* Astronomy

NIST detector counts photons with 99 percent efficiency

Scientists at the National Institute of Standards and Technology (NIST) have developed the world's most efficient single photon detector, which is able to count individual particles of light travelling through fibre optic cables with roughly 99 percent efficiency. The team's efforts could bring improvements to secure electronic communication, advanced quantum computation and the measurement of optical power.
Using essentially the same technology that permitted them to achieve 88 percent detection efficiency five years ago, the team has enhanced its ability to detect photons largely by improving the alignment of the detector and the optical fibres that guide photons into it. The basic principle of the detector is to use a superconductor as an ultra-sensitive thermometer. Each individual photon hitting the detector raises the temperature - and increases electrical resistance - by a minute amount, which the instrument registers as the presence of a photon.
According to team member Sae Woo Nam, the advantage of this type of single photon detector is that the new detector design not only measures lower levels of light than have ever been possible, but does so with great accuracy.
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Physicists play Lego with photons

While many of us enjoyed constructing little houses out of toy bricks when we were kids, this task is much more difficult if bricks are elementary particles. It is even harder if these are particles of light - photons, which can only exist while flying at an incredible speed and vanish if they touch anything.
A team at the University of Calgary has accomplished exactly that: by manipulating a mysterious quantum property of light known as entanglement, they are able to mount up to two photons on top of one another to construct a variety of quantum states of light - that is, build two-story quantum toy houses of any style and architecture.
The results of their research, written in the paper 'Quantum-optical state engineering up to the two-photon level', will be published on Nature Photonics's website on Feb. 14.
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Electromagnetically induced transparency (EIT) is a coherent optical nonlinearity which renders a medium transparent over a narrow spectral range within an absorption line. Extreme dispersion is also created within this transparency "window" which leads to "slow light"
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Scientists at the University of Adelaide have made a breakthrough that could change the world's thinking on what light is capable of.
The researchers in the University's new Institute for Photonics & Advanced Sensing (IPAS) have discovered that light within optical fibres can be squeezed into much tighter spaces than was previously believed possible.
Optical fibres usually act like pipes for light, with the light bouncing around inside the pipe. As you shrink down the size of the fibre, the light becomes more and more confined too, until you reach the ultimate limit - the point beyond which light cannot be squeezed any smaller.
This ultimate point occurs when the strand of glass is just a few hundred nanometres in diameter, about one thousandth of the size of a human hair. If you go smaller than this, light begins to spread out again.
The Adelaide researchers have discovered they can now push beyond that limit by at least a factor of two.

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