181 research outputs found
Sudden Decoherence Transitions for Quantum Discord
We investigate the disappearance of discord in 2- and multi-qubit systems
subject to decohering influences. We formulate the computation of quantum
discord in terms of the generalized Bloch vector, which gives useful insights
on the time evolution of quantum coherence for the open system, particularly
the comparison of entanglement and discord. And we show that the analytical
calculation of the global geometric discord is NP-hard in the number of qubits.
We present an efficient numerical method to calculating the quantum discord for
a certain important class of multipartite states. In agreement with previous
work for 2-qubit cases, (Mazzola et al., Phys. Rev. Lett. 104, 200401 (2010)),
we find situations in which there is a sudden transition from classical to
quantum decoherence characterized by the discord remaining relatively robust
(classical decoherence) until a certain point from where it begins to decay
quickly whereas the classical correlation decays more slowly (quantum
decoherence). However, we find that as the number of qubits increases, the
chance of this kind of transition occurring becomes small.Comment: 15 pages, 2 figure
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