Conditions for Quantum Violation of Macroscopic Realism

Author(s): J. Kofler, Č. Brukner

Journal: Physical Review Letters

Volume: 101

Page(s): 090403

Year: 2008

DOI Number: 10.1103/PhysRevLett.101.090403

Link: Link to publication


Why do we not experience a violation of macroscopic realism in everyday life. Normally, no violation can be seen either because of decoherence or the restriction of coarse-grained measurements, transforming the time evolution of any quantum state into a classical time evolution of a statistical mixture. We find the sufficient condition for these classical evolutions for spin systems under coarse-grained measurements. However, there exist ‘‘nonclassical’’ Hamiltonians whose time evolution cannot be understood classically, although at every instant of time the quantum state appears as a classical mixture. We suggest that such Hamiltonians are unlikely to be realized in nature because of their high computational complexity.


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