Driving the complex dynamics of physical systems to perform a specific task is extremely useful but challenging in several fields of science, and especially for fragile quantum mechanical systems. Even harder, and often unfeasible, is to invert the time arrow of the dynamics, undoing some physical process. We theoretically and experimentally drive forth and back through several paths in the five-level Hilbert space of a Rubidium atom in the ground state. We achieve such an objective applying optimal control strategies to a Bose-Einstein condensate on an Atom chip via a frequency modulated RF field. We further prove that backward dynamical evolution does not correspond to simply inverting the time arrow of the driving field neglecting the only-system part of the dynamics. Apart from the relevance for the foundations of quantum mechanics, these results are important steps forward in the manipulation of quantum dynamics that is crucial for several physical implementations and very promisingly powerful quantum technologies.

C. Lovecchio et al.,
Optimal preparation of quantum states on an atom chip device
Phys. Rev. A 93, 010304(R) (2016)

Chiral edge states are a hallmark of quantum Hall physics. In electronic systems, they appear as a macroscopic consequence of the cyclotron orbits induced by a magnetic field, which are naturally truncated at the physical boundary of the sample. Here we report on the experimental realization of chiral edge states in a ribbon geometry with an ultracold gas of neutral fermions subjected to an artificial gauge field. By imaging individual sites along a synthetic dimension, we detect the existence of the edge states, investigate the onset of chirality as a function of the bulk-edge coupling, and observe the edge-cyclotron orbits induced during a quench dynamics. The realization of fermionic chiral edge states is a fundamental achievement, which opens the door towards experiments including edge state interferometry and the study of non-Abelian anyons in atomic systems.

M. Mancini et al.,
Observation of chiral edge states with neutral fermions in synthetic Hall ribbons
Science 349, 1510 (2015)

See also the Science Perspective by A. Celi and L. Tarruell:

A. Celi and L. Tarruell
Probing the edge with cold atoms
Science 349, 1450 (2015)

It is generally impossible to probe a quantum system without disturbing it. However, it is possible to exploit the back-action of quantum measurements and strong couplings to tailor and protect the coherent evolution of a quantum system. This is a profound and counterintuitive phenomenon known as quantum Zeno dynamics (QZD). Here we demonstrate QZD with a rubidium Bose-Einstein condensate in a five-level Hilbert space. We harness measurements and strong couplings to dynamically disconnect different groups of quantum states and constrain the atoms to coherently evolve inside a two-level subregion. In parallel to the foundational importance due to the realization of a dynamical superselection rule and the theory of quantum measurements, this is an important step forward in protecting and controlling quantum dynamics and, broadly speaking, quantum information processing.

F. Schӓfer et al.,
Experimental realization of quantum zeno dynamics
Nat. Commun. 5, 3194 (2014)

S. Gherardini et al.,
Ergodicity in randomly perturbed quantum systems
Quantum Sci. Technol. 2, 015007 (2017)

Carlo Sias has been awarded with an ERC Starting Grant! The title of the project is "PlusOne: An ultracold gas plus one ion: advancing Quantum Simulations of in- and out-of-equilibrium many-body physics”. Congratulations!

Ultracold atoms and trapped ions are among the most powerful tools to study quantum physics. On the one hand, ultracold neutral 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. Quantum gases have been used extensively in recent years to realize quantum simulations of fundamental models of condensed matter, the solutions of which are often too complex to be computed. 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. Moreover, trapped ions have been recently used as a quantum simulator, making the path of the two subjects of ultracold atoms and trapped ions even more entangled.

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 about ten groups in the world have built or are currently building experimental setups in which different pairs of atoms and ions are used together. piccola sito The reason for this interest is based on the several innovative ingredients that are available – many more than in traditional atomic physics experiments. At the fundamental level, atoms and ions interact through a potential that is much more long-ranged with respect to the interaction between ultracold atoms (scaling with R^-4 instead of R^-6, where R is the internuclear separation), and one can exploit the different techniques to manipulate atoms and ions to exert more control in the hybrid system. With this control 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.