Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 36: TR: Poster Session

TT 36.30: Poster

Thursday, March 25, 2010, 14:00–18:00, Poster A

Characterization of non-Gaussian quantum noise via dephasing of qubits — •Stefan Kessler and Florian Marquardt — Department of Physics, Arnold Sommerfeld Center for Theoretical Physics, and Center for NanoScience, Ludwig-Maximilians-Universität München, Theresienstr 37, D-80333 München, Germany

Until now, a major restriction of solid state qubits as quantum memories is their small coherence times due to the unavoidable coupling to their noisy environment. On the other hand the decoherence of the qubit can be used as unique probe for the time correlations of the environmental noise fluctuations.

While most of the previous work on decoherence has been based on environments modeled by Gaussian fluctuators or ensembles of classical fluctuators, we address here genuine quantum non-Gaussian noise. Features of quantum non-Gaussian noise have been observed in recent experiments in mesoscopic physics, where strong coupling between the system and few environmental fluctuators is dominant.

In this work, we consider the pure dephasing of a two level system due to its quantum environment and introduce an effective quantum noise spectrum based on the time evolution of the qubit coherence. We show that this spectrum provides a convenient way to distinguish experimentally between Gaussian and non-Gaussian noise and can be used to characterize the non-Gaussianity of the noise. The results are illustrated by different models of non-Gaussian environments. We discuss the implications for experimental setups measuring quantum noise.