CN210490895U - Quantum key distribution system of phase and polarization composite coding - Google Patents
Quantum key distribution system of phase and polarization composite coding Download PDFInfo
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Abstract
The quantum key distribution system comprises a sending end and a receiving end, wherein the sending end comprises a laser, an intensity modulator, a phase coding module, a polarization coding module and an attenuator which are sequentially connected, the receiving end comprises a deviation rectifying module, a polarization decoding module, a phase decoding module and a single photon detector which are sequentially connected, and the sending end and the receiving end are connected through the attenuator and the deviation rectifying module. Compared with the prior art, the utility model discloses a carry out phase place and polarization composite coding to single photon bit, can improve the efficiency of agreement, adopt the mode of selecting the base partially can promote efficiency to 4 times of original agreement; the polarization encoding and decoding structure is simple, the performance is stable, the complexity of the system is reduced, and the safety of the system is improved; by adopting a phase and polarization composite coding mode, under the condition that one mode is down, the system can work in another mode, and the working stability of the system is provided to a certain extent.
Description
Technical Field
The utility model relates to a quantum polarization coding technical field, in particular to quantum key distribution system of phase place and polarization composite coding.
Background
Quantum Key Distribution (QKD) can ensure unconditional and secure key distribution for both remote communication parties, and the information theoretical security is ensured by the fundamental principle of Quantum mechanics. After more than 30 years of research and development, quantum key distribution has been gradually put into practical use. The BB84QKD protocol is the most mature in the current technology and the most widely applied, the typical BB84 protocol only encodes bit information on one dimension of a single photon, such as phase, polarization or frequency, and the single photon is subjected to extended encoding, that is, the bit information is encoded on multiple dimensions of the single photon, so that the single photon carries multi-bit information, and the dimensions are decoded respectively, so that the safety code rate can be improved, and the overall efficiency of the system is improved. However, the key generation rate of the current QKD system is low and cannot meet the encryption requirements of the existing conventional optical fiber communication.
SUMMERY OF THE UTILITY MODEL
To prior art defect above, the utility model provides a phase place and polarization composite coding's quantum key distribution system as follows:
the technical scheme of the utility model is realized like this:
the quantum key distribution system comprises a sending end and a receiving end, wherein the sending end comprises a laser, an intensity modulator, a phase coding module, a polarization coding module and an attenuator which are sequentially connected, the receiving end comprises a deviation rectifying module, a polarization decoding module, a phase decoding module and a single photon detector which are sequentially connected, and the sending end and the receiving end are connected through the attenuator and the deviation rectifying module.
Preferably, the phase encoding module is an unequal arm MZ interferometer, the polarization encoding module includes an encoding circulator, an encoding phase modulator and an encoding faraday rotating mirror which are connected in sequence, an optical outlet of the unequal arm MZ interferometer is connected with one port of the encoding circulator, two ports of the encoding circulator are connected with the encoding phase modulator, and three ports of the encoding circulator are connected with the attenuator; the polarization decoding module comprises a decoding circulator, a decoding phase modulator and a decoding Faraday rotating mirror, wherein one port of the decoding circulator is connected with a deviation rectifying module, the two ports of the decoding circulator are sequentially connected with the decoding phase modulator and the decoding Faraday rotating mirror, the phase decoding module comprises a polarization beam splitter and two unequal arm MZ interferometers, the input ends of the two unequal arm MZ interferometers are connected with three ports of the decoding circulator through the polarization beam splitter, and the output ends of the two unequal arm MZ interferometers are connected with two single photon detectors.
Preferably, the phase encoding module is an unequal arm MZ interferometer, the polarization encoding module includes an encoding circulator, an encoding phase modulator and an encoding faraday rotating mirror which are connected in sequence, an optical outlet of the unequal arm MZ interferometer is connected with one port of the encoding circulator, two ports of the encoding circulator are connected with the encoding phase modulator, and three ports of the encoding circulator are connected with the attenuator; the polarization decoding module comprises a decoding circulator, a decoding phase modulator and a decoding Faraday rotating mirror, wherein a port of the decoding circulator is connected with a deviation rectifying module, two ports of the decoding circulator are sequentially connected with the decoding phase modulator and the decoding Faraday rotating mirror, the phase decoding module comprises a polarization beam splitter and an unequal arm MZ interferometer, the input end of the unequal arm MZ interferometer is connected with one end of the polarization beam splitter through a long arm optical fiber and a short arm optical fiber respectively, a delay line is arranged on the long arm optical fiber, the other end of the polarization beam splitter is connected with three ports of the encoding circulator, and the output end of the unequal arm MZ interferometer is connected with two paths of single photon detectors.
Compared with the prior art, the utility model discloses there is following beneficial effect:
1. the utility model discloses a phase place and polarization composite coding's quantum key distribution system, through carrying out phase place and polarization composite coding to the single photon bit, can improve the efficiency of agreement, adopt the mode of selecting the base partially can promote efficiency to 4 times of original agreement;
2. the polarization encoding and decoding structure is simple, the performance is stable, and compared with the traditional multi-laser encoding and passive selective base decoding, the side channel quantum state preparation and measurement information leakage are avoided, so that the complexity of the system is reduced, and the safety of the system is improved;
3. the decoding mode that the receiving end carries out polarization first and then carries out phase is adopted, because the polarization compensation is carried out before the polarization decoding, the polarization state is stable during the phase decoding, the MZI can be directly used, and the stable interference can be realized, so that the phase decoding is very stable, and the MZI has a simple structure and is easy to manufacture;
4. by adopting a phase and polarization composite coding mode, under the condition that one mode is down, the system can work in another mode, and the working stability of the system is provided to a certain extent.
Drawings
Fig. 1 is a schematic block diagram of a phase and polarization composite encoded quantum key distribution system according to the present invention;
fig. 2 is a schematic block diagram of a first embodiment of the present invention;
fig. 3 is a schematic block diagram of a second embodiment of the present invention.
In the figure: the device comprises a sending end 100, a laser 110, an intensity modulator 120, a phase coding module 130, a polarization coding module 140, a coding circulator 141, a coding phase modulator 142, a coding Faraday rotator mirror 143, an attenuator 150, a receiving end 200, a deviation rectifying module 210, a polarization decoding module 220, a decoding circulator 221, a decoding phase modulator 222, a decoding Faraday rotator mirror 223, a phase decoding module 230, a polarization beam splitter 231 and a single photon detector 240.
Detailed Description
The present invention will be described more fully and clearly with reference to the accompanying drawings, which are incorporated in and constitute a part of this specification.
As shown in fig. 1, a quantum key distribution system of phase and polarization composite coding includes a sending end 100 and a receiving end 200, where the sending end 100 includes a laser 110, an intensity modulator 120, a phase coding module 130, a polarization coding module 140, and an attenuator 150, which are connected in sequence, the receiving end 200 includes a deviation rectification module 210, a polarization decoding module 220, a phase decoding module 230, and a single photon detector 240, which are connected in sequence, and the sending end 100 and the receiving end 200 are connected by the attenuator 150 and the deviation rectification module 210.
In a first embodiment, as shown in fig. 2, the phase encoding module 130 is an unequal arm MZ interferometer, the polarization encoding module 140 includes an encoding circulator 141, an encoding phase modulator 142, and an encoding faraday rotator 143, which are connected in sequence, an optical outlet of the unequal arm MZ interferometer is connected to one port of the encoding circulator 141, two ports of the encoding circulator 141 are connected to the encoding phase modulator 142, and three ports of the encoding circulator 141 are connected to the attenuator 150; the polarization decoding module 220 comprises a decoding circulator 221, a decoding phase modulator 222 and a decoding Faraday rotation mirror 223, one port of the decoding circulator 221 is connected with the deviation rectifying module 210, the other port of the decoding circulator is sequentially connected with the decoding phase modulator 222 and the decoding Faraday rotation mirror 223, the phase decoding module 230 comprises a polarization beam splitter 231 and two unequal arm MZ interferometers, the input ends of the two unequal arm MZ interferometers are connected with three ports of the decoding circulator 221 through the polarization beam splitter 231, and the output ends of the two unequal arm MZ interferometers are connected with two single photon detectors 240.
In a second embodiment, as shown in fig. 3, the phase encoding module 130 is an unequal arm MZ interferometer, the polarization encoding module 140 includes an encoding circulator 141, an encoding phase modulator 142, and an encoding faraday rotator 143, which are connected in sequence, an optical outlet of the unequal arm MZ interferometer is connected to one port of the encoding circulator 141, two ports of the encoding circulator 141 are connected to the encoding phase modulator 142, and three ports of the encoding circulator 141 are connected to the attenuator 150; the polarization decoding module 220 comprises a decoding circulator 221, a decoding phase modulator 222 and a decoding Faraday rotation mirror 223, one port of the decoding circulator 221 is connected with the deviation rectifying module 210, the two ports are sequentially connected with the decoding phase modulator 222 and the decoding Faraday rotation mirror 223, the phase decoding module 230 comprises a polarization beam splitter 231 and an unequal arm MZ interferometer, the input end of the unequal arm MZ interferometer is connected with one end of the polarization beam splitter 231 through a long arm optical fiber and a short arm optical fiber respectively, a delay line is arranged on the long arm optical fiber, the other end of the polarization beam splitter 231 is connected with three ports of the coding circulator 141, and the output end of the unequal arm MZ interferometer is connected with two paths of single photon detectors 240.
The composite coding unit of embodiment oneThe working principle is as follows: the transmitting end comprises a laser, an intensity modulator IM, an unequal arm MZ Interferometer (Mach-Zehnder Interferometer) as a phase coding module, a polarization coding module consisting of a coding circulator CIR, a coding phase modulator PMA2 and a coding Faraday rotation mirror FM, and an electrically adjustable attenuator EVOA. Wherein the optical fiber of the two ports of the code circulator CIR is fused with the input end of the code phase modulator PMA2 by 45 degrees. An optical pulse emitted by a laser enters the MZ interferometer with unequal arms to be divided into 2 sub-pulses after the intensity of the optical pulse is modulated by the intensity modulator IM, and the phase difference between the 2 sub-pulses is randomly modulated to be 0 pi/2, pi, 3 pi/2 by the phase modulator PMA 1. Then the optical pulse enters the code circulator CIR, the polarization state rotates 45 degrees, at this time, the optical pulse is divided into two vertical polarization components | H > | V | to enter the code phase modulator PMA2, the optical pulse passes through the code phase modulator PMA2 again after being reflected by the code Faraday rotation mirror FM, and the phase difference between | H > | V |) can be changed by modulating the voltage of the code phase modulator PMA2
So that the resulting polarization state is
When the phase difference is between
The corresponding 4 polarization states are shown in table 1.
Table 1: 4 polarization states generated by a transmitting end
Finally, the optical pulse is attenuated to a single photon magnitude by an electrically adjustable attenuator.
The receiving end comprises an electronic control polarization controller EPC (error correction module), a polarization decoder consisting of a decoding circulator CIR, a decoding phase modulator PMB1 and a decoding Faraday rotation mirror FM, a phase decoder consisting of two unequal arm MZ interferometers and 4 single photon detectors. Optical pulses passing through a channelAfter entering the receiving end, the polarization state disturbed by the channel is restored through a deviation rectification module, namely an electronic control polarization controller (EPC) combined with a polarization compensation algorithm. Then decoding the signal by a polarization decoder same as the transmitting end, and adjusting the voltage of a decoding phase modulator PMB1 to make the phase difference between the two components be
And then the polarization state rotates by 45 degrees and enters a polarization beam splitter PBS, two exit ports of the polarization beam splitter PBS are respectively connected with 1 unequal arm MZ interferometer for phase decoding, the corresponding phase modulator PMB2 and the corresponding phase modulator PMB3 simultaneously modulate the phase difference to be 0, pi/2, pi, 3 pi/2, and the final interference result enters a single photon detector for detection.
The specific working process of the embodiment is as follows:
1. triggering a laser: the laser generates a series of pulse lights at a certain repetition frequency through a trigger signal;
2. decoy state modulation: the light pulse is subjected to random intensity modulation by an Intensity Modulator (IM) to become a signal state, a decoy state or a vacuum state;
3. and (3) encoding at a transmitting end: the light pulse modulated by the intensity modulator enters the phase coding module, and random phase modulation is carried out by the phase modulator PMB1, so that the phase difference between two pulses output from the phase coding module is 0, pi/2, pi, 3 pi/2 respectively. Then the light pulse is encoded by a polarization encoding module to generate polarization states of | + >, | - >, | R >, | L >;
4. electrically controlled adjustable attenuator (EVOA): the EVOA attenuates the optical pulses to a single photon magnitude;
5. decoding at a receiving end: the optical signal is transmitted through an optical fiber channel and then enters a receiving end, the polarization change is compensated through a deviation correcting module, and then the optical signal sequentially enters a polarization decoder and a phase decoder to complete the decoding process;
6. measurement: and measuring the system result by using the single photon detector for subsequent processing to generate a security key.
The second embodiment differs from the first embodiment only in that:
the receiving end adopts time division multiplexing, 1 unequal arm MZ interferometer and 2 single photon detectors can be reduced, and the complexity and the cost of the system are reduced.
The structure and the principle of the utility model are integrated, the utility model can improve the efficiency of the protocol by carrying out the phase and polarization composite coding on the single photon bit, and the efficiency can be improved to 4 times of the original protocol by adopting the mode of selecting the base partially; the polarization encoding and decoding structure is simple, the performance is stable, and compared with the traditional multi-laser encoding and passive selective base decoding, the side channel quantum state preparation and measurement information leakage are avoided, so that the complexity of the system is reduced, and the safety of the system is improved; the decoding mode that the receiving end carries out polarization first and then carries out phase is adopted, because the polarization compensation is carried out before the polarization decoding, the polarization state is stable during the phase decoding, the MZI can be directly used, and the stable interference can be realized, so that the phase decoding is very stable, and the MZI has a simple structure and is easy to manufacture; by adopting a phase and polarization composite coding mode, under the condition that one mode is down, the system can work in another mode, and the working stability of the system is provided to a certain extent.
Claims (3)
1. The quantum key distribution system of the phase and polarization composite coding comprises a sending end and a receiving end, and is characterized in that the sending end comprises a laser, an intensity modulator, a phase coding module, a polarization coding module and an attenuator which are sequentially connected, the receiving end comprises a deviation rectifying module, a polarization decoding module, a phase decoding module and a single photon detector which are sequentially connected, and the sending end and the receiving end are connected through the attenuator and the deviation rectifying module.
2. The quantum key distribution system of phase and polarization composite coding of claim 1, wherein the phase coding module is an unequal arm MZ interferometer, the polarization coding module comprises a coding circulator, a coding phase modulator and a coding faraday rotator mirror which are connected in sequence, an optical outlet of the unequal arm MZ interferometer is connected with one port of the coding circulator, two ports of the coding circulator are connected with the coding phase modulator, and three ports of the coding circulator are connected with an attenuator; the polarization decoding module comprises a decoding circulator, a decoding phase modulator and a decoding Faraday rotating mirror, wherein one port of the decoding circulator is connected with a deviation rectifying module, the two ports of the decoding circulator are sequentially connected with the decoding phase modulator and the decoding Faraday rotating mirror, the phase decoding module comprises a polarization beam splitter and two unequal arm MZ interferometers, the input ends of the two unequal arm MZ interferometers are connected with three ports of the decoding circulator through the polarization beam splitter, and the output ends of the two unequal arm MZ interferometers are connected with two single photon detectors.
3. The quantum key distribution system of phase and polarization composite coding of claim 1, wherein the phase coding module is an unequal arm MZ interferometer, the polarization coding module comprises a coding circulator, a coding phase modulator and a coding faraday rotator mirror which are connected in sequence, an optical outlet of the unequal arm MZ interferometer is connected with one port of the coding circulator, two ports of the coding circulator are connected with the coding phase modulator, and three ports of the coding circulator are connected with an attenuator; the polarization decoding module comprises a decoding circulator, a decoding phase modulator and a decoding Faraday rotating mirror, wherein a port of the decoding circulator is connected with a deviation rectifying module, two ports of the decoding circulator are sequentially connected with the decoding phase modulator and the decoding Faraday rotating mirror, the phase decoding module comprises a polarization beam splitter and an unequal arm MZ interferometer, the input end of the unequal arm MZ interferometer is connected with one end of the polarization beam splitter through a long arm optical fiber and a short arm optical fiber respectively, a delay line is arranged on the long arm optical fiber, the other end of the polarization beam splitter is connected with three ports of the encoding circulator, and the output end of the unequal arm MZ interferometer is connected with two paths of single photon detectors.
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| CN111934869A (en) * | 2020-09-18 | 2020-11-13 | 北京中创为南京量子通信技术有限公司 | Polarization decoding device and method based on active basis vector selection |
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| CN111934869A (en) * | 2020-09-18 | 2020-11-13 | 北京中创为南京量子通信技术有限公司 | Polarization decoding device and method based on active basis vector selection |
| CN111934869B (en) * | 2020-09-18 | 2020-12-29 | 北京中创为南京量子通信技术有限公司 | Polarization decoding device and method based on active basis vector selection |
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Assignee: ZHEJIANG QUANTUM TECHNOLOGIES Co.,Ltd. Assignor: Zhao Yibo|Song Xiaotian Contract record no.: X2022330000342 Denomination of utility model: A Quantum Key Distribution System with Composite Encoding of Phase and Polarization Granted publication date: 20200508 License type: Common License Record date: 20220727 |