Unidimensional Two-Way Continuous-Variable Quantum Key Distribution Using Coherent States

Area of Science:

• Quantum Information Science
• Quantum Cryptography

Background:

• Continuous-variable quantum key distribution (CV-QKD) enables secure key exchange.
• Two-way CV-QKD protocols offer potential advantages but often have complex structures.
• Existing security analyses can be limited by assumptions about attacker strategies.

Purpose of the Study:

• To propose a simplified unidimensional two-way continuous-variable quantum key distribution protocol.
• To analyze the security of this protocol against general two-mode attacks.
• To evaluate the protocol's performance and application prospects in practical scenarios.

Main Methods:

• Modulation of a single quadrature of coherent states for system simplification.
• Security analysis using a general two-mode attack strategy.
• Derivation of one-mode and optimal two-mode attack strategies.
• Performance simulations under various attack scenarios.

Main Results:

• The proposed unidimensional protocol simplifies the two-way system structure.
• Security analysis demonstrates robustness against general two-mode attacks.
• Performance is comparable to Gaussian modulated protocols, even against optimal attacks.
• The protocol maintains good performance under conditions of short distance and high noise.

Conclusions:

• The unidimensional two-way CV-QKD protocol offers a practical simplification without significant security compromise.
• It demonstrates a good balance between system complexity and security performance.
• The protocol shows strong potential for implementation in real-world quantum communication systems.