23,446 research outputs found
Simulating dynamical quantum Hall effect with superconducting qubits
We propose an experimental scheme to simulate the dynamical quantum Hall
effect and the related interaction-induced topological transition with a
superconducting-qubit array. We show that a one-dimensional Heisenberg model
with tunable parameters can be realized in an array of superconducting qubits.
The quantized plateaus, which is a feature of the dynamical quantum Hall
effect, will emerge in the Berry curvature of the superconducting qubits as a
function of the coupling strength between nearest neighbor qubits. We
numerically calculate the Berry curvatures of two-, four- and six-qubit arrays,
and find that the interaction-induced topological transition can be easily
observed with the simplest two-qubit array. Furthermore, we analyze some
practical conditions in typical experiments for observing such dynamical
quantum Hall effect.Comment: 9 pages, 6 figures, version accepted by PR
Linear Convergence of Adaptively Iterative Thresholding Algorithms for Compressed Sensing
This paper studies the convergence of the adaptively iterative thresholding
(AIT) algorithm for compressed sensing. We first introduce a generalized
restricted isometry property (gRIP). Then we prove that the AIT algorithm
converges to the original sparse solution at a linear rate under a certain gRIP
condition in the noise free case. While in the noisy case, its convergence rate
is also linear until attaining a certain error bound. Moreover, as by-products,
we also provide some sufficient conditions for the convergence of the AIT
algorithm based on the two well-known properties, i.e., the coherence property
and the restricted isometry property (RIP), respectively. It should be pointed
out that such two properties are special cases of gRIP. The solid improvements
on the theoretical results are demonstrated and compared with the known
results. Finally, we provide a series of simulations to verify the correctness
of the theoretical assertions as well as the effectiveness of the AIT
algorithm.Comment: 15 pages, 5 figure
IRGAN: A Minimax Game for Unifying Generative and Discriminative Information Retrieval Models
This paper provides a unified account of two schools of thinking in
information retrieval modelling: the generative retrieval focusing on
predicting relevant documents given a query, and the discriminative retrieval
focusing on predicting relevancy given a query-document pair. We propose a game
theoretical minimax game to iteratively optimise both models. On one hand, the
discriminative model, aiming to mine signals from labelled and unlabelled data,
provides guidance to train the generative model towards fitting the underlying
relevance distribution over documents given the query. On the other hand, the
generative model, acting as an attacker to the current discriminative model,
generates difficult examples for the discriminative model in an adversarial way
by minimising its discrimination objective. With the competition between these
two models, we show that the unified framework takes advantage of both schools
of thinking: (i) the generative model learns to fit the relevance distribution
over documents via the signals from the discriminative model, and (ii) the
discriminative model is able to exploit the unlabelled data selected by the
generative model to achieve a better estimation for document ranking. Our
experimental results have demonstrated significant performance gains as much as
23.96% on Precision@5 and 15.50% on MAP over strong baselines in a variety of
applications including web search, item recommendation, and question answering.Comment: 12 pages; appendix adde
The Radiation Structure of PSR B201628 Observed with FAST
With the largest dish Five-hundred-meter Aperture Spherical radio Telescope
(FAST), both the mean and single pulses of PSR B201628, especially including
the single-pulse structure, are investigated in detail in this study. The mean
pulse profiles at different frequencies can be well fitted in a conal model,
and the peak separation of intensity-dependent pulse profiles increases with
intensity. The integrated pulses are obviously frequency dependent (pulse width
decreases by as frequency increases from 300 MHz to 750 MHz), but
the structure of single pulses changes slightly (the corresponding correlation
scale decreases by only ). This disparity between mean and single
pulses provides independent evidence for the existence of the RS-type vacuum
inner gap, indicating a strong bond between particles on the pulsar surface.
Diffused drifting sub-pulses are analyzed. The results show that the modulation
period along pulse series () is positively correlated to the separation
between two adjacent sub-pulses (). This correlation may hint a rough
surface on the pulsar, eventually resulting in the irregular drift of sparks.
All the observational results may have significant implications in the dynamics
of pulsar magnetosphere and are discussed extensively in this paper.Comment: Sci. China-Phys. Mech. Astron. 62, 959505 (2019
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