# Spinsim: A GPU optimized python package for simulating spin-half and spin-one quantum systems

## Description

Spinsim simulates the quantum dynamics of unentangled spin-1/2 and spin-1 systems evolving under time-dependent control. While other solvers for the time-dependent Schrödinger equation optimize for larger state spaces but less temporally-rich control, spinsim is optimized for intricate time evolution of a minimalist system. Efficient simulation of individual or ensemble quanta driven by adiabatic sweeps, elaborate pulse sequences, complex signals and non-Gaussian noise is the primary target application. We achieve fast and robust evolution using a geometric integrator to bound errors over many steps, and split the calculation parallel-in-time on a GPU using the numba just-in-time compiler. Speed-up is three orders of magnitude over QuTip's sesolve and Mathematica's NDSolve, and four orders over SciPy's ivp_solve for equal accuracy. Interfaced through python, spinsim should be useful for simulating robust state preparation, inversion and dynamical decoupling sequences in NMR and MRI, and in quantum control, memory and sensing applications with two- and three-level quanta.