Southwest Quantum Information and Technology

Demonstrations of one-way EPR steerable polarization-entangled photon states

Presenting Author: Lorenzo Calvano, Harvey Mudd College
Contributing Author(s): Nick Koskelo, Ivy Chen, Guadalupe Quirarte, Theresa Lynn

EPR steering is a signature of a class of two-qubit states for which one party, who holds one qubit of the pair, can prove to the possessor of the other qubit that their states are entangled. The protocol requires many copies of the two-qubit state, and involves the first party demonstrating that their measurement choices and results alter the one-qubit state held by the second party, thus “steering” the second party’s state. EPR steerable states form a strict superset of Bell nonlocal states, since they include states with too little entanglement to be Bell nonlocal. Surprisingly, given the mutual nature of bipartite entanglement, certain two-qubit states are actually one-way steerable, with Alice being able to “steer,” Bob, but not vice versa. We demonstrate experimental violation of an all-versus-nothing (AVN) steering inequality for partially polarization-entangled photon pairs. Using this AVN steering inequality, we further demonstrate an asymmetry between the parties in which Alice steers Bob, but Bob cannot steer Alice. We discuss further studies of the parameter regime over which this one-way steering phenomenon can be observed. 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. One-way steering has the potential for further application in communication protocols where the level of trust is asymmetric between the parties.

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