Browsing by Author "Coto, Raul"

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    First-Principles Identification of Single Photon Emitters Based on Carbon Clusters in Hexagonal Boron Nitride
    (2021) Jara, Cesar; Rauch, Tomas; Botti, Silvana; Marques, Miguel A. L.; Norambuena, Ariel; Coto, Raul; Castellanos-Aguila, J. E.; Maze, Jeronimo R.; Munoz, Francisco
    A recent study associates carbon with single photon emitters (SPEs) in hexagonal boron nitride (h-BN). This observation, together with the high mobility of carbon in h-BN, suggests the existence of SPEs based on carbon clusters. Here, by means of density functional theory calculations, we studied clusters of substitutional carbon atoms up to tetramers in h-BN. Two different conformations of neutral carbon trimers have zero-point line energies and shifts of the phonon sideband compatible with typical photoluminescence spectra. Moreover, some conformations of two small C clusters next to each other result in photoluminescence spectra similar to those found in the experiments. We also showed that vacancies are unable to reproduce the typical features of the phonon sideband observed in most measurements because of the large spectral weight of low-energy breathing modes, ubiquitous in such defects.
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    Probabilistic magnetometry with a two-spin system in diamond
    (2021) Coto, Raul; Dinani, Hossein T.; Norambuena, Ariel; Chen, Mo; Maze, Jeronimo R.
    Solid-state magnetometers like the nitrogen-vacancy (NV) center in diamond have been of paramount importance for the development of quantum sensing with nanoscale spatial resolution. The underlying protocol is a Ramsey sequence, that imprints an external static magnetic field into the phase of the quantum sensor, which is subsequently read out. In this theoretical work we propose a sensing scheme that harnesses the hyperfine coupling between the NV center and a nearby nuclear spin to set a post-selection protocol. We show that concentrating valuable sensing information into a single successful measurement yields an improvement in sensitivity over Ramsey in the range of short transverse relaxation times. By considering realistic experimental conditions, we found that the detection of weak magnetic fields in the mu T range can be achieved with a sensitivity of few tens of nTHz(-1/2) at cryogenic temperature (4 K), and mu THz(-1/2) at room temperature.