Multipartite Einstein-Podolsky-Rosen steering and genuine tripartite entanglement with optical networks

TL;DR

This paper reports the first experimental demonstration of multipartite EPR steering and genuine tripartite entanglement in optical networks, revealing directional steering regimes and enabling semi device-independent quantum secret sharing.

Contribution

It introduces the first experimental observation of multipartite EPR steering and tripartite entanglement in optical systems, with analysis of asymmetric loss effects and steering monogamy.

Findings

Identified 8 regimes of directional steering in a 7-qumode state.

Demonstrated continuous variable one-sided semi device-independent quantum secret sharing.

Revealed the directional monogamy of steering in multipartite systems.

Abstract

The Einstein-Podolsky-Rosen (EPR) paradox established a link between entanglement and nonlocality in quantum mechanics. EPR steering is the nonlocality associated with the EPR paradox and has traditionally only been investigated between two parties. Here, we present the first experimental observations of multipartite EPR steering, and of the genuine tripartite continuous variable entanglement of three mesoscopic optical systems. We explore different linear optics networks - each one with optimised asymmetries - that create multipartite steerable states containing different numbers of quantised optical modes (qumodes). By introducing asymmetric loss on a 7-qumode state, we characterize 8 regimes of directional steering, showing that N + 1 regimes exist for an N-qumode state. Further, we reveal the directional monogamy of steering, and experimentally demonstrate continuous variable one-sided semi device-independent quantum secret sharing. Our methods establish principles for the development of multiparty quantum communication protocols with asymmetric observers, and can be extended to qubits, whether photonic, atomic, superconducting, or otherwise.