Point-like defects in wide-bandgap materials are at the heart of a broad range of emerging applications including quantum information processing and metrology . A well-known example is the nitrogen-vacancy (NV) defect in diamond, which can be used as a solid-state qubit to perform elaborate quantum information protocols  and highly sensitive magnetic field sensing . These results motivate the search of new defects in other wide-bandgap materials, which would offer an expanded range of functionalities compared to NV defects in diamond.
In that context, hexagonal boron nitride (hBN) appears as an appealing material. First, it has a 6-eV bandgap, which is ideally suited to host optically active defects with energy levels deeply buried between the valence band and the conduction band. Second, hBN is an electrical insulator with a two-dimensional (2D) honeycomb structure, which is a key element of Van der Waals heterostructures. Such “artificial” materials are currently attracting a great interest owing to their unique mechanical, electrical and optical properties . Combining these properties with individual quantum systems would likely open new perspectives in quantum technologies.
In this talk, I will report on the optical detection of individual defects hosted in a high-purity hBN crystal. Stable single photon emission is demonstrated under ambient conditions by means of photon correlation measurements . A detailed analysis of the photophysical properties of the defect reveals a highly efficient radiative transition, leading to one of the brightest single photon source reported to date from a bulk, unpatterned, material. These results make a bridge between the physics of 2D materials and quantum technologies, and pave the way towards applications of van der Waals heterostructures in photonic-based quantum information science, metrology and optoelectronics.
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 B. Hensen et al., Nature 526, 682-686 (2015).
 J.-P. Tetienne, T. Hingant, J.-F. Roch, P. Maletinsky, and V. Jacques, Rep. Prog. Phys. 77, 056503 (2014).
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 L. J. Martinez, T. Pelini, V. Waselowski, J. R. Maze, B. Gil, G. Cassabois, and V. Jacques, preprint arXiv:1606.04124.
The ability to sense nanotelsa magnetic fields with nanoscale spatial resolution is an outstanding technical
challenge relevant to the physical and biological sciences. For example, detection of such weak localized fields
will enable sensing of magnetic resonance signals from individual electron or nuclear spins in complex biological
molecules and the readout of classical or quantum bits of information encoded in an electron or nuclear spin
memory. Here we present a novel approach to nanoscale magnetic sensing based on coherent control of an
individual electronic spin contained in the Nitrogen-Vacancy (NV) center in diamond. At room temperature,
using an ultra-pure diamond sample, we achieve shot-noise-limited detection of 3 nanotesla magnetic fields
oscillating at kHz frequencies after 100 seconds of signal averaging. Furthermore, we experimentally demonstrate
nanoscale resolution using a diamond nanocrystal of 30 nm diameter for which we achieve a sensitivity of 0.5
microtesla / Hz<sup>1/2</sup>.