149 research outputs found
Binding entanglement channels
We define the binding entanglement channel as the quantum channel through
which quantum information cannot be reliably transmitted, but which can be used
to share bound entanglement. We provide a characterization of such class of
channels. We also show that any bound entangled state can be used to
construction of the map corresponding the binding entanglement channel.Comment: RevTeX, 5 pages, submitted to special issue of J. Mod. Op
Quantum-state transfer in spin chains via isolated resonance of terminal spins
We propose a quantum-state transfer protocol in a spin chain that requires
only the control of the spins at the ends of the quantum wire. The protocol is
to a large extent insensitive to inhomogeneity caused by local magnetic fields
and perturbation of exchange couplings. Moreover, apart from the free evolution
regime, it allows one to induce an adiabatic spin transfer, which provides the
possibility of performing the transfer on demand. We also show that the amount
of information leaking into the central part of the chain is small throughout
the whole transfer process (which protects the information sent from being
eavesdropped) and can be controlled by the magnitude of the external magnetic
field.Comment: 7 pages, 5 figures. Published versio
The decay of quantum correlations between quantum dot spin qubits and the characteristics of its magnetic field dependence
We address the question of the role of quantum correlations beyond
entanglement in context of quantum magnetometry. To this end, we study the
evolution of the quantum discord, measured by the rescaled discord, of two
electron-spin qubits interacting with an environment of nuclear spins via the
hyperfine interaction. We have found that depending on the initial state the
evolution can or cannot display indifferentiability points in its
time-evolution (due to the energy conservation law), as well as non-trivial
dependence on inter-qubit phase. Furthermore, we show that for initial Bell
states, quantum correlations display a strong magnetic-field sensitivity which
can be utilized for decoherence-driven measurements of the external magnetic
field. The potential discord-based measurement is sensitive to a wider range of
magnetic field values than the entanglement-based measurement. In principle,
entanglement is not a necessary resource for reliable decoherence-driven
measurement, while the presence of quantum correlations beyond entanglement is.Comment: 9 pages, 6 figure
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