Experimental direct quantum communication with squeezed states

Area of Science:

• Quantum Communication
• Quantum Information Science
• Optical Physics

Background:

• Quantum secure direct communication (QSDC) offers a novel framework for transmitting information securely via quantum channels, distinct from key-based quantum key distribution (QKD).
• Optical QSDC protocols, employing discrete and continuous variable encodings, are crucial for advancing secure communication technologies.

Purpose of the Study:

• To present the first table-top proof of principle for continuous-variable QSDC.
• To analyze the implementation of QSDC using coherent versus squeezed light sources.
• To evaluate the security and reliability of QSDC in practical, lossy, and noisy environments.

Main Methods:

• Development and analysis of a table-top continuous-variable QSDC system.
• Comparison of coherent and squeezed light sources for QSDC implementation.
• Security analysis using Wyner wiretap channel theory against a beam-splitter attack.

Main Results:

• Squeezed states provide superior security and reliability compared to coherent states in lossy and noisy quantum communication channels.
• The practical QSDC implementation demonstrates feasibility using standard telecom components.
• Wyner wiretap channel theory confirms the enhanced security offered by squeezed states.

Conclusions:

• Continuous-variable QSDC is a viable technology for secure communication.
• Squeezed light sources enhance the security and robustness of QSDC systems.
• The developed system can potentially support secure quantum metropolitan networks with multiplexing capabilities.