CN218829962U - Multi-user MDI-QKD system - Google Patents
Multi-user MDI-QKD system Download PDFInfo
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- CN218829962U CN218829962U CN202222845913.6U CN202222845913U CN218829962U CN 218829962 U CN218829962 U CN 218829962U CN 202222845913 U CN202222845913 U CN 202222845913U CN 218829962 U CN218829962 U CN 218829962U
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Abstract
The utility model discloses a multi-user MDI-QKD system, which comprises a multi-user Alice end, a wavelength division multiplexing unit, a multi-user measuring end and a multi-user Bob end which are connected in sequence; the Alice terminal and the Bob terminal negotiate and determine a communication band; the Alice end and the Bob end respectively send out quantum signals of the wave band and send the quantum signals to the measuring end through the wavelength division multiplexing unit; the Alice end and the Bob end publish a basis vector selected by the prepared polarization state; the measuring end detects the quantum signal and records the response conditions of the first single-photon detector and the second single-photon detector; and the Alice terminal and the Bob terminal generate quantum keys according to the selected basis vectors and the response conditions. The utility model has simple structure, and can satisfy the condition that a plurality of users in the system simultaneously carry out QKD distribution; the number of detectors is reduced, the construction cost and complexity of the system are reduced to a greater extent, and the utilization rate of quantity sub-network resources can be improved.
Description
Technical Field
The utility model relates to a secret communication of quantum and optical communication field, concretely relates to multi-user MDI-QKD system.
Background
Quantum Key Distribution (QKD) theory is based on Quantum mechanics, has theoretical unconditional security, and realizes a process of secret sharing of Quantum keys among legitimate communication users (generally called Alice and Bob). In 1984, bennett and Brassard proposed the first QKD protocol, the BB84 protocol. However, in the actual QKD system, there is a risk that an eavesdropper (generally Eve) steals information due to factors such as environment and device imperfections, so researchers are always studying attack and defense of quantum communication, and try to find a method for solving Eve eavesdropping.
In 2012, a Measurement Device Independent (MDI) -QKD protocol proposed by Lo et al performs interferometric Measurement on quantum signals sent by both communication parties by an untrusted third party, and projects a Measurement result on a Bell state, thereby realizing the resistance to the attack of the Measurement Device. The published single photon source and the adaptive schemes proposed by Azuma and the like can effectively improve the code rate of MDI-QKD.
Four detectors are usually needed at the measuring end of the polarization modulation MDI-QKD protocol, but the detectors with better performance are higher in cost in practical application, particularly in a multi-user network based on WDM, a large number of single photon detectors are needed, and if the number of the detectors at each detecting end can be reduced, the cost consumption and the construction complexity of the whole system can be obviously reduced.
Thus, there is a need for improvements in the deficiencies of the existing QKD techniques.
SUMMERY OF THE UTILITY MODEL
The utility model aims at overcoming prior art's defect, in order to solve the network efficiency and the utilization ratio of the multi-point multi-user's quantum network, provide a multi-user MDI-QKD system and implementation method.
The utility model discloses the method is realized through following technical scheme:
a multi-user MDI-QKD system comprises a multi-user Alice end, a multi-user Bob end, a wavelength division multiplexing unit and a multi-user measuring end;
the multi-user Alice terminal, the wavelength division multiplexing unit, the multi-user measuring terminal and the multi-user Bob terminal are sequentially connected;
the multi-user Alice end comprises n Alice ends, the n Alice ends are respectively connected with the wavelength division multiplexing unit, and n is more than or equal to 2;
the multi-user Bob end comprises n Bob ends, the n Bob ends are respectively connected with the wavelength division multiplexing unit, and n is more than or equal to 2;
the multi-user Alice terminal and the multi-user Bob terminal are used for generating optical signals of various wave bands and sending the optical signals to the wavelength division multiplexing unit;
the wavelength division multiplexing unit is used for forwarding optical signals sent by a multi-user Alice terminal and a multi-user Bob terminal to a multi-user measuring terminal;
the multi-user measuring terminal is used for recording the response time point of the optical signal and publishing the response condition;
the multi-user Alice end and the multi-user Bob end respectively comprise a coherent light source, an intensity modulator, a polarization modulator and an optical attenuator which are connected in sequence;
the multi-user measuring end comprises m measuring ends, input ports of the m measuring ends are connected with output ports of the wavelength division multiplexing unit, and m is more than or equal to 2;
the multi-user measuring end comprises a beam splitter, a polarization beam splitter, a first single-photon detector and a second single-photon detector; the beam splitter is connected with the polarization beam splitter through an optical delay line, and the polarization beam splitter is respectively connected with the first single-photon detector and the second single-photon detector through the optical delay line.
Preferably, after the Alice and Bob negotiate and determine the communication band a through the MDI-QKD protocol, a coherent light source in any one of the Alice end and the Bob end sends out a coherent signal of the band a to enter the intensity modulator for state-induced modulation, so as to obtain a state-induced signal of the coherent signal; the polarization modulator randomly selects any one of BB84 polarization states of 0 degree, 45 degrees, 90 degrees and 135 degrees to perform polarization modulation on the attraction state signal to obtain a corresponding polarization state signal; and the polarization state signal enters an optical attenuator to be attenuated and then is sent to the measuring end through a wavelength division multiplexing unit to be measured.
Preferably, the attenuated signal is sent to the measuring end through the wavelength division multiplexing unit and then enters the beam splitter to be divided into two paths of signals, and the two paths of signals enter the polarization beam splitter through the optical delay line and then are divided into two paths of signals to enter the first single-photon detector and the second single-photon detector respectively.
Preferably, the Alice terminal and the Bob terminal publish preparation of the basis vectors selected by the polarization states, and the first single-photon detector and the second single-photon detector detect photon signals and record the time t1 or t2 when the first single-photon detector and the second single-photon detector detect photons.
Preferably, the band a ranges from: 1500nm to 1600nm.
Preferably, the BB84 polarization state is | H > °, | V > °, | + > and | - >.
The utility model has the advantages that:
the utility model adopts MDI-QKD protocol, which has immunity to the attack of measuring equipment, and the utility model also has the advantage of simple structure, and can satisfy that a plurality of users in the system simultaneously carry out QKD distribution; compared with the traditional MDI-QKD system, the utility model discloses reduced the use quantity of detector, reduced the construction cost and the complexity of system to a great extent to can greatly improve the utilization ratio of quantum network resource.
Drawings
FIG. 1 is an overall block diagram of the multi-user MDI-QKD system of the present invention;
fig. 2 is a structural diagram of each Alice terminal of the multi-user Alice terminal of the present invention;
FIG. 3 is a diagram of each of the multiple user Bob terminals of the present invention;
fig. 4 is a structural diagram of each measurement end in the multi-user measurement end of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments, but the scope of the present invention is not limited to the following specific embodiments.
A multi-user MDI-QKD system is disclosed, as shown in figure 1, the system comprises a multi-user Alice end, a multi-user Bob end, a wavelength division multiplexing unit and a multi-user measuring end; the multi-user Alice terminal, the wavelength division multiplexing unit, the multi-user measuring terminal and the multi-user Bob terminal are sequentially connected;
the multi-user Alice end comprises n Alice ends, the n Alice ends are respectively connected with the wavelength division multiplexing unit, and n is more than or equal to 2;
the multi-user Bob end comprises n Bob ends, the n Bob ends are respectively connected with the wavelength division multiplexing unit, and n is more than or equal to 2;
specifically, as shown in fig. 2 to fig. 3, each of the multi-user Alice end and the multi-user Bob end includes a coherent light source Laser, an intensity modulator IMA, a polarization modulator PMA, and an optical attenuator VOA, which are sequentially connected to each other;
the multi-user Alice terminal and the multi-user Bob terminal are used for generating optical signals of various wave bands and sending the optical signals to the wavelength division multiplexing unit;
the wavelength division multiplexing unit is used for forwarding optical signals sent by a multi-user Alice terminal and a multi-user Bob terminal to a multi-user measuring terminal;
the multi-user measuring terminal is used for recording and respectively publishing the time point of response and the response condition to the received signal to the multi-user Alice terminal and the multi-user Bob terminal.
The multi-user measuring end comprises m measuring ends, two ends of the m measuring ends are respectively connected with the wavelength division multiplexing unit, and m is more than or equal to 2;
as shown in fig. 4, the multi-user measuring end includes a beam splitter BS, a polarization beam splitter PBS, a first single-photon detector DV, and a second single-photon detector DH; the beam splitter BS is connected with the polarization beam splitter through an optical Delay line Delay, and the polarization beam splitter PBS is respectively connected with the first single-photon detector DV and the second single-photon detector DH through the optical Delay line Delay.
The utility model discloses a system theory of operation and process as follows:
after the Alice and the Bob determine a communication band A through an MDI-QKD protocol negotiation, a coherent light source Laser in any one of the Alice end and the Bob end sends out a coherent signal of the band A to enter the intensity modulator IMA for induced state modulation to obtain an induced state signal of the coherent signal;
specifically, coherent signals of different bands are obtained by adjusting the bands of signals sent by the coherent light source Laser, where the ranges of the bands are: 1500nm to 1600nm.
The PMA randomly selects any one BB84 polarization state of 0 degree, 45 degrees, 90 degrees and 135 degrees to perform polarization modulation on the attraction state signal to obtain a corresponding polarization state signal; and the polarization state signal enters the optical attenuator VOA for attenuation and then is sent to the measuring end for measurement through the wavelength division multiplexing unit.
The attenuated signals are sent to the measuring end through a wavelength division multiplexing unit and then enter a beam splitter BS to be divided into two paths of signals, the two paths of signals respectively enter a polarization beam splitter, are divided into two paths in the polarization beam splitter and then respectively enter a first single-photon detector DV and a second single-photon detector DH;
specifically, the Alice and Bob send signals of the same wave band to the wavelength division multiplexing unit, the corresponding measurement ends select the same wave band, and then the corresponding signals of Alice and Bob can be obtained from the wavelength division multiplexing unit, the signals of Alice and Bob interfere after entering the beam splitter BS in the measurement ends, and then the signals are divided into two paths from the beam splitter BS and enter the polarizing beam splitter PBS, wherein one path is output through a port 1 of the beam splitter BS and enters the polarizing beam splitter PBS, and the other path is output through a port 2 and enters the polarizing beam splitter PBS after passing through a Delay line Delay;
the Alice end and the Bob end publish and prepare the basis vectors selected by the polarization state, the first single-photon detector DV and the second single-photon detector DH detect photon signals, and record the time t1 or t2 when the first single-photon detector DV and the second single-photon detector DH detect photons; the time t1 and the time t2 respectively represent a time point when a signal is output from the port 1 and reaches the detector and a time point when the signal is output from the port 2 and reaches any one single photon detector through the Delay line Delay, wherein the time interval between the time t1 and the time t2 is delta t, the delta t represents the time required by the signal to pass through the Delay line Delay, and the delta t is used for distinguishing two paths of signals from the beam splitter;
and the Alice terminal and the Bob terminal form codes according to the published time point and the response condition.
If the two single-photon detectors detect photons, t1 and t2 both record time values, at the moment, the response caused by the two detectors in the scheme is equivalent to the response code forming of the four detectors at the same time in the MDI-QKD protocol, and the specific code forming condition is determined according to the measurement result and the polarization state sent by a user.
Specifically, the coding principle of the MDI-QKD protocol is as follows:
the utility model discloses a MDI-QKD agreement in principle based on the epr agreement of time reversal, realized the immunity to the measuring equipment attack. According to the MDI-QKD protocol, its BELL state measurement result | ψ + >、|ψ - >The correspondence between the encoding schemes 0 ° (H), 90 ° (V), 45 ° (+), and 135 ° (-) for both communications is shown in the following table:
TABLE 1
The code forming is that the Alice terminal and the Bob terminal transmit different polarization states under the Z base (namely H and V in Table 1) and the Alice terminal and the Bob terminal transmit the same or different polarization states under the X base (in Table 1, plus and minus).
In table 1, H corresponds to code 0, v corresponds to code 1, and then it can be known from table 1 that when the measurement results (i.e. the leftmost column) are these, it indicates that the polarization states sent by the Alice end and the Bob end are different, so that according to the polarization state of one end, it can be known what polarization state is sent by the other end. For example: if the Alice terminal is taken as a reference, H sent by the Alice terminal represents code value 0, and if the Bob terminal sends V code, the code value is required to be reversed by the Bob terminal because the Alice terminal is taken as the reference, namely, the Alice terminal and the Bob terminal both generate secret key 0.
Four single-photon detectors are needed in the BELL state measurement of the MDI-QKD protocol, the method is improved, a time sequence distribution mode is adopted to replace a space distribution mode, the using number of the detectors is reduced by half, and therefore the construction cost of the whole system is reduced.
In the MDI-QKD protocol, the code rate forming formula is as follows:
wherein Q rect (E rect ) Representing the total responsivity (total bit error rate) on the orthogonal basis,
represents the response ratio of a single light subsection on a square basis>
Table shows bit error rate, f (E), for a single-photon portion on a diagonal basis rect ) Indicating the efficiency of error correction.
The scheme reduces the using quantity of the detectors, and reduces the construction cost and complexity of the system to a greater extent.
The utility model discloses a MDI-QKD agreement, attack measuring equipment and have the immunity, compare with traditional MDI-QKD system, reduced the use quantity of detector, reduced the construction cost and the complexity of system to a great extent.
The utility model discloses a multi-user system has certain expansibility, can satisfy the function that a plurality of users carry out the QKD process simultaneously in the system, greatly improves quantum network resource utilization.
Variations and modifications to the above-described embodiments may occur to those skilled in the art, in light of the above teachings and teachings. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and modifications and changes to the present invention should fall within the protection scope of the claims of the present invention. In addition, although specific terms are used in the specification, the terms are used for convenience of description and do not limit the utility model in any way.
Claims (6)
1. A multi-user MDI-QKD system is characterized in that the system comprises a multi-user Alice end, a multi-user Bob end, a wavelength division multiplexing unit and a multi-user measuring end;
the multi-user Alice end, the wavelength division multiplexing unit, the multi-user measuring end and the multi-user Bob end are sequentially connected;
the multi-user Alice end comprises n Alice ends, the n Alice ends are respectively connected with the wavelength division multiplexing unit, and n is more than or equal to 2;
the multi-user Bob end comprises n Bob ends, the n Bob ends are respectively connected with the wavelength division multiplexing unit, and n is more than or equal to 2;
the multi-user Alice terminal and the multi-user Bob terminal are used for generating optical signals of various wave bands and sending the optical signals to the wavelength division multiplexing unit;
the wavelength division multiplexing unit is used for forwarding optical signals sent by a multi-user Alice terminal and a multi-user Bob terminal to a multi-user measuring terminal;
the multi-user measuring terminal is used for recording the response time point of the optical signal and publishing the response condition;
the multi-user Alice end and the multi-user Bob end respectively comprise a coherent light source, an intensity modulator, a polarization modulator and an optical attenuator which are connected in sequence;
the multi-user measuring end comprises m measuring ends, input ports of the m measuring ends are connected with output ports of the wavelength division multiplexing unit, and m is more than or equal to 2;
the multi-user measuring end comprises a beam splitter, a polarization beam splitter, a first single-photon detector and a second single-photon detector; the beam splitter is connected with the polarization beam splitter through an optical delay line, and the polarization beam splitter is respectively connected with the first single-photon detector and the second single-photon detector through the optical delay line.
2. The multi-user MDI-QKD system of claim 1, wherein a coherent light source in any one of the Alice end or the Bob end emits a coherent signal of a waveband A to enter the intensity modulator for the trap state modulation to obtain a trap state signal of the coherent signal; the polarization modulator randomly selects any one of BB84 polarization states of 0 degree, 45 degrees, 90 degrees and 135 degrees to perform polarization modulation on the attraction state signal to obtain a corresponding polarization state signal; and the polarization state signal enters an optical attenuator to be attenuated and then is sent to the measuring end through a wavelength division multiplexing unit to be measured.
3. The multi-user MDI-QKD system of claim 1, wherein the attenuated signal is sent to the measurement end via the wavelength division multiplexing unit and then enters the beam splitter to be divided into two signals, and the two signals enter the polarization beam splitter through the optical delay line and then are divided into two paths to enter the first single-photon detector and the second single-photon detector respectively.
4. The multi-user MDI-QKD system of claim 1, wherein the Alice and Bob terminals publish vectors selected for preparing polarization states, and the first and second single-photon detectors detect photon signals and record the times t1 or t2 at which the first and second single-photon detectors detect photons.
5. The multi-user MDI-QKD system of claim 2, wherein said band a ranges from: 1500nm to 1600nm.
6. A multi-user MDI-QKD system according to claim 2. Wherein the BB84 is in a polarization state of | H > °, | V > °, | + > and/or | - >.
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