Quantum Coherence Versus Non-Classical Correlations in Optomechanics

Coherence arises from the superposition principle, where it plays a central role in quantum mechanics. In [Phys.Rev.Lett.114,210401(2015)], it has been shown that the freezing phenomenon of quantum correlations beyond entanglement, is intimately related to the freezing of quantum coherence (QC). In this paper, we compare the behaviour of entanglement and quantum discord with quantum coherence in two di erent subsystems (optical and mechanical). We use respectively the en-tanglement of formation (EoF) and the Gaussian quantum discord (GQD) to quantify entanglement and quantum discord. Under thermal noise and optomechanical coupling e ects, we show that EoF, GQD and QC behave in the same way. Remarkably, when entanglement vanishes, GQD and QC re-main almost una ected by thermal noise, keeping non zero values even for high temperature, which in concordance with [Phys.Rev.Lett.114,210401(2015)]. Also, we nd that the coherence associated with the optical subsystem are more robustagainst thermal noisethan those of the mechanical subsystem. Our results con rm that optomechanical cavities constitute a powerful resource of QC.
Comment: 9 figures, 15 pages