reflects the energy spectrum of the artificial atom. In turn, the quantum interference can be leveraged to facilitate non-adiabatic quantum control.

We begin this article with an introduction to the superconducting persistent-current qubit [@Mooij99a; @Orlando99a] and an overview of Landau-Zener-Stückelberg (LZS) transitions. We then present three experimental works that utilize LZS transitions in a strongly-driven persistent-current qubit. The first is Mach-Zehnder-type interferometry between repeated LZS transitions [@Oliver05a], for which we observed quantum interference fringes in n-photon transition rates [@Berns06a], with n=1 …50. The second is microwave-induced cooling [@Valenzuela06a], by which we achieved effective qubit temperatures less than 3 mK, a factor 10-100 times lower than the environmental temperature. The third is amplitude spectroscopy [@Berns08a; @Rudner08a], a spectroscopy technique that monitors the system response to amplitude rather than frequency. Amplitude spectroscopy allowed us to probe the energy spectra of our artificial atom from 0.01 - 120 GHz, while driving it at a fixed frequency near 0.2 GHz. Finally, we conclude by considering the application of LZS transitions to quantum information science and technology.

Persistent-Current Qubit: Superconducting Artificial Atom {#sec:PCQB}
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Superconducting artificial atoms exhibit a high degree of quantum coherence, and there have been numerous proposals and demonstrations of quantum phenomena 