“Engineering Quantum Systems: From Materials to Networks”
Tian Zhong | Chicago Quantum Institute, University of Chicago
The ability to control atoms, spins, photons, and superconducting circuits has created powerful building blocks for quantum information science. The next challenge is to connect these components across physical platforms and length scales while preserving the quantum properties that make them useful. In this talk, I will describe our approach to this problem, beginning with engineered quantum materials, progressing to heterogeneous telecom networks, and ending with the collective behavior of entanglement at network scale.
Our work starts from a materials-first premise: the quantum coherence and optical interfaces required by a quantum system should be designed into the material itself. Using molecular-beam epitaxy, we develop bottom-up rare-earth quantum materials in which erbium provides a direct optical interface in the telecommunications band. These Er spin-photon interfaces combine long optical and spin coherence with compatibility with nanophotonic and superconducting circuits. They offer a path from atomically controlled materials to devices that can generate, store, and process quantum states while connecting efficiently to optical fiber.
Building on these components, we are developing quantum interconnects between systems that normally operate with different physical degrees of freedom. By exploiting an intrinsic spectral correspondence between rubidium and erbium atoms, we demonstrated a direct telecom quantum link between atomic and solid-state nodes without quantum frequency conversion. The link was deployed over 10.6 km of metropolitan fiber in Chicago and extended to ~50 km in the laboratory while preserving nonclassical photon correlations. This result shows how atomic and material design can simplify a hybrid network architecture and allow distinct quantum nodes to communicate through existing fiber infrastructure.
As networks grow, their behavior cannot be understood solely from the performance of an individual node or link. Imperfect entanglement must be distributed, stored, and purified under realistic constraints, and local operations can shape the behavior of the network as a whole. I will discuss our efforts to identify the physical principles that govern entanglement dynamics and purification in extended networks, including how resource limitations and network structure affect the emergence of useful long-range correlations. Connecting these questions to experimentally grounded materials and interfaces provides a route toward quantum networks whose capabilities arise from coordinated behavior across many heterogeneous components.
SHORT BIO:
Tian Zhong is an Assistant Professor in the Pritzker School of Molecular Engineering at the University of Chicago. He received his Ph.D. and M.S. in Electrical Engineering and Computer Science from MIT and was a postdoctoral researcher and IQIM Fellow at Caltech before joining the University of Chicago in 2018. His research develops quantum materials, devices, and systems for quantum information science, with an emphasis on rare-earth spin-photon interfaces, integrated quantum photonics, and quantum networks. His honors include the NSF CAREER Award, the U.S. Army Research Office Young Investigator Award, the Argonne Board of Governors' Award, and the Michael D. Sturge Prize 2025 for his seminal contributions to quantum nanophotonics as an early career scientist.
