Input-output description of microwave radiation in the dynamical Coulomb blockade
Journal article, 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.

tunnel-junctions

noise

josephson-junction

Author

Juha Leppäkangas

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Göran Johansson

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

M. Marthaler

Karlsruhe Institute of Technology (KIT)

Mikael Fogelström

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

New Journal of Physics

1367-2630 (ISSN)

Vol. 16 Article nr. 015015- 015015

Subject Categories

Physical Sciences

DOI

10.1088/1367-2630/16/1/015015

More information

Latest update

4/9/2018 1