1,102 research outputs found
Comment on the paper: Quantum backaction of optical observations on Bose-Einstein condensates by U. Leonhardt, T. Kiss, and P. Piwnicki, Eur. Phys. J. D7, 413 (1999)
A recent paper, Quantum backaction of optical observations on Bose-Einstein
condensates by U. Leonhardt, T. Kiss, and P. Piwnicki, Eur. Phys. J. D7, 413
(1999), emphasized that the limit of dispersive imaging of Bose-Einstein
condensates with off-resonant light is not residual absorption, but a different
form of quantum backaction of the probe light. This note points out that these
conclusions are incorrect, and that Rayleigh scattering is the dominant quantum
backaction of dispersive imaging.Comment: 1 page (Comment on paper
An Optically Plugged Quadrupole Trap for Bose-Einstein Condensates
We created sodium Bose-Einstein condensates in an optically plugged
quadrupole magnetic trap (OPT). A focused, 532nm laser beam repelled atoms from
the coil center where Majorana loss is significant. We produced condensates of
up to atoms, a factor of 60 improvement over previous work [1],
a number comparable to the best all-magnetic traps, and transferred up to atoms into a purely optical trap. Due to the tight axial
confinement and azimuthal symmetry of the quadrupole coils, the OPT shows
promise for creating Bose-Einstein condensates in a ring geometry
Synthetic magnetic fluxes on the honeycomb lattice
We devise experimental schemes able to mimic uniform and staggered magnetic
fluxes acting on ultracold two-electron atoms, such as ytterbium atoms,
propagating in a honeycomb lattice. The atoms are first trapped into two
independent state-selective triangular lattices and are further exposed to a
suitable configuration of resonant Raman laser beams. These beams induce hops
between the two triangular lattices and make atoms move in a honeycomb lattice.
Atoms traveling around each unit cell of this honeycomb lattice pick up a
nonzero phase. In the uniform case, the artificial magnetic flux sustained by
each cell can reach about two flux quanta, thereby realizing a cold atom
analogue of the Harper model with its notorious Hofstadter's butterfly
structure. Different condensed-matter phenomena such as the relativistic
integer and fractional quantum Hall effects, as observed in graphene samples,
could be targeted with this scheme.Comment: 12 pages, 14 figure
A Distributed GUI-based Computer Control System for Atomic Physics Experiments
Atomic physics experiments often require a complex sequence of precisely
timed computer controlled events. A distributed GUI-based control system
designed with such experiments in mind, The Cicero Word Generator, is
described. The system makes use of a client-server separation between a user
interface for sequence design and a set of output hardware servers. Output
hardware servers are designed to use standard National Instruments output
cards, but the client-server nature allows this to be extended to other output
hardware. Output sequences running on multiple servers and output cards can be
synchronized using a shared clock. By using an FPGA-generated variable
frequency clock, redundant buffers can be dramatically shortened, and a time
resolution of 100ns achieved over effectively arbitrary sequence lengths
A simple model for interactions and corrections to the Gross-Pitaevskii Equation
One of the assumptions leading to the Gross-Pitaevskii Equation (GPE) is that
the interaction between atom pairs can be written effectively as a \delta
-function so that the interaction range of the particles is assumed to vanish.
A simple model that takes into account the extension of the inter-particle
potential is introduced. The correction to the GPE predictions for the energy
of a condensate confined by a harmonic trap in the Thomas-Fermi (TF) regime is
estimated. Although it is found to be small, we believe that in some situations
it can be measured using its dependance on the frequency of the confining trap.
Due to the simplicity of the model, it may have a wide range of applications.Comment: 22 pages, 2 figure
Enhanced Pauli blocking of light scattering in a trapped Fermi gas
Pauli blocking of spontaneous emission by a single excited-state atom has
been predicted to be dramatic at low temperature when the Fermi energy
exceeds the recoil energy . The photon scattering
rate of a ground-state Fermi gas can also be suppressed by occupation of the
final states accessible to a recoiling atom, however suppression is diminished
by scattering events near the Fermi edge. We analyze two new approaches to
improve the visibility of Pauli blocking in a trapped Fermi gas. Focusing the
incident light to excite preferentially the high-density region of the cloud
can increase the blocking signature by 14%, and is most effective at
intermediate temperature. Spontaneous Raman scattering between imbalanced
internal states can be strongly suppressed at low temperature, and is
completely blocked for a final-state in the
high imbalance limit.Comment: 12 pages, 8 figures. v4: to appear in Journal of Physics B: Atomic,
Molecular, and Optical Physic
Collective enhancement and suppression in Bose-Einstein condensates
The coherent and collective nature of Bose-Einstein condensate can enhance or
suppress physical processes. Bosonic stimulation enhances scattering in already
occupied states which leads to atom amplification, and the suppression of
dissipation leads to superfluidity. In this paper, we review several
experiments where suppression and enhancement have been observed and discuss
the common roots of and differences between these phenomena.Comment: ICAP proceedings; 12 figure
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