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.