Development of the Quantum Science Center Underground Test Stand (QUIET)

The Quantum Science Center (QSC) is one of several research centers established as part of the National Quantum Initiative Act. A primary goal of QSC is to overcome key roadblocks in quantum state resilience, controllability and scalability of quantum technologies. In particular, the Fermilab effort is focused on the problem of understanding the deleterious effects of ionizing radiation on qubits, quantum sensors and quantum materials. These same sources of ionizing radiation are also known to be a background for dark matter detectors. Hence improved understanding in the role of ionizing radiation on the performance of quantum sensors and qubits will also benefit the development of next generation dark matter detectors. Studying this problem requires the construction of a test stand that is well-shielded from sources of ionizing radiation and noise. We will construct this test stand, QUIET, in the MINOS near detector hall at Fermilab. This underground location provides shielding from cosmic rays in the form of 300 m.w.e. overburden. QUIET will be modeled after an existing dark matter test stand, named NEXUS, which is located in the same underground hall. NEXUS, the Northwestern Experimental Underground Site at Fermilab, is a detector prototyping and calibration facility that enables accurate calibration of full-size SuperCDMS detectors in a low background environment and prototyping and testing of future detectors. It was jointly designed and built by Fermilab and the same Northwestern University group that this SOW is meant to support. Based on their long-time experience with SuperCDMS and their role in developing the NEXUS stand, the Northwestern group is uniquely suited for the development of QUIET in collaboration with Fermilab. Once QUIET is installed and commissioned, we will operate qubits and related quantum sensors and compare their performance against the same devices operated in surface facilities. To aid our understanding of the effects of running in the well-shielded environment that is provided by QUIET, we will perform simulations of the backgrounds to improve our understanding of the mechanisms by which they cause qubit decoherence. To the extent that these studies also inform our understand of dark matter detector backgrounds, we will apply the knowledge we gain from these background studies to the development of next generation sensors for low mass dark matter searches.