Parto Midya, Leefmans Christian, Williams James, Gray Robert M, Marandi Alireza
Department of Electrical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
Physics and Informatics Laboratories, NTT Research, Inc., Sunnyvale, CA, 94085, USA.
Light Sci Appl. 2025 Jan 1;14(1):6. doi: 10.1038/s41377-024-01667-z.
Sensors are indispensable tools of modern life that are ubiquitously used in diverse settings ranging from smartphones and autonomous vehicles to the healthcare industry and space technology. By interfacing multiple sensors that collectively interact with the signal to be measured, one can go beyond the signal-to-noise ratios (SNR) attainable by the individual constituting elements. Such techniques have also been implemented in the quantum regime, where a linear increase in the SNR has been achieved via using entangled states. Along similar lines, coupled non-Hermitian systems have provided yet additional degrees of freedom to obtain better sensors via higher-order exceptional points. Quite recently, a new class of non-Hermitian systems, known as non-Hermitian topological sensors (NTOS) has been theoretically proposed. Remarkably, the synergistic interplay between non-Hermiticity and topology is expected to bestow such sensors with an enhanced sensitivity that grows exponentially with the size of the sensor network. Here, we experimentally demonstrate NTOS using a network of photonic time-multiplexed resonators in the synthetic dimension represented by optical pulses. By judiciously programming the delay lines in such a network, we realize the archetypal Hatano-Nelson model for our non-Hermitian topological sensing scheme. Our experimentally measured sensitivities for different lattice sizes confirm the characteristic exponential enhancement of NTOS. We show that this peculiar response arises due to the combined synergy between non-Hermiticity and topology, something that is absent in Hermitian topological lattices. Our demonstration of NTOS paves the way for realizing sensors with unprecedented sensitivities.
传感器是现代生活中不可或缺的工具，广泛应用于从智能手机、自动驾驶汽车到医疗行业和太空技术等各种不同场景。通过连接多个共同与被测信号相互作用的传感器，可以超越单个组成元件所能达到的信噪比（SNR）。这种技术也已在量子领域得到应用，在该领域中，通过使用纠缠态实现了信噪比的线性增加。类似地，耦合非厄米系统提供了额外的自由度，可通过高阶例外点获得更好的传感器。最近，理论上提出了一类新的非厄米系统，即非厄米拓扑传感器（NTOS）。值得注意的是，非厄米性与拓扑之间的协同相互作用有望赋予此类传感器更高的灵敏度，该灵敏度会随着传感器网络的规模呈指数增长。在此，我们利用由光脉冲表示的合成维度中的光子时间复用谐振器网络，通过实验证明了NTOS。通过巧妙地对这样一个网络中的延迟线进行编程，我们为非厄米拓扑传感方案实现了典型的Hatano-Nelson模型。我们对不同晶格尺寸的实验测量灵敏度证实了NTOS特有的指数增强特性。我们表明，这种特殊响应源于非厄米性与拓扑之间的协同作用，而这在厄米拓扑晶格中并不存在。我们对NTOS的演示为实现具有前所未有的灵敏度的传感器铺平了道路。
