Efficient simulation of open quantum systems coupled to a reservoir through multiple channels

TL;DR

This paper introduces an efficient method for simulating open quantum systems with multiple bath channels by extending chain mapping techniques, enabling accurate and scalable simulations of complex quantum dynamics.

Contribution

It generalizes the chain mapping approach to multi-channel system-bath couplings, facilitating efficient matrix product state simulations of complex open quantum systems.

Findings

Successfully simulates singlet fission dynamics

Handles diagonal and off-diagonal vibrational couplings

Enables scalable simulations of multi-channel systems

Abstract

The simulation of open quantum systems coupled to a reservoir through multiple channels remains a substantial challenge. This kind of open quantum system arises when considering the radiationless decay of excited states that are coupled to molecular vibrations, for example. We use the chain mapping strategy in the interaction picture to study systems linearly coupled to a harmonic bath through multiple interaction channels. In the interaction picture, the bare bath Hamiltonian is removed by a unitary transformation (the system-bath interactions remain), and a chain mapping transforms the bath modes to a new basis. The transformed Hamiltonian contains time-dependent local system-bath couplings. The open quantum system is coupled to a limited number of (transformed) bath modes in the new basis. As such, the entanglement generated by the system-bath interactions is local, making efficient dynamical simulations possible with matrix product states. We use this approach to simulate singlet fission, using a generalized spin-boson Hamiltonian. The electronic states are coupled to a vibrational bath both diagonally and off-diagonally. This approach generalizes the chain mapping scheme to the case of multi-channel system-bath couplings, enabling the efficient simulation of this class of open quantum systems using matrix product states.