DFG-RSF: Quantum interferometry with interacting electronic systems

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Impressive recent progress in electronics is largely due to the use of low-dimensional nanostructures such as quantum wells, quantum wires and rings, as well as due to the continuous miniaturization of electronic devices down to nanoscales. Physics at these scales is governed by quantum coherence and quantum interference effects as well as by the effects of electron-electron interaction. Interference is a mechanism for manifestation of quantum-coherent phenomena and at the same time a tool to probe coherence.The goal of this project is to investigate how strong electron-electron interactions transform the phenomenon of quantum interference. The common wisdom is that interaction causes dephasing, thus reducing the visibility of interference patterns. Yet on the other hand, interaction gives rise to new, emerging degrees of freedom, which, in turn, can interfere. We plan to investigate novel quantum systems of four types: I) Interference in Aharonov-Bohm setups with strong interaction; II) Interferometers based on split Cooper pairs; III) Interference circuits built out of edge modes in topological matter; IV) Interference, braiding and decoherence in spin (qubit) systems with zero-energy Majorana bound states. All these systems can find practical applications. For example, tiny SQUIDs of dimensions smaller than the coherence length might soon be needed in quantum-information circuits. On the other hand, our project will address the fundamental questions of many-body quantum world, e.g., the physics of many-body localization in strongly interacting disordered systems. This is a cooperation DFG-RSF project in the framework of the call for joint German-Russian project proposals in the field of physics and mathematics. The project will be carried out in collaboration with the research team of the Landau Institute for Theoretical Physics (ITP). Combination of the expertise of the KIT and ITP teams should lead to a synergy effect ensuring the best possible implementation of the project.