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Quantum computing: Scientists stop light in a cloud of atoms

In the latest Star Wars episode, The Force Awakens, villain Kylo Ren uses The Force to stop a laser blast mid-air as it heads towards him.
Now researchers at the Australian National University (ANU) have done something similar by using a cloud of very cold atoms to stop light moving.

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Scientists slow the speed of light

A team of Scottish scientists has made light travel slower than the speed of light.
They sent photons - individual particles of light - through a special mask. It changed the photons' shape - and slowed them to less than light speed.

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Title: On possible origin of an anisotropy in the speed of light in vacuum
Author: E.P. Savelova

We assume the spacetime foam picture in which vacuum is filled with virtual wormholes. In the presence of an external field the distribution of wormholes changes. We consider an anisotropic distribution of wormholes and analyze its relation to the speed of light. We show that speed of light acquires an anisotropic character and save the normal dispersion a gas of virtual wormholes may possess also an anomalous dispersion, i.e., when the light velocity exceeds that in the vacuum.

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Title: How stable is the photon?
Authors: Julian Heeck

Yes, the photon. While a nonzero photon mass has been under experimental and theoretical study for years, the possible implication of a finite photon lifetime lacks discussion. The tight experimental upper bound of the photon mass restricts the kinematically allowed final states of photon decay to the lightest neutrino and/or particles beyond the Standard Model. We discuss the modifications of the well-measured cosmic microwave background spectrum of free streaming photons due to photon mass and lifetime and obtain model-independent constraints on both parameters---most importantly a lower direct bound of 3 yrs on the photon lifetime, should the photon mass be at its conservative upper limit.

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'Twisted light' data-boosting idea sparks heated debate

An idea to vastly increase the carrying capacity of radio and light waves has been called into question.
The "twisted light" approach relies on what is called light's orbital angular momentum, which has been put forth as an unexploited means to carry data.

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Title: Black-Hole Bombs and Photon-Mass Bounds
Authors: Paolo Pani, Vitor Cardoso, Leonardo Gualtieri, Emanuele Berti, Akihiro Ishibashi

Generic extensions of the standard model predict the existence of ultralight bosonic degrees of freedom. Several ongoing experiments are aimed at detecting these particles or constraining their mass range. Here we show that massive vector fields around rotating black holes can give rise to a strong superradiant instability which extracts angular momentum from the hole. The observation of supermassive spinning black holes imposes limits on this mechanism. We show that current supermassive black hole spin estimates provide the tightest upper limits on the mass of the photon (mv<4x10^{-20} eV according to our most conservative estimate), and that spin measurements for the largest known supermassive black holes could further lower this bound to mv<10^{-22} eV. Our analysis relies on a novel framework to study perturbations of rotating Kerr black holes in the slow-rotation regime, that we developed up to second order in rotation, and that can be extended to other spacetime metrics and other theories.

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Title: Closing the window for massive photons
Authors: Sergio A. Hojman, Benjamin Koch

Working with the assumption of non-zero photon mass and a trajectory that is described by the relativistic world-line of a spinning top we find, by deriving new astrophysical bounds, that this assumption is in contradiction with todays experimental results. This yields the conclusion that the photon has to be exactly massless.

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Heavy photons are too light to be behind dark matter

Sadly, dark matter is not made of light. That may sound obvious, but many physicists were hoping that photons - particles of light - could help us to piece together the nature of the mysterious stuff thought to make up 85 per cent of the universe's matter.
Instead, readings from Vitor Cardoso of the Technical University of Lisbon in Portugal and colleagues seem to have quashed this idea.
Some theories had hinted that "heavy photons", hypothetical versions of the more familiar massless particles, might be dark matter. According to that idea, the heavy photon would have a small amount of mass and might carry an unknown fundamental force that allows it to interact only with ordinary photons - effectively hiding it from the visible world.

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Orbital angular momentum
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'Twisted light' carries 2.5 terabits of data per second

Researchers have clocked light beams made of "twisted" waves carrying 2.5 terabits of data - the capacity of more than 66 DVDs - per second.
The technique relies on manipulating what is known as the orbital angular momentum of the waves.

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Cloaking a moment in time

In movie magic, people and objects can appear or disappear or move from place to place in an instant. Just stop the camera, move things around and start it again. Now, Cornell researchers have demonstrated a similar "temporal cloak" -- albeit on a very small scale -- in the transport of information by a beam of light.
The trick is to create a gap in the beam of light, have the hidden event occur as the gap goes by and then stitch the beam back together. Alexander Gaeta, professor of applied and engineering physics, and colleagues report their work in the Jan. 5 issue of the journal Nature.

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