756 research outputs found
Many-particle entanglement with Bose--Einstein condensates
We propose a method to produce entangled states of several particles starting
from a Bose-Einstein condensate. In the proposal, a single fast pulse
is applied to the atoms and due to the collisional interaction, the subsequent
free time evolution creates an entangled state involving all atoms in the
condensate. The created entangled state is a spin-squeezed state which could be
used to improve the sensitivity of atomic clocks.Comment: 4 pages. Minor modification
A quantum beam splitter for atoms
An interferometric method is proposed to controllably split an atomic
condensate in two spatial components with strongly reduced population
fluctuations. All steps in our proposal are in current use in cold atom
laboratories, and we show with a theoretical calculation that our proposal is
very robust against imperfections of the interferometer.Comment: 6 pages, 3 figures, revtex
An outbreak of salmonellosis in Denmark caused by pork from a single slaughterhouse
Due to a rise in the endemic level of Salmonella Typhimurium infections in humans in Funen county, an outbreak of this serotype was discovered in the first week of September 1996. During the outbreak period (28 August - 14 October 1996) approximately 170 culture confirmed cases were registered at Statens Serum Institut. Almost all isolates were of phage type 12, which is frequently found in pork in Denmark - about 60% of S. Typhimurium isolates from pork are of DT 12 (Anon., 1997)
Environmental constraints on Holocene cold‐water coral reef growth off Norway: Insights from a multiproxy approach
Entanglement and spin squeezing in the two-atom Dicke model
We analyze the relation between the entanglement and spin-squeezing parameter
in the two-atom Dicke model and identify the source of the discrepancy recently
reported by Banerjee and Zhou et al that one can observe entanglement without
spin squeezing. Our calculations demonstrate that there are two criteria for
entanglement, one associated with the two-photon coherences that create
two-photon entangled states, and the other associated with populations of the
collective states. We find that the spin-squeezing parameter correctly predicts
entanglement in the two-atom Dicke system only if it is associated with
two-photon entangled states, but fails to predict entanglement when it is
associated with the entangled symmetric state. This explicitly identifies the
source of the discrepancy and explains why the system can be entangled without
spin-squeezing. We illustrate these findings in three examples of the
interaction of the system with thermal, classical squeezed vacuum and quantum
squeezed vacuum fields.Comment: 7 pages, 1 figur
Spin-spin interaction and spin-squeezing in an optical lattice
We show that by displacing two optical lattices with respect to each other,
we may produce interactions similar to the ones describing ferro-magnetism in
condensed matter physics. We also show that particularly simple choices of the
interaction lead to spin-squeezing, which may be used to improve the
sensitivity of atomic clocks. Spin-squeezing is generated even with partially,
and randomly, filled lattices, and our proposal may be implemented with current
technology.Comment: 4 pages, including 4 figure
Positive P simulations of spin squeezing in a two-component Bose condensate
The collisional interaction in a Bose condensate represents a non-linearity
which in analogy with non-linear optics gives rise to unique quantum features.
In this paper we apply a Monte Carlo method based on the positive P
pseudo-probability distribution from quantum optics to analyze the efficiency
of spin squeezing by collisions in a two-component condensate. The squeezing
can be controlled by choosing appropiate collision parameters or by
manipulating the motional states of the two components.Comment: 5 pages, 2 figures. Submitted to Phys. Rev.
Coupling of effective one-dimensional two-level atoms to squeezed light
A cavity QED system is analyzed which duplicates the dynamics of a two-level
atom in free space interacting exclusively with broadband squeezed light. We
consider atoms in a three or four-level Lambda-configuration coupled to a
high-finesse optical cavity which is driven by a squeezed light field. Raman
transitions are induced between a pair of stable atomic ground states via the
squeezed cavity mode and coherent driving fields. An analysis of the reduced
master equation for the atomic ground states shows that a three-level atomic
system has insufficient parameter flexibility to act as an effective two-level
atom interacting exclusively with a squeezed reservoir. However, the inclusion
of a fourth atomic level, coupled dispersively to one of the two ground states
by an auxiliary laser field, introduces an extra degree of freedom and enables
the desired interaction to be realised. As a means of detecting the reduced
quadrature decay rate of the effective two-level system, we examine the
transmission spectrum of a weak coherent probe field incident upon the cavity
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