Comparing Performance of Variational Quantum Algorithm Simulations on HPC Systems

Variational quantum algorithms are of special importance in the research on quantum computing applications because of their applicability to current Noisy Intermediate-Scale Quantum (NISQ) devices. The main building blocks of these algorithms define a relatively large parameter space, making the comparison of results and performance between different approaches and software simulators cumbersome and prone to errors. In this paper, we employ a generic description of the problem, in terms of both Hamiltonian and ansatz, to consistently port a problem definition across different simulators. A use case relevant to current quantum hardware has been run on a set of HPC systems and software simulators to study the dependence of performance on the runtime environment, the scalability of the simulation codes, and the agreement between the physical results, respectively. The results show that our toolchain can successfully translate a problem definition between different simulators. On the other hand, variational algorithms are limited in their scaling by the long runtimes with respect to their memory footprint, so they expose limited parallelism to computation. This shortcoming is partially mitigated by using techniques like job arrays. The potential of the parser tool within the toolchain for exploring HPC performance and comparisons of results of variational algorithm simulations is highlighted.