146 research outputs found
Quantum entanglement and teleportation in pulsed cavity-optomechanics
Entangling a mechanical oscillator with an optical mode is an enticing and
yet a very challenging goal in cavity optomechanics. Here we consider a pulsed
scheme to create Einstein-Podolsky-Rosen-type entanglement between a
traveling-wave light pulse and a mechanical oscillator. The entanglement can be
verified unambiguously by a pump-probe sequence of pulses. In contrast to
schemes that work in a steady-state regime under a continuous-wave drive, this
protocol is not subject to stability requirements that normally limit the
strength of achievable entanglement. We investigate the protocol's performance
under realistic conditions, including mechanical decoherence, in full detail.
We discuss the relevance of a high mechanical Qf product for entanglement
creation and provide a quantitative statement on which magnitude of the Qf
product is necessary for a successful realization of the scheme. We determine
the optimal parameter regime for its operation and show it to work in current
state-of-the-art systems.Comment: 10 pages, 2 figure
Radiation-pressure self-cooling of a micromirror in a cryogenic environment
We demonstrate radiation-pressure cavity-cooling of a mechanical mode of a
micromirror starting from cryogenic temperatures. To achieve that, a
high-finesse Fabry-Perot cavity (F\approx 2200) was actively stabilized inside
a continuous-flow 4He cryostat. We observed optical cooling of the fundamental
mode of a 50mu x 50 mu x 5.4 mu singly-clamped micromirror at \omega_m=3.5 MHz
from 35 K to approx. 290 mK. This corresponds to a thermal occupation factor of
\approx 1x10^4. The cooling performance is only limited by the mechanical
quality and by the optical finesse of the system. Heating effects, e.g. due to
absorption of photons in the micromirror, could not be observed. These results
represent a next step towards cavity-cooling a mechanical oscillator into its
quantum ground state
A microchip optomechanical accelerometer
The monitoring of accelerations is essential for a variety of applications
ranging from inertial navigation to consumer electronics. The basic operation
principle of an accelerometer is to measure the displacement of a flexibly
mounted test mass; sensitive displacement measurement can be realized using
capacitive, piezo-electric, tunnel-current, or optical methods. While optical
readout provides superior displacement resolution and resilience to
electromagnetic interference, current optical accelerometers either do not
allow for chip-scale integration or require bulky test masses. Here we
demonstrate an optomechanical accelerometer that employs ultra-sensitive
all-optical displacement read-out using a planar photonic crystal cavity
monolithically integrated with a nano-tethered test mass of high mechanical
Q-factor. This device architecture allows for full on-chip integration and
achieves a broadband acceleration resolution of 10 \mu g/rt-Hz, a bandwidth
greater than 20 kHz, and a dynamic range of 50 dB with sub-milliwatt optical
power requirements. Moreover, the nano-gram test masses used here allow for
optomechanical back-action in the form of cooling or the optical spring effect,
setting the stage for a new class of motional sensors.Comment: 16 pages, 9 figure
Hybrid Mechanical Systems
We discuss hybrid systems in which a mechanical oscillator is coupled to
another (microscopic) quantum system, such as trapped atoms or ions,
solid-state spin qubits, or superconducting devices. We summarize and compare
different coupling schemes and describe first experimental implementations.
Hybrid mechanical systems enable new approaches to quantum control of
mechanical objects, precision sensing, and quantum information processing.Comment: To cite this review, please refer to the published book chapter (see
Journal-ref and DOI). This v2 corresponds to the published versio
Master Equation for the Motion of a Polarizable Particle in a Multimode Cavity
We derive a master equation for the motion of a polarizable particle weakly
interacting with one or several strongly pumped cavity modes. We focus here on
massive particles with complex internal structure such as large molecules and
clusters, for which we assume a linear scalar polarizability mediating the
particle-light interaction. The predicted friction and diffusion coefficients
are in good agreement with former semiclassical calculations for atoms and
small molecules in weakly pumped cavities, while the current rigorous quantum
treatment and numerical assessment sheds a light on the feasibility of
experiments that aim at optically manipulating beams of massive molecules with
multimode cavities.Comment: 30 pages, 5 figure
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CYP2C19 Genotype Prevalence and Association With Recurrent Myocardial Infarction in British-South Asians Treated With Clopidogrel.
BACKGROUND: Cytochrome P450 family 2 subfamily C member 19 (CYP2C19) is a hepatic enzyme involved in the metabolism of clopidogrel from a prodrug to its active metabolite. Prior studies of genetic polymorphisms in CYP2C19 and their relationship with clinical efficacy have not included South Asian populations. OBJECTIVES: The objective of this study was to assess prevalence of common CYP2C19 genotype polymorphisms in a British-South Asian population and correlate these with recurrent myocardial infarction risk in participants prescribed clopidogrel. METHODS: The Genes & Health cohort of British Bangladeshi and Pakistani ancestry participants were studied. CYP2C19 diplotypes were assessed using array data. Multivariable logistic regression was used to test for association between genetically inferred CYP2C19 metabolizer status and recurrent myocardial infarction, controlling for known cardiovascular disease risk factors, percutaneous coronary intervention, age, sex, and population stratification. RESULTS: Genes & Health cohort participants (N = 44,396) have a high prevalence (57%) of intermediate or poor CYP2C19 metabolizers, with at least 1 loss-of-function CYP2C19 allele. The prevalence of poor metabolizers carrying 2 CYP2C19 loss-of-function alleles is 13%, which is higher than that in previously studied European (2.4%) and Central/South Asian populations (8.2%). Sixty-nine percent of the cohort who were diagnosed with an acute myocardial infarction were prescribed clopidogrel. Poor metabolizers were significantly more likely to have a recurrent myocardial infarction (OR: 3.1; P = 0.019). CONCLUSIONS: A pharmacogenomic-driven approach to clopidogrel prescribing has the potential to impact significantly on clinical management and outcomes in individuals of Bangladeshi and Pakistani ancestry
Multimode circuit optomechanics near the quantum limit
The coupling of distinct systems underlies nearly all physical phenomena and
their applications. A basic instance is that of interacting harmonic
oscillators, which gives rise to, for example, the phonon eigenmodes in a
crystal lattice. Particularly important are the interactions in hybrid quantum
systems consisting of different kinds of degrees of freedom. These assemblies
can combine the benefits of each in future quantum technologies. Here, we
investigate a hybrid optomechanical system having three degrees of freedom,
consisting of a microwave cavity and two micromechanical beams with closely
spaced frequencies around 32 MHz and no direct interaction. We record the first
evidence of tripartite optomechanical mixing, implying that the eigenmodes are
combinations of one photonic and two phononic modes. We identify an asymmetric
dark mode having a long lifetime. Simultaneously, we operate the nearly
macroscopic mechanical modes close to the motional quantum ground state, down
to 1.8 thermal quanta, achieved by back-action cooling. These results
constitute an important advance towards engineering entangled motional states.Comment: 6+7 page
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Genome-wide trans-ancestry meta-analysis provides insight into the genetic architecture of type 2 diabetes susceptibility.
To further understanding of the genetic basis of type 2 diabetes (T2D) susceptibility, we aggregated published meta-analyses of genome-wide association studies (GWAS), including 26,488 cases and 83,964 controls of European, east Asian, south Asian and Mexican and Mexican American ancestry. We observed a significant excess in the directional consistency of T2D risk alleles across ancestry groups, even at SNPs demonstrating only weak evidence of association. By following up the strongest signals of association from the trans-ethnic meta-analysis in an additional 21,491 cases and 55,647 controls of European ancestry, we identified seven new T2D susceptibility loci. Furthermore, we observed considerable improvements in the fine-mapping resolution of common variant association signals at several T2D susceptibility loci. These observations highlight the benefits of trans-ethnic GWAS for the discovery and characterization of complex trait loci and emphasize an exciting opportunity to extend insight into the genetic architecture and pathogenesis of human diseases across populations of diverse ancestry
Characteristics of evidence-based medicine training in Royal College of Physicians and Surgeons of Canada emergency medicine residencies - a national survey of program directors
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