Quantum Non-locality, Quantum Contextuality and Marco-Realism

Saha, Debashis (2014) Quantum Non-locality, Quantum Contextuality and Marco-Realism. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

The descriptions of the quantum realm and the macroscopic classical world di�er signi �cantly not only in their mathematical formulations, but also in their foundational concepts and philosophical consequences. The assumptions of local realism, non-contextuality and macroscopic realism (macro-realism) along with the quantum mechanical violations of these assumptions are discussed. A complete generalization is provided of Wigner's argument inferring quantum nonlocality, originally restricted for the EPR-Bohm entangled state, based on assuming joint probability distributions for all the relevant dichotomic observables. Such Generalized Wigner Inequality (GWI) turns out to be the N-partite local realist inequality which is violated by quantum mechanics for all pure entangled states for any N. We then exploit the non-trivial manifestation of quantum non-locality via local contextuality on three qubit system. Here, we propose an experimental scheme to realize this feature by deriving a new local realist inequality. The way quantum entanglement can be used for global contextual value assigning is discussed in a quantum pseudo-telepathy game. In the second part of this report, we formulate Leggett-Garg inequality (LGI) in terms of joint probability and demonstrate its quantum mechanical violation for two state oscillation, which is initial state dependent, unlike the case of standard LGI. It has been shown that, the newly formulated LGI reveals robustness against unsharp measurement for testing compatibility between macro-realism and quantum mechanics. Finally we show that, the recently proposed No-signaling in time condition, contradicts with quantum mechanical predictions for any degree of unsharpness in measurement.

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