We show how to achieve full spectral characterization of general multiaxis additive noise. Our pulsed spectral estimation technique is based on sequence repetition and frequency-comb sampling and is applicable even to models where a large qubit energy-splitting is present (as is typically the case for spin qubits in semiconductors, for example), as long as the noise is stationary and a second-order (Gaussian) approximation to the controlled reduced dynamics is viable. Our new result is crucial to extending the applicability of these protocols, now standard in dephasing-dominated platforms such as silicon-based qubits, to experimental platforms where both T1 and T2 processes are significant, such as superconducting qubits.
@article{arxiv.1906.03565,
title = {Extending comb-based spectral estimation to multiaxis quantum noise},
author = {Gerardo A. Paz-Silva and Leigh M. Norris and Félix Beaudoin and Lorenza Viola},
journal= {arXiv preprint arXiv:1906.03565},
year = {2019}
}