Just like human drivers, some photons are faster than others depending on road conditions. Nearly identical materials can make a huge difference to travel time, as discovered by Joint Quantum Institute (JQI), College Park, Md., scientists who built a specialized interferometer that can "stop-watch" individual photons. A partnership of the National Institute of Standards and Technology (NIST), Gaithersburg, Md., and the Univ. of Maryland, College Park, and Georgetown Univ., Washington, D.C., have found a remarkably large difference in the time it takes photons to pass through nearly identical stacks of materials with different arrangements of refractive layers. The technique ultimately could provide an empirical answer to a long-standing puzzle over how fast light crosses narrow gaps that do not permit the passage of conventional electromagnetic waves.
展开▼
