Dysprosium and erbium atoms in optical tweezers

Short answer: Dysprosium and erbium are lanthanide atoms with large magnetic moments, and two Physical Review Letters papers report loading single atoms of each into optical tweezer arrays. The dysprosium work was published in 2023 and the erbium work in 2024. Both use polarization tuning to reach near-magic trapping conditions, and the authors present them as starting points for quantum simulation. They report trapping and imaging, not quantum gates.

Dysprosium in 2023

The Physical Review Letters abstract (Bloch, Hofer, Cohen, Browaeys and Ferrier-Barbut, published November 2023) reports the preparation and observation of single dysprosium atoms in arrays of optical tweezers with a wavelength of 532 nm, imaged on the intercombination line at 626 nm. Lanthanides have an anisotropic light shift. The authors use a large difference in tensor and vector polarizabilities between the ground and excited states to tune the differential light shift, which lets them produce tweezers in near-magic or magic polarization. This gives a regime where single atoms can be trapped and imaged.

They say that using the tweezer array toolbox for lanthanides will open new research directions for quantum physics studies, taking advantage of their rich spectrum, large spin and magnetic dipole moment. That is a stated expectation.

Erbium in 2024

The second Physical Review Letters paper (Grün, White and colleagues, with the Innsbruck group, published November 2024) reports what the authors call the first successful trapping of single erbium atoms in an optical tweezer array. A single narrow-line optical transition gives deep cooling for direct tweezer loading, pairwise ejection and continuous imaging, without additional recoil suppression techniques.

Their tweezer wavelength lets them reach the magic trapping condition by tuning the ellipticity of the trapping light. They also implement an ultrafast, high-fidelity fluorescence imaging scheme using a broad transition. That allows time-resolved study of how the tweezer population evolves from many atoms to single atoms during light-assisted collisions. They extract a pair-ejection rate that qualitatively agrees with semiclassical predictions from the Gallagher-Pritchard model. The authors call the Letter a promising starting point for exploring erbium as a resource for quantum simulation in optical tweezers.

What the two have in common

Both papers use light polarization to control the differential light shift, and both rely on narrow transitions for cooling or imaging. The dysprosium abstract names a wavelength of 532 nm and the erbium abstract does not state its tweezer wavelength, so the two should not be assumed to use the same one.

Why single atoms matter

Tweezer arrays hold atoms one by one and let researchers rearrange and image them. Showing that a new species can be loaded as single atoms, with controlled light shifts, is the first step before any quantum simulation or gate work can be attempted with that species. The abstracts frame the work at that stage.

Limits

Both papers are trapping and imaging demonstrations. Neither abstract reports entanglement, gate operations or a computation. The statements about future research directions are the authors' expectations. A synopsis linked from the APS page is a separate summary and was not used for claims here.

FAQ

Why use dysprosium or erbium?

The dysprosium authors cite a rich spectrum, large spin and magnetic dipole moment.

What is a magic polarization?

A setting where the differential light shift between states is tuned away or minimized, as the dysprosium authors describe it.

What did the erbium paper measure?

A pair-ejection rate that agrees qualitatively with the Gallagher-Pritchard model, per the authors.

Were quantum gates demonstrated?

Not in these abstracts.

Which journal and years?

Physical Review Letters, 2023 for dysprosium and 2024 for erbium.