Conclusive Experimental Demonstration of One-Way Einstein-Podolsky-Rosen Steering

Abstract

One of the most noteworthy and fundamental features of quantum mechanics is the fact that it admits stronger correlations between distant objects than what would be possible in a classical world. Quantum correlations can be categorized into the following classes, which form a strict hierarchy [1–3]: entanglement is a superset of Einstein-Podolsky-Rosen (EPR) steerability, which in turn is a superset of Bell nonlocality. Out of these, steering is special in that it allows for, and in fact intrinsically contains, asymmetry. Steering is operationally defined as a quantum information task, where one untrusted party (for instance called Alice) tries to convince another distant, trusted party (Bob) that they share entanglement. Bob asks Alice to make certain measurements on her quantum system (e.g., particle) and to announce the measurement outcomes, but is not sure whether Alice answers honestly, or indeed, even has a particle. He also makes corresponding measurements on his particle and checks whether the correlations of their measurement outcomes rule out a so-called local hidden state model for his particle, thereby proving shared entanglement.