96 research outputs found
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
Direct observation of the leakage current in epitaxial diamond Schottky barrier devices by conductive-probe atomic force microscopy and Raman imaging
The origin of the high leakage current measured in several vertical-type
diamond Schottky devices is conjointly investigated by conducting probe atomic
force microscopy (CP-AFM) and confocal micro-Raman/Photoluminescence (PL)
imaging analysis. Local areas characterized by a strong decrease of the local
resistance (5-6 orders of magnitude drop) with respect to their close
surrounding have been identified in several different regions of the sample
surface. The same local areas, also referenced as electrical hot-spots, reveal
a slightly constrained diamond lattice and three dominant Raman bands in the
low-wavenumber region (590, 914 and 1040 cm-1). These latter bands are usually
assigned to the vibrational modes involving boron impurities and its possible
complexes that can electrically act as traps for charge carriers. Local
current-voltage measurements performed at the hot-spots point out a
trap-filled-limited (TFL) current as the main conduction mechanism favoring the
leakage current in the Schottky devices
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
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
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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