Realization of High-Reliable Coherent-State Quantum Secure Communication

Area of Science:

• Quantum Information Science
• Quantum Communication
• Cryptography

Background:

• Continuous-variable quantum secure communication (CV-QSC) using Gaussian mapping offers high capacity and transmission rates.
• A one-time pad (OTP) encryption scheme provides theoretical security.
• Wyner's wiretap channel theory is a standard for evaluating quantum communication security.

Purpose of the Study:

• To establish and evaluate a reliable coherent-state CV-QSC system.
• To develop an information reconstruction scheme for low-to-medium signal-to-noise ratios.
• To design a self-balanced homodyne detector for improved performance.

Main Methods:

• Implementation of a coherent-state CV-QSC system with Gaussian mapping.
• Application of Wyner's wiretap channel theory for security evaluation.
• Development of a multidimensional rotation-based information reconstruction scheme.
• Design of a self-balanced homodyne detector with a programmable gain amplifier.

Main Results:

• A system achieving a low electronic noise variance ($1.624\times {10}^{-7}$ $V^2$) and 715 MHz bandwidth.
• Secure transmission of a dichroic image over 10-km optical fiber with a block error rate of $8.78\times {10}^{-5}$.
• Achieved a secrecy capacity of $2.44\times {10}^5$ bits per second.

Conclusions:

• The established coherent-state CV-QSC system is reliable and secure.
• The proposed information reconstruction scheme enhances secret message extraction.
• The developed homodyne detector improves system performance for practical applications.