The silicon-vacancy (SiV) color center in diamond is a solid-state single photon emitter and spin quantum bit suited as a component in quantum devices. Here, we show that the SiV center in nanodiamond exhibits a strongly inhomogeneous distribution with regard to the center wavelengths and linewidths of the zero-phonon-line (ZPL) emission at room temperature. We find that the SiV centers separate in two clusters: one group exhibits ZPLs with center wavelengths within a narrow range of approximatly 730 nm to 742 nm and broad linewidths between 5 nm and 17 nm, whereas the second group comprises a very broad distribution of center wavelengths between 715 nm and 835 nm, but narrow linewidths from below 1 nm up to 4 nm. Supported by ab initio Kohn-Sham density functional theory calculations we show that the ZPL shifts of the first group are consistently explained by strain in the diamond lattice. Further, we suggest, that the second group showing the strongly inhomogeneous distribution of center wavelengths might be comprised of modified SiV centers. Whereas single photon emission is demonstrated for SiV centers of both clusters, we show that emitters from different clusters show different spectroscopic features such as variations of the phonon sideband spectra and different blinking dynamics.

The present Photonic era is based on rapidly developing optical technology and photon devices, with special impact on the fields of quantum communication, quantum computing, quantum enhanced measurements beyond the standard quantum limit, and optical radiometry. These applications require quantum optical metrology based on new standards and calibration chains, together with new metrics. In particular, standards are required which operate in the single-photon regime and are embedded in quantum optical technologies. Moreover, quantum enhanced optical measurements e.g. the exploitation of quantum phenomena such as entanglement and other non-classical state correlations, are among the challenges to yield sensitivity and accuracy better than purely classical approaches. The goal is to develop theoretical and technological capabilities for operating optical systems (e.g. sub-shot noise imaging, ghost imaging, phase measurement) or opto-mechanical systems (micro-cavities), in the quantum regime, beyond the Standard Quantum Limit. A single-emitter sub-shot noise quantum light source: press a button and get one photon Author and Speaker: Stephan Götzinger, Max Planck Institute for Light, Germany Speaker email: stephan.goetzinger(at)mpl.mpg.de Abstract: In this talk I will discuss our recent progress towards a deterministic single-photon source. By embedding a single molecule into a metallo-dielectric antenna we obtained the most regulated stream of single photons reported to date. Such a source might have potential applications in the calibration of photodetectors and could lead to the redefinition of the candela. In this talk I will discuss our recent progress towards a deterministic single-photon source. By embedding a single molecule into a metallo-dielectric antenna we obtained the most regulated stream of single photons reported to date. Such a source might have potential applications in the calibration of photodetectors and could lead to the redefinition of the candela. Quantum imaging: challenges and perspectives in radiometry and biophotonics Author and Speaker: Ivano Ruo-Berchera, INRIM, Italy Speaker email: i.ruoberchera(at)inrim.it Abstract: Non-classical correlations in optical beams offer unprecedented opportunity of reducing the uncertainty of measurements especially when a low photon flux, down to the single photon level, is used. We review the principles and the state-of-the-art of quantum imaging and sensing techniques with emphasis on the applications to radiometry and biophotonics. In particular, non-classical correlations could represent a cutting-edge tool for investigating phototransduction processes at the fundamental level, such as the one responsible of human vision. Non-classical correlations in optical beams offer unprecedented opportunity of reducing the uncertainty of measurements especially when a low photon flux, down to the single photon level, is used. We review the principles and the state-of-the-art of quantum imaging and sensing techniques with emphasis on the applications to radiometry and biophotonics. In particular, non-classical correlations could represent a cutting-edge tool for investigating phototransduction processes at the fundamental level, such as the one responsible of human vision.

Kück, S.; López, M.; Rodiek, B.; Hofer, H.; Porrovecchio, G.; Šmid, M.; Brida, G.; Traina, P.; Degiovanni, I. P.; Pokatilov, A.; Kübarsepp, T.; Manninen, A.; Vaigu, A.; Chunnilall, C.; Szwer, D.; Polyakov, S.; Claudon, J.; Gregersen, Niels; Mørk, Jesper; Chu, X-L.; Götzinger, S. ; Lindner, S. ; Bock, M.; Becher, C.; Reitzenstein, S. Published in: Proceedings of 13th International Conference on New Developments and Applications in Optical Radiometry

We present a predictable single-photon source (SPS) based on a silicon vacancy centre in nanodiamond which is optically excited by a pulsed laser. At an excitation rate of 70 MHz the source delivers a photon flux large enough to be measured by a low optical flux detector (LOFD). The directly measured photon flux constitutes an absolute reference. By changing the repetition rate of the pulsed laser, we are able to change the photon flux of our SPS in a controllable way which in turn can act as a reference. The advantage of our method is that it does not require precise knowledge of the source efficiency, but the source is calibrated by the LOFD and can be used for detector responsivity characterizations at the few-photon level.

We report on the experimental realization of an absolute single-photon source based on a single nitrogen vacancy (NV) center in a nanodiamond at room temperature and on the calculation of its absolute spectral photon flux from experimental data. The single-photon source was calibrated with respect to its photon flux and its spectral photon rate density. The photon flux was measured with a low-noise silicon photodiode traceable to the primary standard for optical flux, taking into account the absolute spectral power distribution using a calibrated spectroradiometer. The optical radiant flux is adjustable from 55 fW, which is almost the lowest detection limit for the silicon photodiode, and 75 fW, which is the saturation power of the NV center. These fluxes correspond to total photon flux rates between 190,000 photons per second and 260,000 photons per second, respectively. The single-photon emission purity is indicated by a g((2))(0) value, which is between 0.10 and 0.23, depending on the excitation power. To our knowledge, this is the first single-photon source absolutely calibrated with respect to its absolute optical radiant flux and spectral power distribution, traceable to the corresponding national standards via an unbroken traceability chain. The prospects for its application, e.g., for the detection efficiency calibration of single-photon detectors as well as for use as a standard photon source in the low photon flux regime, are promising. (C) 2017 Optical Society of America