207 research outputs found
Bichromatic field generation from double-four-wave mixing in a double-electromagnetically induced transparency system
We demonstrate the double electromagnetically induced transparency
(double-EIT) and double four-wave mixing (double-FWM) based on a new scheme of
non-degenerate four-wave mixing (FWM) involving five levels of a cold 85Rb
atomic ensemble, in which the double-EIT windows are used to transmit the probe
field and enhance the third-order nonlinear susceptibility. The phase-matching
conditions for both four-wave mixings could be satisfied simultaneously. The
frequency of one component of the generated bichromatic field is less than the
other by the ground-state hyperfine splitting (3GHz). This specially designed
experimental scheme for simultaneously generating different nonlinear
wave-mixing processes is expected to find applications in quantum information
processing and cross phase modulation. Our results agree well with the
theoretical simulation.Comment: Accepted by NJ
Last-Iterate Convergent Policy Gradient Primal-Dual Methods for Constrained MDPs
We study the problem of computing an optimal policy of an infinite-horizon
discounted constrained Markov decision process (constrained MDP). Despite the
popularity of Lagrangian-based policy search methods used in practice, the
oscillation of policy iterates in these methods has not been fully understood,
bringing out issues such as violation of constraints and sensitivity to
hyper-parameters. To fill this gap, we employ the Lagrangian method to cast a
constrained MDP into a constrained saddle-point problem in which max/min
players correspond to primal/dual variables, respectively, and develop two
single-time-scale policy-based primal-dual algorithms with non-asymptotic
convergence of their policy iterates to an optimal constrained policy.
Specifically, we first propose a regularized policy gradient primal-dual
(RPG-PD) method that updates the policy using an entropy-regularized policy
gradient, and the dual via a quadratic-regularized gradient ascent,
simultaneously. We prove that the policy primal-dual iterates of RPG-PD
converge to a regularized saddle point with a sublinear rate, while the policy
iterates converge sublinearly to an optimal constrained policy. We further
instantiate RPG-PD in large state or action spaces by including function
approximation in policy parametrization, and establish similar sublinear
last-iterate policy convergence. Second, we propose an optimistic policy
gradient primal-dual (OPG-PD) method that employs the optimistic gradient
method to update primal/dual variables, simultaneously. We prove that the
policy primal-dual iterates of OPG-PD converge to a saddle point that contains
an optimal constrained policy, with a linear rate. To the best of our
knowledge, this work appears to be the first non-asymptotic policy last-iterate
convergence result for single-time-scale algorithms in constrained MDPs.Comment: 78 pages, 17 figures, and 1 tabl
Highly efficient vortex four-wave mixing in asymmetric semiconductor quantum wells
© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement Orbital angular momentum (OAM) is an important property of vortex light, which provides a valuable tool to manipulate the light-matter interaction in the study of classical and quantum optics. Here we propose a scheme to generate vortex light fields via four-wave mixing (FWM) in asymmetric semiconductor quantum wells. By tailoring the probe-field and control-field detunings, we can effectively manipulate the helical phase and intensity of the FWM field. Particularly, when probe field and control field have identical detuning, we find that both the absorption and phase twist of the generated FWM field are significantly suppressed. Consequently, the highly efficient vortex FWM is realized, where the maximum conversion efficiency reaches around 50%. Our study provides a tool to transfer vortex wavefronts from input to output fields in an efficient way, which may find potential applications in solid-state quantum optics and quantum information processing
Provably Efficient Generalized Lagrangian Policy Optimization for Safe Multi-Agent Reinforcement Learning
We examine online safe multi-agent reinforcement learning using constrained
Markov games in which agents compete by maximizing their expected total rewards
under a constraint on expected total utilities. Our focus is confined to an
episodic two-player zero-sum constrained Markov game with independent
transition functions that are unknown to agents, adversarial reward functions,
and stochastic utility functions. For such a Markov game, we employ an approach
based on the occupancy measure to formulate it as an online constrained
saddle-point problem with an explicit constraint. We extend the Lagrange
multiplier method in constrained optimization to handle the constraint by
creating a generalized Lagrangian with minimax decision primal variables and a
dual variable. Next, we develop an upper confidence reinforcement learning
algorithm to solve this Lagrangian problem while balancing exploration and
exploitation. Our algorithm updates the minimax decision primal variables via
online mirror descent and the dual variable via projected gradient step and we
prove that it enjoys sublinear rate for
both regret and constraint violation after playing episodes of the game.
Here, is the horizon of each episode, and are the
state/action space sizes of the min-player and the max-player, respectively. To
the best of our knowledge, we provide the first provably efficient online safe
reinforcement learning algorithm in constrained Markov games.Comment: 59 pages, a full version of the main paper in the 5th Annual
Conference on Learning for Dynamics and Contro
Self-Evolution Learning for Mixup: Enhance Data Augmentation on Few-Shot Text Classification Tasks
Text classification tasks often encounter few shot scenarios with limited
labeled data, and addressing data scarcity is crucial. Data augmentation with
mixup has shown to be effective on various text classification tasks. However,
most of the mixup methods do not consider the varying degree of learning
difficulty in different stages of training and generate new samples with one
hot labels, resulting in the model over confidence. In this paper, we propose a
self evolution learning (SE) based mixup approach for data augmentation in text
classification, which can generate more adaptive and model friendly pesudo
samples for the model training. SE focuses on the variation of the model's
learning ability. To alleviate the model confidence, we introduce a novel
instance specific label smoothing approach, which linearly interpolates the
model's output and one hot labels of the original samples to generate new soft
for label mixing up. Through experimental analysis, in addition to improving
classification accuracy, we demonstrate that SE also enhances the model's
generalize ability
Meta-analysis of the association between dietary inflammatory index and cognitive health
BackgroundSome studies have shown that a pro-inflammatory diet may be associated with cognitive function, but their conclusions have varied considerably. We here present a meta-analysis of the current published literature on DII score and its association with cognitive health.MethodsIn this meta-analysis, the PubMed, Embase, Web of Science, and Cochrane databases were searched in September 2022. The reported indexes, specifically OR, RR, and β, were extracted and analyzed using R version 3.1.0.ResultsA total of 636 studies in databases were identified, and 12 were included in the meta-analysis. Higher DII was associated with an increased risk of AD and MCI (OR = 1.34; 95% CI = 1.21–1.49). Meanwhile, it may also cause global function impairment (categorical: OR = 1.63; 95% CI = 1.36–1.96) and verbal fluency impairment (continuous: OR = 0.18; 95% IC = 0.08–0.42). But there was no significant association between DII and executive function (categorical: OR = 1.12; 95% IC = 0.84–1.49; continuous: OR = 0.48; 95% IC = 0.19–1.21) or episodic memory (continuous: OR = 0.56; 95% IC = 0.30–1.03).ConclusionA pro-inflammatory diet is related to AD, MCI, and the functions of some cognitive domains (specifically global function and verbal fluency). However, the current evidence on the role of diet-induced inflammation in different cognitive domains should be supported by further studies in the future
NIPD: A Federated Learning Person Detection Benchmark Based on Real-World Non-IID Data
Federated learning (FL), a privacy-preserving distributed machine learning,
has been rapidly applied in wireless communication networks. FL enables
Internet of Things (IoT) clients to obtain well-trained models while preventing
privacy leakage. Person detection can be deployed on edge devices with limited
computing power if combined with FL to process the video data directly at the
edge. However, due to the different hardware and deployment scenarios of
different cameras, the data collected by the camera present non-independent and
identically distributed (non-IID), and the global model derived from FL
aggregation is less effective. Meanwhile, existing research lacks public data
set for real-world FL object detection, which is not conducive to studying the
non-IID problem on IoT cameras. Therefore, we open source a non-IID IoT person
detection (NIPD) data set, which is collected from five different cameras. To
our knowledge, this is the first true device-based non-IID person detection
data set. Based on this data set, we explain how to establish a FL experimental
platform and provide a benchmark for non-IID person detection. NIPD is expected
to promote the application of FL and the security of smart city.Comment: 8 pages, 5 figures, 3 tables, FL-IJCAI 23 conferenc
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