<p>Quantum computing represents a central challenge in modern science. Neutral atoms in optical lattices have emerged as a leading computing platform, with collisional gates offering a stable mechanism for quantum logic<sup><CitationRef AdditionalCitationIDS="CR2 CR3 CR4 CR5 CR6 CR7 CR8 CR9" CitationID="CR1">1</CitationRef>–<CitationRef CitationID="CR10">10</CitationRef></sup>. However, previous experiments have treated ultracold collisions as a dynamically fine-tuned process<sup><CitationRef AdditionalCitationIDS="CR12 CR13 CR14 CR15 CR16 CR17 CR18 CR19 CR20 CR21" CitationID="CR11">11</CitationRef>–<CitationRef CitationID="CR22">22</CitationRef></sup>, which obscures the underlying quantum geometry and quantum statistics crucial for realizing intrinsically robust operations. Here 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<sup><CitationRef CitationID="CR23">23</CitationRef></sup>. 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. When combined with recently developed topological pumping methods for atom transport<sup><CitationRef CitationID="CR16">16</CitationRef></sup>, our results pave the way for large-scale, highly connected quantum processors. This work introduces a new model for quantum logic that transforms fundamental symmetries, including quantum statistics, into a powerful resource for fault-tolerant computation.</p>

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Protected quantum gates using qubit doublons in dynamical optical lattices

  • Yann Kiefer,
  • Zijie Zhu,
  • Lars Fischer,
  • Samuel Jele,
  • Marius Gächter,
  • Giacomo Bisson,
  • Konrad Viebahn,
  • Tilman Esslinger

摘要

Quantum computing represents a central challenge in modern science. Neutral atoms in optical lattices have emerged as a leading computing platform, with collisional gates offering a stable mechanism for quantum logic110. However, previous experiments have treated ultracold collisions as a dynamically fine-tuned process1122, which obscures the underlying quantum geometry and quantum statistics crucial for realizing intrinsically robust operations. Here 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 absent23. 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. When combined with recently developed topological pumping methods for atom transport16, our results pave the way for large-scale, highly connected quantum processors. This work introduces a new model for quantum logic that transforms fundamental symmetries, including quantum statistics, into a powerful resource for fault-tolerant computation.