The development of spin qubits with long coherence times for quantum information processing requires sources of spin noise to be identified and minimized. Although microwave-based spin control is typically used to extract the noise spectrum, this becomes infeasible when high frequency noise components are stronger than the available microwave power. Here, we introduce an all-optical approach for noise spectroscopy of spin qubits based on Raman spin rotation using Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences. By analyzing the resulting spin dynamics, we extract the noise spectrum of a dense ensemble of nuclear spins interacting with a quantum dot, which has thus far only been modelled theoretically. By extracting noise spectra under varying external magnetic fields, our Raman-based analysis provides insights for extending the spin coherence times and predicts the spin dynamics of quantum dots. This noise spectroscopy approach could provide similar insights on other spin systems for quantum information processing.

Pizza and drinks served after the talk.