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arXiv · 2604.16292

Fast, High-Fidelity Erasure Detection of Dual-Rail Qubits with Symmetrically Coupled Readout

Jimmy Shih-Chun Hung·Arbel Haim·Mouktik Raha·Gihwan Kim·Ziwen Huang·Ming-Han Chou·Mitch D'Ewart·Erik Davis·Anurag Mishra·Patricio Arrangoiz Arriola·Amirhossein Khalajhedayati·David Hover·Fernando G. S. L. Brandão·Aashish A. Clerk·Alex Retzker·Harry Levine·Oskar Painter
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Abstract

Erasure qubits are a promising platform for implementing hardware-efficient quantum error correction. Realizing the error-correction advantages of this encoding requires frequent mid-circuit erasure checks that are fast, high-fidelity, and scalable. Here, we realize erasure detection with a hardware-efficient circuit consisting of a single readout resonator dispersively and symmetrically coupled to both transmons of a dual-rail qubit. We use this circuit to demonstrate single-shot erasure detection in 384 ns with minimal impact on the dual-rail logical manifold, achieving a residual error per check of $6.0(2) \times 10^{-4}$, with only $8(3) \times 10^{-5}$ induced dephasing per check, and an erasure error per check of $2.54(1)\times 10^{-2}$. The high degree of matched dispersive readout coupling ($\chi$-matching) within the dual-rail qubit code space also allows us to realize a new modality: time-continuous erasure detection performed in parallel with single-qubit gates. Here we achieve a median $7.2 \times 10^{-5}$ error per gate with $< 1 \times 10^{-5}$ error induced by erasure detection. This demonstrates a reduction in erasure detection overhead as well as a crucial ingredient for soft information quantum error correction. Together, these results establish symmetrically coupled dispersive readout as a fast, hardware-efficient, and scalable component for erasure-based quantum error correction using transmon dual-rail qubits.

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Jimmy Shih-Chun Hung, Arbel Haim, Mouktik Raha, Gihwan Kim, Ziwen Huang, Ming-Han Chou, Mitch D'Ewart, Erik Davis, Anurag Mishra, Patricio Arrangoiz Arriola, Amirhossein Khalajhedayati, David Hover, Fernando G. S. L. Brandão, Aashish A. Clerk, Alex Retzker, Harry Levine, Oskar Painter. 2026-04-17. Fast, High-Fidelity Erasure Detection of Dual-Rail Qubits with Symmetrically Coupled Readout. https://arxiv.org/abs/2604.16292

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