Operational witnesses of non-classicality via Bell inequalities and contextuality
Candidate: Sanchit Srivastava
Supervisor: Shohini Ghose
Supervisor: Robert Mann
Location: QNC 2101
Abstract
This thesis investigates operational signatures of non-classicality in quantum systems, examining the relationship between Bell inequalities, contextuality tests, and discrete Wigner negativity across four case studies. The first analyzes multipartite entanglement and genuine multipartite nonlocality in multiqubit systems, deriving analytical expressions for Svetlichny inequality violations for generalized GHZ and maximal-slice states; the results indicate that the entanglement–nonlocality relationship depends on state structure rather than scalar entanglement measures alone. The second uses an optimized Bell inequality as a contextuality witness for the spin-1 quantum kicked top, revealing correlations between violation strength and the regular-versus-chaotic structure of the classical phase space. The third examines two qutrit Unruh–DeWitt detectors coupled to the Minkowski vacuum, showing that an initially noncontextual product state can develop contextual correlations through vacuum-mediated interactions, with contextuality onset coinciding with discrete Wigner negativity. The fourth constructs logical Bell inequalities for odd prime dimensions that connect single-qudit Wigner negativity to inequality violation. Throughout, the analysis highlights how different witnesses constrain different classes of classical models—locally causal hidden variables, noncontextual hidden variables, and positive Wigner representations—and that witness violations certify properties of observed statistics.