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The application of topology in optics has led to a new paradigm in developing photonic devices with robust properties against disorder. Although significant progress on topological phenomena has been achieved in the classical domain, the quantum regime has remained unexplored. In this talk, I discuss two recent developments in the quantum regime:
(1) We demonstrate a strong interface between single quantum emitters and topological photonic states. Our approach creates robust counter-propagating edge states at the boundary of two distinct topological photonic crystals. We demonstrate the chiral emission of a quantum emitter into these modes and establish their robustness against sharp bends. This approach may enable the development of quantum optics devices with built-in protection, with potential applications in quantum simulation and sensing.
(2) Spontaneous parametric processes such as down-conversion (SPDC) and four-wave mixing (SFWM) have long been the common sources of quantum light, for instance, correlated photon pairs and heralded single photon. These spontaneous processes are mediated by vacuum fluctuations of the electromagnetic field. Therefore, by manipulating the electromagnetic mode structure, for example, using nanophotonic systems, one can engineer the spectrum of generated photons. However, such manipulations are susceptible to fabrication disorders which are ubiquitously present in nanophotonic systems.
We demonstrate a topological source of correlated photon pairs where the spectrum of generated photons is robust against fabrication disorder. Specifically, we use the topological edge states to achieve an enhanced and robust generation of photons using SFWM and show that they outperform their topologically-trivial counterparts. We show the non-classical nature of intensity correlations between generated photons and the anti-bunching of photons using conditional measurements. Our results could pave the way for topologically robust quantum photonic devices.
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