Kevin D. Osborn

Laboratory for Physical Sciences at the University of Maryland

8050 Greenmead Dr.

College Park, MD  20740

osborn -at- lps -dot- umd -dot- edu

KDO Research Group

Quantum Circuits and Advanced Materials (QCAM)

For almost 2 decades scientists have studied quantum coherence in superconducting circuits near the base temperature of a refrigerator that uses a mix of helium-3 and helium-4. Superconducting circuits are especially elucidating for quantum information science and material science because they allow new regimes to be studied. For the former, we study quantum two-level defects with unprecedented characterization of the defect using a resonator with dc electric field control. In other circuits we show a new path for energy-efficient computing with the introduction of special interfaces for fluxons. On the material side, a fundamental understanding of new defect phenomena, e.g., excess quasiparticles or noise,  allows us to understand which material models may explain the phenomena which we might want to avoid or take advantage of. This allows us to work on new features for qubits with renewed interest and optimism.

A qubit defect is individually probed in a thick film for the first time, and the circuits (one example above) use cavity quantum electrodynamics (CQED). The use of CQED with superconducting qubits was pioneered by researchers at Yale U.. We extend it to tunneling two-level systems in capacitors. In recent work we have introduced calibrated dc electric-field control of TLS within related resonators.