Exceptional points are singularities of open systems, and among their many remarkable properties, they provide a way to enhance the responsivity of sensors. Here we show that the improved responsivity of a laser gyroscope caused by operation near an exceptional point is precisely compensated by increasing laser noise. The noise, of fundamental origin, is enhanced because the laser mode spectrum loses the oft-assumed property of orthogonality. This occurs as system eigenvectors coalesce near the exceptional point and a bi-orthogonal analysis confirms experimental observations. While the results do not preclude other possible advantages of the exceptional-point-enhanced responsivity, they do show that the fundamental sensitivity limit of the gyroscope is not improved through this form of operation. Besides being important to the physics of microcavities and non-Hermitian photonics, these results help clarify fundamental sensitivity limits in a specific class of exceptional-point sensor.

特殊点是开放系统的奇异点，在它们的许多显着特性中，它们提供了一种增强传感器响应度的方法。在这里，我们表明，由于在异常点附近工作而引起的激光陀螺仪响应速度的提高，可以通过增加激光噪声来精确补偿。由于激光模式光谱失去了通常假定的正交性，因此增强了基本噪声。当系统特征向量在例外点附近合并时，就会发生这种情况，双正交分析证实了实验观察结果。虽然结果并未排除异常点增强响应度的其他可能优势，但它们确实表明，通过这种操作方式，陀螺仪的基本灵敏度极限并未得到改善。