Exceptional points are degeneracies in physical systems at which both the underlying eigenvalues and eigenvectors of the system coalesce. They originated in theoretical explorations of quantum mechanics, but are of increasing value in photonics, acoustics and electronics because their emergence in physical systems with controlled gain and loss can dramatically alter the response of a system. In particular, systems biased at exceptional points can exhibit an amplified response to a small perturbation, enabling greatly enhanced sensitivity for certain resonant sensors. In biomedicine, implanted electronic sensors based on resonant inductor–capacitor (LC) circuits can be used to monitor internal physiological states, but their capabilities are currently limited by the low sensitivity of existing wireless interrogation techniques. Here we show that a reconfigurable wireless system locked to an exceptional point can be used to interrogate in vivo microsensors with a sensitivity 3.2 times the limit encountered by existing schemes. We use a controller that maximizes the abruptness of a parity–time-symmetry phase transition to operate a reconfigurable circuit at an exceptional point and maintain enhanced sensitivity. With this approach, we demonstrate robust readout of LC microsensors (with diameters of 900 μm) that are subcutaneously implanted in a rat, and show that it can be used for wideband sensor interrogation for measurement of the resonant frequencies of single and multiple sensors.

例外点是物理系统中的简并性，系统的基础特征值和特征向量在该简并性处合并。它们起源于量子力学的理论探索，但是在光子学，声学和电子学中具有越来越高的价值，因为它们出现在具有受控增益和损耗的物理系统中会极大地改变系统的响应。尤其是，偏向异常点的系统会表现出对小扰动的放大响应，从而使某些谐振传感器的灵敏度大大提高。在生物医学中，可以使用基于谐振电感器-电容器（LC）电路的植入式电子传感器来监视内部生理状态，但是它们的功能目前受到现有无线询问技术灵敏度低的限制。在这里，我们展示了锁定到特殊点的可重配置无线系统可用于审讯体内微传感器，其灵敏度是现有方案所遇到的极限的3.2倍。我们使用的控制器可以最大程度地提高奇偶性-时间对称性相变的突变性，以便在特殊情况下操作可重配置的电路并保持增强的灵敏度。通过这种方法，我们展示了皮下植入大鼠皮下的LC微传感器（直径为900μm）的可靠读数，并表明该微传感器可用于宽带传感器询问，以测量单个和多个传感器的共振频率。我们使用的控制器可以最大程度地提高奇偶性-时间对称性相变的突变性，以便在特殊情况下操作可重配置的电路并保持增强的灵敏度。通过这种方法，我们展示了皮下植入大鼠中的LC微传感器（直径为900μm）的稳健读数，并表明该微传感器可用于宽带传感器询问，以测量单个和多个传感器的共振频率。我们使用的控制器可以最大程度地提高奇偶性-时间对称性相变的突变性，以便在特殊情况下操作可重配置的电路并保持增强的灵敏度。通过这种方法，我们展示了皮下植入大鼠皮下的LC微传感器（直径为900μm）的可靠读数，并表明该微传感器可用于宽带传感器询问，以测量单个和多个传感器的共振频率。