Curator's Take
This research represents a significant step forward in making quantum error correction more practical by demonstrating remarkably fast and accurate erasure detection for dual-rail qubits in just 384 nanoseconds. The key innovation lies in using a single readout resonator symmetrically coupled to both transmons, achieving an impressive error rate of only 6 parts in 10,000 per check while introducing minimal interference with the logical qubit operations. Perhaps most exciting is their demonstration of continuous erasure monitoring during gate operations, which could dramatically reduce the overhead typically associated with error correction protocols. This hardware-efficient approach addresses one of the major bottlenecks in scaling up quantum error correction, bringing us closer to fault-tolerant quantum computers that can operate reliably for extended periods.
— Mark Eatherly
Summary
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 ($χ$-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.