Plourde’s research on superconducting quantum bits featured in current issue of Science Magazine

Plourde’s research on superconducting quantum bits featured in current issue of Science MagazineDecember 01, 2006Sara Millersemortim@syr.edu

In the future, it may be possible to construct quantum computers capable of solving many problems that are intractable on even the most powerful classical computer. Problems such as the factorization of large numbers into the products of primes, which might take the age of the universe to solve on a conventional supercomputer, could potentially be tackled in a matter of hours on a modest quantum computer.

In order to move from theory to reality, however, many substantial challenges exist, including the need to develop architecture for a quantum computer whereby the coupling of pairs of quantum bits, or qubits–the fundamental element in a quantum computer, in comparison to the bits in a conventional computer–can be turned on and off.

Research performed by a team of scientists at the University of California, Berkeley, introduces a new approach for arrays of a particular type of qubit, the superconducting flux qubit, to interact in a controllable way using an independent circuit–a dc superconducting quantum interference device (SQUID). The team included Britton L.T. Plourde, now assistant professor of physics in Syracuse University’s College of Arts and Sciences. This research is featured in the Dec. 1 issue of Science Magazine.

The basic principle of quantum computation is that each element, or qubit, behaves according to the laws of quantum mechanics and can exist in a superposition of its states. Interactions between multiple qubits can be used to generate entanglement, where the qubit states can no longer be described individually. Such entanglement is at the heart of the power of a quantum computer. Since 2000, Plourde and seven other researchers have focused on how to fabricate and measure superconducting flux qubits, and more recently, how to switch the coupling between qubits on and off–an essential capability for implementing many quantum-computing algorithms. Plourde and the team demonstrated that such control can be achieved with two flux qubits coupled together through their mutual inductances and through the SQUID that reads out their magnetic flux states.

“This is the first demonstration of a superconducting solid state qubit system with the ability to switch the qubit coupling on and off with an experimental knob,” says Plourde. “Solid state qubit architectures are attractive because they provide a natural route for scaling to large numbers of qubits using conventional microfabrication techniques.”

Prior to coming to Syracuse in 2005, Plourde was a postdoctoral research associate at Berkeley, where he began this research. In his new lab at Syracuse, Plourde studies quantum coherence and vortex dynamics in nanofabricated superconducting devices, and his research focuses on fabricating these superconducting devices, cooling the circuits to low temperatures while minimizing their decoherence and developing techniques for entangling multiple circuits together.

Shortly after arriving at SU, Plourde was awarded the National Science Foundation’s Faculty Early Career Development (CAREER) Award, NSF’s most prestigious and competitive award for young faculty members. This award recognizes outstanding scientists and engineers who, early in their careers, show exceptional potential for leadership. Plourde’s award is funding research into the quantum coherent properties of vortices that are guided through nanofabricated superconducting structures. Such investigations will provide a novel approach to study quantum coherence at the scale of circuits and may help with the development of new building blocks for a quantum computer.

Plourde earned a bachelor’s degree with honors from the University of Michigan, where he majored in physics and music. He earned master’s degrees in physics and flute performance, and a Ph.D. in physics, from the University of Illinois at Urbana-Champaign.

Science Magazine (http://www.sciencemag.org) is the international weekly science journal published by the American Association for the Advancement of Science (AAAS).