277 research outputs found
Dephasing of electron spin qubits due to their interaction with nuclei in quantum dots
Coherence of spins of electrons confined in III-V quantum dots is strongly
affected by their hyperfine interaction with the nuclei. In this paper an
introduction to this subject will be given. Some theoretical approaches to the
problem will be outlined. Most attention will be given to the Quasi-Static Bath
Approximation, to the cluster expansion theories of dephasing due to the
nuclear dynamics induced by the dipolar interactions (spectral diffusion), and
to the effective Hamiltonian based theory of dephasing due to
hyperfine-mediated interactions. The connections between the theoretical
results and various experiments will be emphasized.Comment: An invited review, Proceedings of 39th "Jaszowiec" International
School and Conference on the Physics of Semiconductors, Krynica 2010, Poland.
Journal version available online at
http://przyrbwn.icm.edu.pl/APP/ABSTR/119/a119-5-2.htm
The relation between the quantum discord and quantum teleportation: the physical interpretation of the transition point between different quantum discord decay regimes
We study quantum teleportation via Bell-diagonal mixed states of two qubits
in the context of the intrinsic properties of the quantum discord. We show that
when the quantum-correlated state of the two qubits is used for quantum
teleportation the character of the teleportation efficiency changes
substantially depending on the Bell-diagonal-state parameters, which can be
seen when the worst-case-scenario or best-case-scenario fidelity is studied.
Depending on the parameter range, one of two types of single qubit states is
hardest/easiest to teleport. The transition between these two parameter ranges
coincides exactly with the transition between the range of classical
correlation decay and quantum correlation decay characteristic for the
evolution of the quantum discord. The correspondence provides a physical
interpretation for the prominent feature of the decay of the quantum discord.Comment: 6 page
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