“Abandon every hope, all you who enter.”
(Dante’s Inferno)
Like the entrance to hell in Dante’s Inferno, this gate is one-way only. Physicists have created a laser barrier that lets atoms through only in one direction — mimicking the “demon,” proposed by James Clerk Maxwell in a thought experiment, that selectively opens or closes a microscopic gate to let some atoms through but not others.
The method could cool gases of atoms or molecules to temperatures close to absolute zero, making new kinds of experiments possible. “It’s a very nice demonstration of the one-way barrier concept,” comments Gabriel Price of the University of Texas at Austin. The laser barrier concept was first set forth in 2005 by Austin’s Mark Raizen and his collaborators as a way to cool gases to extremely low temperatures.