First measurements with three-Josephson Junction Radiofrequency Quantum Upconverters*

The Radiofrequency Quantum Upconverter (RQU) coherently upconverts low-frequency (<300 MHz) signals to microwave frequencies, enabling precision measurement for fundamental physics experiments including measurements that evade the Standard Quantum Limit. The RQU consists of a microwave resonator terminated by a multi-junction Josephson junction interferometer. The microwave resonance frequency is modulated via a parametric coupling between the interferometer and a low-frequency pickup resonator. In this talk, we present first experimental results from Al-AlO-Al three-junction RQUs. We discuss the structure and fabrication of these RQUs. We demonstrate low-frequency upconversion from dc to ~20 MHz and frequency modulation of the microwave resonator with varying applied flux. In addition, we present phase-sensitive amplification results from our RQU, a necessary precursor to implementing quantum back action evasion.