220 research outputs found
Long-Range Plasmon Assisted Energy Transfer Between Fluorescent Emitters
We demonstrate plasmon assisted energy transfer between fluorophores located
at distances up to m on the top of a thin silver film. Thanks to the
strong confinement and large propagation length of surface plasmon polaritons,
the range of the energy transfer is almost two orders of magnitude larger than
the values reported in the literature so far. The parameters driving the energy
transfer range are thoroughly characterized and are in very good agreement with
theoretically expected values.Comment: 5 pages, 4 figures, accepted for publication in Physical Review
Letter
Hanbury Brown and Twiss correlations in atoms scattered from colliding condensates
Low energy elastic scattering between clouds of Bose condensed atoms leads to
the well known s-wave halo with atoms emerging in all directions from the
collision zone. In this paper we discuss the emergence of Hanbury Brown and
Twiss coincidences between atoms scattered in nearly parallel directions. We
develop a simple model that explains the observations in terms of an
interference involving two pairs of atoms each associated with the elementary s
wave scattering process.Comment: Minor corrections. reference update
Fluctuations of the local density of states probe localized surface plasmons on disordered metal films
We measure the statistical distribution of the local density of optical
states (LDOS) on disordered semi-continuous metal films. We show that LDOS
fluctuations exhibit a maximum in a regime where fractal clusters dominate the
film surface. These large fluctuations are a signature of surface-plasmon
localization on the nanometer scale
Observation of atom pairs in spontaneous four wave mixing of two colliding Bose-Einstein Condensates
We study atom scattering from two colliding Bose-Einstein condensates using a
position sensitive, time resolved, single atom detector. In analogy to quantum
optics, the process can also be thought of as spontaneous, degenerate four wave
mixing of de Broglie waves. We find a clear correlation between atoms with
opposite momenta, demonstrating pair production in the scattering process. We
also observe a Hanbury Brown and Twiss correlation for collinear momenta, which
permits an independent measurement of the size of the pair production source
and thus the size of the spatial mode. The back to back pairs occupy very
nearly two oppositely directed spatial modes, a promising feature for future
quantum optics experiments.Comment: A few typos have been correcte
Anisotropy in s-wave Bose-Einstein condensate collisions and its relationship to superradiance
We report the experimental realization of a single-species atomic four-wave
mixing process with BEC collisions for which the angular distribution of
scattered atom pairs is not isotropic, despite the collisions being in the
-wave regime. Theoretical analysis indicates that this anomalous behavior
can be explained by the anisotropic nature of the gain in the medium. There are
two competing anisotropic processes: classical trajectory deflections due to
the mean-field potential, and Bose enhanced scattering which bears similarity
to super-radiance. We analyse the relative importance of these processes in the
dynamical buildup of the anisotropic density distribution of scattered atoms,
and compare to optically pumped super-radiance.Comment: 13 pages, 10 figures, added a fuller discussion of timescales,
otherwise some minor changes in the text and the formatting of Figures 5-
Sub-Poissonian number differences in four-wave mixing of matter waves
We demonstrate sub-Poissonian number differences in four-wave mixing of
Bose-Einstein condensates of metastable helium. The collision between two
Bose-Einstein condensates produces a scattering halo populated by pairs of
atoms of opposing velocities, which we divide into several symmetric zones. We
show that the atom number difference for opposing zones has sub-Poissonian
noise fluctuations whereas that of nonopposing zones is well described by shot
noise. The atom pairs produced in a dual number state are well adapted to sub
shot-noise interferometry and studies of Einstein-Podolsky-Rosen-type
nonlocality tests.Comment: 4 pages, 3 figure
Producing and Detecting Correlated atoms
We discuss experiments to produce and detect atom correlations in a
degenerate or nearly degenerate gas of neutral atoms. First we treat the atomic
analog of the celebrated Hanbury Brown Twiss experiment, in which atom
correlations result simply from interference effects without any atom
interactions.We have performed this experiment for both bosons and fermions.
Next we show how atom interactions produce correlated atoms using the atomic
analog of spontaneous four-wavemixing. Finally, we briefly mention experiments
on a one dimensional gas on an atom chip in which correlation effects due to
both interference and interactions have been observed.Comment: to appear in conference proceedings "Atomic Physics 20
Correlated blinking of fluorescent emitters mediated by single plasmons
We observe time-correlated emission between a single CdSe/CdS/ZnS quantum dot exhibiting single-photon statistics and a fluorescent nanobead located micrometers apart. This is accomplished by coupling both emitters to a silver nanowire. Single plasmons are created on the latter from the quantum dot, and transfer energy to excite in turn the fluorescent nanobead. We demonstrate that the molecules inside the bead show the same blinking behavior as the quantum dot
Camparison of the Hanbury Brown-Twiss effect for bosons and fermions
Fifty years ago, Hanbury Brown and Twiss (HBT) discovered photon bunching in
light emitted by a chaotic source, highlighting the importance of two-photon
correlations and stimulating the development of modern quantum optics . The
quantum interpretation of bunching relies upon the constructive interference
between amplitudes involving two indistinguishable photons, and its additive
character is intimately linked to the Bose nature of photons. Advances in atom
cooling and detection have led to the observation and full characterisation of
the atomic analogue of the HBT effect with bosonic atoms. By contrast, fermions
should reveal an antibunching effect, i.e., a tendency to avoid each other.
Antibunching of fermions is associated with destructive two-particle
interference and is related to the Pauli principle forbidding more than one
identical fermion to occupy the same quantum state. Here we report an
experimental comparison of the fermion and the boson HBT effects realised in
the same apparatus with two different isotopes of helium, 3He (a fermion) and
4He (a boson). Ordinary attractive or repulsive interactions between atoms are
negligible, and the contrasting bunching and antibunching behaviours can be
fully attributed to the different quantum statistics. Our result shows how
atom-atom correlation measurements can be used not only for revealing details
in the spatial density, or momentum correlations in an atomic ensemble, but
also to directly observe phase effects linked to the quantum statistics in a
many body system. It may thus find applications to study more exotic situations
>.Comment: Nature 445, 402 (2007). V2 includes the supplementary informatio
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