One of the defining differences between classical and quantum systems is how measurements affect them. Here, we compare approaches contextuality discord in capturing correlations special classes two-qubit states, demonstrating that although non-discordant states are non-contextual, discordant not always contextual.

In this Letter we exploit the recently solved conjecture on the bosonic minimum output entropy to show the optimality of Gaussian discord, so that the computation of quantum discord for bipartite Gaussian states can be restricted to local Gaussian measurements. We prove such optimality for a large family of Gaussian states, including all two-mode squeezed thermal states, which are the most typi...

Linde’s proposal of a Euclidean path integral with the “wrong” sign of Euclidean action is often identified with the tunneling proposal for the wave function of the universe. However, the two proposals are in fact quite different. I illustrate the difference and point out that recent criticism by Hawking and Turok does not apply to the tunneling proposal. The debate about the form of the wave f...

D. Cavalcanti,1 L. Aolita,2 S. Boixo,3 K. Modi,1 M. Piani,4 and A. Winter1,5 1Centre for Quantum Technologies, National University of Singapore, Singapore 117542 2ICFO-Institut de Ciéncies Fotóniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain 3Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125, USA 4Institute for Quantum...

Quantum discord was proposed as an information theoretic measure of the “quantumness” of correlations. I show that discord determines the difference between the efficiency of quantum and classical Maxwell’s demons in extracting work from collections of correlated quantum systems. Information has an energetic value: It can be converted into work. Maxwell’s demon was introduced into thermodynamic...

In this article, by considering Bell-diagonal two-qubit initial states under local dynamics generated by the Phase Damping, Bit Flip, Phase Flip, BitPhase Flip, and Depolarizing channels, we report some elegant direct-dynamical relations between geometric measures of Entanglement and Discord. The complex scenario appearing already in this simplified case study indicates that a similarly simple ...

Chee Kong Lee,1,* Leong Chuan Kwek,1,2 and Jianshu Cao3 1Centre for Quantum Technologies, National University of Singapore, 117543 Singapore 2National Institute of Education and Institute of Advanced Studies, Nanyang Technological University, 637616 Singapore 3Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA (Received 7 August 2011; published 1...

Quantum discord as a measure of the quantum correlations cannot be easily computed for most of density operators. In this paper, we present a measure of the total quantum correlations that is operationally simple and can be computed effectively for an arbitrarymixed state of amultipartite system.Themeasure is based on the coherence vector of the party whose quantumness is investigated as well a...