Coherence oscillations produced by non-Gaussian quantum noise

The usual models for dissipative environments involve a bath of harmonic oscillators, producing Gaussian fluctuations. However, modern experiments on dephasing in qubits and electronic interferometers indicate strong coupling to non-Gaussian quantum noise. Most strikingly, the coherence (interference contrast) may oscillate as a function of time and other control parameters. We present the theory behind a recent ``controlled dephasing'' experiment involving an electronic Mach-Zehnder interferometer strongly coupled to the non-Gaussian shot noise of a detector edge channel [cond-mat/0610634,cond-mat/ 0611372], as well as applications to qubits dephased by shot noise or two-level fluctuators.