Terahertz Radiation Interacting with Electrons in Semiconductors: Pathways to Emerging Quantum Technologies

Electronics: A Successful History of Electrons Dancing with Electromagnetic Fields Electronics has long been a testament to the fascinating interplay of electrons and electromagnetic fields. From the invention of the first vacuum tube to the most advanced THz oscillators, these two entities have been studied as independent yet interacting quantities. However, it is now well established that a new kind of interaction emerges when electrons ("matter") and electromagnetic fields ("light") share the same space over time. This phenomenon underpins cavity quantum electrodynamics , which occurs when electrons are confined within a "matter" cavity (or a quantum well) and THz radiation is confined within an "optical" cavity (or a resonant THz cavity). In cavity quantum electrodynamics, commonly referred to in the optical community as the strong light-matter coupling regime, light and matter can no longer be treated as independent entities. Instead, they combine to form a unified physical entity known as a polariton. In recent years, cavity quantum electrodynamics has garnered significant attention and is already being implemented in various platforms. For instance, Google is advancing quantum computing using superconductors driven by GHz signals. The primary goal of this project is to investigate polariton effects in semiconductor electron devicesspecifically, quantum well heterostructuresat THz frequencies and room temperature. While theoretical and experimental results regarding polaritons in these platforms exist, much remains to be explored to bring these findings to practical, commercial electronics. Although the quantum optics community has developed a robust understanding of the phenomenology of cavity quantum electrodynamics, and some experimental prototypes of operating at room temperature have been documented, the **electronics community has largely overlooked this phenomenon**. To the best of our knowledge, this proposal is among the first to study CQED from a purely electron-device perspective. We argue that this emerging phenomenon holds the potential to revolutionize electronics by naturally bridging electronics and photonics. Furthermore, it offers a new platform compatible with traditional electronics fabrication techniques for advancing quantum technologies. Our project is structured around three specific objectives: 1. **Modelling matter cavities** to model polaritonic semiconductor devices, with a focus on the quantum transport of electrons coupled to light in heterostructures. 2. **Design optical cavities** at THz frequencies for polaritonic semiconductor devices. This includes addressing practical aspects of THz radiation (with or without polaritonic phenomena), such as wireless energy transfer and optomechanical responses.