2,613 research outputs found
High-dimensional frequency conversion in hot atomic system
One of the major difficulties in realizing a high-dimensional frequency
converter for conventional optical vortex (COV) stems from the difference in
ring diameter of COV modes with different topological charge numbers l. Here,
we implement a high-dimensional frequency convertor for perfect optical vortex
(POV) modes with invariant size through the four-wave mixing (FWM) process by
utilizing Bessel-Gaussian beams instead of Laguerre-Gaussian beams. The
measured conversion efficiency from 1530 nm to 795 nm is independent of l at
least in subspace of {-6,...,6}, and the achieved conversion fidelities for
two-dimensional (2D) superposed POV states exceed 97%. We further realize the
frequency conversion of 3D, 5D and 7D superposition states with fidelities as
high as 96.70%, 89.16% and 88.68%, respectively. The reported scheme is
implemented in hot atomic vapor, it's also compatible with the cold atomic
system and may find applications in high-capacity and long-distance quantum
communication
Detection of infrared light through stimulated four-wave mixing process
Infrared optical measurement has a wide range of applications in industry and
science, but infrared light detectors suffer from high costs and inferior
performance than visible light detectors. Four-wave mixing (FWM) process allows
detection in the infrared range by detecting correlated visible light. We
experimentally investigate the stimulated FWM process in a hot Rb atomic
vapor cell, in which a weak infrared signal laser at nm induces the FWM
process and is amplified and converted into a strong FWM light at nm, the
latter can be detected more easily. We find the optimized single- and
two-photon detunings by studying the dependence of the frequency of input laser
on the generated FWM light. What's more, the power gain increases rapidly as
the signal intensity decreases, which is consistent with our theoretical
analysis. As a result, the power gain can reach up to 500 at a signal laser
power of W and the number of detected photons increased by a factor of
250. Finally, we experimentally prove that our amplification process can work
in a broad band in the frequency domain by exploring the response rate of our
stimulated FWM process.Comment: 4 figure
Optical Memory for Arbitrary Perfect Poincar\'e States in an Atomic Ensemble
Inherent spin angular momentum (SAM) and orbital angular momentum (OAM) which
manifest as polarization and spatial degrees of freedom (DOF) of photons, hold
a promise of large capability for applications in classical and quantum
information processing. To enable these photonic spin and orbital dynamic
properties strongly coupled with each other, Poincar\'{e} states have been
proposed and offer advantages in data multiplexing, information encryption,
precision metrology, and quantum memory. However, since the transverse size of
Laguerre Gaussian beams strongly depends on their topological charge numbers
, it is difficult to store asymmetric Poincar\'{e} states due
to the significantly different light-matter interaction for distinct spatial
modes. Here, we experimentally realize the storage of perfect Poincar\'{e}
states with arbitrary OAM quanta using the perfect optical vortex, in which 121
arbitrarily-selected perfect Poincar\'{e} states have been stored with high
fidelity. The reported work has great prospects in optical communication and
quantum networks for dramatically increased encoding flexibility of
information
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A Systems Engineering Framework that Integrates Aircraft Final Assembly Design Activities
A modern large-scaled aircraft consists of numerous structural and system components. Many of those components are installed and tested in the final assembly stage. To design the aircraft final assembly processes, engineers are required to have a comprehensive understanding of the interdependences and interactions between all the aircraft components, and the following influence to manufacturing operations. This work is difficult and challenging due to final assembly design activities lie in both product design and operations management fields. Final assembly processes link to product and operations constraints, thus a process-oriented method is required. Aircraft as a typical system of systems, systems engineering framework, for instance the V model, is used to understand the product complicities and guide the product design activities. However, there is no such a framework for final assembly line (FAL) process. This research investigates the activities of aircraft integrations at final assembly stage, then introduces a framework following Systems Engineering (SE) principles for integrating FAL design activities
Flexible online task assignment in real-time spatial data
The popularity of Online To Offline (O2O) service platforms has spurred the need for online task assignment in real-time spatial data, where streams of spatially distributed tasks and workers are matched in real time such that the total number of assigned pairs is maximized. Existing online task assignment models assume that each worker is either assigned a task immediately or waits for a subsequent task at a fixed location once she/he appears on the platform. Yet in practice a worker may actively move around rather than passively wait in place if no task is assigned. In this paper, we define a new problem Flexible Two-sided Online task Assignment (FTOA). FTOA aims to guide idle workers based on the prediction of tasks and workers so as to increase the total number of assigned worker-task pairs. To address the FTOA problem, we face two challenges: (i) How to generate guidance for idle workers based on the prediction of the spatiotemporal distribution of tasks and workers? (ii) How to leverage the guidance of workers’ movements to optimize the online task assignment? To this end, we propose a novel two-step framework, which integrates offline prediction and online task assignment. Specifically, we estimate the distributions of tasks and workers per time slot and per unit area, and design an online task assignment algorithm, Prediction-oriented Online task Assignment in Real-time spatial data (POLAR-OP). It yields a 0.47-competitive ratio, which is nearly twice better than that of the state-of-the-art. POLAR-OP also reduces the time complexity to process each newly-arrived task/worker to O(1). We validate the effectiveness and efficiency of our methods via extensive experiments on both synthetic datasets and real-world datasets from a large-scale taxi-calling platform.ISSN:2150-809
Experimental realization of quantum non-reciprocity based on cold atomic ensembles
In analog to counterparts widely used in electronic circuits, all optical
non-reciprocal devices are basic building blocks for both classical and quantum
optical information processing. Approaching the fundamental limit of such
devices, where the propagation of a single photon exhibits a good
non-reciprocal characteristic, requires an asymmetric strong coupling between a
single photon and a matter. Unfortunately it has been not realized yet. Here,
we propose and experimentally realize a quantum non-reciprocity device with low
optical losses and a high isolation of larger than 14 dB based on the cold
atoms. Besides, the non-reciprocal transmission of a quantum qubit and
non-reciprocal quantum storage of a true single photon are also realized. All
results achieved would be very promising in building up quantum non-reciprocal
devices for quantum networks.Comment: 7 pages, 4 figure
Screening and evaluating of long noncoding RNAs in the puberty of goats
GO analysis of predicted targets of lncRNAs in trans. (XLS 1551 kb
Smad7 enables STAT3 activation and promotes pluripotency independent of TGF-β signaling
TGF-β and related growth factors critically regulate cell potency and functions. Smad7 is induced by TGF-βs and inhibits the physiological functions of TGF-β signaling. This study describes an unexpected finding that Smad7 promotes self-renewal of embryonic stem cells (ESCs) in a manner independent of its inhibition on TGF-β signaling. Instead, Smad7 acts to induce activation of transcription factor signal transducers and activators of transcription 3 (STAT3) in ESCs. Smad7 activates STAT3 through its direct binding to the cytokine receptor upstream of STAT3 activation. In agreement with the role of STAT3 in maintaining ESC pluripotency, Smad7 promotes ESC self-renewal and induced pluripotent stem cell reprogramming. This finding illustrates a regulatory mechanism for Smad7 in maintaining pluripotency, and likely in cancer and inflammation
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