642 research outputs found
IsoBN: Fine-Tuning BERT with Isotropic Batch Normalization
Fine-tuning pre-trained language models (PTLMs), such as BERT and its better
variant RoBERTa, has been a common practice for advancing performance in
natural language understanding (NLU) tasks. Recent advance in representation
learning shows that isotropic (i.e., unit-variance and uncorrelated) embeddings
can significantly improve performance on downstream tasks with faster
convergence and better generalization. The isotropy of the pre-trained
embeddings in PTLMs, however, is relatively under-explored. In this paper, we
analyze the isotropy of the pre-trained [CLS] embeddings of PTLMs with
straightforward visualization, and point out two major issues: high variance in
their standard deviation, and high correlation between different dimensions. We
also propose a new network regularization method, isotropic batch normalization
(IsoBN) to address the issues, towards learning more isotropic representations
in fine-tuning by dynamically penalizing dominating principal components. This
simple yet effective fine-tuning method yields about 1.0 absolute increment on
the average of seven NLU tasks.Comment: AAAI 202
Quantum Pseudoentanglement
Quantum pseudorandom states are efficiently constructable states which
nevertheless masquerade as Haar-random states to poly-time observers. First
defined by Ji, Liu and Song, such states have found a number of applications
ranging from cryptography to the AdS/CFT correspondence. A fundamental question
is exactly how much entanglement is required to create such states. Haar-random
states, as well as -designs for , exhibit near-maximal
entanglement. Here we provide the first construction of pseudorandom states
with only polylogarithmic entanglement entropy across an equipartition of the
qubits, which is the minimum possible. Our construction can be based on any
one-way function secure against quantum attack. We additionally show that the
entanglement in our construction is fully "tunable", in the sense that one can
have pseudorandom states with entanglement for any desired
function .
More fundamentally, our work calls into question to what extent entanglement
is a "feelable" quantity of quantum systems. Inspired by recent work of
Gheorghiu and Hoban, we define a new notion which we call "pseudoentanglement",
which are ensembles of efficiently constructable quantum states which hide
their entanglement entropy. We show such states exist in the strongest form
possible while simultaneously being pseudorandom states. We also describe
diverse applications of our result from entanglement distillation to property
testing to quantum gravity.Comment: 32 page
Multiple-Change-Point Modeling and Exact Bayesian Inference of Degradation Signal for Prognostic Improvement
Prognostics play an increasingly important role in modern engineering systems for smart maintenance decision-making. In parametric regression-based approaches, the parametric models are often too rigid to model degradation signals in many applications. In this paper, we propose a Bayesian multiple-change-point (CP) modeling framework to better capture the degradation path and improve the prognostics. At the offline modeling stage, a novel stochastic process is proposed to model the joint prior of CPs and positions. All hyperparameters are estimated through an empirical two-stage process. At the online monitoring and remaining useful life (RUL) prediction stage, a recursive updating algorithm is developed to exactly calculate the posterior distribution and RUL prediction sequentially. To control the computational cost, a fixed-support-size strategy in the online model updating and a partial Monte Carlo strategy in the RUL prediction are proposed. The effectiveness and advantages of the proposed method are demonstrated through thorough simulation and real case studies
A signal cascade originated from epidermis defines apical-basal patterning of Arabidopsis shoot apical meristems
In multicellular organisms, a long-standing question is how spatial patterns of distinct cell types are initiated and maintained during continuous cell division and proliferation. Along the vertical axis of plant shoot apical meristems (SAMs), stem cells are located at the top while cells specifying the stem cells are located more basally, forming a robust apical-basal pattern. We previously found that in Arabidopsis SAMs, the HAIRY MERISTEM (HAM) family transcription factors form a concentration gradient from the epidermis to the interior cell layers, and this gradient is essential for the stem cell specification and the apical-basal patterning of the SAMs. Here, we uncover that epidermis specific transcription factors, ARABIDOPSIS THALIANA MERISTEM LAYER 1 (ATML1) and its close homolog, define the concentration gradient of HAM in the SAM through activating a group of microRNAs. This study provides a molecular framework linking the epidermis-derived signal to the stem cell homeostasis in plants
Public-key pseudoentanglement and the hardness of learning ground state entanglement structure
Given a local Hamiltonian, how difficult is it to determine the entanglement
structure of its ground state? We show that this problem is computationally
intractable even if one is only trying to decide if the ground state is
volume-law vs near area-law entangled. We prove this by constructing strong
forms of pseudoentanglement in a public-key setting, where the circuits used to
prepare the states are public knowledge. In particular, we construct two
families of quantum circuits which produce volume-law vs near area-law
entangled states, but nonetheless the classical descriptions of the circuits
are indistinguishable under the Learning with Errors (LWE) assumption.
Indistinguishability of the circuits then allows us to translate our
construction to Hamiltonians. Our work opens new directions in Hamiltonian
complexity, for example whether it is difficult to learn certain phases of
matter.Comment: 58 page
A universal high energy anomaly in angle resolved photoemission spectra of high temperature superconductors - possible evidence of spinon and holon branches
A universal high energy anomaly in the single particle spectral function is
reported in three different families of high temperature superconductors by
using angle-resolved photoemission spectroscopy. As we follow the dispersing
peak of the spectral function from the Fermi energy to the valence band
complex, we find dispersion anomalies marked by two distinctive high energy
scales, E_1=~ 0.38 eV and E_2=~0.8 eV. E_1 marks the energy above which the
dispersion splits into two branches. One is a continuation of the near
parabolic dispersion, albeit with reduced spectral weight, and reaches the
bottom of the band at the gamma point at ~0.5 eV. The other is given by a peak
in the momentum space, nearly independent of energy between E_1 and E_2. Above
E_2, a band-like dispersion re-emerges. We conjecture that these two energies
mark the disintegration of the low energy quasiparticles into a spinon and
holon branch in the high T_c cuprates.Comment: accepted for publication in Phys. Rev. Let
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