63 research outputs found
Quantification of Macroscopic Quantum Superpositions within Phase Space
Based on phase-space structures of quantum states, we propose a novel measure
to quantify macroscopic quantum superpositions. Our measure simultaneously
quantifies two different kinds of essential information for a given quantum
state in a harmonious manner: the degree of quantum coherence and the effective
size of the physical system that involves the superposition. It enjoys
remarkably good analytical and algebraic properties. It turns out to be the
most general and inclusive measure ever proposed that it can be applied to any
types of multipartite states and mixed states represented in phase space.Comment: 4 pages, 1 figure, accepted for publication in Phys. Rev. Let
Effects of squeezing on quantum nonlocality of superpositions of coherent states
We analyze effects of squeezing upon superpositions of coherent states (SCSs)
and entangled coherent states (ECSs) for Bell-inequality tests. We find that
external squeezing can always increase the degrees of Bell violations, if the
squeezing direction is properly chosen, for the case of photon parity
measurements. On the other hand, when photon on/off measurements are used, the
squeezing operation can enhance the degree of Bell violations only for moderate
values of amplitudes and squeezing. We point out that a significant improvement
is required over currently available squeezed SCSs in order to directly
demonstrate a Bell-inequality violation in a real experiment.Comment: 7 pages, 4 figures, accepted for publication in Phys. Rev.
Faithful test of non-local realism with entangled coherent states
We investigate the violation of Leggett's inequality for non-local realism
using entangled coherent states and various types of local measurements. We
prove mathematically the relation between the violation of the
Clauser-Horne-Shimony-Holt form of Bell's inequality and Leggett's one when
tested by the same resources. For Leggett inequalities, we generalize the
non-local realistic bound to systems in Hilbert spaces larger than
bidimensional ones and introduce an optimization technique that allows to
achieve larger degrees of violation by adjusting the local measurement
settings. Our work describes the steps that should be performed to produce a
self-consistent generalization of Leggett's original arguments to
continuous-variable states.Comment: 8 pages, 6 figures, to be published in Phys. Rev.
Generating a Schr\"odinger-cat-like state via a coherent superposition of photonic operations
We propose an optical scheme to generate a superposition of coherent states
with enhanced size adopting an interferometric setting at the single-photon
level currently available in the laboratory. Our scheme employs a nondegenerate
optical parametric amplifier together with two beam splitters so that the
detection of single photons at the output conditionally implements the desired
superposition of second-order photonic operations. We analyze our proposed
scheme by considering realistic on-off photodetectors with nonideal efficiency
in heralding the success of conditional events. A high-quality performance of
our scheme is demonstrated in view of various criteria such as quantum
fidelity, mean output energy, and measure of quantum interference
Room-temperature InGaAs nanowire array band-edge lasers on patterned silicon-on-insulator platforms
Integration of ultracompact light sources on silicon platforms is regarded as a crucial requirement for various nanophotonic applications. In this work, InGaAs/InP core/shell nanowire array photonic crystal lasers are demon- strated on silicon-on-insulator substrates by selective-area epitaxy. 9 9 square-lattice nanowires forming photonic crystal cavities with a footprint of only 3.0 3.0 μm 2 , and a high Q factor of 23 000 are achieved by forming these nanowires on two-dimensional silicon gratings. Room-temperature lasing is observed from a fundamental band-edge mode at 1290 nm, which is the O-band of the telecommunication wavelength. Optimized growth templates and effective in-situ passivation of InGaAs nanowires enable the nanowire array to lase at a low threshold of 200 μJcm 2 , without any signature of heating or degradation above the threshold. These results represent a meaningful step toward ultracompact and monolithic III–V lasers on silicon photonic platform
Echocardiographic View Classification with Integrated Out-of-Distribution Detection for Enhanced Automatic Echocardiographic Analysis
In the rapidly evolving field of automatic echocardiographic analysis and
interpretation, automatic view classification is a critical yet challenging
task, owing to the inherent complexity and variability of echocardiographic
data. This study presents ECHOcardiography VIew Classification with
Out-of-Distribution dEtection (ECHO-VICODE), a novel deep learning-based
framework that effectively addresses this challenge by training to classify 31
classes, surpassing previous studies and demonstrating its capacity to handle a
wide range of echocardiographic views. Furthermore, ECHO-VICODE incorporates an
integrated out-of-distribution (OOD) detection function, leveraging the
relative Mahalanobis distance to effectively identify 'near-OOD' instances
commonly encountered in echocardiographic data. Through extensive
experimentation, we demonstrated the outstanding performance of ECHO-VICODE in
terms of view classification and OOD detection, significantly reducing the
potential for errors in echocardiographic analyses. This pioneering study
significantly advances the domain of automated echocardiography analysis and
exhibits promising prospects for substantial applications in extensive clinical
research and practice
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