Condensed Matter Seminar: Prof. Angela Kou, University of Illinois Urbana-Champaign


Location: 184 Nieuwland Science Hall (View on map )

Using a superconducting transmon to probe mesoscopic phenomena

Prof. Angela Kou
University of Illinois Urbana-Champaign

Superconducting circuits have extremely long coherence times and have been used widely as qubits, quantum-limited amplifiers, and mixers. In this talk, I will discuss using superconducting circuits as sensors for mesoscopic and superconducting phenomena.

As an example, I will show our work using a transmon qubit to probe the Andreev bound states in a superconductor-quantum dot-superconductor (S-QD-S) junction. In such a device, the competition between the charging energy of the dot and superconductivity stabilizes different spin ground states in the junction. We perform spectroscopy on the transmon to map out the full phase diagram of the S-QD-S system as a function of several control parameters: gate voltages, external flux, and magnetic field applied parallel to the wire. We then probe the anomalous Josephson effect in the junction, which results from breaking of multiple symmetries in the junction in an applied magnetic field. Finally, we build a spin qubit from the S-QD-S device and demonstrate strong coupling between the spin qubit and the transmon, paving the way for transduction between the spin qubit and transmon.

Hosted by Prof. Jin