Quantum key distribution with imperfect devices

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K13469
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13010:Mathematical physics and fundamental theory of condensed matter physics-related
• Research Institution: The University of Tokyo
• Principal Investigator: Sasaki Toshihiko 東京大学, 大学院工学系研究科(工学部), 講師 (80734350)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 量子情報理論 / 量子鍵配送

Outline of Final Research Achievements

The purpose of this research project is to extend the device model of quantum key distribution to be more realistic without sacrificing performance as much as possible, and to guarantee security using data that can be confirmed by experiments. There are various studies on extending the device model of quantum key distribution, but most of them consider only the asymptotic performance when the experimental time is infinite, which simplifies the analysis. This project is unique in that it analyzed the case of finite experimental time.
The subjects in this project are how to rigorously test light sources, how to avoid the negative effects of substituting the devices with cheaper ones, how to perform quantum key distribution using photodetectors, which is cheaper than photon detectors, and how to develop numerical methods that can automatically deal with various device imperfections.

Free Research Field

量子鍵配送

Academic Significance and Societal Importance of the Research Achievements

量子鍵配送は遠隔2者間で安全な乱数列を共有する手法であり、これを用いることで長期的に安全な秘密通信が可能になる。この手法は実際に製品にもなり、社会に導入されようとしている。実際の装置の安全性を示すためには、理想化された状況だけでなく、現実に即したモデルを考える必要があるが。本研究課題では、現実的な制約のもとで安全性を示すための新たな手法を開発することで、理論と現実のギャップを縮め、量子鍵配送を安価に実現することに貢献した。