Ultrafast all-optical switching by single photons

TL;DR

This paper demonstrates ultrafast all-optical switching at the single-photon level using a quantum dot-cavity system, enabling potential applications in high-speed quantum photonic networks.

Contribution

It presents the first demonstration of single-photon switching on a 20 ps timescale in a strongly coupled quantum dot-cavity system, advancing quantum nonlinear optics.

Findings

Single-photon switching achieved in 20 ps

Demonstration of a single-photon pulse-correlator

Potential for high-bandwidth quantum photonic networks

Abstract

An outstanding goal in quantum optics is the realization of fast optical non-linearities at the single-photon level. Such non-linearities would allow for the realization of optical devices with new functionalities such as a single-photon switch/transistor or a controlled-phase gate, which could form the basis of future quantum optical technologies. While non-linear optics effects at the single-emitter level have been demonstrated in different systems, including atoms coupled to Fabry-Perot or toroidal micro-cavities, super-conducting qubits in strip-line resonators or quantum dots (QDs) in nano-cavities, none of these experiments so far has demonstrated single-photon switching on ultrafast timescales. Here, we demonstrate that in a strongly coupled QD-cavity system the presence of a single photon on one of the fundamental polariton transitions can turn on light scattering on a transition from the first to the second Jaynes-Cummings manifold with a switching time of 20 ps. As an additional device application, we use this non-linearity to implement a single-photon pulse-correlator. Our QD-cavity system could form the building-block of future high-bandwidth photonic networks operating in the quantum regime.