We propose on-chip topological transport of quantum frequency comb (10 THz) with frequency entanglement in valley photonic crystals. Our proposal could open new avenues for high-dimensional information processing utilizing topology in quantum system.
Optical frequency combs in integrated photonics have widespread applications in high-dimensional optical computing, high-capacity communications, high-speed interconnects, and other paradigm-shifting technologies. However, quantum frequency combs with high-dimensional quantum states are vulnerable to decoherence, particularly in the presence of perturbations such as sharp bends. Here we experimentally demonstrate the robust on-chip topological transport of quantum frequency combs in valley photonic crystal waveguides. By measuring the time correlations and joint spectral intensity of the quantum frequency combs, we show that both quantum correlations and frequency entanglement remain robust against sharp bends, owing to the topological nature of the quantum valley Hall effect. We also demonstrate that dissipative Kerr soliton combs with a bandwidth of 20 THz maintain their spectral envelope and low-noise properties even in the presence of structure perturbations. These topologically protected optical frequency combs offer robust, complex, highly controllable, and scalable light sources, promising significant advances in high-dimensional photonic information processing.
Abstract Recent advances in manipulating topological phases in quantum systems have promised integrated quantum devices with conspicuous functionalities, such as robustness against fabrication defects. At the same time, the introduction of quantum frequency combs enables extreme expansion of quantum resources. Here, it theoretically propose the generation of high‐dimensional entangled quantum frequency combs via four‐wave mixing processes in the valley‐Hall topological resonators. Specifically, it demonstrates two irregular photonic crystal resonators supporting the whispering‐gallery resonator modes that lead to coherent quantum frequency combs at telecommunication wavelengths. By using the Schmidt decomposition, It shows that the quantum frequency combs are frequency entangled, and it also concludes that the effective dimensions of quantum frequency combs in these two resonators are at least seven and six, respectively. Moreover, these quantum frequency combs inherit the topological protection of valley kink states, showing robustness against defects in the resonators. The topological quantum frequency combs have shown intriguing potentiality in the generation and control of topologically protected high‐dimensional quantum states in integrated photonic crystal platforms.
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.
Today’s quantum technology relies on the realization of large-scale non-classical systems in practical formats to enable quantum-accelerated computing, secure communications and enhanced sensing. Optical on-chip quantum frequency combs, characterized by many equidistantly spaced frequency modes, allow the storage of large amounts of quantum information. The combination with control techniques, using accessible state-of-the-art telecommunications infrastructure, can constitute a powerful frequency-domain quantum circuit with new functionalities and represents an approach towards realizing practical large-scale controllable quantum systems. In this presentation, we will review approaches for the efficient realization of quantum frequency combs in on-chip waveguide structures and micro-resonators. We will show their applicability for the realization of quantum systems with considerably enhanced complexity, particularly generating and manipulating on-chip multi-photon and high-dimensional quantum states as well as discrete high-dimensional cluster states, laying at the basis of measurement based-quantum computing. Building on this, the realization of frequency-domain Hong-Ou-Mandel interference of independent photons, fundamental to quantum information processing, as well as an outlook on frequency-domain circuits will be discussed.