Two years after researchers at the Massachusetts Institute of Technology developed a coherent beam of atoms they called an atom laser, physicists at the National Institute of Standards and Technology in Gaithersburg, Md., have found a way to control the direction of the atom beam.

The researchers worked with gaseous Bose-Einstein condensate, in which all atoms behave as a single entity. To achieve this state, scientists trapped sodium atoms in a magnetic field and cooled them to a millionth of a degree above absolute zero. They then aimed two optical lasers -- one from the left side and one from the right -- into the super-cold condensate. The atoms absorbed photons from one laser and emitted photons into the other beam. The process transferred momentum to the atoms and thrust them in the direction of one of the two laser beams. To control the direction of the atoms, the scientists increased the difference between the two frequencies of the optical lasers.