Autonomous quantum error correction beyond break-even and its metrological application

• URL: http://arxiv.org/abs/2509.26042v1
• Date: Tue, 30 Sep 2025 10:16:57 GMT
• Title: Autonomous quantum error correction beyond break-even and its metrological application
• Authors: Zhongchu Ni, Ling Hu, Yanyan Cai, Libo Zhang, Jiasheng Mai, Xiaowei Deng, Pan Zheng, Song Liu, Shi-Biao Zheng, Yuan Xu, Dapeng Yu,
• Abstract summary: We present an unambiguous demonstration of beyond-break-even AQEC in a circuit quantum electrodynamics system.<n>Under the AQEC protection, the logical qubit achieves a lifetime surpassing that of the best physical qubit available in the system by 18%.<n>These results illustrate that the demonstrated AQEC procedure not only represents a crucial step towards fault-tolerant quantum computation but also offers advantages for building robust quantum sensors.
• Score: 17.911199662649967
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: The ability to extend the lifetime of a logical qubit beyond that of the best physical qubit available within the same system, i.e., the break-even point, is a prerequisite for building practical quantum computers. So far, this point has been exceeded through active quantum error correction (QEC) protocols, where a logical error is corrected by measuring its syndrome and then performing an adaptive correcting operation. Autonomous QEC (AQEC), without the need for such resource-consuming measurement-feedback control, has been demonstrated in several experiments, but none of which has unambiguously reached the break-even point. Here, we present an unambiguous demonstration of beyond-break-even AQEC in a circuit quantum electrodynamics system, where a photonic logical qubit encoded in a superconducting microwave cavity is protected against photon loss through autonomous error correction, enabled by engineered dissipation. Under the AQEC protection, the logical qubit achieves a lifetime surpassing that of the best physical qubit available in the system by 18\%. We further employ this AQEC protocol to enhance the precision for measuring a slight frequency shift, achieving a metrological gain of 6.3 dB over that using the most robust Fock-state superposition. These results illustrate that the demonstrated AQEC procedure not only represents a crucial step towards fault-tolerant quantum computation but also offers advantages for building robust quantum sensors.

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