129 research outputs found
Optical addressing of an individual erbium ion in silicon
The detection of electron spins associated with single defects in solids is a
critical operation for a range of quantum information and measurement
applications currently under development. To date, it has only been
accomplished for two centres in crystalline solids: phosphorus in silicon using
electrical readout based on a single electron transistor (SET) and
nitrogen-vacancy centres in diamond using optical readout. A spin readout
fidelity of about 90% has been demonstrated with both electrical readout and
optical readout, however, the thermal limitations of the electrical readout and
the poor photon collection efficiency of the optical readout hinder achieving
the high fidelity required for quantum information applications. Here we
demonstrate a hybrid approach using optical excitation to change the charge
state of the defect centre in a silicon-based SET, conditional on its spin
state, and then detecting this change electrically. The optical frequency
addressing in high spectral resolution conquers the thermal broadening
limitation of the previous electrical readout and charge sensing avoids the
difficulties of efficient photon collection. This is done with erbium in
silicon and has the potential to enable new architectures for quantum
information processing devices and to dramatically increase the range of defect
centres that can be exploited. Further, the efficient electrical detection of
the optical excitation of single sites in silicon is a major step in developing
an interconnect between silicon and optical based quantum computing
technologies.Comment: Corrected the third affiliation. Corrected one cross-reference of
"Fig. 3b" to "Fig. 3c". Corrected the caption of Fig. 3a by changing (+-)1 to
Supervised and Unsupervised Learning of Audio Representations for Music Understanding
In this work, we provide a broad comparative analysis of strategies for
pre-training audio understanding models for several tasks in the music domain,
including labelling of genre, era, origin, mood, instrumentation, key, pitch,
vocal characteristics, tempo and sonority. Specifically, we explore how the
domain of pre-training datasets (music or generic audio) and the pre-training
methodology (supervised or unsupervised) affects the adequacy of the resulting
audio embeddings for downstream tasks.
We show that models trained via supervised learning on large-scale
expert-annotated music datasets achieve state-of-the-art performance in a wide
range of music labelling tasks, each with novel content and vocabularies. This
can be done in an efficient manner with models containing less than 100 million
parameters that require no fine-tuning or reparameterization for downstream
tasks, making this approach practical for industry-scale audio catalogs.
Within the class of unsupervised learning strategies, we show that the domain
of the training dataset can significantly impact the performance of
representations learned by the model. We find that restricting the domain of
the pre-training dataset to music allows for training with smaller batch sizes
while achieving state-of-the-art in unsupervised learning -- and in some cases,
supervised learning -- for music understanding.
We also corroborate that, while achieving state-of-the-art performance on
many tasks, supervised learning can cause models to specialize to the
supervised information provided, somewhat compromising a model's generality
Single rare-earth ions as atomic-scale probes in ultra-scaled transistors
Continued dimensional scaling of semiconductor devices has driven information
technology into vastly diverse applications. As the size of devices approaches
fundamental limits, metrology techniques with nanometre resolution and
three-dimensional (3D) capabilities are desired for device optimisation. For
example, the performance of an ultra-scaled transistor can be strongly
influenced by the local electric field and strain. Here we study the spectral
response of single erbium ions to applied electric field and strain in a
silicon ultra-scaled transistor. Stark shifts induced by both the overall
electric field and the local charge environment are observed. Further, changes
in strain smaller than are detected, which is around two
orders of magnitude more sensitive than the standard techniques used in the
semiconductor industry. These results open new possibilities for
non-destructive 3D mapping of the local strain and electric field in the
channel of ultra-scaled transistors, using the single erbium ions as
ultra-sensitive atomic probes.Comment: 10+5 pages, 4+3 figure
Sub-megahertz homogeneous linewidth for Er in Si via in situ single photon detection
We studied the optical properties of a resonantly excited trivalent Er
ensemble in Si accessed via in situ single photon detection. A novel approach
which avoids nanofabrication on the sample is introduced, resulting in a highly
efficient detection of 70 excitation frequencies, of which 63 resonances have
not been observed in literature. The center frequencies and optical lifetimes
of all resonances have been extracted, showing that 5% of the resonances are
within 1 GHz of our electrically detected resonances and that the optical
lifetimes range from 0.5 ms up to 1.5 ms. We observed inhomogeneous broadening
of less than 400 MHz and an upper bound on the homogeneous linewidth of 1.4 MHz
and 0.75 MHz for two separate resonances, which is a reduction of more than an
order of magnitude observed to date. These narrow optical transition properties
show that Er in Si is an excellent candidate for future quantum information and
communication applications.Comment: 12 pages, 13 figure
Millisecond electron spin coherence time for erbium ions in silicon
Spins in silicon that are accessible via a telecom-compatible optical
transition are a versatile platform for quantum information processing that can
leverage the well-established silicon nanofabrication industry. Key to these
applications are long coherence times on the optical and spin transitions to
provide a robust system for interfacing photonic and spin qubits. Here, we
report telecom-compatible Er3+ sites with long optical and electron spin
coherence times, measured within a nuclear spin-free silicon crystal (<0.01%
29Si) using optical detection. We investigate two sites and find 0.1 GHz
optical inhomogeneous linewidths and homogeneous linewidths below 70 kHz for
both sites. We measure the electron spin coherence time of both sites using
optically detected magnetic resonance and observe Hahn echo decay constants of
0.8 ms and 1.2 ms at around 11 mT. These optical and spin properties of Er3+:Si
are an important milestone towards using optically accessible spins in silicon
for a broad range of quantum information processing applications.Comment: 14 pages, 6 figure
Nanomechanical sensing using spins in diamond
Nanomechanical sensors and quantum nanosensors are two rapidly developing
technologies that have diverse interdisciplinary applications in biological and
chemical analysis and microscopy. For example, nanomechanical sensors based
upon nanoelectromechanical systems (NEMS) have demonstrated chip-scale mass
spectrometry capable of detecting single macromolecules, such as proteins.
Quantum nanosensors based upon electron spins of negatively-charged
nitrogen-vacancy (NV) centers in diamond have demonstrated diverse modes of
nanometrology, including single molecule magnetic resonance spectroscopy. Here,
we report the first step towards combining these two complementary technologies
in the form of diamond nanomechanical structures containing NV centers. We
establish the principles for nanomechanical sensing using such
nano-spin-mechanical sensors (NSMS) and assess their potential for mass
spectrometry and force microscopy. We predict that NSMS are able to provide
unprecedented AC force images of cellular biomechanics and to, not only detect
the mass of a single macromolecule, but also image its distribution. When
combined with the other nanometrology modes of the NV center, NSMS potentially
offer unparalleled analytical power at the nanoscale.Comment: Errors in the stress susceptibility parameters present in the
original arXiv version have been correcte
Context-dependent conservation responses to emerging wildlife diseases
Emerging infectious diseases pose an important threat to wildlife. While established protocols exist for combating outbreaks of human and agricultural pathogens, appropriate management actions before, during, and after the invasion of wildlife pathogens have not been developed. We describe stage-specific goals and management actions that minimize disease impacts on wildlife, and the research required to implement them. Before pathogen arrival, reducing the probability of introduction through quarantine and trade restrictions is key because prevention is more cost effective than subsequent responses. On the invasion front, the main goals are limiting pathogen spread and preventing establishment. In locations experiencing an epidemic, management should focus on reducing transmission and disease, and promoting the development of resistance or tolerance. Finally, if pathogen and host populations reach a stable stage, then recovery of host populations in the face of new threats is paramount. Successful management of wildlife disease requires risk-taking, rapid implementation, and an adaptive approach."Funding was provided by the US National Science Foundation (grants EF-0914866, DGE-0741448, DEB-1115069, DEB-1336290) and the National Institutes of Health (grant 1R010AI090159)."https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/14024
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