Person: Le Sage, David
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Le Sage
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David
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Le Sage, David
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Publication Anti-Reflection Coating for Nitrogen-Vacancy Optical Measurements in Diamond(American Institute of Physics (AIP), 2012) Yeung, T. K.; Le Sage, David; Pham, Linh; Stanwix, P. L.; Walsworth, RonaldWe realize anti-reflection (AR) coatings for optical excitation and fluorescence measurements of nitrogen-vacancy (NV) color centers in bulk diamond by depositing quarter-wavelength thick silica layers on the diamondsurface. These AR coatings improve NV-diamond optical measurements by reducing optical reflection at the diamond-air interface from ≈17% to ≈2%, which allows more effective NV optical excitation and more efficient detection of NV fluorescence. We also show that diamondAR coatings eliminate standing-wave interference patterns of excitation laser intensity within bulk diamond, and thereby greatly reduce spatial variations in NV fluorescence, which can degrade spatially resolved magnetic field sensing using NV centers.Publication Enhanced metrology using preferential orientation of nitrogen-vacancy centers in diamond(American Physical Society (APS), 2012) Pham, Linh; Bar-Gill, N.; Le Sage, David; Belthangady, Chinmay; Stacey, A.; Markham, M.; Twitchen, D. J.; Lukin, Mikhail; Walsworth, RonaldWe demonstrate preferential orientation of nitrogen-vacancy (NV) color centers along two of four possible crystallographic axes in diamonds grown by chemical vapor deposition on the {100} face. We identify the relevant growth regime and present a possible explanation of this effect. We show that preferential orientation provides increased optical readout contrast for NV multispin measurements, including enhanced ac magnetic-field sensitivity, thus providing an important step towards high-fidelity multispin-qubit quantum information processing, sensing, and metrology.Publication Enhanced solid-state multispin metrology using dynamical decoupling(American Physical Society (APS), 2012) Pham, Linh; Bar-Gill, N.; Belthangady, Chinmay; Le Sage, David; Cappellaro, P.; Lukin, Mikhail; Yacoby, Amir; Walsworth, RonaldWe use multipulse dynamical decoupling to increase the coherence lifetime (T2) of large numbers of nitrogen-vacancy (NV) electronic spins in room temperature diamond, thus enabling scalable applications of multispin quantum information processing and metrology. We realize an order-of-magnitude extension of the NV multispin T2 in three diamond samples with widely differing spin impurity environments. In particular, for samples with nitrogen impurity concentration ≲1 ppm, we extend T2 to >2 ms, comparable to the longest coherence time reported for single NV centers, and demonstrate a tenfold enhancement in NV multispin sensing of ac magnetic fields.Publication Suppression of spin-bath dynamics for improved coherence of multi-spin-qubit systems(Springer Nature, 2012) Bar-Gill, N.; Pham, Linh; Belthangady, Chinmay; Le Sage, David; Cappellaro, P.; Maze, J.R.; Lukin, Mikhail; Yacoby, Amir; Walsworth, RonaldMulti-qubit systems are crucial for the advancement and application of quantum science. Such systems require maintaining long coherence times while increasing the number of qubits available for coherent manipulation. For solid-state spin systems, qubit coherence is closely related to fundamental questions of many-body spin dynamics. Here we apply a coherent spectroscopic technique to characterize the dynamics of the composite solid-state spin environment of nitrogen-vacancy colour centres in room temperature diamond. We identify a possible new mechanism in diamond for suppression of electronic spin-bath dynamics in the presence of a nuclear spin bath of sufficient concentration. This suppression enhances the efficacy of dynamical decoupling techniques, resulting in increased coherence times for multi-spin-qubit systems, thus paving the way for applications in quantum information, sensing and metrology.Publication Efficient photon detection from color centers in a diamond optical waveguide(American Physical Society (APS), 2012) Le Sage, David; Pham, Linh; Bar-Gill, N.; Belthangady, Chinmay; Lukin, Mikhail; Yacoby, Amir; Walsworth, RonaldA common limitation of experiments using color centers in diamond is the poor photon collection efficiency of microscope objectives due to refraction at the diamond interface. We present a simple and effective technique to detect a large fraction of photons emitted by color centers within a planar diamond sample by detecting light that is guided to the edges of the diamond via total internal reflection. We describe a prototype device using this “side-collection” technique, which provides a photon collection efficiency ≈47% and a photon detection efficiency ≈39%. We apply the enhanced signal-to-noise ratio gained from side collection to ac magnetometry using ensembles of nitrogen-vacancy (NV) color centers, and demonstrate an ac magnetic field sensitivity ≈100pT/Hz‾‾‾√, limited by added noise in the prototype side-collection device. Technical optimization should allow significant further improvements in photon collection and detection efficiency as well as subpicotesla NV-diamond magnetic field sensitivity using the side-collection technique.Publication Dressed-State Resonant Coupling between Bright and Dark Spins in Diamond(American Physical Society, 2013) Belthangady, Chinmay; Bar-Gill, N.; Pham, Linh; Arai, K.; Le Sage, David; Cappellaro, P.; Walsworth, RonaldUnder ambient conditions, spin impurities in solid-state systems are found in thermally mixed states and are optically “dark”; i.e., the spin states cannot be optically controlled. Nitrogen-vacancy (NV) centers in diamond are an exception in that the electronic spin states are “bright”; i.e., they can be polarized by optical pumping, coherently manipulated with spin-resonance techniques, and read out optically, all at room temperature. Here we demonstrate a scheme to resonantly couple bright NV electronic spins to dark substitutional-nitrogen (P1) electronic spins by dressing their spin states with oscillating magnetic fields. This resonant coupling mechanism can be used to transfer spin polarization from NV spins to nearby dark spins and could be used to cool a mesoscopic bath of dark spins to near-zero temperature, thus providing a resource for quantum information and sensing, and aiding studies of quantum effects in many-body spin systems.Publication A Genetic Strategy for Probing the Functional Diversity of Magnetosome Formation(Public Library of Science, 2015) Rahn-Lee, Lilah; Byrne, Meghan E.; Zhang, Manjing; Le Sage, David; Glenn, David; Milbourne, Timothy; Walsworth, Ronald; Vali, Hojatollah; Komeili, ArashModel genetic systems are invaluable, but limit us to understanding only a few organisms in detail, missing the variations in biological processes that are performed by related organisms. One such diverse process is the formation of magnetosome organelles by magnetotactic bacteria. Studies of model magnetotactic α-proteobacteria have demonstrated that magnetosomes are cubo-octahedral magnetite crystals that are synthesized within pre-existing membrane compartments derived from the inner membrane and orchestrated by a specific set of genes encoded within a genomic island. However, this model cannot explain all magnetosome formation, which is phenotypically and genetically diverse. For example, Desulfovibrio magneticus RS-1, a δ-proteobacterium for which we lack genetic tools, produces tooth-shaped magnetite crystals that may or may not be encased by a membrane with a magnetosome gene island that diverges significantly from those of the α-proteobacteria. To probe the functional diversity of magnetosome formation, we used modern sequencing technology to identify hits in RS-1 mutated with UV or chemical mutagens. We isolated and characterized mutant alleles of 10 magnetosome genes in RS-1, 7 of which are not found in the α-proteobacterial models. These findings have implications for our understanding of magnetosome formation in general and demonstrate the feasibility of applying a modern genetic approach to an organism for which classic genetic tools are not available.Publication Spectroscopy of composite solid-state spin environments for improved metrology with spin ensembles.(2012) Bar-Gill, N.; Pham, L.; Belthangady, Chinmay; Le Sage, David; Cappellaro, P.; Maze, J.; Lukin, Mikhail; Yacoby, Amir; Walsworth, RonaldFor precision coherent measurements with ensembles of quantum spins the relevant Figure-of Merit (FOM) is the product of polarized spin density and coherence lifetime, which is generally limited by the dynamics of the spin environment. Here, we apply a coherent spectroscopic technique to characterize the dynamics of the composite solid-state spin environment of Nitrogen-Vacancy (NV) centers in room temperature diamond. For samples of very different NV densities and impurity spin concentrations, we show that NV FOM values can be almost an order of magnitude larger than previously achieved in other room-temperature solid-state spin systems, and within an order of magnitude of the state-of-the-art atomic system. We also identify a new mechanism for suppression of electronic spin bath dynamics in the presence of a nuclear spin bath of sufficient concentration. This suppression could inform efforts to further increase the FOM for solid-state spin ensemble metrology and collective quantum information processing.Publication Coherence of Nitrogen-Vacancy Electronic Spin Ensembles in Diamond(American Physical Society, 2010) Stanwix, Paul L.; Pham, Linh; Maze, Jeronimo R.; Le Sage, David; Yeung, Tsun Kwan; Cappellaro, Paola; Hemmer, Philip R.; Yacoby, Amir; Lukin, Mikhail; Walsworth, RonaldWe present an experimental and theoretical study of electronic spin decoherence in ensembles of nitrogen-vacancy (NV) color centers in bulk high-purity diamond at room temperature. Under appropriate conditions, we find ensemble NV spin coherence times (\(T_2\)) comparable to that of single NV with \(T_2>600 \mu s\) for a sample with natural abundance of \(^{13}\)C and paramagnetic impurity density ∼1015 cm\(^{−3}\). We also observe a sharp decrease in the coherence time with misalignment of the static magnetic field relative to the NV electronic spin axis, consistent with theoretical modeling of NV coupling to a \(^{13}\)C nuclear-spin bath. The long coherence times and increased signal-to-noise provided by room-temperature NV ensembles will aid many applications of NV centers in precision magnetometry and quantum information.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.