758 research outputs found
Spin Readout Techniques of the Nitrogen-Vacancy Center in Diamond
The diamond nitrogen-vacancy (NV) center is a leading platform for quantum
information science due to its optical addressability and room-temperature spin
coherence. However, measurements of the NV center's spin state typically
require averaging over many cycles to overcome noise. Here, we review several
approaches to improve the readout performance and highlight future avenues of
research that could enable single-shot electron-spin readout at room
temperature.Comment: 21 pages, 7 figure
Amplified Sensitivity of Nitrogen-Vacancy Spins in Nanodiamonds using All-Optical Charge Readout
Nanodiamonds containing nitrogen-vacancy (NV) centers offer a versatile
platform for sensing applications spanning from nanomagnetism to in-vivo
monitoring of cellular processes. In many cases, however, weak optical signals
and poor contrast demand long acquisition times that prevent the measurement of
environmental dynamics. Here, we demonstrate the ability to perform fast,
high-contrast optical measurements of charge distributions in ensembles of NV
centers in nanodiamonds and use the technique to improve the spin readout
signal-to-noise ratio through spin-to-charge conversion. A study of 38
nanodiamonds, each hosting 10-15 NV centers with an average diameter of 40 nm,
uncovers complex, multiple-timescale dynamics due to radiative and
non-radiative ionization and recombination processes. Nonetheless, the
nanodiamonds universally exhibit charge-dependent photoluminescence contrasts
and the potential for enhanced spin readout using spin-to-charge conversion. We
use the technique to speed up a relaxometry measurement by a factor of
five.Comment: 13 pages, 14 figure
Optical Signatures of Quantum Emitters in Suspended Hexagonal Boron Nitride
Hexagonal boron nitride (h-BN) is a tantalizing material for solid-state
quantum engineering. Analogously to three-dimensional wide-bandgap
semiconductors like diamond, h-BN hosts isolated defects exhibiting visible
fluorescence, and the ability to position such quantum emitters within a
two-dimensional material promises breakthrough advances in quantum sensing,
photonics, and other quantum technologies. Critical to such applications,
however, is an understanding of the physics underlying h-BN's quantum emission.
We report the creation and characterization of visible single-photon sources in
suspended, single-crystal, h-BN films. The emitters are bright and stable over
timescales of several months in ambient conditions. With substrate interactions
eliminated, we study the spectral, temporal, and spatial characteristics of the
defects' optical emission, which offer several clues about their electronic and
chemical structure. Analysis of the defects' spectra reveals similarities in
vibronic coupling despite widely-varying fluorescence wavelengths, and a
statistical analysis of their polarized emission patterns indicates a
correlation between the optical dipole orientations of some defects and the
primitive crystallographic axes of the single-crystal h-BN film. These
measurements constrain possible defect models, and, moreover, suggest that
several classes of emitters can exist simultaneously in free-standing h-BN,
whether they be different defects, different charge states of the same defect,
or the result of strong local perturbations
Spin-Dependent Quantum Emission in Hexagonal Boron Nitride at Room Temperature
Optically addressable spins associated with defects in wide-bandgap
semiconductors are versatile platforms for quantum information processing and
nanoscale sensing, where spin-dependent inter-system crossing (ISC) transitions
facilitate optical spin initialization and readout. Recently, the van der Waals
material hexagonal boron nitride (h-BN) has emerged as a robust host for
quantum emitters (QEs), but spin-related effects have yet to be observed. Here,
we report room-temperature observations of strongly anisotropic
photoluminescence (PL) patterns as a function of applied magnetic field for
select QEs in h-BN. Field-dependent variations in the steady-state PL and
photon emission statistics are consistent with an electronic model featuring a
spin-dependent ISC between triplet and singlet manifolds, indicating that
optically-addressable spin defects are present in h-BN a versatile
two-dimensional material promising efficient photon extraction, atom-scale
engineering, and the realization of spin-based quantum technologies using van
der Waals heterostructures.Comment: 38 pages, 34 figure
Developments in surface passenger transport. Implications for tourism
This paper was presented at the 1991 Tourism Outlook Forum (Australian Tourism Research Institute). It examines the state of play in the surface passenger transport system and comments on the implications of developments for tourism. Transport is increasingly being regarded as a weak link in Australian tourism, largely due to the declining standard of infrastructure. Nowhere is this more evident than in the road system. As governments at all levels attempt to cope with less resources, road funding is not keeping pace with traffic growth. As a consequence, some of the nation’s busiest highways are in need of major upgrading. The automobile, the most commonly used form of tourist transport, is becoming more fuel efficient as a result of technological developments and environmental pressures. The bus and coach industry is undergoing major changes as a result of competitive pressures both from within the industry and from other modes. Whilst the prospects for charter operations are sound, long-distance express services are under threat, especially as airline competition erodes their market. Conventional rail is also suffering in this environment, but the five government rail systems are under increasing pressure to curb the deficits on long-distance passenger services. The likely outcome is a more efficient rail operation with higher fares and better services on lines with the heaviest traffic. This should provide better opportunities to incorporate rail into tourism products, but rail’s roll will be limited. The proposal to introduce a network of high speed rail services connecting Sydney, Canberra, Melbourne, Brisbane and Adelaide with service levels similar to airline standards offers hope of a significant expansion of the travel market. The Very Fast Train proposal could have a major impact on air and other public transport modes, but would also aim to take a sizable proportion of people out of their cars. This would make it easier to develop attractive packages for a broader tourist market. Finally, Bass Strait has seen the introduction of a high speed ferry and the TT Line will replace the Abel Tasman in 1993 with a luxurious and larger vessel. The outlook for the future is a transport sector with a growing recognition that it is a vital part of tourism
Detection of skewed X-chromosome inactivation in Fragile X syndrome and X chromosome aneuploidy using quantitative melt analysis.
Methylation of the fragile X mental retardation 1 (FMR1) exon 1/intron 1 boundary positioned fragile X related epigenetic element 2 (FREE2), reveals skewed X-chromosome inactivation (XCI) in fragile X syndrome full mutation (FM: CGGÂ >Â 200) females. XCI skewing has been also linked to abnormal X-linked gene expression with the broader clinical impact for sex chromosome aneuploidies (SCAs). In this study, 10 FREE2 CpG sites were targeted using methylation specific quantitative melt analysis (MS-QMA), including 3 sites that could not be analysed with previously used EpiTYPER system. The method was applied for detection of skewed XCI in FM females and in different types of SCA. We tested venous blood and saliva DNA collected from 107 controls (CGGÂ <Â 40), and 148 FM and 90 SCA individuals. MS-QMA identified: (i) most SCAs if combined with a Y chromosome test; (ii) locus-specific XCI skewing towards the hypomethylated state in FM females; and (iii) skewed XCI towards the hypermethylated state in SCA with 3 or more X chromosomes, and in 5% of the 47,XXY individuals. MS-QMA output also showed significant correlation with the EpiTYPER reference method in FM males and females (PÂ <Â 0.0001) and SCAs (PÂ <Â 0.05). In conclusion, we demonstrate use of MS-QMA to quantify skewed XCI in two applications with diagnostic utility
Photon emission correlation spectroscopy as an analytical tool for quantum defects
Photon emission correlation spectroscopy has a long history in the study of
atoms, molecules, and, more recently, solid-state quantum defects. In
solid-state systems, its most common use is as an indicator of single-photon
emission, a key property for quantum technology. However, photon correlation
data can provide a wealth of information about quantum emitters beyond their
single-photon purityinformation that can reveal details about an
emitter's electronic structure and optical dynamics that are hidden by other
spectroscopy techniques. We present a standardized framework for using photon
emission correlation spectroscopy to study quantum emitters, including
discussion of theory, data acquisition, analysis, and interpretation. We
highlight nuances and best practices regarding the commonly-used
test for single-photon emission. Finally, we illustrate
how this experimental technique can be paired with optical dynamics simulations
to formulate an electronic model for unknown quantum emitters, enabling the
design of quantum control protocols and assessment of their suitability for
quantum information science applications.Comment: 20 pages, 7 figures. Updates in version 2 include an expanded section
VI and the addition of two figures and an appendi
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