Distinguished Seminar Series Sponsored by the Texas Quantum Institute (TQI) with Tian Zhong from the University of Chicago

The ability to engineer individual quantum systems—atoms, spins, and photons—has transformed quantum science and
enabled rapidly advancing technologies in computing, communication, and sensing. A central challenge for the next stage of
quantum engineering is to move beyond isolated quantum components and create increasingly complex systems in which
distinct quantum degrees of freedom communicate, interact, and collectively generate new functionality.
In this talk, I will describe our efforts to engineer quantum systems across increasing physical scales, beginning with the
material itself. Rather than adapting existing materials to quantum technologies, we pursue a bottom-up approach in which
quantum materials are engineered to provide the coherence, optical functionality, and interfaces required by quantum
devices. Using molecular-beam epitaxy, we have developed rare-earth quantum materials in which telecom-wavelength
erbium spin-photon interfaces combine long optical and spin coherence with compatibility with nanophotonic and
superconducting circuits. These results establish a materials foundation for scalable, optically connected quantum systems.
Building outward from these quantum building blocks, we are developing interfaces that allow fundamentally different
quantum systems to communicate. By exploiting an intrinsic spectral matching between rubidium and erbium, we recently
demonstrated a direct telecom quantum link between atomic and solid-state nodes without quantum frequency conversion.
The network was deployed over 10.6 km of metropolitan fiber in Chicago and extended to 49.2 km in the laboratory while
preserving nonclassical photon correlations. This approach points toward hybrid quantum networks in which different
quantum technologies retain their individual strengths while communicating through native optical interfaces.
Finally, I will briefly discuss how the same philosophy of co-engineering materials and their electromagnetic environment
may open a different frontier. Moving beyond using light to connect quantum systems, we are exploring whether engineered
quantum light can itself become an active ingredient in quantum matter. By integrating quantum materials with nonlinear
photonic resonators and cavity fields, we seek new regimes in which light-matter interactions can be used to probe and
ultimately engineer collective quantum phenomena.