2,426 research outputs found
Two-mode entanglement in two-component Bose-Einstein condensates
We study the generation of two-mode entanglement in a two-component
Bose-Einstein condensate trapped in a double-well potential. By applying the
Holstein-Primakoff transformation, we show that the problem is exactly solvable
as long as the number of excitations due to atom-atom interactions remains low.
In particular, the condensate constitutes a symmetric Gaussian system, thereby
enabling its entanglement of formation to be measured directly by the
fluctuations in the quadratures of the two constituent components [Giedke {\it
et al.}, Phys. Rev. Lett. {\bf 91}, 107901 (2003)]. We discover that
significant two-mode squeezing occurs in the condensate if the interspecies
interaction is sufficiently strong, which leads to strong entanglement between
the two components.Comment: 22 pages, 4 figure
Entanglement between atomic condensates in an optical lattice: effects of interaction range
We study the area-dependent entropy and two-site entanglement for two state
Bose-Einstein condensates in a 2D optical lattice. We consider the case where
the array of two component condensates behave like an ensemble of spin-half
particles with the interaction to its nearest neighbors and next nearest
neighbors. We show how the Hamiltonian of their Bose-Einstein condensate
lattice with nearest-neighbor and next-nearest-neighbor interactions can be
mapped into a harmonic lattice. We use this to determine the entropy and
entanglement content of the lattice.Comment: 5 pages, 3 figures, title change
Analysis of measurement errors for a superconducting phase qubit
We analyze several mechanisms leading to errors in a course of measurement of
a superconducting flux-biased phase qubit. Insufficiently long measurement
pulse may lead to nonadiabatic transitions between qubit states and
, before tunneling through a reduced barrier is supposed to distinguish
the qubit states. Finite (though large) ratio of tunneling rates for these
states leads to incomplete discrimination between and .
Insufficiently fast energy relaxation after the tunneling of state may
cause the repopulation of the quantum well in which only the state is
supposed to remain. We analyze these types of measurement errors using
analytical approaches as well as numerical solution of the time-dependent
Schr\"{o}dinger equation.Comment: 14 pages, 14 figure
Another proof of Gell-Mann and Low's theorem
The theorem by Gell-Mann and Low is a cornerstone in QFT and zero-temperature
many-body theory. The standard proof is based on Dyson's time-ordered expansion
of the propagator; a proof based on exact identities for the time-propagator is
here given.Comment: 5 page
Neutron beta decay in effective field theory
Radiative corrections to the lifetime and angular correlation coefficients of
neutron beta-decay are evaluated in effecitive field theory. We also evaluate
the lowest order nucleon recoil corrections, including weak-magnetism. Our
results agree with those of the long-range and model-independent part of
previous calculations. In an effective theory the model-dependent radiative
corrections are replaced by well-defined low-energy constants. The effective
field theory allows a systematic evaluation of higher order corrections to our
results to the extent that the relevant low-energy constants are known.Comment: 13 pages, 1 figure; two references added, minor correctio
A Review of Rare Pion and Muon Decays
After a decade of no measurements of pion and muon rare decays, PIBETA, a new
experimental program is producing its first results. We report on a new
experimental study of the pion beta decay, Pi(+) -> Pi(0) e(+) Nu, the Pi(e2
gamma) radiative decay, Pi(+) -> e(+) Nu Gamma, and muon radiative decay, Mu ->
e Nu Gamma. The new results represent four- to six-fold improvements in
precision over the previous measurements. Excellent agreement with Standard
Model predictions is observed in all channels except for one kinematic region
of the Pi(e2 gamma) radiative decay involving energetic photons and
lower-energy positrons.Comment: 10 pages, 6 figures, 2 tables, invited talk presented at MESON 2004,
8th Int'l. Workshop on Meson Production, Properties and Interaction, Krakow,
Poland 4-8 June 200
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