Time evolution of quantum correlations induced by atomic state superpositions

Abstract

In this article, we study the time evolution of Gaussian quantum correlations induced by the superposition of atomic states. Photon-based quantum information and communication are powerful and suitable because the relevant physical mechanisms, the high combination rate of photons, and the sources of coherence can be understood and easily modeled. To this end, coupled photon pairs produced by coherent superposition of atomic states in an atomic laser and influences of spontaneous atomic decay due to vacuum field fluctuations have been considered. The dynamics of the quantum system leads to temporal quantum correlations such as quantum discord, quantum entanglement, and quantum steering, which are treated by the density operator approach. It was found that the generated photon pairs are completely in a separable state in the initial phase of the dynamical processes. The quantum coherences must be given sufficient time to generate quantum correlations that saturate after very short time scales. The strength of these quantum correlations has been improved by increasing the number of superposed atoms per unit of time. In particular, two-way quantum steering, which is a guarantee for the existence of quantum discord and quantum entanglement, can be achieved by increasing the atom injection rate from 10 kHz to 100 kHz when the probability of finding atoms in the excited state is 45%.