186 research outputs found
Bone marrow examination: a prospective survey on factors associated with pain
Bone marrow examination (BME) represents an essential tool for diagnosis and monitoring of haematological disorders. It remains associated with morbidity and discomfort; repeat examinations are frequent. We made a single-centre prospective survey on 700 BME between July 2007 and July 2008 with a structured anonymized questionnaire for patients undergoing and physicians performing BME, which includes at our institution always aspiration and trephine. All procedures were performed according to institutionalised standard operating procedures; 412 patients' (58.9%) and 554 physicians' (79.1%) questionnaires were returned. Pain was the only procedure-related complication; no pain was reported in 149 (36.7%), bearable pain in 242 (59.6%) and unbearable pain in 15 (3.7%) cases. Premedication associated complications were reported by 110 (32.7%) of the 336 (65.4%) patients with premedication before BME. None of these were > WHO grade 2; most frequently reported were tiredness (76 patients; 22.6%), dizziness (19 patients; 5.7%) and nausea (15 patients; 4.5%). Only two factors were significantly associated with unbearable pain: "pain during prior BME” (seven of 94 with versus one of 198 without previous pain; p < 0.01) and "information before BME” (four of 11 without versus 12 of 372 with adequate information before BME; p < 0.01). Inadequate information at any time showed a trend towards an association with unbearable pain (p = 0.08). No other factor was associated with unbearable pain. Good and adequate information appears to be the best way to reduce pain, even for a future BM
Modeling temperature-dependent population dynamics in the excited state of the nitrogen-vacancy center in diamond
The nitrogen-vacancy (NV) center in diamond is well known in quantum
metrology and quantum information for its favorable spin and optical
properties, which span a wide temperature range from near zero to over 600 K.
Despite its prominence, the NV center's photo-physics is incompletely
understood, especially at intermediate temperatures between 10-100 K where
phonons become activated. In this work, we present a rate model able to
describe the cross-over from the low-temperature to the high-temperature
regime. Key to the model is a phonon-driven hopping between the two orbital
branches in the excited state (ES), which accelerates spin relaxation via an
interplay with the ES spin precession. We extend our model to include magnetic
and electric fields as well as crystal strain, allowing us to simulate the
population dynamics over a wide range of experimental conditions. Our model
recovers existing descriptions for the low- and high-temperature limits, and
successfully explains various sets of literature data. Further, the model
allows us to predict experimental observables, in particular the
photoluminescence (PL) emission rate, spin contrast, and spin initialization
fidelity relevant for quantum applications. Lastly, our model allows probing
the electron-phonon interaction of the NV center and reveals a gap between the
current understanding and recent experimental findings
Rapid flipping of parametric phase states
Since the invention of the solid-state transistor, the overwhelming majority
of computers followed the von Neumann architecture that strictly separates
logic operations and memory. Today, there is a revived interest in alternative
computation models accompanied by the necessity to develop corresponding
hardware architectures. The Ising machine, for example, is a variant of the
celebrated Hopfield network based on the Ising model. It can be realized with
artifcial spins such as the `parametron' that arises in driven nonlinear
resonators. The parametron encodes binary information in the phase state of its
oscillation. It enables, in principle, logic operations without energy transfer
and the corresponding speed limitations. In this work, we experimentally
demonstrate flipping of parametron phase states on a timescale of an
oscillation period, much faster than the ringdown time \tau that is often
(erroneously) deemed a fundamental limit for resonator operations. Our work
establishes a new paradigm for resonator-based logic architectures.Comment: 6 pages, 3 figure
Temperature dependence of photoluminescence intensity and spin contrast in nitrogen-vacancy centers
We report on measurements of the photoluminescence (PL) properties of single
nitrogen-vacancy (NV) centers in diamond at temperatures between 4-300 K. We
observe a strong reduction of the PL intensity and spin contrast between ca.
10-100 K that recovers to high levels below and above. Further, we find a rich
dependence on magnetic bias field and crystal strain. We develop a
comprehensive model based on spin mixing and orbital hopping in the electronic
excited state that quantitatively explains the observations. Beyond a more
complete understanding of the excited-state dynamics, our work provides a novel
approach for probing electron-phonon interactions and a predictive tool for
optimizing experimental conditions for quantum applications.Comment: Companion paper: arXiv:2304.02521 | Model:
https://github.com/sernstETH/nvratemode
Towards Quantum Sensing of Chiral-Induced Spin Selectivity: Probing Donor-Bridge-Acceptor Molecules with NV Centers in Diamond
Photoexcitable donor-bridge-acceptor (D-B-A) molecules that support
intramolecular charge transfer are ideal platforms to probe the influence of
chiral-induced spin selectivity (CISS) in electron transfer and resulting
radical pairs. In particular, the extent to which CISS influences spin
polarization or spin coherence in the initial state of spin-correlated radical
pairs following charge transfer through a chiral bridge remains an open
question. Here, we introduce a quantum sensing scheme to measure directly the
hypothesized spin polarization in radical pairs using shallow nitrogen-vacancy
(NV) centers in diamond at the single- to few-molecule level. Importantly, we
highlight the perturbative nature of the electron spin-spin dipolar coupling
within the radical pair, and demonstrate how Lee-Goldburg decoupling can
preserve spin polarization in D-B-A molecules for enantioselective detection by
a single NV center. The proposed measurements will provide fresh insight into
spin selectivity in electron transfer reactions.Comment: 7 pages and 4 pages appendix including an extensive description of
the initial spin state of photo-generated radical pair
Near-resonant nuclear spin detection with high-frequency mechanical resonators
Mechanical resonators operating in the high-frequency regime have become a
versatile platform for fundamental and applied quantum research. Their
exceptional properties, such as low mass and high quality factor, make them
also very appealing for force sensing experiments. In this Letter, we propose a
method for detecting and ultimately controlling nuclear spins by directly
coupling them to high-frequency resonators via a magnetic field gradient.
Dynamical backaction between the sensor and an ensemble of nuclear spins
produces a shift in the sensor's resonance frequency, which can be measured to
probe the spin ensemble. Based on analytical as well as numerical results, we
predict that the method will allow nanoscale magnetic resonance imaging with a
range of realistic devices. At the same time, this interaction paves the way
for new manipulation techniques, similar to those employed in cavity
optomechanics, enriching both the sensor's and the spin ensemble's features.Comment: Includes Supplemental Materia
Spatially resolved surface dissipation over metal and dielectric substrates
We report spatially resolved measurements of static and fluctuating electric
fields over conductive (Au) and non-conductive (SiO2) surfaces. Using an
ultrasensitive `nanoladder' cantilever probe to scan over these surfaces at
distances of a few tens of nanometers, we record changes in the probe resonance
frequency and damping that we associate with static and fluctuating fields,
respectively. We find that the two quantities are spatially correlated and of
similar magnitude for the two materials. We quantitatively describe the
observed effects on the basis of trapped surface charges and dielectric
fluctuations in an adsorbate layer. Our results provide direct, spatial
evidence for surface dissipation in adsorbates that affects nanomechanical
sensors, trapped ions, superconducting resonators, and color centers in
diamond
Single Nitrogen-Vacancy-NMR of Amine-Functionalized Diamond Surfaces
Nuclear magnetic resonance (NMR) imaging with shallow nitrogen-vacancy (NV)
centers in diamond offers an exciting route toward sensitive and localized
chemical characterization at the nanoscale. Remarkable progress has been made
to combat the degradation in coherence time and stability suffered by
near-surface NV centers using suitable chemical surface termination. However,
approaches that also enable robust control over adsorbed molecule density,
orientation, and binding configuration are needed. We demonstrate a diamond
surface preparation for mixed nitrogen- and oxygen-termination that
simultaneously improves NV center coherence times for emitters <10-nm-deep and
enables direct and recyclable chemical functionalization via amine-reactive
crosslinking. Using this approach, we probe single NV centers embedded in
nanopillar waveguides to perform NMR sensing of covalently
bound trifluoromethyl tags in the ca. 50-100 molecule regime. This work
signifies an important step toward nuclear spin localization and structure
interrogation at the single-molecule level.Comment: 21 pages and 16 pages supporting informatio
Multicone Diamond Waveguides for Nanoscale Quantum Sensing
The long-lived electronic spin of the nitrogen-vacancy (NV) center in diamond
is a promising quantum sensor for detecting nanoscopic magnetic and electric
fields in a variety of experimental conditions. Nevertheless, an outstanding
challenge in improving measurement sensitivity is the poor signal-to-noise
ratio (SNR) of prevalent optical spin-readout techniques. Here, we address this
limitation by coupling individual NV centers to optimized diamond nanopillar
structures, thereby improving optical collection efficiency of fluorescence.
First, we optimize the structure in simulation, observing an increase in
collection efficiency for tall ( 5 m) pillars with tapered
sidewalls. We subsequently verify these predictions by fabricating and
characterizing a representative set of structures using a reliable and
reproducible nanofabrication process. An optimized device yields increased SNR,
owing to improvements in collimation and directionality of emission.
Promisingly, these devices are compatible with low-numerical-aperture,
long-working-distance collection optics, as well as reduced tip radius,
facilitating improved spatial resolution for scanning applications.Comment: 22 pages, five figure
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