Propagating large open quantum systems towards their asymptotic states: cluster implementation of the time-evolving block decimation scheme

Many-body quantum systems are subjected to the Curse of Dimensionality: The dimension of the Hilbert space H, where these systems live in, grows exponentially with number of their components. However, with some systems, it is possible to escape the curse by using a low-rank tensor approximation known as “matrix-product state/operator (MPS/O) representation” in the quantum community and “tensor-train decomposition” among applied mathematicians. Motivated by recent advances in computational quantum physics, we consider chains of N spins coupled by nearest-neighbor interactions. The spins are subjected to an action coming from the environment. Spatially disordered interaction and environment-induced decoherence drive systems into non-trivial asymptotic states. The dissipative evolution is modeled with a Markovian master equation in the Lindblad form. By implementing the MPO technique and propagating system states with the time-evolving block decimation scheme, which allows keeping the length of the state descriptions fixed, it is in principle possible to reach the asymptotic states. We propose and realize a cluster implementation of this idea. The implementation on four nodes allowed us to resolve the asymptotic states of the model systems with N = 128 spins (total dimension of the Hilbert space dimH = 2¹²⁸ ≈ 10³⁹).