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[en] We have measured the mass, width and two-photon decay width of the ηc and ηc' mesons in two-photon collisions using 483 fb-1 of data collected with the Belle detector at the asymmetric-energy e+e- collider KEKB. Interference effects have been studied
[en] Full Text:Path entangled photon states can be used to overcome classical limits on the accuracy of interferometric measurements such as the diffraction limit. These states are superpositions of finding n photons in one out of two (or more) paths. Using stimulated parametric down-conversion, we propose and demonstrate a method for generating heralded multiphoton path entanglement, without applying post-selection. parametric down-conversion is relatively easy to produce compared to pure Fock states as demanded by other proposals. By a special coincidence detection at one down converted arm, the photons of the second arm non-locally bunch into the desired state. Entanglement in photon number is created between two polarization modes rather than two paths. A polarization beam-splitter and a 2 wave plate can translate between the two representations. The experimental generation of a two-photon path entangled state was detected by observing interference at half the photon wavelength. The scheme is generally extendable to higher photon numbers
[en] Experimental results of investigation of two-photon interactions at LEP (CERN) are presented. Experimental conditions provided a possibility of investigation of the whole set of two-photon interactions from the production of lepton pairs in collisions of quasi-real photons to interactions of high-virtual photons.
[en] We report a way of manipulating the spontaneous emission process leading to a spatial modulation of spontaneous decay. The effect is observed in the case of coherently driven atoms separated by less than a transition wavelength. It is quantified by Glauber's photon-photon second-order correlation function. We show that the photon arrival time, usually regarded as an entirely random process, depends not only on where a photon is detected but also on where a former photon had been recorded previously. Our results shed light on the unexpected consequences of state reduction and entanglement for the fundamental process of spontaneous emission
[en] The Editor-in-Chief has retracted this article because post-publication review has shown that there are serious flaws with respect to the acquisition of data through the instrumentation used. The lack of sufficient information on experimental procedures makes it impossible to reproduce the author’s approach. For example, it is not defined which portion of light is analysed in the spectral measurements shown in the article. As a consequence the interpretation of the results (e.g. in terms of “microlasing”) must be considered unsound. The author does not agree with this retraction.
[en] 2 research groups have announced the making of interferences into which 3 photons take part. In one case 3 entangled photons are created and introduced into an interferometer to reveal interferences of this state with itself. In the other case 3 photons from 3 different light sources are made to interfere and the interference pattern depend on the sum of all the time shifts from the photon couples taken 2 by 2. This achievement may be important for cryptography and quantum computers. (A.C.)