Experimental verification of quantum discord in continuous-variable states

• Published in: Journal of physics. B, Atomic, molecular, and optical physics Vol. 47; no. 2; pp. 1 - 8
• Main Authors: Hosseini, S, Rahimi-Keshari, S, Haw, J Y, Assad, S M, Chrzanowski, H M, Janousek, J, Symul, T, Ralph, T C, Lam, P K
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 28.01.2014; Institute of Physics
• Subjects: Beam splitters; Classical and quantum physics: mechanics and fields; Coherence; Conditioning; continuous variable quantum optics; Correlation analysis; Exact sciences and technology; Gaussian; Gaussian states; Non-Gaussian; Physics; Quadratures; quantum discord; Quantum mechanics; Separation; Continuous variables; Quantum correlation; Gaussian states; Vacuum states; Bipartite systems
• ISSN: 0953-4075; 1361-6455
• DOI: 10.1088/0953-4075/47/2/025503

We introduce a simple and efficient technique to verify quantum discord in unknown Gaussian states and a certain class of non-Gaussian states. We show that any separation in the peaks of the marginal distributions of one subsystem conditioned on two different outcomes of homodyne measurements performed on the other subsystem indicates correlation between the corresponding quadratures, and hence nonzero discord. We also apply this method to non-Gaussian states that are prepared by overlapping a statistical mixture of coherent and vacuum states on a beam splitter. We experimentally demonstrate this technique by verifying nonzero quantum discord in a bipartite Gaussian and certain non-Gaussian states.