Steven J. Weber, Gabriel O. Samach, David Hover, Simon Gustavsson, David K. Kim, Danna Rosenberg, Adam P. Sears, Fei Yan, Jonilyn L. Yoder, William D. Oliver, Andrew J. Kerman

Published:

Quantum annealing is an optimization technique which potentially leverages
quantum tunneling to enhance computational performance. Existing quantum
annealers use superconducting flux qubits with short coherence times, limited
primarily by the use of large persistent currents $I_\mathrm{p}$. Here, we
examine an alternative approach, using qubits with smaller $I_\mathrm{p}$ and
longer coherence times. We demonstrate tunable coupling, a basic building block
for quantum annealing, between two flux qubits with small ($\sim
50~\mathrm{nA}$) persistent currents. Furthermore, we characterize qubit
coherence as a function of coupler setting and investigate the effect of flux
noise in the coupler loop on qubit coherence. Our results provide insight into
the available design space for next-generation quantum annealers with improved
coherence.