Interfacing epitaxial rare earth spins with superconducting circuits for high-sensitivity ESR*

Hybrid quantum systems interfacing superconducting circuits with solid-state spin ensembles provide a practical route to realizing long-term microwave quantum memories and high-sensitivity inductive electron spin resonance (ESR) detection [1,2]. Specifically, ensembles of erbium ions are a promising platform for quantum networks and transduction [3] due to their long coherence times and telecom band optical transition at 1.54 μm. We report on pulsed and continuous wave ESR spectroscopy measurements of erbium dopants in Y₂O₃ [4] performed at millikelvin temperature using a microwave resonator. Using a superconducting low impedance resonator on epitaxially grown thin-film Y₂O₃ will allow for further increased coupling rates between the cavity photons and electron spins on the order of kHz.

[1] A. Bienfait et al., Nature Nanotechnology 11, 253-257 (2016)
[2] C. Eichler et al., Phys Rev Lett. 118, 037701 (2017)
[3] Lewis A. Williamson et al., Phys. Rev. Lett. 113, 203601 (2014)
[4] Supratik Guha et al., Appl. Phys. Lett. 80, 766 (2002)