Master 2 internship - related funded PhD position [filled]
Topic: Absorption imaging of a one-dimensional gas
In the cold atom domain, absorption imaging allows the measurement of the density distribution of diluted quantum gases. Atoms initially trapped in a magnetic potential are released and undergo a time of flight before being illuminated by a laser beam at resonance with an atomic transition. Finally, an optical objective allows the beam to be imaged on a CCD camera. Comparison of the intensity distribution of the laser beam in the presence of the atoms and that obtained in the absence of the atoms makes it possible to deduce the atomic density. The optical objective is based on the use of two converging lenses leading to a fixed magnification and a resolution limited by the wavelength of the laser. In principle, the addition of additional lenses reduces the size of the lens.
On our experimental device, ultracold sodium atoms are magnetically trapped on the surface of an atomchip. The magnetic potential being very anisotropic, the gas reaches the one-dimensional regime for temperatures on the order of hundred nanokelvin. Once released, the properties of the gas can be deduced using an absoption imaging system.
The purpose of the internship will be to design and implement such a system on the experimental device. It will start with a simulation of the properties of the optical objective using the Zeemax software and then build it using commercial lenses. The objective will then be experimentally characterized before being installed on the experimental setup. Finally, it will be tested directly on the one-dimensional cold gases produced at the surface of the atom chip.
Environment: The student will be supervised by Aurélien Perrin, within the BEC group, and will benefit from stimulating interactions with the larger Quantum gases group of about fifteen people, including three other ultra cold atom experiments and a theory group. Our group is a member of SIRTEQ, a world-leading joint Institute gathering all the groups in Paris area in the field Quantum technologies. The internship is expected to lead to a PhD position (secured funding), see related PhD offer.
Aurélien Perrin 01 49 40 32 03 or Hélène Perrin / email
Topic: Out-of-equilibrium dynamics of a superfluid
Quantum gases are one of the most fascinating quantum systems now available in the lab. Far beyond atomic physics, their applications include quantum metrology, superfluidity, quantum information and quantum simulation in the wider and developing frame of quantum technology.
In this context, the BEC group at Laser Physics Laboratory has developed a rubidium Bose-Einstein condensation experiment. This experimental setup produces a superfluid degenerate bosonic gas confined in a « bubble-like » potential obtained by a combination of magnetic and radiofrequency fields. Initially, the atoms occupy the bottom of this bubble, in a flat 2D geometry. We have developed tools to excite the system, either by means of magnetic/radio-frequency control, or with optical tools like an optical laser stirrer able to create a local perturbation of the quantum gas. These tools allow us to set the superfluid into rotation, and also modify dynamically the landscape seen by the atoms in order to put them out of equilibrium. In particular, we have prepared a fast rotating superfluid flow in the bubble: due to the centrifugal force, the gas climbs along the side of the bubble and takes a circular shape away from the bottom. In this way, we are able to bring the superfluid to very fast rotations rates, with supersonic speeds reaching Mach 18 i.e. 18 times the speed of sound in the gas . This superfluid flow persists for about one minute in the rotationally invariant bubble trap.
The subject of the internship is to probe the stability of this fast flow and to study the eventual decay mechanisms. To this aim, we will add a local obstacle produced with the laser stirrer and study the decay of rotation as a function of the laser parameters (position, intensity). The student will participate in the various steps of the experiment, from running the experiment to the data analysis.
Environment: This internship will give the appointed student the opportunity to enhance his/her experimental skills in optics and atomic physics. The student will be supervised by Laurent Longchambon within the BEC group, beneficing from stimulating interaction with the larger Quantum gases group of about fifteen people, including three other ultra cold atom experiments and a theory group.
Our group is a member of SIRTEQ, a world-leading joint institute gathering all the groups in Paris area in the field of quantum technology. The internship may lead to a PhD position (on the other setup).
Laurent Longchambon 01 49 40 36 71 or Hélène Perrin / email