Penn Engineers Design Nanostructured Diamond Metalens For Compact Quantum Technologies

By finding a certain kind of defect inside a block of diamond and fashioning a pattern of nanoscale pillars on the surface above it, the researchers can control the shape of individual photons emitted by the defect. Because those photons carry information about the spin state of an electron, such a system could be used as the basis for compact quantum technologies. (Illustration: Ann Sizemore Blevins)

By Lauren Salig

At the chemical level, diamonds are no more than carbon atoms aligned in a precise, three-dimensional (3D) crystal lattice. However, even a seemingly flawless diamond contains defects: spots in that lattice where a carbon atom is missing or has been replaced by something else. Some of these defects are highly desirable; they trap individual electrons that can absorb or emit light, causing the various colors found in diamond gemstones and, more importantly, creating a platform for diverse quantum technologies for advanced computing, secure communication and precision sensing.

Quantum technologies are based on units of quantum information known as “qubits.” The spin of electrons are prime candidates to serve as qubits; unlike binary computing systems where data takes the form of only 0s or 1s, electron spin can represent information as 0, 1, or both simultaneously in a quantum superposition. Qubits from diamonds are of particular interest to quantum scientists because their quantum-mechanical properties, including superposition, exist at room temperature, unlike many other potential quantum resources.

The practical challenge of collecting information from a single atom deep inside a crystal is a daunting one, however. Penn Engineers addressed this problem in a recent study in which they devised a way to pattern the surface of a diamond that makes it easier to collect light from the defects inside. Called a metalens, this surface structure contains nanoscale features that bend and focus the light emitted by the defects, despite being effectively flat.

Tzu-Yung Huang, Lee Bassett and David Hopper at work in Bassett’s Quantum Engineering Laboratory.

The research was led by Lee Bassett, Assistant Professor in the Department of Electrical and Systems Engineering, graduate student Tzu-Yung Huang, and postdoctoral researcher Richard Grote from Bassett’s lab.

Additional Bassett Lab members David Hopper, Annemarie Exarhos and Garrett Kaighn contributed to the work, as did Gerald Lopez, director of Business Development at the Singh Center for Nanotechnology, and two members of Amsterdam’s Center for…