Thermal Photoemitter and Absorber

Sammanfattning

The development of controllable thermal photon sources is essential for the advancement of quantum computers, specifically for the development of sensitive detectors and the study of heat transport in superconducting circuits. This thesis investigates a device featuring a metallic copper island acting as a variable thermal bath, coupled to a superconducting microwave line through a clean interface. The device utilizes four adjoining Normal-Insulator-Superconductor (NIS) junctions, enabling both the heating of the island and precise measurements of its electronic temperature. Experimental results demonstrate microwave signal absorption efficiency near 100% and thermal emission reaching close to the theoretical unity limit, thus giving a direct measurement of quantum limited photonic heat conduction. In addition to the emission measurements, this thesis considers the heat flow away from the island. Interestingly, measurements reveal an enhanced heat flux from the island compared to similar previously studied devices, suggesting that specific geometrical parameters may play a critical role in the heat conduction. These findings establish the device as a highly efficient, controllable thermal photon source.