Claudio Polisseni | Searcharxiv

arXiv2016

Quantum dynamics of a driven two-level molecule with variable dephasing

The longitudinal ($Γ_1$) and transverse ($Γ_2$) decay rates of a two-level quantum system have profound influence on its evolution. Atomic systems with $Γ_2=\tfrac{1}{2}Γ_1$ have been studied extensively, but with the rise of solid-state quantum devices it is also important to consider the effect of stronger transverse relaxation due to interactions with the solid environment. Here we study the quantum dynamics of a single organic dye molecule driven by a laser. We measure the variation of $Γ_2$ with temperature and determine the activation energy for thermal dephasing of the optical dipole. Then we measure the second-order correlation function $g^{(2)}(τ)$ of the light emitted by the molecule for various ratios $Γ_2/Γ_1$ and saturation parameters $S$. We show that the general solution to the optical Bloch equations accurately describes the observed quantum dynamics over a wide range of these parameters, and we discuss the limitations of the various approximate expressions for $g^{(2)}(τ)$ that appear in the literature.

quant-ph↗

arXiv2016

A stable, single-photon emitter in a thin organic crystal for application to quantum-photonic devices

Single organic molecules offer great promise as bright, reliable sources of identical single photons on demand, capable of integration into solid-state devices. It has been proposed that such molecules in a crystalline organic matrix might be placed close to an optical waveguide for this purpose, but so far there have been no demonstrations of sufficiently thin crystals, with a controlled concentration of suitable dopant molecules. Here we present a method for growing very thin anthracene crystals from super-saturated vapour, which produces crystals of extreme flatness and controlled thickness. We show how this crystal can be doped with a widely adjustable concentration of dibenzoterrylene (DBT) molecules and we examine the optical properties of these molecules to demonstrate their suitability as quantum emitters in nanophotonic devices. Our measurements show that the molecules are available in the crystal as single quantum emitters, with a well-defined polarisation relative to the crystal axes, making them amenable to alignment with optical nanostructures. We find that the radiative lifetime and saturation intensity vary little within the crystal and are not in any way compromised by the unusual matrix environment. We show that a large fraction of these emitters are able to deliver more than $10^{12}$ photons without photo-bleaching, making them suitable for real applications.

quant-ph↗