24 research outputs found
NV center emission in a substrate free low index environment
With in-built advantages (high quantum efficiency and room temperature photostability1) for deployment in quantum technologies as a bright on-demand source of single photons, the nitrogen vacancy (NV) center is the most widely studied optical defect in diamond. Despite significant success in controlling its spontaneous emission2, the fundamental understanding of its photo-physics in various environments and host material remains incomplete. Studying NV photoemission from nanodiamonds on a glass substrate, we recently pointed out a disparity between the measured and calculated decay rates (assuming near unity quantum efficiency)3. This indicates the presence of some strong nonradiative influences from factors most likely intrinsic to nanodiamond itself. To obtain a clearer picture of the NV emission, here we remove the substrate contributions to the decay rates by embedding our nanodiamonds inside silica aerogel, a substrate-free environment of effective index n ∼ 1.05. Nanodiamond doped aerogel samples were fabricated using the two-step process4. Time-resolved fluorescence measurement on ∼20 centers for both coverslip and aerogel configurations, showed an increase in the mean lifetime (∼37%) and narrowing of the distribution width (∼40%) in the aerogel environment, which we associate with the absence of a air/cover-glass interface near the radiating dipoles3. Finite difference time domain (FDTD) calculations showed the strong influence of the irregular nanodiamond geometry on the remaining distribution width. Finally a comparison between measurements and calculations provides an estimate of the quantum efficiency of the nanodiamond NV emitters as ∼0.7. This value is apparently consistent with recent reports concerning the oscillation of the NV center between negative and neutral charge states5. © 2013 SPIE
Quantum control of proximal spins using nanoscale magnetic resonance imaging
Quantum control of individual spins in condensed matter systems is an
emerging field with wide-ranging applications in spintronics, quantum
computation, and sensitive magnetometry. Recent experiments have demonstrated
the ability to address and manipulate single electron spins through either
optical or electrical techniques. However, it is a challenge to extend
individual spin control to nanoscale multi-electron systems, as individual
spins are often irresolvable with existing methods. Here we demonstrate that
coherent individual spin control can be achieved with few-nm resolution for
proximal electron spins by performing single-spin magnetic resonance imaging
(MRI), which is realized via a scanning magnetic field gradient that is both
strong enough to achieve nanometric spatial resolution and sufficiently stable
for coherent spin manipulations. We apply this scanning field-gradient MRI
technique to electronic spins in nitrogen-vacancy (NV) centers in diamond and
achieve nanometric resolution in imaging, characterization, and manipulation of
individual spins. For NV centers, our results in individual spin control
demonstrate an improvement of nearly two orders of magnitude in spatial
resolution compared to conventional optical diffraction-limited techniques.
This scanning-field-gradient microscope enables a wide range of applications
including materials characterization, spin entanglement, and nanoscale
magnetometry.Comment: 7 pages, 4 figure
High-sensitivity diamond magnetometer with nanoscale resolution
We present a novel approach to the detection of weak magnetic fields that
takes advantage of recently developed techniques for the coherent control of
solid-state electron spin quantum bits. Specifically, we investigate a magnetic
sensor based on Nitrogen-Vacancy centers in room-temperature diamond. We
discuss two important applications of this technique: a nanoscale magnetometer
that could potentially detect precession of single nuclear spins and an optical
magnetic field imager combining spatial resolution ranging from micrometers to
millimeters with a sensitivity approaching few femtotesla/Hz.Comment: 29 pages, 4 figure
Room temperature coherent control of coupled single spins in solid
Coherent coupling between single quantum objects is at the heart of modern
quantum physics. When coupling is strong enough to prevail over decoherence, it
can be used for the engineering of correlated quantum states. Especially for
solid-state systems, control of quantum correlations has attracted widespread
attention because of applications in quantum computing. Such coherent coupling
has been demonstrated in a variety of systems at low temperature1, 2. Of all
quantum systems, spins are potentially the most important, because they offer
very long phase memories, sometimes even at room temperature. Although precise
control of spins is well established in conventional magnetic resonance3, 4,
existing techniques usually do not allow the readout of single spins because of
limited sensitivity. In this paper, we explore dipolar magnetic coupling
between two single defects in diamond (nitrogen-vacancy and nitrogen) using
optical readout of the single nitrogen-vacancy spin states. Long phase memory
combined with a defect separation of a few lattice spacings allow us to explore
the strong magnetic coupling regime. As the two-defect system was well-isolated
from other defects, the long phase memory times of the single spins was not
diminished, despite the fact that dipolar interactions are usually seen as
undesirable sources of decoherence. A coherent superposition of spin pair
quantum states was achieved. The dipolar coupling was used to transfer spin
polarisation from a nitrogen-vacancy centre spin to a nitrogen spin, with
optical pumping of a nitrogen-vacancy centre leading to efficient
initialisation. At the level anticrossing efficient nuclear spin polarisation
was achieved. Our results demonstrate an important step towards controlled spin
coupling and multi-particle entanglement in the solid state
Scalable quantum register based on coupled electron spins in a room temperature solid
Realization of devices based on quantum laws might lead to building
processors that outperform their classical analogues and establishing
unconditionally secure communication protocols. Solids do usually present a
serious challenge to quantum coherence. However, owing to their spin-free
lattice and low spin orbit coupling, carbon materials and particularly diamond
are suitable for hosting robust solid state quantum registers. We show that
scalable quantum logic elements can be realized by exploring long range
magnetic dipolar coupling between individually addressable single electron
spins associated with separate color centers in diamond. Strong distance
dependence of coupling was used to characterize the separation of single qubits
98 A with unprecedented accuracy (3 A) close to a crystal lattice spacing. Our
demonstration of coherent control over both electron spins, conditional
dynamics, selective readout as well as switchable interaction, opens the way
towards a room temperature solid state scalable quantum register. Since both
electron spins are optically addressable, this solid state quantum device
operating at ambient conditions provides a degree of control that is currently
available only for atomic systems.Comment: original submitted version of the manuscrip
Processing 15-nm nanodiamonds containing nitrogen-vacancy centres for single-molecule FRET
Colour centres in nanodiamonds have many properties such as chemical and physical stability, biocompatibility, straightforward surface functionalisation as well as bright and stable photoluminescence, which make them attractive for biological applications. Here we examine the use of fluorescent nanodiamonds containing a single nitrogen-vacancy (NV) centre, as an alternative nano-label over conventional fluorophores. We describe a series of chemical treatments and air oxidation to reliably produce small (∼15nm) oxidised nanodiamonds suitable for applications in bioscience. We use Frster resonance energy transfer to measure the coupling efficiency from a single NV centre in a selected nanodiamond to an IRDye 800CW dye molecule absorbed onto the surface. Our single-molecule Frster resonance energy transfer analysis, based on fluorescence lifetime measurements, locates the position of the photostable NV centre deep within the core of the nanodiamond. © 2012 CSIRO
Critical components for diamond-based quantum coherent devices
C1 - Journal Articles Referee
Emission and nonradiative decay of nanodiamond NV centers in a low refractive index environment
The nitrogen vacancy (NV) center is the most widely studied single optical defect in diamond with great potential for applications in quantum technologies. Development of practical single-photon devices requires an understanding of the emission under a range of conditions and environments. In this work, we study the properties of a single NV center in nanodiamonds embedded in an air-like silica aerogel environment which provides a new domain for probing the emission behavior of NV centers in nanoscale environments. In this arrangement, the emission rate is governed primarily by the diamond crystal lattice with negligible contribution from the surrounding environment. This is in contrast to the conventional approach of studying nanodiamonds on a glass coverslip. We observe an increase in the mean lifetime due to the absence of a dielectric interface near the emitting dipoles and a distribution arising from the irregularities in the nanodiamond geometry. Our approach results in the estimation of the mean quantum efficiency (∼0.7) of the nanodiamond NV emitters. © 2013 American Chemical Society