Zero temperature quantum dissipation using a SQUID-tunable boundary - Tim Duty

The strong nonlinearity provided by superconducting Josephson tunnel junctions can be used in experiments for parametric down conversion of microwave fields. This has many potential uses for nanoscale engineered quantum systems, such as quantum-limited amplification, generation of non-classical microwave radiation, and the possibility of implementing quantum feedback control for solid-state quantum systems. In this talk, I describe two sets of experiments where the parametric driving is implemented using a superconducting quantum interference device (SQUID). The SQUID is integrated into a on-chip microwave transmission line, and thereby acts as a tunable boundary condition for microwave fields. In the first set of experiments, we investigate the quantum dynamics of a tunable coplanar cavity, which we model as a parametric oscillator with a quartic nonlinearity. When  driven above threshold, the oscillator exhibits bistability, and we observe a novel type of quantum tunneling that we call "quantum activation". In the second set of experiments, we investigate the dynamical Casimir effect (DCE) in a broadband, open 1D transmission line, where we observe two-mode squeezing of the emitted radiation.