Necessary and sufficient conditions for macroscopic realism from quantum mechanics

Abstract

Macroscopic realism, the classical world view that macroscopic objects exist independently of and are not influenced by measurements, is usually tested using Leggett-Garg inequalities. Recently, another necessary condition called no-signaling in time (NSIT) has been proposed as a witness for non-classical behavior. In this paper, we show that a combination of NSIT conditions is not only necessary but also sufficient for a macrorealistic description of a physical system. Any violation of macroscopic realism must therefore be witnessed by a suitable NSIT condition. Subsequently, we derive an operational formulation for NSIT in terms of positive operator-valued measurements and the system Hamiltonian. We argue that this leads to a suitable definition of "classical" measurements and Hamiltonians, and apply our formalism to some generic coarse-grained quantum measurements.

10 pages, published version

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Cited by in corpus (8)

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• Leggett-Garg tests of macrorealism: checks for non-invasiveness and generalizations to higher-order correlators
• Leggett-Garg test of macrorealism using indefinite causal order of measurements
• Reality, Causality, and Quantum Theory
• Lüders bounds of Leggett-Garg inequalities, $\mathcal{P}\mathcal{T}$- symmetric evolution and arrow-of-time
• Quantum violations of Lüders bound Leggett-Garg inequalities for quantum channel
• Operational quasiprobabilities for continuous variables