Macroscopic entanglement distribution with atomic ensembles

TL;DR

This paper evaluates a protocol for distributing macroscopic entanglement over atomic ensembles, demonstrating its robustness and scalability up to one million particles despite realistic noise levels.

Contribution

It develops advanced numerical methods to simulate large atomic ensembles and assesses the protocol's viability and robustness under realistic decoherence conditions.

Findings

Entanglement remains robust at moderate dephasing levels.

Stronger noise gradually suppresses entanglement.

The protocol is viable for large-scale atomic ensembles.

Abstract

The distribution of entanglement is a crucial task for quantum communication towards realizing a globe-spanning quantum internet. Recently a protocol for deterministic long-distance distribution of macroscopic entanglement over a network of ensembles of qubits was introduced [Adv. Quantum Technol. 2025, 8, 2400524]. It was shown that this protocol allows for the propagation of macroscopic amounts of entanglement with a protocol complexity that is independent on the ensemble size. However, questions remained on whether the scheme is viable, particularly for a large particle number, which is the case for realistic atomic ensembles. Here we develop improved numerical techniques that allow calculation of realistic ensemble sizes up to 10^6 with a negligible loss of accuracy. We find that moderate dephasing leaves the entanglement largely intact at the magic times, whereas stronger noise monotonically suppresses the entanglement. Our results demonstrate that the protocol retains its functionality towards the macroscopic regime and provides quantitative benchmarks for its robustness under a realistic level of decoherence.