Nontechnical Abstract The goal of this project is to create a new class of matter by freezing a heterogeneous mixture of rare gases: helium (He), neon (Ne), and argon (Ar), into multilayer solids at low temperatures. The new kind of matter, called heterogeneous rare-gas quantum solids, is analogous to heterogeneous semiconductors but can exhibit more unusual electronic properties on the surface, at the interface, or in the bulk. These quantum solids, defined by the fact that the atomic positions are strongly vibrating even at the lowest temperatures, are exceptionally inert and pristine. Their surfaces and interfaces therefore provide an ideal platform for studying the quantum properties of electrons confined to moving in two dimensions, including tendencies to form exotic phases of matter. In addition, these quantum solids can serve as ultraclean host materials for quantum bits – the fundamental building blocks of quantum computers. The project will provide comprehensive training to undergraduate and graduate students across interdisciplinary fields and prepare the next generation of quantum scientists and engineers. Technical Abstract We will create and characterize a new class of condensed matter – heterogeneous rare-gas quantum solids, which consist of multilayer thin films of solid neon (Ne), solid argon (Ar), and (optionally) a mono-atomic layer of solid helium (He) at near-zero temperature and pressure. We target revealing unique electronic structures on the s