Performance Analysis of Relativistic Quantum Key Distribution for Deep-Space Optical Communication

Quantum key distribution (QKD) is a method for securely exchanging keys based on quantum mechanics. QKD has been thoroughly examined for terrestrial and near-Earth satellite applications; however, forthcoming deep-space links are anticipated to experience considerable relativistic effects. Quantum states can be altered in these circumstances by relative motion between terminals and by gravitational effects, which may affect entan-glement, measurement outcomes, and overall security. The effectiveness of entanglement-based quantum key distribution (QKD) in relativistic motion is investigated in this work, with particular attention to deep-space optical communication. The quantum channel model includes Wigner rotations due to Lorentz transformations, polarization mixing due to Doppler shift, and redshift due to gravity. This method gives us new ways to analyze the quantum bit error rate (QBER), quantum entanglement fidelity, Bell inequality violation , and secret key rate. Our numerical simulations show that when the relative velocity becomes high enough, the polarization correlations start to break down significantly. This leads to more errors in the quantum bits, making it harder to generate a secure secret key. Even though quantum nonlocality persists at these speeds, relativistic effects make it much harder to actually extract a secure key.