Physical systems close to a quantum phase transition exhibit a divergent susceptibility, suggesting that an arbitrarily high precision may be achieved by exploiting quantum critical systems as probes to estimate a physical parameter. However, such an improvement in sensitivity is counterbalanced by the closing of the energy gap, which implies a critical slowing down and an inevitable growth of the protocol duration. Here, we design different metrological protocols that exploit the superradiant phase transition of the quantum Rabi model, a finite-component system composed of a single two-level atom interacting with a single bosonic mode. We show that, in spite of the critical slowing down, critical quantum optical probes can achieve a quantum-enhanced time scaling of the sensitivity in frequency-estimation protocols.

中文翻译：

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具有有限分量量子相变的临界量子计量学

接近量子相变的物理系统表现出不同的磁化率，这表明可以通过利用量子临界系统作为探针来估计物理参数来实现任意高精度。但是，通过缩短能隙可以抵消这种敏感性的提高，这意味着严重的速度下降和协议持续时间的必然增长。在这里，我们设计了不同的计量协议，这些协议利用了量子拉比模型的超辐射相变，量子拉比模型是一个由单个两级原子与单个玻色子模式相互作用组成的有限分量系统。我们表明，尽管临界速度变慢，但临界量子光学探针仍可以实现频率估计协议中灵敏度的量子增强时间缩放。