Boston Chapter of the IEEE Photonics Society

Abstract:  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 provides an overview of quantum information science and superconducting artificial atoms. We then present several demonstrations of quantum coherence using these circuits: Landau-Zener-Stückelberg oscillations [1], microwave-induced qubit cooling to temperatures less than 3 mK (colder than the refrigerator) [2], and a new broadband spectroscopy technique called amplitude spectroscopy [3]. We discuss in detail a highly coherent aluminum qubit (T1=12 us, T2Echo=23 us, fidelity = 99.75%) with which we demonstrated noise spectroscopy using NMR-inspired control sequences comprising 100’s of pulses [4,5].

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] W.D. Oliver, et al., Science 310, 1653 (2005)

[2] S.O. Valenzuela, et al., Science (2006)

[3] D.M. Berns et al., Nature 455, 51 (2008)

[4] J. Bylander, et al., Nature Physics 7, 565 (2011)

[5] F.Yan, et al., Nature Comm. 4, 2337 (2013)

Biography:  William D. Oliver is a Staff Member at MIT Lincoln Laboratory, where he leads the laboratory's Cryogenic Electronics program, and a Research Affiliate with the Research Laboratory for Electronics (RLE), where he collaborates with the Orlando group. Since arriving at Lincoln in 2003, Will's research has focused on the fabrication and measurement of superconducting flux qubits for quantum information processing applications, and the development of cryogenic semiconducting and superconducting digital electronics for high-performance classical computation. Before coming to Lincoln, Will earned a Ph.D. at Stanford developing experimental techniques to realize quantum optical phenomena and entanglement with electrons in two-dimensional electron gas systems. He previously spent two years at the MIT Media Laboratory developing an interactive computer music installation called the Singing Tree as part of Tod Machover's Brain Opera.

William D. Oliver received degrees in Electrical Engineering (B.S.) and Japanese (B.A.) from the University of Rochester in 1995, the S.M. degree from the Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology in 1997, and the Ph.D. degree in Electrical Engineering with a Ph.D. minor in Physics from Stanford University in 2003.