Non-Gaussian Noise Spectroscopy with a Superconducting Qubit*

Most quantum control and quantum error-correction protocols assume that the noise causing decoherence is described by Gaussian statistics. However, the Gaussianity assumption breaks down when a qubit is strongly coupled to a sparse environment or has a non-linear response to environmental degrees of freedom. Here, we experimentally validate an open-loop quantum control protocol that reconstructs the higher-order spectrum of injected non-Gaussian phase noise using a superconducting qubit as a noise spectrometer. This first experimental demonstration of non-Gaussian-noise spectroscopy represents a major step toward the goal of demonstrating a complete noise spectral characterization of quantum devices.