Coherent spin dynamics of rare-earth doped crystals in the high-cooperativity regime*

We present a study into the decoherence mechanisms of rare-earth ions doped in yttrium orthosilicate (YSO). Rare-earth ions present a viable route towards quantum transduction and quantum memory devices, in this study we explore the suitability of ¹⁷¹Yb in the microwave domain by coupling the spins to a superconducting resonator. We outline the main sources of decoherence present in the systems and provide techniques to overcome these and extend T₂ times. We explore both natural doped Yb and isotopically pure ¹⁷¹Yb and identify Yb isotopes with 0 nuclear spin as a major source of spectral diffusion. By utilising regions of low df/dB at high field and the zero-field clock transition we are able to extend coherence times to over 7 ms while maintaining a cooperativity of over 8 to a superconducting resonator.