Scalable Timing Coordination of Bell State Analyzers in Quantum Networks

TL;DR

This paper investigates the scalability and effectiveness of timing synchronization mechanisms for Bell State Analyzers in large-scale quantum networks, considering both memoryless and memory-enabled nodes, and highlights challenges in multi-hop and cyclic network topologies.

Contribution

It provides an analysis of optical path coordination methods for BSA synchronization in complex quantum networks, including the impact of quantum memory and network topology on synchronization feasibility.

Findings

Optical path coordination effectively synchronizes photons in memoryless quantum networks.

Timing mechanisms can have cascading effects impacting adjacent links.

Cycle topologies may hinder synchronization, affecting large network design.

Abstract

The optical Bell State Analyzer (BSA) plays a key role in the optical generation of entanglement in quantum networks. The optical BSA is effective in controlling the timing of arriving photons to achieve interference. It is unclear whether timing synchronization is possible even in multi-hop and complex large-scale networks, and if so, how efficient it is. We investigate the scalability of BSA synchronization mechanisms over multiple hops for quantum networks both with and without memory in each node. We first focus on the exchange of entanglement between two network nodes via a BSA, especially effective methods of optical path coordination in achieving the simultaneous arrival of photons at the BSA. In optical memoryless quantum networks, including repeater graph state networks, we see that the quantum optical path coordination works well, though some possible timing coordination mechanisms have effects that cascade to adjacent links and beyond, some of which was not going to work well of timing coordination. We also discuss the effect of quantum memory, given that end-to-end extension of entangled states through multi-node entanglement exchange is essential for the practical application of quantum networks. Finally, cycles of all-optical links in the network topology are shown to may not be to synchronize, this property should be taken into account when considering synchronization in large networks.