arXiv subjects

Abdelghani Laraoui

Publications and source records attributed to Abdelghani Laraoui.

28 records · Page 2Linked to original sources

arXiv2017

Long-distance excitation of nitrogen-vacancy centers in diamond via surface spin waves

Coherent communication over mesoscale distances is a necessary condition for the application of solid-state spin qubits to scalable quantum information processing. Among other routes under study, one possibility entails the generation of magnetostatic surface spin waves (MSSW) dipolarly coupled to shallow paramagnetic defects in wide-bandgap semiconductors. As an initial step in this direction, here we make use of room-temperature MSSWs to mediate the interaction between the microwave field from an antenna and the spin of a nitrogen-vacancy (NV) center in diamond. We show that this transport spans distances exceeding 3 mm, a manifestation of the MSSW robustness and long diffusion length. Using the NV spin as a local sensor, we find that the MSSW amplitude grows linearly with the applied microwave power, suggesting this approach could be extended to amplify the signal from neighboring spin qubits by several orders of magnitude.

cond-mat.mtrl-sci↗

arXiv2017

Approach to Dark Spin Cooling in a Diamond Nanocrystal

Using a Hartman-Hahn protocol, we demonstrate spin polarization transfer from a single, optically-polarized nitrogen-vacancy (NV) center to the ensemble of paramagnetic defects hosted by an individual diamond nanocrystal. Owing to the strong NV-bath coupling, the transfer takes place on a short, microsecond time scale. Upon fast repetition of the pulse sequence we observe strong polarization transfer blockade, which we interpret as an indication of spin bath cooling. Numerical simulations indicate that the spin bath polarization is non-uniform throughout the nanoparticle averaging approximately 5% over the crystal volume, but reaching up to 25% in the immediate vicinity of the NV. These observations may prove relevant to the planning of future bath-assisted magnetometry tests.

cond-mat.mes-hall↗

arXiv2016

Optical patterning of trapped charge in nitrogen-doped diamond

The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here we use two-color optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion, and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce via a model of the interplay between photo-excited carriers and atomic defects. Further, by using the NV as a probe, we map the relative fraction of positively charged nitrogen upon localized optical excitation. These observations may prove important to transporting quantum information between NVs or to developing three-dimensional, charge-based memories.

cond-mat.mes-hall↗

arXiv2015

Imaging nuclear spins weakly coupled to a probe paramagnetic center

Optically-detected paramagnetic centers in wide-bandgap semiconductors are emerging as a promising platform for nanoscale metrology at room temperature. Of particular interest are applications where the center is used as a probe to interrogate other spins that cannot be observed directly. Using the nitrogen-vacancy center in diamond as a model system, we propose a new strategy to determining the spatial coordinates of weakly coupled nuclear spins. The central idea is to label the target nucleus with a spin polarization that depends on its spatial location, which is subsequently revealed by making this polarization flow back to the NV for readout. Using extensive analytical and numerical modeling, we show that the technique can attain high spatial resolution depending on the NV lifetime and target spin location. No external magnetic field gradient is required, which circumvents complications resulting from changes in the direction of the applied magnetic field, and considerably simplifies the required instrumentation. Extensions of the present technique may be adapted to pinpoint the locations of other paramagnetic centers in the NV vicinity or to yield information on dynamical processes in molecules on the diamond surface.

cond-mat.mes-hall↗

arXiv2015

Imaging thermal conductivity with nanoscale resolution using a scanning spin probe

The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the NV to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. With the aid of a combined AFM/confocal setup, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. The small mass and high thermal conductivity of the diamond host make the time response of our technique short, which we demonstrate by monitoring the tip temperature upon application of a heat pulse. Our approach promises multiple applications, from the investigation of phonon dynamics in nanostructures to the characterization of heterogeneous phase transitions and chemical reactions in various solid-state systems.

cond-mat.mes-hall↗

arXiv2014

Recursive polarization of nuclear spins in diamond at arbitrary magnetic fields

We introduce an alternate route to dynamically polarize the nuclear spin host of nitrogen-vacancy (NV) centers in diamond. Our approach articulates optical, microwave and radio-frequency pulses to recursively transfer spin polarization from the NV electronic spin. Using two complementary variants of the same underlying principle, we demonstrate nitrogen nuclear spin initialization approaching 80% at room temperature both in ensemble and single NV centers. Unlike existing schemes, our approach does not rely on level anti-crossings and is thus applicable at arbitrary magnetic fields. This versatility should prove useful in applications ranging from nanoscale metrology to sensitivity-enhanced NMR.

quant-ph↗

arXiv2013

High-Resolution Correlation Spectroscopy of 13C Spins Near a Nitrogen-Vacancy Center in Diamond

Spin complexes comprising the nitrogen-vacancy (NV) center and neighboring spins are being considered as a building block for a new generation of spintronic and quantum information processing devices. Because assembling identical spin clusters is difficult, new strategies are in order to determine individual node structures with the highest precision. Here we use a pulse protocol to monitor the time evolution of the 13C ensemble in the vicinity of a NV center. We observe long-lived time correlations in the nuclear spin dynamics, limited by NV spin-lattice relaxation. We use the host 14N spin as a quantum register, and demonstrate that hyperfine-shifted resonances can be separated upon proper NV initialization. Intriguingly, we find that the amplitude of the correlation signal exhibits a sharp dependence on the applied magnetic field. We discuss this observation in the context of the quantum-to-classical transition proposed recently to explain the field dependence of the spin cluster dynamics.

cond-mat.mes-hall↗

arXiv2011

Rotating frame spin dynamics of a Nitrogen-Vacancy center in a diamond nanocrystal

We investigate the spin dynamics of a Nitrogen-Vacancy (NV) center contained in an individual diamond nanocrystal in the presence of continuous microwave excitation. Upon periodic reversal of the microwave phase, we observe a train of 'Solomon echoes' that effectively extends the system coherence lifetime to reach several tens of microseconds, depending on the microwave power and phase inversion rate. Starting from a model where the NV center interacts with a bath of paramagnetic defects on the nanocrystal surface, we use average Hamiltonian theory to compute the signal envelope from its amplitude at the echo maxima. Comparison between the effective Rabi and Solomon propagators shows that the observed response can be understood as a form of higher-order decoupling from the spin bath.

cond-mat.mes-hall↗

arXiv2011

The diamond Nitrogen-Vacancy center as a probe of random fluctuations in a nuclear spin ensemble

New schemes that exploit the unique properties of Nitrogen-Vacancy (NV) centers in diamond are presently being explored as a platform for high-resolution magnetic sensing. Here we focus on the ability of a NV center to monitor an adjacent mesoscopic nuclear spin bath. For this purpose, we conduct comparative experiments where the NV spin evolves under the influence of surrounding 13C nuclei or, alternatively, in the presence of asynchronous AC fields engineered to emulate bath fluctuations. Our study reveals substantial differences that underscore the limitations of the semi-classical picture when interpreting and predicting the outcome of experiments designed to probe small nuclear spin ensembles. In particular, our study elucidates the NV center response to bath fluctuations under common pulse sequences, and explores a detection protocol designed to probe time correlations of the nuclear spin bath dynamics. Further, we show that the presence of macroscopic nuclear spin order is key to the emergence of semi-classical spin magnetometry.

cond-mat.mes-hall↗

arXiv2010

Magnetometry of random AC magnetic fields using a single Nitrogen-Vacancy center

We report on the use of a single NV center to probe fluctuating AC magnetic fields. Using engineered currents to induce random changes in the field amplitude and phase, we show that stochastic fluctuations reduce the NV center sensitivity and, in general, make the NV response field-dependent. We also introduce two modalities to determine the field spectral composition, unknown a priori in a practical application. One strategy capitalizes on the generation of AC-field-induced coherence 'revivals', while the other approach uses the time-tagged fluorescence intensity record from successive NV observations to reconstruct the AC field spectral density. These studies are relevant for magnetic sensing in scenarios where the field of interest has a non-trivial, stochastic behavior, such as sensing unpolarized nuclear spin ensembles at low static magnetic fields.

cond-mat.mes-hall↗