Witnessing non-classicality of a quantum oscillator state by coupling it to a qubit

TL;DR

This paper introduces a new method to detect non-classical states of a quantum harmonic oscillator by coupling it to a qubit, avoiding the need for full state reconstruction and providing a clear criterion for non-classicality.

Contribution

The authors develop a novel witness operation that identifies non-classical oscillator states through qubit dynamics without requiring state tomography.

Findings

The method establishes a bound for classical states' evolution.

Violations of the bound indicate non-classicality.

The approach simplifies detection of quantum features in oscillator states.

Abstract

We propose a new witness operation for the non-classical character of a harmonic oscillator state. The method does not require state reconstruction. For all harmonic oscillator states that are classical, a bound is established for the evolution of a qubit which is coupled to the oscillator. Any violation of the bound can be rigorously attributed to the non-classical character of the initial oscillator state.