High-cooperativity coupling of a rare-earth spin ensemble to a superconducting resonator using yttrium orthosilicate as a substrate

Abstract

Yttrium orthosilicate (Y${}_2$SiO${}_5$, or YSO) has proved to be a convenient host for rare-earth ions used in demonstrations of microwave quantum memories and optical memories with microwave interfaces, and shows promise for coherent microwave--optical conversion owing to its favourable optical and spin properties. The strong coupling required by such microwave applications could be achieved using superconducting resonators patterned directly on Y${}_2$SiO${}_5$, and hence we investigate here the use of Y${}_2$SiO${}_5$ as an alternative to sapphire or silicon substrates for superconducting hybrid device fabrication. A NbN resonator with frequency 6.008 GHz and low power quality factor $Q\approx 400000$ was fabricated on a Y${}_2$SiO${}_5$ substrate doped with isotopically enriched Nd${}^{145}$. Measurements of dielectric loss yield a loss-tangent $\tan \delta =4\times 10^{-6}$, comparable to sapphire. Electron spin resonance (ESR) measurements performed using the resonator show the characteristic angular dependence expected from the anisotropic Nd${}^{145}$ spin, and the coupling strength between resonator and electron spins is in the high cooperativity regime ($C=30$). These results demonstrate Y${}_2$SiO${}_5$ as an excellent substrate for low-loss, high-Q microwave resonators, especially in applications for coupling to optically-accessible rare earth spins.

6 pages, 3 figures

References in corpus (9)

• The Quantum Internet
• Quantum Storage of Photonic Entanglement in a Crystal
• A magneto-optic modulator with unit quantum effciency
• Anisotropic rare-earth spin ensemble strongly coupled to a superconducting resonator
• Coherent spin control at the quantum level in an ensemble-based optical memory
• Electron spin ensemble strongly coupled to a three-dimensional microwave cavity
• Probing decoherence through Fano resonances
• High Resolution Optical Spectroscopy and Magnetic Properties of Yb3+ in Y2SiO5
• Photoluminescence of focused ion beam implanted Er${}^{3+}$:Y${}_2$SiO${}_5$ crystals