Hyperfine Structure and Coherent Dynamics of Rare Earth Spins Explored with Electron-Nuclear Double Resonance at Sub-Kelvin Temperatures

TL;DR

This paper presents an ultralow-temperature ENDOR spectroscopy platform to study the hyperfine structure and coherence of rare-earth spins, revealing long coherence times and detailed energy levels relevant for quantum memory applications.

Contribution

The study introduces a novel experimental platform for ultralow-temperature ENDOR spectroscopy and provides detailed hyperfine structure measurements of rare-earth spins without relying on a reconstructed spin Hamiltonian.

Findings

Achieved electron coherence times over 2 ms at 100 mK.

Measured hyperfine energy levels directly using ENDOR.

Demonstrated long spin population lifetimes suitable for quantum memory.

Abstract

An experimental platform of ultralow-temperature pulsed ENDOR (electron-nuclear double resonance) spectroscopy is constructed for the bulk materials. Coherent property of the coupled electron and nuclear spins of the rare-earth (RE) dopants in a crystal (143Nd3+:Y2SiO5) is investigated from 100 mK to 6 K. At the lowest working temperatures, two-pulse-echo coherence time exceeding 2 ms and 40 ms are achieved for the electron and nuclear spins, while the electronic Zeeman and hyperfine population lifetimes are more than 15 s and 10 min. With the aid of the near-unity electron spin polarization at 100 mK, the complete hyperfine level structure with 16 energy levels is measured using ENDOR technique without the assistance of the reconstructed spin Hamiltonian. These results demonstrate the suitability of the deeply cooled paramagnetic RE-doped solids for memory components aimed for quantum communication and quantum computation. The developed experimental platform is expected to be a powerful tool for paramagnetic materials from various research fields.