The first time this has been achieved, offers physicists a better chance to study the kinship between Bose-Einstein condensates (BEC) and superfluids. Both involve the establishment of an ensemble in which many atoms join together in a single quantum entity. But they’re not quite the same thing. In a bath of liquid helium at low temperatures, for example, nearly 100% of the atoms are in a superfluid state but only about 10% are in a BEC state (in a BEC millions of atoms have become, in a sense, a single atom). But physicists generally believe that most or all of a BEC is superfluid. Scientists have been able to stir up quantized vortices in BEC samples, one indication that BECs are superfluid. But until now researchers had not been able to get BECs to move around a track in a persistent flow, another sign of superfluidity.
The new experiment, performed by Nobel laureate William Philips and his colleagues at NIST-Gaithersburg and the Joint Quantum Institute of NIST and the University of Maryland, chilled sodium atoms in a toroidal trap, set them into motion with laser light, and observed a flow for as long as 10 seconds, when the condensate started to come undone because the delicate magnetic and optical trapping parameters tuned to contain the atoms had drifted from their ideal settings. One of the scientists on the project, Kristian Helmerson (firstname.lastname@example.org), says that neutral atoms flowing in a toroidal vessel could be fashioned into the atom analog of a superconducting quantum interference device (or a SQUID, for short, which is used as a sensitive detector of magnetism); this BEC device, sensing not magnetism but slight changes in direction, could serve as a sensitive gyroscope, possibly for navigation purposes (Ryu et al., Physical Review Letters, upcoming article)