varoquaux@normalesupWorking on Bose Einstein Condensation
I am currently a phD student in Alain Aspect's atom optic group.
I work on Bose-Einstein condensation. In spring 2004 Rob Nyman and I have started building a new experiment (nicknamed "KRub") that aim tho achieve BEC with Rubidium 87, and Fermi degeneracy with Potassium 40 to study the use of degenerate atomic gases for atom-interferometry. In falls 2005 we have been joined by Jean-François Clément and in june 2006 by Jean-Philippe Brantut.
- We often take 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.
- Since September 2006 I am in charge of the "little-ICE" project, a spin-off of our experiment that aims to go in a plane to demonstrate that our technology can work in ballistic flights.
little-ICElog: pictures of the little-ICE project.
- my CV: my Curriculum Vitae, with my publication list.
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
The long term goals of our experiment (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] Robert A. Nyman, Gaël Varoquaux, Fabien Lienhart, Damien Chambon, Salah Boussen, Jean-François Clément, T. Muller, Giorgio Santarelli, Frank Pereira Dos Santos, André Clairon, Alexandre Bresson, Arnaud Landragin, Philippe Bouyer, I.C.E.: a Transportable Atomic Inertial Sensor for Test in Microgravity , Journal of Applied physics B, 84 673-681 (2006)
[3] Authors: Gaël Varoquaux, Nassim Zahzam, Walid Chaibi, Jean-François Clément, Olivier Carraz, Jean-Philippe Brantut, Robert A. Nyman, Franck Pereira Dos Santos, Linda Mondin, Michel Rouzé, Yannick Bidel, Alexandre Bresson, Arnaud Landragin, Philippe 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).
Invited Talks
- Building a double-species slow atomic source, EGC workshop, June 26-30, 2005, Gif sur Yvette, France.
- A source for coherent atom-interferometry in micro-gravity, EGC workshop July 11-14, 2006, Stirling, UK.
- Little-I.C.E.: towards atom interferometry in free-fall, June 7 2006, Seminar at SYRTE, observatoire de Paris, Paris, France.
- TraitsUI pour développer des applications graphiques, Journées Python Francophones, June 2-3 2007, Cité des Sciences, Paris, France.
- mlab: a pylab-like interface to Mayavi2, SciPy'07, 16-17 August 2007, CalTech, Pasadena, CA, USA.
- Atomic sources for long-interrogation-time interferometric inertial sensors, 18 February 2008, Laser Center Vrije Universiteit Amsterdam, Netherlands.
- Mayavi and Python in science, Open Knowledge conference, 15 March 2008, London School of Economics, London, UK.
Posters
- A boson-fermion atom interferometer for inertial sensing YAO, February 14-18 2006, École Polytechnique, Palaiseau, France (this poster won the IOP prize for young atom opticians )
- ICE: towards long-baseline atom interferometry ICOLS, June 24-29, 2007, Tellurride, CO, USA.
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