Security analysis of continuous variable quantum key distribution based on entangled states with biased correlations

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Quantum Communication

Background:

• Einstein-Podolsky-Rosen (EPR) entangled states are crucial for enhancing secret key rates and secure distances in continuous-variable quantum key distribution (CV-QKD).
• Practical imperfections in preparing entangled states lead to asymmetrical variances, known as the bias effect.
• This bias effect is often incorrectly attributed to the untrusted channel, degrading CV-QKD system performance.

Purpose of the Study:

• To theoretically quantify the impact of the bias effect on secret key rate and secure distance in CV-QKD.
• To propose and analyze a protocol for generating unbiased entangled states.
• To compare the performance of unbiased entangled states against biased and coherent states in CV-QKD.

Main Methods:

• Theoretical analysis of the bias effect in two-mode squeezing (entangled state) preparation.
• Development of a protocol for generating unbiased entangled states.
• Mathematical modeling to calculate secret key rates and secure distances for different state preparations.

Main Results:

• The bias effect in entangled states significantly reduces the secret key rate and secure distance of CV-QKD systems.
• The proposed unbiased entangled states protocol effectively mitigates the performance degradation caused by bias.
• Unbiased entangled states yield the longest secure distance and highest key rate compared to biased entangled and coherent states.

Conclusions:

• Addressing the bias effect in entangled state preparation is critical for optimizing CV-QKD performance.
• The unbiased entangled states protocol offers a viable solution to overcome practical imperfections.
• This approach enhances the security and efficiency of quantum key distribution.