Coherent metamaterial absorption of two-photon states with 40% efficiency

TL;DR

This paper demonstrates a metasurface-based system that achieves nearly maximum two-photon absorption efficiency using N=2 N00N states, advancing quantum nonlinear device capabilities at the single-photon level.

Contribution

It introduces a novel method of enhancing two-photon absorption efficiency through coherent absorption of N=2 N00N states in a metasurface within an interferometer.

Findings

Achieved 40.5% two-photon absorption efficiency.

Demonstrated near-theoretical maximum absorption with quantum states.

Potential applications in multi-photon upconversion technologies.

Abstract

Multi-photon absorption processes have a nonlinear dependence on the amplitude of the incident optical field i.e. the number of photons. However, multi-photon absorption is generally weak and multi-photon events occur with extremely low probability. Consequently, it is extremely challenging to engineer quantum nonlinear devices that operate at the single photon level and the majority of quantum technologies have to rely on single photon interactions. Here, we demonstrate experimentally and theoretically that exploiting coherent absorption of N = 2 N00N states makes it possible to enhance the number of two-photon states that are absorbed. An absorbing metasurface placed inside a Sagnac-style interferometer into which we inject an N = 2 N00N state, exhibits two-photon absorption with 40.5% efficiency, close to the theoretical maximum. This high probability of simultaneous absorption of two photons holds the promise for applications in fields that require multi-photon upconversion but are hindered by high peak intensities.