Spin-noise-induced synchronization between non-overlapping laser beams

Noise-induced synchronizations have led to diverse phenomena and applications. Here, we propose and demonstrate an approach towards inducing synchronizations between non-overlapping laser beams by intrinsic spin noise. Two linearly polarized and non-overlapping laser beams propagate through a vapor of flying unpolarized alkali atoms and capture their correlated noise properties by the atom-light interaction, resulting in synchronization between the two laser beams. Using correlation spectra, we demonstrate the nearly in phase synchronization at the atomic Larmor frequency between the two laser beams, which can easily be varied across a wide frequency range by the magnetic-field strength. Moreover, we show that the degree of synchronization increases with the atomic density, and the synchronization remains effective when the Larmor frequencies in the regions of the two laser beams are different. Our method may be useful for applications like secure key distribution and secure communication.