Direct observation of any two-point quantum correlation function

Abstract

The existence of noncompatible observables in quantum theory makes a direct operational interpretation of two-point correlation functions problematic. Here we challenge such a view by explicitly constructing a measuring scheme that, independently of the input state $\rho$ and observables $A$ and $B$, performs an unbiased optimal estimation of the two-point correlation function $\mathrm{Tr}[A\rho B]$. This shows that, also in quantum theory, two-point correlation functions are as operational as any other expectation value. A very simple probabilistic implementation of our proposal is presented.

5 + 3 pages, 4 figures

Cited by in corpus (2)

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