Quantum Lunch: Benchmarking purity and correlations for quantum states

Speaker: Bill Coish from McGill University

Title:
Benchmarking purity and correlations for quantum states
(joint work with Katarzyna Roszak and Pawel Horodecki)

Abstract:
A joint measurement performed on two identically-prepared independent copies of a quantum state can be used to directly establish the unconditional purity of that quantum state.  In most realistic quantum systems, quantum or classical correlations may develop before a joint measurement can be performed, invalidating the independence requirement for an unconditional purity measurement.  Here, we introduce and assess a protocol that can be used to establish purity from a simple joint measurement, even in the presence of correlations.  This can be achieved given an accurate model for the development of correlations, typically through interaction with a common environment.  This scheme can also be used to establish the presence of quantum or classical pairwise correlations given an accurate model of purity decay.