Physica Scripta

Ramsey Fringe Measurement of Decoherence in a Novel Superconducting Quantum Bit Based on the Cooper Pair Box

D. Vion, A. Aassime, Audrey Cottet, P. Joyez, H. Pothier, C. Urbina, D. Esteve, Michel Devoret

Published Jan 1, 2002• 6 citations

Abstract

We have designed and operated a novel superconducting tunnel junction circuit which behaves as a controllable atom, with a ground and first excited state forming an effective spin 1/2. These two states are the symmetric and antisymmetric combinations of two charge configurations of a Cooper pair box. Any spin orientation corresponding to an arbitrary superposition of these two states can be prepared by applying NMR-like microwave pulses to the gate of the box. The spin state is readout by measuring the voltage response to a probe current pulse applied to the bridge formed by the two junctions of the box and an additional large, shunting junction. In a sample whose transition period is 60 ps, coherent superpositions decay with a 0.5 μs time constant, as measured by a Ramsey fringes experiment. This result is a step towards the realization of a solid-state quantum information processor.

DOI: 10.1238/physica.topical.102a00162

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