Measurement and feedforward correction of the fast phase noise of lasers

Lasers are the workhorse of quantum engineering in the atomic-molecular-optic community. However, phase noise of the laser, which can be especially large in popular semiconductor-based lasers, can limit gate fidelity. Here we present a fully fiberized instrument detecting and correcting the fast, submicrosecond, phase fluctuations of lasers. We demonstrate a measurement noise floor of less than 0.1 ${\mathrm{Hz}}^{2}$/Hz and a noise suppression of more than 20 dB for Fourier frequencies in the 1--10 MHz region (reaching up to 30 dB at 3 MHz), where noise is critical for Rydberg-based quantum gates. We observe the improvement offered by this fast-phase-noise eater on a Raman transition driven by two such stabilized lasers. These measurement and correction techniques are important tools for high-fidelity manipulation of the excited electronic states of atoms and molecules.