CN114745103A - Multi-user quantum key distribution system and method with annular structure - Google Patents
Multi-user quantum key distribution system and method with annular structure Download PDFInfo
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Abstract
The invention provides a multi-user quantum key distribution system and a method of a ring structure, wherein the system comprises a multi-user network based on the ring structure and a plurality of user terminals connected by a ring network; the invention combines the ring structure to the multi-user QKD network, realizes the loop protection and monitoring functions, realizes the many-to-many quantum key distribution of the optical loop structure, and ensures that the increase of users can not increase the insertion loss and reduce the key generation rate; the RRDPS protocol is adopted, so that the transmission efficiency is effectively increased; the structure adopted is simple, the operation is convenient, the transmission is stable, and the code rate is high.
Description
Technical Field
The invention relates to the quantum information and optical communication technology, in particular to a multi-user quantum key distribution system and method with a ring structure.
Background
Quantum Key Distribution (QKD) is an important field of Quantum communication research, and absolute security of Quantum communication is guaranteed based on Heisenberg's Uncertainty Principle and Quantum non-clonable Theorem (Quantum No-Cloning theory) in Quantum mechanics principles, and Quantum Key Distribution (QKD) in Quantum communication is more and more concerned because of the absolute security of Quantum communication.
QKD development to date has been proposed by a variety of protocols, the earliest being the BB84 protocol proposed in 1984 and the BBM92 protocol improved over the BB84 protocol in 1992, until recently the popular MDI-QKD protocol and TF-QKD protocol were compared.
The greatest problem faced by QKD development to date is how to combine quantum communication with classical communication, i.e. how to communicate using classical communication networks, so that it is not necessary to build a dedicated network for quantum communication, and it is possible to use existing optical fiber networks.
In the aspect of combining quantum communication and classical communication, a feasible solution is provided, and a plurality of structures of multi-user QKD networks are provided. Most multi-user QKD networks today employ optical node-based multi-user QKD networks. Currently, most of the solutions for multi-user QKD network based on wavelength division multiplexing technology are adopted, and the solutions generally adopt a single-wavelength light source: the pulse generated by the laser at the same time is a single wavelength pulse, so that only one user can be served by one communication practically, that is, only one-to-one communication can be achieved, which causes a problem that a plurality of users cannot work simultaneously. The key generation rate of the system in the current multi-user QKD network still suffers from the scale of the multi-user QKD network, and along with the increase of the number of users, the insertion loss of the whole network system is increased, the key generation rate of the multi-user network is reduced, and along with the defects of low photon utilization rate, insufficient stability and the like.
The prior patent is as follows: (CN105049195B) proposes a multi-user QKD network system based on sagnac loop and its key distribution method, which realizes one-to-N multi-user transmission. However, the method does not consider the problem that when the attenuated quantum signal meets the strong light signal, the quantum signal is interfered by the reverse rayleigh scattering of the strong light signal. And single-mode optical fiber transmission is adopted, and the transmission capacity of the system is limited.
The prior patent is as follows: (CN105515767A) provides a DPS-based multi-user QKD network system and a key distribution method thereof, which have the advantages of good stability, simple structure and low cost, and realize one-to-N multi-user transmission. But only one-to-N multi-user transmission is realized, and N-to-N multi-user transmission cannot be performed, which is not beneficial to the expansion of a user network.
Disclosure of Invention
The invention provides a multi-user quantum key distribution system with an annular structure, which is a multi-user network system, wherein a multi-user network is based on the annular structure, and a monitor in the network monitors in real time, so that the multi-user network system with the annular structure has the functions of loop protection and monitoring, and the efficiency of multi-user communication is greatly improved. Each user is relatively independent, the key generation rate of a single user is guaranteed to be stable, and the key generation rate cannot be reduced along with the increase of the users.
The invention further aims to provide a key distribution method of the multi-user quantum key distribution system with the ring structure.
In order to achieve the technical effects, the technical scheme of the invention is as follows:
a multi-user quantum key distribution system with a ring structure is characterized in that a multi-user network is based on the ring structure, and the multi-user network comprises a plurality of user terminals, optical add-drop multiplexers (ROADMs) with the number consistent with that of the user terminals, optical path selectors with the number consistent with that of the user terminals and a plurality of monitors;
the plurality of user terminals establish connection through a ring-shaped common channel; each user end is connected with the annular quantum channel through an optical add-drop multiplexer ROADM and an optical path selector;
the plurality of monitors are distributed in the annular quantum channel and are connected with the annular quantum channel; the monitors and the user side carry out information interaction through an annular public channel; the monitor can monitor the condition in the ring quantum channel and feed back to the user terminal in time.
Before the user side in the multi-user network needs to communicate, sending a communication application through a ring-shaped common channel and informing a receiving user side needing to communicate; each user side has a wavelength range which can be used for communication in the multi-user network, information interaction exists between the user sides, the wavelength range occupied by other user sides which are communicating can be known, the communication wavelength range of the user side is selected according to the information interaction, and the wavelength range used by other user sides is informed; the user side can know the condition of the annular quantum channel through the feedback of the monitor in the annular quantum channel, and the user side selects the optical path according to the condition of the annular quantum channel, so that the loop protection and monitoring function can be realized;
furthermore, the user side consists of an Alice sending end and a Bob receiving end; when the user terminal is in a sending state, namely an Alice sending terminal is selected, and the Alice sending terminal comprises a multi-wavelength pulse laser generating device, a phase modulator, a wavelength selector and an attenuator; the multi-wavelength pulse laser generating device, the phase modulator, the wavelength selection switch and the attenuator are sequentially connected;
when the user side is in a sending state, namely an Alice sending end works, the multi-wavelength pulse laser generating device generates a multi-wavelength pulse sequence, and a specific wavelength is selected after passing through the wavelength selection switch; the phase modulator respectively performs phase modulation on each pulse of the pulse sequence, and then the phase modulation passes through the attenuator;
further, when the user side is in a receiving state, namely, the user side selects a Bob receiving end, the Bob receiving end comprises a first beam splitter, a second beam splitter, a quantum random number random generator, a delayer, a first detector and a second detector; the laser pulse train reaches the upper and lower arm paths formed by the first beam splitter:
upper arm path: the pulse sequence transmitted by the first beam splitter is delayed by the delay device, and the delay size is determined by the quantum random number generator and reaches the second beam splitter.
Lower arm path: the pulse sequence reflected by the first beam splitter is directed to the second beam splitter.
And the upper arm path and the lower arm path interfere at the second beam splitter, and the detectors respectively respond according to interference results.
A multi-user quantum key distribution method of a ring structure comprises the following steps:
s1: multi-user network system initialization: the user side self-checks hardware facilities, determines information such as a system communication wavelength range and the like, checks whether each device normally operates or not, and sets initial conditions;
s2: and (3) testing system noise: randomly selecting two user terminals for communication, and testing the signal-to-noise ratio of a multi-user network system, wherein SNR is 10lg (PS/PN), PS is signal power, and PN is noise power; the noise of a coder, a decoder, a channel and a detector can influence the signal-to-noise ratio of the system during long-distance transmission, and the signal-to-noise ratio can not be used during communication due to the safety requirement to a certain degree;
s3: resource coordination: before the user terminal communicates, sending out a communication application through a ring-shaped public channel and informing a receiving user terminal which needs to communicate; each user side has a wavelength range which can be used for communication in the multi-user network, information interaction exists between the user sides, the wavelength range occupied by other user sides which are communicating can be known, the communication wavelength range of the user side is selected according to the information interaction, and the wavelength range used by other user sides is informed; the user side can know the condition of the annular quantum channel through the feedback of the monitor in the annular quantum channel, the user side selects the optical path according to the condition of the annular quantum channel, and the resource distribution and coordination processing are carried out among the user sides through the annular public channel;
s4: quantum information encoding and transmission: after the user terminal is selected as an Alice sending terminal, immediately driving a multi-wavelength pulse laser generating device to generate a multi-wavelength pulse sequence, and selecting a specific wavelength after passing through a wavelength selection switch; the phase modulator respectively performs phase modulation on each pulse in the pulse sequence, passes through the attenuator and then is sent to a channel;
s5: key screening and coding: the pulse is transmitted to a Bob receiving end of a corresponding receiving user end through a channel, the Bob receiving end records the response of the detector and records a corresponding pulse sequence responded by the detector, whether the pulse sequence is an effective forming code is judged, after the effective forming code is judged, the serial number of the corresponding pulse sequence is published through an annular public channel, and an Alice sending end calculates according to the pulse sequence published by the Bob to obtain an initial secret key;
s6: and (3) detection of the bit error rate: the Alice sender and Bob receiver repeat the above-mentioned S4 and S5 processes to obtain the total initial key. The Alice sending end calculates the error rate according to the obtained initial key so as to evaluate the information quantity obtained by Eve; if QBER is larger than 15%, the interception is possible, the communication is abandoned, and the communication is restarted;
s7: data coordination and privacy enhancement: the data coordination is the whole process of correcting errors of the screened data by utilizing a public classical channel, and after the data coordination, the data owned by the Alice sending terminal and the Bob receiving terminal are highly consistent, and the error rate is very low; the privacy enhancement is a technology for improving the data privacy through open communication, an eavesdropper Eve can steal part of data due to data coordination, and in order to improve the data privacy, an Alice sending end and a Bob receiving end carry out the privacy enhancement at the cost of reducing effective information, so that the information obtained by Eve is invalid, and the safety of the effective information is improved.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
1. the invention adopts an annular structure, the node failure does not affect the operation of the whole network, the monitor can monitor the transmission light path in real time and has the functions of seamless upgrade and capacity expansion; the reconfigurable optical add-drop multiplexer ROADM is used as a backbone ring node, the wavelength can be dynamically and flexibly dropped/inserted into a user side, a multi-user network with a ring structure and the user side form a multi-user quantum key distribution system, and a public optical fiber is maximally utilized, so that the cost of a special optical fiber is reduced, and long-distance transmission is facilitated; the increase of the number of users and the expansion of a coverage area are realized, and the network expansibility is good;
2. the RRDPS protocol is adopted, so that the safety of the system can be improved;
3. the system has the advantages of simple overall scheme, easy operation and higher implementability.
Drawings
FIG. 1 is a block diagram of the present invention;
fig. 2 is a user terminal according to the present invention;
fig. 3 shows an Alice sender n (n ═ 1,2,3.. m) at the customer end according to the present invention;
fig. 4 shows a Bob receiving end n (n ═ 1,2,3.. m) of the user end in accordance with the present invention.
FIG. 5 is a flow chart of the present invention.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;
it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1
As shown in fig. 1-4, a multi-user quantum key distribution system with a ring structure includes a multi-user network 1 ', a user end 2', an Alice sender n (n is 1,2,3.. m)3 ', and a Bob receiver n (n is 1,2,3.. m) 4', where the multi-user network 1 'includes a plurality of user ends 2', the user end 2 'is composed of an Alice sender 3' and a Bob receiver 4 ', and the user ends are connected to the multi-user network 1' through an optical add/drop multiplexer ROADM102, where:
the multi-user network 1' comprises an optical path selector 101, an optical add-drop multiplexer ROADM102 and a monitor 103;
the user end 2 'comprises a sending/receiving selector 201, an Alice sending end 3' and a Bob receiving end 4 ', and the user end 2' selects whether to carry out the operation of sending or receiving a signal according to the sending/receiving selector 201;
the Alice transmitting terminal 3' comprises a multi-wavelength pulse laser generating device 301, a wavelength selection switch 302, a phase modulator 303 and an attenuator 304;
bob receiving end 4' includes a first beam splitter 401, a second beam splitter 404, a quantum random number generator 402, a retarder 403, a first detector 405, and a second detector 406.
When the invention works, before the user terminal in the multi-user network needs to communicate, the user terminal sends out a communication application through the annular public channel and informs the receiving user terminal needing to communicate(ii) a Each user side has a wavelength range which can be used for communication in the multi-user network, information interaction exists between the user sides, the wavelength range occupied by other user sides which are communicating can be known, the communication wavelength range of the user side is selected according to the information interaction, and the wavelength range used by other user sides is informed; the user end can know the condition of the ring quantum channel through the feedback of the monitor 103 in the ring quantum channel, and the optical path selection made by the user end according to the condition of the ring quantum channel determines whether the laser pulse moves I in the ring quantum channel1Either go to I2When one link of the annular quantum channel fails, the other link can be selected to play a role in loop protection;
the user end 2 'immediately enters a sending state, namely, the sending end 3' is selected as the Alice sending end, and the multi-wavelength pulse laser generating device 301 sends out an L-length multi-wavelength laser pulse sequence
S1、S2、S3、...SL
Then, the corresponding wavelength is selected by the wavelength selection switch 302, each pulse of the pulse sequence is respectively phase-modulated by 0 or pi by the phase modulator 303, 0 represents bit 0, pi represents bit 1, and then attenuated by the attenuator 304 into a weak pulse sequence with an average photon number less than 1, where the encoded pulse sequence can be represented as:
the signal pulse with the corresponding wavelength is transmitted on the ring quantum channel through the optical add-drop multiplexer ROADM102 and the optical path selector 101, and then transmitted to the corresponding receiving user terminal through the optical add-drop multiplexer ROADM102, and the receiving user terminal enters a receiving state, namely, is selected as the Bob receiving terminal 4';
the sequence of laser pulses reaches the upper and lower arm paths formed by the first beam splitter 401:
upper arm path: the pulse train transmitted by the first beam splitter 401 is delayed by a delay 403, the magnitude of which is determined by the quantum random number generator 402, and reaches the second beam splitter 404.
Lower arm path: the pulse sequence reflected by the first beam splitter 401 is directed to the second beam splitter 404.
The upper arm path and the lower arm path interfere at the second beam splitter, and the detectors respectively respond according to the interference result.
The delay generated by the delay 403 is determined by the quantum random number generator 402, and r ' T (r ' is e {1, 2,3 …) is delayed for the upper arm path of Bob receiving end, and r ' is generated by the quantum random number generator 402; therefore, the pulse sequences of the upper arm path and the lower arm path are shifted from each other, the magnitude of the shift sequence is determined by the delay 403, the pulse sequence overlapping region of the upper arm path and the lower arm path interferes with the second beam splitter 404, and the interference result is determined by the delay and the phase modulation performed on the pulse sequences by the Alice transmitting end.
If exactly one photon is detected during the entire measurement and this photon originates from the interference of the ith pulse of the L pulse trains that have not done any operation and the jth pulse of the L pulse trains that have been delayed by r', wherein: j + i ± r', this is called a successful detection event.
And judging the obtained bit value by the Bob receiving end according to the response of the detector device: the first detector 405 is responsive to a pulse sequence with a phase difference of 0 and the second detector 406 is responsive to a pulse sequence with a phase difference of ± pi; when the first detector responds, the first detector is marked as bit 0, when the second detector responds, the second detector is marked as 1, the Bob receiving end obtains the screening key and records the serial numbers (i, j) corresponding to the pulses which are overlapped and generate interference, the Bob obtains the screening key according to the relative phase, otherwise, the Bob abandons the transmission process.
SB＝Si⊕Sj
The Bob receiving terminal publishes the sequence pair (i, j) through the annular public channel, and the Alice sending terminal can calculate to obtain the initial secret key according to the published pulse sequence information.
SA＝Si⊕Sj
Alice and Bob repeat N rounds of steps for generating an initial key, and then perform classical information post-processing procedures such as error correction and privacy amplification through a verification public channel to convert the N-bit initial key into a final key.
Example 2
The following describes the whole operation process of the present invention by taking the communication between the ue 1 and the ue 2 as an example.
As shown in fig. 1, before a ue 1 needs to perform communication, it sends a communication application through a ring common channel and informs a receiving ue 2 that needs to perform communication; each user side has a wavelength range which can be used for communication in the multi-user network, information interaction exists between the user sides, the wavelength range occupied by other user sides which are communicating can be known, the communication wavelength range of the user side is selected according to the information interaction, and the wavelength range used by other user sides is informed; the user end 1 can know the status of the ring quantum channel through the feedback of the monitor 103 in the ring quantum channel, and the optical path selection of the user end 1 according to the status of the ring quantum channel determines whether the laser pulse goes I or not in the ring quantum channel1Either go to I2When one link of the annular quantum channel fails, the other link can be selected to play a role in loop protection;
as shown in fig. 2 and fig. 3, the user end 1 immediately enters a transmitting state, i.e. it is selected as the Alice transmitting end 3', and the multi-wavelength pulse laser generating device 301 transmits the L-long multi-wavelength laser pulse sequence
S1、S2、S3、...SL
Then, the corresponding wavelength is selected by the wavelength selection switch 302, each pulse of the pulse sequence is respectively phase-modulated by 0 or pi by the phase modulator 303, 0 represents bit 0, pi represents bit 1, and then attenuated by the attenuator 304 into a weak pulse sequence with an average photon number less than 1, where the encoded pulse sequence can be represented as:
the signal pulse with the corresponding wavelength is transmitted on the ring quantum channel through the optical add-drop multiplexer ROADM102 and the optical path selector 101, and then transmitted to the corresponding receiving user terminal 2 through the optical add-drop multiplexer ROADM102, and the receiving user terminal 2 enters a receiving state, namely, is selected as a Bob receiving terminal 4';
as shown in fig. 4, the laser pulse train arrives at the upper and lower arm paths formed by the first beam splitter 401:
upper arm path: the pulse train transmitted by the first beam splitter 401 is delayed by a delay 403, the magnitude of which is determined by the quantum random number generator 402, and reaches the second beam splitter 404.
Lower arm path: the pulse sequence reflected by the first beam splitter 401 is directed to the second beam splitter 404.
The upper arm path and the lower arm path interfere at the second beam splitter, and the detectors respectively respond according to the interference result.
The delay generated by the delay 403 is determined by the quantum random number generator 402, and r ' T (r ' is e {1, 2,3 …) is delayed for the upper arm path of Bob receiving end, and r ' is generated by the quantum random number generator 402; therefore, the pulse sequences of the upper arm path and the lower arm path are shifted, the size of the shift sequence is determined by the delay 403, the pulse sequence overlapping region of the upper arm path and the lower arm path interferes with the second beam splitter 404, and the interference result is determined by the delay and the phase modulation performed on the pulse sequence by the Alice transmission terminal.
If exactly one photon is detected during the entire measurement and this photon originates from the interference of the ith pulse of the L pulse trains that have not done any operation and the jth pulse of the L pulse trains that have been delayed by r', wherein: j + i ± r', this is called a successful detection event.
And judging the obtained bit value by the Bob receiving end according to the response of the detector device: the first detector 405 is responsive to a pulse sequence with a phase difference of 0 and the second detector 406 is responsive to a pulse sequence with a phase difference of ± pi; when the first detector responds, the first detector is marked as bit 0, when the second detector responds, the second detector is marked as 1, the Bob receiving end obtains the screening key and records the serial numbers (i, j) corresponding to the pulses which are overlapped and generate interference, the Bob obtains the screening key according to the relative phase, otherwise, the Bob abandons the transmission process.
SB＝Si⊕Sj
The user end 2 publishes the sequence pair (i, j) through the ring public channel, and the user end 1 can calculate and obtain the initial key according to the published pulse sequence information.
SA＝Si⊕Sj
The user side 1 and the user side 2 repeat N rounds of steps for generating an initial key, and then the N-bit initial key is converted into a final key through classical information post-processing processes such as error correction, secret amplification and the like executed by verifying a public channel.
Example 3
As shown in fig. 5, a multi-user quantum key distribution method of a ring structure includes the following steps:
s1: multi-user network system initialization: the user side self-checks hardware facilities, determines information such as a system communication wavelength range and the like, checks whether each device normally operates or not, and sets initial conditions;
s2: and (3) testing system noise: randomly selecting two user terminals for communication, and testing the signal-to-noise ratio of a multi-user network system, wherein SNR is 10lg (PS/PN), PS is signal power, and PN is noise power; the noise of a coder, a decoder, a channel and a detector can influence the signal-to-noise ratio of the system during long-distance transmission, and the signal-to-noise ratio can not be used during communication due to the safety requirement to a certain degree;
s3: resource coordination: before the user terminal communicates, the user terminal sends out a communication application through a ring-shaped public channel and informs a receiving user terminal which needs to communicate; each user side has a wavelength range which can be used for communication in the multi-user network, information interaction exists between the user sides, the wavelength range occupied by other user sides which are communicating can be known, the communication wavelength range of the user side is selected according to the information interaction, and the wavelength range used by other user sides is informed; the user side can know the condition of the annular quantum channel through the feedback of the monitor in the annular quantum channel, the user side selects the optical path according to the condition of the annular quantum channel, and the resource distribution and coordination processing are carried out among the user sides through the annular public channel;
s4: quantum information encoding and transmission: after the user terminal is selected as an Alice sending terminal, immediately driving a multi-wavelength pulse laser generating device to generate a multi-wavelength pulse sequence, and selecting a specific wavelength after passing through a wavelength selection switch; the phase modulator respectively performs phase modulation on each pulse in the pulse sequence, passes through the attenuator and then is sent to a channel;
s5: key screening and coding: the pulse is transmitted to a Bob receiving end of a corresponding receiving user end through a channel, the Bob receiving end records the response of the detector and records a corresponding pulse sequence responded by the detector, whether the pulse sequence is an effective forming code is judged, after the effective forming code is judged, the serial number of the corresponding pulse sequence is published through an annular public channel, and an Alice sending end calculates according to the pulse sequence published by the Bob to obtain an initial secret key.
S6: and (3) detection of the bit error rate: the Alice sender and Bob receiver repeat the above-mentioned S4 and S5 processes to obtain the total initial key. The Alice sending end calculates the error rate according to the obtained initial key so as to evaluate the information quantity obtained by Eve; if QBER is larger than 15%, the interception is possible, the communication is abandoned, and the communication is restarted;
s7: data coordination and privacy enhancement: the data coordination is the whole process of correcting errors of the screened data by using a public classical channel, after the data coordination, the data owned by the Alice sending end and the Bob receiving end are highly consistent, and the error rate is very low; the privacy enhancement is a technology for improving the data privacy through open communication, an eavesdropper Eve possibly steals part of data due to data coordination, in order to improve the data privacy, an Alice sending end and a Bob receiving end carry out the privacy enhancement at the cost of reducing valid information, so that the information obtained by Eve is invalid, and the security of the valid information is improved.
1. The invention adopts an annular structure, the node failure does not affect the operation of the whole network, the monitor can monitor the transmission light path in real time and has the functions of seamless upgrade and capacity expansion; the reconfigurable optical add-drop multiplexer ROADM is used as a backbone ring node, the wavelength can be dynamically and flexibly dropped/inserted into a user side, a multi-user network with a ring structure and the user side form a multi-user quantum key distribution system, and a public optical fiber is maximally utilized, so that the cost of a special optical fiber is reduced, and long-distance transmission is facilitated; the increase of the number of users and the expansion of a coverage area are realized, and the network expansibility is good;
2. the RRDPS protocol is adopted, so that the safety of the system can be improved;
3. the system has simple integral scheme, easy operation and higher feasibility.
The same or similar reference numerals correspond to the same or similar parts;
the positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent;
it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A multi-user quantum key distribution system with a ring structure is characterized in that a multi-user network is based on the ring structure, and the multi-user network comprises a plurality of user terminals, optical add-drop multiplexers (ROADMs) with the number consistent with that of the user terminals, optical path selectors with the number consistent with that of the user terminals and a plurality of monitors;
the plurality of user terminals establish connection through a ring-shaped common channel; each user end is connected with the annular quantum channel through an optical add-drop multiplexer ROADM and an optical path selector;
the plurality of monitors are distributed in the annular quantum channel and are connected with the annular quantum channel; the monitors and the user side carry out information interaction through an annular public channel; the monitor can monitor the condition in the annular quantum channel and feed back the condition to the user side in time, and the information is shared between the user sides through the annular public channel;
before the user side in the multi-user network needs to communicate, sending a communication application through a ring-shaped common channel and informing a receiving user side needing to communicate; each user side has a wavelength range which can be used for communication in the multi-user network, information interaction exists between the user sides, the wavelength range occupied by other user sides which are communicating can be known, the communication wavelength range of the user side is selected according to the information interaction, and the wavelength range used by other user sides is informed; the user terminal can know the condition of the annular quantum channel through the feedback of the monitor in the annular quantum channel, and the user terminal selects the optical path according to the condition of the annular quantum channel to play the roles of loop protection and monitoring.
2. The system of claim 1, wherein the user side comprises an Alice transmitter and a Bob receiver; when the user terminal is in a sending state, namely an Alice sending terminal is selected, and the Alice sending terminal comprises a multi-wavelength pulse laser generating device, a phase modulator, a wavelength selector and an attenuator; the multi-wavelength pulse laser generating device, the phase modulator, the wavelength selection switch and the attenuator are sequentially connected;
when the user side is in a sending state, namely an Alice sending end works, the multi-wavelength pulse laser generating device generates a multi-wavelength pulse sequence, and a specific wavelength is selected after passing through the wavelength selection switch; the phase modulator respectively performs phase modulation on each pulse in the pulse sequence, and then the phase modulation is performed through the attenuator.
3. The system of claim 2, wherein when the user terminal is in a receiving state, i.e. selecting the Bob receiving terminal, it comprises a first beam splitter, a second beam splitter, a quantum random number random generator, a delayer, a first detector and a second detector; the laser pulse train reaches the upper and lower arm paths formed by the first beam splitter:
upper arm path: the pulse sequence transmitted by the first beam splitter generates delay through a delay device, and the delay size is determined by a quantum random number generator and reaches a second beam splitter;
lower arm path: the pulse sequence reflected by the first beam splitter is directly connected to the second beam splitter;
and the upper arm path and the lower arm path interfere at the second beam splitter, and the detectors respectively respond according to interference results.
4. The multi-user quantum key distribution system of claim 3, wherein the detector device is a single photon detector.
5. The system of claim 4, wherein the multi-user network has a ring public channel and a ring quantum channel, the ring public channel is responsible for transmitting other information, and the ring quantum channel is responsible for transmitting key information.
6. The multi-user quantum key distribution system of claim 5, wherein the multi-wavelength continuous laser generates different wavelength laser light meeting the requirements of multiple communication situations.
7. The multi-user quantum key distribution system of claim 6, wherein the Alice transmitter and the Bob receiver determine the key information according to the response of the detector and the quantum number random generator.
8. The multi-user quantum key distribution system of claim 7, wherein the first and second beam splitters operate efficiently over a range of wavelengths.
9. A key distribution method of the multi-user quantum key distribution system of the ring structure according to claim 8, comprising the steps of:
s1: multi-user network system initialization: the user side self-checks hardware facilities, determines information such as a system communication wavelength range and the like, checks whether each device normally operates or not, and sets initial conditions;
s2: and (3) testing system noise: randomly selecting two user terminals for communication, and testing the signal-to-noise ratio of a multi-user network system, wherein SNR is 10lg (PS/PN), PS is signal power, and PN is noise power; the noise of a coder, a decoder, a channel and a detector can influence the signal-to-noise ratio of the system during long-distance transmission, and the signal-to-noise ratio can not be used during communication due to the safety requirement to a certain degree;
s3: resource coordination: before the user terminal communicates, sending out a communication application through a ring-shaped public channel and informing a receiving user terminal which needs to communicate; each user side has a wavelength range which can be used for communication in the multi-user network, information interaction exists between the user sides, the wavelength range occupied by other user sides which are communicating can be known, the communication wavelength range of the user side is selected according to the information interaction, and the wavelength range used by other user sides is informed; the user side can know the condition of the annular quantum channel through the feedback of the monitor in the annular quantum channel, the user side selects the optical path according to the condition of the annular quantum channel, and the resource distribution and coordination processing are carried out among the user sides through the annular public channel;
s4: quantum information encoding and transmission: after the user terminal is selected as an Alice sending terminal, immediately driving a multi-wavelength pulse laser generating device to generate a multi-wavelength pulse sequence, and selecting a specific wavelength after passing through a wavelength selection switch; the phase modulator respectively performs phase modulation on each pulse in the pulse sequence, passes through the attenuator and then is sent to a channel;
s5: key screening and coding: the pulse is transmitted to a Bob receiving end of a corresponding receiving user end through a channel, the Bob receiving end records the response of the detector and the corresponding pulse sequence responded by the detector, judges whether the pulse sequence is an effective forming code or not, publishes the corresponding pulse sequence number through an annular public channel after judging that the pulse sequence is the effective forming code, and an Alice sending end calculates according to the pulse sequence published by the Bob to obtain an initial key;
s6: and (3) detection of the bit error rate: repeating the processes of S4 and S5 by the Alice sending terminal and the Bob receiving terminal to obtain a total initial secret key; the Alice sending end calculates the error rate according to the obtained initial key so as to evaluate the information quantity obtained by Eve; if QBER > threshold value theta, the communication is abandoned and the communication is restarted, wherein QBER is Nerr/Nsift, Nsift is the number of screened data, Nerr is the number of code value errors, and QBER is the number of code value errors;
s7: data coordination and privacy enhancement: the data coordination utilizes a public classical channel to carry out the whole process of error correction on the screened data, and after the data coordination, the data owned by the Alice sending terminal and the Bob receiving terminal are highly consistent, and the error rate is very low; because data coordination may cause an eavesdropper Eve to steal partial data, in order to improve the data confidentiality, an Alice sending end and a Bob receiving end perform confidentiality enhancement at the cost of reducing valid information, so that the information obtained by Eve is invalid, and the safety of the valid information is improved.
10. The method of claim 9, wherein the threshold θ is 15%.
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