Person: Bennett, Steven
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Bennett
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Steven
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Bennett, Steven
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Publication Phonon-Induced Spin-Spin Interactions in Diamond Nanostructures: Application to Spin Squeezing(American Physical Society (APS), 2013) Bennett, Steven; Yao, Norman; Otterbach, Johannes; Zoller, P.; Rabl, P.; Lukin, MikhailWe propose and analyze a novel mechanism for long-range spin-spin interactions in diamond nanostructures. The interactions between electronic spins, associated with nitrogen-vacancy centers in diamond, are mediated by their coupling via strain to the vibrational mode of a diamond mechanical nanoresonator. This coupling results in phonon-mediated effective spin-spin interactions that can be used to generate squeezed states of a spin ensemble. We show that spin dephasing and relaxation can be largely suppressed, allowing for substantial spin squeezing under realistic experimental conditions. Our approach has implications for spin-ensemble magnetometry, as well as phonon-mediated quantum information processing with spin qubits.Publication Phonon cooling and lasing with nitrogen-vacancy centers in diamond(American Physical Society (APS), 2013) Kepesidis, K. V.; Bennett, Steven; Portolan, S.; Lukin, Mikhail; Rabl, P.We investigate the strain-induced coupling between a nitrogen-vacancy impurity and a resonant vibrational mode of a diamond nanoresonator. We show that under near-resonant laser excitation of the electronic states of the impurity, this coupling can modify the state of the resonator and either cool the resonator close to the vibrational ground state or drive it into a large-amplitude coherent state. We derive a semiclassical model to describe both effects and evaluate the stationary state of the resonator mode under various driving conditions. In particular, we find that by exploiting resonant single- and multiphonon transitions between near-degenerate electronic states, the coupling to high-frequency vibrational modes can be significantly enhanced and dominate over the intrinsic mechanical dissipation. Our results show that a single nitrogen-vacancy impurity can provide a versatile tool to manipulate and probe individual phonon modes in nanoscale diamond structures.Publication Single-photon nonlinearities in two-mode optomechanics(American Physical Society, 2013) Komar, Peter; Bennett, Steven; Stannigel, K.; Habraken, S.; Rabl, P.; Zoller, P.; Lukin, MikhailWe present a detailed theoretical analysis of a weakly driven, multimode optomechanical system, in which two optical modes are strongly and near-resonantly coupled to a single mechanical mode via a three-wave mixing interaction. We calculate one- and two-time intensity correlations of the two optical fields and compare them to analogous correlations in atom-cavity systems. Nonclassical photon correlations arise when the optomechanical coupling g exceeds the cavity decay rate κ, and we discuss signatures of one- and two-photon resonances as well as quantum interference. We also find a long-lived correlation that decays slowly with the mechanical decay rate γ, reflecting the heralded preparation of a single-phonon state after detection of a photon. Our results provide insight into the quantum regime of multimode optomechanics, with potential applications for quantum information processing with photons and phonons.Publication Sensing Distant Nuclear Spins with a Single Electron Spin(American Physical Society (APS), 2012) Kolkowitz, S; Unterreithmeier, Quirin; Bennett, Steven; Lukin, MikhailWe experimentally demonstrate the use of a single electronic spin to measure the quantum dynamics of distant individual nuclear spins from within a surrounding spin bath. Our technique exploits coherent control of the electron spin, allowing us to isolate and monitor nuclear spins weakly coupled to the electron spin. Specifically, we detect the evolution of distant individual C13 nuclear spins coupled to single nitrogen vacancy centers in a diamond lattice with hyperfine couplings down to a factor of 8 below the electronic spin bare dephasing rate. Potential applications to nanoscale magnetic resonance imaging and quantum information processing are discussed.Publication Optomechanical Quantum Information Processing with Photons and Phonons(American Physical Society, 2012) Stannigel, K.; Komar, Peter; Habraken, S. J. M.; Bennett, Steven; Lukin, Mikhail; Zoller, P.; Rabl, P.We describe how strong resonant interactions in multimode optomechanical systems can be used to induce controlled nonlinear couplings between single photons and phonons. Combined with linear mapping schemes between photons and phonons, these techniques provide a universal building block for various classical and quantum information processing applications. Our approach is especially suited for nano-optomechanical devices, where strong optomechanical interactions on a single photon level are within experimental reach.Publication Quantum logic between remote quantum registers(American Physical Society (APS), 2013) Yao, Norman; Gong, Z.-X; Laumann, Chris; Bennett, Steven; Duan, L.-M.; Lukin, Mikhail; Jiang, L.; Gorshkov, A.V.We consider two approaches to dark-spin-mediated quantum computing in hybrid solid-state spin architectures. First, we review the notion of eigenmode-mediated unpolarized spin-chain state transfer and extend the analysis to various experimentally relevant imperfections: quenched disorder, dynamical decoherence, and uncompensated long-range coupling. In finite-length chains, the interplay between disorder-induced localization and decoherence yields a natural optimal channel fidelity, which we calculate. Long-range dipolar couplings induce a finite intrinsic lifetime for the mediating eigenmode; extensive numerical simulations of dipolar chains of lengths up to L=12 show remarkably high fidelity despite these decay processes. We further briefly consider the extension of the protocol to bosonic systems of coupled oscillators. Second, we introduce a quantum mirror based architecture for universal quantum computing that exploits all of the dark spins in the system as potential qubits. While this dramatically increases the number of qubits available, the composite operations required to manipulate dark-spin qubits significantly raise the error threshold for robust operation. Finally, we demonstrate that eigenmode-mediated state transfer can enable robust long-range logic between spatially separated nitrogen-vacancy registers in diamond; disorder-averaged numerics confirm that high-fidelity gates are achievable even in the presence of moderate disorder.Publication Phonon-Induced Population Dynamics and Intersystem Crossing in Nitrogen-Vacancy Centers(American Physical Society (APS), 2015) Goldman, Michael Lurie; Sipahigil, Alp; Doherty, M. W.; Yao, Norman; Bennett, Steven; Markham, M.; Twitchen, D. J.; Manson, N. B.; Kubanek, Alexander; Lukin, MikhailWe report direct measurement of population dynamics in the excited state manifold of a nitrogen-vacancy (NV) center in diamond. We quantify the phonon-induced mixing rate and demonstrate that it can be completely suppressed at low temperatures. Further, we measure the intersystem crossing (ISC) rate for different excited states and develop a theoretical model that unifies the phonon-induced mixing and ISC mechanisms. We find that our model is in excellent agreement with experiment and that it can be used to predict unknown elements of the NV center’s electronic structure. We discuss the model’s implications for enhancing the NV center’s performance as a room-temperature sensor.Publication All-Optical Sensing of a Single-Molecule Electron Spin(American Chemical Society (ACS), 2014) Sushkov, Alexander; Chisholm, N.; Lovchinsky, I.; Kubo, M.; Lo, P. K.; Bennett, Steven; Hunger, D.; Akimov, Alexey; Walsworth, Ronald; Park, H.; Lukin, MikhailWe demonstrate an all-optical method for magnetic sensing of individual molecules in ambient conditions at room temperature. Our approach is based on shallow nitrogen-vacancy (NV) centers near the surface of a diamond crystal, which we use to detect single paramagnetic molecules covalently attached to the diamond surface. The manipulation and readout of the NV centers is all-optical and provides a sensitive probe of the magnetic field fluctuations stemming from the dynamics of the electronic spins of the attached molecules. As a specific example, we demonstrate detection of a single paramagnetic molecule containing a gadolinium (Gd3+) ion. We confirm single-molecule resolution using optical fluorescence and atomic force microscopy to colocalize one NV center and one Gd3+-containing molecule. Possible applications include nanoscale and in vivo magnetic spectroscopy and imaging of individual molecules.Publication State-selective intersystem crossing in nitrogen-vacancy centers(American Physical Society (APS), 2015) Goldman, Michael Lurie; Doherty, M. W.; Sipahigil, Alp; Yao, Norman; Bennett, Steven; Manson, N. B.; Kubanek, Alexander; Lukin, MikhailThe intersystem crossing (ISC) is an important process in many solid-state atomlike impurities. For example, it allows the electronic spin state of the nitrogen-vacancy (NV) center in diamond to be initialized and read out using optical fields at ambient temperatures. This capability has enabled a wide array of applications in metrology and quantum information science. Here, we develop a microscopic model of the state-selective ISC from the optical excited state manifold of the NV center. By correlating the electron-phonon interactions that mediate the ISC with those that induce population dynamics within the NV center's excited state manifold and those that produce the phonon sidebands of its optical transitions, we quantitatively demonstrate that our model is consistent with recent ISC measurements. Furthermore, our model constrains the unknown energy spacings between the center's spin-singlet and spin-triplet levels. Finally, we discuss prospects to engineer the ISC in order to improve the spin initialization and readout fidelities of NV centers.