  In a traveling wave microresonator, the cascaded four-wave mixing (FWM)
between optical modes allows the generation of frequency combs, including
intriguing dissipative Kerr solitons (DKS). In this study, we explore the
quantum fluctuations of frequency combs and unveil the quantum features of
solitons. The entanglement of DKS exhibits two distinct characteristics. For
modes located at the spectral edge with a small number of excitations,
different comb modes with multiple colors become entangled due to photon-pair
generation and coherent photon conversion stimulated by the FWM. Notably, we
observe a sudden disappearance of quantum entanglement in the center of the DKS
spectrum, which is attributed to the self-locking phenomena in the FWM network.
Our findings demonstrate the prominent quantum nature of DKS, which is of
fundamental significance in quantum optics and has the potential to be utilized
in quantum networking and distributed quantum sensing applications.
