Phys. Rev. Lett. 109, 030403 (2012)

Particle–wave duality tells us that a stream of matter can behave in a similar way to a beam of light: Giovanni Gattobigio and colleagues now show how crossing the emission from two lasers creates a matter–wave analogue of an optical beamsplitter. This concept could form an integral part of matter–wave interferometers, which are predicted theoretically to be far more sensitive than their optical counterpart.

Gattobigio et al. optically trapped a cloud of rubidium-87 atoms. Some of these atoms drifted slowly along one of the trapping beams, at a speed of about 13 mm s−1. After travelling 700 μm, the atoms met a second laser beam that crossed the first at an angle of 45°. The researchers waited 200 ms before measuring the position of the atoms. By increasing the power of the second laser, the researchers could switch from a regime where the atoms were split between travelling along both beams to one where 100% of the atoms moved along the cross beam.