Multiple-path interferometer with a single quantum obstacle

¹ Max-Planck-Institut für Physik komplexer Systeme Nöthnitzer Str. 38, 01187 Dresden, Germany
² Kamerlingh Onnes Laboratory, Universiteit Leiden P.O. Box 9504, 2300 RA Leiden, The Netherlands
³ Laboratoire Kastler Brossel, Département de Physique de l'Ecole Normale Supérieure 24 rue Lhomond, 75231 Paris, France
⁴ Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506 2300 RA Leiden, The Netherlands

Received: 22 August 2001
Accepted: 14 December 2001

Abstract

We consider the scattering of particles (kinetic energy ε) by an obstacle which tunnels coherently between two positions (tunnel splitting Δ), for arbitrary values of and scattering strength U. The obstacle mimics two classical scatterers at fixed positions when . Interference disappears when , but can be recovered if the elastic-scattering channel is detected only. At intermediate values of ε there is a systematic interplay of the coherent tunnel motion and the ballistic particle motion. We show that the transmission probability can remain finite even in the limit because the particle can evade the obstacle systematically. We discuss the realization of a quantum obstacle in mesoscopic systems.