Quantum error correction with erasure qubits promises significant advantages over standard error correction due to favorable thresholds for erasure errors. To realize this advantage in practice requires a qubit for which nearly all errors are such erasure errors, and the ability to check for erasure errors without dephasing the qubit. We demonstrate that a “dual-rail qubit” consisting of a pair of resonantly coupled transmons can form a highly coherent erasure qubit, where transmon $T_1$ errors are converted into erasure errors and residual dephasing is strongly suppressed, leading to millisecond-scale coherence within the qubit subspace. We show that single-qubit gates are limited primarily by erasure errors, with erasure probability $p_{\text{erasure}}=2.19(2)\times {10}^{-3}$ per gate while the residual errors are $\sim 40$ times lower. We further demonstrate midcircuit detection of erasure errors while introducing $<0.1\%$ dephasing error per check. Finally, we show that the suppression of transmon noise allows this dual-rail qubit to preserve high coherence over a broad tunable operating range, offering an improved capacity to avoid frequency collisions. This work establishes transmon-based dual-rail qubits as an attractive building block for hardware-efficient quantum error correction.

中文翻译：

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使用可调谐 Transmons 演示长相干双轨擦除量子位

由于擦除错误的有利阈值，使用擦除量子位的量子纠错比标准纠错具有显着优势。要在实践中实现这一优势，需要一个几乎所有错误都是此类擦除错误的量子位，以及在不使量子位失相的情况下检查擦除错误的能力。我们证明，由一对共振耦合传输器组成的“双轨量子位”可以形成高度相干的擦除量子位，其中传输器${\mathrm{时间}}_1$错误被转换为擦除错误，并且残余相移被强烈抑制，从而导致量子位子空间内的毫秒级相干性。我们证明单量子位门主要受到擦除错误的限制，擦除概率$p_{\text{删除}}=2.19（2）\times {10}^{-3}$每个门，而残余误差是$～40$低几倍。我们进一步演示了擦除错误的中电路检测，同时引入$<0.1\%$每次检查的移相误差。最后，我们表明，传输噪声的抑制使该双轨量子位能够在广泛的可调工作范围内保持高相干性，从而提高避免频率冲突的能力。这项工作将基于 transmon 的双轨量子位建立为硬件高效量子纠错的有吸引力的构建块。