131 research outputs found
Rectangular Photonic Crystal Nanobeam Cavities in Bulk Diamond
We demonstrate the fabrication of photonic crystal nanobeam cavities with
rectangular cross section into bulk diamond. In simulation, these cavities have
an unloaded quality factor (Q) of over 1 million. Measured cavity resonances
show fundamental modes with spectrometer-limited quality factors larger than
14,000 within 1nm of the NV center's zero phonon line at 637nm. We find high
cavity yield across the full diamond chip with deterministic resonance trends
across the fabricated parameter sweeps
Efficient Photon Coupling from a Diamond Nitrogen Vacancy Centre by Integration with Silica Fibre
A central goal in quantum information science is to efficiently interface
photons with single optical modes for quantum networking and distributed
quantum computing. Here, we introduce and experimentally demonstrate a compact
and efficient method for the low-loss coupling of a solid-state qubit, the
nitrogen vacancy (NV) centre in diamond, with a single-mode optical fibre. In
this approach, single-mode tapered diamond waveguides containing exactly one
high quality NV memory are selected and integrated on tapered silica fibres.
Numerical optimization of an adiabatic coupler indicates that
near-unity-efficiency photon transfer is possible between the two modes.
Experimentally, we find an overall collection efficiency between 18-40 % and
observe a raw single photon count rate above 700 kHz. This integrated system
enables robust, alignment-free, and efficient interfacing of single-mode
optical fibres with single photon emitters and quantum memories in solids
Two-Dimensional Photonic Crystal Slab Nanocavities on Bulk Single-Crystal Diamond
Color centers in diamond are promising spin qubits for quantum computing and
quantum networking. In photon-mediated entanglement distribution schemes, the
efficiency of the optical interface ultimately determines the scalability of
such systems. Nano-scale optical cavities coupled to emitters constitute a
robust spin-photon interface that can increase spontaneous emission rates and
photon extraction efficiencies. In this work, we introduce the fabrication of
2D photonic crystal slab nanocavities with high quality factors and cubic
wavelength mode volumes -- directly in bulk diamond. This planar platform
offers scalability and considerably expands the toolkit for classical and
quantum nanophotonics in diamond
Multiplexed control of spin quantum memories in a photonic circuit
A central goal in many quantum information processing applications is a
network of quantum memories that can be entangled with each other while being
individually controlled and measured with high fidelity. This goal has
motivated the development of programmable photonic integrated circuits (PICs)
with integrated spin quantum memories using diamond color center spin-photon
interfaces. However, this approach introduces a challenge in the microwave
control of individual spins within closely packed registers. Here, we present a
quantum-memory-integrated photonics platform capable of (i) the integration of
multiple diamond color center spins into a cryogenically compatible, high-speed
programmable PIC platform; (ii) selective manipulation of individual spin
qubits addressed via tunable magnetic field gradients; and (iii) simultaneous
control of multiple qubits using numerically optimized microwave pulse shaping.
The combination of localized optical control, enabled by the PIC platform,
together with selective spin manipulation opens the path to scalable quantum
networks on intra-chip and inter-chip platforms.Comment: 10 pages, 4 figure
InSAR observations of 2007 Tanzania rifting episode reveal mixed fault and dyke extension in an immature continental rift
In the early stages of continental rifting, extension takes place by normal faulting, while in mature continental rifts dyke intrusion dominates. Little is known about the nature of the transition between fault-controlled and dyke-controlled extension or about the processes in an intermediate setting. Here, we present observations of the temporal and spatial evolution of surface displacements during the 2007 July 14âAugust 4 rifting episode in Northern Tanzania, an immature section of the East African Rift. The ground deformation initiated with subsidence that can be attributed to âŒ40 cm of normal motion on a NE striking fault. Following July 17, deformation was dominated by the intrusion of âŒ7-km-long dyke. Dyke opening increased gradually to a total of âŒ2.4 m. From July 21, the collapse of a shallow graben above the fault dominated the near-field displacements. Comparison to the 2007 Dabbahu dyke, Afar, which occurred in a more mature rift, shows an order-of-magnitude scale difference in dyke length. Using numerical models of dyke propagation, we attribute this to the size and depth of the magma chamber; in immature rifts the thick crust and slow spreading rate favour small, deep magma chambers, forming short, buried dykes, whereas in mature rifts the thinner crust and faster spreading rate favour large, shallow magma chambers and long, erupting dykes. Observing the pattern of active processes in the East African Rift is key to understanding the development of rift systems and passive margins elsewhere
Transform-limited photons from a coherent tin-vacancy spin in diamond
Solid-state quantum emitters that couple coherent optical transitions to
long-lived spin qubits are essential for quantum networks. Here we report on
the spin and optical properties of individual tin-vacancy (SnV) centers in
diamond nanostructures. Through cryogenic magneto-optical and spin
spectroscopy, we verify the inversion-symmetric electronic structure of the
SnV, identify spin-conserving and spin-flipping transitions, characterize
transition linewidths, measure electron spin lifetimes and evaluate the spin
dephasing time. We find that the optical transitions are consistent with the
radiative lifetime limit even in nanofabricated structures. The spin lifetime
is phononlimited with an exponential temperature scaling leading to
10 ms, and the coherence time, reaches the nuclear spin-bath limit upon
cooling to 2.9 K. These spin properties exceed those of other
inversion-symmetric color centers for which similar values require millikelvin
temperatures. With a combination of coherent optical transitions and long spin
coherence without dilution refrigeration, the SnV is a promising candidate for
feasable and scalable quantum networking applications
Expression of genes for bone morphogenetic proteins BMP-2, BMP-4 and BMP-6 in various parts of the human skeleton
BACKGROUND: Differences in duration of bone healing in
various parts of the human skeleton are common experience for
orthopaedic surgeons. The reason for these differences is not obvious
and not clear.METHODS: In this paper we decided to
measure by the use of real-time RT-PCR technique the level of expression
of genes for some isoforms of bone morphogenetic proteins (BMPs), whose
role is proven in bone formation, bone induction and bone turnover.
Seven bone samples recovered from various parts of skeletons from six
cadavers of young healthy men who died in traffic accidents were
collected. Activity of genes for BMP-2, -4 and -6 was measured by the
use of fluorescent SYBR Green I.RESULTS: It was found
that expression of m-RNA for BMP-2 and BMP-4 is higher in trabecular
bone in epiphyses of long bones, cranial flat bones and corpus
mandibulae then in the compact bone of diaphyses of long bones. In all
samples examined the expression of m-RNA for BMP-4 was higher than for
BMP-2.CONCLUSION: It was shown that m-RNA for BMP-6 is
not expressed in the collected samples at all. It is postulated that
differences in the level of activation of genes for BMPs is one of the
important factors which determine the differences in duration of bone
healing of various parts of the human skeleton.Author has checked copyrightDG 16/11/1
The DOE E3SM Coupled Model Version 1: Overview and Evaluation at Standard Resolution
This work documents the first version of the U.S. Department of Energy (DOE) new Energy Exascale Earth System Model (E3SMv1). We focus on the standard resolution of the fully coupled physical model designed to address DOE mission-relevant water cycle questions. Its components include atmosphere and land (110-km grid spacing), ocean and sea ice (60Ă km in the midlatitudes and 30Ă km at the equator and poles), and river transport (55Ă km) models. This base configuration will also serve as a foundation for additional configurations exploring higher horizontal resolution as well as augmented capabilities in the form of biogeochemistry and cryosphere configurations. The performance of E3SMv1 is evaluated by means of a standard set of Coupled Model Intercomparison Project Phase 6 (CMIP6) Diagnosis, Evaluation, and Characterization of Klima simulations consisting of a long preindustrial control, historical simulations (ensembles of fully coupled and prescribed SSTs) as well as idealized CO2 forcing simulations. The model performs well overall with biases typical of other CMIP-class models, although the simulated Atlantic Meridional Overturning Circulation is weaker than many CMIP-class models. While the E3SMv1 historical ensemble captures the bulk of the observed warming between preindustrial (1850) and present day, the trajectory of the warming diverges from observations in the second half of the twentieth century with a period of delayed warming followed by an excessive warming trend. Using a two-layer energy balance model, we attribute this divergence to the modelâs strong aerosol-related effective radiative forcing (ERFari+aciĂ =Ă -1.65Ă W/m2) and high equilibrium climate sensitivity (ECSĂ =Ă 5.3Ă K).Plain Language SummaryThe U.S. Department of Energy funded the development of a new state-of-the-art Earth system model for research and applications relevant to its mission. The Energy Exascale Earth System Model version 1 (E3SMv1) consists of five interacting components for the global atmosphere, land surface, ocean, sea ice, and rivers. Three of these components (ocean, sea ice, and river) are new and have not been coupled into an Earth system model previously. The atmosphere and land surface components were created by extending existing components part of the Community Earth System Model, Version 1. E3SMv1âs capabilities are demonstrated by performing a set of standardized simulation experiments described by the Coupled Model Intercomparison Project Phase 6 (CMIP6) Diagnosis, Evaluation, and Characterization of Klima protocol at standard horizontal spatial resolution of approximately 1Ă° latitude and longitude. The model reproduces global and regional climate features well compared to observations. Simulated warming between 1850 and 2015 matches observations, but the model is too cold by about 0.5Ă Ă°C between 1960 and 1990 and later warms at a rate greater than observed. A thermodynamic analysis of the modelâs response to greenhouse gas and aerosol radiative affects may explain the reasons for the discrepancy.Key PointsThis work documents E3SMv1, the first version of the U.S. DOE Energy Exascale Earth System ModelThe performance of E3SMv1 is documented with a set of standard CMIP6 DECK and historical simulations comprising nearly 3,000Ă yearsE3SMv1 has a high equilibrium climate sensitivity (5.3Ă K) and strong aerosol-related effective radiative forcing (-1.65Ă W/m2)Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151288/1/jame20860_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151288/2/jame20860.pd
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