# Deterministic generation of maximally discordant mixed states by dissipation

## TL;DR

This paper presents two dissipative schemes using atom-cavity interactions to generate maximally discordant, non-entangled mixed states of two qubits, achieving high fidelity with current quantum optical technology.

## Contribution

The authors propose novel dissipative protocols for creating maximally quantum dissonant states without entanglement, utilizing phase control and lossy cavity systems.

## Key findings

- Achieve super-fidelity over 99% with current cavity QED parameters.
- Guarantee the target state as the unique steady state within a specific subspace.
- Demonstrate all required Lindblad dynamics for the state preparation.

## Abstract

Entanglement can be considered as a special quantum correlation, but not the only kind. Even for a separable quantum system, it is allowed to exist non-classical correlations. Here we propose two dissipative schemes for generating a maximally correlated state of two qubits in the absence of quantum entanglement, which was raised by [F. Galve, G. L. Giorgi, and R. Zambrini, {\color{blue}Phys. Rev. A {\bf 83}, 012102 (2011)}]. These protocols take full advantages of the interaction between four-level atoms and strongly lossy optical cavities. In the first scenario, we alternatively change the phases of two classical driving fields, while the second proposal introduces a strongly lossy coupled-cavity system. Both schemes can realize all Lindblad terms required by the dissipative dynamics, guaranteeing the maximally quantum dissonant state to be the unique steady state for a certain subspace of system. Moreover, since the target state is a mixed state, the performance of our method is evaluated by the definition of super-fidelity $G(\rho_{1},\rho_{2})$, and the strictly numerical simulations indicate that fidelity outstripping $99\%$ of the quantum dissonant state is achievable with the current cavity quantum electrodynamics parameters.