Cavity quantum electrodynamics (cQED) is a central paradigm for the study of open quantum systems.The study of cQED aims to understand phenomena such as quantum decoherence and the emergence of semiclassical dynamics, striving to better connect empirical realism and axiomatic theory.Within this quantum regime, it is possible to prepare a mechanical oscillator in pure quantum states and observe how it evolves under interaction with the environment.Furthermore, quantum coupling of these mechanical systems to ultracold atomic systems offers a novel approach to controlling macroscopic systems at the quantum level.We are laying the experimental groundwork for hybrid atom-optomechanics where the optomechanical coupling is atom-mediated using an ultracold 6 Li atomic gas.The ultracold 6 Li gas is to be in close proximity with and strongly coupled to a high quality factor fused silica microtoroid resonator by confinement in a two-color evanescent wave optical dipole trap.The infrastructure, construction, and operation of an ultracold Li apparatus is presented and followed with a report of the characterization of our first observation of an ultracold lithium gas in the laboratory.Specifically, this thesis briefly covers theory and experimental implementation of laser cooling methods, development of the homemade laser and laser amplifier systems, and development and construction of the homemade electronic systems for the precise control and monitoring of atomic parameters.Finally, magneto-optical trap characterization methods and images of the cold atoms using time-dependent fluorescence imaging are shown and followed with a discussion of further work. ACKNOWLEDGMENTSMany people have contributed to the success of this thesis, and I owe thanks to all of them.First, I am grateful to Prof. Mukund Vengalattore for giving me the opportunity to be a part of his group and to work on building the lithium experiment.His incredible passion, never-ending myriad of ideas he contributed to this work, and the exceptional work environment he created have been crucial to the success of this thesis and to my development as a masters student.I owe much thanks to my colleague in the lithium-6 experiment, Yogesh Patil, for his invaluable insights and close to instant understanding of many of the technical difficulties and physical effects.Much of the success of this thesis results from his insights during our countless discussions.Thank you so much for the time we spent in the lab together!Many thanks to our undergraduate member, Airlia Shaffer-Moag, for a full set of crosstalk data on all 32 DIO circuits.Also, many thanks to all other group members from previous years who provided the original designs that the circuits in the lithium experiment are based upon.Finally, I am grateful to those who were not directly involved in the lithium-6 experiment but nevertheless contributed to making this thesis a successful and very pleasant one.First, I thank Lauren Aycock for her guidance, encouragement and invaluable suggestions in the lab and on this thesis.I thank Collin Reynolds for pointing out some very key circuit issues and for his constant feedback and encouragement.Finally, I thank Srivatsan Chakram for his help and insights and for his willingness to discuss my questions! b To my instructors, mentors, and colleagues.
Cavity quantum electrodynamics (cQED) is a central paradigm for the study of open quantum systems.The study of cQED aims to understand phenomena such as quantum decoherence and the emergence of semiclassical dynamics, striving to better connect empirical realism and axiomatic theory.Within this quantum regime, it is possible to prepare a mechanical oscillator in pure quantum states and observe how it evolves under interaction with the environment.Furthermore, quantum coupling of these mechanical systems to ultracold atomic systems offers a novel approach to controlling macroscopic systems at the quantum level.We are laying the experimental groundwork for hybrid atom-optomechanics where the optomechanical coupling is atom-mediated using an ultracold 6 Li atomic gas.The ultracold 6 Li gas is to be in close proximity with and strongly coupled to a high quality factor fused silica microtoroid resonator by confinement in a two-color evanescent wave optical dipole trap.The infrastructure, construction, and operation of an ultracold Li apparatus is presented and followed with a report of the characterization of our first observation of an ultracold lithium gas in the laboratory.Specifically, this thesis briefly covers theory and experimental implementation of laser cooling methods, development of the homemade laser and laser amplifier systems, and development and construction of the homemade electronic systems for the precise control and monitoring of atomic parameters.Finally, magneto-optical trap characterization methods and images of the cold atoms using time-dependent fluorescence imaging are shown and followed with a discussion of further work. ACKNOWLEDGMENTSMany people have contributed to the success of this thesis, and I owe thanks to all of them.First, I am grateful to Prof. Mukund Vengalattore for giving me the opportunity to be a part of his group and to work on building the lithium experiment.His incredible passion, never-ending myriad of ideas he contributed to this work, and the exceptional work environment he created have been crucial to the success of this thesis and to my development as a masters student.I owe much thanks to my colleague in the lithium-6 experiment, Yogesh Patil, for his invaluable insights and close to instant understanding of many of the technical difficulties and physical effects.Much of the success of this thesis results from his insights during our countless discussions.Thank you so much for the time we spent in the lab together!Many thanks to our undergraduate member, Airlia Shaffer-Moag, for a full set of crosstalk data on all 32 DIO circuits.Also, many thanks to all other group members from previous years who provided the original designs that the circuits in the lithium experiment are based upon.Finally, I am grateful to those who were not directly involved in the lithium-6 experiment but nevertheless contributed to making this thesis a successful and very pleasant one.First, I thank Lauren Aycock for her guidance, encouragement and invaluable suggestions in the lab and on this thesis.I thank Collin Reynolds for pointing out some very key circuit issues and for his constant feedback and encouragement.Finally, I thank Srivatsan Chakram for his help and insights and for his willingness to discuss my questions! b To my instructors, mentors, and colleagues.
Ultracold mixture experiments hold the promise of providing new insights into many-body quantum systems as well as ultracold chemistry and few-body phenomena. The work presented in this thesis dealt with the construction of a new apparatus for the production and study of ultracold gases of fermionic lithium-6 and bosonic caesium-133. These isotopes offer a wide tunability in their interaction strength, both in inter-species and intra-species collisions, through magnetic Feshbach resonances. Additionally, the widely different resonance frequencies of lithium and caesium enables independent control of each of the species. With this apparatus, Bose-Einstein condensates (BEC) containing 10^4 lithium Feshbach molecules are routinely produced. The cooling system for caesium has been developed in parallel and important steps towards producing ultracold caesium gases have been made. An optical dipole trap has been loaded with 2x10^6 caesium atoms and evaporative cooling towards quantum degeneracy can now be pursued. Laser, vacuum, magnetic and control systems have been developed for the implementation of this experiment. Light produced with this laser system was used to laser cool atoms, create conservative dipole traps as well as to provide means of imaging atomic clouds. Additionally, a system to produce strong magnetic fields of up to 1400 G has been established in order to exploit the wide tunability in the atomic interactions. Software that was developed for the computerised control system facilitated the coordination of all the components involved in the experimental sequence. Measurements and calculations that showcase the functionality of relevant parts of the setup are presented in this thesis. In this experiment, lithium and caesium atoms are obtained from a novel type of Zeeman slower and are loaded into a magneto-optical trap (MOT). The system is capable of doing this independently for each of the atomic species as well as sequentially. After the MOT has been loaded with atoms, they are transferred into a conservative far-off-resonance optical dipole trap. By adjusting the interactions between atoms and lowering the depth of the dipole trap, efficient evaporative cooling of lithium was carried out from which a molecular BEC was obtained. Time-of-flight measurements were used to characterise the condensate and study its expansion dynamics.
Hybrid quantum systems represent one of the most promising routes in the progress of experimental quantum physics and in the development of quantum technologies. In a hybrid quantum system two (or more) different quantum systems interact in the same experimental setup. Therefore, these composite systems benefit from both the properties of each single system and from the presence of an interaction term, leading to the emergence of new variables that can be experimentally manipulated. \nA promising hybrid quantum system is the one realized by the com- bination of an ultracold atomic gas and trapped ions. Ultracold atoms and trapped ions are two of the most studied physical systems for the implementation of several quantum technologies, like e.g. quantum simulation, quantum computa- tion, and quantum metrology. When trapped together, atoms and ions interact via an interaction potential that scales asymptotically with R^(−4), where R is the inter- particle distance, due to the electrostatic (attractive) force between the ion’s electric monopole and the atom’s induced dipole. Interestingly, this potential has a typical range on the order of hundreds of nm, i.e. approx. two orders of magnitude longer than the range of atom-atom interactions. Several studies have proposed to use this interaction to realize new quantum simulations, study few-body physics, and control atom-ion chemical reactions. \nElastic collisions between ions and atoms can be exploited to sympathetically cool the ions and try to reach the so-far elusive s-wave scattering regime, in which atom- ion collisions can lead to a quantum coherent evolution of the composite system. However, the ultracold atom-ion mixtures realized so far were not brought to the s-wave scattering regime because of the so-called “micromotion”, a driven motion affecting the dynamics of the ions trapped in Paul traps. Atom-ion collisions in the presence of micromotion cause a coupling of energy from the oscillating field of the Paul trap to the colliding particles, which can be heated up in the collision. In order to realize an atom-ion experiment in which the system could reach the s-wave scattering regime, the choice of the atomic species and the ion trapping strategy are crucial. \nWe decided to build a new experimental apparatus for the realization of an ultracold atom-ion quantum hybrid system made of a quantum gas of fermionic Lithium and trapped Barium ions. The choice for the elements ensures that atoms and ions in their electronic ground state will not undergo charge- exchange collisions, i.e. inelastic processes for which an electron is “exchanged” be- tween the two colliding particles. Additionally, the large mass ratio ensures an efficient cooling of the ion in the ultracold gas. \nFor what regards the ion trapping strategy, in order to remove the limitations set by micromotion, we conceived a new trap. This is formed by the superposition of an electric quadrupole static potential and an optical lattice along the untrapping direction of the electric quadrupole. The ions are moved into this electro-optical trap (EOT) from a standard Paul trap, in which the ions are first trapped after their production through photoionization. \nIn this thesis, I will describe how this new experimental apparatus for the real- ization of an ultracold atom-ion quantum hybrid system was conceived, designed and assembled. I will first describe the motivations for investigating atom-ion interactions in the ultracold regime. Then, I will describe the experimental techniques to trap and cool Barium ions and Lithium atoms, and how we plan to make them interact. The largest part of the thesis will be dedicated to the description of the parts of the experimental setup that I designed and realized, like the Lithium optical setup, the Barium imaging system and the electrical setup of the ion trap, including a compact RF drive based on interdependent resonant circuits that I developed for operating the Paul trap. The last chapter of the thesis is dedicated to this innovative drive.
Ultracold atoms and trapped ions are among the most formidable sources of coherent matter available in a laboratory. In a hybrid quantum system of atoms and ions, ultracold atoms and trapped ions are combined in a single experimental apparatus, thus realizing an innovative platform to experimentally investigate open problems of quantum physics from a new standpoint. An atom-ion hybrid system not only brings together the advantages of each single physical system, but moreover gives rise to atom-ion interactions, which are two orders of magnitude longer-ranged than atom-atom interactions. Despite a strong interest in atom-ion experiments in recent years, atom-ion systems have not yet been brought to an s-wave scattering regime in which atoms and ions experience a long-living coherent evolution. I will report on the advancements in the realization of an experimental apparatus in which a single trapped Barium ion will be immersed into an ultracold gas of fermionic Lithium. In particular, I will report on the a number of technical advancements that we have realized in order to achieve the highest possible level of control over the atom-ion quantum mixture. These include a new ion trap for creating confining potentials for the ions with a combination of optical and electric fields [1], and a high-finesse optical cavity for confining and rapidly cool neutral atoms via unconventional sideband cooling [2]. Notably, this apparatus was recently used to successfully trap Ba+ ions, thus realizing the first ion trapping experiment in Italy. [1] E. Perego, L. Duca, C. Sias Appl. Sci. 10, 2222 (2020) [2] F. Berto, E. Perego, L. Duca, C. Sias arXiv:2107.04110 Phys. Rev. Research (in press)
My first thanks go to Jeff Kimble for providing me the opportunity to work in this exciting field, and to be a part of his outstanding research group. Needless to say, his tireless efforts have played an instrumental role in the progress we’ve made these past few years. Beyond this direct contribution, I have learned immeasurable amounts from him, not only in terms of scientific skills both theoretical and experimental. I also owe a debt of gratitude to my colleagues from Lab 11, where all the work in this thesis was done. This list begins with David Vernooy and Jun Ye, who constructed the heart of the experiment, which continues to beat to this day. Postdoctoral fellows Dan Stamper-Kurn and Hanns-Christoph Nägerl provided excellent leadership, and I learned a great deal from both of them. Special thanks also go to Joe Buck, with whom our first real breakthroughs were achieved. Joe was a great friend and colleague throughout both the good times and the months before that weren’t quite as pleasant. Alex Kuzmich provided several important scientific contributions to our lab, which are greatly appreciated. Andreea Boca, David Boozer and Russ Miller have been tremendous friends and co-workers, and a separate paragraph of gratitude could be written about each of them. Amazing progress already being made as of this writing is a testament to the fact that the lab could not be
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.
In modern quantum technology, different quantum systems have properties that make them effective for some tasks and less beneficial for others. Integrating these systems together into a single quantum hybrid system, exploiting the advantages of each systems strengths while suppressing their disadvantages, can advance the total performance. On-chip quantum hybrid systems coupled to an ensemble of ultracold atoms show a great potential for advancing quantum technology, because they combine the long coherence time of the atomic ensemble with access to conventional read-out techniques provided by the chip. This thesis presents an apparatus that we have built to carry out experiments with coupling ultracold 87Rb gases to various systems, including nanomechanics and optical cavities. The apparatus operates at ultra-high vacuum conditions, required for experiments with ultracold gases, and its design allows us to easily and quickly switch between different on-chip devices to perform and study quantum hybridization with ultracold gases. Such versatility is provided by separating the region where the ultracold gas is created from the location of the chip, and implementing a system which can optically transfer the atoms between these two regions. In this work we also describe atom cooling techniques used in this experiment, including magneto-optical trapping, sub-Doppler cooling in optical molasses and evaporative cooling. These methods have demonstrated cooling to temperatures below 100 uK. We also discuss a setup for optimal optical-dipole transport. Finally, we theoretically consider magnetic coupling between atoms and nanomechanical oscillators and propose using the Landau-Zener transitions as a method for reducing or measuring mechanical temperature of the resonators, and to create quantum entanglement between multiple devices.