PILOT BASED QUANTUM ERROR CORRECTION SCHEME FOR SATELLITE COMMUNICATION

Abstract

This research addresses the significant problem of signal loss in satellite-based Quantum Key Distribution. This issue slows down the development of global secure communication networks. Current QKD links using Low Earth Orbit satellites face serious fidelity loss due to atmospheric turbulence and polarization errors caused by motion. Existing Quantum Error Correction methods often do not perform well in these complex and changing channel conditions. This thesis proposes and evaluates a Pilot-Based Quantum Error Correction (PB-QEC) framework tailored for LEO-to-ground quantum channels. A crucial part of this work involves creating a realistic hybrid channel model that merges atmospheric interference and satellite motion. In this model, a scheme is developed where known pilot quantum states are interspersed among data qubits. By measuring these pilots at the ground station, the framework enables real-time estimation of channel-induced errors, particularly polarization drifts, allowing for adaptive, feed-forward correction. The performance of the PB-QEC framework is tested through extensive numerical simulations using data from the Ethiopian Remote Sensing Satellite-1 (ETRSS-1). The results reveal that PB-QEC consistently outperforms traditional QEC methods, including repetition, Shor, Steane, and surface codes, in highly dynamic satellite-to-ground channels. Conventional codes need many qubits (typically 7–9 or more), involve complex decoding, and are less suited for satellite links due to high resource demands and sensitivity to quickly changing error patterns. In contrast, PB-QEC offers strong protection against Pauli-type polarization errors with extremely low qubit overhead (0.002307%) and low computational complexity through simple on-the-fly decoding. Simulation results show that PB-QEC achieves higher quantum state fidelity, significantly lowers the Quantum Bit Error Rate (QBER), and improves secure key rates by adaptively correcting motion-induced polarization drift in real time. This positions PB-QEC as a scalable and practical solution for the resource-limited and variable conditions of satellite QKD.