Person: Trifonov, Alexei
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Trifonov
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Alexei
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Trifonov, Alexei
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Publication Limits to Resolution of CW STED Microscopy(Academic Press (Elsevier BV), 2013) Trifonov, Alexei; Jaskula, Jean-Christophe; Teulon, Claire; Glenn, David; Bar-Gill, Nir; Walsworth, RonaldWe report a systematic theoretical and experimental study of the limits to spatial resolution for stimulated emission depletion (STED) superresolution fluorescence microscopy using continuous wave (CW) laser beams. We develop a theoretical framework for CW STED imaging from point fluorescent emitters and calculate the dependence of 2D spatial resolution on the power of the CW excitation (pump) beam, as well as the power, contrast, and polarization of the CW STED “doughnut” beam. We perform CW STED experiments on (non-bleaching) nitrogen vacancy (NV) color centers in diamond and find good agreement with the theoretical expressions for CW STED spatial resolution. Our results will aid the optimization and application of CW STED microscopy in both the physical and life sciences.Publication Quantum entanglement between an optical photon and a solid-state spin qubit(Nature Publishing Group, 2010) Togan, E; Chu, Y.; Trifonov, Alexei; Jiang, L.; Maze, J.; Childress, Lilian I.; Dutt, M; Sørensen, A. S.; Hemmer, Philip; Zibrov, Alexander; Lukin, MikhailQuantum entanglement is among the most fascinating aspects of quantum theory1. Entangled optical photons are now widely used for fundamental tests of quantum mechanics2 and applications such as quantum cryptography1. Several recent experiments demonstrated entanglement of optical photons with trapped ions3, atoms4, 5 and atomic ensembles6, 7, 8, which are then used to connect remote long-term memory nodes in distributed quantum networks9, 10, 11. Here we realize quantum entanglement between the polarization of a single optical photon and a solid-state qubit associated with the single electronic spin of a nitrogen vacancy centre in diamond. Our experimental entanglement verification uses the quantum eraser technique5, 12, and demonstrates that a high degree of control over interactions between a solid-state qubit and the quantum light field can be achieved. The reported entanglement source can be used in studies of fundamental quantum phenomena and provides a key building block for the solid-state realization of quantum optical networks13, 14.Publication Correlative light and electron microscopy using cathodoluminescence from nanoparticles with distinguishable colours(Nature Publishing Group, 2012) Glenn, David; Zhang, Huidan; Kasthuri, Narayanan; Schalek, Richard; Lo, P. K.; Trifonov, Alexei; Park, Hongkun; Lichtman, Jeff; Walsworth, RonaldCorrelative light and electron microscopy promises to combine molecular specificity with nanoscale imaging resolution. However, there are substantial technical challenges including reliable co-registration of optical and electron images, and rapid optical signal degradation under electron beam irradiation. Here, we introduce a new approach to solve these problems: imaging of stable optical cathodoluminescence emitted in a scanning electron microscope by nanoparticles with controllable surface chemistry. We demonstrate well-correlated cathodoluminescence and secondary electron images using three species of semiconductor nanoparticles that contain defects providing stable, spectrally-distinguishable cathodoluminescence. We also demonstrate reliable surface functionalization of the particles. The results pave the way for the use of such nanoparticles for targeted labeling of surfaces to provide nanoscale mapping of molecular composition, indicated by cathodoluminescence colour, simultaneously acquired with structural electron images in a single instrument.Publication Magnetic Field Imaging with Nitrogen-Vacancy Ensembles(Institute of Physics, 2011) Pham, Linh; Le Sage, David; Stanwix, Paul L.; Yeung, Tsun Kwan; Glenn, David; Trifonov, Alexei; Cappellaro, Paola; Hemmer, Philip; Lukin, Mikhail; Park, Hongkun; Yacoby, Amir; Walsworth, RonaldWe demonstrate a method of imaging spatially varying magnetic fields using a thin layer of nitrogen-vacancy (NV) centers at the surface of a diamond chip. Fluorescence emitted by the two-dimensional NV ensemble is detected by a CCD array, from which a vector magnetic field pattern is reconstructed. As a demonstration, ac current is passed through wires placed on the diamond chip surface, and the resulting ac magnetic field patterns are imaged using an echo-based technique with sub-micron resolution over a \(140 \mu m\) x \(140 \mu m\) field of view, giving single-pixel sensitivity \(\sim 100 nT / \sqrt{Hz}\). We discuss ongoing efforts to further improve the sensitivity, as well as potential bioimaging applications such as real-time imaging of activity in functional, cultured networks of neurons.Publication Properties of Nitrogen-Vacancy Centers in Diamond: The Group Theoretic Approach(Institute of Physics, 2011) Maze, Jeronimo R.; Gali, Adam; Togan, Emre; Chu, Yiwen; Trifonov, Alexei; Kaxiras, Efthimios; Lukin, MikhailWe present a procedure that makes use of group theory to analyze and predict the main properties of the negatively charged nitrogen-vacancy (NV) center in diamond. We focus on the relatively low temperature limit where both the spin–spin and spin–orbit effects are important to consider. We demonstrate that group theory may be used to clarify several aspects of the NV structure, such as ordering of the singlets in the \((e^2)\) electronic configuration and the spin–spin and spin–orbit interactions in the \((ae)\) electronic configuration. We also discuss how the optical selection rules and the response of the center to electric field can be used for spin–photon entanglement schemes. Our general formalism is applicable to a broad class of local defects in solids. The present results have important implications for applications in quantum information science and nanomagnetometry.