Qubit Zoo

Beyond-Ten-Hour Coherence in a Decoherence-Free Trapped-Ion Clock Qubit

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Demonstrates coherence exceeding ten hours in a decoherence-free subspace (DFS) using trapped-ion clock qubits. Combines ¹⁷¹Yb⁺ clock-state qubits (first-order field-insensitive hyperfine transitions) with DFS encoding in a Yb-Ba-Yb chain: ¹⁷¹Yb⁺ ion pairs sympathetically cooled by a ¹³⁸Ba⁺ ion. A logical qubit is encoded in the DFS spanned by {|01⟩, |10⟩}, rejecting common-mode magnetic-field and microwave phase noise via correlation-based phase tracking.

Key Results

  • Fitted coherence time: (3.77 ± 1.09) × 10⁴ s ≈ 10.5 hours
  • DFS encoding over ¹⁷¹Yb⁺ clock-state pairs, sympathetically cooled by ¹³⁸Ba⁺
  • Correlation-based phase tracking suppresses common-mode magnetic and microwave phase noise
  • Extends the prior single-ion 10-minute (Wang et al. 2017) and >1-hour (P. Wang et al. 2021) records to >10 hours

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