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
Abstract:
We investigate the entanglement between any two spins in a one dimensional Heisenberg chain as a function of temperature and the external magnetic field. We find that the entanglement in an antiferromagnetic chain can be increased by increasing the temperature or the external field. Increasing the field can also create entanglement between otherwise disentangled spins. This entanglement can be confirmed by testing Bell's inequalities involving any two spins in the solid.Geometric quantum computation with Josephson qubits
Physica C: Superconductivity and its Applications 352:1-4 (2001) 110-112
Abstract:
The quest for large scale integrability and flexibility has stimulated an increasing interest in designing quantum computing devices. A proposal based on small-capacitance Josephson junctions in the charge regime in which quantum gates are implemented by means of adiabatic geometric phases was discussed. The proposed works, are in the charge regime where the qubit is realized by two nearly degenerate charge states of a single electron box.Remote information concentration using a bound entangled state.
Phys Rev Lett 86:2 (2001) 352-355