Superconducting qubits are artificial atoms assembled from electrical circuit elements. When cooled to cryogenic temperatures, these circuits exhibit quantized energy levels. Transitions between levels are induced by applying pulsed microwave electromagnetic radiation to the circuit, revealing quantum coherent phenomena analogous to (and in certain cases beyond) those observed with coherent atomic systems.

This talk begins with an overview of quantum information science and superconducting artificial atoms.  We present recent results from a highly coherent persistent-current qubit (T₁=12 us, T₂^Echo=23 us) [1] with a single-qubit randomized benchmarking fidelity 99.8% [2]. We have performed noise mitigation and noise spectroscopy during free evolution using dynamical decoupling sequences comprising 100’s of pulses [1]. More recently, we have demonstrated noise mitigation and spectroscopy during driven evolution using rotary echo [3] and spin-locking techniques [4].  

These experiments exhibit a remarkable agreement with theory, and are extensible to other solid-state qubit modalities. In addition to fundamental studies of quantum coherence in solid-state systems, we anticipate these devices and techniques will advance qubit control and state-preparation methods for quantum information science and technology applications.


[1] J. Bylander, et al., Nature Physics 7, 565 (2011)
[2] S. Gustavsson, et al., PRL 108, 170503 (2012)
[3] S. Gustavsson, et al., PRL 110, 040502 (2013)
[4] F. Yan, et al., Nature Comm. 4, 2337 (2013)