Nonequilibrium interactions between GaAs-based quantum devices

Jörg P. Kotthaus, Center for NanoScience and Fakultät für Physik, Ludwig-Maximilians-Universität München, Germany Quantum point contacts (QPCs) on GaAs-AlGaAs heterostructures, routinely employed as sensitive charge detectors for adjacent mesoscopic quantum devices, are shown to cause back-action phenomena when moderately biased. Recent studies of such non-equilibrium interactions caused by electrons ballistically injected across a QPC are discussed, in which currents induced in unbiased detector circuits, adjacent but electrically separated from the biased QPC emitter, are investigated. Incorporating suitable voltage-tunable barriers it becomes possible to energetically analyse the quanta generated in the emitter that cause the non-equilibrium in the detector. Our studies show conclusively that acoustic phonons, emitted by back-scattering of excited electrons, are a dominant cause of such non-equilibrium interactions, and can become detrimental to quantum coherent operations.

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