Dresden 2003 – wissenschaftliches Programm
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SYQD: Quantum decoherence in solid state physics
SYQD 1: Quantum Decoherence in Solid State Physics I
SYQD 1.1: Hauptvortrag
Dienstag, 25. März 2003, 14:00–14:30, HSZ/01
Manipulating the Quantum State of an Electrical Circuit — •Audrey Cottet1,2, D. Vion2, A. Aassime2, P. Joyez2, H. Pothier2, C. Urbina2, D. Esteve2, and M. H. Devoret2 — 1Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland — 2Groupe Quantronique, SPEC CEA-Saclay, France
We have engineered a superconducting circuit, nicknamed ”quantronium”, which is based on the Cooper pair box. The quantronium can be placed in a coherent superposition of two states which involve a macroscopic number of Cooper pairs. We have succeeded in controlling this superposition by using sequences of microwave signals, analogue to those used in NMR experiments. The quantronium was specially designed to avoid the decoherence due to electrical impedances. However, there remain residual sources of decoherence such as the charge noise induced by randomly moving charges in the insulating material close to the circuit. The best coherence time we have measured is T=0.5 microseconds, which corresponds to a quality factor Q=25000. Spectroscopic and echoes experiments provide information about the decoherence mechanisms involved.