Multicolor Continuous-Variable Quantum Entanglement in the Kerr Frequency Comb

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). This study explores the quantum fluctuations of frequency combs and reveal the continuous-variable quantum entanglement between different comb lines of the DKS states. 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, a sudden disappearance of quantum entanglement in the center of the DKS spectrum is observed, which is attributed to the self-locking phenomena in the FWM network. These 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. The study delves into the intrinsic quantum entanglement of the dissipative Kerr soliton comb in microresonators, uncovering two distinct features. First, comb lines positioned at the spectral edge exhibit entanglement as a result of photon-pair generation and coherent photon conversion across multiple colors. Conversely, entanglement diminishes at the center of the spectrum, owing to the self-locking effect.image