1,720,967 research outputs found
Spontaneous symmetry breaking in a SO(3) non-Abelian lattice gauge theory in 2+1D with quantum algorithms
No full textThe simulation of various properties of quantum field theories is rapidly becoming a testing ground for demonstrating the prowess of quantum algorithms. Some examples include the preparation of ground states, as well as the investigation of various simple wave packets relevant for scattering phenomena. In this work, we study the ability of quantum algorithms to prepare ground states in a matter-free non-Abelian SO(3) lattice gauge theory in 2+1D in a phase where the global charge conjugation symmetry is spontaneously broken. This is challenging for two reasons: the necessity of dealing with a large Hilbert space for gauge theories compared to that of quantum spin models, and the closing of the gap between the two ground states which becomes exponentially small as a function of the volume. To deal with the large Hilbert space of gauge fields, we demonstrate how the exact imposition of the non-Abelian Gauss Law in the rishon representation of the quantum link operator significantly reduces the degrees of freedom. Further, to resolve the gap, we introduce symmetry-guided ansätze in the Gauss-Law-resolved basis for trial states as the starting point for the quantum algorithms to prepare the two lowest energy states. In addition to simulation results for a range of two-dimensional system sizes, we also provide experimental results from the trapped-ion-based quantum hardware, IonQ, when working on systems with four quantum links. The experimental/simulation results derived from our theoretical developments indicate the role of metrics--such as the energy and the infidelity--to assess the obtained results
A qubit regularization of asymptotic freedom without fine-tuning
No full textOther than the commonly used Wilson’s regularization of quantum field theories (QFTs), there is a growing interest in regularizations that explore lattice models with a strictly finite local Hilbert space, in anticipation of the upcoming era of quantum simulations of QFTs. A notable example is Euclidean qubit regularization, which provides a natural way to recover continuum QFTs that emerge via infrared fixed points of lattice theories. Can such regularizations also capture the physics of ultraviolet fixed points? We present a novel regularization of the asymptotically free massive continuum QFT that emerges at the Berezenski-Kosterlitz-Thouless (BKT) transition through a hard core loop-gas model, discussing the advantages this model provides compared to traditional regularizations. In particular, we demonstrate that without the need for fine-tuning, it can reproduce the universal step-scaling function of the classical lattice XY model in the massive phase as we approach the phase transition
Asymptotic Freedom at the Berezinskii-Kosterlitz-Thouless Transition without Fine-Tuning Using a Qubit Regularization
No full textISSN:0031-9007ISSN:1079-7114ISSN:1079-711
Spontaneous symmetry breaking in a SO(3) non-Abelian lattice gauge theory in 2+1D with quantum algorithms
No full textThe simulation of various properties of quantum field theories is rapidly becoming a testing ground for demonstrating the prowess of quantum algorithms. Some examples include the preparation of ground states, as well as the investigation of various simple wave packets relevant for scattering phenomena. In this paper, we study the ability of quantum algorithms to prepare ground states in a matter-free non-Abelian SO(3) lattice gauge theory in 2+1D in a phase where the global charge conjugation symmetry is spontaneously broken. This is challenging for two reasons: the necessity of dealing with a large Hilbert space for gauge theories compared to that of quantum spin models, and the closing of the gap between the two ground states, which becomes exponentially small as a function of the volume. To deal with the large Hilbert space of gauge fields, we demonstrate how the exact imposition of the non-Abelian Gauss law in the rishon representation of the quantum link operator significantly reduces the degrees of freedom. Further, to resolve the gap, we introduce symmetry-guided ansätze in the Gauss-law-resolved basis for trial states as the starting point for the quantum algorithms to prepare the two lowest-energy states. In addition to simulation results for a range of two-dimensional system sizes, we also provide experimental results from the trapped-ion-based quantum hardware, IonQ, when working on systems with four quantum links. The experimental/simulation results derived from our theoretical developments indicate the role of metrics—such as the energy and the infidelity—to assess the obtained results
Engineering electrocatalyst nanosurfaces to enrich the activity by inducing lattice strain
No full textElectrocatalysis undeniably offers noteworthy improvements to future energy conversion and storage technologies, such as fuel cells, water electrolyzers, and metal-air batteries. The molecular interaction between catalytic surfaces and chemical reactants produces a trade-off between catalyst activity and effectiveness, and hence requires optimization. When enhancing electrocatalysis, atomic surface structure tuning is of primary importance in simultaneously meeting demands for electrocatalytic activity and stability. The impact of lattice strain on catalytic activity tuning is experimentally revealed in de-alloyed bimetallic nanoparticles, in which surface distortion makes essential contributions to the activities of state-of-the-art electrocatalysts that vary over distinct sizes, surface defect concentrations, shapes, and atomic compositions under the studied environments. Further, metal-rich shells show compressive strain in core-shell catalyst nanoparticles, yielding shifts in metal electronic band structure features, weakened chemisorption of oxygenated species, and changes in the mechanisms governing catalyst activity. Our study evaluates the practical and fundamental effects of surface distortion and defects on interfacial electrocatalysis, namely in the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). This is accomplished via an understanding of strain from theory, establishing reactivity-strain relationships that inform the tuning and enhancement of electrocatalytic activity and stability.11Nsciescopu
Towards the phase diagram of fermions coupled with SO(3) quantum links in (2+1)-D
No full textQuantum link models (QLMs) are generalizations of Wilson's lattice gauge theory formulated with finite-dimensional link Hilbert spaces. In certain cases, the non-Abelian Gauss Law constraint can be exactly solved, and the gauge invariant subspace embedded onto local spin Hamiltonians for efficient quantum simulation. In (1+1)d previous studies of the SO(3) QLM coupled to adjoint fermionic matter have been shown to reflect key properties of QCD and nuclear physics, including distinct confining/deconfining phases and hadronic bound states. We extend the model to (2+1)d dimensions for the first time, and report on our initial results. We review the construction of gauge-invariant state space for the proposed models, and study the single-plaquette ground state via exact-diagonalisation. We provide indications of a rich phase diagram which shows both spontaneous and explicit chiral symmetry breaking, confinement, and distinct magnetic phases characterised by different plaquette expectation values
Engineering Single Atom Catalysts to Tune Properties for Electrochemical Reduction and Evolution Reactions
No full textElectrocatalysis is important to the conversion and storage of renewable energy resources, including fuel cells, water electrolysers, and batteries. Engineering metal-based nano-architectures and their atomic-scale surfaces is a promising approach for designing electrocatalysts. Single metal atom interactions with substrates and reaction environments crucially modulate the surface electronic properties of active metal centers, yielding controllable scaling relationships and transitions between different reaction mechanisms that improve catalytic activity. Single-atom catalysts (SACs) allow activity and selectivity tuning while maintaining relatively consistent morphologies. SACs have well-defined configurations and active centers within homogeneous single-atom dispersions, producing exceptional selectivities, activities, and stabilities. Furthermore, SACs with high per-atom utilization efficiencies, well-controlled substrate compositions, and engineered surface structures develop single atom active sites for molecular reactions, enhancing mass activities. Recent developments in different metal-based SAC nanostructures are discussed to explain their remarkable bi-functional electrocatalytic activities and high mechanical flexibility, especially in the oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, hydrogen evolution reaction, and in battery applications. Existing barriers to and future insights into improving SAC performance are addressed. This study develops practical and fundamental insights on single atom electrocatalysts directed towards tuning their electrocatalytic activities and enhancing their stabilities.
Electrocatalysis is important to the conversion and storage of renewable energy resources, including fuel cells, water electrolysers, and batteries. Engineering metal-based nano-architectures and their atomic-scale surfaces is a promising approach for designing electrocatalysts. Single metal atom interactions with substrates and reaction environments crucially modulate the surface electronic properties of active metal centers, yielding controllable scaling relationships and transitions between different reaction mechanisms that improve catalytic activity. Single-atom catalysts (SACs) allow activity and selectivity tuning while maintaining relatively consistent morphologies. SACs have well-defined configurations and active centers within homogeneous single-atom dispersions, producing exceptional selectivities, activities, and stabilities. Furthermore, SACs with high per-atom utilization efficiencies, well-controlled substrate compositions, and engineered surface structures develop single atom active sites for molecular reactions, enhancing mass activities. Recent developments in different metal-based SAC nanostructures are discussed to explain their remarkable bi-functional electrocatalytic activities and high mechanical flexibility, especially in the oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, hydrogen evolution reaction, and in battery applications. Existing barriers to and future insights into improving SAC performance are addressed. This study develops practical and fundamental insights on single atom electrocatalysts directed towards tuning their electrocatalytic activities and enhancing their stabilities.11Nsciescopu
Fabrication of Sub-3 nm Feature Size Based on Block Copolymer Self-Assembly for Next-Generation Nanolithography
No full textFor Ultrahigh-density storage media and D-RAM, the feature size of lithography should be much reduced (say less than 10 nm): Though some-research groups reported feature site of 5-6 rim, further reduced feature size is needed. for next generation lithography. We synthesized, via a reversible addition-fragmentation chain-transfer polymerization, polydihydroxystyrene-block-polystyrene (PDHS-b-PS) copolymers showing lamellar and cylindrical microdomains by adjusting the volume fraction of PS block-Ups). We found that the Flory-Huggins interaction parameter (chi) between PDHS and PS was very large, 0.7 at 170 degrees C. Because of-the hugex chi, the lamellar domain spacing (L) of PDHS-b-PS with a total molecular weight of 2.1 kg mol(-1) and f(PS) = 0.5 was only 5.9, nm thus, a sub-3 nm feature size (half-pitch) was successfully obtained, Furthermore, PDHS-b-PS with a molecular weight of 4.2 kg mol(-1) and f(PS) = 0.79 showed hexagonally packed cylinders with 4 nm diameter. We also obtained thin films of PDHS-b-PS with cylindrical microdomains, showing 8.8 nm center-to-center spacing, Furthermore, we fabricated ultrahigh-density ZrO2 nanowire arrays from the cylindrical monolayer thin films via atomic layer deposition, indicating an applicability of PDHS-b-PS for next-generation lithography.1120Nsciescopu
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