Optically Coherent Nitrogen-Vacancy Defect Centers in Diamond Nanostructures

Optically active solid-state spin defects have the potential to become a versatile resource for quantum information processing applications. Nitrogen-vacancy defect centers (NV) in diamond act as quantum memories and can be interfaced with coherent photons as demonstrated in entanglement protocols. However, particularly in diamond nanostructures, the effect of spectral diffusion leads to optical decoherence hindering entanglement generation. In this work, we present strategies to significantly reduce the electric noise in diamond nanostructures. We demonstrate single NVs in nanopillars exhibiting a lifetime-limited linewidth on a timescale of one second and long-term spectral stability with an inhomogeneous linewidth as low as 150 MHz over three minutes. Excitation power and energy-dependent measurements in combination with nanoscopic Monte Carlo simulations contribute to a better understanding of the impact of bulk and surface defects on the NV’s spectral properties. Finally, we propose an entanglement protocol for nanostructure-coupled NVs providing entanglement generation rates up to hundreds of kHz.Peer Reviewe

Elephant crop-raiding and human-elephant conflict in Cambodia: crop selection and seasonal timings of raids

Elephants are threatened globally by habitat loss, poaching and accelerating levels of human-elephant conflict. For Elephas maximus in Cambodia, crop raiding underlies this conflict. Understanding the timing of raids and selection of crops can help design locally appropriate mitigation and management strategies. This study, using a 4-year database of events, investigated the most frequently raided crops and patterns of raids, over time and seasons and by location. Damage frequency varied significantly by crop, with rice, banana, cassava, sugar cane and papaya most frequently raided. Considering raid events per unit crop area, banana, sugar cane and pineapple were raided more than would be expected based on their availability. There were differences in both crop-raiding events and crop-damage frequencies over study years and there was a peak raiding season in October-December. Nationally, significant differences were found among provinces but not between years. Rates of damage decreased after mitigation strategies such as observation towers, deterrents and fences were implemented. We suggest further mechanisms to improve human-elephant conflict monitoring in relation to crop choice and availability