Multipartite entanglement outperforming bipartite entanglement under limited quantum system sizes

TL;DR

This paper demonstrates that under limited local quantum system sizes, multipartite entanglement provides unique advantages over bipartite entanglement, making it an essential resource for certain quantum information tasks.

Contribution

It proves that multipartite entanglement cannot always be simulated by bipartite entanglement when local system sizes are limited, highlighting its indispensable role.

Findings

Certain multipartite states cannot be generated from bipartite entanglement under size constraints.

Multipartite entanglement can be prepared from bipartite resources using temporal communication within size limits.

Some multipartite states remain inaccessible even with bipartite resources and size limitations.

Abstract

Multipartite quantum entanglement serves as a resource for spatially separated parties performing distributed quantum information processing. Any multipartite entangled state can be generated from appropriately distributed bipartite entangled states by local operations and classical communication (LOCC), and in this sense, any distributed process based on shared multipartite entanglement and LOCC is simulatable by using only bipartite entangled states and LOCC. We show here that this reduction scenario does not hold when there exists a limitation on the size of the local quantum system of each party. Under such a limitation, we prove that there exists a set of multipartite quantum states such that these states in the set cannot be prepared from any distribution of bipartite entanglement while the states can be prepared from a common resource state exhibiting multipartite entanglement. We also show that temporal uses of bipartite quantum communication resources within a limitation of local system sizes are sufficient for preparing this common resource state exhibiting multipartite entanglement, yet there also exist other states exhibiting multipartite entanglement which cannot be prepared even in this setting. Hence, when the local quantum system sizes are limited, multipartite entanglement is an indispensable resource without which certain processes still cannot be accomplished.