41,180 research outputs found
Susceptibility of a two-level atom near an isotropic photonic band edge: transparency and band edge profile reconstruction
We discuss the necessary conditions for a two-level system in the presence of
an isotropic band edge to be transparent to a probe laser field. The two-level
atom is transparent whenever it is coupled to a reservoir constituted of two
parts - a flat and a non-flat density of modes representing a PBG structure. A
proposal on the reconstruction of the band edge profile from the experimentally
measured susceptibility is also presented.Comment: 15 pages, 3 figure
Characterization and quantification of symmetric Gaussian state entanglement through a local classicality criterion
A necessary and sufficient condition for characterization and quantification
of entanglement of any bipartite Gaussian state belonging to a special symmetry
class is given in terms of classicality measures of one-party states. For
Gaussian states whose local covariance matrices have equal determinants it is
shown that separability of a two-party state and classicality of one party
state are completely equivalent to each other under a nonlocal operation,
allowing entanglement features to be understood in terms of any available
classicality measure.Comment: 5 pages, 1 figure. Replaced with final published versio
Numerical study of a model for non-equilibrium wetting
We revisit the scaling properties of a model for non-equilibrium wetting
[Phys. Rev. Lett. 79, 2710 (1997)], correcting previous estimates of the
critical exponents and providing a complete scaling scheme. Moreover, we
investigate a special point in the phase diagram, where the model exhibits a
roughening transition related to directed percolation. We argue that in the
vicinity of this point evaporation from the middle of plateaus can be
interpreted as an external field in the language of directed percolation. This
analogy allows us to compute the crossover exponent and to predict the form of
the phase transition line close to its terminal point.Comment: 8 pages, 8 figure
Corrections to Finite Size Scaling in Percolation
A 1/L-expansion for percolation problems is proposed, where L is the lattice
finite length. The square lattice with 27 different sizes L = 18, 22 ... 1594
is considered. Certain spanning probabilities were determined by Monte Carlo
simulations, as continuous functions of the site occupation probability p. We
estimate the critical threshold pc by applying the quoted expansion to these
data. Also, the universal spanning probability at pc for an annulus with aspect
ratio r=1/2 is estimated as C = 0.876657(45)
Generation of Superposition States and Charge-Qubit Relaxation Probing in a Circuit
We demonstrate how a superposition of coherent states can be generated for a
microwave field inside a coplanar transmission line coupled to a single
superconducting charge qubit, with the addition of a single classical magnetic
pulse for chirping of the qubit transition frequency. We show how the qubit
dephasing induces decoherence on the field superposition state, and how it can
be probed by the qubit charge detection. The character of the charge qubit
relaxation process itself is imprinted in the field state decoherence profile.Comment: 6 pages, 4 figure
Unravelling the non-classicality role in Gaussian heat engines
At the heart of quantum thermodynamics lies a fundamental question about what
is genuine "quantum" in quantum heat engines. With the help of the
P-representability expression of classicality, the degree of non-classicality
of a bosonic thermal engine - a quantum heat engine consisting of a single
bosonic mode as a working substance coupled to a cold thermal and a hot
squeezed thermal bath - is quantified. For two specific protocols, i.e., a
quantum Otto and a generalized cycle, we show that the non-classicality is a
fundamental resource for genuinely quantum heat engines.Comment: 8 pages, 7 figure
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