Nonclassical photon pair production in a voltage-biased Josephson junction
Lundi 21 janvier 2013 15:00
- Duree : 1 heure
Lieu : Salle "Remy Lemaire" K 223 (1er étage) bât. K de l’institut Néel/CNRS - 25 rue des martyrs - Grenoble
Orateur : Juha LEPPAKANGAS
We investigate electromagnetic radiation emitted by a small voltage-biased Josephson junction connected to a superconducting transmission line . At frequencies below the well known emission peak at the Josephson frequency (2eV/h), extra radiation is triggered by quantum fluctuations in the electromagnetic environment. For weak tunneling couplings and typical ohmic transmission lines, the corresponding photon flux spectrum is symmetric around half the Josephson frequency, indicating that the photons are predominately created in pairs. By establishing an input-output formalism for the microwave field in the transmission line, we give further evidence for this nonclassical photon pair production, demonstrating that it violates the classical Cauchy-Schwarz inequality for two-mode flux cross correlations. In connection to recent experiments, we also consider a stepped transmission line, where resonances increase the signal-to-noise ratio.
Contact : max.hofheinz@cea.fr
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