Analysis of Quantum Network Coding for Realistic Repeater Networks

TL;DR

This paper evaluates quantum network coding (QNC) in realistic noisy conditions, showing it can double throughput with some fidelity trade-offs and highlighting the impact of local gate errors.

Contribution

It provides the first analysis of QNC performance under noise and resource limitations, demonstrating its advantages and limitations in practical quantum networks.

Findings

QNC can double Bell pair creation rate compared to entanglement swapping.

Output fidelity drops below 0.5 when initial fidelity is below 0.90.

Local gate errors significantly affect QNC performance.

Abstract

Quantum repeater networks have attracted attention for the implementation of long-distance and large-scale sharing of quantum states. Recently, researchers extended classical network coding, which is a technique for throughput enhancement, into quantum information. The utility of quantum network coding (QNC) has been shown under ideal conditions, but it has not been studied previously under conditions of noise and shortage of quantum resources. We analyzed QNC on a butterfly network, which can create end-to-end Bell pairs at twice the rate of the standard quantum network repeater approach. The joint fidelity of creating two Bell pairs has a small penalty for QNC relative to entanglement swapping. It will thus be useful when we care more about throughput than fidelity. We found that the output fidelity drops below 0.5 when the initial Bell pairs have fidelity F < 0.90, even with perfect local gates. Local gate errors have a larger impact on quantum network coding than on entanglement swapping.