# Regensburg 2019 – wissenschaftliches Programm

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# TT: Fachverband Tiefe Temperaturen

## TT 10: Focus Session: New Bright Sources of Quantum Microwaves

### TT 10.5: Hauptvortrag

### Montag, 1. April 2019, 17:15–17:45, H2

**Correlated Cooper pair transport and microwave photon emission in the Coulomb blockade** — •Juha Leppäkangas^{1, 2}, Michael Marthaler^{1}, Mikael Fogelström^{2}, and Göran Johansson^{2} — ^{1}Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, Karlsruhe, Germany — ^{2}Microtechnology and Nanoscience, MC2, Chalmers University of Technology, Göteborg, Sweden

We study theoretically electromagnetic radiation emitted by inelastic Cooper-pair tunneling. We consider a dc-voltage-biased superconducting transmission line terminated by a Josephson junction. The leading-order expansion in the tunneling coupling, similar to the "P(E)-theory", can be used to investigate the photon emission statistics in the limit of sequential (independent) Cooper-pair tunneling. By explicitly evaluating the system characteristics up to the fourth-order in the tunneling coupling, we account for dynamics between consecutively tunneling Cooper pairs. Within this approach we investigate how temporal correlations in the charge transport can be seen in the second-order coherence of the emitted microwave radiation. In particular, we find that a Coulomb blockade provided by a high zero-frequency impedance can be used to create antibunched microwave photons at a very high rate.