Artikeln in anderen Sprachen

Measurement of quantum phase-slips in a Josephson junction chain, 21 Mai 2010

Josephson junction chains attract currently a lot of interest due to their possible applications in metrology or quantum information. For example, under microwave irradiation of frequency f, such chains could exhibit current quantization I=2nef where 2e is the charge of a Cooper pair and n is an integer number. They could be used for the definition of a new quantum current standard. In view of the potential applications, we have measured the ground state of a Josephson junction chain. Here we have analysed our results in terms of “quantum phase-slips”, the central phenomenon governing these superconducting networks.

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Heat flux at the nanoscale: beyond the Boltzmann-Stefan law, 20 Mai 2010

Does the usual Stephan-Boltzmann theory for blackbody radiation applies to nanometer-size objects ? To answer this question the heat flux in vacuum between two surfaces at different temperature and separated by distances between a micrometer to100 nm have been measured and compared to theory by two CNRS labs (Charles Fabry of Institut d’Optique and Institut Néel). At the nanometer scale, the measurements show large discrepancies with the Stefan-Boltzmann theory which describes this thermal exchange at large distances on the basis of Planck’s law. As well known, in the far field regime the heat flux exchanged between two flat parallel surfaces does not depend upon the distance between the two surfaces. Instead, in the near field regime, the measured variation is strong. The flux increase dramatically as the distance between the two surfaces becomes smaller than about one micrometer.

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