The AUFRONS (Ultra cold atoms in nanostructured optical potential) project aims at building near field optics / Ultra cold atoms hybrid systems to achieve stronger interaction between solid state and cold atoms physics. One of our goals is to manipulate cold fermionic species at the vicinity of a surface.The laser used to cool the ferminic species are developped in partnership with the iXlim to create a fully fibered laser system using telecom technologies. The goal is to meet AMO standard using a compact, robust fully fibered scheme
The AUFRONS (Ultra cold atoms in nanostructured optical potential) project aims at building near field optics / Ultra cold atoms hybrid systems to achieve stronger interaction between solid state and cold atoms physics. One of our goals is to manipulate cold fermionic species at the vicinity of a surface.The laser used to cool the ferminic species are developped in partnership with the iXlim to create a fully fibered laser system using telecom technologies. The goal is to meet AMO standard using a compact, robust fully fibered scheme
This project is concerned with ultra-sensitive characterization of the interaction of microwave and optical transitions in atomic clouds and solid materials. Microwave Electron Spin Resonance spectroscopy is performed on low loss ferromagnetics and paramagnetic, rare-earth impurity ions in crystal lattices, searching for systems capable of strong coupling. In the optical regime, laser-cooled and trapped neutral Ytterbium atoms are spectroscopically studied with an aim to develop an optical lattice clock for the international Atomic Clock Ensemble in Space mission. This expertise is developing enabling techno logy towards optical coupling to crystals, targeting microwave-optical quantum conversion applications within a hybrid quantum system paradigm.
Recently, cold atoms in lattices blossomed as good candidates to mimic the prop- erties of electrons in solid state systems and to simulate other quantum systems. However, experimental techniques currently use optical lattices in the far-field. This limit the lattice spacing to λ/2, thus the relevant energy scale (tunneling and interaction), making it difficult to enter deeply into the proper quantum regimes to observe magnetic quantum correlations or strongly correlated phases. Our project aims at reducing the lattice period to bridge the gap between solid state ( ̊A) and far field lattice (500nm) by developing an hybrid quantum system of Bose and Fermi quantum gas in close proximity of a nano-structured surface generating sub-wavelength lattice potentials. To push toward this goal, we first developed a novel method to transport and then trap an ultracold atomic cloud in close vicinity of a surface. We will discuss about the early stage atom-chip produced, and report on some tests about the transport sequence. By measuring the power spectral density of the trap parameters, we can predict the noise- induce heating of the trapped cloud. In order to work with such system, one need to be able to address individually each sites with a resolution under the standard PSF limit. We implemented a tunable sub-wavelength imaging system with a theoretical resolution of 30nm that we used to resolve the wave-packet of a cloud in a single lattice site. This scheme involves two superimposed optical lattices, one at 1064nm and one at 1529nm, whose interfringe can be tuned. We present hereafter the experimental setup in detail and show interesting results we obtained.
The entry into the new millennium was marked in the quantum community by the first experimental realizations of the Bose-Einstein condensation of atoms in a vapor, achieved in different research groups. Twenty-five years later, such systems are 'routinely' produced and are the core of many experiments. At the frontier between condensed matter their y, quantum optics, and atomic physics, ultra-cold atoms are subjects of high scientific interest.Ultra-cold gas can be trapped in optical lattices, giving a realistic way of experimentally realizing a new range of lattice Hamiltonians, that are used to simulate condensed matter systems. In these simulations, ultra-cold atoms are used to mimic the behavior of electrons in a solid-state material and could be used to simulate a wide range of complex condensed matter phenomena, such as the fractional quantum Hall effect, topological insulators, and high-temperature superconductivity.In order to study such systems, diffraction-limited quantum gas microscopes have emerged as a way to manipulate and detect atoms trapped in lattice potentials. Using far-field interference, experiments have mainly been restricted to a lattice spacing of 500 nm. This limits the speed of dynamics of all physical processes.Higher energy regimes could be accessed by reducing the lattice spacing. For this purpose, one of the long-term goals of the team is to trap atoms in the near-field of a surface and to make use of the Casimir-Polder forces to shape sub-wavelength potentials. Thanks to nano-fabrication capabilities, the spacing can be reduced to a few tens of nanometers. However, this requires to adapt the imaging techniques to observe cold-atoms with sub-wavelength spatial resolutions.In this PhD thesis, I report first on the advances toward implementing an atom chip in our experiment, which will serve as an integrated platform to manipulate the quantum gas. I present simulations and study an experimental solution allowing the cloud to be transported to the near-field. The method is based on the interference of a laser radiation in the near field of a rotating surface. It has been fully simulated, and the limitations have been numerically and experimentally assessed. I conclude this part by presenting the first model of chip that has been fabricated.In a second part, I report on the development of a sub-wavelength imaging method of cold Rubidium 87 atoms which is based on excited state dressing. I detail the concept of this nano-metric spatial resolution method and apply it to super-resolve a single longitudinal wave function trapped in a tight lattice that exhibits a width below 30 nm.
Ultra-cold atoms systems used as quantum simulators offer an alternative way to simulate many-body systemsbehaviour in condensed matter. Indeed, we can create artificial matter with optical lattices : the stationnarywave reproduces the potential wells in the crystalline structure. Moreover, the big advantage of using cold atomsis that the parameters of the simulated crystal can be well controlled so that we can understand the electricaland magnetism properties of the condensed matter such as conductivity, ferromagnetism ...The commonapproach for generating optical lattices is interfering two laser beams in one dimension. The lattice spacing islimited by the interfringe, which is half the wavelength. However, the more the lattice spacing decreases, themore the interaction energies increase [3].In the new ongoing project, we are going to produce subwavelengthlattices by irradiating a nanostructure gold layer. The subwavelength potential is got thanks to the control ofthe interactions between the beams, the atomic cloud, and the nanostructured surface. This system will be ableto study new interaction regimes with very high tunability (different lattice geometries, impurities...).
During my PhD, I participated in the full setup from scratch of an experiment that aims at cooling down and manipulating two fermionic alkaline atomic species, 6Li and 40K. Our goal is to study ultracold Fermi mixtures with mass imbalance, and to realize a flexible quantum analog simulator. In fact, for certain quantum many-body problems, such as high critical temperature superconductivity and frustrated anti-ferromagnetism, there is neither complete analytical nor numerical solution. Therefore, cold atoms systems, due to their purity and their high degree of tunability, even on their interaction itself, offer an interesting complementary point of view in the study of those phenomena. As far as the experimental setup is concerned, we built an ultra-high vacuum system, a complete and stable laser source for each species, as well as two performing atomic sources, a 6Li Zeeman slower and a 40K bidimensionnal magneto-optical trap; most of the optical and electrical quantities, as well as the imaging diagnostics, being computer controlled. Once those preliminary steps have been performed and optimized, we could obtain an efficient double magneto-optical trap, containing typically 5x10^9 atoms of 6Li and 8x10^9 atoms of 40K. In this configuration, we produced the first 6Li40K* heteronuclear molecules by photoassociation, for which we identified 70 rovibrational lines. In a second part, I describe in detail the magnetic transport of the atomic mixture, between the magneto-optical trap chamber and a science cell, located in an ultra-high vacuum region with large optical access. The complete setup, from its design to its experimental implementation and optimization, as well as the development of the program and the useful numerical diagnostics, are the heart of my work. The transport efficiency could be tested and optimized, allowing for an efficient transfer of the mixture in the science cell. Thus, after this thesis, all the experimental tools are operational in order to allow for evaporative cooling of the mixture in an optically plugged magnetic trap. Therefore, the field is open for quantum simulation and understanding of many-body problems in ultracold Fermi mixtures.
The work described in this thesis is related to various projects that I worked on towards the production of ultra-cold ensembles of ⁸⁵Rb, ⁸⁷Rb and fermionic ⁶Li. In the past few years, ultra-cold atomic gases have evolved into a mature field of research, driving various theoretical and experimental groups towards new possibilities. This thesis starts with an overview of the research direction of the field and the lab in particular, to use ultra-cold fermionic atoms as quantum simulators for several condensed matter problems. It discusses the experimental route to quantum degeneracy in a sample of ultra-cold atoms and techniques to get there. The rest of the thesis primarily discusses the first step to degeneracy- production of ultra-cold ensembles of rubidium and lithium. It starts with the theoretical concepts that enable laser cooling and trapping. The interaction between light and atoms and how it leads to a decrease in temperature of the ensemble is discussed. The limits of different cooling mechanism with relevance of the atoms of interest are described. The starting point for all laser cooling experiments is an atomic source, the details of the requirements and efficiency of different atomic sources is discussed, emphasizing our choice of sources for the two atoms. Other technical details such as the vacuum system and the control system for the experiment are briefly discussed. Preliminary data from our first ensembles of ultra-cold lithium and rubidium is shown. At the end, the planning and progress of the first experiments that we aim to achieve with these ultra-cold atoms namely looking for Feshbach resonances and studying the effect of DC electric fields on them, and studies with ultra-cold lithium atoms in optical lattices, is discussed.