Using the unique detection properties offered by metastable helium atoms we have produced high resolution images of the transverse spatial profiles of an atom laser beam. We observe transverse fringes on the beam, resulting from quantum mechanical interference between atoms that start from rest at different transverse locations within the outcoupling surface and end up at a later time with different velocities at the same transverse position. Further, for high outcoupling rates we see the emergence of structure on the beam profile, which is not predicted by the usual Gross-Pitaevskii equation.Using the unique detection properties offered by metastable helium atoms we have produced high resolution images of the transverse spatial profiles of an atom laser beam. We observe transverse fringes on the beam, resulting from quantum mechanical interference between atoms that start from rest at different transverse locations within the outcoupling surface and end up at a later time with different velocities at the same transverse position. Further, for high outcoupling rates we see the emergence of structure on the beam profile, which is not predicted by the usual Gross-Pitaevskii equation.

Quantum-Atom Optics Downunder (QAO)Jan 1, 20070 citations

Transverse mode of an atom laser

Thomas Busch, Michael Köhl, Tilman Esslinger +1 more

The transverse mode of an atom laser beam that is outcoupled from a Bose--Einstein condensate is investigated and is found to be strongly determined by the mean-field interaction of the laser beam with the condensate. For repulsive interactions, the condensate acts as a diverging lens for the outcoupled atoms, and transverse interference fringes in the atomic beam are predicted due to the coherent addition of amplitudes for atoms emitted from different regions in the condensate. This effect can be used to investigate the transverse coherence of an atom laser beam.The transverse mode of an atom laser beam that is outcoupled from a Bose--Einstein condensate is investigated and is found to be strongly determined by the mean-field interaction of the laser beam with the condensate. For repulsive interactions, the condensate acts as a diverging lens for the outcoupled atoms, and transverse interference fringes in the atomic beam are predicted due to the coherent addition of amplitudes for atoms emitted from different regions in the condensate. This effect can be used to investigate the transverse coherence of an atom laser beam.

arXiv:cond-mat/0110555Physical Review AApr 5, 200229 citations

Atomic interference patterns in the transverse plane

M. Boustimi, Valerij Bočvarski, B. Viaris de Lesegno +4 more

A quadrupolar static magnetic field used as a phase object in a Stern-Gerlach atom interferometer produces phase shifts proportional to the distance to the zero-field line. As a consequence the transverse intensity profile of the atomic beam beyond the interferometer is modulated by an interference pattern which is a ``phase portrait'' of the field configuration. This pattern---a central bright spot surrounded by annular fringes---can be translated as a whole in any transverse direction by adding a homogeneous field to the quadrupolar field. These effects have been investigated experimentally with a beam of metastable hydrogen atoms ${\mathrm{H}}^{*}(2s),$ either by measuring the atom flux through a fixed slit or by scanning the beam profile through a movable hole. The results are in good agreement with the theoretical predictions.A quadrupolar static magnetic field used as a phase object in a Stern-Gerlach atom interferometer produces phase shifts proportional to the distance to the zero-field line. As a consequence the transverse intensity profile of the atomic beam beyond the interferometer is modulated by an interference pattern which is a ``phase portrait'' of the field configuration. This pattern---a central bright spot surrounded by annular fringes---can be translated as a whole in any transverse direction by adding a homogeneous field to the quadrupolar field. These effects have been investigated experimentally with a beam of metastable hydrogen atoms ${\mathrm{H}}^{*}(2s),$ either by measuring the atom flux through a fixed slit or by scanning the beam profile through a movable hole. The results are in good agreement with the theoretical predictions.

Physical Review AFeb 10, 200013 citations

Results of {open_quotes}Heisenberg Microscope{close_quotes} decoherence atom interferometry experiments

John F. Clauser, S. Li, Matthias Reinsch

We present results of atom interferometry experiments in which spatial matter - wave interference is revealed by its selective destruction. A thermal potassium beam is transmitted through a velocity selective atom interferometer and detected. The interferometer is a sequence of three diffraction gratings. Interference fringes forming a Moire pattern with the third grating determine the transmission. The thermal beam produces a velocity average over different fringe Fourier components, each resonant in the interferometer at a different atomic velocity. AC modulated laser light passes through the interferometer, near the middle grating. Since imaging of the fluorescent light could be used to determine which slit an atom passes, the contribution to the fringe pattern by atoms at the laser`s Doppler shifted wavelength is removed. That component is thus AC modulated and detected. This {open_quotes}atom interference filter{close_quotes} resolves the K{sup 39} HFS.We present results of atom interferometry experiments in which spatial matter - wave interference is revealed by its selective destruction. A thermal potassium beam is transmitted through a velocity selective atom interferometer and detected. The interferometer is a sequence of three diffraction gratings. Interference fringes forming a Moire pattern with the third grating determine the transmission. The thermal beam produces a velocity average over different fringe Fourier components, each resonant in the interferometer at a different atomic velocity. AC modulated laser light passes through the interferometer, near the middle grating. Since imaging of the fluorescent light could be used to determine which slit an atom passes, the contribution to the fringe pattern by atoms at the laser`s Doppler shifted wavelength is removed. That component is thus AC modulated and detected. This {open_quotes}atom interference filter{close_quotes} resolves the K{sup 39} HFS.

Bulletin of the American Physical SocietyMay 1, 19930 citations

Approach to coherent interference fringes in helium-surface scattering

Matthew C. Schram, Eric J. Heller

The conventional notion of elastic, coherent atom-surface scattering originates from the scattering particles acting as a quantum-mechanical matter wave, which coherently interfere to produce distinct Bragg peaks which persist at finite temperature. If we introduce inelastic scattering to this scenario, the result is that the surface particles become displaced by the scattering atoms, resulting in emission or absorption of phonons that shift the final energy and momentum of the scatterer. As the lowest-lying phonons are gapless excitations, the ability to measure these phonons is very difficult and this difficulty is exacerbated by the roughly 1-eV resolution found in high-energy helium scattering experiments. Even though the surface has in effect measured the presence of the scatterer which decoheres the particle, we retain the diffraction spots which are referred to as coherent scattering. How do we reconcile these disparate viewpoints? We propose an experiment to more precisely examine the question of coherence in atom-surface scattering. We begin with an initially coherent superposition of helium particles with equal probabilities of interacting with the surface or not interacting with the surface. The beams are directed so that after the scattering event, the atoms are recombined so that we can observe the resulting interference pattern. The degree to which phonons are excited in the lattice by the scattering process dictates the fringe contrast of the interference pattern of the resulting beams. We use semiclassical techniques to simulate and test the viability of this experiment and show that for a wide range of conditions, despite the massive change in the momentum perpendicular to the surface, we can still expect to have coherent (in the superposition sense) scattering.The conventional notion of elastic, coherent atom-surface scattering originates from the scattering particles acting as a quantum-mechanical matter wave, which coherently interfere to produce distinct Bragg peaks which persist at finite temperature. If we introduce inelastic scattering to this scenario, the result is that the surface particles become displaced by the scattering atoms, resulting in emission or absorption of phonons that shift the final energy and momentum of the scatterer. As the lowest-lying phonons are gapless excitations, the ability to measure these phonons is very difficult and this difficulty is exacerbated by the roughly 1-eV resolution found in high-energy helium scattering experiments. Even though the surface has in effect measured the presence of the scatterer which decoheres the particle, we retain the diffraction spots which are referred to as coherent scattering. How do we reconcile these disparate viewpoints? We propose an experiment to more precisely examine the question of coherence in atom-surface scattering. We begin with an initially coherent superposition of helium particles with equal probabilities of interacting with the surface or not interacting with the surface. The beams are directed so that after the scattering event, the atoms are recombined so that we can observe the resulting interference pattern. The degree to which phonons are excited in the lattice by the scattering process dictates the fringe contrast of the interference pattern of the resulting beams. We use semiclassical techniques to simulate and test the viability of this experiment and show that for a wide range of conditions, despite the massive change in the momentum perpendicular to the surface, we can still expect to have coherent (in the superposition sense) scattering.

Physical Review AAug 28, 201811 citations

Three-beam atom interferometer

H. Hinderthür, Andreas Pautz, V. Rieger +4 more

We present an atom interferometer based on the interference of three partial matter waves in three different internal and external states. Coherent laser excitation acts as a beamsplitter to create a superposition state of the ground state and two Zeeman sublevels of the metastable state of magnesium atoms. The interference pattern of the output ports shows high contrast and the characteristics of three-beam interferences as known from optical interferometry. In comparison to two-beam interferometry a reduction of the fringe width of (32\ifmmode\pm\else\textpm\fi{}8)% is observed. This offers various possibilities for improved measurements of quantum-mechanical phases due to the internal atomic-state sensitive coupling of external potentials. This is demonstrated for the interaction of magnesium atoms with an external magnetic field.We present an atom interferometer based on the interference of three partial matter waves in three different internal and external states. Coherent laser excitation acts as a beamsplitter to create a superposition state of the ground state and two Zeeman sublevels of the metastable state of magnesium atoms. The interference pattern of the output ports shows high contrast and the characteristics of three-beam interferences as known from optical interferometry. In comparison to two-beam interferometry a reduction of the fringe width of (32\ifmmode\pm\else\textpm\fi{}8)% is observed. This offers various possibilities for improved measurements of quantum-mechanical phases due to the internal atomic-state sensitive coupling of external potentials. This is demonstrated for the interaction of magnesium atoms with an external magnetic field.

Physical Review ASep 1, 199722 citations

{\mathrm{H}}^{*}(2s),

either by measuring the atom flux through a fixed slit or by scanning the beam profile through a movable hole. The results are in good agreement with the theoretical predictions.