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Working on Bose Einstein Condensation

I did my phD studies in Alain Aspect's atom optic group.

I worked on Bose-Einstein condensation (BEC) and it's application to quantum-intereferomotric sensing of inertial fields.

  1. In spring 2004 Rob Nyman and I have started building a new experiment (nicknamed "KRub") to produce a new BEC source for the study of degenerate atomic gases in atom-interferometry. In falls 2005 we were joined by Jean-François Clément and in june 2006 by Jean-Philippe Brantut.

    The experiment is now leading a life of its own, as I defended my phD in January 2008.

    • We often took pictures of the work in progress in the lab, and you see them on KRubLog, the unofficial blog of the experiment.

    KRubLog: pictures of the "KRub" experiment.

  2. In September 2006 I started the "little-ICE" project, a spin-off of our main experiment to perform atom-interferometric measurements in ballistic flights: 20 seconds of micro-gravity in a free-falling plane.

    In particular, we demonstrated the first atom interferometer to perform in microgravity.

Atom-interferometry

An interferometric device compares the phase-shift undergone by test particles in two different paths (that can by spatially separated, or only separated by internal parameters). It can thus read to a high precision the potential felt by the test particles.

Photon-interferometry is a well established technique for high precision measurements. State of the art gravimeters are made of a falling test mass whose acceleration is read by photon interferometry. Sagnac-effect gyrometers drive inertial-navigation centers of almost all planes.

Atom-interferometry promises orders of magnitude more sensitivity than photon-interferometry but is still in its infancy.

Coherent atom-interferometry in micro-gravity

Long term goals of our research project (see also our group's webpage ):

The use of ultracold atomic gases as a source for matter-wave interferometry allows high signal-to-noise ratio due to high densities and narrow momentum-spectra. To avoid inhomogeneities of external potential, propagation between beam splitters in an atom interferometer is usually achieved via free-fall. The sensitivity of an interferometric measurement is limited in current high-precision experiments by the propagation time of the atoms, itself limited by the free expansion of the atomic cloud in the vacuum chamber. The use of a Bose-condensed cloud dramaticaly reduces the ballistic expansion and allows for long propagation times.

To access experimentally such long fall times we are building a transportable atom-interferometry apparatus that can be used on an aeroplane, in ballistic flights, to perform measurements in micro-gravity. A mixture of quantum degenerate gases, bosonic 87Rb and fermionic 40K, will be used in a Raman-pulse interferometer for accelerometry.

Interactions in high density samples such as Bose-condensed gases give rise to systematic shifts in interferometric measurements. Fermionic degenerate gases have a broad momentum distribution but negligible collisions. We plan to study the importance of interaction shifts in our 87 Rb bosonic sample using a Fermi gas of 40K.

This experiment is part of the French collaboration for doing atom-interferometry in micro-gravity: ICE.

Publication list

Papers

[1] R. A. Nyman, G. Varoquaux, B. Villier, D. Sacchet, F. Moron, Y. Le Coq, A. Aspect, and P. Bouyer, Tapered-amplified AR-coated laser diodes for Potassium and Rubidium atomic-physics experiments , Review of Scientific Instruments 77, 033105 (2006)

[2] R. A. Nyman, G. Varoquaux, F. Lienhart, D. Chambon, S. Boussen, J.-F. Clément, T. Muller, G. Santarelli, F. Pereira Dos Santos, A. Clairon, A. Bresson, A. L., Philippe Bouyer, I.C.E.: a Transportable Atomic Inertial Sensor for Test in Microgravity , Journal of Applied physics B, 84 673-681 (2006)

[3] G. Varoquaux, N. Zahzam, W. Chaibi, J.-F. Clément, O. Carraz, J.-P. Brantut, R. A. Nyman, F. Pereira Dos Santos, L. Mondin, M. Rouzé, Y. Bidel, A. Bresson, A. Landragin, P. Bouyer, I.C.E.: An Ultra-Cold Atom Source for Long-Baseline Interferometric Inertial Sensors in Reduced Gravity , Proceedings of the "Rencontres de Moriond, Gravitational Waves and Experimental Gravity", March 2007

[4] E. Varoquaux and G. Varoquaux, The Sagnac effect in superfluids. Uspekhi Fizicheskikh Nauk 2, 217 (Feb. 2008).

[5] G. Varoquaux, Agile computer control of a complex experiment. Computing in Science and Engineering 10(2), 55 (2008).

[6] P. Bouyer, G. Varoquaux, R. A. Nyman, J.-P. Brantut, G. Stern, T. Bourdel, B. Battelier, A. Landragin, O. Chaibi, F. Pereira Dos Santos, A. Bresson, N. Zahzam, Y. Bidel, O. Carras, M. Rouzé, and L. Mondin Testing the universality of free fall in a freely-falling two-species atom interferometer: the I.C.E project, Proceedings of the International Conference on Space Optics, Toulouse, France, October 2008.

[7] J.P. Brantut, J.F. Clement, M.R. de Saint Vincent, G. Varoquaux, R.A. Nyman, A. Aspect, T. Bourdel, P. Bouyer, Light-shift tomography in an optical-dipole trap for neutral atoms, Physical Review A., 78, (3), pp. 31401, (2008).

[8] G. Stern , B. Battelier, R. Geiger, G. Varoquaux, A. Villing, F. Moron, O. Carraz, N. Zahzam, Y. Bidel, W. Chaibi, F. Pereira Dos Santos, A. Bresson, A. Landragin, and P. Bouyer Light-pulse atom interferometry in microgravity, European Physical Journal D, 53, 353-357, (2009).

[9] G. Varoquaux, R.A. Nyman, R. Geiger, P. Cheinet, A. Landragin and P. Bouyer, How to estimate the differential acceleration in a two-species atom interferometer to test the equivalence principle, New Journal of Physics, 11 113010, (2009).

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