A simple test of quantumness for a single system

Abstract

We propose a simple test of quantumness which can decide whether for the given set of accessible experimental data the classical model is insufficient. Take two observables $A,B$ such that for any state $\psi$ their mean values satisfy $0\le <\psi |A|\psi >\le <\psi |B|\psi >\le 1$. If there exists a state $\varphi$ such that the second moments fulfill the inequality $<\varphi |A^2|\varphi >><\varphi |B^2|\varphi >$ then the system cannot be described by the classical probabilistic scheme. An example of an optimal triple $(A,B,\varphi )$ in the case of a qubit is given.

3 pages, no figures, corrected typos, text essentially amended

References in corpus (2)

• Microwave-induced thermal escape in Josephson junctions
• Rabi-type oscillations in a classical Josephson junction

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