First double-slit experiment with antimatter

Interference patterns of the wave-particle dualism observed for the first time at positrons

Typical interference in the double-slit experiment with electrons - their antiparticles, the positrons, behave the same way, as an experiment now reveals. © Alexandre Gondran / CC-by-sa 4.0
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Double nature also in the "opposite world": For the first time physicists have carried out the classic double-slit experiment with positrons - the antimatter equivalent of electrons. As with normal particles, an interference pattern was revealed. This provides the first experimental evidence that the quantum wave-wave-particle dualism is also true for antiparticles, as the researchers in the journal "Science Advances" report.

The double-slit experiment is a classic in physics. Coherent light is allowed to fall on an aperture with two slits. On an observation screen behind the aperture then shows an interference pattern of light and dark stripes. With the help of this experiment, scientists proved the wave-particle dualism of light, but also of electrons, neutrons and even molecules.

But what about the exotic counterpart of our normal matter - antimatter? Does it have the same wave-particle dualism as normal elementary particles? After all, antiparticles such as positrons, antiprotons or antihydrogen behave in many ways just like their normal counterparts. Even the spectrum of antihydrogen and its positron transition are the same.

Double-slit test with positrons

"But an analogue of the double-slit experiment has never been done with an antimatter system, " explain Simone Sala of the University of Milan and his colleagues. They have now made up for it. For their experiment, the researchers generated positron from the decay of radioactive sodium-22 and accelerated it in a special accelerator of the L-NESS laboratory in Como.

The researchers shot this positron beam on a gold-coated grid of silicon nitride, which had slits at a distance of about one micrometer. Behind the grid, a silver bromide emulsion serves as a detector for the impacting antiparticles. "The emulsion can detect the point of impact of each single positron with sub-micron resolution, " the researchers said. display

Classical interference pattern behind the gap

The result: in fact, the researchers registered behind the column lattice a typical interference pattern, which, according to their calculations, results from a true wave interference of the antiparticles. The distance of the interference peaks was in the range predicted by quantum theory. "This is the first time that we have observed any antimatter interference, " say Sala and his team.

The experiment thus shows that antimatter particles apparently behave like normal elementary particles in this aspect - they also show a wave-particle dualism. "The positrons are emitted as point-like particles from the radioactive source, interacting with each other as Broglie waves, and are then re-registered as single points by the emulsion detector, " the researchers explain. (Science Advances, 2019; doi: 0.1126 / sciadv.aav7610)

Source: Science Advances

- Nadja Podbregar