Superconducting resonant cavities design and material development for quantum computing and quantum sensing applications

Superconducting resonant cavities are electromagnetic devices that leverage the unique properties of superconducting materials to sustain high-quality oscillations of the electromagnetic field with minimal energy loss, resulting in long coherence times for the trapped electromagnetic waves. One of the most important applications for this kind of device is particle accelerators in which superconducting radiofrequency (SRF) cavities play a pivotal role by providing a stable and efficient way to accelerate charged particles, allowing scientists to achieve high beam energies and intensities for fundamental research, materials science, and medical applications. A more recent field of application is quantum computing: superconducting qubits, the building blocks of the most powerful existing quantum computers, require exceptionally stable and low-loss environments to perform complex quantum computations. Superconducting resonant cavities provide the necessary conditions to control and manipulate these qubits paving the way for more powerful quantum processors. New applications of great interest for the scientific community are also quantum communication and quantum sensing. The ability of SRF cavities to preserve quantum states over extended periods of time enhances the reliability and efficiency of quantum communication protocols and enables precise measurements in quantum sensing applications such as single photon counting. In this work, the design and fabrication of an aluminum SRF cavity for quantum computing applications is discussed, along with its characterization and performances. Moreover, a similar design for the fabrication of a second cavity for quantum sensing applied to dark matter search, in particular axion-like particles (ALPs) search, is presented. In the same field of application, looking at thin film technology for ALPs search NbTi coated cavities performances are investigated.