By Peter Weiss
Last year, for the first time, scientists slowed light pulses to a halt and briefly stored them in a gas before permitting them to reemerge at normal speed (SN: 1/27/01, p. 52: Light Stands Still in Atom Clouds). Now, a team of researchers in the United States and Korea has achieved the same result with light in a solid.
Many scientists envision applying this remarkable new means of controlling nature to quantum computers and other future devices whose operation will be based on quantum mechanics (SN: 12/8/01, p. 364: Gadgets from the Quantum Spookhouse).
Stopping and storing light, and the applications these capabilities could lead to, would be “much cheaper and much easier” in solids than in gases, says Alexey V. Turukhin of JDS Uniphase Corp. in Eatontown, N.J.
In the Jan. 14 Physical Review Letters, Turukhin and his colleagues report using off-the-shelf crystals of yttrium silicate with some added praseodymium atoms to bring pulses of yellow laser light to a temporary standstill. As the pulses passed through the supercooled crystal, the scientists also shined a second laser on the material. The two beams interfered and combined with each other to create a beam that interacted with a quantum property of the praseodymium atoms known as spin.
That interaction slowed down the light. Then, to stop the
pulse altogether, the researchers shut off the second laser, effectively trapping the light pulse’s energy and quantum identity in the praseodymium atoms’ spins. When the second laser was turned back on, the atoms released their entrapped light.
Turukhin, who was at the Massachusetts Institute of Technology at the time of the experiments, and his colleagues report that they could store a pulse of light for up to half a millisecond. Turukhin says that’s long enough for many applications. Those include storing and processing information in future computers that would exchange quantum information between matter and light.
