Selective control of edge-channel trajectories by scanning gate microscopy

Electronic Mach-Zehnder interferometers in the quantum Hall (QH) regime are currently discussed for the realization of quantum information schemes. A recently proposed device architecture employs interference between two co-propagating edge channels. Here we demonstrate the precise control of individual edge-channel trajectories in quantum point contact devices in the QH regime. The biased tip of an atomic force microscope is used as a moveable local gate to pilot individual edge channels. Our results are discussed in light of the implementation of multi-edge interferometers. (C) 2009 Elsevier B.V. All rights reserved.