Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 25: FV-internes Symposium ”Superconducting Qubits and π-junctions”

TT 25.3: Invited Talk

Thursday, March 11, 2004, 10:30–11:00, H20

Quantum dynamics of persistent current qubits — •Kees Harmans — Quantum Transport Group, Department of NanoScience/TNW, Delft University of Technology,Delft, The Netherlands

Quantum bits employing superconductivity come in a few varieties, comprising (Cooperpair) charge, (condensate) phase, and persistent current or flux. In a flux-based qubit the loop-shape topology allows a persistent current to circulate in opposite directions, leading to two quantum states that are well separated from a higher lying manifold of states. The properties of these two states can be fully engineered during the fabrication, and largely controlled during the experiment. Employing flux-flux coupling in addition allows a flexible qubit-qubit interaction scheme towards multi-qubit systems. Using burst microwave magnetic excitation resonant between the levels and pulsed fluxes, both of well controlled amplitude and duration/interval, allows full quantum control of the qubit(s). We will present a series of experiments demonstrating the quantum behavior of a single qubit, comprising Rabi, Ramsey and echo-type oscillations. In addition some results on a coupled two-qubit experiment will be discussed. The role of decoherence in our quantum experiments will be highlighted, including the effect of the qubit state detection.

11:00 Pause