56 research outputs found
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Broadband boundary effects on Brownian motion
Brownian motion of particles in confined fluids is important for many applications, yet the effects of the boundary over a wide range of time scales are still not well understood. We report high-bandwidth, comprehensive measurements of Brownian motion of an optically trapped micrometer-sized silica sphere in water near an approximately flat wall. At short distances we observe anisotropic Brownian motion with respect to the wall. We find that surface confinement not only occurs in the long time scale diffusive regime but also in the short time scale ballistic regime, and the velocity autocorrelation function of the Brownian particle decays faster than that of a particle in bulk fluid. Furthermore, at low frequencies the thermal force loses its color due to the reflected flow from the no-slip boundary. The power spectrum of the thermal force on the particle near a no-slip boundary becomes flat at low frequencies. This detailed understanding of boundary effects on Brownian motion opens a door to developing a 3D microscope using particles as remote sensors.Sid W. Richardson FoundationR. A. Welch Foundation F-1258Physic
Magneto-Optical Cooling of Atoms
We propose an alternative method to laser cooling. Our approach utilizes the
extreme brightness of a supersonic atomic beam, and the adiabatic atomic
coilgun to slow atoms in the beam or to bring them to rest. We show how
internal-state optical pumping and stimulated optical transitions, combined
with magnetic forces can be used to cool the translational motion of atoms.
This approach does not rely on momentum transfer from photons to atoms, as in
laser cooling. We predict that our method can surpass laser cooling in terms of
flux of ultra-cold atoms and phase-space density, with lower required laser
power and reduced complexity
Calculation of Atomic Number States: a Bethe Ansatz Approach
We analyze the conditions for producing atomic number states in a
one-dimensional optical box using the Bethe ansatz method. This approach
provides a general framework, enabling the study of number state production
over a wide range of realistic experimental parameters
A Quantum Tweezer for Atoms
We propose a quantum tweezer for extracting a desired number of neutral atoms
from a reservoir. A trapped Bose-Einstein condensate (BEC) is used as the
reservoir, taking advantage of its coherent nature, which can guarantee a
constant outcome. The tweezer is an attractive quantum dot, which may be
generated by red-detuned laser light. By moving with certain speeds, the dot
can extract a desired number of atoms from the BEC through Landau-Zener
tunneling. The feasibility of our quantum tweezer is demonstrated through
realistic and extensive model calculations.Comment: 4 pages, 6 figures Revised versio
Quantum Chaos of Bogoliubov Waves for a Bose-Einstein Condensate in Stadium Billiards
We investigate the possibility of quantum (or wave) chaos for the Bogoliubov
excitations of a Bose-Einstein condensate in billiards. Because of the mean
field interaction in the condensate, the Bogoliubov excitations are very
different from the single particle excitations in a non-interacting system.
Nevertheless, we predict that the statistical distribution of level spacings is
unchanged by mapping the non-Hermitian Bogoliubov operator to a real symmetric
matrix. We numerically test our prediction by using a phase shift method for
calculating the excitation energies.Comment: minor change, 4 pages, 4 figures, to appear in Phys. Rev. Let
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