通过隐藏对称性保护的真空噪声固定点实现超越例外点的量子传感
Quantum Sensing Beyond Exceptional Points via Hidden symmetry-protected vacuum-noise fixed point
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中文总结 AI 辅助
研究提出基于对称性保护噪声抑制而非响应放大的非厄米量子传感途径，开发统一PT和APT对称性的模型，发现隐藏对称性保护相变及真空噪声固定点，增强量子传感，建立不同于传统EP方法的机制，揭示相关联系并确立噪声抑制范式。
中文摘要 AI 辅助
例外点（EP）传感因其异常响应缩放而备受关注。然而，近期研究表明，EP附近增强的响应不可避免地伴随着量子噪声放大，从根本上限制了可实现的信噪比（SNR）。在此，我们提出一种基于对称性保护噪声抑制而非响应放大的非厄米量子传感的根本不同途径。我们开发了一个完全量子连续变量模型，将宇称 - 时间（PT）和反宇称 - 时间（APT）对称性统一在一个框架内。利用这两种对称性之间的不相容性，我们发现了一个非厄米狄拉克本征谱，并揭示了嵌入在哈密顿谱中的隐藏对称性保护相变。值得注意的是，这个隐藏相变同时构成一个对称性保护的真空噪声固定点，其中集体三模正交分量尽管没有任何异常谱响应，但量子涨落受到抑制。结果，通过抑制过量量子噪声同时保持有限的响应灵敏度来增强量子传感，建立了一种与传统基于EP的方法根本不同的传感机制。这些结果揭示了隐藏对称性、量子涨落和非厄米量子计量学之间意想不到的联系，并将噪声抑制确立为非厄米量子传感的替代范式。
英文摘要
Exceptional-point (EP) sensing has attracted considerable interest because of its anomalous response scaling. However, recent studies have shown that the enhanced response near an EP is inevitably accompanied by amplified quantum noise, fundamentally limiting the achievable signalto-noise ratio (SNR). Here, we propose a fundamentally different route toward non-Hermitian quantum sensing based on symmetry-protected noise suppression rather than response amplification. We develop a fully quantum continuous-variable model that unifies parity-time (PT) and anti-paritytime(APT) symmetries within a single framework. Exploiting the incompatibility between these two symmetries, we uncover a non-Hermitian Dirac eigenspectrum and reveal a hidden symmetryprotected phase transition embedded in the Hamiltonian spectrum. Remarkably, this hidden phasetransition simultaneously constitutes a symmetry-protected vacuum-noise fixed point, where collective three-mode quadratures exhibit suppressed quantum fluctuations despite the absence of any anomalous spectral response. As a consequence, quantum sensing is enhanced through the suppression of excess quantum noise while maintaining a finite response sensitivity, establishing a sensing mechanism fundamentally different from conventional EP-based approaches. These results reveal an unexpected connection between hidden symmetry, quantum fluctuations, and non-Hermitian quantum metrology, and establish noise suppression as an alternative paradigm for non-Hermitian quantum sensing.
