Deterministic generation of maximally discordant mixed states by dissipation

Entanglement can be considered as a special quantum correlation, but not the only kind. Even for a separable quantum system, nonclassical correlations are allowed to exist. Here we propose two dissipative schemes for generating a maximally correlated state of two qubits in the absence of quantum entanglement, which was proposed by Galve et al. [F. Galve, G. L. Giorgi, and R. Zambrini, Phys. Rev. A 83, 012102 (2011)]. These protocols take full advantage 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 the system. Moreover, since the target state is a mixed state, the performance of our method is evaluated by the definition of superfidelity 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.