Nonlinear quantum electrodynamics of epsilon-near-zero nanostructures

The authors demonstrate here the nonlinear optical response of epsilon-near-zero (ENZ) nanostructures at the single-photon level using fully nonperturbative quantum theory of open systems with indium tin oxide materials and Kerr-type nonlinearity. Closed-form analytical results obtained for spherical nanoparticles are numerically validated and extended to geometries that can be fabricated using state-of-the-art electron-beam lithography, establishing a rigorous benchmark for understanding quantum nonlinear effects in ENZ nanostructures with optical losses. These results are important to emerging quantum technology, including on-chip single-photon nondemolition detection, sensing, and spectroscopy.