Coherence of Microwave and Optical Qubit Levels in Neutral Thulium

Abstract

Hyperfine-encoded qubits in alkali atoms have established themselves as robust platforms for quantum computing, while alkaline-earth-like elements expand the state manipulation toolbox through their rich spectrum of optical transitions and metastable states. In this work, we demonstrate that thulium is a viable candidate for quantum computing, combining advantages of hyperfine qubit encoding with a rich energy-level structure of alkaline-earth-like atoms. We describe protocols for the initial state preparation and state-selective readout, and show single-qubit operations on the microwave transition at $1 497$ MHz. We demonstrate ground state hyperfine qubit coherence times up to $T_2^* = 22^{+2}_{-2}$ s and $T_2 = 55^{+59}_{-14}$ s, representing record-scale performance for neutral-atom systems. Furthermore, we show operations involving metastable optical states, including shelving for the state-selective readout as well as coherent population transfer of the ground state qubit with coherence time primarily limited by the metastable level natural lifetime of $112$ ms. These results mark the first step toward using thulium for quantum computing applications and highlight its promising characteristics.