Violation of Leggett-Garg inequalities for quantum-classical hybrids

Abstract

Violation of Leggett{Garg inequalities can serve as a signature of a failure of (macroscopic) realism. We investigate violation of the simplest Leggett{Garg inequality for a qubit coupled to an integer j spin (angular momentum). Such a system e ectively reveals quantum{classical hybrid behavior in the limit of large j values. We show that a maximal violation of the Leggett{ Garg inequality is larger for quantum{classical hybrids than for fully quantum systems.