Nonlocal correlations in noisy multiqubit systems simulated using matrix product operators

TL;DR

This paper presents an open-source solver for the Lindblad master equation using matrix product states, demonstrating that driven multiqubit systems can develop large, nonlocal correlations even with weak interactions, especially in systems with alternating qubit frequencies.

Contribution

The authors develop and apply a matrix product operator-based solver to study nonlocal correlations in noisy multiqubit systems under continuous driving, revealing unexpected long-range correlations.

Findings

Large correlations between distant qubits due to excitation tunneling.

Correlation functions can increase with distance, peaking at system edges.

Alternating-frequency qubits exhibit significant nonlocal effects.

Abstract

We introduce an open-source solver for the Lindblad master equation, based on matrix product states and matrix product operators. Using this solver we study the dynamics of tens of interacting qubits with different connectivities, focusing on a problem where an edge qubit is being continuously driven on resonance, which is a fundamental operation in quantum devices. Because of the driving, induced excitations propagate through the qubits until the system reaches a steady state due to the incoherent terms. We find that with alternating-frequency qubits whose interactions with their off-resonant neighbors appear weak, the tunneling excitations lead to large correlations between distant qubits in the system. Some two-qubit correlation functions are found to increase as a function of distance in the system (in contrast to the typical decay with distance), peaking on the two edge qubits farthest apart from each other.