# Probing nonclassicality under spontaneous decay

## TL;DR

This paper explores the nonclassical behavior of a qubit under spontaneous decay by exactly analyzing Leggett-Garg inequality violations in non-Markovian environments, revealing quantum correlations over time.

## Contribution

It provides an exact calculation of two-time correlation functions for a decaying qubit in non-Markovian environments, extending beyond the Born-Markov approximation.

## Key findings

- Violations of LGI indicate nonclassicality in the system.
- Exact correlation functions are obtained for a wide parameter range.
- Results demonstrate nonclassical behavior persists under various environmental conditions.

## Abstract

We investigate the nonclassicality of an open quantum system using Leggett-Garg inequality (LGI) which test the correlations of a single system measured at different times. Violation of LGI implies nonclassical behavior of the open system. We investigate the violation of the Leggett-Garg inequality for a two level system (qubit) spontaneously decaying under a general non-Markovian dissipative environment. Our results are exact as we have calculated the two-time correlation functions exactly for a wide range of system-environment parameters beyond Born-Markov regime.