A Frequency-Multiplexed Coherent Electro-optic Memory in Rare Earth Doped Nanoparticles.

Quantum memories for light are essential components in quantum technologies like long-distance quantum communication and distributed quantum computing. Recent studies have shown that long optical and spin coherence lifetimes can be observed in rare earth doped nanoparticles, opening exciting possibilities over bulk materials, e.g.

Fast electrical modulation of strong near-field interactions between erbium emitters and graphene.

Combining the quantum optical properties of single-photon emitters with the strong near-field interactions available in nanophotonic and plasmonic systems is a powerful way of creating quantum manipulation and metrological functionalities. The ability to actively and dynamically modulate emitter-environment interactions is of particular interest in this regard. While thermal, mechanical and optical modulation have been demonstrated, electrical modulation has remained an outstanding challenge.

Defect Engineering for Quantum Grade Rare-Earth Nanocrystals.

Nanostructured systems that combine optical and spin transitions offer new functionalities for quantum technologies by providing efficient quantum light-matter interfaces. Rare-earth (RE) ion-doped nanoparticles are promising in this field as they show long-lived optical and spin quantum states. However, further development of their use in highly demanding applications, such as scalable single-ion-based quantum processors, requires controlling defects that currently limit coherence lifetimes.

Initialization and Readout of Nuclear Spins via a Negatively Charged Silicon-Vacancy Center in Diamond.

In this Letter, we demonstrate initialization and readout of nuclear spins via a negatively charged silicon-vacancy (SiV) electron spin qubit. Under Hartmann-Hahn conditions the electron spin polarization is coherently transferred to the nuclear spin. The readout of the nuclear polarization is observed via the fluorescence of the SiV.

Controlled size reduction of rare earth doped nanoparticles for optical quantum technologies.

Rare earth doped nanoparticles with sub-wavelength size can be coupled to optical micro- or nano-cavities to enable efficient single ion readout and control, a key requirement for quantum processors and high-fidelity single-ion quantum memories. However, producing small nanoparticles with good dispersion and exploitable optical coherence properties, another key aspect for these applications, is highly challenging by most synthesis and nano-fabrication methods. We report here on the wet chemical etching of Eu:YO nanoparticles and demonstrate that a controlled size reduction down to 150 nm, well below the wavelength of interest, 580 nm, can be achieved.

Thermally Stable, High Performance Transfer Doping of Diamond using Transition Metal Oxides.

We report on optimisation of the environmental stability and high temperature operation of surface transfer doping in hydrogen-terminated diamond using MoO and VO surface acceptor layers. In-situ annealing of the hydrogenated diamond surface at 400 °C was found to be crucial to enhance long-term doping stability. High temperature sheet resistance measurements up to 300 °C were performed to examine doping thermal stability.

Reduction of Dislocations in Single Crystal Diamond by Lateral Growth over a Macroscopic Hole.

A low-dislocation diamond is obtained by homoepitaxial chemical vapor deposition on a standard moderate-quality substrate hollowed out by a large square hole. Dislocations are found to propagate vertically and horizontally from the substrate and to terminate at the top surface or at the sides of the hole, thus leaving the central part with a strongly reduced dislocation density.