Universal nonclassicality witnesses for harmonic oscillators

TL;DR

This paper introduces a universal set of nonclassicality witnesses for harmonic oscillators, enabling the detection of nonclassical states through measurable expectation values, with potential for experimental implementation.

Contribution

It develops a universal framework for nonclassicality detection using filters, providing explicit operators and demonstrating practical applicability.

Findings

Universal witnesses parameterized by three real numbers

Explicit operator expressions derived for the witnesses

Application demonstrated with a nontrivial example

Abstract

It is shown that a nonclassicality witness, whose expectation value can be measured for all quantum states, can be constructed from every nonclassicality filter. This finding leads to a set of universal witnesses, parameterized by only three real numbers, for the detection of nonclassicality of any quantum state of a harmonic oscillator. An explicit operator expression is given for such a universal witness. The application of the witnesses is demonstrated for a nontrivial example, and its experimental measurement is briefly considered.