Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field

作者：Florian Luthi, Thijs Stavenga, Oscar Enzing, Alessandro Bruno, Christian Dickel, Nathan K. Langford, M. A. Rol, Thomas Sand Jespersen, Jesper Nygård, Peter Krogstrup, L. DiCarlo · 发表于：Physical Review Letters · 年份：2018 · DOI：10.1103/physrevlett.120.100502 · 被引用次数：103 · 研究领域：Quantum and electron transport phenomena、Topological Materials and Phenomena、Quantum Information and Cryptography

We present an experimental study of flux- and gate-tunable nanowire transmons with state-of-the-art relaxation time allowing quantitative extraction of flux and charge noise coupling to the Josephson energy. We evidence coherence sweet spots for charge, tuned by voltage on a proximal side gate, where first order sensitivity to switching two-level systems and background 1/f noise is minimized. Next, we investigate the evolution of a nanowire transmon in a parallel magnetic field up to 70 mT, the upper bound set by the closing of the induced gap. Several features observed in the field dependence of qubit energy relaxation and dephasing times are not fully understood. Using nanowires with a thinner, partially covering Al shell will enable operation of these circuits up to 0.5 T, a regime relevant for topological quantum computation and other applications.