CN100471105C - Quantum key multi-channel transmission method - Google Patents
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- CN100471105C CN100471105C CNB2005100232014A CN200510023201A CN100471105C CN 100471105 C CN100471105 C CN 100471105C CN B2005100232014 A CNB2005100232014 A CN B2005100232014A CN 200510023201 A CN200510023201 A CN 200510023201A CN 100471105 C CN100471105 C CN 100471105C
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Abstract
The invention relates to a quanta cryptographic key multi-channel transmission method. It comprises the following steps that the transmitting part is taking four kinds of polarization state modulation to the emitting light beam at random; the light beam is imaging at the image focal plane of the receiving part through the lens combination and free space between them; each of imaging light beam is passed the lens array to transform to parallel; after it is taking beam-splitting by the polarization light splitter, it is received by the analyzer with different polarization direction; after the receiving part is received the photon sequence, both side commonly discard the four multiplied by one channel photon sequence by the discussing in the common channel, and transform the rest photon sequence to the binary. The invention improves the transmission efficiency and the security of the cryptographic key transmission t at he same time.
Description
Technical field:
The present invention relates to the quantum key transmission field in the free space, particularly a kind of polarization encoder that utilizes carries out multichannel quantum key multi-channel transmission method.
Background technology:
Existing classical cryptographic communication is based on the safety of classical channel or to the finding the solution of certain mathematics difficult problem, its fail safe is relative.Along with the continuous development of computer science and technology, its fail safe is challenged day by day.The people that appear as of quantum cryptography communication provide a kind of brand-new and safe cryptographic communication system.Quantum cryptography communication is actual to be a process that quantum state distributes as cipher key carrier, it carries a bit information with a single photon and carries out password transmission, and Heisenberg's uncertainty principle, quantum that its fail safe depends in the quantum mechanics can not cloning theorem and quantum inseparabilities.What at present, the quantum-key distribution communication plan extensively adopted is BB84 agreement and B92 agreement.In the free space optical quantum cryptography communication, generally adopt the BB84 agreement.
The selected emission source of sender Alice is the laser pulse of single-photon source or process overdamp in the BB84 agreement, and the latter is approximately single-photon source.Consider from the fail safe aspect, number of photons in the light source pulse should be obeyed Poisson distribution, makes only to contain a single photon in each weak light pulse, and the umber of pulse that contains two or more photons is many more, the easy more shunting that is subjected to the potential third party is attacked, and the fail safe of its communication is just low more.Because a pulse only contains a such perfect condition of single photon and is difficult to realize, actual way is that to allow in the light beam each pulse contain two and two above number of photons probabilities very little, usually be controlled at about 5%, the laser after the decay just can reach in average each pulse and only contain 0.1 below the number of photons like this.For example, the breadboard quantum key communication experiment of U.S. Los Alamos has used similar attenuating device, at communication distance is in the laboratory experiment of 205m, average every pulse contains 0.7 of number of photons in the laser after the decay, this accounts for 34.8% of overall pulse number with regard to meaning the pulse that contains 1 photon, the pulse that contains 2 photons accounts for 12.3%, and the pulse that contains 3 photons accounts for 2.84%, and window pulse accounts for 50.06%; And be in the night experiment of 1km at communication distance, average every pulse contains 0.1 of number of photons, and the pulse that contains 2 and 2 above photons only accounts for＜and 6%.
From top numeral, the contained number of photons of average pulse in the experiment after the decay is controlled at very little scope, owing to exist in the existing single channel transmission course from the caused loss of atmospheric turbulance, and most of pulse all is the window pulse that does not contain photon, this has just seriously reduced the efficiency of transmission of quantum key distribution system, the intrinsic efficiency that in addition has certain quantum efficiency and agreement self algorithm at the single-photon detector of receiving terminal, the single photon efficiency of transmission lowly will directly influence whole system operation efficient in the transmission course.
Summary of the invention:
The object of the present invention is to provide a kind of quantum key multi-channel transmission method,, on the basis of BB84 protocol algorithm, utilize imaging optical path to carry out the multichannel transmission of quantum key in the free space to overcome above-mentioned the deficiencies in the prior art.
For achieving the above object, the invention provides a kind of quantum key multi-channel transmission method, may further comprise the steps: a. transmit leg carries out the modulation of 4 kinds of polarization states randomly to the emission light beam; B. light beam is through combination of lenses and the imaging on recipient's picture side focal plane of the free space between the two; C. make the light beam scioptics array of each imaging, be converted to collimated light beam, after the spectropolarimeter beam splitting, receive by analyzer with different polarization direction; D. after the recipient receives the photon sequence, discuss by overt channel, both sides abandon jointly and receive incomplete 4 * 1 passage photon sequences, and will remain the photon sequence and be converted into binary sequence by prior agreement.
Wherein, described method comprises that also binary sequence is carried out the password error correction to be amplified with maintaining secrecy.
Described emission light beam is the generally pulse laser in 1M～100M scope of operating frequency.This pulse laser is selected to filter on wave band, and the operation wavelength of wavelength in atmospheric window passed through.Pulse laser is through overdamping, and the average photon number that makes in the pulse to be contained satisfies Poisson distribution (n ≈ 0.1).
Further, the modulation of emission light polarization is realized by a polarizer.This polarizer has the inclined to one side aperture of rising of 4 * 1 arrays, above two get " * " polarisation based, below two get "+" polarisation based.The polarizer links to each other with computer, and the pseudo random sequence that is produced by relevant control circuits such as computers changes the polarization direction randomly to separately aperture in upper and lower two groups of bases.
The present invention improves on the basis of BB84 protocol algorithm, a kind of multichannel transmission means of utilizing imaging optical path to carry out quantum key in the free space is proposed, send bipartite photon transmission efficient in this greatly raising system of scheme, effectively solve the low problem of single photon efficiency of transmission in the traditional scheme.And significantly reduced the data volume of discussing at overt channel, also reduced the chance that the listener-in obtains information simultaneously.
The present invention is further illustrated below in conjunction with accompanying drawing and embodiment.
Description of drawings:
Fig. 1 is a transmitting terminal index path of the present invention.
The imaging optical path figure of Fig. 2 for transmitting in the space of the present invention.
Fig. 3 is an apparatus structure schematic diagram of the present invention.
Embodiment:
Relevant detailed description of the present invention and technology contents, existing as follows with regard to accompanying drawings:
At first please refer to Fig. 1, Fig. 1 is a transmitting terminal index path of the present invention.Owing to be the multichannel cipher key delivery of carrying out free space, for the sake of simplicity, the present invention is that example describes with the LASER Light Source array (4 * 1) of one dimension.The light that LASER Light Source 1 is sent among Fig. 1 passes collimating lens 4 and arrives the polarizers 5 after. interference filter 2 and laser attenuator assembly 3 are handled.Top two polarisation based of the polarizer (4 * 1) 5 are " * ", below two polarisation based be "+".The polarizer 5 back are information source array of apertures plates 6, and it is followed successively by A, B, C, D from top to bottom; The light that penetrates from information source array of apertures plate 6 passes diversing lens 7 arrival free spaces 8.
For sender Alice, LASER Light Source array 1 is positioned on the object space focal plane of lens 4, randomly they are carried out the modulation of 4 kinds of polarization states, the light beam that each point-source of light 1 sends is through combination of lenses and the free space between the two 8 imaging on recipient's picture side focal plane, and recipient Bob finishes and exchanges the reception that is shaped on the polarization information light beam.Behind imaging surface, make the light beam scioptics array of each imaging, be converted to collimated light beam, after the spectropolarimeter beam splitting, receive by analyzer with different polarization direction, the result notes by computer control system.In whole transport process,,, be equivalent in a spatial channel, carry out the transmission of 4 passages on the transmission channel of same space so each light beam does not disturb mutually owing to be incoherent light.After Bob receives the photon sequence, discuss by overt channel, residue photon sequence after both sides will discuss is converted into binary sequence by prior agreement, the initial password (raw key) that promptly can be used as quantum communications is preserved, then through processes such as the password error correction and the amplifications of maintaining secrecy, finally obtain the safe key that Alice and Bob both sides share, realized that the multichannel of quantum key in the free space transmits.
Suppose that then the imaging point on recipient's image planes is followed successively by D ＇, C ＇, B ＇ and A ＇ from top to bottom with the point-source of light of 4 * 1 arrays among Fig. 2 called after A, B, C and D successively from top to bottom.Herein, 44 analyzing detectors that play inclined to one side aperture and receiving terminal of transmitting terminal all are defined as upper and lower two groups (being designated as up and down), and the up group (A, B) in the transmit leg expansion light source is imaged on the down group (A ＇, B ＇) of recipient's image planes, and vice versa.Make the modulating polarization base of A, B point-source of light be " * ", the modulating polarization base of C, D point-source of light is "+".Determine to select the interior polarization state of base separately randomly after the polarisation based, A, B are selected randomly
" → ", " ↑ " polarization direction are selected randomly to C, D in the polarization direction.Each expansion light source with random polarization attitude is imaged on recipient's the image planes behind lens 7 and 9, is collimated light beam via thereafter microlens array effect again and arrives polarization beam apparatus.After the beam splitting, the photon stream that each bundle has the different polarization direction arrives analyzer and single photon numeration detector.
Because A, B are imaged on A ＇, B ＇, so the light that arrival A ＇, B ＇ are ordered has respectively
With
The random polarization attitude of direction, then get A ＇, B ＇ after the analyzer direction be respectively
With
Photon after the polarization beam apparatus beam splitting has passed through
The analyzer of direction and the single-photon detector that arrives thereafter then are designated as " 0 ", otherwise, if photon has passed through
The analyzer of direction and the single-photon detector that arrives thereafter then are designated as " 1 ".In like manner, C, D are imaged on C ＇, D ＇, and the light that arrives C ＇, D ＇ has the random polarization attitude of " → " and " ↑ " direction respectively, and the analyzer direction of getting behind C ＇, the D ＇ is respectively " → " and " ↑ ".Photon has passed through the analyzer of " → " direction and the single-photon detector that arrives thereafter then is designated as " 0 " after beam splitting, otherwise, if photon has passed through the analyzer of " ↑ " direction and the single-photon detector that arrives thereafter then is designated as " 1 ".
Ideally, a certain moment transmitting terminal A, B, C, D respectively send a single photon, and these group 4 * 1 photon sequences arrive receiving terminal A ＇, B ＇, C ＇, D ＇ and quilt detector thereafter smoothly and detect through a desirable transport process.In the practical operation, C ＇ and D ＇ end (up group) at a time can receive 3 or 3 above photons simultaneously, promptly take place " crosstalking ".So-called " crosstalking " problem is meant light that the transmitting terminal point-source of light launched through behind the lens, because diffraction, each light beam field pattern is Gaussian Profile when arriving picture side.If the receiving terminal imaging resolution is not high or system's pointing accuracy is not high, have photon during then the imaging of A ＇ or B ＇ end (down group) distributes and enter C ＇ and D ＇ end detector, because the polarisation based of A ＇, B ＇ and C ＇, D ＇ is non-orthogonal, make these photons have 50% probability to be detected by C ＇ and D ＇ end detector." crosstalking " to cause A ＇ and B ＇ end only to receive the photon of N＜2, and C ＇ and D ＇ end can receive N〉2 photon.In like manner, also may have the detector that photon enters A ＇ or B ＇ end during the imaging of C ＇ or D ＇ end distributes.The incomplete situation of this reception can cause the error code in the communicating pair transmission initial key process.Alice arranges with Bob: in up and down group any one group of polarization detector that is connected can not receive two photons (be Nup,
Or Nup, Ndown＜2) all should organize the photon sequence abandons.
Take place between C ＇ and D ＇ " crosstalking ", the photon that should arrive C ＇ might arrive D ＇, because the two polarisation based is identical, these photons can and be detected by analyzer.At this moment C ＇ does not receive photon, and D ＇ receives 2 photons.If 2 photons are identical in the polarization direction of delivery time, promptly one of them detector of D ＇ end receives 2 photons, then only its polarization direction as a result of need be write down to get final product, and does not need to distinguish the source of 2 photons; If 2 photons are in the polarization direction of delivery time difference, 2 detectors that are D ＇ end respectively receive a photon, then recipient's record result also has 50% probability identical with the primary photon sequence that transmit leg will send under the situation of not distinguishing the two source (being that photon is from C or D), and at this moment we preserve this group photon sequence and record in the initial key and go.For other probability is 50% mistake, and we can carry out relevant treatment by the error correction and the secret amplification process in communicating pair quantum key transmission course later stage.In like manner, for also having same analysis between A ＇ and the B ＇.For this class cross-interference issue, can improve the performance of system by the imaging resolution that improves receiving terminal with imitating.
If there is listener-in Eve in the channel, adopt the eavesdropping mode of intercepting/repeating transmission or shunting as Eve, then certain one group of 4 * 1 photon sequence that sends constantly can not be sent to receiving terminal completely, we are equal to the processing mode of " crosstalking " problem for the processing of the incomplete situation of this same reception, promptly agreement abandons this group photon sequence when overt channel is discussed, thereby has reduced the destruction that the eavesdropping of Eve brings to communication security to greatest extent.
For diameter is D
1Diversing lens, its emission light beam diffraction extended corner in free space is:
If transmitting range is d, the beam broadening that then arrives receiver lens is:
w≈D
1+d·2θ (2)
Propagation in atmosphere efficient is T in the transport process, if the diameter of receiver lens is D
2, how much losses during light beam process receiver lens are L
g:
Then distance loss in the transport process (Range loss) is L
R, often be written as the dB form in the experiment:
L
R＝-10log(T·L
g) (4)
Expection photon transfer rate is:
K＝RMTL
gη/2 (5)
Wherein R is the pulsed operation frequency of LASER Light Source, and M is the number of photons of average every pulse, and η is the total operating efficiency of detection system, and 1/2 is the intrinsic efficiency of BB84 agreement.Be about 10%～15% of initial key (raw key) through the key after the error correction and the amplification of maintaining secrecy.
Get atmosphere transmit in the less 650nm of diffraction diffusion be operation wavelength, diversing lens diameter D
1With receiver lens diameter D
2Value 30cm and 10cm are respectively at transmitting range d under the situation of 1km and 10km respectively, and getting T is 65%, the pulsed operation efficient of light source is 1MHz, and average photon number is 0.1, and the total operating efficiency η of detection system is 30%, then with various more than the above-mentioned parameter substitution, result of calculation sees table 1 for details.Can be seen by result of calculation, when the lens diameter of transmitting antenna and reception antenna is all got 30cm and all got 10cm, be under the situation of short distance (d=1km or 10km) when transmitting range, and it is all more satisfactory with expection photon transfer rate to pass the journey loss.Consider the pay(useful) load of system, get the two aperture diameter and all be set to 10cm.
The transmission efficiency and the loss of quantum key transport process see the following form:
See also Fig. 3 again, Fig. 3 is the schematic diagram of free space quantum key multi-channel transmission plan overall apparatus of the present invention, by among the figure as can be known, device comprises the device of transmitting terminal Alice and receiving terminal Bob respectively among the present invention program.Be followed successively by transmitting terminal, free space 8 and receiving end device among Fig. 3 from left to right.Wherein LASER Light Source 1 is the generally pulse laser in 1M～100M scope of operating frequency; Interference filter 2 (＜0.1nm), the pulse laser that light source 1 is sent is selected to filter on wave band, the operation wavelength of wavelength in atmospheric window passed through, reduce the loss of system; Attenuating plate 3, its effect are that paired pulses laser is decayed, thereby the average photon number that makes in the pulse to be contained satisfies Poisson distribution (n ≈ 0.1), reduces potential listener-in Eve photon stream is shunted the possibility of eavesdropping, improve the fail safe in the transport process; Also has collimating lens 4; The polarizer 5, the inclined to one side aperture of rising that 4 * 1 arrays are arranged, above two get " * " polarisation based, below two get "+" polarisation based, the polarizer links to each other with computer, the pseudo random sequence that is produced by relevant control circuits such as computers changes the polarization direction randomly to separately aperture, thereby 4 passage single photon streams by 4 * 1 arrays is carried out Polarization Modulation randomly in upper and lower two groups of bases; Information source array of apertures plate 6 is followed successively by A, B, C, D from top to bottom.Modulated polarised light incides the array board of being close to the polarizer, passes through from the aperture, becomes expansion light source outgoing forwards, can be considered the array extension light source of transmit leg; Transmitting antenna 7 (lens), array of apertures plate are placed on the object space focal plane of diversing lens, and the effect of the light process transmitting antenna that sends on the slave plate is horizontal light beam and incides free space 8; Reception antenna 9 (lens) is gained knowledge as can be known by illuminance, and the imaging effect that improve picture side promptly improves the efficient that picture side receives photon, generally adopts the large aperture small field of view; Filter 10, the light of the miscellaneous wavelength of elimination reduces the influence of background noise; Picture point array 11 is expressed as image point position, is followed successively by D ＇, C ＇, B ＇, A ＇ from top to bottom; Lens arra 12, be placed on the back of picture point array, distance between the two equals lenticular focal length, the light beam that makes each bundle have the different random polarization state incides spectropolarimeter 13 in horizontal direction by lenticule, the two-beam that two bundles of being told by spectrometer 12 have mutually orthogonal polarization direction is respectively by the corresponding single photon counting detector 15 of the 14 back arrival of the analyzing plate on its light path, and computer converts the photon sequence results of record to binary sequence.
Both sides carry out the overt channel discussion, abandon jointly according to algorithm of the present invention and receive incomplete 4 * 1 passage photon sequences, keep the photon sequence set that those meet about provisioning request, are converted to binary sequence, preserve as the initial key of sharing.So far, the transport process of both sides' performance sub-key transmission.Both sides know clearly to initial key by processes such as error correction, the amplifications of maintaining secrecy and examine then, and then obtain the quantum key of final safety.
Obviously, in the working unit time (being assumed to 1s), the number of photons that success is detected by Bob and preserves as initial key (raw key) in the 4 passage schemes is obviously than the number of photons that is detected in the single channel scheme many (being about 4 times).Be generalized to N * M scheme, can realize the N * M channel transfer of quantum key in the free space.Like this number of photons that success is transmitted under certain situation of operating time be exactly N * M that formerly single channel successfully transmits number of photons in the scheme doubly, thereby the efficiency of transmission of quantum key is greatly increased.
Above introduce, it only is preferred embodiment of the present invention, can not limit scope of the invention process with this, it is the variation that is equal to that the those skilled in the art in the present technique field are done according to the present invention, and those skilled in that art improvement, the variation known, all should still belong to the scope that patent of the present invention contains.
Claims (8)
1, a kind of quantum key multi-channel transmission method is characterized in that it may further comprise the steps: a. transmit leg carries out the modulation of 4 kinds of polarization states randomly to the emission light beam; B. light beam is through combination of lenses and the imaging on recipient's picture side focal plane of the free space between the two; C. make the light beam scioptics array of each imaging, be converted to collimated light beam, after the spectropolarimeter beam splitting, receive by analyzer with different polarization direction; D. after the recipient receives the photon sequence, discuss by overt channel, both sides abandon the photon sequence that 4 photons of 4 road photons that receive incomplete transmission arranged side by side are formed jointly, and will remain the photon sequence and be converted into binary sequence by prior agreement.
2, quantum key multi-channel transmission method as claimed in claim 1 is characterized in that: described method comprises that also step e. carries out the password error correction and the amplification of maintaining secrecy to binary sequence.
3, quantum key multi-channel transmission method as claimed in claim 1 is characterized in that: described emission light beam is the pulse laser of operating frequency in 1M～100M scope.
4, quantum key multi-channel transmission method as claimed in claim 3 is characterized in that: described pulse laser is selected to filter on wave band, and the operation wavelength of wavelength in atmospheric window passed through.
5, quantum key multi-channel transmission method as claimed in claim 3 is characterized in that: described pulse laser is through overdamping, and the average photon number that makes in the pulse to be contained satisfies Poisson distribution.
6, quantum key multi-channel transmission method as claimed in claim 1 is characterized in that: described step a is realized by a polarizer.
7, quantum key multi-channel transmission method as claimed in claim 6 is characterized in that: the described polarizer has the inclined to one side aperture of rising of 4 * 1 arrays, above two get " * " polarisation based, below two get "+" polarisation based.
8, quantum key multi-channel transmission method as claimed in claim 7 is characterized in that: the described polarizer links to each other with computer, and the pseudo random sequence that is produced by computer changes the polarization direction randomly to separately aperture in upper and lower two groups of bases.
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| RU2767290C1 (en) * | 2021-06-07 | 2022-03-17 | ОБЩЕСТВО С ОГРАНИЧЕННОЙ ОТВЕТСТВЕННОСТЬЮ "КуРэйт" (ООО "КуРэйт") | Device for recording optical signal from satellite (options) |
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| CN101998382B (en) * | 2009-08-18 | 2013-04-24 | 华为终端有限公司 | Network configuration method, equipment and system |
| CN102683868B (en) * | 2011-03-15 | 2015-02-04 | 深圳光启高等理工研究院 | Metamaterial imaging system |
| CN108199840B (en) * | 2018-02-05 | 2020-08-28 | 华北电力大学 | Quantum key distribution system |
| CN109495261B (en) * | 2018-12-29 | 2024-01-23 | 广东尤科泊得科技发展有限公司 | OAM measurement equipment independent quantum key distribution system and method for real-time tracking compensation |
| KR102173200B1 (en) * | 2019-09-06 | 2020-11-03 | (주)쎄트렉아이 | Payload apparatus for dual use of earth observation and quantum key distribution in satellite |
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| US5731790A (en) * | 1995-11-02 | 1998-03-24 | University Of Central Florida | Compact optical controller for phased array systems |
| US6289104B1 (en) * | 1998-08-07 | 2001-09-11 | Ilinois Institute Of Technology | Free-space quantum cryptography system |
| CN1384621A (en) * | 2002-06-21 | 2002-12-11 | 清华大学 | Speeding, efficient-raising and dilatating method for quantum cipher key distribution |
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| RU2767290C1 (en) * | 2021-06-07 | 2022-03-17 | ОБЩЕСТВО С ОГРАНИЧЕННОЙ ОТВЕТСТВЕННОСТЬЮ "КуРэйт" (ООО "КуРэйт") | Device for recording optical signal from satellite (options) |
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