Applicability of Squeezed- and Coherent-State Continuous-Variable Quantum Key Distribution over Satellite Links

Area of Science:

• Quantum Information Science
• Satellite Communication
• Quantum Cryptography

Background:

• Satellite-based quantum key distribution (QKD) faces challenges like channel attenuation and atmospheric turbulence.
• Continuous-variable (CV) QKD protocols using coherent and squeezed states are being explored for long-distance links.

Purpose of the Study:

• To assess the feasibility of CV-QKD over low Earth orbit satellite links.
• To analyze the impact of channel noise, turbulence, and finite data on QKD security.
• To investigate methods for enhancing the robustness and applicability of satellite QKD.

Main Methods:

• Theoretical analysis of CV-QKD protocols with coherent and squeezed states.
• Modeling of channel attenuation, atmospheric turbulence, and finite data effects.
• Derivation of security bounds based on untrusted channel noise.
• Simulation of segmented satellite passes and optimized signal squeezing.

Main Results:

• Tight security bounds indicate significant noise and loss challenges for current satellite QKD setups.
• Splitting satellite passes into segments improves robustness against channel noise, enabling secure keys under active collective attacks.
• Optimized signal squeezing offers substantial improvements over coherent-state protocols, allowing for lower system requirements and higher noise/attenuation resilience.

Conclusions:

• Satellite-based CV-QKD is challenging but feasible with optimized protocols and system stabilization.
• Signal squeezing is a key technique for enhancing the practical implementation of satellite QKD.
• Segmented key extraction and optimized squeezing are crucial for establishing secure satellite quantum communication networks.