Cavity Cooling Using Electron Pulses

The interaction between free electrons and electromagnetic fields is a cornerstone of classical and quantum electrodynamics. Recent studies have demonstrated that free-electron interactions can be utilized to create, manipulate, and measure quantum photonic states [1], leveraging the electron-photon entanglement enabled by their interaction. The frontier of research now takes these concepts into new spectral domains, and specifically to generating quantum photonic states in the THz and microwave ranges. This effort leverages the electrons' rapid (picosecond) interaction duration and complete tunability. However, a long-standing challenge in these spectral domains is the thermal noise at finite temperatures. Thus, achieving strong electron-photon entanglement, essential for all photonic quantum processes, requires cooling the photonic state to near-zero temperatures [2].