Abstract
Abstract Topological quantum optics that manipulates the topological protection of quantum states has attracted special interests in recent years. Here we demonstrate valley photonic crystals implementing topologically protected transport of the continuous frequency entangled biphoton states. We numerically simulate the nonlinear four-wave mixing interaction of topological valley kink states propagating along the interface between two valley photonic crystals. We theoretically clarify that the signal and idler photons generated from the four-wave mixing interaction are continuous frequency entangled. The numerical simulation results imply that the entangled biphoton states are robust against the sharp bends and scattering, giving clear evidence of topological protection of entangled photon pairs. Our proposal paves a concrete way to perform topological protection of entangled quantum states operating at telecommunication wavelengths.
Highlights
Topological insulators, striking paradigms that implement the insulating bulk, and conducting edge, have prompted the contexts of condensed matter physics
The results reveal that edge states of the pump, signal and idler are robust to the sharp bends due to the overlap between the frequencies of four-wave mixing (FWM) interactions and operation bandwidths of valley kink states
With optimized parameters of valley photonic crystals (VPCs), the frequencies of pump, signal and idler photons are all localized inside the operation bandwidth of topological valley kink states
Summary
Topological insulators, striking paradigms that implement the insulating bulk, and conducting edge, have prompted the contexts of condensed matter physics. Photonic analog of topological insulators emulating quantum Hall effect in two-dimensional (2D) photonic systems were first demonstrated by Haldane and Raghu [1, 2]. Inspired by advanced behaviors of topological protection, researchers are focusing on exploiting the concepts of topology in the fields of nonlinear and quantum optics. Topological physics provides new exciting aspects of nonlinear optics. Topological protected third-harmonic generation has been experimentally realized [18] in photonic topological metasurfaces emulating the QSH effect. A configuration of the graphene metasurface imitating the quantum Hall effect theoretically proves [19] that the four-wave mixing (FWM) is topologically protected with the breaking of time-reversal symmetry. The aforementioned nonlinear and topological quantum photonic devices may provide a manipulated platform for on-chip nonlinear manipulation or quantum information processing
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