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Coherent Quantum Dynamics of a Superconducting Flux Qubit

I. Chiorescu·Y. Nakamura·C. J. P. M. Harmans·J. E. Mooij
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Abstract

We have observed coherent time evolution between two quantum states of a superconducting flux qubit comprising three Josephson junctions in a loop. The superposition of the two states carrying opposite macroscopic persistent currents is manipulated by resonant microwave pulses. Readout by means of switching-event measurement with an attached superconducting quantum interference device revealed quantum-state oscillations with high fidelity. Under strong microwave driving it was possible to induce hundreds of coherent oscillations. Pulsed operations on this first sample yielded a relaxation time of 900 nanoseconds and a free-induction dephasing time of 20 nanoseconds. These results are promising for future solid-state quantum computing.

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I. Chiorescu, Y. Nakamura, C. J. P. M. Harmans, J. E. Mooij. 2003-05-20. Coherent Quantum Dynamics of a Superconducting Flux Qubit. https://doi.org/10.1126/science.1081045

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