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Quantum Physics, quant-ph, Physics, Atomic Physics, physics.atom-ph, Physics, Optics, physics.optics
Abstract:
Superradiant lasers based on atomic ensembles exhibiting ultra-narrow optical
transitions can emit light of unprecedented spectral purity and may serve as
active atomic clocks. We consider two frequency-detuned active atomic clocks,
which are coupled in a cascaded setup, i.e. as master & slave lasers, and study
the synchronization of the slave to the master clock. In a setup where both
atomic ensembles are coupled to a common cavity mode such synchronization
phenomena have been predicted by Xu et al. [Phys. Rev. Lett. 113, 154101
(2014)] and experimentally observed by Weiner et al. [arXiv:1503.06464 (2015)].
Here we demonstrate that synchronization still occurs in cascaded setups but
exhibits distinctly different phase diagrams. We study the characteristics of
synchronization in comparison to the case of coupling through a common cavity.
We also consider synchronization through a classical channel where light of the
master laser is measured phase sensitively and the slave laser is injection
locked by feedback and compare to the results achievable by coupling through
quantum channels.