Initial-state randomness as a universal source of decoherence

TL;DR

This paper demonstrates that initial-state randomness universally limits entanglement growth in multi-qubit systems, with entanglement remaining localized and short-lived regardless of the Hamiltonian, modeled effectively by two-body random matrices.

Contribution

It introduces a universal explanation for entanglement dynamics based on initial-state randomness, supported by a two-body random matrix model.

Findings

Entanglement is short-lived and localized due to initial randomness.

The entanglement dynamics are largely independent of the specific Hamiltonian.

A two-body random matrix model accurately reproduces the observed behavior.

Abstract

We study time evolution of entanglement between two qubits, which are part of a larger system, after starting from a random initial product state. We show that, due to randomness in the initial product state, entanglement is present only between directly coupled qubits and only for short times. Time dependence of the entanglement appears essentially independent of the specific hamiltonian used for time evolution and is well reproduced by a parameter-free two-body random matrix model.