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ACS Nano ; 2020 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-32697571


Nanostructured systems that combine optical and spin transitions offer new functionalities for quantum technologies by providing efficient quantum light-matter interfaces. Rare earth (RE) ions 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. In this work, we demonstrate that a post-treatment process that includes multi-step high temperature annealing followed by high-power microwave oxygen plasma processing advantageously improves key properties for quantum technologies. We obtain single crystalline Eu3+:Y2O3 nanoparticles (NPs) of 100 nm diameter, presenting bulk-like inhomogeneous linewidths (Γinh) and population lifetimes (T1). Furthermore, a significant coherence lifetime (T2) extension, up to a factor of 5, is successfully achieved by modifying the oxygen-related point defects in the NPs by the oxygen plasma treatment. These promising results confirm the potential of these engineered RE NPs to integrate devices such as cavity-based single photon sources, quantum memories and processors. In addition, our strategy could be applied to a large variety of oxides to obtain outstanding crystalline quality NPs for a broad range of applications.

Phys Rev Lett ; 122(19): 190503, 2019 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-31144926


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. We also show that the coherence time of the nuclear spin (6 ms) is limited by the electron spin-lattice relaxation due to the hyperfine coupling to the electron spin. This Letter paves the way toward realization of building blocks of quantum hardware with an efficient spin-photon interface based on the SiV color center coupled to a long lasting nuclear memory.

Sci Rep ; 8(1): 3342, 2018 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-29463823


We report on optimisation of the environmental stability and high temperature operation of surface transfer doping in hydrogen-terminated diamond using MoO3 and V2O5 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. Exposure of MoO3 and V2O5 transfer-doped hydrogen-terminated diamond samples up to a temperature of 300 °C in ambient air showed significant and irreversible loss in surface conductivity. Thermal stability was found to improve dramatically however when similar thermal treatment was performed in vacuum or in ambient air when the oxide layers were encapsulated with a protective layer of hydrogen silsesquioxane (HSQ). Inspection of the films by X-ray diffraction revealed greater crystallisation of the MoO3 layers following thermal treatment in ambient air compared to the V2O5 films which appeared to remain amorphous. These results suggest that proper encapsulation and passivation of these oxide materials as surface acceptor layers on hydrogen-terminated diamond is essential to maximise their environmental and thermal stability.

Adv Mater ; 29(16)2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28218441


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.