78 research outputs found
Singlet levels of the NV centre in diamond
The characteristic transition of the NV- centre at 637 nm is between
and triplet states. There are also
intermediate and singlet states, and the
infrared transition at 1042 nm between these singlets is studied here using
uniaxial stress. The stress shift and splitting parameters are determined, and
the physical interaction giving rise to the parameters is considered within the
accepted electronic model of the centre. It is established that this
interaction for the infrared transition is due to a modification of
electron-electron Coulomb repulsion interaction. This is in contrast to the
visible 637 nm transition where shifts and splittings arise from modification
to the one-electron Coulomb interaction. It is also established that a dynamic
Jahn-Teller interaction is associated with the singlet state,
which gives rise to a vibronic level 115 above the
electronic state. Arguments associated with this level are
used to provide experimental confirmation that the is the
upper singlet level and is the lower singlet level.Comment: 19 pages, 6 figure
The non-vanishing effect of detuning errors in dynamical decoupling based quantum sensing experiments
Characteristic dips appear in the coherence traces of a probe qubit when
dynamical decoupling (DD) is applied in synchrony with the precession of target
nuclear spins, forming the basis for nanoscale nuclear magnetic resonance
(NMR). The frequency of the microwave control pulses is chosen to match the
qubit transition but this can be detuned from resonance by experimental errors,
hyperfine coupling intrinsic to the qubit, or inhomogeneous broadening. The
detuning acts as an additional static field which is generally assumed to be
completely removed in Hahn echo and DD experiments. Here we demonstrate that
this is not the case in the presence of finite pulse-durations, where a
detuning can drastically alter the coherence response of the probe qubit, with
important implications for sensing applications. Using the electronic spin
associated with a nitrogen-vacancy centre in diamond as a test qubit system, we
analytically and experimentally study the qubit coherence response under CPMG
and XY8 dynamical decoupling control schemes in the presence of finite
pulse-durations and static detunings. Most striking is the splitting of the NMR
resonance under CPMG, whereas under XY8 the amplitude of the NMR signal is
modulated. Our work shows that the detuning error must not be neglected when
extracting data from quantum sensor coherence traces
Competition between electric field and magnetic field noise in the decoherence of a single spin in diamond
We analyze the impact of electric field and magnetic field fluctuations in
the decoherence of the electronic spin associated with a single
nitrogen-vacancy (NV) defect in diamond by engineering spin eigenstates
protected either against magnetic noise or against electric noise. The
competition between these noise sources is analyzed quantitatively by changing
their relative strength through modifications of the environment. This study
provides significant insights into the decoherence of the NV electronic spin,
which is valuable for quantum metrology and sensing applications.Comment: 8 pages, 4 figures, including supplementary information
Spin properties of dense near-surface ensembles of nitrogen-vacancy centres in diamond
We present a study of the spin properties of dense layers of near-surface
nitrogen-vacancy (NV) centres in diamond created by nitrogen ion implantation.
The optically detected magnetic resonance contrast and linewidth, spin
coherence time, and spin relaxation time, are measured as a function of
implantation energy, dose, annealing temperature and surface treatment. To
track the presence of damage and surface-related spin defects, we perform in
situ electron spin resonance spectroscopy through both double electron-electron
resonance and cross-relaxation spectroscopy on the NV centres. We find that,
for the energy (~keV) and dose (~ions/cm)
ranges considered, the NV spin properties are mainly governed by the dose via
residual implantation-induced paramagnetic defects, but that the resulting
magnetic sensitivity is essentially independent of both dose and energy. We
then show that the magnetic sensitivity is significantly improved by
high-temperature annealing at C. Moreover, the spin properties
are not significantly affected by oxygen annealing, apart from the spin
relaxation time, which is dramatically decreased. Finally, the average NV depth
is determined by nuclear magnetic resonance measurements, giving
-17~nm at 4-6 keV implantation energy. This study sheds light on the
optimal conditions to create dense layers of near-surface NV centres for
high-sensitivity sensing and imaging applications.Comment: 12 pages, 7 figure
Diamond quantum magnetometer with dc sensitivity of < 10 pT Hz toward measurement of biomagnetic field
We present a sensitive diamond quantum sensor with a magnetic field
sensitivity of in a near-dc frequency range
of 5 to 100~Hz. This sensor is based on the continuous-wave optically detected
magnetic resonance of an ensemble of nitrogen-vacancy centers along the [111]
direction in a diamond (111) single crystal. The long in our diamond and the reduced intensity noise in
laser-induced fluorescence result in remarkable sensitivity among diamond
quantum sensors. Based on an Allan deviation analysis, we demonstrate that a
sub-picotesla field of 0.3~pT is detectable by interrogating the magnetic field
for a few thousand seconds. The sensor head is compatible with various
practical applications and allows a minimum measurement distance of about 1~mm
from the sensing region. The proposed sensor facilitates the practical
application of diamond quantum sensors.Comment: 8 pages, 5 figure
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