Pinja Haikka, Sabrina Maniscalco
We study the dynamics of quantum discord shared by two qubits in local dephasing reservoirs. It is known that discord may be unaffected by noise for a finite time, followed by a sudden transition from classical to quantum decoherence. In this Letter, using an exact noise model, we unveil a class of initial states with completely time invariant discord, that is, discord frozen to a positive value for arbitrarily long times. We connect this phenomenon to non-Markovian properties of the dephasing noise and propose a physical set-up where time invariant discord could be observed. Finally, we prove that Markovian pure dephasing models are inconsistent with all super-Ohmic environments.
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http://arxiv.org/abs/1203.6469
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