318 research outputs found
Engineering Photon Delocalization in a Rabi Dimer with a Dissipative Bath
A Rabi dimer is used to model a recently reported circuit quantum
electrodynamics system composed of two coupled transmission-line resonators
with each coupled to one qubit. In this study, a phonon bath is adopted to
mimic the multimode micromechanical resonators and is coupled to the qubits in
the Rabi dimer. The dynamical behavior of the composite system is studied by
the Dirac-Frenkel time-dependent variational principle combined with the
multiple Davydov D ans\"{a}tze. Initially all the photons are pumped into
the left resonator, and the two qubits are in the down state coupled with the
phonon vacuum. In the strong qubit-photon coupling regime, the photon dynamics
can be engineered by tuning the qubit-bath coupling strength and
photon delocalization is achieved by increasing . In the absence of
dissipation, photons are localized in the initial resonator. Nevertheless, with
moderate qubit-bath coupling, photons are delocalized with quasiequilibration
of the photon population in two resonators at long times. In this case, high
frequency bath modes are activated by interacting with depolarized qubits. For
strong dissipation, photon delocalization is achieved via frequent
photon-hopping within two resonators and the qubits are suppressed in their
initial down state.Comment: 11 pages, 11 figure
Synthesis of ultrathin platinum nanoplates for enhanced oxygen reduction activity.
Ultrathin Pt nanostructures exposing controlled crystal facets are highly desirable for their superior activity and cost-effectiveness in the electrocatalytic oxygen reduction reaction (ORR), and they are conventionally synthesized by epitaxial growth of Pt on a limited range of templates, such as Pd nanocrystals, resulting in a high cost and less structural diversity of the ultrathin Pt nanostructures. To solve this problem, we demonstrate that ultrathin Pt nanostructures can be synthesized by templating conveniently available Ag nanocrystals without involving galvanic replacement, which enables a much-reduced cost and controllable new morphologies, such as ultrathin Pt nanoplates that expose the {111} facets. The resulting ultrathin Pt nanoplates are ∼1-2 nm in thickness, which show an ∼22-fold increase in specific activity (5.3 mA cm-2), an ∼9.5-fold increase in mass activity (1.62 A mg-1) and significantly enhanced catalytic stability in the ORR, compared with the commercial Pt/C catalyst. We believe this strategy opens a door to a highly extendable family of ultrathin noble metal nanostructures, thus promising excellent activity and stability in a broad range of catalytic applications
Efficient RLHF: Reducing the Memory Usage of PPO
Reinforcement Learning with Human Feedback (RLHF) has revolutionized language
modeling by aligning models with human preferences. However, the RL stage,
Proximal Policy Optimization (PPO), requires over 3x the memory of Supervised
Fine-Tuning (SFT), making it infeasible to use for most practitioners. To
address this issue, we present a comprehensive analysis the memory usage,
performance, and training time of memory-savings techniques for PPO. We
introduce Hydra-RLHF by first integrating the SFT and Reward models and then
dynamically turning LoRA "off" during training. Our experiments show: 1. Using
LoRA during PPO reduces its memory usage to be smaller than SFT while improving
alignment across four public benchmarks, and 2. Hydra-PPO reduces the latency
per sample of LoRA-PPO by up to 65% while maintaining its performance. Our
results demonstrate that Hydra-PPO is a simple and promising solution for
enabling more widespread usage of RLHF
Adapting LLM Agents Through Communication
Recent advancements in large language models (LLMs) have shown potential for
human-like agents. To help these agents adapt to new tasks without extensive
human supervision, we propose the Learning through Communication (LTC)
paradigm, a novel training approach enabling LLM agents to improve continuously
through interactions with their environments and other agents. Recent
advancements in large language models (LLMs) have shown potential for
human-like agents. To help these agents adapt to new tasks without extensive
human supervision, we propose the Learning through Communication (LTC)
paradigm, a novel training approach enabling LLM agents to improve continuously
through interactions with their environments and other agents. Through
iterative exploration and PPO training, LTC empowers the agent to assimilate
short-term experiences into long-term memory. To optimize agent interactions
for task-specific learning, we introduce three structured communication
patterns: Monologue, Dialogue, and Analogue-tailored for common tasks such as
decision-making, knowledge-intensive reasoning, and numerical reasoning. We
evaluated LTC on three datasets: ALFWorld (decision-making), HotpotQA
(knowledge-intensive reasoning), and GSM8k (numerical reasoning). On ALFWorld,
it exceeds the instruction tuning baseline by 12% in success rate. On HotpotQA,
LTC surpasses the instruction-tuned LLaMA-7B agent by 5.1% in EM score, and it
outperforms the instruction-tuned 9x larger PaLM-62B agent by 0.6%. On GSM8k,
LTC outperforms the CoT-Tuning baseline by 3.6% in accuracy. The results
showcase the versatility and efficiency of the LTC approach across diverse
domains. We will open-source our code to promote further development of the
community.Comment: Preprin
Magnetic properties of undoped Cu2O fine powders with magnetic impurities and/or cation vacancies
Fine powders of micron- and submicron-sized particles of undoped Cu2O
semiconductor, with three different sizes and morphologies have been
synthesized by different chemical processes. These samples include nanospheres
200 nm in diameter, octahedra of size 1 micron, and polyhedra of size 800 nm.
They exhibit a wide spectrum of magnetic properties. At low temperature, T = 5
K, the octahedron sample is diamagnetic. The nanosphere is paramagnetic. The
other two polyhedron samples synthesized in different runs by the same process
are found to show different magnetic properties. One of them exhibits weak
ferromagnetism with T_C = 455 K and saturation magnetization, M_S = 0.19 emu/g
at T = 5 K, while the other is paramagnetic. The total magnetic moment
estimated from the detected impurity concentration of Fe, Co, and Ni, is too
small to account for the observed magnetism by one to two orders of magnitude.
Calculations by the density functional theory (DFT) reveal that cation
vacancies in the Cu2O lattice are one of the possible causes of induced
magnetic moments. The results further predict that the defect-induced magnetic
moments favour a ferromagnetically coupled ground state if the local
concentration of cation vacancies, n_C, exceeds 12.5%. This offers a possible
scenario to explain the observed magnetic properties. The limitations of the
investigations in the present work, in particular in the theoretical
calculations, are discussed and possible areas for further study are suggested.Comment: 20 pages, 5 figures 2 tables, submitted to J Phys Condense Matte
Towards Automating Precision Studies of Clone Detectors
Current research in clone detection suffers from poor ecosystems for
evaluating precision of clone detection tools. Corpora of labeled clones are
scarce and incomplete, making evaluation labor intensive and idiosyncratic, and
limiting inter tool comparison. Precision-assessment tools are simply lacking.
We present a semi-automated approach to facilitate precision studies of clone
detection tools. The approach merges automatic mechanisms of clone
classification with manual validation of clone pairs. We demonstrate that the
proposed automatic approach has a very high precision and it significantly
reduces the number of clone pairs that need human validation during precision
experiments. Moreover, we aggregate the individual effort of multiple teams
into a single evolving dataset of labeled clone pairs, creating an important
asset for software clone research.Comment: Accepted to be published in the 41st ACM/IEEE International
Conference on Software Engineerin
In-Context Learning Unlocked for Diffusion Models
We present Prompt Diffusion, a framework for enabling in-context learning in
diffusion-based generative models. Given a pair of task-specific example
images, such as depth from/to image and scribble from/to image, and a text
guidance, our model automatically understands the underlying task and performs
the same task on a new query image following the text guidance. To achieve
this, we propose a vision-language prompt that can model a wide range of
vision-language tasks and a diffusion model that takes it as input. The
diffusion model is trained jointly over six different tasks using these
prompts. The resulting Prompt Diffusion model is the first diffusion-based
vision-language foundation model capable of in-context learning. It
demonstrates high-quality in-context generation on the trained tasks and
generalizes effectively to new, unseen vision tasks with their respective
prompts. Our model also shows compelling text-guided image editing results. Our
framework, with code publicly available at
https://github.com/Zhendong-Wang/Prompt-Diffusion, aims to facilitate research
into in-context learning for computer vision
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