We introduce open-loop quantum control protocols for characterizing the spectral properties of non-Gaussian noise, applicable to both classical and quantum dephasing environments. The basic idea is to engineer a multi-dimensional frequency comb via repetition of suitably designed pulse sequences, through which the desired high-order noise spectra may be related to observable properties of the qubit probe. We prove that access to a high time resolution is key to achieve spectral reconstruction over an extended bandwidth, overcoming limitations of existing schemes. Non-Gaussian spectroscopy is demonstrated for a classical noise model describing quadratic dephasing at an optimal point, as well as a quantum spin-boson model out of equilibrium. In both cases, we obtain spectral reconstructions that accurately predict the qubit dynamics in the non-Gaussian regime.
@article{arxiv.1512.01575,
title = {Qubit noise spectroscopy for non-Gaussian dephasing environments},
author = {Leigh M. Norris and Gerardo A. Paz-Silva and Lorenza Viola},
journal= {arXiv preprint arXiv:1512.01575},
year = {2016}
}