M. F. Cornelio, O. Jiménez Farías, F. F. Fanchini, I. Frerot, G. H. Aguilar, M. O. Hor-Meyll, M. C. de Oliveira, S. P. Walborn, A. O. Caldeira, P. H. Souto Ribeiro
The measurement problem is at the core of fundamental questions of quantum physics and the quantum- classical boundary. One way to approach these questions is through the process of decoherence. In this paradigm, a measurement apparatus A interacts initially with the system of interest S. The apparatus suffers de- coherence through contact with the environment that collapses A into some classical set of pointer states, which are not altered by the decoherence. This fact permits the apparatus to maintain correlations with the system, allowing an observer to retrieve information about S through A, despite the dissipative decoherence process. In this sense, the decoherence selects the pointer states of A, inducing a transition from quantum to classical states of the apparatus. The time scale associated with this transition is usually estimated by the decoherence half-life. In this work, we show that the classicality of the apparatus can be manifested at a distinct and well-defined time. This time corresponds to a non-analytical change in classical correlations between the system and apparatus, and is related to the sudden changes of the Quantum Discord. Using polarization entangled photon pairs, we demonstrate this behavior experimentally.
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http://arxiv.org/abs/1203.5068
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