Ultrasensitive bolometers as detectors of single quanta

The development of precision detectors has been pivotal in advancing the field of physics, where accurate observation and measurement of natural phenomena are essential for understanding the laws of the universe. In this thesis, we consider superconducting quantum circuits (SQCs) to expand the toolbox of ultrasensitive detection methods. This thesis begins by investigating the hypothesis of an electric field effect on metallic superconductors which on one hand, contradicts current theories, but on the other hand, might open possibilities for novel applications in electric field detection within SQCs. We delve into the feasibility of electric-field detectors through resonator studies, aiming to shed light on the interaction between superconductors and external fields. We then dive into the world of bolometers, traditionally known for their effectiveness in photon detection. We consider their underutilized potential in the detection of electrons and their integration into more complex systems. Through qubit readout experiments and the exploration of single-electron detection, we stretch the boundaries of bolometer applications, aiming to widen their range of functionalities. Furthermore, we present an improved bolometer design that streamlines fabrication processes and optimizes device characteristics. This novel design paves the way for enhanced bolometric detection techniques within superconducting quantum circuits, increasing their accessibility and effectiveness in practical applications. This thesis paints a comprehensive picture of the versatile world of ultrasensitive metallic bolometers within SQCs. It offers novel insights, methodologies, and the promise of greater advances in precision detection, contributing to the broader advancement of superconducting quantum technology.