YQI Talk - Angela Kou - Microsoft Research

Event time: 
Monday, September 30, 2019 - 11:00am to 12:00pm
YQI Seminar Room See map
Event description: 

Nanowire-based superconducting circuits

Hybrid superconducting circuits, which integrate non-superconducting elements into a circuit quantum electrodynamics (cQED) architecture expand the possible applications of cQED. In such circuits, one can investigate the properties of unconventional Josephson junctions or perform readout of quantum dots and spin ensembles. In this talk, I will discuss our work building hybrid circuits based on superconductor-proximitized semiconducting nanowires. First, I will present a transmon based on a weak-link junction with high transparency. We observe a drastic decrease in the charge dispersion of the transmon as we increase the transparency of the junction. We attribute this decrease to diabatic transitions between Andreev bound states in the junction. Next, I will detail our results building a nanowire-based fluxonium. We demonstrate in-situ tuning of the Josephson energy of the fluxonium using an electrostatic gate. Our fluxonium device can also be operated up to 1T. We use the fluxonium spectrum to map out the dependence of the Josephson energy of the junction on magnetic field. At high magnetic fields, we observe the φ0-junction effect, which indicates the breaking of multiple symmetries in the junction. Our work demonstrates the utility of hybrid superconducting circuits for exploring mesoscopic physics and paves the way for manipulating Majorana zero modes in these circuits.