Analysis of Asynchronous Protocols for Entanglement Distribution in Quantum Networks

TL;DR

This paper evaluates asynchronous protocols for entanglement distribution in quantum networks, considering practical factors like decoherence and classical communication, and finds the sequential scheme preferable for real-world applications.

Contribution

It introduces and analyzes two minimal asynchronous entanglement distribution protocols, incorporating realistic network conditions and performance metrics.

Findings

Sequential scheme outperforms parallel scheme in practical settings.

Cutoff strategy improves entanglement quality and network performance.

Performance assessed on SURFnet topology as a function of memory coherence time.

Abstract

The distribution of entanglement in quantum networks is typically approached under idealized assumptions such as perfect synchronization and centralized control, while classical communication is often neglected. However, these assumptions prove impractical in large-scale networks. In this paper, we present a pragmatic perspective by exploring two minimal asynchronous protocols: a parallel scheme generating entanglement independently at the link level, and a sequential scheme extending entanglement iteratively from one party to the other. Our analysis incorporates non-uniform repeater spacings and classical communications and accounts for quantum memory decoherence. We evaluate network performance using metrics such as entanglement bit rate, end-to-end fidelity, and secret key rate for entanglement-based quantum key distribution. Our findings suggest the sequential scheme's superiority due to comparable performance with the parallel scheme, coupled with simpler implementation. Additionally, we impose a cutoff strategy to improve performance by discarding attempts with prolonged memory idle time, effectively eliminating low-quality entanglement links. Finally, we apply our methods to the real-world topology of SURFnet and report the performance as a function of memory coherence time.