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Input-output description of microwave radiation in the dynamical Coulomb blockade

Juha Leppäkangas (Institutionen för mikroteknologi och nanovetenskap, Tillämpad kvantfysik) ; Göran Johansson (Institutionen för mikroteknologi och nanovetenskap, Tillämpad kvantfysik) ; M. Marthaler ; Mikael Fogelström (Institutionen för mikroteknologi och nanovetenskap, Tillämpad kvantfysik)
New Journal of Physics (1367-2630). Vol. 16 (2014), p. Article nr. 015015.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: josephson-junction, tunnel-junctions, noise

Denna post skapades 2014-03-14. Senast ändrad 2017-10-03.
CPL Pubid: 194995


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Institutioner (Chalmers)

Institutionen för mikroteknologi och nanovetenskap, Tillämpad kvantfysik



Chalmers infrastruktur