Input-output description of microwave radiation in the dynamical Coulomb blockade
Artikel i vetenskaplig tidskrift, 2014

We study microwave radiation emitted by a small voltage-biased Josephson junction connected to a superconducting transmission line. An input-output formalism for the radiation field is established, using a perturbation expansion in the junction's critical current. Using output field operators solved up to the second order, we estimate the spectral density and the second-order coherence of the emitted field. For typical transmission line impedances and at frequencies below the main emission peak at the Josephson frequency, radiation occurs predominantly due to two-photon emission. This emission is characterized by a high degree of photon bunching if detected symmetrically around half of the Josephson frequency. Strong phase fluctuations in the transmission line make related nonclassical phase-dependent amplitude correlations short lived, and there is no steady-state two-mode squeezing. However, the radiation is shown to violate the classical Cauchy-Schwarz inequality of intensity cross-correlations, demonstrating the nonclassicality of the photon pair production in this region.





Juha Leppäkangas

Chalmers, Mikroteknologi och nanovetenskap, Tillämpad kvantfysik

Göran Johansson

Chalmers, Mikroteknologi och nanovetenskap, Tillämpad kvantfysik

M. Marthaler

Karlsruher Institut für Technologie (KIT)

Mikael Fogelström

Chalmers, Mikroteknologi och nanovetenskap, Tillämpad kvantfysik

New Journal of Physics

1367-2630 (ISSN)

Vol. 16 Article nr. 015015- 015015





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