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Violation of entropic Leggett-Garg inequality in nuclear spins

Katiyar, Hemant and Shukla, Abhishek and Rao, Rama Koteswara K and Mahesh, TS (2013) Violation of entropic Leggett-Garg inequality in nuclear spins. In: Physical Review A, 87 (5). 052102_1-052102_5.

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Official URL: http://dx.doi.org/10.1103/PhysRevA.87.052102

Abstract

We report an experimental study of recently formulated entropic Leggett-Garg inequality (ELGI) by Usha Devi et al. Phys. Rev. A 87, 052103 (2013)]. This inequality places a bound on the statistical measurement outcomes of dynamical observables describing a macrorealistic system. Such a bound is not necessarily obeyed by quantum systems, and therefore provides an important way to distinguish quantumness from classical behavior. Here we study ELGI using a two-qubit nuclear magnetic resonance system. To perform the noninvasive measurements required for the ELGI study, we prepare the system qubit in a maximally mixed state as well as use the ``ideal negative result measurement'' procedure with the help of an ancilla qubit. The experimental results show a clear violation of ELGI by over four standard deviations. These results agree with the predictions of quantum theory. The violation of ELGI is attributed to the fact that certain joint probabilities are not legitimate in the quantum scenario, in the sense they do not reproduce all the marginal probabilities. Using a three-qubit system, we also demonstrate that three-time joint probabilities do not reproduce certain two-time marginal probabilities.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Physical Society.
Department/Centre: Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility)
Division of Physical & Mathematical Sciences > Physics
Depositing User: Francis Jayakanth
Date Deposited: 21 Jun 2013 05:23
Last Modified: 21 Jun 2013 05:23
URI: http://eprints.iisc.ac.in/id/eprint/46687

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