Zero quantum discord for Markovian bipartite systems

Abstract

Quantum discord measures the total non-classical correlations in a composite quantum system.
As a possible resource for the classically non-achievable tasks, amount of quantum discord is crucial for
efficient performance of the quantum technology tasks. Zero discord means the absence of the required
resources. For a wide class of the bipartite open quantum systems, initial nonzero discord is known
practically never goes to zero, except asymptotically. However, if initial discord equals zero, there remains
the possibility to remain zero for the finite time intervals for certain Markovian models of open systems–that
we call Markovian classicality. In this paper we search for the models that allow for Markovian classicality.
We point out a general model that represents a matter-of-principle formal proof, i.e. a sufficient condition for
the, otherwise not obvious, existence of Markovian classicality. Physical relevance of the model is twofold.
First, the model is in intimate relation to the topics of quantum information locality, quantum discord
saturation and quantum decorrelation. Second, the model is of the general physical interest. It pertains to
a specific structure (decomposition into parts/subsystems) of a composite system, not to a special kind of
composite system. Being a characteristic of a structure, by definition, the model of Markovian classicality
is not a model of sudden death of discord. We emphasize wide-range implications of our results.