Seminar – Markus Müller (PSI)

Abstract: Experiments in rare earth compounds, such as LiHoYF4 and GGG (Gd-Ga-garnet), have demonstrated very long lived, coherent quantum degrees of freedom with sharply defined excitation energies, many orders of magnitude below the scale of typical magnetic interactions (exchange, dipolar or hyperfine interactions), and with life times on the order of seconds.

The nature of these coherent entities in the midst of a solid state environment has remained a mystery for a long time. I will discuss their likely origin and argue that they arise from an intricate interplay between several nuclear and electronic spins, and exist only in long lived states out of equilibrium. The sharpness of the excitations is protected by Anderson localization of composite objects, with an unusual type of power law hopping. The emerging, well isolated degrees of freedom may be promising candidates for magnetic qubits.

Time permitting I will discuss ideas of how to realise quantum memories and gates based on electro-nuclear qubits in rare earth systems.