We advertise an experimental postdoc position opening in North-Paris University, Laboratoire de Physique des Lasers, to work on our chromium quantum gas experiment, which aims at studying the growth of quantum correlations in a many-body system driven by dipole-dipole interactions.
Loading quantum gases in periodic potentials made of optical lattices has become a prominent way to investigate quantum many-body physics. Our project focuses on the magnetic properties of chromium quantum gases, which are quite original as high spin S=3 chromium atoms interact with each other through dipolar interactions. The long-range character of dipolar interactions ensures coupling of atoms loaded in different sites of the optical lattice . We have recently shown that our isolated many-body dipolar spin system system thus thermalizes under the effect of long-range interactions, consistent with a scenario of quantum thermalization .
The goal of our project is now to experimentally characterize the dynamical growth of entanglement in this scenario, by using new experimental tools that will be developed in close collaboration with theoretical studies. Our approach relies on the measurement of collective properties, such as those provided by monitoring the total populations of the 7 different Zeeman states by means of a Stern-Gerlach separation. The observation of the fluctuations of the collective spin can give information on the growth of quantum correlations.
In addition, we will implement bichromatic optical lattices, which will create an array of double potential wells. In this system, the collective spin of the atoms can be measured independently in the odd wells and in the even wells, because a controlled energy tilt can be applied between the two sub-lattice sites. Measuring the spin state of atoms in every other site constitutes a bi-partite measurement, which is known to offer efficient ways to characterize entanglement in a large pure system.
The post-doctoral researcher will first finalize setting up the double-well lattice architecture, together with one PhD student that he/she will contribute supervising. Then the candidate will be involved in setting up the differential measurement leading to the characterization of bi-partite spin fluctuations. Together with our theory collaborator Tommaso Roscilde, he/she will explore which measurements may best reveal entanglement. The candidate should have a strong background in AMO experimental physics, cold atom physics, and the use of cold atoms to investigate quantum many-body physics.
 A. de Paz et al, Phys. Rev. Lett. 111, 185305 (2013)
 S. Lepoutre et al., Nature Communications, 10, 1714 (2019)
The Magnetic Quantum Gases group at LPL combines two experimental projects studying magnetism on Chromium and Strontium, and a theory activity. Our group hosts three researchers from the Paris 13 University, two CNRS researchers, and one CNRS Engineer. At the moment, four PhD students are working on our projects.