Continuous-variable quantum key distribution (CV-QKD) method and system

Patent metadata

Field	Value
Publication number	US-12088707-B2
Application number	US-202117435023-A
Country	US
Kind code	B2
Filing date	Jan 23, 2021
Priority date	Feb 14, 2020
Publication date	Sep 10, 2024
Grant date	Sep 10, 2024

Abstract

A continuous-variable quantum key distribution (CV-QKD) method and system is provided. The CV-QKD method includes: step 1: transmitting a quantum signal and a local oscillation signal synchronously based on time and polarization multiplexing, and performing detection to obtain detection data; and step 2: compensating for the detection data based on a phase compensation algorithm and public data. In this way, a phase can be compensated accurately in channel fading, so as to improve performance of the CV-QKD system.

First claim

What is claimed is:

1. A continuous-variable quantum key distribution (CV-QKD) method, comprising:
transmitting a quantum signal and a local oscillation signal synchronously through a free-space channel based on time delay and polarization multiplexing, and performing detection to obtain detection data, comprising:
chopping, by an intensity modulator, continuous laser light emitted by a laser, and converting the continuous laser light into a light pulse sequence;
modulating a part of the light pulse sequence, loading to-be-transmitted information to the quantum signal, and performing time delay;
combining a light pulse sequence of the quantum signal loaded with the to-be-transmitted information and a light pulse sequence of the local oscillation signal through polarization multiplexing to obtain a combined light pulse sequence, and transmitting the combined light pulse sequence to a receiving end through the free-space channel;
performing, by a polarization beam splitter, beam splitting at the receiving end, aligning the light pulse sequence of the quantum signal loaded with the to-be-transmitted information and the light pulse sequence of the local oscillation signal in time domain through delay, and performing homodyne detection; and
collecting, by a data collection device, an electrical signal output by a detector, and performing digital signal processing to obtain the detection data; and

implementing a phase compensation for the detection data based on a phase compensation algorithm and public data.

2. The CV-QKD method according to claim 1 , wherein implementing a phase compensation for the detection data based on a phase compensation algorithm and public data comprises:
publishing the public data by two communication parties, and performing, by a transmitting end, phase shifting, by applying a plurality of predetermined phase shifting angles, on the public data to generate contrasted data;
calculating a cross-correlation between the contrasted data and the detection data, and finding a maximum value, wherein a phase shifting angle of the plurality of phase shifting angles that produces the maximum value is a phase drift estimating value;
performing data compensation on the detection data based on the phase drift estimating value to obtain compensated detection data; and
performing negotiated decoding on the compensated detection data, and performing privacy amplification to obtain a final key.

3. The CV-QKD method according to claim 2 , wherein a length of the public data affects compensation accuracy.

4. The CV-QKD method according to claim 2 , wherein a range of the phase shifting is 0 to 360 degrees; and
an interval between a plurality of phase shifting is set, and affects compensation accuracy.

5. A continuous-variable quantum key distribution (CV-QKD) system, comprising:
a first module comprising circuitry configured to transmit a quantum signal and a local oscillation signal synchronously through a free-space channel based on time delay and polarization multiplexing, and perform detection to obtain detection data, wherein the first module comprises:
a first submodule configured to chop, by an intensity modulator, continuous laser light emitted by a laser, and convert the continuous laser light into a light pulse sequence;
a second submodule configured to modulate a part of the light pulse sequence, load to-be-transmitted information to the quantum signal, and perform time delay;
a third submodule configured to combine a light pulse sequence of the quantum signal loaded with the to-be-transmitted information and a light pulse sequence of the local oscillation signal through polarization multiplexing to obtain a combined light pulse sequence, and transmit the combined light pulse sequence to a receiving end through the free-space channel;
a fourth submodule configured to perform, by a polarization beam splitter, beam splitting at the receiving end, align the light pulse sequence of the quantum signal loaded with the to-be-transmitted information and the light pulse sequence of the local oscillation signal in time domain through delay, and perform homodyne detection; and
a fifth submodule configured to collect, by a data collection device, an electrical signal output by a detector, and perform digital signal processing to obtain the detection data; and

a second module comprising circuitry configured to: implement a phase compensation for the detection data based on a phase compensation algorithm and public data.

6. The CV-QKD system according to claim 5 , wherein the second module comprises:
a primary submodule configured to: publish the public data by two communication parties, and perform, by a transmitting end, phase shifting on the public data to generate contrasted data;
a secondary submodule configured to: calculate a cross-correlation between the contrasted data and the detection data, and find a maximum value, wherein a phase shifting angle of the maximum value is a phase drift estimating value;
a tertiary submodule configured to: perform data compensation on the detection data based on the phase drift estimating value to obtain compensated detection data; and
a quatenary submodule configured to: perform negotiated decoding on the compensated detection data, and perform privacy amplification to obtain a final key.

7. The CV-QKD system according to claim 6 , wherein a length of the public data affects compensation accuracy.

8. The CV-QKD system according to claim 6 , wherein a range of the phase shifting is 0 to 360 degrees; and
an interval between a plurality of phase shifting is set, and affects compensation accuracy.

Assignees

• Univ Shanghai Jiaotong

Inventors

• Huang Peng
• Wang Shiyu
• Zeng Guihua

Classifications

• H04L9/0852

  Quantum cryptography (transmission systems employing electromagnetic waves other than radio waves, e.g. light, infrared H04B10/00; wavelength-division multiplex systems H04J14/02; WDM arrangements H04J14/03) · CPC title

• H04B10/5561

  Digital phase modulation · CPC title

• H04B10/541

  Digital intensity or amplitude modulation · CPC title

• H04B10/614

  comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers (H04J14/06 takes precedence) · CPC title

• H04B10/532

  Polarisation modulation · CPC title