In recognition of his exceptional thesis: “Quantum Liquid Droplets in a Mixture of Bose-Einstein Condensates” Cesar Cabrera received the ICFO PhD Thesis award in December 2019 at the ICFO Institute in Spain. more

Elementary particles carry several quantum numbers, such as charge and spin. However, in an ensemble of strongly interacting particles, the emerging degrees of freedom can fundamentally differ from those of the individual constituents. For example, one-dimensional systems are described by independent quasiparticles carrying either spin (spinon) or charge (holon). Here, we report on the dynamical deconfinement of spin and charge excitations in real space after the removal of a particle in Fermi-Hubbard chains of ultracold atoms. more

Some isolated quantum systems with disordered potentials fail to ever reach thermal equilibrium, a phenomenon known as many-body localization (MBL). An outstanding question concerns the stability of this phenomenon. While it is well known that exposing the quantum system to the outside world destroys localization, it is not clear what happens when the MBL system is connected to another small quantum system known as a quantum bath. Does a quantum bath destroy the localization, and if so, how small can that bath be? more

Strongly-interacting gauge theories are extremely challenging to access with conventional numerical techniques. Here, we take a first step towards quantum simulation of gauge theories by implementing a Floquet-based method with two-component ultracold bosons in a double-well potential. For resonant periodic driving at the on-site interaction strength and an appropriate choice of the modulation parameters, the effective Floquet Hamiltonian exhibits Z2 symmetry. more

Here we report the microscopic real-space characterization of magnetic polarons in a doped Fermi–Hubbard system, enabled by the single-site spin and density resolution of our ultracold-atom quantum simulator. We reveal the dressing of doublons by a local reduction—and even sign reversal—of magnetic correlations, which originates from the competition between kinetic and magnetic energy in the system. The experimentally observed polaron signatures are found to be consistent with an effective string model at finite temperature. more

Typically, direct optical access to molecular constituents is out of reach due to their tiny size in the sub-nanometer regime. Because highly-excited Rydberg atoms feature strong interactions even at distances of micrometers, two Rydberg atoms can form huge molecules, comparable to the size of small bacteria and larger than optical wavelengths. more

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