225 research outputs found
Optimal 1->M universal quantum cloning via spin networks
We present a scheme that transform 1 qubit to M identical copies with optimal
fidedelity via free dynamical evolution of spin star networks. We show that the
Heisenberg XXZ coupling can fulfill the challenge. The initial state of the
copying machine and the parameters of the spin Hamiltonian are discussed in
detail. Furthermore we have proposed a feasible method to prepare the initial
state of the copying machine.Comment: 4 pages, 2 figure
Critical surface band gap of repulsive Casimir interaction between three dimensional topological insulators at finite temperature
We generalize the calculation of Casimir interaction between topological
insulators with opposite topological magnetoelectric polarizabilities and
finite surface band gaps to finite Temperature cases. We find that finite
temperature quantitatively depress the repulsive peak and enlarge the critical
surface gap for repulsive Casimir force. However the universal property
is still valid for various oscillation strength, temperature
region and topological magnetoelectric polarizabilities.Comment: 7 pages, 4 figure
Surface Spectral Function of Momentum-dependent Pairing Potentials in a Topological Insulator: Application to CuBiSe
We propose three possible momentum-dependent pairing potentials for candidate
of topological superconductor (for example CuBiSe), and calculate
the surface spectral function and surface density of state with these pairing
potentials. We find that the first two can give the same spectral functions as
the fully-gapped and node-contacted pairing potentials given in [Phys. Rev.
Lett. 105, 097001], and that the third one can obtain topological non-trivial
case which exists flat Andreev bound state and preserves the rotation
symmetry. We hope our proposals and results be judged by future experiment.Comment: 5 pages, 3 figure
Features and flaws of a contact interaction treatment of the kaon
Elastic and semileptonic transition form factors for the kaon and pion are
calculated using the leading-order in a global-symmetry-preserving truncation
of the Dyson-Schwinger equations and a momentum-independent form for the
associated kernels in the gap and Bethe-Salpeter equations. The computed form
factors are compared both with those obtained using the same truncation but an
interaction that preserves the one-loop renormalisation-group behaviour of QCD
and with data. The comparisons show that: in connection with observables
revealed by probes with |Q^2|<~ M^2, where M~0.4GeV is an infrared value of the
dressed-quark mass, results obtained using a symmetry-preserving regularisation
of the contact-interaction are not realistically distinguishable from those
produced by more sophisticated kernels; and available data on kaon form factors
do not extend into the domain whereupon one could distinguish between the
interactions. The situation is different if one includes the domain Q^2>M^2.
Thereupon, a fully consistent treatment of the contact interaction produces
form factors that are typically harder than those obtained with QCD
renormalisation-group-improved kernels. Amongst other things also described are
a Ward identity for the inhomogeneous scalar vertex, similarity between the
charge distribution of a dressed-u-quark in the K^+ and that of the
dressed-u-quark in the pi^+, and reflections upon the point whereat one might
begin to see perturbative behaviour in the pion form factor. Interpolations of
the form factors are provided, which should assist in working to chart the
interaction between light-quarks by explicating the impact on hadron properties
of differing assumptions about the behaviour of the Bethe-Salpeter kernel.Comment: 17 pages, 9 figures, 4 table
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