A critical view on transport and entanglement in models of photosynthesis

TL;DR

This paper critically examines claims of quantum entanglement in photosynthesis, arguing that current evidence is inconclusive and that similar transport efficiency can occur without entanglement, challenging its supposed essential role.

Contribution

It provides a counter-example showing that entanglement is not necessary for efficient transport in photosynthetic models, questioning recent claims of its fundamental role.

Findings

Transport phenomenology can be replicated without entanglement.

Entanglement, if present, appears incidental and non-essential.

Current evidence for entanglement in light-harvesting complexes is inconclusive.

Abstract

We revisit critically the recent claims, inspired by quantum optics and quantum information, that there is entanglement in the biological pigment protein complexes, and that it is responsible for the high transport efficiency. While unexpectedly long coherence times were experimentally demonstrated, the existence of entanglement is, at the moment, a purely theoretical conjecture; it is this conjecture that we analyze. As demonstrated by a toy model, a similar transport phenomenology can be obtained without generating entanglement. Furthermore, we also argue that even if entanglement does exist, it is purely incidental and seems to plays no essential role for the transport efficiency. We emphasize that our paper is not a proof that entanglement does not exist in light-harvesting complexes - this would require a knowledge of the system and its parameters well beyond the state of the art. Rather, we present a counter-example to the recent claims of entanglement, showing that the arguments, as they stand at the moment, are not sufficiently justified and hence cannot be taken as proof for the existence of entanglement, let alone of its essential role, in the excitation transport.