Kavli Affiliate: Oskar Painter
| First 5 Authors: Harry Levine, Arbel Haim, Jimmy S. C. Hung, Nasser Alidoust, Mahmoud Kalaee
| Summary:
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 experimentally demonstrate that a "dual-rail
qubit" consisting of a pair of resonantly-coupled transmons can form a highly
coherent erasure qubit, where the erasure error rate is given by the transmon
$T_1$ but for which 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 mid-circuit
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.
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