Beyond-Ten-Hour Coherence in a Decoherence-Free Trapped-Ion Clock Qubit

Jiahao Pi; Xiangjia Liu; Junle Cao; Pengfei Wang; Lingfeng Ou; Erfu Gao; Hengchao Tu; Menglin Zou; Xiang Zhang; Junhua Zhang; Kihwan Kim

arXiv · 2603.19631

Beyond-Ten-Hour Coherence in a Decoherence-Free Trapped-Ion Clock Qubit

Jiahao Pi·Xiangjia Liu·Junle Cao·Pengfei Wang·Lingfeng Ou·Erfu Gao·Hengchao Tu·Menglin Zou·Xiang Zhang·Junhua Zhang·Kihwan Kim

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Abstract

Quantum systems promise to revolutionize information processing science and technology [1-3]. The preservation of quantum coherence, the defining property of qubits, fundamentally constrains the performance of quantum information processing with quantum memories [4]. While trapped atomic ions theoretically support million-year coherence based on spontaneous emission [5-7], experimental demonstrations have reached far less, only about an hour [8-13]. Here we combine clock-state qubits with decoherence-free subspace (DFS) encoding to achieve coherence exceeding ten hours. Using correlation-based phase tracking in 171Yb+ ion pairs sympathetically cooled by 138Ba+ ion, we demonstrate this without magnetic shielding or enhanced microwave phase stabilization that previously limited coherence times. DFS encoding references the qubit phase to the inter-ion energy difference to reject microwave phase noise and common-mode magnetic fluctuations, while clock states provide environmental insensitivity. Throughout measurements extended to 1600 seconds, we observe minimal coherence decay, with exponential fits yielding a coherence time of (3.77 +/- 1.09) x 10^4 seconds. Our results establish DFS encoding as a form of passive error correction that eliminates technical noise constraints, unlocking the million-year coherence potential of atomic ions for scalable quantum information processing.

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Jiahao Pi, Xiangjia Liu, Junle Cao, Pengfei Wang, Lingfeng Ou, Erfu Gao, Hengchao Tu, Menglin Zou, Xiang Zhang, Junhua Zhang, Kihwan Kim. 2026-03-20. Beyond-Ten-Hour Coherence in a Decoherence-Free Trapped-Ion Clock Qubit. https://arxiv.org/abs/2603.19631

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