45 research outputs found
Correlations and Pair Formation in a Repulsively Interacting Fermi Gas
A degenerate Fermi gas is rapidly quenched into the regime of strong
effective repulsion near a Feshbach resonance. The spin fluctuations are
monitored using speckle imaging and, contrary to several theoretical
predictions, the samples remain in the paramagnetic phase for arbitrarily large
scattering length. Over a wide range of interaction strengths a rapid decay
into bound pairs is observed over times on the order of 10\hbar/E_F, preventing
the study of equilibrium phases of strongly repulsive fermions. Our work
suggests that a Fermi gas with strong short-range repulsive interactions does
not undergo a ferromagnetic phase transition
Spin-Orbit Coupling and Spin Textures in Optical Superlattices
We proposed and demonstrated a new approach for realizing spin orbit coupling
with ultracold atoms. We use orbital levels in a double well potential as
pseudospin states. Two-photon Raman transitions between left and right wells
induce spin-orbit coupling. This scheme does not require near resonant light,
features adjustable interactions by shaping the double well potential, and does
not depend on special properties of the atoms. A pseudospinor Bose-Einstein
condensate spontaneously acquires an antiferromagnetic pseudospin texture which
breaks the lattice symmetry similar to a supersolid
Speckle Imaging of Spin Fluctuations in a Strongly Interacting Fermi Gas
Spin fluctuations and density fluctuations are studied for a two-component
gas of strongly interacting fermions along the BEC-BCS crossover. This is done
by in-situ imaging of dispersive speckle patterns. Compressibility and magnetic
susceptibility are determined from the measured fluctuations. This new
sensitive method easily resolves a tenfold suppression of spin fluctuations
below shot noise due to pairing, and can be applied to novel magnetic phases in
optical lattices
Suppression of Density Fluctuations in a Quantum Degenerate Fermi Gas
We study density profiles of an ideal Fermi gas and observe Pauli suppression
of density fluctuations (atom shot noise) for cold clouds deep in the quantum
degenerate regime. Strong suppression is observed for probe volumes containing
more than 10,000 atoms. Measuring the level of suppression provides sensitive
thermometry at low temperatures. After this method of sensitive noise
measurements has been validated with an ideal Fermi gas, it can now be applied
to characterize phase transitions in strongly correlated many-body systems.Comment: minor edit: fixed technical problem with arxiv's processing of .eps
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Neurogenesis Dynamics-inspired Spiking Neural Network Training Acceleration
Biologically inspired Spiking Neural Networks (SNNs) have attracted
significant attention for their ability to provide extremely energy-efficient
machine intelligence through event-driven operation and sparse activities. As
artificial intelligence (AI) becomes ever more democratized, there is an
increasing need to execute SNN models on edge devices. Existing works adopt
weight pruning to reduce SNN model size and accelerate inference. However,
these methods mainly focus on how to obtain a sparse model for efficient
inference, rather than training efficiency. To overcome these drawbacks, in
this paper, we propose a Neurogenesis Dynamics-inspired Spiking Neural Network
training acceleration framework, NDSNN. Our framework is computational
efficient and trains a model from scratch with dynamic sparsity without
sacrificing model fidelity. Specifically, we design a new drop-and-grow
strategy with decreasing number of non-zero weights, to maintain extreme high
sparsity and high accuracy. We evaluate NDSNN using VGG-16 and ResNet-19 on
CIFAR-10, CIFAR-100 and TinyImageNet. Experimental results show that NDSNN
achieves up to 20.52\% improvement in accuracy on Tiny-ImageNet using ResNet-19
(with a sparsity of 99\%) as compared to other SOTA methods (e.g., Lottery
Ticket Hypothesis (LTH), SET-SNN, RigL-SNN). In addition, the training cost of
NDSNN is only 40.89\% of the LTH training cost on ResNet-19 and 31.35\% of the
LTH training cost on VGG-16 on CIFAR-10
PolyMPCNet: Towards ReLU-free Neural Architecture Search in Two-party Computation Based Private Inference
The rapid growth and deployment of deep learning (DL) has witnessed emerging
privacy and security concerns. To mitigate these issues, secure multi-party
computation (MPC) has been discussed, to enable the privacy-preserving DL
computation. In practice, they often come at very high computation and
communication overhead, and potentially prohibit their popularity in large
scale systems. Two orthogonal research trends have attracted enormous interests
in addressing the energy efficiency in secure deep learning, i.e., overhead
reduction of MPC comparison protocol, and hardware acceleration. However, they
either achieve a low reduction ratio and suffer from high latency due to
limited computation and communication saving, or are power-hungry as existing
works mainly focus on general computing platforms such as CPUs and GPUs.
In this work, as the first attempt, we develop a systematic framework,
PolyMPCNet, of joint overhead reduction of MPC comparison protocol and hardware
acceleration, by integrating hardware latency of the cryptographic building
block into the DNN loss function to achieve high energy efficiency, accuracy,
and security guarantee. Instead of heuristically checking the model sensitivity
after a DNN is well-trained (through deleting or dropping some non-polynomial
operators), our key design principle is to em enforce exactly what is assumed
in the DNN design -- training a DNN that is both hardware efficient and secure,
while escaping the local minima and saddle points and maintaining high
accuracy. More specifically, we propose a straight through polynomial
activation initialization method for cryptographic hardware friendly trainable
polynomial activation function to replace the expensive 2P-ReLU operator. We
develop a cryptographic hardware scheduler and the corresponding performance
model for Field Programmable Gate Arrays (FPGA) platform
AutoReP: Automatic ReLU Replacement for Fast Private Network Inference
The growth of the Machine-Learning-As-A-Service (MLaaS) market has
highlighted clients' data privacy and security issues. Private inference (PI)
techniques using cryptographic primitives offer a solution but often have high
computation and communication costs, particularly with non-linear operators
like ReLU. Many attempts to reduce ReLU operations exist, but they may need
heuristic threshold selection or cause substantial accuracy loss. This work
introduces AutoReP, a gradient-based approach to lessen non-linear operators
and alleviate these issues. It automates the selection of ReLU and polynomial
functions to speed up PI applications and introduces distribution-aware
polynomial approximation (DaPa) to maintain model expressivity while accurately
approximating ReLUs. Our experimental results demonstrate significant accuracy
improvements of 6.12% (94.31%, 12.9K ReLU budget, CIFAR-10), 8.39% (74.92%,
12.9K ReLU budget, CIFAR-100), and 9.45% (63.69%, 55K ReLU budget,
Tiny-ImageNet) over current state-of-the-art methods, e.g., SNL. Morever,
AutoReP is applied to EfficientNet-B2 on ImageNet dataset, and achieved 75.55%
accuracy with 176.1 times ReLU budget reduction.Comment: ICCV 2023 accepeted publicatio