Does relativistic motion really freeze initially maximal entanglement?

TL;DR

This paper demonstrates that the $CL_4$ quantum state maintains maximal bipartite entanglement under all accelerations, challenging the belief that relativistic effects always degrade entanglement.

Contribution

It reveals the phenomenon of complete entanglement freezing in a relativistic setting, a novel discovery in quantum information theory.

Findings

$1-3$ bipartite entanglement remains maximal at all accelerations

The phenomenon of entanglement freezing is systematically characterized

Challenges the view that acceleration always diminishes entanglement

Abstract

We investigate the relativistic dynamics of quantum entanglement in a four-qubit cluster ($CL_4$) state using a fully operational Unruh-DeWitt detector framework. Contrary to the widely held expectation that the Unruh effect inevitably degrades initially maximal entanglement, we demonstrate that the $1-3$ bipartite entanglement of the $CL_4$ state remains strictly maximal for all accelerations, including the infinite-acceleration limit. This result uncovers a previously unexplored phenomenon, namely the ``complete freezing of initially maximal entanglement" under relativistic motion. To the best of our knowledge, this is the first identification and systematic characterization of such a phenomenon within a relativistic framework. These findings overturn the conventional view that acceleration universally diminishes maximal entanglement and establish the $CL_4$ state as a promising resource for quantum information processing in non-inertial or curved-spacetime settings.