Can a quantum state lock its phase like a clock?

Classical synchronization — fireflies flashing in unison, pendulum clocks aligning — requires a system to lock its rhythm to an external drive. This work shows that a quantum oscillator trapped in a non-classical 'Fock state' limit cycle, detectable by its negative Wigner function, can do the same. The key insight is that synchronization hinges on suppressing rare phase-slip events, which decay exponentially with drive strength, giving a clean way to measure quantum phase-locking from first principles.