547 research outputs found
Linear and nonlinear optical spectroscopy of a strongly-coupled microdisk-quantum dot system
A fiber taper waveguide is used to perform direct optical spectroscopy of a
microdisk-quantum-dot system, exciting the system through the photonic (light)
channel rather than the excitonic (matter) channel. Strong coupling, the regime
of coherent quantum interactions, is demonstrated through observation of vacuum
Rabi splitting in the transmitted and reflected signals from the cavity. The
fiber coupling method also allows the examination of the system's steady-state
nonlinear properties, where saturation of the cavity-QD response is observed
for less than one intracavity photon.Comment: adjusted references, added minor clarification
Quantum nature of a strongly-coupled single quantum dot-cavity system
Cavity quantum electrodynamics (QED) studies the interaction between a
quantum emitter and a single radiation-field mode. When an atom is in strong
coupling with a cavity mode1,2, it is possible to realize key quantum
information processing (QIP) tasks, such as controlled coherent coupling and
entanglement of distinguishable quantum systems. Realizing these tasks in the
solid state is clearly desirable, and coupling semiconductor self-assembled
quantum dots (QDs) to monolithic optical cavities is a promising route to this
end. However, validating the efficacy of QDs in QIP applications requires
confirmation of the quantum nature of the QD-cavity system in the strong
coupling regime. Here we find a confirmation by observing quantum correlations
in photoluminescence (PL) from a photonic crystal (PC) nanocavity3-5
interacting with one, and only one, QD located precisely at the cavity electric
field maximum. When off-resonance, photon emission from the cavity mode and QD
excitons is anti-correlated at the level of single quanta, proving that the
mode is driven solely by the QD despite an energy mis-match between cavity and
excitons. When tuned into resonance, the exciton and photon enter the
strong-coupling regime of cavity-QED and the QD lifetime reduces by a factor of
120. The photon stream from the cavity becomes anti-bunched, proving that the
coupled exciton/photon system is in the quantum anharmonic regime. Our
observations unequivocally show that QIP tasks requiring the quantum nonlinear
regime are achievable in the solid state.Comment: 14 pages 4 figure
Chemotherapy-Response Monitoring of Breast Cancer Patients Using Quantitative Ultrasound-Based Intra-Tumour Heterogeneities
© 2017 The Author(s). Anti-cancer therapies including chemotherapy aim to induce tumour cell death. Cell death introduces alterations in cell morphology and tissue micro-structures that cause measurable changes in tissue echogenicity. This study investigated the effectiveness of quantitative ultrasound (QUS) parametric imaging to characterize intra-tumour heterogeneity and monitor the pathological response of breast cancer to chemotherapy in a large cohort of patients (n = 100). Results demonstrated that QUS imaging can non-invasively monitor pathological response and outcome of breast cancer patients to chemotherapy early following treatment initiation. Specifically, QUS biomarkers quantifying spatial heterogeneities in size, concentration and spacing of acoustic scatterers could predict treatment responses of patients with cross-validated accuracies of 82 ± 0.7%, 86 ± 0.7% and 85 ± 0.9% and areas under the receiver operating characteristic (ROC) curve of 0.75 ± 0.1, 0.80 ± 0.1 and 0.89 ± 0.1 at 1, 4 and 8 weeks after the start of treatment, respectively. The patients classified as responders and non-responders using QUS biomarkers demonstrated significantly different survivals, in good agreement with clinical and pathological endpoints. The results form a basis for using early predictive information on survival-linked patient response to facilitate adapting standard anti-cancer treatments on an individual patient basis
Automated Analysis of Craniofacial Morphology Using Magnetic Resonance Images
Quantitative analysis of craniofacial morphology is of interest to scholars
working in a wide variety of disciplines, such as anthropology, developmental
biology, and medicine. T1-weighted (anatomical) magnetic resonance images (MRI)
provide excellent contrast between soft tissues. Given its three-dimensional
nature, MRI represents an ideal imaging modality for the analysis of
craniofacial structure in living individuals. Here we describe how T1-weighted
MR images, acquired to examine brain anatomy, can also be used to analyze facial
features. Using a sample of typically developing adolescents from the Saguenay
Youth Study (N = 597; 292 male, 305 female, ages: 12 to 18
years), we quantified inter-individual variations in craniofacial structure in
two ways. First, we adapted existing nonlinear registration-based morphological
techniques to generate iteratively a group-wise population average of
craniofacial features. The nonlinear transformations were used to map the
craniofacial structure of each individual to the population average. Using
voxel-wise measures of expansion and contraction, we then examined the effects
of sex and age on inter-individual variations in facial features. Second, we
employed a landmark-based approach to quantify variations in face surfaces. This
approach involves: (a) placing 56 landmarks (forehead, nose, lips, jaw-line,
cheekbones, and eyes) on a surface representation of the MRI-based group
average; (b) warping the landmarks to the individual faces using the inverse
nonlinear transformation estimated for each person; and (3) using a principal
components analysis (PCA) of the warped landmarks to identify facial features
(i.e. clusters of landmarks) that vary in our sample in a correlated fashion. As
with the voxel-wise analysis of the deformation fields, we examined the effects
of sex and age on the PCA-derived spatial relationships between facial features.
Both methods demonstrated significant sexual dimorphism in craniofacial
structure in areas such as the chin, mandible, lips, and nose
Ultrafast all-optical switching by single photons
An outstanding goal in quantum optics is the realization of fast optical
non-linearities at the single-photon level. Such non-linearities would allow
for the realization of optical devices with new functionalities such as a
single-photon switch/transistor or a controlled-phase gate, which could form
the basis of future quantum optical technologies. While non-linear optics
effects at the single-emitter level have been demonstrated in different
systems, including atoms coupled to Fabry-Perot or toroidal micro-cavities,
super-conducting qubits in strip-line resonators or quantum dots (QDs) in
nano-cavities, none of these experiments so far has demonstrated single-photon
switching on ultrafast timescales. Here, we demonstrate that in a strongly
coupled QD-cavity system the presence of a single photon on one of the
fundamental polariton transitions can turn on light scattering on a transition
from the first to the second Jaynes-Cummings manifold with a switching time of
20 ps. As an additional device application, we use this non-linearity to
implement a single-photon pulse-correlator. Our QD-cavity system could form the
building-block of future high-bandwidth photonic networks operating in the
quantum regime
Photonic quantum technologies
The first quantum technology, which harnesses uniquely quantum mechanical
effects for its core operation, has arrived in the form of commercially
available quantum key distribution systems that achieve enhanced security by
encoding information in photons such that information gained by an eavesdropper
can be detected. Anticipated future quantum technologies include large-scale
secure networks, enhanced measurement and lithography, and quantum information
processors, promising exponentially greater computation power for particular
tasks. Photonics is destined for a central role in such technologies owing to
the need for high-speed transmission and the outstanding low-noise properties
of photons. These technologies may use single photons or quantum states of
bright laser beams, or both, and will undoubtably apply and drive
state-of-the-art developments in photonics
Higher-order multipole amplitudes in charmonium radiative transitions
Using 24 million decays in CLEO-c, we have searched
for higher multipole admixtures in electric-dipole-dominated radiative
transitions in charmonia. We find good agreement between our data and
theoretical predictions for magnetic quadrupole (M2) amplitudes in the
transitions and ,
in striking contrast to some previous measurements. Let and
denote the normalized M2 amplitudes in the respective aforementioned decays,
where the superscript refers to the angular momentum of the . By
performing unbinned maximum likelihood fits to full five-parameter angular
distributions, we determine the ratios and , where
the theoretical predictions are independent of the charmed quark magnetic
moment and are and .Comment: 32 pages, 7 figures, acceptance updat
Dalitz Plot Analysis of Ds to K+K-pi+
We perform a Dalitz plot analysis of the decay Ds to K+K-pi+ with the CLEO-c
data set of 586/pb of e+e- collisions accumulated at sqrt(s) = 4.17 GeV. This
corresponds to about 0.57 million D_s+D_s(*)- pairs from which we select 14400
candidates with a background of roughly 15%. In contrast to previous
measurements we find good agreement with our data only by including an
additional f_0(1370)pi+ contribution. We measure the magnitude, phase, and fit
fraction of K*(892) K+, phi(1020)pi+, K0*(1430)K+, f_0(980)pi+, f_0(1710)pi+,
and f_0(1370)pi+ contributions and limit the possible contributions of other KK
and Kpi resonances that could appear in this decay.Comment: 21 Pages,available through http://www.lns.cornell.edu/public/CLNS/,
submitted to PR
Search for D0 to p e- and D0 to pbar e+
Using data recorded by CLEO-c detector at CESR, we search for simultaneous
baryon and lepton number violating decays of the D^0 meson, specifically, D^0
--> p-bar e^+, D^0-bar --> p-bar e^+, D^0 --> p e^- and D^0-bar --> p e^-. We
set the following branching fraction upper limits: D^0 --> p-bar e^+ (D^0-bar
--> p-bar e^+) p e^- (D^0-bar --> p e^-) < 1.2 *
10^{-5}, both at 90% confidence level.Comment: 10 pages, available through http://www.lns.cornell.edu/public/CLNS/,
submitted to PRD. Comments: changed abstract, added reference for section 1,
vertical axis in Fig.5 changed (starts from 1.5 rather than 2.0), fixed typo
Charmonium decays to gamma pi0, gamma eta, and gamma eta'
Using data acquired with the CLEO-c detector at the CESR e+e- collider, we
measure branching fractions for J/psi, psi(2S), and psi(3770) decays to gamma
pi0, gamma eta, and gamma eta'. Defining R_n = B[ psi(nS)-->gamma eta ]/B[
psi(nS)-->gamma eta' ], we obtain R_1 = (21.1 +- 0.9)% and, unexpectedly, an
order of magnitude smaller limit, R_2 < 1.8% at 90% C.L. We also use
J/psi-->gamma eta' events to determine branching fractions of improved
precision for the five most copious eta' decay modes.Comment: 14 pages, available through http://www.lns.cornell.edu/public/CLNS/,
published in Physical Review
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