Quantum Process Nonclassicality

TL;DR

This paper introduces a new way to define and detect nonclassicality in quantum optical processes by using a process-specific quasiprobability distribution, enabling experimental verification of nonclassical behavior.

Contribution

It proposes a process-nonclassicality quasiprobability distribution to identify nonclassical quantum processes based on their action on coherent states.

Findings

The distribution's negativities indicate nonclassicality.

Derived a relation to predict output nonclassicality from input states.

Experimentally demonstrated the method with single-photon addition.

Abstract

We propose a definition of nonclassicality for a single-mode quantum-optical process based on its action on coherent states. If a quantum process transforms a coherent state to a nonclassical state, it is verified to be nonclassical. To identify nonclassical processes, we introduce a representation for quantum processes, called the process-nonclassicality quasiprobability distribution, whose negativities indicate nonclassicality of the process. Using this distribution, we derive a relation for predicting nonclassicality of the output states for a given input state. We experimentally demonstrate our method by considering the single-photon addition as a nonclassical process, and predicting nonclassicality of the output state for an input thermal state.