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3 min read<\/p>\n3 min read<\/p>\n
Here\u2019s what you\u2019ll learn when you read this story:<\/p>\n
When you try to clip a photon using a barrier, it becomes more photons than before.Photons are inherently asymmetrical because one side has an infinite trailing tail.We now know photons are like worms\u2014they can regrow from either half.<\/p>\n
In newly published research, three physicists from the University of Oslo in Norway posed an interesting dinner-party question for fellow particle nerds: What happens when you \u201ctruncate\u201d a photon? After all, a photon can\u2019t be split the way non-elementary particles can be split, but it can be smushed into various quantum phenomena and combinations thereof. The new research appears now<\/a> in the peer-reviewed journal Physical Review Letters.<\/p>\n \u201cA photon, being an elementary particle<\/a>, cannot be cut in two halves. Still, it is clearly possible to remove a part of an optical pulse, e.g., using an optical shutter,\u201d the team explained in their introduction. In other words, the light is almost like a stream, and it can be cut off and then released. \u201cIf a photon is truncated in this way, what is the resulting state? Despite being a simple question, it appears that it has not been asked before.\u201d<\/p>\n Optical pulses are like tiny, extremely precise lasers<\/a>. Just a few photons pass through at once, released during an infinitesimal opening. Clipping this stream with an optical shutter is not as simple as it sounds, partly because single photons \u201chave infinite tails.\u201d As the team explained, \u201cSurprisingly, we will find that a truncated photon is a complicated state involving photon numbers up to infinity. In other words, by \u2018cutting away part of the photon\u2019 with a shutter, we effectively create a bunch of new photons. In principle, this is the case even if the shutter is turned off slowly.\u201d<\/p>\n Maybe it\u2019s now clear why nobody had ever bothered to ask this seemingly simple question: the answer defies common sense. Cut off the \u201chead\u201d of a photon, and\u2014like the mythical hydra\u2014it doesn\u2019t die or shrink. It multiplies, erupting into a swarm of brand-new photons. That strange outcome is possible in part because a photon isn\u2019t a neat, symmetrical packet of light<\/a>; its \u201cinfinite tail\u201d trails off in only one direction, meaning where you make the cut matters enormously. To pin down exactly what happens at that moment of truncation, the Oslo team built a pristine hypothetical scenario\u2014following a single photon through the shutter\u2014and crunched the numbers.<\/p>\n
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