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  • Open Access

Coherence of Microwave and Optical Qubit Levels in Neutral Thulium

D. Mishin1, D. Tregubov1, N. Kolachevsky1,2, and A. Golovizin1,2,*

  • *Contact author: artem.golovizin@gmail.com
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PRX Quantum 6, 040329 – Published 10 November, 2025

DOI: https://doi.org/10.1103/f8xg-w57m

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 T2∗=22−2+2 s and T2=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.

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Popular Summary

Neutral atoms are one of the leading platforms for quantum computing, with current research primarily focused on alkali (e.g., Cs and Rb) and alkaline-earth (e.g., Sr and Yb) elements. Thulium, with its unique electronic structure, makes it possible to merge their advantages: a robust qubit encoded in hyperfine levels and a rich energy-level structure for state manipulation.

In this work we focus on the coherence time of qubit levels, a key parameter that often limits the fidelity of quantum operations and the storage time of quantum states. For a hyperfine qubit in thulium, we demonstrate a remarkably long coherence time of up to one minute with minimal external control, a value that is competitive with the record for neutral atoms. Furthermore, we demonstrate coherent transfer and storage of the qubit state in a metastable level—the first step for realization of optical-metastable-ground-state architecture in thulium atoms. We also demonstrate state-selective readout, which can be used to detect qubit subspace leakage.

To our knowledge, this is the first study of qubits in neutral thulium, and the broad spectrum of available transitions enables further advancement of the techniques demonstrated in this work. We also expect the coherence time and state manipulation fidelities to improve upon switching to single atoms in an optical tweezer array—a next step in developing the thulium platform for quantum computing.

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PRX Quantum 6, 040329– Published 10 November, 2025
  • Received 19 August 2025
  • Accepted 10 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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