Quantum simulator design and exploration with open source matrix product state codes

On the way to universal quantum computing, quantum simulators, specialized quantum computers built on a wide variety of experimental architectures, have already been a huge success and are fulfilling Feynman's original 1982 vision of quantum computing. Each such simulator, of which there are over 300 worldwide presently, requires a dedicated experimental platform and costs on the order of several million dollars to build. Such experiments have many interacting parts often requiring a complex rearrangement and months of work in order to perform a specified quantum computation. A widely accessible and easy to use software tool to shortcut design considerations for quantum simulator experimentalists is much needed. We have created such a tool, OpenMPS, downloaded over 4,500 times to date. Our open source software package, a Python wrapper with a Fortran core, is centered around 1D matrix product state (MPS) and matrix product density operator (MPDO) methods, for both closed and open quantum systems, which any experimentalist can download and easily use locally to design and benchmark their quantum simulator architecture of choice. The software elements include (i) prebuilt generalized Ising, Hubbard, and other quantum many-body models, (ii) different time propagation methods for short and long-range interactions, and (iii) supplemental exact diagonalization and quantum trajectory methods. In this talk, I present the capabilities of this code and a range of applications from my own group including exploring new complexity tools for quantum states taken from neuroscience; finding Kibble-Zurek exponents to predict defect formation in quantum quenches with long-range interactions and complex phase diagrams in more advanced Hamiltonians; discovering new features in entangled non-equilibrium quantum dynamics which establish quantum many-body chaos as a separate and open field from classical and quantum chaos; and discovering new regimes of macroscopic quantum tunneling escape with a half-life based on quantum fluctuations. This survey of research outcomes will demonstrate the wide capabilities and potential of OpenMPS in quantum simulator applications.