Optically addressable spins in materials are important platforms for quantum technologies, such as repeaters and sensors. Identification of such systems in two-dimensional (2d) layered materials offers advantages over their bulk counterparts, as their reduced dimensionality enables more feasible on-chip integration into devices. Here, we report room-temperature optically detected magnetic resonance (ODMR) from previously identified carbon-related single defects in 2d hexagonal boron nitride (hBN). We show that single-defect ODMR contrast is up to 100x stronger than that of ensembles and displays a magnetic-field dependence with both positive or negative sign per defect. Further, the ODMR lineshape comprises a doublet resonance, indicating a S=1 state with low but finite zero-field splitting. Our results offer a promising route towards realising a room-temperature spin-photon quantum interface in hexagonal boron nitride.
Optically active semiconductor quantum dots offer high quality spin-photon interfaces for quantum optics applications. This interface can be used to generate distant entanglement between confined spins based on projective measurements. I will review current progress on this topic highlighting the crucial role played by coherent scattering.
Nanodiamonds contain stable fluorescent emitters and hence can be used for molecular fluorescence imaging and precision sensing of electromagnetic fields. The physical properties of these emitters together with their low reported cytotoxicity make them attractive for biological imaging applications. The controlled application of nanodiamonds for cellular imaging requires detailed understanding of surface chemistry, size ranges and aggregation, as these can all influence cellular interactions. We compared these characteristics for graphitic and oxidized nanodiamonds. Oxidation is generally used for surface functionalization, and was optimized by Thermogravimetric Analysis, achieved by 445±5°C heating in air for 5 hours, then confirmed via Raman and Infrared spectroscopies. Size ranges and aggregation were assessed using Atomic Force Microscopy and Dynamic Light Scattering. Biocompatibility in breast cancer cell lines was measured using a proliferation assay. Heating at 445±5°C reduced the Raman signal of graphitic carbon (1575 cm-1) as compared to that of diamond (1332 cm-1) from 0.31±0.07 Raman intensity units to 0.07±0.04. This temperature was substantially below the onset of major mass loss (observed at 535±1°C) and therefore achieved cost efficiency, convenience and high yield. Graphitic and oxidized nanodiamonds formed aggregates in water, with a mean particle size of 192±4nm and 166±2nm at a concentration of 66μg/mL. We then applied the graphitic and oxidized nanodiamonds to cells in culture at 1μg/mL and found no significant change in the proliferation rate (-5±2% and -1±3% respectively). Nanodiamonds may therefore be suitable for development as a novel transformative tool in the life sciences.
We describe the development of a quantum key distribution (QKD)
scheme based on ultrafast laser pumped sources of entangled photon
pairs and the engineering of their entanglement properties. Though
quantum entanglement has been shown to be a useful resource for
quantum key distribution, little work has been carried out in
making use of the full range of joint entanglement behavior present in hyper-entangled photon pairs. We consider the principal advantages of our QKD scheme in connection with the way it makes use of ultrafast laser pumped spontaneous parametric down-conversion and hyper-entanglement. In particular, we consider how polarization quantum interference may be modified by manipulating the spatial features of the down-converted light.
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