A topological source of quantum light

Abstract

Quantum light is characterized by distinctive statistical distributions that are possible only because of quantum mechanical effects. For example, single photons and correlated photon pairs exhibit photon number distributions with variance lower than classically allowed limits. This enables high-fidelity transmission of quantum information and sensing with lower noise than possible with classical light sources. Most quantum light sources rely on spontaneous parametric processes such as down-conversion and four-wave mixing. These processes are mediated by vacuum fluctuations of the electromagnetic field. Therefore, by manipulating the electromagnetic mode structure, for example with dispersion-engineered nanophotonic systems, the spectrum of generated photons can be controlled. However, disorder, which is ubiquitous in nanophotonic fabrication, causes device-to-device spectral variations. Here we realize topologically robust electromagnetic modes and use their vacuum fluctuations to create a quantum light source in which the spectrum of generated photons is much less affected by fabrication-induced disorder. Specifically, we use the topological edge states realized in a two-dimensional array of ring resonators to generate correlated photon pairs by spontaneous four-wave mixing and show that they outperform their topologically trivial one-dimensional counterparts in terms of spectral robustness. We demonstrate the non-classical nature of the generated light and the realization of a robust source of heralded single photons by measuring the conditional antibunching of photons, that is, the reduced likelihood of photons arriving together compared to thermal or laser light. Such topological effects, which are unique to bosonic systems, could pave the way for the development of robust quantum photonic devices.

Four-wave mixing of topological edge plasmons in graphene metasurfaces

“…Third, phase-matching is a crucial condition in nonlinear frequency mixing processes. In contrast to the frequently used bulk modes (22), where several modes with different wave vectors usually exist at a given frequency, a topological edge mode has a unique wave vector at a fixed frequency, thus the phase-matching condition is insensitive to the way one excites the system, as in this case only a single mode could be excited at one frequency. These important features make graphene plasmonic systems particularly appealing in the design of highly integrated nonlinear topological nanophotonic devices.…”

Topology and Interactions in the Photonic Creutz and Creutz‐Hubbard Ladders

“…Photonic quantum simulators use the properties of quantum or classical states of light to analyze the behavior of different quantum systems. In the last few years, an increasing collection of topological materials have been studied in photonic setups, both using quantum and classical light . The latter type of simulators are easier to implement but can only simulate first‐quantized dynamics, and thus the realization of systems of interacting particles has been traditionally challenging.…”

Edge states of photon pairs in cavity arrays with spatially modulated nonlinearity

“…The integrated quantum optical platform potentially promises robust scalable quantum simulations on a chip. It is now under active development [3][4][5][6][7][8], although still catches up with the cold atom and superconducting resonator networks [9]. Hence, it is specially instructive to re-examine the conceptual effects of interaction, that can be manifested already for a few interacting particles, and are potentially easier to implement.…”