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Publications

2017
Bar-Gill, N. & Retzker, A. Observing chemical shifts from nanosamples. Science (Perspective) 357, 6346, 38 (2017). Publisher's Version
2015
Wolf, S.A., Rosenberg, I., Rapaport, R. & Bar-Gill, N. Purcell-enhanced optical spin readout of nitrogen-vacancy centers in diamond. Phys. Rev. B 92, 235410 (2015). Publisher's Version
Farfurnik, D., et al. Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond. Phys. Rev. B 92, 060301 (2015). Publisher's Version
Arai, K., et al. Optical magnetic resonance imaging with nanoscale resolution and compressed sensing speed-up. Nat. Nanotechnol. Advanced online publication, (2015). Publisher's VersionAbstract

Optically detected magnetic resonance using nitrogen-vacancy (NV) colour centres in diamond is a leading modality for nanoscale magnetic field imaging, as it provides single electron spin sensitivity, three-dimensional resolution better than 1 nm (ref. 5) and applicability to a wide range of physical and biological samples under ambient conditions. To date, however, NV-diamond magnetic imaging has been performed using 'real-space' techniques, which are either limited by optical diffraction to ∼250 nm resolution or require slow, point-by-point scanning for nanoscale resolution, for example, using an atomic force microscope, magnetic tip, or super-resolution optical imaging. Here, we introduce an alternative technique of Fourier magnetic imaging using NV-diamond. In analogy with conventional magnetic resonance imaging (MRI), we employ pulsed magnetic field gradients to phase-encode spatial information on NV electronic spins in wavenumber or 'k-space' followed by a fast Fourier transform to yield real-space images with nanoscale resolution, wide field of view and compressed sensing speed-up.

DeVience, S.J., et al. Nanoscale NMR spectroscopy and imaging of multiple nuclear species. Nat. Nanotechnol. 10, 2, 129-134 (2015). Publisher's VersionAbstract

Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) provide non-invasive information about multiple nuclear species in bulk matter, with wide-ranging applications from basic physics and chemistry to biomedical imaging. However, the spatial resolution of conventional NMR and MRI is limited to several micrometres even at large magnetic fields (>1 T), which is inadequate for many frontier scientific applications such as single-molecule NMR spectroscopy and in vivo MRI of individual biological cells. A promising approach for nanoscale NMR and MRI exploits optical measurements of nitrogen–vacancy (NV) colour centres in diamond, which provide a combination of magnetic field sensitivity and nanoscale spatial resolution unmatched by any existing technology, while operating under ambient conditions in a robust, solid-state system. Recently, single, shallow NV centres were used to demonstrate NMR of nanoscale ensembles of proton spins, consisting of a statistical polarization equivalent to ∼100–1,000 spins in uniform samples covering the surface of a bulk diamond chip. Here, we realize nanoscale NMR spectroscopy and MRI of multiple nuclear species (1H, 19F, 31P) in non-uniform (spatially structured) samples under ambient conditions and at moderate magnetic fields (∼20 mT) using two complementary sensor modalities.

Romach, Y., et al. Spectroscopy of surface-induced noise using shallow spins in diamond. Phys. Rev. Lett. 114, 017601 (2015). Publisher's VersionAbstract
We report on the noise spectrum experienced by few nanometer deep nitrogen-vacancy centers in diamond as a function of depth, surface coating, magnetic field and temperature. Analysis reveals a double-Lorentzian noise spectrum consistent with a surface electronic spin bath in the low frequency regime, along with a faster noise source attributed to surface-modified phononic coupling. These results shed new light on the mechanisms responsible for surface noise affecting shallow spins at semiconductor interfaces, and suggests possible directions for further studies. We demonstrate dynamical decoupling from the surface noise, paving the way to applications ranging from nanoscale NMR to quantum networks.
2013
Trifonov, A.S., et al. Limits to resolution of CW STED microscopy. Advances In Atomic, Molecular, and Optical Physics 62, 279-302 (2013).
Belthangady, C., et al. Dressed-State Resonant Coupling between Bright and Dark Spins in Diamond. Physical Review Letters 110, (2013).
Bar-Gill, N., Pham, L., Jarmola, A., Budker, D. & Walsworth, R. Solid-state electronic spin coherence time approaching one second. Nature communications 4, (2013). Publisher's VersionAbstract
Solid-state spin systems such as nitrogen-vacancy colour centres in diamond are promising for applications of quantum information, sensing and metrology. However, a key challenge for such solid-state systems is to realize a spin coherence time that is much longer than the time for quantum spin manipulation protocols. Here we demonstrate an improvement of more than two orders of magnitude in the spin coherence time {(T&\#x2082;)} of nitrogen-vacancy centres compared with previous measurements: T&\#x2082;&\#x2248;0.6 s at 77 K. We employed dynamical decoupling pulse sequences to suppress nitrogen-vacancy spin decoherence, and found that T&\#x2082; is limited to approximately half of the longitudinal spin relaxation time over a wide range of temperatures, which we attribute to phonon-induced decoherence. Our results apply to ensembles of nitrogen-vacancy spins, and thus could advance quantum sensing, enable squeezing and many-body entanglement, and open a path to simulating driven, interaction-dominated quantum many-body Hamiltonians.
2012
Le Sage, D., et al. Efficient photon detection from color centers in a diamond optical waveguide. Physical Review B 85, (2012).
Pham, L., et al. Enhanced metrology using preferential orientation of nitrogen-vacancy centers in diamond. Physical Review B 86, (2012).
Pham, L.M., et al. Enhanced solid-state multispin metrology using dynamical decoupling. Physical Review B 86, (2012).
Bar-Gill, N., et al. Suppression of spin-bath dynamics for improved coherence of multi-spin-qubit systems. Nature communications 3, (2012). Publisher's VersionAbstract
Multi-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.
2011
Bar-Gill, N., Rao, D. & Kurizki, G. Creating nonclassical states of Bose-Einstein condensates by dephasing collisions. Physical review letters 107, (2011).Abstract
We show, using an exactly solvable model, that nonlinear dynamics is induced in a double-well {Bose-Einstein} condensate {(BEC)} by collisions with a thermal reservoir. This dynamics can facilitate the creation of phase or number squeezing and, at longer times, the creation of macroscopic nonclassical superposition states. Enhancement of these effects is possible by loading the reservoir atoms into an optical lattice.
Bar-Gill, N., Gross, C., Mazets, I., Oberthaler, M. & Kurizki, G. Einstein-Podolsky-Rosen correlations of ultracold atomic gases. Physical review letters 106, (2011).Abstract
We demonstrate that collective continuous variables of two species of trapped ultracold bosonic gases can be {Einstein-Podolsky-Rosen-correlated} (entangled) via inherent interactions between the species. We propose two different schemes for creating these correlations–a dynamical scheme and a static scheme analogous to two-mode squeezing in quantum optics. We quantify the correlations by using known measures of entanglement and study the effect of finite temperature on these quantum correlations.
Gross, C., et al. Atomic homodyne detection of continuous-variable entangled twin-atom states. Nature 480, 219-223 (2011). Publisher's VersionAbstract
Historically, the completeness of quantum theory has been questioned using the concept of bipartite continuous-variable entanglement. The non-classical correlations (entanglement) between the two subsystems imply that the observables of one subsystem are determined by the measurement choice on the other, regardless of the distance between the subsystems. Nowadays, continuous-variable entanglement is regarded as an essential resource, allowing for quantum enhanced measurement resolution, the realization of quantum teleportation and quantum memories, or the demonstration of the {Einstein-Podolsky-Rosen} paradox. These applications rely on techniques to manipulate and detect coherences of quantum fields, the quadratures. Whereas in optics coherent homodyne detection of quadratures is a standard technique, for massive particles a corresponding method was missing. Here we report the realization of an atomic analogue to homodyne detection for the measurement of matter-wave quadratures. The application of this technique to a quantum state produced by spin-changing collisions in a {Bose-Einstein} condensate reveals continuous-variable entanglement, as well as the twin-atom character of the state. Our results provide a rare example of continuous-variable entanglement of massive particles. The direct detection of atomic quadratures has applications not only in experimental quantum atom optics, but also for the measurement of fields in many-body systems of massive particles.
Bhaktavatsala Rao, D., Bar-Gill, N. & Kurizki, G. Generation of macroscopic superpositions of quantum states by linear coupling to a bath. Physical review letters 106, (2011).Abstract
We demonstrate through an exactly solvable model that collective coupling to any thermal bath induces effectively nonlinear couplings in a quantum many-body (multispin) system. The resulting evolution can drive an uncorrelated large-spin system with high probability into a macroscopic quantum-superposition state. We discuss possible experimental realizations.
2010
Bar-Gill, N., Kurizki, G., Malomed, B.A. & Sudheesh, C. Dynamical control of nonlinear symmetry breaking under decoherence. Physical Review A 82, (2010).
Sudheesh, C., Bar-Gill, N., Malomed, B.A. & Kurizki, G. Two-dimensional solitons in periodically modulated double-well potentials. Journal of Physics B: Atomic, Molecular and Optical Physics 43, (2010).
2009
Bar-Gill, N., Kurizki, G., Oberthaler, M. & Davidson, N. Dynamic control and probing of many-body decoherence in double-well Bose-Einstein condensates. Physical Review A 80, (2009).

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