6,528 research outputs found
Quantum-gas microscopes - A new tool for cold-atom quantum simulators
This "Perspectives" paper gives a brief overview of the recent developments
with quantum-gas microscopes and how they can be used to build the next
generation of cold-atom quantum simulators.Comment: "Perspectives" paper for Special Issue "Cold Atom Physics" of Natl.
Sci. Rev; published online April 19, 201
Single top quark measurements with CMS
Measurements of single top quark production are presented, performed using
CMS data collected in 2011 and 2012 at centre-of-mass energies of 7 and 8 TeV.
The cross sections for the electroweak production of single top quarks in the
t-channel and in association with W-bosons is measured and the results are used
to place constraints on the CKM matrix element |V_tb|.Comment: 5 pages, 6 figures, conference HCP201
Frequency-Dependent Selection at Rough Expanding Fronts
Microbial colonies are experimental model systems for studying the
colonization of new territory by biological species through range expansion. We
study a generalization of the two-species Eden model, which incorporates local
frequency-dependent selection, in order to analyze how social interactions
between two species influence surface roughness of growing microbial colonies.
The model includes several classical scenarios from game theory. We then
concentrate on an expanding public goods game, where either cooperators or
defectors take over the front depending on the system parameters. We analyze in
detail the critical behavior of the nonequilibrium phase transition between
global cooperation and defection and thereby identify a new universality class
of phase transitions dealing with absorbing states. At the transition, the
number of boundaries separating sectors decays with a novel power law in time
and their superdiffusive motion crosses over from Eden scaling to a nearly
ballistic regime. In parallel, the width of the front initially obeys Eden
roughening and, at later times, passes over to selective roughening.Comment: 11 pages, 10 figure
An objective lens for efficient fluorescence detection of single atoms
We present the design of a diffraction limited, long working distance
monochromatic objective lens for efficient light collection. Consisting of four
spherical lenses, it has a numerical aperture of 0.29, an effective focal
length of 36 mm and a working distance of 36.5 mm. This inexpensive system
allows us to detect 8*10^4 fluorescence photons per second from a single cesium
atom stored in a magneto-optical trap.Comment: 3 pages, 3 figures, revtex4, submitted to Review of Scientific
Instrument
A cavity-QED scheme for Heisenberg-limited interferometry
We propose a Ramsey interferometry experiment using an entangled state of N
atoms to reach the Heisenberg limit for the estimation of an atomic phase shift
if the atom number parity is perfectly determined. In a more realistic
situation, due to statistical fluctuations of the atom source and the finite
detection efficiency, the parity is unknown. We then achieve about half the
Heisenberg limit. The scheme involves an ensemble of circular Rydberg atoms
which dispersively interact successively with two initially empty microwave
cavities. The scheme does not require very high-Q cavities. An experimental
realization with about ten entangled Rydberg atoms is achievable with state of
art apparatuses.Comment: 13 pages, 7 figure
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