Description
Laser-cooled and trapped two-dimensional (2D) crystals comprising
hundreds of ions are now an established platform for quantum simulation and quantum sensing. Previous work has produced high-fidelity readout, individual addressing and tunable interactions through the implementation of site-resolved imaging, coherent single-ion control and spin-dependent optical dipole forces (ODFs), respectively [1, 2, 3]. ODFs have enabled Ising-like interactions in 2D crystals and hence collective spin dynamics relevant to quantum simulation. However, these have limitations that prohibit straightforward extensions of these capabilities to larger 3D ion crystals, thus motivating the exploration of alternative interaction schemes.
In this work, we investigate the implementation of Mølmer–Sørensen (MS) interactions in large crystals of trapped 9Be+ ions confined in a Penning trap [4]. The interaction is generated using Raman laser beams that couple the electronic qubit states through the intermediate level. Red- and blue-sideband frequency components allow coupling of the qubits to shared motional modes of the crystal, while being insensitive to the motional phase. This approach enables coherent spin-motion coupling and the generation of effective spin-spin interactions in arbitrary 3D ion-crystal geometries, thereby achieving favourable scaling with larger ion ensembles.
We characterise the MS interaction with 2D crystals by measuring carrier and motional sideband transitions and spin-dependent forces, which provide quantitative information about interaction strengths, mode participation, and coherence. Moreover, we show the dependence of the interaction on motional mode occupation by applying previously developed protocols for Doppler and EIT cooling [3]. Establishing reliable MS interactions is an important step toward experiments with ensembles that are natively 3D in quantum simulation and sensing protocols.
[1] J. Y. Z. Jee et al. arXiv:2604.13872 (2026).
[2] N. Makadia et al., arXiv:2606.00940 (2026).
[3] J. H. Pham et al., Adv. Quantum Technol. 7, 2400086 (2024).
[4] A. L. Carter et al., Phys. Rev. A 107, 042618 (2023).
| I am the presenting author | Yes |
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