CN113938277A - Double-field quantum key distribution system and communication distance improving method thereof - Google Patents
Double-field quantum key distribution system and communication distance improving method thereof Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/70—Photonic quantum communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0819—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s)
Abstract
The invention finds that the dense wavelength division multiplexer arranged in the prior art can not filter the noise related to the second Rayleigh scattering, and can also limit the system communication distance. Based on the discovery of the problem, a method for improving the communication distance of the dual-field quantum key distribution and a dual-field quantum key distribution system realized by the method are further disclosed. The pulse sequence output by the sending end is simply modulated, so that the occurrence frequency of strong reference optical signal pulses in the pulse sequence is reduced, secondary Rayleigh scattering noise and other noise in an optical fiber channel are reduced on the basis of not changing the parameters of the reference light and quantum optical signal pulses, and the communication distance of the system can be increased, which is extremely favorable for promoting the practical process of a double-field quantum key distribution system.
Description
Technical Field
The invention relates to the field of quantum communication, in particular to a method for increasing a double-field quantum key distribution communication distance and a double-field quantum key distribution system with the improved communication distance.
Background
Quantum communication is an emerging frontier discipline in which quantum physics and electronic informatics are deeply crossed and emerged, and quantum key distribution is one of important research directions in the field and is the direction with the fastest development and the highest engineering degree. Quantum key distribution has incomparable advantages compared with classical cryptography, and can provide unconditional and safe key transmission in theory, and the safety is guaranteed by quantum mechanics.
The double-field quantum key distribution is a new technology for realizing long-distance quantum communication at present, and because quantum signals are very fragile, the signal light is easily interfered by various noises in optical fibers, and the noises limit the transmission of the double-field quantum key distribution in a longer communication distance (a limit distance).
In the quantum channel of the dual-field quantum key distribution system, a Dense Wavelength Division Multiplexer (DWDM) is currently used to filter noise in the quantum channel to reduce interference of the noise on the quantum signal, for example, a DWDM with a central wavelength of 1550.12nm and a bandwidth of 100GHz is usually set in the quantum channel.
Disclosure of Invention
Through research on the conventional double-field quantum key distribution system, the invention discovers that the dense wavelength division multiplexer for eliminating the noise in the quantum channel in the prior art can not filter the noise related to the secondary Rayleigh scattering, and can also limit the communication distance of the system. Based on the discovery of the problem, the invention further discloses a method for improving the communication distance of the double-field quantum key distribution and a double-field quantum key distribution system realized thereby. The pulse sequence output by the sending end is simply modulated, so that the occurrence frequency of strong reference optical signal pulses in the pulse sequence is reduced, secondary Rayleigh scattering noise and other noise in an optical fiber channel are reduced on the basis of not changing the parameters of the reference light and quantum optical signal pulses, and the communication distance of the system can be increased, which is extremely favorable for promoting the practical process of a double-field quantum key distribution system.
Specifically, a first aspect of the present invention relates to a method for increasing a dual-field quantum key distribution communication distance, wherein, in a dual-field quantum key distribution system, quantum optical signal pulses and reference optical signal pulses are transmitted in a time division multiplexing manner by sharing an optical fiber channel; and the number of the first and second groups,
reducing a ratio of an average number of the reference optical signal pulses per unit time to an average number of the quantum optical signal pulses per unit time in the optical fiber channel without increasing a power of a single reference optical signal pulse.
Preferably, in the method of the present invention, the parameters of the individual reference optical signal pulses may not be changed.
Further, one or more pulse sequences having a modulation period T, comprising k, coexist in the fiber channel1A first pulse sub-sequence and k2A second pulse sub-sequence, k1Greater than or equal to 1, k2Greater than or equal to 1;
the first pulse subsequence includes quantum optical signal pulse and reference optical signal pulse at the same time and has a first modulation sub-period T1；
The second pulse subsequence only includes quantum optical signal pulses and has a second modulation sub-period T2。
Preferably, T ═ k1*T1+k2*T2And T is1＝T2。
Preferably, in the pulse sequence, the k is1A first sub-sequence of pulses being consecutive in time, and said k2The second pulse sub-sequence is consecutive in time.
Preferably, the first pulse subsequence comprises a segment of quantum optical signal pulses and a segment of reference optical signal pulses.
A second aspect of the present invention relates to a dual-field quantum key distribution system, which includes a receiving end and at least two transmitting ends;
the transmitting end is configured to generate a pulse sequence with a modulation period T and output the pulse sequence to a fiber channel, and the fiber channel is used for connecting the transmitting end and the receiving end;
the pulse sequence comprises k1A first pulse sub-sequence and k2A second pulse sequenceColumn, k1Greater than or equal to 1, k2Greater than or equal to 1;
the first pulse subsequence includes quantum optical signal pulse and reference optical signal pulse at the same time and has a first modulation sub-period T1(ii) a And the number of the first and second electrodes,
the second pulse subsequence only includes quantum optical signal pulses and has a second modulation sub-period T2。
Preferably, in the pulse sequence, the k is1A first sub-sequence of pulses being consecutive in time, and said k2The second pulse sub-sequence is consecutive in time.
Preferably, T ═ k1*T1+k2*T2And T is1＝T2。
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 illustrates a pulse sequence employed in the prior art for simultaneously transmitting a quantum optical signal and a reference optical signal;
FIG. 2 schematically illustrates a pulse sequence for a quantum optical signal and a reference optical signal in accordance with the present invention;
fig. 3 shows an example of a pulse sequence for a quantum optical signal and a reference optical signal according to the present invention.
Detailed Description
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are provided by way of illustration in order to fully convey the spirit of the invention to those skilled in the art to which the invention pertains. Accordingly, the present invention is not limited to the embodiments disclosed herein.
In a quantum channel of a dual-field quantum key distribution system, it is generally required to transmit a quantum optical signal and a reference optical signal at the same time, where the common-fiber transmission of the reference optical signal and the quantum optical signal with the same wavelength is often realized in a time division multiplexing manner. FIG. 1 shows a pulse sequence for simultaneously transmitting a quantum optical signal and a reference optical signal, which has a modulation period T, as used in the prior art1And each modulation period simultaneously comprises a strong reference optical signal pulse and a weak quantum optical signal pulse.
In such co-fiber transmission, scattering of strong reference light in the optical fiber inevitably causes noise, and its sources include raman scattering, brillouin scattering, rayleigh scattering, and the like.
Research shows that in the existing dual-field quantum key distribution system, the dense wavelength division multiplexer can actually only filter the noise part which is caused by Raman scattering and Brillouin scattering and is inconsistent with the wavelength of a quantum optical signal, while the noise caused by Rayleigh scattering has the same wavelength as the quantum optical signal and is uniformly distributed in a time domain, so that the noise part is difficult to distinguish from the incident quantum optical signal in the time domain and cannot be filtered by the dense wavelength division multiplexer. Further, the rayleigh scattered light includes forward rayleigh scattered light and backward rayleigh scattered light, the forward rayleigh scattered light overlaps with the quantum optical signal pulse and therefore has no influence thereon, and the backward rayleigh scattered light can generate secondary rayleigh scattering at any time, and since the secondary rayleigh scattering is uniformly distributed in the time domain, the secondary rayleigh scattered light leaks into the quantum optical signal to increase dark count, which will limit realization of communication at a longer distance in the dual-field quantum key distribution system, because the long-distance (limit distance) dual-field quantum key distribution system is very sensitive to noise.
On the basis of finding that the existing double-field quantum key distribution system still has the factors which can limit the communication distance, the invention further obtains the solution idea that the communication distance of the double-field quantum key distribution system can be further improved by reducing the secondary Rayleigh scattering noise of the strong reference light signal.
A dual-field quantum key distribution system typically includes a receiving end and at least one pair of transmitting ends. The sending end can output the quantum optical signal pulse and the reference optical signal pulse to the same optical fiber channel in a pulse sequence mode in a time division multiplexing mode so as to transmit the quantum optical signal pulse and the reference optical signal pulse to the receiving end. Wherein the quantum optical signal pulse and the reference optical signal pulse have the same wavelength.
After receiving the pulse sequence including the quantum optical signal pulse and the reference optical signal pulse, the receiving end can use the reference optical signal pulse to realize phase estimation and compensation, and use the quantum optical signal pulse to realize the quantum key distribution process.
Based on the discovery that the existence of secondary rayleigh scattering noise is still the limiting factor of the communication distance in the existing double-field quantum key distribution system, the invention specifically provides a method for reducing the secondary rayleigh scattering noise caused by strong reference optical signal pulses in an optical fiber channel by modulating a pulse sequence output by a sending end, so as to improve the communication distance of the double-field quantum key distribution system, and the obtained double-field quantum key distribution system.
Fig. 2 schematically shows a pulse sequence for improving the communication distance of dual-field quantum key distribution according to the present invention, which is to be generated by a transmitting end and output into a fiber channel connected to a receiving end.
As shown in fig. 2, k may be included in the pulse sequence according to the present invention1A first pulse sub-sequence and k2A second pulse subsequence, wherein k1And k2Are all greater than or equal to 1.
By modulating the pulse sequence, the first pulse subsequence simultaneously includes quantum optical signal pulses and reference optical signal pulses, and the second pulse subsequence only includes quantum optical signal pulses, so that, compared with the prior art, the ratio of the average number of the reference optical signal pulses in the optical fiber channel in a unit time to the average number of the quantum optical signal pulses in the optical fiber channel in a unit time can be reduced, or the occurrence frequency of the reference optical signal pulses can be reduced on the basis of keeping the occurrence frequency of the quantum optical signals in the optical fiber channel unchanged.
Therefore, the generation frequency of the secondary Rayleigh scattering noise in the optical fiber channel can be reduced on the basis of not changing the parameters of the single reference optical signal pulse and/or the quantum optical signal pulse, and accordingly the dark count in the optical fiber channel is reduced, so that the communication distance of the dual-field quantum key distribution system is allowed to be improved. Obviously, in the method of the present invention, only the occurrence frequency of the reference optical signal pulse needs to be changed, and the parameters of the pulse itself need not to be changed, which will reduce the modification requirements of the hardware and software system of the existing dual-field quantum key distribution system for implementing the method of the present invention, and is easy to implement on the basis of the existing system.
Further, according to the invention, the first pulse sub-sequence may be modulated to have a first modulation sub-period T1Modulating the second pulse subsequence to have a second modulation sub-period T2And T ═ k1*T1+k2*T2，T1＝T2。
In a preferred example, such as that shown in fig. 2, the first pulse subsequence may include a segment of quantum optical signal pulses and a segment of reference optical signal pulses.
In a preferred example, such as shown in fig. 2, the first plurality of pulse sub-sequences in one pulse sequence are consecutive in time, and the second plurality of pulse sub-sequences are also consecutive in time. Thereby, it may be allowed to reduce interference of the secondary rayleigh scattering noise on the quantum optical signal pulse.
Fig. 3 shows an example of a pulse sequence for improving the two-field quantum key distribution communication distance according to the present invention.
As shown in FIG. 3, the pulse sequence transmitted by the dual-field quantum key distribution system to the fiber channel has a modulation period T of 50 μ s, wherein the pulse sequence includes a first modulation sub-period T1And having a second modulation sub-period T2Of the first pulse sub-sequence.
In the pulse train, the first pulseThe sub-sequence comprises a strong reference optical signal pulse and a weak quantum optical signal pulse, and the number k of the reference optical signal pulses and the weak quantum optical signal pulses 110, first modulation sub-period T1Is 1. mu.s. The second pulse subsequence only contains a weak quantum optical signal pulse, and the number k of the weak quantum optical signal pulses 240, second modulation sub-period T2Is 1. mu.s.
The pulse sequence shown in fig. 3 is obtained by modulation at the transmitting end, and is used for transmitting the quantum optical signal pulse and the reference optical signal pulse to the receiving end through the optical fiber channel, so that the number (or the occurrence frequency) of the strong reference optical signal pulse in the optical fiber channel in the same time is reduced while the receiving end is ensured to realize estimation and compensation of the phase in real time, and the secondary rayleigh scattering noise in the optical fiber channel is reduced, thereby the dark count in the system is reduced, the limitation of the secondary rayleigh scattering noise on the communication distance of the system is eliminated, and the communication distance is further improved. Meanwhile, the invention can also reduce other noises caused by the reference optical signal pulse in the optical fiber channel, and is beneficial to promoting the practical process of the double-field quantum key distribution system.
Although the present invention has been described in connection with the embodiments illustrated in the accompanying drawings, it will be understood by those skilled in the art that the embodiments described above are merely exemplary for illustrating the principles of the present invention and are not intended to limit the scope of the present invention, and that various combinations, modifications and equivalents of the above-described embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention.
Claims (9)
1. A method for improving the distribution communication distance of a double-field quantum key is disclosed, wherein, in a double-field quantum key distribution system, quantum optical signal pulses and reference optical signal pulses are transmitted by sharing an optical fiber channel in a time division multiplexing mode; and the number of the first and second groups,
reducing a ratio of an average number of the reference optical signal pulses per unit time to an average number of the quantum optical signal pulses per unit time in the optical fiber channel without increasing a power of a single reference optical signal pulse.
2. The method of claim 1, wherein parameters of a single reference optical signal pulse are not changed.
3. The method of claim 1, wherein one or more pulse trains having a modulation period T comprising k are present simultaneously in the fibre channel1A first pulse sub-sequence and k2A second pulse sub-sequence, k1Greater than or equal to 1, k2Greater than or equal to 1;
the first pulse subsequence includes quantum optical signal pulse and reference optical signal pulse at the same time and has a first modulation sub-period T1；
The second pulse subsequence only includes quantum optical signal pulses and has a second modulation sub-period T2。
4. A method as claimed in claim 3, wherein T ═ k1*T1+k2*T2And T is1＝T2。
5. The method of claim 3, wherein, in the pulse sequence, the k is1A first sub-sequence of pulses being consecutive in time, and said k2The second pulse sub-sequence is consecutive in time.
6. The method of claim 3, wherein the first pulse subsequence comprises a segment of quantum optical signal pulses and a segment of reference optical signal pulses.
7. A double-field quantum key distribution system comprises a receiving end and at least two transmitting ends;
the transmitting end is configured to generate a pulse sequence with a modulation period T and output the pulse sequence to a fiber channel, and the fiber channel is used for connecting the transmitting end and the receiving end;
the pulse sequence comprises k1A first pulseSequence sum k2A second pulse sub-sequence, k1Greater than or equal to 1, k2Greater than or equal to 1;
the first pulse subsequence includes quantum optical signal pulse and reference optical signal pulse at the same time and has a first modulation sub-period T1(ii) a And the number of the first and second electrodes,
the second pulse subsequence only includes quantum optical signal pulses and has a second modulation sub-period T2。
8. The dual-field quantum key distribution system of claim 7, wherein in the pulse sequence, the k is1A first sub-sequence of pulses being consecutive in time, and said k2The second pulse sub-sequence is consecutive in time.
9. The dual-field quantum key distribution system of claim 7, wherein T ═ k1*T1+k2*T2And T is1＝T2。
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114448621A (en) * | 2022-01-21 | 2022-05-06 | 西安电子科技大学 | Multi-party double-field quantum key distribution protocol implementation method and system |
| CN114448621B (en) * | 2022-01-21 | 2024-04-23 | 西安电子科技大学 | Multi-party double-field quantum key distribution protocol implementation method and system |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109194470A (en) * | 2018-09-07 | 2019-01-11 | 中南大学 | High-efficiency and continuous variable quantum key delivering method |
| CN110445610A (en) * | 2019-08-26 | 2019-11-12 | 上海循态信息科技有限公司 | Polarization method for tracing, system and the medium of continuous variable quantum key distribution system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109194470A (en) * | 2018-09-07 | 2019-01-11 | 中南大学 | High-efficiency and continuous variable quantum key delivering method |
| CN110445610A (en) * | 2019-08-26 | 2019-11-12 | 上海循态信息科技有限公司 | Polarization method for tracing, system and the medium of continuous variable quantum key distribution system |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114448621A (en) * | 2022-01-21 | 2022-05-06 | 西安电子科技大学 | Multi-party double-field quantum key distribution protocol implementation method and system |
| CN114448621B (en) * | 2022-01-21 | 2024-04-23 | 西安电子科技大学 | Multi-party double-field quantum key distribution protocol implementation method and system |
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