QSE Quantum Seminar: The thorium nuclear clock & nuclear quantum optics

Please join us for the QSE Center Quantum Seminar with Kjeld Beeks from EPFL, who will give the talk "The thorium nuclear clock & nuclear quantum optics" on Thursday June 6.
Location: CM 1 120

Pizzas will be available before the seminar at 12:00. All PhDs, postdocs, students, and PIs are welcome to join us.

TITLE: The thorium nuclear clock & nuclear quantum optics

ABSTRACT: The first nuclear excited state or isomer of 229Th, denoted as 229mTh, has an extremely low energy (8.4 eV/148 nm, M1+E2). Owing to its narrow resonance, the 229mTh isomer is a platform for a future extremely precise nuclear optical clock [1]. This clock would outperform contemporary atomic clocks. Owing to its nuclear nature, it would also be a new sensitive probe for fundamental physics. Recently, the very first laser spectroscopy of a nucleus has been achieved [2], and immediately confirmed [3]. This result means that very soon a nuclear optical clock can be built, and that the area of nuclear quantum optics comes within reach. In this talk I will elaborate on nuclear laser spectroscopy, growing radioactively doped crystals [4], nuclear solid-state physics effects [5] and how to build a solid-state nuclear clock (and how soon we can do this!).

The logical next question though: virtually all other nuclei have excited states much larger than 229Th, so how can we extend nuclear quantum optics to other nuclei? 235U has an excited state at 76 eV (E3), 181Ta at 6.2 keV (E1) and 197Au at 79 keV (M1+E2) which all require different technologies to excite. Currently, free electron lasers (FELs) are used to cover this vast range. Their high brightness, tuneability and narrow linewidth are ideally suited for nuclear spectroscopy. In FELs, for example Rabi oscillations in 57Fe [6] have been shown and the isomer clock transition in 45Sc was excited [7]. In my talk I will indicate some possible directions [8,9] to miniaturize nuclear spectroscopy experiments to the size of two optical tables and which possibly will lead the way to nuclear quantum optics available to all.

BIO: Kjeld received his masters from the TU/e in Eindhoven in collaboration with ASML on EUV light sources. Next, he received his PhD in physics from the TU Wien in Vienna on building a solid-state optical nuclear clock using thorium-229. The clock was being built from scratch, so this spanned from radioactive crystal growing to VUV spectroscopy and nuclear spectroscopy using x-rays. The intersection and overlap of masters and PhD projects, which involved producing VUV/EUV/x-ray light, electron bunches, solid-state and nuclear physics, resulted in the current postdoc at EPFL in the LUMES group of prof. Fabrizio Carbone. At the moment Kjeld still works on building a nuclear clock, a goal that is within sight. At the same time he is developing novel experiments that aim to bring nuclear physics to the tabletop using ultrafast lasers, electron bunches and x-ray spectroscopy. The dream is to be able to apply quantum optics to nuclei, to have small flexible setups that extremely precisely access the diverse world of isotopes and nuclei. By developing the tools to probe nuclei, the hope is to bring new applications to light: such as nuclear batteries, qubits, clocks and waste processing.

[1] Beeks et al., Nature Reviews Physics 3.4 (2021): 238-248.
[2] Tiedau, et al. Physical Review Letters 132.18 (2024): 182501.
[3] Elwell et al. Physical Review Letters (2024), Accepted, Arxiv: https://arxiv.org/abs/2404.12311 
[4] Beeks, et al. Physical Review B 109.9 (2024): 094111. 
[5] Hiraki, et al. Arxiv: https://arxiv.org/abs/2405.09577 . 
[6] Haber, et al. Nature Photonics 11.11 (2017): 720-725.
[7] Shvyd’ko, et al. Nature 622.7983 (2023): 471-475.
[8] Wu, et al. Physical Review Letters 128.16 (2022): 162501.  
[9] Gargiulo, et al. Physical Review Letters 128.21 (2022): 212502.