A scalable algorithm of numerical real-time path integral for quantum dissipative systems.

Numerical real-time path integration has been a practical method to study a quantum system under the influence of its environment. Performing the path integral computations, however, is a resource-demanding task in general, and implementing it is less straightforward with modern hardware architectures of massively parallel platforms. In this article, a numerical algorithm based on the quasiadiabatic propagator path integral scheme is proposed and shown to scale for systems with large size. As a case study of performance, the quantum dynamics of excitation energy transfer in the Fenna-Matthews-Olson complex is discussed, employing a vibronic model in which the system size can be varied simply by adding vibrational excitations.