Rare-earth quantum magnets

Quantum computers (QC) utilize the superposition principle of quantum objects: the property of being in a combination of different states simultaneously. QC promise groundbreaking research capabilities due to their inherent exponential scaling and are attracting attention across many fields of physics and beyond. The quest for a universal quantum computer spans different fields of research and several different paradigms now exist using single atoms in traps, superconducting circuits and dopants in semiconductors.

One focus of our QT group is on rare-earth (RE) fluorides as a platform for QC. LiY_1-xHo_xF₄ for example is a RE fluoride which exhibits a plethora of quantum phenomena ranging from quantum annealing to long lived coherent oscillations [18-21]. The potential of RE doped crystals for QT has been recognized early on and significant progress was recently shown [22-26]. We explore LiY_1-xHo_xF₄ and other suitable RE:LiYF₄ materials as candidates for solid-state qubits. The various energies and symmetries of different crystal field states, alongside with optical access offer a promising platform for a solid-state QC. We use our unique combination high-resolution optical spectroscopy and a high-brilliance infrared source (the Swiss Light Source Synchrotron) to gain thorough understanding of the nature of the individual states. Next, we aim to control the electronic and nuclear degrees of freedom of these states coherently, meaning we will be able to maniplate both the energy and the phase of individual RE atoms in the solid.

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