Quantum computing and condensed matter physics with microwave photons

Life after charge noise: recent results with transmon qubits

A. A. Houck, Jens Koch, M. H. Devoret, S. M. Girvin and R. J. Schoelkopf


 We review the main theoretical and experimental results for the transmon, a superconducting charge qubit derived from the Cooper pair box. The increased ratio of the Josephson to charging energy results in an exponential suppression of the transmon’s sensitivity to 1/f charge noise. This has been observed experimentally and yields homogeneous broadening, negligible pure dephasing, and long coherence times of up to 3 µs. Anharmonicity of the energy spectrum is required for qubit operation, and has been proven to be sufficient in transmon devices. Transmons have been implemented in a wide array of experiments, demonstrating consistent and reproducible results in very good agreement with theory.