Flux qubits in a planar circuit quantum electrodynamics architecture: quantum control and decoherence

Abstract

We report experiments on superconducting flux qubits in a circuit quantum electrodynamics (cQED) setup. Two qubits, independently biased and controlled, are coupled to a coplanar waveguide resonator. Dispersive qubit state readout reaches a maximum contrast of $72\%$. We find intrinsic energy relaxation times at the symmetry point of $7\mu \text{s}$ and $20\mu \text{s}$ and levels of flux noise of $2.6\mu {\Phi }_0/\sqrt{\text{Hz}}$ and $2.7\mu {\Phi }_0/\sqrt{\text{Hz}}$ at 1 Hz for the two qubits. We discuss the origin of decoherence in the measured devices. These results demonstrate the potential of cQED as a platform for fundamental investigations of decoherence and quantum dynamics of flux qubits.

8 pages, including supplementary information

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