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Entangling Ions with Engineered Light Gradients

Tommaso Faorlin1,*, Lorenz Panzl1, Phoebe Grosser1, Pablo Viñas2, Alan Kahan2, Walter Joseph Hörmann1, Yannick Weiser1, Giovanni Cerchiari1,3, Thomas Feldker4 et al.

Alexander Erhard4, Georg Jacob4, Juris Ulmanis4, Rainer Blatt1,4,5, Alejandro Bermudez2, and Thomas Monz1,4

  • *Contact author: tommaso.faorlin@uibk.ac.at
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Phys. Rev. Lett. 137, 170601 – Published 23 October, 2026

DOI: https://doi.org/10.1103/4smy-6w2n

Abstract

Spectral crowding of collective motional modes limits the fidelity of entangling interactions in trapped-ion quantum processors by inducing off-resonant coupling to spectator modes. We introduce a geometric-phase entangling interaction driven by a transverse, time-dependent structured-light force. By applying the force in a plane orthogonal to the optical propagation direction, we reduce the effects of spectral crowding while preserving single-ion addressing. The scheme is compatible with arbitrary qubit encodings, provided that the qubit states experience a differential AC Stark shift. We experimentally realize high-fidelity two-qubit gates with error rates below 5×10−3 in ion crystals containing up to 12 ions confined within a single potential well. These results establish gradient-field light-shift gates as a scalable approach to high-fidelity entanglement generation in spectrally crowded trapped-ion systems.

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Phys. Rev. Lett. 137, 170601– Published 23 October, 2026
  • Received 1 April 2026
  • Revised 30 July 2026
  • Accepted 24 September 2026
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