13 research outputs found
Orbital Expansion Variational Quantum Eigensolver: Enabling Efficient Simulation of Molecules with Shallow Quantum Circuit
In the noisy-intermediate-scale-quantum era, Variational Quantum Eigensolver
(VQE) is a promising method to study ground state properties in quantum
chemistry, materials science, and condensed physics. However, general quantum
eigensolvers are lack of systematical improvability, and achieve rigorous
convergence is generally hard in practice, especially in solving
strong-correlated systems. Here, we propose an Orbital Expansion VQE~(OE-VQE)
framework to construct an efficient convergence path. The path starts from a
highly correlated compact active space and rapidly expands and converges to the
ground state, enabling simulating ground states with much shallower quantum
circuits. We benchmark the OE-VQE on a series of typical molecules including
H-chain, H-ring and N, and the simulation results show that
proposed convergence paths dramatically enhance the performance of general
quantum eigensolvers.Comment: Wu et al 2023 Quantum Sci. Techno
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
Inorganic Salt Hydrate for Thermal Energy Storage
Using phase change materials (PCMs) for thermal energy storage has always been a hot topic within the research community due to their excellent performance on energy conservation such as energy efficiency in buildings, solar domestic hot water systems, textile industry, biomedical and food agroindustry. Several literatures have reported phase change materials concerning various aspects. Among these materials, salt hydrates are worthy of exploring due to their high-energy storage density, rational price, multiple sources and relatively good thermal conductivity. This paper reviews the present state of salt hydrates PCMs targeting classification, properties, defects, possible solutions as well as their idiographic features which are suitable for applications. In addition, new trends of future research are also indicated
Ultrathin 2D Fe-Nanosheets Stabilized by 2D Mesoporous Silica: Synthesis and Application in Ammonia Synthesis
Developing high-performance Fe-based ammonia catalysts through simple and cost-efficient methods has received an increased level of attention. Herein, we report for the first time, the synthesis of two-dimensional (2D) FeOOH nanoflakes encapsulated by mesoporous SiO2 (mSiO2) via a simple solution-based method for ammonia synthesis. Due to the sticking of the mSiO2 coating layers and the limited spaces in between, the Fe after reduction retains the 2D morphology, showing high resistance against the sintering in the harsh Haber–Bosch process. Compared to supported Fe particles dispersed on mSiO2 spheres, the coated catalyst shows a significantly improved catalytic activity by 50% at 425 °C. Thermal desorption spectroscopy (TDS) reveals the existence of a higher density of reactive sites for N2 activation in the 2D Fe catalyst, which is possibly coupled to a larger density of surface defect sites (kinks, steps, point defects) that are generally considered as active centers in ammonia synthesis. Besides the structural impact of the coating on the 2D Fe, the electronic one is elucidated by partially substituting Si with Al in the coating, confirmed by 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR). An increased apparent activation energy (Ea) of the Al-containing catalyst evidences an influence on the nature of the active site. The herein-developed stable 2D Fe nanostructures can serve as an example of a 2D material applied in catalysis, offering the chance of a rational catalyst design based on a stepwise introduction of various promoters, in the coating and on the metal, maintaining the spatial control of the active centers