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QI: Fachverband Quanteninformation

QI 2: Implementations I

QI 2.4: Vortrag

Montag, 9. März 2026, 10:30–10:45, BEY/0245

Hyperfine spectroscopy of rare-earth ions in CaWO₄ using broadband electron spin resonance — •Georg Mair^1,2, Ana Strinić^1,2,3, Achim Marx¹, Kirill Fedorov^1,2,3, Hans Huebl^1,2,3, Rudolf Gross^1,2,3, and Nadezhda Kukharchyk^1,2,3 — ¹Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany — ²School of Natural Sciences, Technische Universität München, 85748 Garching, Germany — ³Munich Center for Quantum Science and Technology, 80799 München, Germany

The spin states of rare-earth ions doped into crystals provide a promising platform for quantum memories, owing to their long coherence times and frequency compatibility with superconducting quantum circuits. We investigate dilute ensembles of erbium and ytterbium ions in CaWO₄ crystals at millikelvin temperatures using broadband electron spin resonance spectroscopy based on superconducting coplanar waveguides. This approach enables the precise detection of zero-field and low-field spin transition spectra. Hyperfine and quadrupolar interactions emerging from the nuclear spins of ¹⁶⁷Er, ¹⁷¹Yb, and ¹⁷³Yb give rise to a rich microwave spectrum below 4 GHz, from which we identify Zero First-Order Zeeman (ZEFOZ) shift transitions. By measuring coherence properties of individual hyperfine spin transitions, we find Hahn echo coherence times of tens of microseconds to milliseconds. Our broadband spectroscopy approach thus enables not only the fitting of full spin Hamiltonians, but also the identification and validation of long-lived spin transitions.

Keywords: Rare-earth ions; Quantum memory; Microwave; Spectroscopy; Hyperfine