A peer-reviewed experiment confines ultracold lithium atoms between light barriers and gathers their waves into moving pulses. Changing a barrier’s motion allows different trajectories, including behaviour mathematically resembling one-way motion near an event horizon. Journal publication on 4 November follows an earlier preprint. The apparatus studies controllable wave dynamics rather than creating an astronomical black hole.
David Weld’s group at the University of California, Santa Barbara in the United States has concentrated ultracold lithium matter waves into moving pulses. Two sheets of light confine and reflect the atoms, acting as movable barriers. The experiment’s peer-reviewed journal publication appeared on 4 November in Physical Review Letters, following a preprint released on 28 January. Static barriers let the waves spread throughout the space between them.[1]
An optical lattice makes the waves propagate at nearly constant speed over the relevant range, below 1 metre per second. Moving one barrier near the cavity’s resonance, around 100 hertz, gathered waves into one narrow pulse. Different starting conditions approached the same stable trajectory. Twice the resonant frequency yielded a pair of pulses, while an abrupt phase shift exchanged stable and unstable points; the observed evolution then ran in reverse.[1]
The one-way approach toward a stable trajectory has a mathematical resemblance to light heading toward a black-hole horizon. Using slow atoms makes that motion experimentally accessible without a solid mirror moving near light speed. Residual curvature in the atoms’ propagation relation also allowed extra trajectories, examined with numerical simulations. The analogy concerns controlled wave motion; the setup created neither an astronomical black hole nor a gravitational singularity.[1]
