Two-Photon Blockade in an Atom-Driven Cavity QED System

TL;DR

This paper demonstrates two-photon blockade in a cavity QED system by driving the atom, leading to enhanced nonlinearity and observable multi-photon quantum effects, advancing multi-photon quantum optics.

Contribution

It shows that atom-driven excitation in cavity QED significantly enhances nonlinearity, enabling two-photon blockade and multi-photon quantum effects.

Findings

Observation of three-photon antibunching

Simultaneous two-photon bunching in emitted light

Enhanced nonlinearity from atom-driven excitation

Abstract

Photon blockade is a dynamical quantum-nonlinear effect that occurs in driven systems with an anharmonic excitation ladder. For a single atom strongly coupled to an optical cavity, we show that driving the atom gives a decisively larger optical nonlinearity than driving the cavity. This enhances single-photon blockade and allows for the implementation of two-photon blockade where the absorption of two photons suppresses the absorption of further photons. As a signature, we report on three-photon antibunching with simultaneous two-photon bunching observed in the light emitted from the cavity. Our experiment constitutes a significant step towards multi-photon quantum-nonlinear optics.