Necessary and sufficient conditions for macroscopic realism from quantum mechanics

Lucas Clemente and Johannes Kofler
Phys. Rev. A 91, 062103 – Published 4 June 2015

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 nonclassical 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 measures and the system Hamiltonian. We argue that this leads to a suitable definition of “classical” measurements and Hamiltonians, and we apply our formalism to some generic coarse-grained quantum measurements.

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  • Received 6 March 2015

DOI:https://doi.org/10.1103/PhysRevA.91.062103

©2015 American Physical Society

Authors & Affiliations

Lucas Clemente* and Johannes Kofler

  • Max Planck Institute of Quantum Optics, Hans-Kopfermann Strasse 1, 85748 Garching, Germany

  • *lucas.clemente@mpq.mpg.de
  • johannes.kofler@mpq.mpg.de

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Issue

Vol. 91, Iss. 6 — June 2015

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