Ying Zu-Jian, Felicetti Simone, Liu Gang, Braak Daniel
School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China.
Institute for Complex Systems, National Research Council (ISC-CNR), 00185 Rome, Italy.
Entropy (Basel). 2022 Jul 22;24(8):1015. doi: 10.3390/e24081015.
The quantum Rabi model (QRM) with linear coupling between light mode and qubit exhibits the analog of a second-order phase transition for vanishing mode frequency which allows for criticality-enhanced quantum metrology in a few-body system. We show that the QRM including a nonlinear coupling term exhibits much higher measurement precisions due to its first-order-like phase transition at frequency, avoiding the detrimental slowing-down effect close to the critical point of the linear QRM. When a bias term is added to the Hamiltonian, the system can be used as a fluxmeter or magnetometer if implemented in circuit QED platforms.
光模式与量子比特之间具有线性耦合的量子拉比模型（QRM），对于消失的模式频率呈现出二阶相变的类似情况，这使得在少体系统中实现临界增强量子计量成为可能。我们表明，包含非线性耦合项的QRM由于其在特定频率处的类一阶相变，展现出更高的测量精度，避免了接近线性QRM临界点时有害的减速效应。当在哈密顿量中添加一个偏置项时，如果在电路量子电动力学平台中实现，该系统可被用作磁通计或磁力计。
