Coherent operation of a gap-tunable flux qubit

Xiaobo Zhu; Kemp, Alexander; Saito, Shiro; Semba, Kouichi
September 2010
Applied Physics Letters;9/6/2010, Vol. 97 Issue 10, p102503
Academic Journal
We replace the Josephson junction defining a three-junction flux qubit’s properties with a tunable direct current superconducting quantum interference devices (dc-SQUIDs) in order to tune the qubit gap during the experiment. We observe different gaps as a function of the external magnetic pre-biasing field and the local magnetic field through the dc-SQUID controlled by high-bandwidth on chip control lines. The persistent current and gap behavior correspond to numerical simulation results. We set the sensitivity of the gap on the control lines during the sample design stage. With a tuning range of several gigahertz on a qubit dynamics timescale, we observe coherent system dynamics at the degeneracy point.


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