Ben Alemán of the University of Oregon and his colleagues have drilled into the two-dimensional hexagonal boron nitride, an analog of graphene colloquially known as "white graphene", to generate artificial atoms that are sustained under ambient conditions. Writing in the journal Nano Letters, the team suggests that the work might lead the way to secure quantum communication devices and all-optical quantum computing. [Ziegler, J. et al., Nano Lett. (2019) DOI: 10.1021/acs.nanolett.9b00357].
Team member Joshua Ziegler, drilled holes with a diameter of just 500 of nanometers that were four nanometers deep into a sheet of hexagonal boron nitride. The team used a process that is whimsically described as in some ways resembling pressure-washing, but instead of a water jet they used a focused beam of ions to etch circles into the white graphene. They then heated the material in oxygen at high temperatures to remove the residue.
"The big breakthrough is that we've discovered a simple, scalable way to nanofabricate artificial atoms on to a microchip, and that the artificial atoms work in air and at room temperature," explains Alemán
Ziegler then used optical confocal microscopy to look at tiny spots of light coming from the regions that had been drilled in the 2D material. After analyzing the light with photon counting techniques, he discovered realized that the individual bright spots were emitting light at the lowest possible level; a single photon at a time. These patterned bright spots can be thought of as artificial atoms possessing many of the same properties of actual atoms, such as this ability to emit single photons. Since his arrival at Oregon, Alemán had planned to pursue the idea that artificial atoms could be generated in white graphene. Of course, a team at another university had identified artificial atoms in flakes of white graphene before Alemán's current success. Nevertheless, he built on that discovery and suggests that the fabrication of artificial atoms is the first step towards harnessing them as single-photon sources for quantum photonic circuits.
"Our work provides a source of single photons that could act as carriers of quantum information as qubits," Alemán explains. "We've patterned these sources, creating as many as we want, where we want." He adds that the team would next like to pattern these single photon emitters into circuits or networks on a microchip so they can communicate with each other.