Extended Data Fig. 1: SBS laser noise.

Shown is the measurement of the 674-nm SBS laser subsystem’s frequency noise before and after the application of feedforward stabilization. The SBS laser subsystem features a white noise floor of 3 Hz² Hz⁻¹ before feedforward and a gradual increase in noise at lower offset frequencies. An integration over the noise spectral density yields a full-width at half-maximum linewidth of 45 Hz, while a calculation of the white-noise limited linewidth at large offset frequencies yields 9 Hz. With feedforward turned on, the SBS laser subsystem’s noise increases slightly and exhibits additional noise peaks that arise from the RF signal generator used for feedforward correction. The integrated linewidth increases to 51 Hz.