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Blobrana


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Negative refraction
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For years, researchers have struggled to find an efficient way to develop lenses that do not lose portions of light as it passes throughan effect that hinders the performance of lasers, medical diagnostic imaging equipment and sensor systems. Now researchers led by a group at Princeton University have developed a new technique using nanosize materials that sets the stage for new lenses that eliminate the errors and image distortion inherent in today's optical technologyand may one day be used to check for toxic chemicals in the air and the body.

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Blobrana


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RE: Light
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Physicists in France can watch as a mirror-lined box gradually decides how many photons it contains. Their experiment, which uses atoms to count the number of photons in the box without destroying them, will help us to better understand the mysterious role of measurement in quantum mechanics.
Quantum mechanics says the world is innately random: an isolated system will remain in a fuzzy superposition of all possible states until we measure it, at which point it will collapse with a certain probability into just one state. Recently physicists have discovered that this collapse can be witnessed step-by-step if a series of special quantum non-demolition (QND) measurements are performed. Now, Serge Haroche and colleagues from the Ecole Normale Supérieure have developed a new QND technique to see, for the first time, the step-by-step collapse of a coherent light field.

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Blobrana


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The speed of light
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It was supposed to be the one speed limit you cannot break.
But scientists claim to have demonstrated there is the possibility of travel faster than the speed of light.
The feat contradicts one of the key tenets of Einstein's special theory of relativity - that nothing, under any circumstances, can move faster than 186,000 miles per second, or the speed of light.

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Ed ~ it is just an illusion

-- Edited by Blobrana at 18:53, 2007-08-22

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Blobrana


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Atomic laser
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Scientists have reported a way to achieve the so-called atomic laser, a breakthrough predicted by Albert Einstein in 1925, the Italian news agency ANSA reported today.
A Florence University research team led by Massimo Inguscio and Giovanni Modugno used potassium isotopes to build an "atomic condensate" squeezed into a harmonious whole by a magnetic field, similar to a theoretical model envisaged by Einstein and fellow physicist Satyendra Nath Bose.

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Blobrana


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X-ray free electron laser
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World's first X-ray free electron laser is on course to completion
Argonne reached another milestone in the design and construction of the Linac Coherent Light Source (LCLS) undulator system.
LCLS will be the world's first X-ray free electron laser to produce hard X-rays when it becomes operational at the Stanford Linear Accelerator Center (SLAC) in 2009. It will be the first X-ray laser to combine the brilliance of laser sources with the penetrating power and atomic sensitivity of X-rays. Argonne is a partner laboratory on the project and is responsible for the 130-meter undulator system, including magnets, support structures, beam diagnostics, controls and vacuum systems.
Undulators are the heart of the LCLS free electron laser, providing a precise magnetic field through which an electron beam will travel. The undulators' magnetic fields force the electrons to oscillate back and forth and produce large amounts of X-rays. These X-rays interact back on the electrons and force them to bunch at X-ray wavelengths. When this occurs, the electrons emit their light coherently, causing a large gain in radiation power that raises the X-rays' intensity.

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Blobrana


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RE: Light
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Overcoming the limits of resolution
This years Julius Springer Prize for Applied Physics will be awarded to the Göttingen-based researcher Stefan Hell for his revolutionary discovery that resolutions far below the diffraction limit can be achieved in a fluorescence microscope using conventionally focused light.
The STED (stimulated emission depletion) microscope invented by Hell is the first optical microscope to show details in resolutions far below the light wavelength using conventional lenses. This technique opens up new possibilities in the life sciences because it allows non-invasive imaging of the inside of cells. The prestigious award from the scientific publisher Springer will be awarded for the tenth time this year and carries prize money of US $5,000. Stefan Hell will receive the prize during a plenary session at the trade show Laser.World of Photonics 2007 in Munich on 19 June.

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Blobrana


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Photons
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Cavity quantum electrodynamics is a sub-field of quantum optics. Speaking at the EPL symposium, Physics In Our Times held on 9 May at the Foundation Del Duca de lInstitut de France, Paris Professor Serge Haroche from the Collège de France and the École Normale Supérieure in Paris, explained how he and his colleagues manipulate and control single atoms and single photons interacting in a cavity, which is a box made of highly reflecting walls. By studying the behaviour of these atoms and photons in this protected environment, the physicists can illustrate fundamental aspects of quantum theory, such as state superpositions, complementarity and decoherence. This research is related to the physics of quantum information, a new domain at the frontier of information science and physics that tries to harness the logic of the quantum world to realise tasks in communication and computing that classical devices cannot achieve.

"During the 20th century, quantum physics has given us new technologies that have changed our lives for example the computer, the laser and magnetic resonance imaging to name a few. However, quantum laws have counterintuitive aspects that defy common sense. This has led to a paradox: although we all take advantage of quantum physics, it remains very strange - even some of the scientists that developed the theory, such as Einstein, Schrödinger and de Broglie, were uneasy about its deep meaning" - Professor Serge Haroche .

Prof. Haroche and his team have recently succeeded in trapping a single photon in a box on the time scale of seconds and have detected this photon many times without destroying it. The researchers have achieved this by sending atoms across the box and measuring the imprint left on the atoms by the photon.

"This is a new kind of light detection called quantum non-demolition.  Until now, single photons were always destroyed upon detection" - Professor Serge Haroche.

The result means that it is now possible repeatedly to extract information from the same photon. This is important because the major part of all information we get from the universe come from light.

"Developing a new way of seeing could have applications in quantum science.  A photon could share its information with an ensemble of atoms to build up an entangled state of light or matter"

Attempting to manipulate and control quantum systems raises important questions about the transition between quantum and classical behaviour.

"Fundamentally, the goal is to understand nature better. Applications, such as quantum communication machines, will certainly come but what they will be useful for is not yet clear. This is why research is so exciting unpredictable things keep happening all the time."

Prof. Haroches group is currently working with atoms and photons in cavities but related work is being done by other groups on trapped ions and cold atoms in optical potential wells, with superconducting junction or quantum dots in solid state devices.

"Although the technologies may differ widely, the quantum and information science concepts used are the same. We are therefore witnessing a kind of unification between different fields of research that is very promising."

Source: Europhysics Letters

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Blobrana


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RE: Light
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French team of physicists succeeds in trapping a single photon in a box within seconds, detecting it many times without destroying it

Measuring a photon repeatedly without destroying it has been achieved for the first time, enabling researchers to study an individual quantum object with a new level of non-invasiveness. Physicists have long realised that it is possible to perform non-destructive observations of a photon with a difficult-to-execute technique known as a "quantum non-demolition" (QND) measurement. After many years of experimental effort, researchers in France (Serge Haroche, Ecole Normale Superieure) have demonstrated the first QND measurement of a single quantum object, namely a photon bouncing back and forth between a pair of mirrors (a "cavity"). A conventional photodetector measures photons in a destructive manner, by absorbing the photons and converting them into electrical signals. "Eating up" or absorbing photons to study them is not required by fundamental quantum mechanics laws and can be avoided with the QND technique demonstrated by the French researchers. In their technique, a photon in a cavity is probed without absorbing any net energy from it. (Of course, Heisenberg's Uncertainty Principle ensures that counting a photon still disturbs the "phase" associated with its electric and magnetic fields.) In the experiment, a rubidium atom passes through a cavity. If a photon is present, the atom acquires a phase shift which can easily be detected. Sending additional rubidium atoms through the cavity allowed the researchers to measure the photon repeatedly without destroying it or, as the French would say, "Avoir le beurre et l'argent du beurre" ("Getting the butter and money out of it at the same time"). This technique can allow physicists to study the behaviour of a photon during its natural lifespan; it can potentially allow researchers to entangle  an arbitrary number of atoms and build quantum logic gates.

Source: The American Institute of Physics Bulletin of Physics News
Number 439 July 16, 1999

(Nogues et al., Nature, 15 July; see also Scientific American, April 1993; figure at www.aip.org/physnews/graphics.)

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Blobrana


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Everyone has seen a prism bend light. Now researchers have constructed a material that bends visible light in the opposite way. The odd effect, known as negative refraction, is similar to what is needed in far-out proposals for creating a cloak of invisibility. For now, however, the device only works in two dimensions, so construction of invisible spaceships will have to wait.

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Blobrana


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Lene Hau has already shaken scientists' beliefs about the nature of things. Albert Einstein and just about every other physicist insisted that light travels 186,000 miles a second in free space, and that it can't be speeded-up or slowed down. But in 1998, Hau, for the first time in history, slowed light to 38 miles an hour, about the speed of rush-hour traffic.
Two years later, she brought light to a complete halt in a cloud of ultracold atoms. Next, she restarted the stalled light without changing any of its characteristics, and sent it on its way. These highly successful experiments brought her a tenured professorship at Harvard University and a $500,000 MacArthur Foundation award to spend as she pleased.

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