7,273 research outputs found
Sweeping cluster algorithm for quantum spin systems with strong geometric restrictions
Quantum spin systems with strong geometric restrictions give rise to rich
quantum phases such as valence bond solids and spin liquid states. However, the
geometric restrictions often hamper the application of sophisticated numerical
approaches. Based on the stochastic series expansion method, we develop an
efficient and exact quantum Monte Carlo "sweeping cluster" algorithm which
automatically satisfies the geometrical restrictions. Here we use the quantum
dimer model as a benchmark to demonstrate the reliability and power of this
algorithm. Comparing to existing numerical methods, we can obtain higher
accuracy results for a wider parameter region and much more substantial system
sizes
Primer: Fast Private Transformer Inference on Encrypted Data
It is increasingly important to enable privacy-preserving inference for cloud
services based on Transformers. Post-quantum cryptographic techniques, e.g.,
fully homomorphic encryption (FHE), and multi-party computation (MPC), are
popular methods to support private Transformer inference. However, existing
works still suffer from prohibitively computational and communicational
overhead. In this work, we present, Primer, to enable a fast and accurate
Transformer over encrypted data for natural language processing tasks. In
particular, Primer is constructed by a hybrid cryptographic protocol optimized
for attention-based Transformer models, as well as techniques including
computation merge and tokens-first ciphertext packing. Comprehensive
experiments on encrypted language modeling show that Primer achieves
state-of-the-art accuracy and reduces the inference latency by 90.6% ~ 97.5%
over previous methods.Comment: 6 pages, 6 figures, 3 table
TrojViT: Trojan Insertion in Vision Transformers
Vision Transformers (ViTs) have demonstrated the state-of-the-art performance
in various vision-related tasks. The success of ViTs motivates adversaries to
perform backdoor attacks on ViTs. Although the vulnerability of traditional
CNNs to backdoor attacks is well-known, backdoor attacks on ViTs are
seldom-studied. Compared to CNNs capturing pixel-wise local features by
convolutions, ViTs extract global context information through patches and
attentions. Na\"ively transplanting CNN-specific backdoor attacks to ViTs
yields only a low clean data accuracy and a low attack success rate. In this
paper, we propose a stealth and practical ViT-specific backdoor attack
. Rather than an area-wise trigger used by CNN-specific backdoor
attacks, TrojViT generates a patch-wise trigger designed to build a Trojan
composed of some vulnerable bits on the parameters of a ViT stored in DRAM
memory through patch salience ranking and attention-target loss. TrojViT
further uses minimum-tuned parameter update to reduce the bit number of the
Trojan. Once the attacker inserts the Trojan into the ViT model by flipping the
vulnerable bits, the ViT model still produces normal inference accuracy with
benign inputs. But when the attacker embeds a trigger into an input, the ViT
model is forced to classify the input to a predefined target class. We show
that flipping only few vulnerable bits identified by TrojViT on a ViT model
using the well-known RowHammer can transform the model into a backdoored one.
We perform extensive experiments of multiple datasets on various ViT models.
TrojViT can classify of test images to a target class by flipping
bits on a ViT for ImageNet.Comment: 10 pages, 4 figures, 11 table
Immunity of replicating Mu to self-integration: a novel mechanism employing MuB protein
We describe a new immunity mechanism that protects actively replicating/transposing Mu from self-integration. We show that this mechanism is distinct from the established cis-immunity mechanism, which operates by removal of MuB protein from DNA adjacent to Mu ends. MuB normally promotes integration into DNA to which it is bound, hence its removal prevents use of this DNA as target. Contrary to what might be expected from a cis-immunity mechanism, strong binding of MuB was observed throughout the Mu genome. We also show that the cis-immunity mechanism is apparently functional outside Mu ends, but that the level of protection offered by this mechanism is insufficient to explain the protection seen inside Mu. Thus, both strong binding of MuB inside and poor immunity outside Mu testify to a mechanism of immunity distinct from cis-immunity, which we call 'Mu genome immunity'. MuB has the potential to coat the Mu genome and prevent auto-integration as previously observed in vitro on synthetic A/T-only DNA, where strong MuB binding occluded the entire bound region from Mu insertions. The existence of two rival immunity mechanisms within and outside the Mu genome, both employing MuB, suggests that the replicating Mu genome must be segregated into an independent chromosomal domain. We propose a model for how formation of a 'Mu domain' may be aided by specific Mu sequences and nucleoid-associated proteins, promoting polymerization of MuB on the genome to form a barrier against self-integration
Intermediate-Mass Black Holes in Globular Clusters
There have been reports of possible detections of intermediate-mass black
holes (IMBHs) in globular clusters (GCs). Empirically, there exists a tight
correlation between the central supermassive black hole (SMBH) mass and the
mean velocity dispersion of elliptical galaxies, "pseudobulges" and classical
bulges of spiral galaxies. We explore such a possible correlation for IMBHs in
spherical GCs. In our model of self-similar general polytropic quasi-static
dynamic evolution of GCs, a criterion of forming an IMBH is proposed. The key
result is M(BH) = L o^1/(1-n) where M(BH) is the IMBH mass, o is the GC mean
stellar velocity, L is a coefficient, and 2/3 < n < 1
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