1,918 research outputs found
Smooth quantum-classical transition in photon subtraction and addition processes
Recently Parigi et al. [Science 317, 1890 (2007)] implemented experimentally
the photon subtraction and addition processes from/to a light field in a
conditional way, when the required operations were produced successfully only
upon the positive outcome of a separate measurement. It was verified that for a
low intensity beam (quantum regime) the bosonic annihilation operator does
indeed describe a single photon subtraction, while the creation operator
describes a photon addition. Nonetheless, the exact formal expressions for
these operations do not always reduce to these simple identifications, and in
this connection here we deduce the general superoperators for multiple photons
subtraction and addition processes and analyze the statistics of the resulting
states for classical field states having an arbitrary intensity. We obtain
closed analytical expressions and verify that for classical fields with high
intensity (classical regime) the operators that describe photon subtraction and
addition processes deviate significantly from simply annihilation and creation
operators. Complementarily, we analyze in details such a smooth
quantum-classical transition as function of beam intensity for both processes.Comment: 7 pages, 5 figures. To appear in Phys. Rev.
Three-body relativistic flux tube model from QCD Wilson-loop approach
First we review the derivation of the relativistic flux tube model for a
quark-antiquark system from Wilson area law as we have given in a preceding
paper. Then we extend the method to the three-quark case and obtain a
Lagrangian corresponding to a star flux tube configuration.
A Hamiltonian can be explicitly constructed as an expansion in or
in the string tension . In the first case it reproduces the Wilson loop
three-quark semirelativistic potential; in the second one, very complicated in
general, but it reproduces known string models for slowly rotating quarks.Comment: 14 pages, latex, uses elsart.sty, 2 figures available upon reques
Control of the geometric phase and pseudo-spin dynamics on coupled Bose-Einstein condensates
We describe the behavior of two coupled Bose-Einstein condensates in
time-dependent (TD) trap potentials and TD Rabi (or tunneling) frequency, using
the two-mode approach. Starting from Bloch states, we succeed to get analytical
solutions for the TD Schroedinger equation and present a detailed analysis of
the relative and geometric phases acquired by the wave function of the
condensates, as well as their population imbalance. We also establish a
connection between the geometric phases and constants of motion which
characterize the dynamic of the system. Besides analyzing the affects of
temporality on condensates that differs by hyperfine degrees of freedom
(internal Josephson effect), we also do present a brief discussion of a one
specie condensate in a double-well potential
(external Josephson effect).Comment: 1 tex file and 11 figures in pdf forma
Quantum statistical information contained in a semi-classical Fisher--Husimi measure
We study here the difference between quantum statistical treatments and
semi-classical ones, using as the main research tool a semi-classical,
shift-invariant Fisher information measure built up with Husimi distributions.
Its semi-classical character notwithstanding, this measure also contains
information of a purely quantal nature.
Such a tool allows us to refine the celebrated Lieb bound for Wehrl entropies
and to discover thermodynamic-like relations that involve the degree of
delocalization. Fisher-related thermal uncertainty relations are developed and
the degree of purity of canonical distributions, regarded as mixed states, is
connected to this Fisher measure as well.Comment: 9 pages, 3 figures; chenged conten
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Magnetic Properties and Interfacial Anisotropies of Pt/Co/AlO<inf>x</inf> Perpendicularly Magnetized Thin Films
The thin films of Pt/Co/AlOx, showing perpendicular magnetic anisotropy, were grown by magnetron sputtering with AlOx formed by the oxidation of thin Al layers using an oxygen atom source. Films were studied as a function of Pt thickness and Al oxidation, and films that showed full remanence and sharp switching coercivity were achieved. In order to prevent further oxidation of the interface in ambient conditions, we use a double Al growth and oxidation process. The magnetooptical Kerr effect and vibrating sample magnetometry were used to analyze these films. We find an effective perpendicular anisotropy of 2 × 106 erg/cm3, with the majority of the perpendicular anisotropy coming from the Pt/Co interface. From the sweep rate dependence on the coercivity, we are able to extract an activation volume of 4.3-0.5 × 10-18cm3, similar to other Co-based perpendicular systems.This research is funded by the European Community under the Seventh Framework Program ERC Contract No. 247368: 3SPIN. AB acknowledges DTA funding from the EPSRC
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