Whose bright idea was that? Prof Padgett says the crucial component is the mask - a software controlled liquid crystal device: "That mask looks a little bit like a bull's-eye target. But hang on a minute. If a photon is a particle, how is it possible to impose a pattern on it? It's because photons exist in the exotic and rather wonderful quantum realm, where the rules of the reassuringly solid world in which we live tend to lose their grip.
They exhibit what physicists call "wave-particle duality": they behave like both a wave and a particle. So you can send them round a racetrack two by two like particles, yet change the shape of one of them as if it was a wave. Oh yes. Which is why the researchers say it might help to think of a bicycle race. The peloton - the main bunch of riders - may be moving at a constant speed.
But within the bunch an individual rider may be moving more slowly, dropping back for a rest or a drink. Meanwhile other riders in the bunch are moving faster to get to the front. The bunch is a beam of light, travelling at - yes - the speed of light. The riders are photons, travelling at their individual speeds. For Dr Giovannini it's been a satisfying intellectual and experimental challenge: "It mostly comes from a question we asked ourselves two and a half years ago.
We just kept working on it. It's just one of those big, fundamental questions you may want to ask yourself at some point in the pub one night. This finding shows unambiguously that the propagation of light can be slowed below the commonly accepted figure of ,, metres per second, even when travelling in air or vacuum. The effect is biggest when the lenses used to create the beam are large and when the distance over which the light is focused is small, meaning the effect only applies at short range.
Professor Padgett added: "It might seem surprising that light can be made to travel more slowly like this, but the effect has a solid theoretical foundation and we're confident that our observations are correct. We expect that the effect will be applicable to any wave theory, so a similar slowing could well be created in sound waves, for example. The team's paper, titled 'Spatially Structured Photons that Travel in Free Space Slower than the Speed of Light', is published in Science Express , which provides electronic publication of selected papers in advance of print in the journal Science.
Materials provided by University of Glasgow. Note: Content may be edited for style and length. Science News. Story Source: Materials provided by University of Glasgow. Journal Reference : D. Giovannini, J. Romero, V. Poto ek, G. Ferenczi, F. Speirits, S. Barnett, D. A team of researchers from the Israel Institute of Technology and the Institute of Pure and Applied Mathematics in Brazil discovered a method of theoretically bringing the speed of light to a halt by capitalizing on "exceptional points"—coordinates at which two separate light emissions reach each other and merge into a single one, according to Phys.
A paper describing the research was published in the scientific journal Physical Review Letters. Slow-light technologies could help improve our telecommunications systems, as well as our quantum computers. Existing research shows us that light can be slowed to an infinitesimal fraction of its vacuum speed in two ways, according to the new paper: trapping it inside either ultracold atom clouds or inside waveguides made with photonic crystals.
The first involves aiming a laser into a cloud of ultracold sodium atoms, the researchers wrote in their paper. When the laser is abruptly switched off, a slow pulse of light is imprinted onto the atoms, essentially bringing the light to a halt by absorbing it; the imprinted shape can then be converted back into a photon.
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