Southwest Quantum Information and Technology

Bell nonlocality vs. EPR steering in polarization-entangled photons

Presenting Author: Chen Jie Xin, Harvey Mudd College
Contributing Author(s): Evan Atchison and Theresa W. Lynn

Violation of a Bell inequality, or Bell nonlocality, is a signature of only a restricted class of two-qubit entangled states. States with too little entanglement to be Bell nonlocal may nevertheless be EPR steerable: measurements performed on one subsystem can influence probabilities of measurement outcomes on the other subsystem, thus ‘steering’ the second subsystem. Surprisingly, given the mutual nature of bipartite entanglement, certain two-qubit entangled states are actually one-way steerable, with only one subsystem able to steer the other. EPR steering, both mutual and one-way, could be useful as a signature of partial entanglement in a variety of quantum communication or distributed quantum computing schemes. We study EPR-steerable states of photon pairs entangled in polarization, produced via spontaneous parametric down-conversion. By varying the entanglement purity, we map out a range of entangled states that may be Bell nonlocal and steerable, Bell local but steerable, or Bell local and not EPR steerable. The simplicity of the experimental approach makes it suitable for an undergraduate advanced laboratory.

(Session 5 : Thursday from 5:00pm - 7:00pm)