Realistic Simulation of Quantum Repeater with Encoding and Classical Error Correction

TL;DR

This paper presents a simulation of a quantum repeater protocol with encoding and classical error correction, demonstrating error suppression and high-fidelity entanglement distribution over long distances.

Contribution

It introduces a detailed simulation framework for a quantum repeater with encoding and classical error correction, extending SeQUeNCe with new features and noise models.

Findings

QRE-CEC suppresses errors to second order

Logical Bell pairs with 0.91 fidelity over 2000 km

Simulation reveals practical challenges in implementation

Abstract

Quantum repeaters are essential for scalable long-distance quantum networking. As quantum information processing moves toward fault-tolerant and error-corrected operations, it becomes increasingly important to study quantum repeaters that also move beyond raw physical entanglement and towards logical entanglement. In this paper, we implement and simulate the quantum repeater with encoding and classical error correction (QRE-CEC) protocol in SeQUeNCe, a discrete-event simulator of quantum networks. The protocol distributes logical Bell pairs, performs encoded entanglement swapping, and uses classical error correction for the decoding of entanglement swapping measurement outcomes to determine Pauli-frame corrections. For this study, we extend SeQUeNCe with a stabilizer-based backend, add support for CSS code-based encoded operations, and integrate gate, measurement, idle decoherence, and state-initialization noise models. Our simulation results show that QRE-CEC suppresses all modeled errors to the second order. Also, QRE-CEC can distribute logical Bell pairs with 0.91 fidelity over a distance of 2000 km under the parameter regimes we study. Beyond protocol-level performance evaluation, our implementation exposes practical simulator and control-plane challenges that are typically abstracted away in theoretical studies.