title: Geometric aspects of composite pulses.
abstract: Unitary operations acting on a quantum system must be robust against systematic errors in control parameters for reliable quantum computing. Composite pulse technique in nuclear magnetic resonance realizes such a robust operation by employing a sequence of possibly poor-quality pulses. In this study, we demonstrate that two kinds of composite pulses-one compensates for a pulse length error in a one-qubit system and the other compensates for a J-coupling error in a two-qubit system-have a vanishing dynamical phase and thereby can be seen as geometric quantum gates, which implement unitary gates by the holonomy associated with dynamics of cyclic vectors defined in the text.
authors.affiliation: Research Center for Quantum Computing, Interdisciplinary Graduate School of Science and Engineering, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan.
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Bando
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kondo
authors.forename: Mikio
authors.initials: M
authors.lastname: Nakahara