# Quantum Decoherence in System-Bath Interferometry

## TL;DR

This study investigates how a quantum harmonic oscillator in an interferometer interacts with its environment, revealing that some quantum properties persist despite decoherence, challenging the classicalization notion in quantum theory.

## Contribution

It demonstrates that thermalization does not fully classicalize the system and introduces an entropy measure to describe bath influence, providing new insights into quantum decoherence.

## Key findings

- Quantum properties persist despite decoherence effects.
- Thermalization does not fully classicalize the system.
- High frequency and low temperature conditions reveal residual quantum coherence.

## Abstract

In this paper, we study a quantum harmonic oscillator in a Mach-Zehnder-type interferometer which interacts with an environment, including electromagnetic oscillators. By solving the Lindblad master equation, we calculate the resulted interference pattern of the system. Interestingly, we show that even if one considers the decoherence effect, the system will keep some of its quantum properties. Indeed, the thermalization process does not completely leave the system in a classical state and the system keeps some of its coherency. Such an effect can be detected, when the frequency of the central system is high and the temperature is low, even with zero phase angle. This observation makes the quantum-to-classical transition remain as a vague notion in decoherence theory. By introducing an entropy measure, we express the influence of the bath as a maximization of system's entropy instead of classicalization of the state.