(Phys.org) —When C. K. Hong, Z. Y. Ou and Leonard Mandel demonstrated destructive quantum interference between pairs of indistinguishable bosons in their 1987 paper1, they did so with massless photons. Their protocol – christened the Hong–Ou–Mandel (HOM) effect – remained unchanged until recently, when scientists at The University of Queensland, Brisbane proposed an experiment to implement HOM in the matter-wave regime. This massive-particle version of the HOM effect uses pair-correlated atoms produced in a collision of two Bose–Einstein condensates and subjected to two laser-induced so-called Bragg pulses. (A Bose-Einstein condensate, or BEC, is a phase of matter in which bosons in a dilute gas enter the same quantum state when cooled to a temperature near absolute zero – that is, 0 K or −273.15 °C – and macroscopic-scale quantum effects appear. Bragg pulses replicate atom optics analogs of the mirror and beam-splitter elements of the photonic HOM interferometer.) By simulating the atom-optics HOM effect using colliding condensates and predicting an interference visibility of about 70%, the researchers say that their matter-wave approach may lead to stronger tests of quantum mechanics, including Bell inequality violations and the Einstein–Podolsky–Rosen paradox, the latter now being known as entanglement.