A single nanodiamond operating at room temperature can be used as an ultrafast optical switch, a key component for future light-based information processing and computing. Faster and more powerful transistors and integrated circuits that are based on photons rather than electrons are central to the development of optical signal processes. Not only do photons transfer data at much higher rates than electrons, but they generate much less heat in the process. The nanomanipulation of an artificial atom. Courtesy of ICFO. In 2009, a group at ETH Zurich created an optical transistor from a single dye molecule operated at cryogenic temperatures. The new study, led by researchers at the Institute of Photonics Sciences (ICFO) in Barcelona showed that a single nanodiamond can operate as an ultrafast optical switch, but at room temperature. Research on single quantum emitters, either molecules or quantum dots, has focused on achieving stable and efficient light emission with well-defined properties, the researchers say, but a long-term, stable source of such single photons, and at room temperature, has remained a challenge. The ICFO team used nitrogen-vacancy centers, which are artificial atoms protected by a diamond shell, making them immune to both blinking and bleaching. This gives their electron spin a long coherence time, even at room temperature. Pumping with a continuous-wave green (532 nm) laser excited the nanodiamond to its "on" state, and the researchers discovered that illumination with a nonresonant, continuous-wave, near-IR laser was an efficient and fast way to switch it "off." Based on this simple concept, they modulated the optical nanodiamond "on" and "off" at extremely high speeds, demonstrating its robustness and viability for very fast information processing and quantum computer operations. In 2009, a team at ETH Zurich created an optical transistor from a single molecule, but it worked at cryogenic temperatures. A new study, led by researchers at the Institute of Photonics Sciences in Barcelona shows that a single nanodiamond can operate as an ultrafast optical switch, but at room temperature. Courtesy of Robert Lettow. "What is really attractive about our discovery is that our nanoswitch combines very small dimensions (compatible with integrating a large number of them in a small area) with very fast response time (meaning lots of operations in a short time) and operation at room temperature," said researcher Romain Quidant. The work was a collaborative effort between his group and that of Javier García de Abajo at ICFO's ICREA, the Catalan Institution for Research and Advanced Studies. A logical next step would be to couple a single nitrogen-vacancy center to highly confined optical guided modes, such as those supported by a quasi-one-dimensional plasmonic waveguide, the team reports in its paper, which appears in the Oct. 13 online edition of Nature Physics. For more information, visit: www.icfo.eu