Bounds on relative entropy of entanglement for multi-party systems
Journal of Physics A: Mathematical and General 34:35 (2001) 6997-7002
Abstract:
We present upper and lower bounds to the relative entropy of entanglement of multi-party systems in terms of the bi-partite entanglements of formation and distillation and entropies of various subsystems. We point out implications of our results to the local reversible convertibility of multi-party pure states and discuss their physical basis in terms of deleting information.Classical, quantum and total correlations
Journal of Physics A: Mathematical and General 34:35 (2001) 6899-6905
Abstract:
We discuss the problem of separating consistently the total correlations in a bipartite quantum state into a quantum and a purely classical part. A measure of classical correlations is proposed and its properties are explored.Security of EPR-based quantum cryptography against incoherent symmetric attacks
Journal of Physics A: Mathematical and General 34:35 (2001) 6913-6918
Abstract:
We investigate a new strategy for incoherent eavesdropping in Ekert's entanglement-based quantum key distribution protocol. We show that under certain assumptions of symmetry the effectiveness of this strategy reduces to that of the original single-qubit protocol of Bennett and Brassard.Subsystem purity as an enforcer of entanglement.
Phys Rev Lett 87:5 (2001) 050401
Abstract:
We show that entanglement can always arise in the interaction of an arbitrarily large system in any mixed state with a single qubit in a pure state. This small initial purity is enough to enforce entanglement even when the total entropy is close to maximum. We demonstrate this feature using the Jaynes-Cummings interaction of a two-level atom in a pure state with a field in a thermal state at an arbitrarily high temperature. We find the time and temperature variation of a lower bound on the amount of entanglement produced and study the classical correlations quantified by the mutual information.Natural thermal and magnetic entanglement in the 1D Heisenberg model.
Phys Rev Lett 87:1 (2001) 017901