Resonant Semiconductor Metasurfaces for Generating Complex Quantum States

TL;DR

This paper demonstrates how resonant semiconductor metasurfaces can generate complex, frequency-multiplexed quantum states, including cluster states, by enhancing photon pair emission without strict phase-matching constraints.

Contribution

It introduces a novel approach using nonlinear metasurfaces with high-quality resonances to produce complex quantum states beyond traditional phase-matching limitations.

Findings

Enhanced photon pair emission within narrow resonance bands

Generation of entangled photons at multiple wavelengths

Support for photon pair generation from a wide range of pump energies

Abstract

Quantum state engineering, the cornerstone of quantum photonic technologies, mainly relies on spontaneous parametric down-conversion and four-wave mixing, where one or two pump photons decay into a photon pair. Both these nonlinear effects require momentum conservation (i.e., phase-matching) for the participating photons, which strongly limits the versatility of the resulting quantum states. Nonlinear metasurfaces, due to their subwavelength thickness, relax this constraint and extend the boundaries of quantum state engineering. Here, we generate entangled photons via spontaneous parametric down-conversion in semiconductor metasurfaces with high-quality resonances. By enhancing the quantum vacuum field, our metasurfaces boost the emission of photon pairs within narrow resonance bands at multiple selected wavelengths. Due to the relaxed momentum conservation, the same resonances support photon pair generation from pump photons of practically any energy. This enables the generation of complex frequency-multiplexed quantum states, in particular cluster states. Our results demonstrate the multifunctional use of metasurfaces for quantum state engineering.