412 research outputs found
1D Bose Gases in an Optical Lattice
We report on the study of the momentum distribution of a one-dimensional Bose
gas in an optical lattice. From the momentum distribution we extract the
condensed fraction of the gas and thereby measure the depletion of the
condensate and compare it with a theorical estimate. We have measured the
coherence length of the gas for systems with average occupation and
per lattice site.Comment: 4 pages, 3 figure
Measuring the temporal coherence of an atom laser beam
We report on the measurement of the temporal coherence of an atom laser beam
extracted from a Rb Bose-Einstein condensate. Reflecting the beam from a
potential barrier creates a standing matter wave structure. From the contrast
of this interference pattern, observed by magnetic resonance imaging, we have
deduced an energy width of the atom laser beam which is Fourier limited by the
duration of output coupling. This gives an upper limit for temporal phase
fluctuations in the Bose-Einstein condensate.Comment: 4 pages, 3 figure
Hybrid apparatus for Bose-Einstein condensation and cavity quantum electrodynamics: Single atom detection in quantum degenerate gases
We present and characterize an experimental system in which we achieve the
integration of an ultrahigh finesse optical cavity with a Bose-Einstein
condensate (BEC). The conceptually novel design of the apparatus for the
production of BECs features nested vacuum chambers and an in-vacuo magnetic
transport configuration. It grants large scale spatial access to the BEC for
samples and probes via a modular and exchangeable "science platform". We are
able to produce \87Rb condensates of five million atoms and to output couple
continuous atom lasers. The cavity is mounted on the science platform on top of
a vibration isolation system. The optical cavity works in the strong coupling
regime of cavity quantum electrodynamics and serves as a quantum optical
detector for single atoms. This system enables us to study atom optics on a
single particle level and to further develop the field of quantum atom optics.
We describe the technological modules and the operation of the combined BEC
cavity apparatus. Its performance is characterized by single atom detection
measurements for thermal and quantum degenerate atomic beams. The atom laser
provides a fast and controllable supply of atoms coupling with the cavity mode
and allows for an efficient study of atom field interactions in the strong
coupling regime. Moreover, the high detection efficiency for quantum degenerate
atoms distinguishes the cavity as a sensitive and weakly invasive probe for
cold atomic clouds
1D Bose gases in an optical lattice
We report on the study of the momentum distribution of a one-dimensional Bose gas in an optical lattice. From the momentum distribution we extract the condensed fraction of the gas and thereby measure the depletion of the condensate and compare it with a theoretical estimate. We have measured the coherence length of the gas for systems with average occupation n̄>1 and n̄<1 per lattice sit
Fringe spacing and phase of interfering matter waves
We experimentally investigate the outcoupling of atoms from Bose-Einstein
condensates using two radio-frequency (rf) fields in the presence of gravity.
We show that the fringe separation in the resulting interference pattern
derives entirely from the energy difference between the two rf fields and not
the gravitational potential difference. We subsequently demonstrate how the
phase and polarisation of the rf radiation directly control the phase of the
matter wave interference and provide a semi-classical interpretation of the
results.Comment: 4 pages, 3 figure
Optics with an Atom Laser Beam
We report on the atom optical manipulation of an atom laser beam. Reflection,
focusing and its storage in a resonator are demonstrated. Precise and versatile
mechanical control over an atom laser beam propagating in an inhomogeneous
magnetic field is achieved by optically inducing spin-flips between atomic
ground states with different magnetic moment. The magnetic force acting on the
atoms can thereby be effectively switched on and off. The surface of the atom
optical element is determined by the resonance condition for the spin-flip in
the inhomogeneous magnetic field. A mirror reflectivity of more than 98% is
measured
Dynamical coupling between a Bose-Einstein condensate andacavity optical lattice
A Bose-Einstein condensate is dispersively coupled to a single mode of an ultra-high finesse optical cavity. The system is governed by strong interactions between the atomic motion and the light field even at the level of single quanta. While coherently pumping the cavity mode the condensate is subject to the cavity optical lattice potential whose depth depends nonlinearly on the atomic density distribution. We observe optical bistability already below the single photon level and strong back-action dynamics which tunes the coupled system periodically out of resonanc
An Atom Laser with a cw Output Coupler
We demonstrate a continuous output coupler for magnetically trapped atoms.
Over a period of up to 100 ms a collimated and monoenergetic beam of atoms is
continuously extracted from a Bose- Einstein condensate. The intensity and
kinetic energy of the output beam of this atom laser are controlled by a weak
rf-field that induces spin flips between trapped and untrapped states.
Furthermore, the output coupler is used to perform a spectroscopic measurement
of the condensate, which reveals the spatial distribution of the magnetically
trapped condensate and allows manipulation of the condensate on a micrometer
scale.Comment: 4 pages, 4 figure
Exploring phase coherence in a 2D lattice of Bose-Einstein condensates
Bose-Einstein condensates of rubidium atoms are stored in a two-dimensional
periodic dipole force potential, formed by a pair of standing wave laser
fields. The resulting potential consists of a lattice of tightly confining
tubes, each filled with a 1D quantum gas. Tunnel-coupling between neighboring
tubes is controlled by the intensity of the laser fields. By observing the
interference pattern of atoms released from more than 3000 individual lattice
tubes the phase coherence of the coupled quantum gases is studied. The lifetime
of the condensate in the lattice and the dependence of the interference pattern
on the lattice configuration are investigated.Comment: 4 pages, 6 figure
Quantitative Determination of Temperature in the Approach to Magnetic Order of Ultracold Fermions in an Optical Lattice
We perform a quantitative simulation of the repulsive Fermi-Hubbard model using an ultracold gas trapped in an optical lattice. The entropy of the system is determined by comparing accurate measurements of the equilibrium double occupancy with theoretical calculations over a wide range of parameters. We demonstrate the applicability of both high-temperature series and dynamical mean-field theory to obtain quantitative agreement with the experimental data. The reliability of the entropy determination is confirmed by a comprehensive analysis of all systematic errors. In the center of the Mott insulating cloud we obtain an entropy per atom as low as 0.77k(B) which is about twice as large as the entropy at the Neel transition. The corresponding temperature depends on the atom number and for small fillings reaches values on the order of the tunneling energy
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