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A quantum key distribution phase encoding device

A quantum key distribution and phase encoding technology, which is applied in the field of quantum key distribution phase encoding devices, can solve the problems of high requirements for the drive circuit of the phase modulator, inconsistent losses of the two time windows, and large insertion loss of the phase modulator. Improve stability and practicability, eliminate non-interference components, and improve the effect of safe coding rate

Active Publication Date: 2022-08-05
杭州慧明量子通信技术有限公司
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] In view of the above defects in the prior art, the present invention proposes a phase encoding device for quantum key distribution to solve the problem of inconsistent loss of the two time windows caused by the large insertion loss of the phase modulator of the quantum key distribution system in the prior art, and the phase modulation Due to technical defects such as high requirements for the drive circuit of the interferometer, high cost and complexity, and the use of polarization multiplexing to improve the energy utilization rate of the interferometer, the security coding rate of the system can be improved.

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  • A quantum key distribution phase encoding device
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Embodiment 1

[0035] The structure of the encoding device is as follows: the orthogonal polarization time window generating element OPTG is a four-port polarization beam splitter PBS, and the first port and the third port of the polarization beam splitter PBS are respectively generated as orthogonal polarization time windows. The input port and the output port of the element OPTG, the second port and the fourth port of the polarization beam splitter are directly connected by a polarization maintaining fiber with a length of L1, the length L1=t*ns*c (ns is the polarization maintaining fiber The refractive index of the slow axis, c is the speed of light in vacuum). The first path selection element PS1 is the first beam splitter BS1, the second path selection element PS2 is the first optical switch OS1, the third path selection element PS3 is the second optical switch OS2, and the first path selection element PS2 is the second optical switch OS2. The beam splitter BS1 is a 1×2 beam splitter, t...

Embodiment 2

[0044] The structure of the encoding device is as follows: the orthogonal polarization time window generating element OPTG is a four-port polarization beam splitter PBS, and the first port and the third port of the polarization beam splitter PBS are respectively generated as orthogonal polarization time windows. The input port and the output port of the element OPTG, the second port and the fourth port of the polarization beam splitter are directly connected by a polarization maintaining fiber with a length of L1, the length L1=t*ns*c (ns is the polarization maintaining fiber The refractive index of the slow axis, c is the speed of light in vacuum). The first path selection element PS1 is the third optical switch OS3, the second path selection element PS2 is the second beam splitter BS2, the third path selection element PS3 is the fourth optical switch OS4, and the third path selection element PS2 is the fourth optical switch OS4. The optical switch OS3 is a 1×2 optical switch...

Embodiment 3

[0053] The structure of the encoding device is as follows: the orthogonal polarization time window generating element OPTG is a high-birefringence polarization-maintaining fiber PMF with a length of L2, and the length L2=t*(ns-nf)*c (ns and nf respectively) is the refractive index of the slow axis and fast axis of the polarization-maintaining fiber, and c is the speed of light in vacuum). The first path selection element PS1 is the fifth optical switch OS5, the second path selection element PS2 is the sixth optical switch OS6, the third path selection element PS3 is the third beam splitter BS3, and the fifth path selection element PS3 is the third beam splitter BS3. The optical switch OS5 is a 1×2 optical switch, the sixth optical switch OS6 is a 2×2 optical switch, and the third beam splitter BS3 is a 2×1 beam splitter.

[0054] The three-phase encoding process of the embodiment is:

[0055] The laser LD generates a horizontally polarized light pulse P0 that enters the first...

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Abstract

A quantum key distribution phase encoding device, comprising a laser, an orthogonal polarization time window generating element, a first path selection element, a second path selection element, a third path selection element, a half-wave plate and a quarter-wave plate, The orthogonal polarization time window generating element is used to convert a single light pulse into sub-pulses with orthogonal polarizations located in two time windows with a time interval of t respectively; the input port of the laser and the orthogonal polarization time window generating element They are connected by 45° fusion splicing through polarization-maintaining fibers. Compared with the prior art, the present invention can prepare four kinds of phase encoding states without a phase modulator, and the polarizations of the two time window pulses are perpendicular to each other, so that the non-interference components can be eliminated to improve the energy utilization rate, and thus the system can be improved. security rate. The optical switch only needs to be driven by a digital circuit, which can realize stable coding, improve the stability and practicability of the system, and reduce the cost and complexity of the coding device.

Description

technical field [0001] The invention relates to the technical field of quantum phase encoding, in particular to a quantum key distribution phase encoding device. Background technique [0002] Phase encoding is a commonly used encoding method for the BB84 quantum key distribution protocol. The conventional phase encoding scheme uses an unequal-arm Mach-Zehnder interferometer or a Faraday-Michelson interferometer, and a phase modulator is added to one arm to randomly modulate the phase of the long and short arms. difference, thereby preparing 4 phase-encoded states. However, the phase modulator has high insertion loss and cost, which makes the loss of the two time windows before and after the coding state inconsistent, which affects the security of the system. And adjusting the 4 phases requires loading 4 voltages, at least 3 driving voltages, and the highest voltage is more than 1.5 times the half-wave voltage, which requires higher requirements for the analog-to-digital con...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L9/08
CPCH04B10/548H04B10/70
Inventor 王士通王慎周宏飞
Owner 杭州慧明量子通信技术有限公司