Enhanced Two-Photon Absorption Using Entangled States and Small Mode Volumes

TL;DR

This paper demonstrates that frequency-entangled photons in a tapered optical fiber with a small mode volume significantly enhance two-photon absorption rates, comparable to microcavity systems, due to field confinement and resonance effects.

Contribution

It introduces a method to enhance two-photon absorption using entangled photons in tapered fibers, combining field confinement with resonance to achieve high absorption rates.

Findings

Two-photon absorption rate is significantly increased in tapered fibers.

Resonance with atomic states enhances absorption despite broad photon linewidths.

Entangled photons in small mode volumes match microcavity absorption efficiencies.

Abstract

We calculate the rate of two-photon absorption for frequency entangled photons in a tapered optical fiber whose diameter is comparable to the wavelength of the light. The confinement of the electric field in the transverse direction increases the intensity associated with a single photon, while the two-photon absorption rate is further enhanced by the fact that the sum of the frequencies of the two photons is on resonance with the upper atomic state, even though each photon has a relatively broad linewidth. As a result, the photons are effectively confined in all three dimensions and the two-photon absorption rate for frequency-entangled photons in a tapered fiber was found to be comparable to that for unentangled photons in a microcavity with a small mode volume.