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 1497 MHz. We demonstrate ground-state hyperfine qubit coherence times up to T 2 ∗ = 22 − 2 + 2 s and T 2 = 55 − 14 + 59 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.