199 research outputs found
Dynamics of quantum-classical hybrid system: effect of matter-wave pressure
Radiation pressure affects the kinetics of a system exposed to the radiation
and it constitutes the basis of laser cooling. In this paper, we study {\it
matter-wave pressure} through examining the dynamics of a quantum-classical
hybrid system. The quantum and classical subsystem have no explicit coupling to
each other, but affect mutually via a changing boundary condition. Two systems,
i.e., an atom and a Bose-Einstein condensate(BEC), are considered as the
quantum subsystems, while an oscillating wall is taken as the classical
subsystem. We show that the classical subsystem would experience a force
proportional to from the quantum atom, whereas it acquires an
additional force proportional to from the BEC due to the atom-atom
interaction in the BEC. These forces can be understood as the {\it matter-wave
pressure}.Comment: 7 pages, 6 figue
Simple and Efficient Partial Graph Adversarial Attack: A New Perspective
As the study of graph neural networks becomes more intensive and
comprehensive, their robustness and security have received great research
interest. The existing global attack methods treat all nodes in the graph as
their attack targets. Although existing methods have achieved excellent
results, there is still considerable space for improvement. The key problem is
that the current approaches rigidly follow the definition of global attacks.
They ignore an important issue, i.e., different nodes have different robustness
and are not equally resilient to attacks. From a global attacker's view, we
should arrange the attack budget wisely, rather than wasting them on highly
robust nodes. To this end, we propose a totally new method named partial graph
attack (PGA), which selects the vulnerable nodes as attack targets. First, to
select the vulnerable items, we propose a hierarchical target selection policy,
which allows attackers to only focus on easy-to-attack nodes. Then, we propose
a cost-effective anchor-picking policy to pick the most promising anchors for
adding or removing edges, and a more aggressive iterative greedy-based attack
method to perform more efficient attacks. Extensive experimental results
demonstrate that PGA can achieve significant improvements in both attack effect
and attack efficiency compared to other existing graph global attack methods
DIFER: Differentiable Automated Feature Engineering
Feature engineering, a crucial step of machine learning, aims to extract
useful features from raw data to improve data quality. In recent years, great
efforts have been devoted to Automated Feature Engineering (AutoFE) to replace
expensive human labor. However, existing methods are computationally demanding
due to treating AutoFE as a coarse-grained black-box optimization problem over
a discrete space. In this work, we propose an efficient gradient-based method
called DIFER to perform differentiable automated feature engineering in a
continuous vector space. DIFER selects potential features based on evolutionary
algorithm and leverages an encoder-predictor-decoder controller to optimize
existing features. We map features into the continuous vector space via the
encoder, optimize the embedding along the gradient direction induced by the
predicted score, and recover better features from the optimized embedding by
the decoder. Extensive experiments on classification and regression datasets
demonstrate that DIFER can significantly improve the performance of various
machine learning algorithms and outperform current state-of-the-art AutoFE
methods in terms of both efficiency and performance.Comment: 8 pages, 5 figure
- …