Harvard's ultra-thin chip breakthrough sets new standard for quantum optics

Researchers at Harvard University, led by Professor Federico Capasso, have developed a groundbreaking ultra-thin optical device called a metasurface that can perform complex quantum operations previously requiring numerous bulky components. This single, flat chip replaces traditional setups involving lenses, mirrors, and beam splitters used to control and entangle photons—key particles for quantum computing and networking. By miniaturizing the entire optical system into a stable, robust metasurface, the team addresses a major scalability challenge in photon-based quantum information processing. A novel design process was crucial to this breakthrough, employing graph theory to map the complex interference pathways of multi-photon quantum states onto nanoscale patterns on the metasurface. This approach unifies the metasurface design with the quantum state generation, enabling precise and systematic construction of devices tailored for specific quantum tasks. The metasurface’s monolithic design reduces optical loss and environmental sensitivity, and its fabrication via semiconductor industry techniques promises cost-effective, reproducible production. Beyond quantum computing, this technology has potential applications in