of input optical pulse respectively as a result,
In beam splitting to the difference of the phase difference through two optic paths during closing beam.
A kind of phase decoding device of one preferred embodiment of the utility model is as shown in Fig. 2, include consisting of part: point
Beam device 201, phase-modulator 202, bundling device 203.Beam splitter 201 and bundling device 203 pass through two optical path optical couplings, phase tune
Device 202 processed is located in one of in optical path.
Beam splitter 201 is used to the beam splitting of input optical pulse all the way of incident random polarization state be two-way light pulse.
The two-way light pulse that two optical paths between beam splitter 201 and bundling device 203 are obtained for transmitting beam splitting respectively, and
Realize the relative time delay of this two-way light pulse.
Specifically, being realized by the physical transfer length for adjusting two optical paths between beam splitter 201 and bundling device 203
The relative time delay of this two-way light pulse.
Phase-modulator 202 is used for close according to quantum to one of above-mentioned two-way light pulse through the optic path where it
Key distribution protocol carries out phase-modulation.
Although Fig. 2 shows phase-modulator is arranged between beam splitter 201 and bundling device 203, i.e., in beam splitting to conjunction beam
One of two-way light pulse obtained in the process to beam splitting carries out phase-modulation according to quantum key distribution agreement, it is also possible to
It is phase-modulator to be set in 201 front end of beam splitter, i.e., to the random polarization state of the incidence before beam splitting before beam splitting
Input optical pulse carries out phase-modulation according to quantum key distribution agreement all the way.
In addition, although showing only one phase-modulator in Fig. 2, between beam splitter 201 and bundling device 203 two
It is also possible that a phase-modulator, which is arranged, in every optical path in optical path.In setting, there are two the feelings of phase-modulator
Under condition, the difference for the phase that two phase-modulators are modulated is determined by quantum key distribution agreement.
Bundling device 203 for will through relative time delay, two-way light pulse that beam splitting obtains close beam output.
According to the utility model, two optical paths and optical device thereon are constructed such that, the input optical pulse
Each comfortable beam splitting of two orthogonal polarisation states to the phase difference through two optic paths during closing beam differ the whole of 2 π
Several times.
In this regard, an optical path depends on for two orthogonal polarisation states there may be birefringent or there is no birefringent
In the type of the optical path.For example, free space optical path for input optical pulse all the way two orthogonal polarisation states there is no two-fold
Penetrate, and polarization maintaining optical fibre optical path for input optical pulse all the way two orthogonal polarisation states usually exist differ greatly each other it is two-fold
It penetrates.In addition, an optical device in optical path for two orthogonal polarisation states there may be birefringent or there is no birefringent, depend on
In the type of the optical device.For example, a non-birefringent optical device for input optical pulse all the way two orthogonal polarisation states not
There are birefringent, and a polarization keeps optical device usually to there are each other two orthogonal polarisation states of input optical pulse all the way
What is differed greatly is birefringent.
According to the utility model, the type and/or length of above-mentioned two optical paths and the type of optical device thereon and/or double
Refraction size causes each comfortable beam splitting of two orthogonal polarisation states of the input optical pulse to closing during beam through described two
The phase difference of optic path differs the integral multiple of 2 π.
In a kind of possible embodiment, the optical path between beam splitter 201 and bundling device 203 is free space optical path,
Other optical devices in phase-modulator 202 and optical path are that non-birefringent optical device and/or polarization keep optical device.For the reality
Mode is applied, in the case where there is polarization to keep optical device, polarization holding optical device itself leads to two cross-polarizations of light pulse
Phase difference of the state through two optic paths between beam splitter 201 and bundling device 203 differs the integral multiple of 2 π.
In a kind of possible embodiment, two optical paths between beam splitter 201 and bundling device 203 are polarization maintaining optical fibre light
Road, other optical devices in phase-modulator 202 and optical path are that polarization keeps optical device and/or non-birefringent optical device.
In a kind of possible embodiment, phase decoding device can also include fiber stretcher and/or birefringent phase
Position modulator.
The fiber stretcher can be in any optical path in two optical paths between beam splitter 201 and bundling device 203, can
For adjusting the polarization maintaining optical fibre length of the optical path where it.By adjusting polarization maintaining optical fibre length by means of fiber stretcher, can have
It is easily achieved two orthogonal polarisation states of light pulse sharply between beam splitter 201 and bundling device 203 through two optic paths
Phase difference differs the integral multiple of 2 π.
The birefringent phase modulator can be located in any optical path in above-mentioned two optical paths, can be used for the light by it
Two orthogonal polarisation states of pulse apply different phase-modulations.By controlling the birefringent phase modulator, pass through its light
The difference for the phase-modulation that two orthogonal polarisation states of pulse are respectively subjected to is adjustable.In this way, by utilizing birefringent phase tune
Device processed, it is convenient to through described two during each comfortable beam splitting to conjunction beam of two orthogonal polarisation states of influence and adjustment light pulse
The difference of the phase difference of optic path, it is easy to accomplish the integral multiple that the difference is 2 π.Before the birefringent phase modulator can be
Lithium niobate phase modulator described in text.
Optionally, unequal arm Mach-Zender interferometer or unequal arm Michelson can be used in the phase decoding device
The structure of interferometer.
In a kind of possible embodiment, the phase decoding device is using unequal arm Mach-Zender interferometer
The optical path (that is, two optical paths between beam splitter and bundling device) of structure, interferometer two-arm uses polarization maintaining optical fibre, this two optical paths
Polarization maintaining optical fibre length difference be beat length of polarization maintaining optical fiber integral multiple.In this case, the optical device in two optical paths leads to light
The phase difference through two optic paths differs 2 between each comfortable beam splitter 201 of two orthogonal polarisation states of pulse and bundling device 203
The integral multiple of π.
In a kind of possible embodiment, the phase decoding device uses the knot of unequal arm Michelson's interferometer
Structure, interferometer two-arm optical path (that is, with for same device beam splitter and bundling device optical coupling, be respectively used to transmission beam splitting
Two optical paths of obtained two-way light pulse) polarization maintaining optical fibre is used, the difference of the polarization maintaining optical fibre length of this two optical paths is polarization-maintaining light
Fibre claps the integral multiple of long half.In this case, other optical devices in two optical paths cause two of light pulse it is orthogonal partially
The integral multiple of 2 π is differed during each comfortable beam splitting to conjunction beam of polarization state through the phase difference of two optic paths.
" beat length of polarization maintaining optical fiber " is concept well known in the art, refers to two polarization eigen states of polarization maintaining optical fibre along polarization maintaining optical fibre
Transmission generates polarization maintaining optical fibre length corresponding to the phase difference of 2 π.
For the embodiment of Fig. 2, beam splitter 201 preferably uses polarization-maintaining beam splitter, and bundling device 203 preferably closes beam using polarization-maintaining
Device.
In a kind of possible embodiment, the phase decoding device uses the knot of unequal arm Michelson's interferometer
Structure.At this point, bundling device and beam splitter are same device.In the case, phase decoding device further includes two reflecting mirrors, this two
A reflecting mirror is located in two optical paths for being previously described for the two-way light pulse that transmission beam splitting obtains, and is respectively used to come from
The two-way light pulse of beam splitter come through two optic paths reflects back so as to by being same device with beam splitter
Bundling device close beam output.In addition, the input port and output port of unequal arm Michelson's interferometer can be same port,
And phase decoding device further includes optical circulator.
The optical circulator can be located at beam splitter front end.Input optical pulse can input and from light from the first port of optical circulator
The second port of circulator is exported to beam splitter.Conjunction beam output from bundling device (being same device with beam splitter) can be input to
The second port of optical circulator is simultaneously exported from the third port of optical circulator.
A kind of phase decoding device of another preferred embodiment of the utility model is as shown in figure 3, once using unequal arm Mach-
Dare interferometer structure, including consisting of part: beam splitter 303, phase-modulator 304, bundling device 305.
Input terminal of one of two ports 301 and 302 of the side of beam splitter 303 as phase decoding device, bundling device
Output end of one of two ports 306 and 307 of 305 side as phase decoding device, phase-modulator 304 are inserted into horse
Any arm in two arms of conspicuous-Zeng Deer interferometer.When work, the input optical pulse all the way of incident random polarization state is through dividing
The port 301 or 302 of beam device 303 is divided into two-way optical pulse propagation into beam splitter 303, wherein light pulse is directly transferred to all the way
Bundling device 305, the phase modulated device 304 of another way light pulse are transmitted to bundling device 305, two-way light pulse after carrying out phase-modulation
Beam is closed by bundling device 305 after relative time delay and is exported after closing beam by port 306 or 307.Beam splitter 303 and bundling device 305
Polarization-maintaining fiber coupler can be used, phase-modulator 304 can be the unrelated device of polarization.Adjust beam splitter 303 and bundling device
The length of the polarization maintaining optical fibre of two optical paths between 305, so that two orthogonal polarisation states of light pulse are in beam splitter 303 and bundling device
Phase difference through two optic paths between 305 is equal or differs the integral multiple of 2 π.If between beam splitter 303 and bundling device 305
Optical device have optical device for the two cross-polarizations between non-birefringent optical device or beam splitter 303 and bundling device 305
There are birefringent and thus caused two orthogonal polarisation states pass between beam splitter 303 and bundling device 305 through two optical paths for state
The difference of defeated phase difference is the integral multiple of 2 π, and the polarization maintaining optical fibre for adjusting two optical paths between beam splitter 303 and bundling device 305 is long
The difference of degree is the integral multiple of beat length of polarization maintaining optical fiber.Adjusting polarization maintaining optical fibre length can be by accurate cutting optical fiber or in Mach-Zehnder
Any arm setting polarization maintaining optical fibre stretcher of your interferometer is realized.
The phase decoding device of another preferred embodiment of the utility model is as shown in figure 4, dry using unequal arm Michelson
Interferometer structure, including consisting of part: 405, two beam splitter 403, phase-modulator reflecting mirrors 404 and 406.
Input terminal and output of two ports 401 and 402 of the side of beam splitter 403 respectively as phase decoding device
End；One of two ports of the other side of beam splitter 403 are directly connected to reflecting mirror 404, and ipsilateral another port is then linked in sequence phase
Position modulator 405, reflecting mirror 406.When work, the input optical pulse all the way of incident random polarization state is through the end of beam splitter 403
Mouthfuls 401, which are divided into two-way light pulse into beam splitters 403, is transmitted, and is transmitted to reflecting mirror 404 and anti-via reflecting mirror 404 all the way
It is emitted back towards and, be transmitted to reflecting mirror 406 after the phase modulated progress of device 405 phase-modulation of another way and be reflected back again by reflecting mirror 406
Come, two-way light closes beam through beam splitter 403 after relative time delay and exported after closing beam by port 402.Light pulse is defeated by port 402
Enter, exported by port 401 and using port 401 or 402 while as when outputting and inputting, it is as a result identical.With port 401 or 402
Simultaneously as unequal arm Michelson's interferometer when outputting and inputting, while as the port (beam splitter output and input
403 port 401 or 402) it is connect with optical circulator；First port input of the input optical pulse through optical circulator and from the light
The second port of circulator is exported to beam splitter 403, is then two-way light pulse by 403 beam splitting of beam splitter；This two-way light pulse
Beam output is closed by beam splitter 403 after relative time delay, which is input to the second port of optical circulator and from optical circulator
Third port output.Polarization-maintaining fiber coupler can be used in beam splitter 403, and phase-modulator 405 can be the unrelated device of polarization.
The length of the polarization maintaining optical fibre between beam splitter 403 and two reflecting mirrors 404 and 406 is adjusted, so that two of light pulse are orthogonal inclined
Polarization state phase difference through two optic paths between beam splitter 403 and two reflecting mirrors 404 and 406 is equal or differs the whole of 2 π
Several times.If the optical device between beam splitter 403 and two reflecting mirrors 404 and 406 is non-birefringent optical device or beam splitter 403
Between two reflecting mirrors 404 and 406 it is birefringent for the two orthogonal polarisation states with the presence of optical device and thus caused by two
A orthogonal polarisation state is during beam splitting to conjunction beam through two optical paths between beam splitter 403 and two reflecting mirrors 404 and 406
The difference of the phase difference of transmission is the integral multiple of 2 π, adjusts two optical paths between beam splitter 403 and two reflecting mirrors 404 and 406
Polarization maintaining optical fibre length difference be beat length of polarization maintaining optical fiber half integral multiple.Adjustment polarization maintaining optical fibre length can pass through accurate cutting optical fiber
Or it is realized in any arm setting polarization maintaining optical fibre stretcher of unequal arm Michelson's interferometer.
Herein, term " beam splitter " and " bundling device " are used interchangeably, and beam splitter is also referred to as and as bundling device, instead
?.
The phase decoding device of the utility model can be configured in the receiving end of quantum key distribution system, be used for phase solution
Code.The phase decoding device of the utility model is configured alternatively, it is also possible to the transmitting terminal in quantum key distribution system, is used for phase
Coding.
Although the embodiment of Fig. 3 and 4 one of beam splitting to two-way light pulse that beam splitting is obtained during closing beam by
Phase-modulation is carried out according to quantum key distribution agreement, it is also possible to: beam splitting is obtained during beam splitting to conjunction beam
Two-way light pulse carries out phase-modulation according to quantum key distribution agreement respectively, or to entering described in front of beam splitting before beam splitting
The input optical pulse all the way for the random polarization state penetrated carries out phase-modulation according to quantum key distribution agreement.
A kind of quantum key distribution system of one preferred embodiment of the utility model is as shown in figure 5, include consisting of portion
It is divided to: 503, two single-photon source 501, phase encoder 502, quantum channel single-photon detectors 505 and 506, and as above
The phase decoding device 504 of introduction.
Single-photon source 501 is for generating single-photon optical pulse.
The single-photon optical pulse that phase encoder 502 is used to generate single-photon source 501 is according to quantum key distribution agreement
Carry out phase code.
Quantum channel 503 is used for transmission single-photon optical pulse.Particularly, quantum channel 503 is by the monochromatic light through phase code
Sub-light pulse is transmitted to phase decoding device 504.
Phase decoding device 504 is used for according to quantum key distribution agreement to the single photon come through the transmission of quantum channel 503
Light pulse carries out phase decoding.
The single-photon optical pulse that single-photon detector 505 and 506 is used to export phase decoding device 504 detects,
And according to testing result and quantum key distribution agreement carry out quantum key distribution.
Single-photon source 501 emits a single-photon optical pulse and enters phase encoder 502, and phase encoder 502 is to monochromatic light
Sub-light pulse carries out phase code, and the light pulse after phase code is transmitted to phase decoding device 504, phase through quantum channel 503
The incident single photon pulses in 504 pairs of decoding apparatus of position carry out phase decoding, and the light pulses that phase decoding device 504 exports are extremely
Single-photon detector 505 or single-photon detector 506.Phase encoder 502 and phase decoding device 504 are according to quantum key point
It sends out agreement and phase code and phase decoding is carried out to light pulse respectively, and key distribution is carried out according to quantum key distribution agreement.
Specifically, phase encoder 502 using it is following any one: unequal arm Mach-Zender interferometer, unequal arm step
Ke Erxun interferometer, unequal arm faraday-Michelson's interferometer, above-described phase decoding device.
Quantum channel 503 can be optical waveguide, optical fiber, free space, discrete optical element, planar waveguide optical element,
Fibre optic member or among the above any two combination of the above at light propagation channel.
By by the beam splitting of input optical pulse all the way of incident random polarization state being two-way respectively through two at receiving end
Optical path is transmitted, and to each comfortable beam splitting of two orthogonal polarisation states of the input optical pulse to closing during beam through this two
Relationship between the phase difference of optic path is controlled, and the utility model makes the input optical pulse for random polarization state can
Stablize interference output to realize.
In addition, interferometer used in the phase decoding device of receiving end can be various types using the utility model
--- including unequal arm Mach-Zender interferometer, and it is not limited to unequal arm Michelson's interferometer.Thus, pass through
Suitable interferometer is selected, the lower Insertion Loss in receiving end may be implemented while solving system instability.
It should be able to be the technical means and efficacy reaching predetermined purpose and being taken to the utility model by explanation above
Have and more deeply and specifically understand, however appended diagram is only to provide reference and description and is used, and is not used to practical newly to this
Type limits.
Claims (10)
1. a kind of phase decoding device carries out phase decoding for the input optical pulse all the way to incident random polarization state,
It is characterized in that, the phase decoding device includes: beam splitter；Bundling device；And merge with the beam splitter optocoupler and the conjunction
Two optical paths of beam device optical coupling, wherein the beam splitter is coupled to the bundling device through two optical paths, wherein described point
There is a phase-modulator, wherein two optical paths at least one optical path in beam device front end or two optical paths
And optical device thereon is configured so that each leisure of two orthogonal polarisation states beam splitter beam splitting of the input optical pulse extremely
The phase difference through two optic paths differs the integral multiple of 2 π during the bundling device conjunction beam.
2. phase decoding device according to claim 1, which is characterized in that two optical paths are free space optical path,
Optical device in two optical paths is that non-birefringent optical device and/or polarization keep optical device.
3. phase decoding device according to claim 1, which is characterized in that two optical paths are polarization maintaining optical fibre optical path,
Optical device in two optical paths is that polarization keeps optical device and/or non-birefringent optical device.
4. phase decoding device according to claim 2 or 3, which is characterized in that the phase decoding device further include:
Polarization maintaining optical fibre stretcher, the polarization maintaining optical fibre stretcher are located in any optical path in two optical paths；And/or
Birefringent phase modulator, the birefringent phase modulator are located in any optical path in two optical paths.
5. phase decoding device according to claim 1, which is characterized in that the phase decoding device uses unequal arm horse
The structure of conspicuous-Zeng Deer interferometer or unequal arm Michelson's interferometer.
6. phase decoding device described according to claim 1 or 3 or 5, which is characterized in that the phase decoding device is not using
The structure of equiarm Mach-Zender interferometer, two optical paths are polarization maintaining optical fibre optical path, wherein the polarization-maintaining of two optical paths
The difference of fiber lengths is the integral multiple of beat length of polarization maintaining optical fiber.
7. phase decoding device described according to claim 1 or 3 or 5, which is characterized in that the phase decoding device is not using
The structure of equiarm Michelson's interferometer, two optical paths are polarization maintaining optical fibre optical path, wherein the polarization-maintaining light of two optical paths
The difference of fine length is the integral multiple of the half of beat length of polarization maintaining optical fiber.
8. phase decoding device according to claim 1 or 5, which is characterized in that the phase decoding device is used and differed
The structure of arm Michelson's interferometer, the bundling device and the beam splitter are same device, and the phase decoding device also wraps
It includes:
Two reflecting mirrors, described two reflecting mirrors are located in two optical paths, are respectively used to that the beam splitter will be come from
Through two optic paths come two-way light pulse be reflected back the bundling device,
Wherein the input port of the unequal arm Michelson's interferometer and output port are same port, the phase decoding dress
It sets further include:
Optical circulator, the optical circulator are located at the beam splitter front end, and the optical circulator has first port, second port
And third port, for the first port for receiving the input optical pulse, the second port is optically coupled to the beam splitter,
The third port is for exporting.
9. a kind of quantum key distribution system characterized by comprising single-photon source, the phase for being optically coupled to the single-photon source
Position encoder, quantum channel, single-photon detector and phase decoding device according to any one of claims 1 to 8, wherein institute
It states phase decoding device and is coupled to the phase encoder through the quantum channel, the single-photon detector is coupled to the phase
Position decoding apparatus.
10. quantum key distribution system according to claim 9, which is characterized in that the phase encoder uses right
It is required that phase decoding device described in any one of 1~8.
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| CN109150524A (en) * | 2018-10-29 | 2019-01-04 | 中国电子科技集团公司电子科学研究院 | A kind of phase decoding method, apparatus and quantum key distribution system |
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