# A New Mechanism of Open System Evolution and Its Entropy Using Unitary Transformations in Noncomposite Qudit Systems

## TL;DR

This paper introduces a novel approach to model open quantum system evolution using unitary transformations in noncomposite qudit systems, specifically employing qutrits to analyze qubit channels and their entropy.

## Contribution

It presents a new method to study open system dynamics via unitary transformations in qutrit systems, enabling analysis of quantum channels and entropy in a unified framework.

## Key findings

- Developed a unitary transformation-based method for open system evolution.
- Analyzed phase damping and spontaneous-emission quantum channels.
- Addressed experimental realization and entropy characteristics.

## Abstract

The evolution of an open system is usually associated with the interaction of the system with an environment. A new method to study the open-type system evolution of a qubit (two-level atom) state is established. This evolution is determined by a unitary transformation applied to the qutrit (three-level atom) state, which defines the qubit subsystems. This procedure can be used to obtain different qubit quantum channels employing unitary transformations into the qutrit system. In particular, we study the phase damping and spontaneous-emission quantum channels. In addition, we mention a proposal for quasiunitary transforms of qubits, in view of the unitary transform of the total qutrit system. The experimental realization is also addressed. The probability representation of the evolution and its information-entropic characteristics are considered.