Experimental quantification of asymmetric Einstein-Podolsky-Rosen steering

TL;DR

This paper experimentally demonstrates asymmetric EPR steering in two-qubit states, providing a practical quantification method and a necessary and sufficient condition, highlighting fundamental quantum nonlocality asymmetry.

Contribution

It introduces an experimental demonstration of asymmetric EPR steering with a new quantification method and a clear criterion for one-way steering in two-qubit states.

Findings

Confirmed the existence of one-way EPR steering.

Proposed a practical steerability quantification method.

Established a necessary and sufficient condition for EPR steering.

Abstract

Einstein-Podolsky-Rosen (EPR) steering describes the ability of one observer to nonlocally "steer" the other observer's state through local measurements. It exhibits a unique asymmetric property, i.e., the steerability of one observer to steer the other's state could be different from each other, which can even lead to a one-way EPR steering, i.e., only one observer obtains the steerability in the two-observer case. This property is inherently different from the symmetric concepts of entanglement and Bell nonlocality and has been attracted increasing interests. Here, we experimentally demonstrate the asymmetric EPR steering for a class of two-qubit states in the case of two measurement settings. We propose a practical method to quantify the steerability. We then provide a necessary and sufficient condition for EPR steering and clearly show the case of one-way EPR steering. Our work provides a new insight on the fundamental asymmetry of quantum nonlocality and would find potential application in asymmetric quantum information processing.