3,097 research outputs found
Quantum channels in random spin chains
We study the entanglement between pairs of qubits in a random
antiferromagnetic spin-1/2 chain at zero temperature. We show that some very
distant pairs of qubits are highly entangled, being almost pure Bell states.
Furthermore, the probability to obtain such spin pairs is proportional to the
chain disorder strenght and inversely proportional to the square of their
separation.Comment: v1: 4 pages, 2 eps figures; v2: discussion about the effect of
temperature added, v3: 1 eps figure added, enlarged discussions, 6 pages,
published versio
Holographic Kondo and Fano Resonances
We use holography to study a -dimensional Conformal Field Theory (CFT)
coupled to an impurity. The CFT is an gauge theory at large , with
strong gauge interactions. The impurity is an spin. We trigger an
impurity Renormalization Group (RG) flow via a Kondo coupling. The Kondo effect
occurs only below the critical temperature of a large- mean-field
transition. We show that at all temperatures , impurity spectral functions
exhibit a Fano resonance, which in the low- phase is a large-
manifestation of the Kondo resonance. We thus provide an example in which the
Kondo resonance survives strong correlations, and uncover a novel mechanism for
generating Fano resonances, via RG flows between -dimensional fixed
pointsComment: 5 pages + references, 6 figures; v2: discussion clarified, references
added; as accepted by PR
An improved model of vector mesons in holographic QCD
We analyze the sector of dimension-three vector meson operators in the "hard
wall" model of holographic QCD, including the vector and axial currents, dual
to gauge fields in the bulk, and the tensor operator
, dual to a two-form field satisfying a complex
self-duality condition. The model includes the effect of chiral symmetry
breaking on vector mesons, that involves a coupling between the dual gauge
field and the two-form field. We compute the leading logarithmic terms in the
operator product expansion of two-point functions and the leading
non-perturbative contribution to the tensor-vector correlator. The result is
consistent with the operator product expansion of QCD. We also study the
spectrum of vector mesons numerically.Comment: 19 page
Control of fluorescence in quantum emitter and metallic nanoshell hybrids for medical applications
We study the light emission from quantum emitter and double metallic
nanoshell hybrid systems. Quantum emitters act as local sources which transmit
their light efficiently due to a double nanoshell near field. The double
nanoshell consists a dielectric core and two outer nanoshells
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