  With growing interest in quantum technologies, possibilities of synchronizing
quantum systems has garnered significant recent attention. In experiments with
dilute ensemble of laser cooled spin-1 $^{87}{Rb}$ atoms, we observe phase
difference of spin coherences to synchronize with phases of external classical
fields. An initial limit-cycle state of a spin-1 atom localizes in phase space
due to dark-state-polaritons generated by classical two-photon tone fields. In
particular, when the two couplings fields are out of phase, the limit-cycle
state synchronizes only with two artificially engineered, anisotropic decay
rates. Furthermore, we observe a blockade of synchronization due to quantum
interference and emergence of Arnold tongue-like features. Such anisotropic
decay induced synchronization of spin-1 systems with no classical analogue can
provide insights in open quantum systems and find applications in synchronized
quantum networks.
