ABSTRACT: This paper describes the performance evaluation and analysis of a set of open source petascale quantum simulation tools for nanotechnology applications. The tools of interest are based on the existing realspace multigrid (RMG) method. In this work we take a reference set of these tools and evaluate their performance with the help of performance evaluation libraries and tools such as TAU and PAPI. The goal is to develop an in-depth understanding of their performance on Teraflop leadership platforms, and moreover identify possible bottlenecks and give suggestions for their removal. The measurements are being done on ORNL’s Cray XT4 system (Jaguar) based on quad-core 2.1 GHz AMD Opteron processors. Profiling is being used to identify possible performance bottlenecks and tracing is being used to try to determine the exact locations and causes of those bottlenecks. The results so far indicate that the methodology followed can be used to easily produce and analyze performance data, and that this ability has the potential to aid our overall efforts on developing efficient quantum simulation tools for petascale systems. KEYWORDS: performance evaluation, petascale tools, quantum simulations, TAU, PAPI. 1
This topical review describes the methodology of continuum variational and diffusion quantum Monte Carlo calculations. These stochastic methods are based on many-body wavefunctions and are capable of achieving very high accuracy. The algorithms are intrinsically parallel and well suited to implementation on petascale computers, and the computational cost scales as a polynomial in the number of particles. A guide to the systems and topics which have been investigated using these methods is given. The bulk of the article is devoted to an overview of the basic quantum Monte Carlo methods, the forms and optimization of wavefunctions, performing calculations under periodic boundary conditions, using pseudopotentials, excited-state calculations, sources of calculational inaccuracy, and calculating energy differences and forces.
As demand for quantum technologies increases, so does the need to generate and classify non-classical correlations in complex many-body systems. We introduce a simple and versatile method for creating and certifying entanglement and many-body Bell correlations. This method relies on a single qubit interacting with an
N-qubit system. We demonstrate that: (i) such pairwise interaction is sufficient to induce many-body quantum correlations, and (ii) the qubit can serve as a probe to extract all information about these correlations. Thus, single-qubit measurements reveal multi-partite entanglement and
N-body Bell correlations, enabling the rapid and efficient certification of non-classicality in complex systems.
As demand for quantum technologies increases, so does the need to generate and classify nonclassical correlations in complex many-body systems. We introduce a simple and versatile method for creating and certifying entanglement and many-body Bell correlations. This method relies on a single qubit interacting with an N-qubit system. We demonstrate that (i) such pairwise interaction is sufficient to induce many-body quantum correlations, and (ii) the qubit can serve as a probe to extract all information about these correlations. Thus, single-qubit measurements reveal multipartite entanglement and N-body Bell correlations, enabling the rapid and efficient certification of nonclassicality in complex systems.