Links for 2009-10-11

"Quantum information science relies on superpositions of quantum states with a definite phase relation, but such superpositions are inherently fragile against interactions with their environment. Fortunately, if some kind of common property bounds these interactions, it is possible, though by no means easy in a practical setting, to come up with states that are essentially immune to their environment. In papers appearing in Physical Review A and Physical Review Letters, Magnus RÃ¥dmark and Mohamed Bourennane at Stockholm University in Sweden and Marcin WiÅniak and Marek Å»ukowski at Uniwesytet GdaÅski in Poland report that they have prepared a six-photon entangled state that is immune to the environmental disturbances commonly occurring in optical fibers."

"We report on a direct measurement of a phase shift on a weak coherent beam by a single 87Rb atom in a Mach-Zehnder interferometer. By strongly focusing the probe mode to the location of the atom, a maximum phase shift of about 1° is observed experimentally."

"Present ultrafast laser optics is at the frontier between atto- and zeptosecond photon pulses, giving rise to unprecedented applications. We show that high-energetic photon pulses down to the yoctosecond time scale can be produced in heavy-ion collisions. We focus on photons produced during the initial phase of the expanding quark-gluon plasma. We study how the time evolution and properties of the plasma may influence the duration and shape of the photon pulse. Prospects for achieving double-peak structures suitable for pump-probe experiments at the yoctosecond time scale are discussed."

It's got a beat, and I suppose one could dance to it.