Mainz 2026 – scientific programme

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A: Fachverband Atomphysik

A 3: Collisions, Scattering and Correlation Phenomena I (joint session A/MO)

A 3.5: Talk

Monday, March 2, 2026, 12:45–13:00, N 2

Protected quantum gates using qubit doublons in dynamical optical lattices — •Lars Fischer, Yann Kiefer, Zijie Zhu, Samuel Jele, Marius Gächter, Giacomo Bisson, Konrad Viebahn, and Tilman Esslinger — Institute for Quantum Electronics & Quantum Center, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich

Scalable quantum computation relies on configurable qubit connectivity through system-wide, error-free transport of quantum states. Neutral atoms in optical lattices represent a promising platform for quantum computing, where collisional gates provide a controlled mechanism for quantum logic. Here, we present a purely geometric two-qubit SWAP gate that transiently populates qubit doublon states of fermionic atoms in a dynamical optical lattice. Using atomic spin singlets of fermionic potassium-40, we demonstrate the experimental realisation of this quantum holonomy enabled by doublon states. The gate mechanism is based on a geometric evolution in which dynamical phases are entirely absent, making the mechanism intrinsically robust against fluctuations and inhomogeneities in the confining potentials.

We report a loss-corrected two-qubit SWAP gate fidelity of 99.91(7)%, measured across an ensemble of more than 17,000 atom pairs. Combined with tunable atomic collisions, we realise a universal set of two-qubit gates, paving the way toward large-scale, highly connected quantum processors. Our scheme, based on topological pumping of atoms, establishes the foundation for a fault-tolerant computational platform.

Keywords: Quantum Computing; Collisional Quantum Gates; Ultracold atoms; Topological Transport; Particle Entanglement