Controlled Immersion of Single Neutral Atomic Impurities into an Ultracold Quantum Gas of a Different Atomic Species

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Coherent control of quantum systems with single-particle resolution opens the possibility to shed light on quantum mechanical phenomena on a fundamental level and exploit them for engineering arbitrary quantum states. In this project, such a control is envisioned by controlled immersion of single or few neutral atoms of one atomic species in a quantum gas of another species. The project will devise tools for independent positioning and controlling the two sub-systems by species-selective optical traps; for independent read-out by standard absorption and fluorescence imaging; and for tuning and switching the interaction strength by inter-species Feshbach resonances. Two major scenarios will be explored with this system: First the project will address the question if cooling of single qubits in a quantum gas is possible while preserving their internal state coherences, highly relevant for quantum information purposes. Second, for strong inter-species interaction, the system is well described by a quasi-particle approach, where atoms from the quantum gas surround the impurities. Such polarons, analogous to electrons dressed by phonons in usual solid state physics, have remarkable properties which cannot be found in usual solid state systems. The project will create and investigate polarons in the crossover between single and many impurity atoms and study their properties, such as their self-localization.