Investigation of microwave transducers for linearity dependence and applications in quantum networking

Quantum devices have the potential to revolutionize applications in computing, communications, and sensing; however, current state-of-art resources must operate at extremely low temperatures, making the routing of microwave control and readout signals challenging to scale. Interest in microwave photonic solutions to this problem has grown in recent years, in which control signals are delivered to the cold stage via optical fiber, where they are converted to electrical signals through photodetection. Overall link performance depends strongly on the characteristics of the photodiode, yet detailed measurements of many detector properties remain lacking at cold temperatures. In this work, we examine and compare the performance of a modified uni-traveling carrier photodiode (MUTC-PD) at both room (300 K) and liquid nitrogen (80 K) temperatures, focusing in particular on responsivity, bandwidth, and linearity. In line with previous work, we find a sharp reduction in responsivity at 1550 nm as temperature decreases, while RF bandwidth remains steady. Interestingly, our linearity tests reveal that the RF output saturates more quickly at 80 K, suggesting reduced linearity with lower temperature, the cause of which is still under investigation. Our results should help contribute to the understanding and future design of highly linear cryogenic quantum links.

量子器件有可能彻底改变计算、通信和传感方面的应用；然而，当前最先进的资源必须在极低的温度下运行，这使得微波控制和读出信号的布线难以规模化。近年来，人们对解决这一问题的微波光子解决方案的兴趣日益增长，在这种方案中，控制信号通过光纤传输到低温台，在那里通过光电探测转换为电信号。整个链路性能在很大程度上取决于光电二极管的特性，但在低温下许多探测器特性的详细测量仍然缺乏。在这项工作中，我们检测并比较了一种改进的单行载流子光电二极管（MUTC - PD）在室温（300 K）和液氮（80 K）温度下的性能，特别关注响应度、带宽和线性度。与之前的研究一致，我们发现随着温度降低，在1550 nm处响应度急剧下降，而射频带宽保持稳定。有趣的是，我们的线性度测试表明，在80 K时射频输出更快地达到饱和，这表明温度越低线性度越低，其原因仍在研究中。我们的研究结果应有助于理解高线性低温量子链路，并为其未来设计提供帮助。