2005/10/21 by Mika Sillanpaa, Teijo Lehtinen, Antti Paila +2 · 2 citations
Physics and Astronomy · #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevlett.96.187002
published as Phys. Rev. Lett. 96, 187002 (2006). · 22 pages, 5 figures
arxiv created 2005/10/21 · arxiv updated 2015/06/25
Quantum-mechanical systems having two discrete energy levels are ubiquitous in nature. For crossing energy levels, depending on how fast they approach each other, there is a possibility of a transition between them. This phenomenon is known as Landau-Zener tunneling and it forms the physical basis of the Zener diode, for example. The traditional treatment of the Landau-Zener tunneling, however, ignores quantum-mechanical interference. Here we report an observation of phase-sensitive interference between consecutive Landau-Zener tunneling attempts in an artificial two-level system formed by a Cooper-pair-box qubit. We interpret the experiment in terms of a multi-pass analog to the well-known optical Mach-Zehnder interferometer. In our case, the beam splitting occurs by Landau-Zener tunneling at the charge degeneracy, while the arms of the Mach-Zehnder interferometer in energy space are represented by the ground and excited state. Our Landau-Zener interferometer can be used as a high-resolution detector for phase and charge owing to interferometric sensitivity-enhancement. The findings also demonstrate new methods for qubit manipulations.