Experiments with Potassium-Cesium Quantum Gas Mixtures

The achievement of Bose-Einstein condensation in ultracold atomic gases 20 years ago has been a scientific breakthrough not only for the field of atomic and optical physics, but in fact for nearly all of physics and its nearby disciplines. Fields as disjunct as quantum optics and quantum information, precision measurement and sensing, foundations of physics, and condensed matter physics, to name a few, benefit greatly from the existence of Bose- Einstein condensates (BEC). In essence, the BEC, a zero-entropy many-body quantum system that forms for bosonic particles at temperatures in the nanokelvin range, is the ideal starting point for a multitude of novel experiments and investigations, e.g. on quantum registers made out of ultracold atoms, on many-body quantum entanglement, on quantum engineering of novel many-body states, on quantum phases and quantum phase transitions, on quantum many-body dynamics and excited states, on precision spectroscopy and interferometry, on molecular quantum systems, etc. In particular, ultracold quantum gases offer a quantum test bed for new quantum effects and quantum phenomena that will inevitably occur in future electronic devices in view of the continuing miniaturization of device structures towards the single atom level, e.g. nano-wires with the thickness of an atom, and in view of the continuously improving device quality. They allow us to perform quantum simulations of quantum model systems. By engineering and synthesizing novel atomic and molecular many-body systems in highly controllable traps and with very good control over interaction properties, we aim at getting a deeper understanding of strongly correlated quantum matter and advancing our knowledge on new forms of quantum matter, in particular in low dimensionality, probing thermodynamics and transport processes at the quantum level, implementing quantum simulation schemes that benchmark classical computations, and investigating into dynamical processes in quantum many-body systems. The project relies on an existing versatile K-Cs quantum gas mixture apparatus that has been set up in the PIs group over the course of the past 3.5 years and it makes use of the highly advanced ultracold atom and molecule toolbox. Using quantum gas mixtures of potassium (K) and cesium (Cs) atoms confined to lattice potentials we will implement high- resolution, single-site imaging on quantum gases of Cs atoms with tunable interactions and on spin mixtures of fermionic K atoms with the aim to engineer and probe novel quantum gas phases of interacting bosons and fermions. In particular, the project aims at creating low- entropy many-body systems of interacting fermionic dipoles (KCs) with the goal to investigate into novel forms of superfluidity and to study the properties of spin crystals.

The achievement of Bose-Einstein condensation in ultracold atomic gases 25 years ago has been a scientific breakthrough not only for the field of atomic and optical physics, but in fact for nearly all of physics and its nearby disciplines. Fields as disjunct as quantum optics and quantum information, precision measurement and sensing, foundations of physics, and condensed matter physics, to name a few, benefit greatly from the existence of Bose-Einstein condensates (BEC). In essence, the BEC, a zero-entropy many-body quantum system that forms for bosonic particles at temperatures in the nanokelvin range, is the ideal starting point for a multitude of novel experiments and investigations, e.g. on quantum registers made out of ultracold atoms, on many-body quantum entanglement, on quantum engineering of novel many-body states, on quantum phases and quantum phase transitions, on quantum many-body dynamics and excited many-body quantum states, on precision spectroscopy and interferometry, on molecular quantum systems, etc. In particular, ultracold quantum gases offer a quantum test bed for new quantum effects and quantum phenomena that will inevitably occur in future electronic devices in view of the continuing miniaturization of device structures towards the single atom level, e.g. nano-wires with the thickness of an atom, and in view of the continuously improving device quality. They allow us to perform quantum simulations of quantum model systems with the hope to elucidate the phenomenon of high-temperature superconductivity. The present project aims at generating a new class of quantum simulators, namely molecular quantum simulators based on ultracold strongly-interacting KCs dipolar molecules in the regimes of Bose and Fermi quantum degeneracy. By means of an elaborate quantum engineering protocol, the molecules in the regime of zero temperature are to be produced out of quantum degenerate atomic mixtures of K and Cs atoms. In the course of the project, which will now be continued with the PI's recently acquired ERC Advanced Grant, we have identified suitable scattering resonances for the production of KCs molecules, have implemented quantum gas transport of atoms across long distances, have developed further advanced laser cooling techniques as needed for sample preparation, have tested various techniques for sample mixing, and have engaged in constructing the next-generation quantum gas apparatus that is expected to allow full quantum control of the molecular sample together with single-molecule detection. In accordance with the initial plans, the project aims at creating low-entropy many-body systems of interacting bosonic and fermionic dipoles with the goal to investigate into novel forms of superfluidity and to study the properties of spin crystals.