Multipartite Einstein-Podolsky-Rosen steering sharing with separable states

TL;DR

This paper demonstrates that Einstein-Podolsky-Rosen steering, a quantum correlation resource, can be distributed among multiple parties using separable states, enabling secure quantum communication protocols like quantum key distribution and secret sharing.

Contribution

It introduces novel protocols for distributing EPR steering via separable states, expanding the understanding of quantum correlations and their practical applications.

Findings

Steering can be distributed via separable states using simple optical components.

Protocols enable one-way Gaussian steering suitable for quantum key distribution.

Extension to three parties allows for complex steerability and secret sharing.

Abstract

Distribution of quantum correlations among remote users is a key procedure underlying many quantum information technologies. Einstein-Podolsky-Rosen steering, which is one kind of such correlations stronger than entanglement, has been identified as a resource for secure quantum networks. We show that this resource can be established between two and even more distant parties by transmission of a system being separable from all the parties. For the case with two parties, we design a protocol allowing to distribute one-way Gaussian steering between them via a separable carrier; the obtained steering can be used subsequently for one-sided device-independent (1sDI) quantum key distribution. Further, we extend the protocol to three parties, a scenario which exhibits richer steerability properties including one-to-multimode steering and collective steering, and which can be used for 1sDI quantum secret sharing. All the proposed steering distribution protocols can be implemented with squeezed states, beam splitters and displacements, and thus they can be readily realized experimentally. Our findings reveal that not only entanglement but even steering can be distributed via communication of a separable system. Viewed from a different perspective, the present protocols also demonstrate that one can switch multipartite states between different steerability classes by operations on parts of the states.