Recent years have seen a simultaneous growth in the scientific and technological applications of cryogenic devices. This project proposes an innovative approach for the development of superconducting quantum processors and cryogenic particle detectors for rare event searches. Despite these two topics have different fields of application, their implementation is based on some common technological solutions, such as the use of cryogenics, the need for low radioactivity and the adoption of superconductor devices for signal readout.

The interest in quantum technology has recently seen an impressive growth, thanks to its potential impact on the economy and society. Large mass calorimeters have shown unprecedented performances and are a leading technology for rare event searches and many other potential applications in particle physics and cosmology.

This project has the potential to introduce a paradigm shift in the development of cryogenic devices. We will enhance the performance of superconducting quantum bits by suppressing the decoherence and correlated errors induced by radioactivity. We will define a novel approach to the design of cryogenic calorimeters, featuring at the same time better performance and simplified hardware implementation. These ambitious goals will be accomplished by addressing the state of the art technologies from different perspectives. We will upgrade the design of cryogenic detectors and qubit chips with the use of thin films. In quantum circuits, the thin films can act as phonon traps, protecting the qubits and then enhancing their coherence. The use of coatings in cryogenic calorimeters can improve their particle discrimination capability and can simplify the construction procedures.

In parallel, we will develop protocols for radioactivity screening and mitigation. The detrimental effects of radioactivity on qubits were demonstrated only recently, however a full understanding of this phenomenon, and a corresponding optimization of quantum devices is still missing. On the contrary, the effects of radioactivity on cryogenic calorimeters have been known for a long time, however the extremely low backgrounds required in rare event searches demand for careful material screening. Finally we will implement a simulation framework for modeling the thermal behavior of cryogenic devices. Following an iterative approach, this tool will take as input the data from cryogenic measurements, and will help optimizing the design of the devices developed in the research project. The proposed project has an intrinsic interdisciplinary nature, comprising quantum processors, particle detectors, radioactivity mitigation, thin films and thermal models. It is based on the collaboration of young researchers with different backgrounds and experience in each of the aforementioned activities.