System information propagation for spin structures

TL;DR

This paper investigates how information about a spin register is transferred and stored in its environment during decoherence, revealing regimes of classical encoding and the role of protected subspaces in quantum information dynamics.

Contribution

It introduces a detailed analysis of information flow and the role of decoherence and protected subspaces in spin environments, expanding understanding of quantum decoherence mechanisms.

Findings

Register decoheres into a classical bit string with redundant environmental encoding

Presence of decoherence free and orthogonalization free subspaces affects coherence loss

Rich structure of coherence protection and loss in the asymptotic state

Abstract

We study in details decoherence process of a spin register, coupled to a spin environment. We use recently developed methods of information transfer study in open quantum systems to analyze information flow between the register and its environment. We show that there are regimes when not only the register decoheres effectively to a classical bit string, but this bit string is redundantly encoded in the environment, making it available to multiple observations. This process is more subtle than in a case of a single qubit due to possible presence of protected subspaces: Decoherence free subspaces and, so called, orthogonalization free subspaces. We show that this leads to a rich structure of coherence loss/protection in the asymptotic state of the register and a part of its environment. We formulate a series of examples illustrating these structures.