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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