3,451 research outputs found
High resolution spectroscopy of single NV defects coupled with nearby C nuclear spins in diamond
We report a systematic study of the hyperfine interaction between the
electron spin of a single nitrogen-vacancy (NV) defect in diamond and nearby
C nuclear spins, by using pulsed electron spin resonance spectroscopy.
We isolate a set of discrete values of the hyperfine coupling strength ranging
from 14 MHz to 400 kHz and corresponding to C nuclear spins placed at
different lattice sites of the diamond matrix. For each lattice site, the
hyperfine interaction is further investigated through nuclear spin polarization
measurements and by studying the magnetic field dependence of the hyperfine
splitting. This work provides informations that are relevant for the
development of nuclear-spin based quantum register in diamond.Comment: 8 pages, 5 figure
Magnetic imaging with an ensemble of Nitrogen Vacancy centers in diamond
The nitrogen-vacancy (NV) color center in diamond is an atom-like system in
the solid-state which specific spin properties can be efficiently used as a
sensitive magnetic sensor. An external magnetic field induces Zeeman shifts of
the NV center levels which can be measured using Optically Detected Magnetic
Resonance (ODMR). In this work, we exploit the ODMR signal of an ensemble of NV
centers in order to quantitatively map the vectorial structure of a magnetic
field produced by a sample close to the surface of a CVD diamond hosting a thin
layer of NV centers. The reconstruction of the magnetic field is based on a
maximum-likelihood technique which exploits the response of the four intrinsic
orientations of the NV center inside the diamond lattice. The sensitivity
associated to a 1 {\mu}m^2 area of the doped layer, equivalent to a sensor
consisting of approximately 10^4 NV centers, is of the order of 2
{\mu}T/sqrt{Hz}. The spatial resolution of the imaging device is 400 nm,
limited by the numerical aperture of the optical microscope which is used to
collect the photoluminescence of the NV layer. The versatility of the sensor is
illustrated by the accurate reconstruction of the magnetic field created by a
DC current inside a copper wire deposited on the diamond sample.Comment: 11 pages, 5 figures, figure 4 added, results unchange
Magnetic-field-dependent photodynamics of single NV defects in diamond: Application to qualitative all-optical magnetic imaging
Magnetometry and magnetic imaging with nitrogen-vacancy (NV) defects in
diamond rely on the optical detection of electron spin resonance (ESR).
However, this technique is inherently limited to magnetic fields that are weak
enough to avoid electron spin mixing. Here we focus on the high off-axis
magnetic field regime for which spin mixing alters the NV defect spin dynamics.
We first study in a quantitative manner the dependence of the NV defect optical
properties on the magnetic field vector B. Magnetic-field-dependent
time-resolved photoluminescence (PL) measurements are compared to a seven-level
model of the NV defect that accounts for field-induced spin mixing. The model
reproduces the decreases in (i) ESR contrast, (ii) PL intensity and (iii)
excited level lifetime with an increasing off-axis magnetic field. We next
demonstrate that those effects can be used to perform all-optical magnetic
imaging in the high off-axis magnetic field regime. Using a scanning NV defect
microscope, we map the stray field of a magnetic hard disk through both PL and
fluorescence lifetime imaging. This all-optical method for high magnetic field
imaging at the nanoscale might be of interest in the field of nanomagnetism,
where samples producing fields in excess of several tens of milliteslas are
typical
Different methods of evaluation of Monilinia laxa on apricot flowers and branches
- Organic apricot production is currently not profitable.
- The main obstacle to sustainable profitability is brown rot caused by the fungus Monilinia laxa (Aderh. & Ruhl).
- In the current apricot germplasm no source of total resistance has been shown, but some varieties are expressing interesting levels of tolerance.
- A good evaluation of the M. laxa symptoms is essential for a precise diagnosis of the infection and to appreciate differences between tolerant and susceptible varieties and genotypes
Perfect preferential orientation of nitrogen-vacancy defects in a synthetic diamond sample
We show that the orientation of nitrogen-vacancy (NV) defects in diamond can
be efficiently controlled through chemical vapor deposition (CVD) growth on a
(111)-oriented diamond substrate. More precisely, we demonstrate that
spontaneously generated NV defects are oriented with a ~ 97 % probability along
the [111] axis, corresponding to the most appealing orientation among the four
possible crystallographic axes. Such a nearly perfect preferential orientation
is explained by analyzing the diamond growth mechanism on a (111)-oriented
substrate and could be extended to other types of defects. This work is a
significant step towards the design of optimized diamond samples for quantum
information and sensing applications.Comment: 6 pages, 4 figure
Avoiding power broadening in optically detected magnetic resonance of single NV defects for enhanced DC-magnetic field sensitivity
We report a systematic study of the magnetic field sensitivity of a magnetic
sensor based on a single Nitrogen-Vacancy (NV) defect in diamond, by using
continuous optically detected electron spin resonance (ESR) spectroscopy. We
first investigate the behavior of the ESR contrast and linewidth as a function
of the microwave and optical pumping power. The experimental results are in
good agreement with a simplified model of the NV defect spin dynamics, yielding
to an optimized sensitivity around 2 \mu T/\sqrt{\rm Hz}. We then demonstrate
an enhancement of the magnetic sensitivity by one order of magnitude by using a
simple pulsed-ESR scheme. This technique is based on repetitive excitation of
the NV defect with a resonant microwave \pi-pulse followed by an optimized
read-out laser pulse, allowing to fully eliminate power broadening of the ESR
linewidth. The achieved sensitivity is similar to the one obtained by using
Ramsey-type sequences, which is the optimal magnetic field sensitivity for the
detection of DC magnetic fields
Feedbacks in QCA: a Quantitative Approach
In the post-CMOS scenario a primary role is played by the quantum-dot cellular automata (QCA) technology. Irrespective of the specific implementation principle (e.g., either molecular, or magnetic or semiconductive in the current scenario) the intrinsic deep-level pipelined behavior is the dominant issue. It has important consequences on circuit design and performance, especially in the presence of feedbacks in sequential circuits. Though partially already addressed in literature, these consequences still must be fully understood and solutions thoroughly approached to allow this technology any further advancement. This paper conducts an exhaustive analysis of the effects and the consequences derived by the presence of loops in QCA circuits. For each problem arisen, a solution is presented. The analysis is performed using as a test architecture, a complex systolic array circuit for biosequences analysis (Smith–Waterman algorithm), which represents one of the most promising application for QCA technology. The circuit is based on nanomagnetic logic as QCA implementation, is designed down to the layout level considering technological constraints and experimentally validated structures, counts up to approximately 2.3 milion nanomagnets, and is described and simulated with HDL language using as a testbench realistic protein alignment sequences. The results here presented constitute a fundamental advancement in the emerging technologies field since: 1) they are based on a quantitative approach relying on a realistic and complex circuit involving a large variety of QCA blocks; 2) they strictly are reckoned starting from current technological limits without relying on unrealistic assumptions; 3) they provide general rules to design complex sequential circuits with intrinsically pipelined technologies, like QCA; and 4) they prove with a real application benchmark how to maximize the circuits performance
- …