"The existence of a sharp transition between classical and quantum loss of correlations in a composite system is a remarkable feature of the dynamics of composite open quantum system that was up to now unknown. The existence of a finite time interval during which quantum correlations initially present in the state do not decay in the presence of decoherence opens a series of interesting questions. Is it possible to exploit the class of initial states displaying such a property to perform quantum computa- tion or communication tasks without any disturbance from the noisy environment for long enough intervals of time? Which is the most general class of states and of open quantum systems exhibiting a sudden transition from classical to quantum decoherence? Finally, and perhaps most importantly, which are the physical mechanisms that forbid the loss of quantum correlations at the initial times and that allow only quantum correlations to be lost after the transition time t"? We believe that the transition from classical to quantum decoherence presented in this Letter and very recently confirmed experimentally [25] will shed new light on one of the most fundamental and fascinating aspects of quantum theory."

PHYSICAL REVIEW LETTERS week ending PRL 104, 200401 (2010) 21 MAY 2010

Sudden Transition between Classical and Quantum Decoherence

L. Mazzola,* J. Piilo,and S. ManiscalcoTurku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turun yliopisto, Finland

(Received 3 December 2009; revised manuscript received 30 January 2010; published 17 May 2010)