Abstract : A qubit that experiences pure dephasing due to its interaction with an environment can be easily turned into a sensor of environmental fluctuations - one just needs to periodically apply simple unitary operations to the qubit in order to turn into into noise spectrometer (see arXiv:1705.02262 for a review). This works particularly well if the environmental noise has Gaussian statistics. I will explain the issues related to quantum vs classical nature of Gaussian noise, and show how these two cases can be distinguished with a qubit that has a particular form of coupling to the environment (for an example calculation for an NV center see arXiv:1909.06438). Time permitting, I will discuss how to sense environmental noise cross-correlations (and also the non-Gaussian character of the noise) with two qubits, and how to see a back-action of the qubit on its environment in such a setting. ______________________________________________ Zoom meeting details Topic: Quantum Information and Quantum Computing Working Group Time: Apr 23, 2020, 04:00 PM Warsaw Join Zoom Meeting: QIQCWG-ZOOM Meeting ID: 640 279 690Password: tp4C,kERx If you encounter any problems with connecting to the Zoom meeting, please email firstname.lastname@example.org directly.