Best articles

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“Time-integrated qubit measurements using digital memories”, H. Jayakumar, C.A. Meriles, submitted.

We introduce an alternative path to spin qubit detection comprising spin-to-charge conversion and long-term storage of the emitted carriers via ancillary charge traps. This strategy allows one to replace the numerous individual spin readouts — exceeding hundreds of thousands in a normal measurement — by a single collective inspection of the trap ensemble upon repeating the control protocol a pre-defined number of times. Our results pave the route toward enhanced forms of color-center-based metrology down to the limit of individual point defects, while opening intriguing opportunities for on-chip, carrier-based transport of information between distant spin qubits.


“Scalable microcavity-coupled quantum emitters in 2D hexagonal boron nitride”, N.V. Proscia, H. Jayakumar, X. Ge, G.l. Lopez-Morales, Z. Shotan, W. Zhou, C.A. Meriles, V.M. Menon, submitted.  Available as  arxiv:1906.06546

We demonstrate “pick and place” integration of a Si3N4 microdisk optical resonator with a single-photon-emitter (SPE) host in the form of ~20-nm-thick hexagonal boron nitride (hBN). The film folds around the microdisk maximizing contact to ultimately form a composite hBN/Si3N4 structure. The local strain that develops in the hBN film at the resonator circumference deterministically activates a low density of SPEs within the whispering gallery mode volume of the microdisk. These conditions allow us to demonstrate cavity-mediated excitation and incipient coupling of hBN color centers to the microdisk cavity modes.


“Mechanical rotation via optical pumping of paramagnetic impurities”, P.R. Zangara, A. Wood, M.W. Doherty, C.A. Meriles, submitted.

We examine the dynamics of NV-P1 spin pairs under under continuous optical excitation , and theoretically show that cross-relaxation between the NV and P1 spins must induce rigid rotation of the diamond crystal. Further, we find that physical rotation introduces a distance-independent coupling between remote spin pairs, which can ultimately lead to entanglement between otherwise non-interacting NV-P1 pairs.


13C dynamic nuclear polarization in diamond via a microwave-free ‘integrated’ cross effect”, J. Henshaw, D. Pagliero, P.R. Zangara, B. Franzoni, A. Ajoy, R. Acosta, J.A. Reimer, A. Pines, C.A. Meriles, submitted.

We demonstrate efficient microwave-free 13C DNP via consecutive magnetic field sweeps and continuous optical excitation. By comparing the 13C DNP response for different crystal orientations, we show that the process is robust to magnetic field/NV misalignment, a feature that makes the present technique suitable to diamond powders and settings where the field is heterogeneous. Applications to shallow NVs could capitalize on the greater physical proximity between surface paramagnetic defects and outer nuclei to efficiently polarize target samples in contact with the diamond crystal.


“Two-electron-spin ratchets as a platform for microwave-free dynamic nuclear polarization of arbitrary material targets”, P.R. Zangara, J. Henshaw, D. Pagliero, A. Ajoy, J.A. Reimer, A. Pines, C.A. Meriles, Nano Lett. 19, 2389 (2019). (ASAP article). Available as arXiv:1904.08563v1

We study the case of an NV center in diamond interacting with a near-surface paramagnetic defect (P1), in turn coupled  to protons outside the diamond crystal. We theoretically show that protons spin-polarize efficiently upon a magnetic field sweep across the NV–P1 level anti-crossing. The polarization transfer process is robust to NV misalignment relative to the external magnetic field, and efficient over a broad range of electron-electron and electron-nuclear spin couplings, even if proxy spins feature short coherence or spin-lattice relaxation times.


“Dynamics of frequency-swept nuclear spin optical pumping in powdered diamond at low magnetic fields”, P.R. Zangara, S. Dhomkar, A. Ajoy, K. Liu, R. Nazarian, D. Pagliero, D. Suter, J.A. Reimer, A. Pines, C.A. Meriles, Proc. Natl. Acad. Sci. USA 116, 2512 (2019). Available as arXiv:1902.06805.

We articulate experiment, theory, and numerical modeling to shed light on the optical pumping of 13C spins in an NV-hosting diamond powder subjected to simultaneous laser excitation and MW frequency sweeps.  The understanding we gain should help expedite applications where powders are intrinsically advantageous, including the hyper-polarization of target fluids in contact with the diamond surface or the use of hyperpolarized particles as contrast agents for in-vivo imaging.


“Microwave-assisted cross-polarization of nuclear spin ensembles from optically-pumped nitrogen-vacancy centers in diamond”, F. Shagieva, S. Zaiser, P. Neumann, D.B.R. Dasari, R. Stöhr, A. Denisenko, R. Reuter, C.A. Meriles, J. Wrachtrup, Nano Lett. 18, 3731 (2018). (ASAP article). Available as arXiv:1803.05608v1.

Here we demonstrate variable-magnetic-field cross-polarization from the NV electronic spin to protons in a model viscous fluid in contact with the diamond surface. Our experiments suggest slower molecular diffusion at nm distances from the diamond surface compared to that in bulk, an observation consistent with present models of the microscopic structure of a fluid close to a solid interface.


“Charge dynamics in near-surface, variable-density ensembles of nitrogen-vacancy centers in diamond”, S. Dhomkar, H. Jayakumar, P.R. Zangara, C.A. Meriles, Nano Lett. 18, 4046 (2018). (ASAP article). Available as arXiv:1807.00229.

Using multi-color confocal microscopy, we show that near-surface NVs ionize and recombine via single-photon processes due to concentration-dependent state hybridization with orbitals from neighboring traps. Further, we observe charge transfer from and to NVs in the dark which we reproduce semi-quantitatively via Monte Carlo modeling. These findings can find application for nanoscale electro-chemical sensing, or for data storage with sub-diffraction resolution.


“Orientation independent room-temperature optical 13C hyperpolarization in powdered diamond”, A. Ajoy, K. Liu, R. Nazaryan, X. Lv, P.R. Zangara, B. Safvati, G. Wang, D. Arnold, G. Li, A. Lin, P. Raghavan, E. Druga, S. Dhomkar, D. Pagliero, J.A. Reimer, D. Suter, C.A. Meriles, A. Pines, Science Adv. 4, eaar5492 (2018).  

Dynamic polarization of nuclear spins via optically pumped NVs is an intriguing route to enhanced-sensitivity NMR but applications have been limited to single crystals. Here we attain record levels of 13C spin polarization in powdered diamond under ambient conditions. These results pave the way towards the use of hyperpolarized diamond particles as imaging contrast agents for biosensing and, ultimately, for the hyperpolarization of nuclear spins in arbitrary liquids brought in contact with their surface.


“Multi-spin-assisted optical pumping of bulk 13C nuclear spin polarization in diamond”, D. Pagliero, K.R. Koteswara Rao, P.R. Zangara, S. Dhomkar, H.H. Wong, A. Abril, N. Aslam, A. Parker, J. King, C.E. Avalos, A. Ajoy, J. Wrachtrup, A. Pines, C.A. Meriles, Phys. Rev. B 97, 024422 (2018)(Editor’s choice). Also available as arXiv:1711.07576.

One of the most remarkable properties of the nitrogen-vacancy (NV) center in diamond is that optical illumination initializes its electronic spin almost completely, a feature that can be exploited to polarize other spin species in their proximity to record levels under ambient conditions. Here we show 13C spin pumping near 51 mT takes place via a multi-spin cross relaxation process involving the NV spin and the electronic and nuclear spins of neighboring P1 centers.


“On-demand generation of neutral and negatively-charged silicon-vacancy centers in diamond”, S. Dhomkar, P. Zangara, C.A. Meriles, Phys. Rev. Lett. 120, 117401 (2018). Available as arXiv:1803.06569v1.

The silicon-vacancy (SiV) center in diamond is emerging as a new platform for nano-photonics, information processing, and sensing but the controlled conversion between its most common charge states (negative and neutral) has so far proven elusive. Here we demonstrate on demand generation of SiV- and SiV0 over large areas using laser excitation of variable wavelength and intensity.


“Near-deterministic activation of single-photon emitters in hexagonal boron nitride”, N. Proscia, Z. Shotan, H. Jayakumar, P. Reddy, M. Dollar, A. Alkauskas, M.W. Doherty, C.A. Meriles, V.M. Menon, Optica 5, 1128 (2018).  Available as arXiv:1712.01352.

We demonstrate strain-induced activation of single-photon emitters in hexagonal boron nitride into a bright state through charge trapping in deformation potentials. The process is nearly 100% efficient yielding stable emitters at room temperature over arbitrarily shaped spatial patterns. This article was chosen for Optica’s cover


KikuchietalAn_ThumbnailFig“Long-distance excitation of nitrogen-vacancy centers in diamond via propagating surface spin waves”, D. Kikuchi, D. Prananto, K. Hayashi, A. Laraoui, N. Mizuochi, M. Hatano, E. Saitoh, Y. Kim, C.A. Meriles, T. An, Appl. Phys. Express 10, 103004 (2017). Also available as arXiv:1708.00596.

Coherent communication over mesoscale distances is a necessary condition for the application of solid-state spin qubits to scalable quantum information processing. As an initial step in this direction, here we make use of room-temperature spin waves to mediate the interaction between the microwave field from an antenna and the spin of an NV center 3.6 mm away.


Screen Shot 2017-03-25 at 5.43.24 PM“Non-volatile nuclear spin memory enables sensor-unlimited nanoscale spectroscopy of small spin clusters”, M. Pfender, N. Aslam, H. Sumiya, S. Onoda, P. Neumann, J. Isoya, C.A. Meriles, J. Wrachtrup, Nature Commun. 8, 834 (2017). Available as arXiv: 1610.05675v1.

In nanoscale metrology applications, measurements are commonly limited by the performance of the sensor. Here we use a hybrid quantum-classical sensor device to demonstrate  NMR spectral resolution of single spins down to 13 Hz. This work paves the way for high resolution NMR spectroscopy on nanoscopic quantum systems down to the single level.


shotanetal_thumbnail“Photo-induced modification of single photon emitters in hexagonal boron nitride”, Z. Shotan, H. Jayakumar, C.R. Considine, M. Mackoit, H. Fedder, J. Wrachtrup, A. Alkauskas, M.W. Doherty, V.M. Menon, C.A. Meriles, ACS Photonics  3, 2490 (2016) . 

We uncover singular phenomenology in the emission of individual fluorescent defects in boron nitride exposed to suitable laser pulses.


Screen Shot 2016-05-05 at 7.27.02 PMLong-term data storage in diamond”, S. Dhomkar, J. Henshaw, H. Jayakumar, C.A. Meriles, Science Adv. 2, e1600911 (2016). Available as arXiv:1610.09022

We use NV centers in diamond to demonstrate high-density, three-dimensional read/writing of classical information. We also show how nuclear spins can serve as ancillary memories for sub-diffraction data encoding.


NV_ElectronBus“Towards a room-temperature spin quantum bus in diamond via optical spin injection, transport and detection”, M.W. Doherty, C.A. Meriles, A. Alkauskas, H. Fedder, M.J. Sellars, N.B. Manson, Phys. Rev. X 6, 041035 (2016). Available as arXiv:1511.08559.

We discuss the use of charge carriers to generate entanglement between remote nuclear spin qubits in diamond at room temperature


Screen Shot 2016-05-05 at 7.24.14 PM“Optical patterning of trapped charge in nitrogen-doped diamond”, H. Jayakumar, J. Henshaw, S. Dhomkar, D. Pagliero, A. Laraoui, N.B. Manson, R. Albu, M.W. Doherty, C.A. Meriles, Nature Commun. 7, 12660 (2016). Also available as arXiv:1609.03085.

We investigate the diffusion and trapping of charge carriers photo-ionized from NVs and P1 centers in diamond. We observe the formation of intriguing patters that we reproduce semi-quantitatively via a model of coupled master equations.


NV_ThermalSensing2“Imaging thermal conductivity with nanoscale resolution using a scanning spin probe”, A. Laraoui, H. Aycock-Rizzo, X. Lu, Y. Gao, E. Riedo, C.A. Meriles, Nature Commun. 6, 8954 (2015). Available as arXiv:1511.06916.

We use nanoparticle-hosted NVs attached to a thermal AFM tip as a local probe to measure the thermal conductivity of heterogeneous systems with nanometer resolution.


Screen Shot 2016-05-05 at 6.10.25 PM“Probing molecular dynamics at the nanoscale via an individual paramagnetic center”, T.M. Staudacher, N. Raatz, S. Pezzagna, J. Meijer, F. Reinhard, C.A. Meriles, J. Wrachtrup, Nature Commun. 6, 8527 (2015). Available as arXiv:1507.05921.

We work with NV centers nanometers below the crystal surface to probe the near-surface dynamics of molecules from organic systems including solid films and liquids. For the latter group, we manage to separately identify adsorbed and freely diffusing molecules.


 NV5“Dynamic nuclear spin polarization of liquids and gases in contact with nanostructured diamond”, D. Abrams, M.E. Trusheim, D. Englund, M.D. Shattuck, C.A. Meriles, Nano Lett. 14, 2471 (2014).

We discuss the use of near-surface NV centers to polarize the nuclear spins from organic molecules within arbitrary fluids brought in direct contact with the diamond surface.


NV_Nanoparticles1“Scalable Fabrication of High Purity Diamond Nanocrystals with Long-Spin-Coherence Nitrogen Vacancy Centers”, M.E. Trusheim, L. Li, A. Laraoui, E.H. Chen, O. Gaathon, H. Bakhru, T. Schroeder, C.A. Meriles, D.R. Englund, Nano Lett. 14, 32 (2014).

We demonstrate record-long spin coherence lifetimes for NVs within engineered, high-purity diamond nanoparticles.


NV_P1CenterPolarization1“Approach to dark spin cooling in a diamond nanocrystal”, A. Laraoui, C.A. Meriles, ACS Nano 7, 3403 (2013). Available as arxiv:1703.03988

We demonstrate efficient spin polarization transfer from NVs to P1 centers in their vicinity. Further, using the NVs as a local probe, we determine that the P1 center spin polarization reaches up to 50% within a 10 nm volume centered at the NV.


NV_Correlations1“High-Resolution Correlation Spectroscopy of 13C Spins Near a Nitrogen-Vacancy Center in Diamond”, A. Laraoui, F. Dolde, C. Burk, F. Reinhard, J. Wrachtrup, C.A. Meriles, Nature Commun. 4, 1651 (2013). Available as arXiv:1305.1536.

We introduce a new NV-based technique to probe weakly coupled nuclear spins. Unlike prior approaches, this method exploits the long NV spin-lattice relaxation times to attain highly-resolved NMR spectra from the nuclear spin noise.


NV_ProtonSensing2“Nuclear magnetic resonance spectroscopy on a (5nm)3 volume of liquid and solid samples”, T. Staudacher, F. Shi, S. Pezzagna, J. Meijer, J. Du, C.A. Meriles, F. Reinhard, J. Wrachtrup, Science 339, 561 (2013).

We demonstrate for the first time detection the use of shallow NVs to probe nuclear spins from an arbitrary organic system deposited on the diamond surface.


NV_DetectingP1Centers“Nitrogen-Vacancy-assisted magnetometry of paramagnetic centers in an individual diamond nanocrystal”, A. Laraoui, J.S. Hodges, C.A. Meriles, Nano Lett. 12, 3477 (2012).

We use double resonance techniques to probe P1 centers contained in an individual diamond nanocrystal.


OPinGalliumArsenide1“Optically re-writable patterns of nuclear magnetization in Gallium Arsenide”, J.P. King, Y. Li, C.A. Meriles, J.A. Reimer, Nature Commun. 3, 918 (2012).

We use the large magnetic field gradient to image the nuclear spin polarization induced by optical pumping of a gallium arsenide wafer. We show that low illumination intensities generate a non-monotonic polarization profile where nuclear spins polarize positively or negatively, depending on the distance to the sample surface.


FaradayRotationInLiquids2“Magneto-optical contrast in liquid-state optically-detected NMR spectroscopy”, D. Pagliero, C.A. Meriles, Proc. Natl. Acad. Sci. USA 108, 19510 (2011).

We use time-resolved Faraday rotation at 10 T to demonstrate for the first time chemical-shift-resolved NMR of arbitrary solvents.


FaradayRotationInLiquids1“Time-resolved optically-detected NMR of fluids at high-magnetic field”, D. Pagliero, W. Dong, D. Sakellariou, C.A. Meriles, J. Chem. Phys. 133, 154505 (2010).

We demonstrate optical detection of magnetic resonance at high-magnetic field using time-resolved Faraday rotation.


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