Logical multi-qubit entanglement with dual-rail superconducting qubits

• URL: http://arxiv.org/abs/2504.12099v1
• Date: Wed, 16 Apr 2025 14:02:30 GMT
• Title: Logical multi-qubit entanglement with dual-rail superconducting qubits
• Authors: Wenhui Huang, Xuandong Sun, Jiawei Zhang, Zechen Guo, Peisheng Huang, Yongqi Liang, Yiting Liu, Daxiong Sun, Zilin Wang, Yuzhe Xiong, Xiaohan Yang, Jiajian Zhang, Libo Zhang, Ji Chu, Weijie Guo, Ji Jiang, Song Liu, Jingjing Niu, Jiawei Qiu, Ziyu Tao, Yuxuan Zhou, Xiayu Linpeng, Youpeng Zhong, Dapeng Yu,
• Abstract summary: We demonstrate a superconducting processor integrating four dual-rail erasure qubits.<n>Each dual-rail qubit, encoded in pairs of tunable transmons, preserves millisecond-scale coherence times and single-qubit gate errors.<n>This work provides a blueprint ford quantum error correction with erasure qubits.
• Score: 14.808613294313902
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Recent advances in quantum error correction (QEC) across hardware platforms have demonstrated operation near and beyond the fault-tolerance threshold, yet achieving exponential suppression of logical errors through code scaling remains a critical challenge. Erasure qubits, which enable hardware-level detection of dominant error types, offer a promising path toward resource-efficient QEC by exploiting error bias. Single erasure qubits with dual-rail encoding in superconducting cavities and transmons have demonstrated high coherence and low single-qubit gate errors with mid-circuit erasure detection, but the generation of multi-qubit entanglement--a fundamental requirement for quantum computation and error correction--has remained an outstanding milestone. Here, we demonstrate a superconducting processor integrating four dual-rail erasure qubits that achieves the logical multi-qubit entanglement with error-biased protection. Each dual-rail qubit, encoded in pairs of tunable transmons, preserves millisecond-scale coherence times and single-qubit gate errors at the level of $10^{-5}$. By engineering tunable couplings between logical qubits, we generate high-fidelity entangled states resilient to physical qubit noise, including logical Bell states (98.8% fidelity) and a three-logical-qubit Greenberger-Horne-Zeilinger (GHZ) state (93.5% fidelity). A universal gate set is realized through a calibrated logical controlled-NOT (CNOT) gate with 96.2% process fidelity, enabled by coupler-activated $XX$ interactions in the protected logical subspace. This work advances dual-rail architectures beyond single-qubit demonstrations, providing a blueprint for concatenated quantum error correction with erasure qubits.

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