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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - PlusOne (An ultracold gas plus one ion: advancing Quantum Simulations of in- and out-of-equilibrium many-body physics)

Teaser

Summary

Ultracold atoms and trapped ions are among the most powerful tools to study quantum physics. On the one hand, ultracold atoms provide an exceptional resource for studying many-body physics, since a relatively large number of particles, typically from a few tens of thousands to several million, can be brought to quantum degeneracy. On the other hand, trapped ions provide a great resource to explore the physics of small quantum systems. They provide one of the most successful hardwares for a quantum computer, and clocks made of trapped ions are among the most precise.
Only recently, though, ultracold atoms and trapped ions have been brought together in a single experimental setup. The progress in this new research field has been extremely fast, and now several groups in the world have built or are currently building experimental setups in which different pairs of atoms and ions are used together. The reason for this interest is based on the possibility of using atom-ion interactions, which are much more long-ranged with respect to the interactions between ultracold atoms (scaling with R^-4 instead of R^-6, where R is the internuclear separation). With this interaction at hand, atom-ion quantum systems have been proposed to advance quantum simulation, quantum computation, and quantum chemistry.
In our project, we plan to realize a new generation atom-ion machine in order to realize new quantum simulations of a many-body system in the presence of one or more localized impurities. With this setup, we plan to investigate fundamental atom-ion interactions in the ultracold regime, and to use these controlled interactions to realize a platform for investigating out-of-equilibrium quantum systems and quantum thermodynamics. An hybrid quantum system of atoms and ions interacting in a - so far unexplored - full quantum regime will realize a brand new quantum system with the possibility of tuning most of the parameters of the system, so that this can be used to study existing problems and new problems of physics from a completely novel standpoint.

Work performed

The goal of the project is to realize for the first time a quantum mixture of atoms and ions in which the atom-ion collisions are at a sufficiently low energy that the atom-ion mixture evolves coherently. To this end, it was necessary to conceive and realize an utterly new experimental apparatus. Most of the activities that have been so far pursued within the project were devoted to the design and realization of this apparatus. The apparatus is composed of a large number of sources of light (lasers), a vacuum system in which an ultra-high vacuum (UHV) is created, electrodes and coils realizing electric and magnetic fields used to trap and manipulate ions and atoms, respectively, and a large number of electronic equipment pieces. Importantly, the apparatusâ€™ design is based on a number of original concepts in the realization of an ion trapping potential, in the laser cooling of neutral atoms, and in the realization of many technical parts composing the overall experimental setup, like the lasers for cooling, trapping and detecting the atoms and the ions, the electronics for controlling the experiment, the creation of intense RF fields for driving an ion Paul trap.
All these advancements were or will be soon reported in specific publications, and a patent is pending for the extended cavity diode laser design that we have conceived.
Unfortunately, a number of technical issues have slowed the progress in the experiment. These issues regarded the realization of the UHV environment in the chamber hosting the ion trap (UHV was achieved only after running three separate bake outs of the whole vacuum system), and the realization of the laser system for the neutral atoms, since we incurred in a number of failures of the active media used in the lasers, and these failures were solved only after investigating all possible problems with the private companies that provide us the active media and the electronic boards used to feed the active media.
At the moment of writing, the portion of the apparatus for realizing ion trapping has been built, neutral Ba atoms were observed in the vacuum chamber, and we should be soon ready to achieve ion trapping (remarkably, this is the first attempt to realize ion trapping in Italy). The atoms part of the apparatus is under construction, the vacuum parts will be soon baked out, and the laser system is under assembly.

Final results

The realization of an innovative experimental apparatus was made possible by the development of novel strategies for the realization of several fundamental and technical processes that are at the base of the experiment.
These advancements are or will be soon reported in scientific publications, which will be relevant not only for the atom-ion community, but for a large portion of the wide atomic physics community. These achievements are, at the moment of writing, mainly four.
1. A new electronic and software control system, based on programmable FPGA chips. While commercial electronic boards typically execute pre-determined temporal sequences of electric signals, therefore not allowing any action on the electrical outputs while the sequence is executed, the new control software and electronic boards designed by the research team make this possible. As a result, the machine-time of the experimental setup can be optimized so that two experiments can be performed at the same time. This new control system was reported in a publication in Review of Scientific Instruments (Perego et al. Rev. Sci. Instrum. 89, 113116 (2018) ).
2. A new RF drive providing the electric signal to operate a Paul trap. Paul traps are the most commonly used traps for confining charged particles. In order to function, the electrodes of the trap must be fed with an intense RF electric signal. Typically, this is realized either by using large amplifiers, or by implementing bulky resonant circuits. Instead, we have developed a new, compact and inexpensive RF drive that is confined in a single electronic board (smaller than a hand), based on a low-noise amplifier on on low-losses ferrites used to realize highly performing inductors. This new RF drive was reported in a publication in Review of Scientific Instruments (Detti et al. Rev. Sci. Instrum. 90, 023201 (2019) ).
3. A new laser source, made by a diode laser in an extended cavity configuration. The new laser source solves existing problems of instability that affect similar sources, and allows us to realize laser sources for atomic and molecular spectroscopy in a cheap and reliable way. A patent is currently pending on this novel laser design, and a scientific publication is under preparation.
4. We theoretically investigated a new strategy for realizing one-photon Li sideband cooling, with a scheme that provides a simplification with respect to the existing schemes for Li sideband cooling, which are based on the action of two lasers. The theoretical study was performed by the PI and by one member of the research team, who was awarded the best poster prize at the course 206 of the Enrico Fermi Physics School in Varenna, Italy. The prize consisted in the right of publishing a short article in the School book. The article, which has been recently submitted, is available online (arXiv:1912.08104).
At the moment of writing, the research team is close to achieve ion trapping. Importantly, this would represent the first ion trapping experiment in Italy.