Qubit noise spectroscopy for non-Gaussian dephasing environments

TL;DR

This paper develops open-loop quantum control protocols to characterize non-Gaussian noise spectra affecting qubits, enabling high-resolution spectral reconstruction over broad bandwidths for classical and quantum environments.

Contribution

It introduces a multi-dimensional frequency comb approach for non-Gaussian noise spectroscopy, overcoming previous bandwidth and resolution limitations.

Findings

Successfully reconstructs non-Gaussian noise spectra in classical and quantum models.

Demonstrates accurate prediction of qubit dynamics in non-Gaussian regimes.

Achieves high time resolution for spectral reconstruction over extended bandwidths.

Abstract

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.