Two competing teams of physicists have found a way of manipulating atoms in a Bose-Einstein condensate (BEC) to form soliton waves. Solitons are stable localized waves that propagate through a medium without spreading. William Phillips from the US National Institute of Standards and Technology (NIST) in Gaithersburg and colleagues used pulses of laser light to "imprint" a standing wave into a BEC of sodium atoms and a matter-wave interferometer to prove that the wave maintains its phase pattern as it travels through the material (Science 287 97). Meanwhile, Sven Burger from the Institut für Quantenoptik at the University of Hannover and colleagues independently achieved the same feat with a dilute vapour of rubidium atoms (to be published in Phys. Rev. Lett).
Bose–Einstein condensates are trapped atoms that are cooled to low temperatures and occupy the same quantum state. They are ideal for studying and manipulating quantum effects such as solitons and vortices as they occur on the macroscopic rather than the microscopic scale. In both of the new experiments the soliton waves moved through the BECs at velocities less than the speed of sound, confirming that the effect was not sound waves. Indeed as soon as the solitons reached the speed of sound, they disappeared. “The ability to imprint phase profiles onto a condensate and the resolve the profile using a separate technique is a lovely advance,” says Keith Burnett an atomic physicist from Oxford University.
