CN101571612B - Polarization controlling encoder - Google Patents
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- CN101571612B CN101571612B CN2009101319808A CN200910131980A CN101571612B CN 101571612 B CN101571612 B CN 101571612B CN 2009101319808 A CN2009101319808 A CN 2009101319808A CN 200910131980 A CN200910131980 A CN 200910131980A CN 101571612 B CN101571612 B CN 101571612B
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Abstract
The invention relates to a polarization controlling encoding method, an encoder and a quantum key dispatching system. The invention is characterized in that the interior of the encoder adopts a polarization-maintaining light path or a ninety-degree Faraday rotation reflector reflection to cause output optical pulse polarization state to be the same; the optical pulse output by the sending terminalof the quantum key dispatching system taking the polarization controlling encoder as the core is passed to the receiving terminal thereof by a quantum channel in a uni-directional way; according to t he superposition interference results of the optical pulse and distributorship agreement of the quantum key, the quantum key dispatching is realized. The polarization controlling encoder causes the whole system (comprising a sending set, a reception unit and the quantum channel) to have the interference free capability. The outlet of the sending set and the inlet of the receiving set of the systemare added with a reversal photon separation detection unit, thus preventing the invasion of the modulation information and carrying the photon to get off the reception unit of Trojan photon. The quan tum key dispatching system can realize unconditional secure assignment of the key.
Description
Technical field
The invention belongs to light transmission private communication technology field, particularly coding method in the quantum-key distribution and device.
Background technology
Early stage quantum-key distribution is used the photon polarization encoder, and this mode is suitable for free-space communication and is not suitable for the optical fiber communication system.Do not show as the influence to polarized state of light because the ordinary optic fibre symmetry is not the interference in fine, the transmission path, so the polarization state can't keep light to propagate therein the time, polarization encoder also just is not suitable in optical fiber, using.U.S. Patent number 5307410 has been announced the phase encoding quantum-key distribution scheme of a pair of unequal arm Mach-Ceng Te of a kind of usefulness (Mach-Zehnder) interferometer for the basis; Its receive with dispensing device in light pulse experience respectively Mach-dissimilar arm of special interferometer once; Because the interference that dissimilar arm receives can not be in full accord; Can't offset fully mutually, therefore stability is bad, poor anti jamming capability; Again because two photon pulses respectively through Mach-once the dissimilar arm of special interferometer had experienced different light paths; The polarization state of two pulses can not guarantee to confirm relation during the inlet subchannel; Therefore very sensitive to the interference in the quantum channel; This interference is particularly serious during the long-range quantum-key distribution, the improvement of all unprincipled property of multiple variant version of this scheme.
Stability problem in view of two unequal arm M-Z interferometer scheme existence; U.S.'s " applied physics wall bulletin " (Appl.Phys.Lett.77 (7); 793 (1997)) a solution has been proposed; Make two light pulses between transmission and acceptance point, transmit one back and forth with faraday's catoptron, each light pulse through all light paths has once reached self-compensating effect.Undesired signal had little time to change when this scheme supposition photon pulse was gone through same position twice back and forth, suffered the interferences unanimity of light pulse, thus interference effect is cancelled each other and is reached anti-interference and stable purpose during stack.And in fact, this stable only not oversize effective when not too high with interfering frequency in transmission range, when transmission range increased, the mistiming increase of same position was experienced in light pulse back and forth, and antijamming capability also just decreases; In addition; Because light pulse will be in quantum channel twice back and forth; Loss when the channel total losses equal actual amount subchannel double length is adopted usually and is gone the method for Cheng Qiangguang and backhaul single photon to remedy this defective, but this method that remedies only is applicable to the present situation with overdamp laser pulse simulation single-photon source; The light source of desirable quantum-key distribution should be a single-photon source; But present desirable single-photon source can't be practical, in case use desirable single-photon source, the limit transmission range of this scheme has only present half the; A more serious defective is that this scheme has hidden potential safety hazard: the listener-in possibly decay getting into the preceding strong signal of reception area in proportion; Replenish with wavelength and the very approaching wooden horse signal of operation wavelength again, make that the total monitoring signal intensity in the reception area is constant, i.e. the signal intensity monitors failure; When signal returns; The wooden horse signal can and detect entrained information by listener-in's separation, passes the original signal photon back sender by " super low-loss channel " again, as long as the suitable control signal attenuation ratio of listener-in; The reception code check that just can accomplish system is unaffected, does not find thereby be sent out the person.Concerning information security technology, this hidden danger of eavesdropping is fatal.
Summary of the invention
The present invention proposes a kind of polarization controlling encoding method, according to the Polarization Control scrambler of this method construct and the quantum key dispatching system of forming by this scrambler; Can between two users, form one group of quantum key of not eavesdropped, realize that the unconditional security of key distributes.
Polarization Control scrambler of the present invention comprises: 2 * 2 3dB beam splitters; Be used for a light pulse of incident is beamed into two light pulses; Said 2 * 2 3dB beam splitters have first port, second port, the 3rd port and the 4th port; Wherein first port and second port are positioned at a side of said 2 * 2 3dB beam splitters, and the 3rd port and the 4th port are positioned at the opposite side of said 2 * 2 3dB beam splitters; Delay line is used for one of said two light pulses are applied time-delay; Phase-modulator is used for light pulse is carried out phase modulation (PM) by the quantum key sharing agreement; And the one 90 degree rotation faraday's catoptron and the 2 90 degree rotation faraday catoptron; First port of wherein said 2 * 2 3dB beam splitters is as the output terminal of said Polarization Control scrambler, and second port of said 2 * 2 3dB beam splitters is as the input end of said Polarization Control scrambler; The 3rd port of said 2 * 2 3dB beam splitters links to each other with the one 90 degree rotation faraday catoptron; And the 4th port of said 2 * 2 3dB beam splitters and the 2 90 degree rotation faraday catoptron link to each other, and said 2 * 2 3dB beam splitters will close Shu Weiyi Lu Guangcong output terminal through two light pulses of the first and second 90 degree rotation faraday mirror reflects and export; Said delay line is connected between the 4th port and said the 2 90 degree rotation faraday catoptron of said 2 * 2 3dB beam splitters; And said phase-modulator is connected between the 3rd port and said the one 90 degree rotation faraday catoptron of said 2 * 2 3dB beam splitters; Perhaps be connected between the 4th port and said the 2 90 degree rotation faraday catoptron of said 2 * 2 3dB beam splitters, perhaps the output terminal with said Polarization Control scrambler links to each other.
Polarization Control scrambler of the present invention can be used in the transmitting terminal of quantum key dispatching system.Perhaps/and Polarization Control scrambler of the present invention also can be used in the receiving end of quantum key dispatching system.
Preferably; The transmitting terminal of said quantum key dispatching system can also comprise: optical circulator; Be positioned at the output terminal of said Polarization Control scrambler, export from second port of optical circulator, export from the 3rd port of optical circulator from the light that second port of optical circulator is imported from the light that first port of optical circulator is imported; From the output of said output terminal close light behind the bundle from first port input of optical circulator, and from second port output of optical circulator; Single-photon detector links to each other with the 3rd port of optical circulator, is used for the reverse input light from second port of optical circulator is detected.
More preferably, the transmitting terminal of said quantum key dispatching system can also comprise: optical band pass filter, link to each other with first port of optical circulator, and be used for light output the carrying out optical band pass filtering behind the bundle of closing from the output of said output terminal.
Quantum channel in the said quantum key dispatching system can be optical waveguide, optical fiber, free space, discrete optical element, slab guide optical element, fibre optic member or any light propagation ducts that is combined into more than two in them.
Compare with the existing scrambler that two unequal arm Mach-once special interferometer is formed; Because the polarization state of Polarization Control scrambler of the present invention portion's control within it light pulse; At first make scrambler insensitive to self suffered interference, quantum key dispatching system reduces environment requirement greatly; Simultaneously because the polarization state between two light pulses of inlet subchannel is identical; Make light pulse suffered interference in co-route when the receiving end stack is interfered, cancel each other; Realized that signal transmission and channel disturbance are irrelevant, improved the practical stability of system greatly; In 90 degree rotation faraday mirrored Polarization Control scramblers of the present invention; Because twice process of light pulse phase-modulator; And the polarization direction when passing through is orthogonal, as long as phase modulated signal lasts longer than light pulse twice elapsed time back and forth, then the polarization state of phase modulation size and light pulse is irrelevant; Therefore the phase-modulator that available polarization is relevant reaches the purpose of polarization irrelevant phase modulation (PM), and also can reduce the rate request of phase-modulator; In the Polarization Control scrambler of forming with polarization maintenance beam splitter of the present invention, because light pulse all is maintained on the specific polarization state, the phase-modulator that polarization is relevant is suitable for naturally.
In quantum key dispatching system of the present invention; Transmitting terminal and receiving end can increase reverse photon separation detection unit (optical circulator and single-photon detector); After having increased reverse photon separation detection unit; Because signal pulse is transferred to receiving trap from dispensing device is unidirectional through quantum channel, can single-photon detector separated and imported to the photon of any opposite direction transmission and detect, so not only can stop possible wooden horse photon to get into scrambler and carry out coded message; And can know whether have the listener-in to exist, stopped the possibility of being attacked by wooden horse; Consider that single-photon detector and optical circulator operation wavelength have certain limit; Can increase the logical spectral filter of band in the quantum key dispatching system of the present invention; Light pulse in the system works wavelength coverage can be passed through; The light of wavelength can not pass through beyond the operating wavelength range, remedies single-photon detector and the wide inadequately shortcoming of circulator operating wavelength range.
Description of drawings
Fig. 1 keeps the basic composition synoptic diagram of light path Mach-once special interferometer type Polarization Control scrambler for polarization.
Fig. 2 keeps the basic composition synoptic diagram of light path mirrored Polarization Control scrambler for polarization.
Fig. 3 is the basic composition synoptic diagram of 90 degree rotation faraday mirrored Polarization Control scramblers.
Fig. 4 is the basic composition synoptic diagram of the change type of 90 degree rotation faraday mirrored Polarization Control scramblers.
Fig. 5 is positioned at the basic composition synoptic diagram of 90 degree rotation faraday mirrored Polarization Control scramblers of output light path for phase-modulator.
Fig. 6 keeps the basic composition synoptic diagram of light path mirrored Polarization Control scrambler for the polarization that uses the variable light beam splitter.
Fig. 7 rotates the basic composition synoptic diagram of faraday's mirrored Polarization Control scramblers for 90 degree that use the variable light beam splitter.
Fig. 8 is a kind of synoptic diagram of reverse photon separation detection unit.
Fig. 9 is the another kind of synoptic diagram that increases the reverse photon separation detection unit of the logical spectral filter of band.
Figure 10 is for being the phase modulation (PM) optical fiber quantum key dispatching system structural representation of core with the Polarization Control scrambler.
Embodiment
Embodiment 1:
First kind of composition structure of the Polarization Control scrambler in the quantum key dispatching system of the present invention is as shown in Figure 1: it keeps beam splitter 3,6 by two 2 * 2 3dB polarization; A polarization keeps phase-modulator 5 and a polarization to keep delay line 4 to form, and constitutes a polarization jointly and keeps Mach-once special interferometer.Wherein the 3dB polarization keeps the two-port 1 and one of 2 input ends as the Polarization Control scrambler of a side of beam splitter 3; One of two- port 7,8 of the opposite side of 3dB polarization maintenance beam splitter 6 is as output terminal; Polarization keeps phase-modulator 5 and polarization to keep delay line 4 (order arbitrarily) to insert any arm of special interferometer of above-mentioned Mach-once together, or the two inserts two arms of special interferometer of above-mentioned Mach-once respectively.During work; Light pulse keeps the port one or 2 of beam splitter 3 to get into polarization maintenance beam splitter 3 through polarization and is divided into two-way; One tunnel process polarization keeps phase-modulator 5 to carry out phase modulation (PM), and another road keeps delay line 4 time-delays through polarization, and the two-way behind the relative time delay is through polarization maintenance beam splitter 6 synthetic routed ports 7 or 8 outputs; Because of being polarization, all light paths keep light path, so the polarization state of two pulses of output is identical thus.When polarization kept phase-modulator 5 and polarization to keep delay line 4 to be positioned at polarization keeping the same arm of the special interferometer of Mach-once, The above results was unaffected.
Embodiment 2:
Second kind of Polarization Control scrambler in the quantum key dispatching system of the present invention to form structure as shown in Figure 2: it keeps beam splitter 11, two catoptrons 13 and 15, polarizations to keep phase-modulators 12 and a polarization to keep delay line 14 to form by one 2 * 2 3dB polarization.Wherein the 3dB polarization keeps the two- port 9 and 10 of a side of beam splitter 11 all to can be used as the input and output side of Polarization Control scrambler; One of two-port of the opposite side of 3dB polarization maintenance beam splitter 11 connects polarization successively and keeps phase-modulator 12, catoptron 13; The homonymy another port polarization that then is linked in sequence keeps delay line 14, catoptron 15; A kind of slightly change but the identical structure of function is to keep delay line 14 and polarization to keep phase-modulator 12 (sequence independence) to be serially connected in same port simultaneously polarization, and the another port only connects a catoptron.During work; Light pulse keeps the port 9 of beam splitter 11 to get into polarization maintenance beam splitter 11 through polarization and is divided into two-way; One the tunnel through 14 time-delays of polarization maintenance delay line; Reflected by catoptron 15, another road reflects through catoptron 13 after polarization keeps phase-modulator 12 to carry out phase modulation (PM) again, and the two-way light pulse that reflects keeps 10 outputs of beam splitter 11 synthetic routed ports through polarization; Because of being polarization, all light paths keep light path, so identical by the polarization state of two pulses of 10 outputs.Keep phase-modulator 12 (sequence independence) to be serially connected in same port when polarization keeps delay line 14 and polarization, and the another port is when only connecting a catoptron, The above results is unaffected.Light pulse is imported from 10 ports, 9 ports output and come to the same thing during simultaneously as input and output with port 9 or 10.
Embodiment 3:
It is as shown in Figure 3 that the third of Polarization Control scrambler in the quantum key dispatching system of the present invention formed structure: it is made up of one 2 * 2 3dB beam splitter 18, two 90 degree rotation faraday's catoptrons 20 and 22, phase-modulators 19 and a delay line 21.Wherein the two- port 16 and 17 of a side of 3dB beam splitter 18 is respectively as the input and output side of Polarization Control scrambler; One of two-port of the opposite side of 3dB beam splitter 18 connects phase-modulator 19,90 degree rotation faraday catoptrons 20 successively, homonymy another port delay line 21, the 90 degree rotation faraday catoptrons 22 that then are linked in sequence.During work; Light pulse is divided into two-way through the port one 6 entering beam splitters 18 of beam splitter 18; One the tunnel through delay line 21 time-delays; Reflected by 90 degree rotation faraday catoptrons 22, another road reflects through 90 degree rotation faraday catoptrons 20 after phase-modulator 19 carries out phase modulation (PM) again, and the two-way light pulse that reflects is through 17 outputs of beam splitter 18 synthetic routed ports; Because of two light paths all also experience light path even number separately through 90 degree rotation faraday mirror reflects, so the polarization state of two pulses of output is identical thus.Light pulse is imported from 17 ports, 16 ports output and come to the same thing during simultaneously as input and output with port one 6 or 17.
Embodiment 4:
Another kind of structure slightly changes but the identical Polarization Control scrambler of function is as shown in Figure 4; Difference is phase-modulator 19, delay line 21,90 degree rotation faraday catoptrons 22 are linked in sequence on a port of coupling mechanism (wherein 19 and 21 order can reciprocity), only connects one 90 degree on the another port and rotates faraday's catoptron 20.During work; Light pulse is divided into two-way through the port one 6 entering beam splitters 18 of beam splitter 18; One the tunnel through phase-modulator 19 carry out phase modulation (PM) again through delay line 21 time-delay (sequence independence) after; Reflected by 90 degree rotation faraday catoptrons 22, another route 90 degree rotation faraday catoptrons 20 reflect, and the two-way light pulse that reflects is through 17 outputs of beam splitter 18 synthetic routed ports; Because of two light paths all also experience light path even number separately through 90 degree rotation faraday mirror reflects, so the polarization state of two pulses of output is identical thus.Light pulse is imported from 17 ports, 16 ports output and come to the same thing during simultaneously as input and output with port one 6 or 17.
Embodiment 5:
The 4th kind of Polarization Control scrambler in the quantum key dispatching system of the present invention to form structure as shown in Figure 6: it keeps variable beam splitter 25, two catoptrons 23 and 27, polarizations to keep phase-modulators 24 and a polarization to keep delay line 26 to form by one 2 * 2 polarization.Wherein polarization keep variable beam splitter 25 one of two ports of a side as the output terminal 28 of Polarization Control scrambler, the another port keeps delay line 26 to connect catoptron 27 through polarization; Polarization keeps one of two ports of opposite side of variable beam splitter 25 as the input end 29 of Polarization Control scrambler, and the another port keeps phase-modulator 24 to connect catoptron 23 through polarization.A kind of slightly change but the identical structure of function is to keep delay line 26 and polarization to keep phase-modulator 24 (sequence independence) to be serially connected in same port polarization, and the another port only connects a catoptron.During work, light pulse keeps the port 29 entering polarizations of variable beam splitter 25 to keep variable beam splitter 25 to be divided into two-way through polarization, and one the tunnel directly keeps the port 28 of variable beam splitter 25 directly to export from polarization; Another road keeps delay line 26 time-delays through polarization; Reflect by catoptron 27, keep variable beam splitter 25 through polarization again, keep phase-modulator 24 to carry out phase modulation (PM) through polarization again after catoptron 23 reflects; The light pulse that reflects keeps 28 outputs of the synthetic routed port of the variable beam splitter 25 and the light pulse of above-mentioned direct output through polarization; When beam splitting was carried out in light pulse, the control polarization kept the splitting ratio of variable beam splitter, made by two light pulse amplitudes of port 28 outputs equal; Because of being polarization, all light paths keep light path, so the polarization state of two light pulses of output is identical thus.Keep phase-modulator 24 (sequence independence) serial connection to go into same port when polarization keeps delay line 26 and polarization, and the another port is when only connecting a catoptron, The above results is unaffected.Pulse is imported from 28 ports, comes to the same thing during the output of 29 ports.
Embodiment 6:
The 5th kind of Polarization Control scrambler in the quantum key dispatching system of the present invention to form structure as shown in Figure 7: it is made up of one 2 * 2 variable beam splitter 32, two 90 degree rotation faraday's catoptrons 30 and 34, phase-modulators 31 and a delay line 33.One of two ports of one side of wherein variable beam splitter 32 are as the output terminal 35 of Polarization Control scrambler, and the another port connects 90 degree rotation faraday catoptrons 34 through delay line 33; One of two ports of the opposite side of variable beam splitter 32 are as the input end 36 of Polarization Control scrambler, and the another port connects 90 degree rotation faraday catoptrons 30 through phase-modulator 31.A kind of slightly change but the identical structure of function is that delay line 33 is connected in series into same port with phase-modulator 31 (sequence independence), and the another port only connects one 90 degree rotation faraday catoptron.During work, light pulse is divided into two-way through the variable beam splitter 32 of port 36 entering of variable beam splitter 32, and one the tunnel directly directly exports from the port 35 of variable beam splitter 32; Another road is through delay line 33 time-delays; Reflect by 90 degree rotation faraday catoptrons 34, pass through variable beam splitter 32 again, carry out phase modulation (PM) through phase-modulator 31 again after 90 degree rotation faraday catoptrons 30 reflect; The light pulse that reflects is through 35 outputs of the synthetic routed port of the variable beam splitter 32 and the light pulse of above-mentioned direct output; When beam splitting is carried out in light pulse, control the splitting ratio of variable beam splitter, make by two pulse heights of port 35 outputs equal; Because of two light paths all also experience light path even number separately through 90 degree rotation faraday mirror reflects, so the polarization state of two pulses of output is identical thus.When delay line 33 and phase-modulator 31 (sequence independence) are serially connected in same port, and the another port is when only connecting one 90 degree rotation faraday catoptron, and The above results is unaffected.Pulse is imported from 35 ports, comes to the same thing during the output of 36 ports.
Embodiment 7:
In the composition structure of five kinds of cited Polarization Control scramblers, phase-modulator all is movable to the identical phase modulation (PM) function of realization in the output light path in the foregoing description.For example: it is as shown in Figure 5 that a kind of phase-modulator is arranged in the Polarization Control scrambler of output light path, and it is made up of one 2 * 2 3dB beam splitter 18, two 90 degree rotation faraday's catoptrons 20 and 22, phase-modulators 19 and a delay line 21.One of two-port of a side of 3dB beam splitter 18 16 input ends wherein as the Polarization Control scrambler; The another port connects the output terminal 17 of phase-modulator 19 backs as the Polarization Control scrambler; One of two-port of the opposite side of 3dB beam splitter 18 connects 90 degree rotation faraday catoptrons 20, homonymy another port delay line 21, the 90 degree rotation faraday catoptrons 22 that then are linked in sequence.When described Polarization Control scrambler is used for receiving end; The above-mentioned phase-modulator that is positioned at output light path must move to the input light path before the pulse beam splitting, and for example: the phase-modulator 19 among the Polarization Control scrambler 49-5 must change into and is serially connected in port one 6 by being serially connected in port one 7.During work; Light pulse is divided into two-way through the port one 6 entering beam splitters 18 of beam splitter 18; One the tunnel through delay line 21 time-delays; Spend rotation faraday catoptrons 22 by 90 and reflect, another road 90 degree rotation faraday catoptrons 20 reflect, and the two-way light pulse that reflects is exported through port one 7 after beam splitter 18 synthetic route phase-modulators 19 carry out phase modulation (PM) respectively again; Because of two light paths all also experience light path even number separately through 90 degree rotation faraday mirror reflects, so the polarization state of two pulses of output is identical thus.When this Polarization Control scrambler was used for receiving end, the above-mentioned phase-modulator 19 that is arranged in output light path must move to the input light path before the pulse beam splitting, carries out phase modulation (PM) respectively by two light pulses of 19 pairs of inputs of phase-modulator.When above-mentioned phase-modulator is arranged in the output light path of transmitting terminal or is arranged in the input light path of receiving end the polarization retention performance is not required.
Embodiment 8:
In the quantum-key distribution device of the present invention reverse photon separation detection unit by: optical circulator 38 is formed with single-photon detector 37.Wherein, The incident port 39 of circulator is as the input port of reverse photon separation detection unit; The output port in the same way of the reverse photon separation detection unit of exit ports 40 conducts of circulator, and will be detected by circulator 38 separation and guiding single-photon detector 37 from the reverse photon of output port 40 incidents in the same way.As shown in Figure 8.During work; The forward photon of importing from the incident port 39 of circulator directly passes through, by exit ports 40 outputs of circulator, if photon is arranged from the reverse photon separation detection unit of port 40 reverse entering; Then circulator 38 will stop this photon from port 39 outputs; And this photon guiding single-photon detector 37 is detected, exist to have judged whether eavesdropping wooden horse photon, when using it for receiving end; A road of signal photon after the interference is detected by detector 27 equally, and testing result is used as quantum key information.
Embodiment 9:
The operating wavelength range of considering circulator and single-photon detector is limited; Possibly have wavelength and oppositely get into the Polarization Control scrambler away from the photon of circulator and single-photon detector, a kind of slightly different reverse photon separation detection unit is as shown in Figure 9: its difference is: input port 39 backs increase an optical band pass filter 41.Optical band pass filter 41 lets the interior light of system works wavelength coverage pass through during work, and the photon beyond the reverse photon separation detection unit operating wavelength range can not be passed through, the ability of the anti-eavesdropping of enhanced system.
Embodiment 10:
Utilize Polarization Control scrambler of the present invention, reverse photon separation detection unit and single-photon detector, light-pulse generator, can form a kind of typical quantum key dispatching system such as Figure 10 and show: wherein dispensing device is made up of single-photon source 42 (can be substituted by the simulation single-photon source that laser instrument and overdamp device are formed), Polarization Control scrambler of the present invention 43, reverse photon separation detection unit 44.Specifically be connected to: Polarization Control scrambler 43 (can be 49-1; 49-2; 49-3; 49-6, arbitrary in 49-7 or their change type) input end is connected with the output port of single-photon light source 42, and the output terminal of Polarization Control scrambler 43 (can be 50-1 with reverse photon separation detection unit 44 then; Arbitrary among the 50-2) input end connects, and the output port in the same way of reverse photon separation detection unit 44 is connected with quantum channel 45 outside being positioned at the place of safety as the signal output port of dispensing device.
The receiving trap of quantum key dispatching system (can be 49-1 by Polarization Control scrambler 47 of the present invention then; 49-2; 49-3; 49-6, arbitrary in 49-7 or their change type, wherein 49-3 or 49-7 are better), reverse photon separation detection unit 46 (can be among 50-1 and the 50-2 arbitrary) and single-photon detector 48 compositions.Specifically be connected to: quantum channel 45 gets into to receive in the place of safety and is connected with the input end of reverse photon separation detection unit 46; The output terminal in the same way of reverse photon separation detection unit 46 is connected with the input end of Polarization Control scrambler 47, and the output terminal of Polarization Control scrambler 47 then is connected with single-photon detector 48.
Quantum key distribution method is: the sender at first sends a single photon pulses by single-photon source 42, and (the actual pulse laser of overdamp that can adopt replaces; Require the contained photon number of each pulse to be not more than 1) entering Polarization Control scrambler 43; The Polarization Control scrambler carries out phase modulation (PM) with single photon pulses beam splitting, relative time delay and to one of them by the quantum key sharing agreement, and two light pulses that the output polarization attitude is identical get into quantum channels 45 and the unidirectional receiving traps of passing to through reverse photon separation detection unit 44 backs; After these two light pulses arrive receiving trap through quantum channel 45; Earlier through reverse photon separation detection unit 46 entering Polarization Control scramblers 47, Polarization Control scrambler 47 is once more with these two pulse beam splitting, make relative time delay and carry out phase modulation (PM) by the quantum key sharing agreement by the quantum key sharing agreement; One of interference signal of Polarization Control scrambler 47 outputs is directly delivered in the single-photon detector 48 and is detected (for reducing dark counts and the not interference of stem portion mutually; The detection here need be adopted the time gate pattern; Gate-control signal can be provided by the classical channel of transmitting terminal); Second detecting of the interference signal of Polarization Control scrambler 47 outputs through reverse photon separation detection unit separation back; According to testing result, transmission and the take over party's of above-mentioned two interference signals phase modulation recording and the information that both sides openly contrast, and, can obtain a quantum key according to the agreement of quantum key distribution protocol; Repeat said process, can set up the quantum key of the unconditional security of random length; Because the inner polarization that adopts of Polarization Control scrambler keeps light path or 90 degree faraday rotator mirrors to make two light pulse polarization states of output keep identical, thereby system has good antijamming capability.Use same port as input and output port to be simultaneously when sending and receiving device adopts the Polarization Control scrambler, need to increase beam splitting elements such as circulator, Y type beam splitter in the light path to separate the signal of input and output; When sending and receiving device adopts Polarization Control scrambler 49-6 with 49-7, to the light pulse beam splitting time, need control splitting ratio, make that two light pulse amplitudes of output are equal, with the bit error rate of the quantum key that reduces final generation.
Claims (5)
1. a Polarization Control scrambler (49-3,49-4,49-5) comprising:
2 * 2 3dB beam splitters (18); Be used for a light pulse of incident is beamed into two light pulses; Said 2 * 2 3dB beam splitters (18) have first port, second port, the 3rd port and the 4th port; Wherein first port and second port are positioned at a side of said 2 * 2 3dB beam splitters (18), and the 3rd port and the 4th port are positioned at the opposite side of said 2 * 2 3dB beam splitters (18);
Delay line (21) is used for one of said two light pulses are applied time-delay;
Phase-modulator (19) is used for light pulse is carried out phase modulation (PM) by the quantum key sharing agreement; And
The one 90 degree rotation faraday's catoptron (20) and the 2 90 degree rotation faraday's catoptron (22),
First port of wherein said 2 * 2 3dB beam splitters (18) is as the output terminal (17) of said Polarization Control scrambler (49-3,49-4,49-5), and second port of said 2 * 2 3dB beam splitters (18) is as the input end (16) of said Polarization Control scrambler (49-3,49-4,49-5);
The 3rd port of said 2 * 2 3dB beam splitters (18) links to each other with the one 90 degree rotation faraday's catoptron (20); And the 4th port of said 2 * 2 3dB beam splitters (18) and the 2 90 degree rotation faraday's catoptron (22) link to each other, and said 2 * 2 3dB beam splitters (18) will close Shu Weiyi Lu Guangcong output terminal (17) through two light pulses of the first and second 90 degree rotation faraday's catoptron (20,22) reflections and export;
Said delay line (21) is connected between the 4th port and said the 2 90 degree rotation faraday's catoptron (22) of said 2 * 2 3dB beam splitters (25); And
Said phase-modulator (19) is connected between the 3rd port and said the one 90 degree rotation faraday's catoptron (20) of said 2 * 2 3dB beam splitters (25); Perhaps be connected between the 4th port and said the 2 90 degree rotation faraday's catoptron (22) of said 2 * 2 3dB beam splitters (25), perhaps the output terminal (17) with said Polarization Control scrambler (49-3,49-4,49-5) links to each other.
2. Polarization Control scrambler as claimed in claim 1 (49-3,49-4,49-5) is characterized in that said Polarization Control scrambler (49-3,49-4,49-5) is used in the transmitting terminal of quantum key dispatching system.
3. Polarization Control scrambler as claimed in claim 2 (49-3,49-4,49-5) is characterized in that the transmitting terminal of said quantum key dispatching system also comprises:
Optical circulator (38); Be positioned at the output terminal (17) of said Polarization Control scrambler (49-3,49-4,49-5); Export from second port of optical circulator (38) from the light that first port of optical circulator (38) is imported; The 3rd port output from the light of second port of optical circulator (38) input from optical circulator (38), from said output terminal (17) output close light behind the bundle from first port input of optical circulator (38), and from second port output of optical circulator (38);
Single-photon detector (37) links to each other with the 3rd port of optical circulator (38), is used for the reverse input light from second port of optical circulator (38) is detected.
4. Polarization Control scrambler as claimed in claim 3 (49-3,49-4,49-5) is characterized in that the transmitting terminal of said quantum key dispatching system also comprises:
Optical band pass filter (41) links to each other with first port of optical circulator (38), is used for light output the carrying out optical band pass filtering behind the bundle of closing from said output terminal (17) output.
5. Polarization Control scrambler as claimed in claim 1 (49-3,49-4,49-5) is characterized in that said Polarization Control scrambler (49-3,49-4,49-5) is used in the receiving end of quantum key dispatching system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009101319808A CN101571612B (en) | 2004-02-02 | 2004-02-02 | Polarization controlling encoder |
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| CN2009101319808A CN101571612B (en) | 2004-02-02 | 2004-02-02 | Polarization controlling encoder |
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| CNA2004100139966A Division CN1651947A (en) | 2004-02-02 | 2004-02-02 | Polarization control coding method coder and quantum key distributing system |
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| CN101571612A CN101571612A (en) | 2009-11-04 |
| CN101571612B true CN101571612B (en) | 2012-12-26 |
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| TWI764840B (en) * | 2021-09-29 | 2022-05-11 | 國立中央大學 | Asymmetric adiabatic coupling polarization beam splitter element and its integrated optical waveguide spatial filter chip |
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