A measure of physical reality

Abstract

From the premise that an observable is real after it is measured, we envisage a tomography-based protocol that allows us to propose a quantifier for the degree of indefiniteness of an observable given a quantum state. Then, we find that the reality of an observable can be inferred locally only if this observable is not quantumly correlated with an informer. In other words, quantum discord precludes Einstein's notion of separable realities. Also, by monitoring changes in the local reality upon measurements on a remote system, we are led to define a measure of nonlocality. Proved upper bounded by discordlike correlations and requiring indefiniteness as a basic ingredient, our measure signals nonlocality even for separable states, thus revealing nonlocal aspects that are not captured by Bell inequality violations.

6 pages, 2 figures, typos corrected, references added; accepted for publication in EPL

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• Quantifying Coherence
• Quantum Darwinism
• Quantum origins of objectivity
• How ψ-epistemic models fail at explaining the indistinguishability of quantum states
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• Signifying the Schrodinger cat in the context of testing macroscopic realism
• Uncertainty-Reality Complementarity and Entropic Uncertainty Relations
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• Correlating Local Quantum Reality with Causally Disconnected Choices
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