Protected quantum gates using qubit doublons in dynamical optical lattices - Nature

"We propose and experimentally demonstrate a purely geometric two-qubit SWAP gate by transiently populating qubit doublon states of fermionic atoms in a dynamical optical lattice. The presence of these doublon states, together with fermionic exchange anti-symmetry, enables a two-particle quantum holonomy—a geometric evolution in which dynamical phases are absent."

"This yields a gate mechanism that is intrinsically protected against fluctuations and inhomogeneities of the confining potentials. The resilience of the gate is further reinforced by time-reversal and chiral symmetries of the Hamiltonian."

"We experimentally validate this exceptional protection, achieving a loss-corrected amplitude fidelity of 99.91(7)% measured across the entire system consisting of more than 17,000 atom pairs."

"This work introduces a new model for quantum logic that transforms fundamental symmetries, including quantum statistics, into a powerful resource for fault-tolerant computation."

Neutral atoms in optical lattices are a promising platform for quantum computing. A geometric two-qubit SWAP gate has been proposed and experimentally demonstrated, utilizing qubit doublon states of fermionic atoms. This gate mechanism is protected against fluctuations due to the presence of fermionic exchange anti-symmetry and symmetries of the Hamiltonian. The experimental results show a high fidelity of 99.91(7)% across over 17,000 atom pairs. This approach offers a new model for quantum logic, leveraging fundamental symmetries for fault-tolerant computation and paving the way for advanced quantum processors.

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