8,387 research outputs found
UniBrain: Unify Image Reconstruction and Captioning All in One Diffusion Model from Human Brain Activity
Image reconstruction and captioning from brain activity evoked by visual
stimuli allow researchers to further understand the connection between the
human brain and the visual perception system. While deep generative models have
recently been employed in this field, reconstructing realistic captions and
images with both low-level details and high semantic fidelity is still a
challenging problem. In this work, we propose UniBrain: Unify Image
Reconstruction and Captioning All in One Diffusion Model from Human Brain
Activity. For the first time, we unify image reconstruction and captioning from
visual-evoked functional magnetic resonance imaging (fMRI) through a latent
diffusion model termed Versatile Diffusion. Specifically, we transform fMRI
voxels into text and image latent for low-level information and guide the
backward diffusion process through fMRI-based image and text conditions derived
from CLIP to generate realistic captions and images. UniBrain outperforms
current methods both qualitatively and quantitatively in terms of image
reconstruction and reports image captioning results for the first time on the
Natural Scenes Dataset (NSD) dataset. Moreover, the ablation experiments and
functional region-of-interest (ROI) analysis further exhibit the superiority of
UniBrain and provide comprehensive insight for visual-evoked brain decoding
Assisted optimal state discrimination without entanglement
A fundamental problem in quantum information is to explore the roles of
different quantum correlations in a quantum information procedure. Recent work
[Phys. Rev. Lett., 107 (2011) 080401] shows that the protocol for assisted
optimal state discrimination (AOSD) may be implemented successfully without
entanglement, but with another correlation, quantum dissonance. However, both
the original work and the extension to discrimination of states [Phys. Rev.
A, 85 (2012) 022328] have only proved that entanglement can be absent in the
case with equal a \emph{priori} probabilities. By improving the protocol in
[Sci. Rep., 3 (2013) 2134], we investigate this topic in a simple case to
discriminate three nonorthogonal states of a qutrit, with positive real
overlaps. In our procedure, the entanglement between the qutrit and an
auxiliary qubit is found to be completely unnecessary. This result shows that
the quantum dissonance may play as a key role in optimal state discrimination
assisted by a qubit for more general cases.Comment: 6 pages, 3 figures. Accepted by EPL. We extended the protocol for
assisted optimal state discrimination to the case with positive real
overlaps, and presented a proof for the absence of entanglemen
Most robust and fragile two-qubit entangled states under depolarizing channels
For a two-qubit system under local depolarizing channels, the most robust and
most fragile states are derived for a given concurrence or negativity. For the
one-sided channel, the pure states are proved to be the most robust ones, with
the aid of the evolution equation for entanglement given by Konrad et al. [Nat.
Phys. 4, 99 (2008)]. Based on a generalization of the evolution equation for
entanglement, we classify the ansatz states in our investigation by the amount
of robustness, and consequently derive the most fragile states. For the
two-sided channel, the pure states are the most robust for a fixed concurrence.
Under the uniform channel, the most fragile states have the minimal negativity
when the concurrence is given in the region [1/2,1]. For a given negativity,
the most robust states are the ones with the maximal concurrence, and the most
fragile ones are the pure states with minimum of concurrence. When the
entanglement approaches zero, the most fragile states under general nonuniform
channels tend to the ones in the uniform channel. Influences on robustness by
entanglement, degree of mixture, and asymmetry between the two qubits are
discussed through numerical calculations. It turns out that the concurrence and
negativity are major factors for the robustness. When they are fixed, the
impact of the mixedness becomes obvious. In the nonuniform channels, the most
fragile states are closely correlated with the asymmetry, while the most robust
ones with the degree of mixture.Comment: 10 pages, 9 figs. to appear in Quantum Information & Computation
(QIC
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