Decoherence of a tunable capacitively shunted flux qubit
quant-ph
/ Authors
R. Trappen, X. Dai, M. A. Yurtalan, D. Melanson, D. M. Tennant, A. J. Martinez, Y. Tang, J. Gibson, J. A. Grover, S. M. Disseler
and 12 more authors
J. I. Basham, R. Das, D. K. Kim, A. J. Melville, B. M. Niedzielski, C. F. Hirjibehedin, K. Serniak, S. J. Weber, J. L. Yoder, W. D. Oliver, D. A. Lidar, A. Lupascu
/ Abstract
Quantum annealing is a method to solve optimization problems that leverages quantum tunneling in a coupled qubit system. We present a detailed study of the coherence of a tunable capacitively-shunted flux qubit, designed for coherent quantum annealing applications. We find that for high qubit frequencies, thermal noise in the bias line makes a significant contribution to the relaxation, arising from the design choice to experimentally explore both fast annealing and high-frequency control. The measured dephasing rate is primarily due to intrinsic low-frequency flux noise in the two qubit loops, with additional contribution from the low-frequency noise of control electronics used for fast annealing. Our results characterize decoherence in a realistic setup for quantum annealing and are relevant for ongoing efforts toward building superconducting quantum annealers with increased coherence.