Quantum entanglement in photosynthetic light harvesting complexes

TL;DR

This paper rigorously quantifies quantum entanglement in photosynthetic light harvesting complexes, revealing the presence of bipartite, long-range, and multipartite entanglement under physiological conditions, and discusses potential practical applications.

Contribution

It introduces new methods for quantifying entanglement in biological systems and applies them to the FMO complex, demonstrating the existence of various forms of entanglement at physiological temperatures.

Findings

FMO complex contains bipartite entanglement between chromophores

Long-range and multipartite entanglement exist at physiological temperatures

First rigorous quantification of entanglement in a biological system

Abstract

Light harvesting components of photosynthetic organisms are complex, coupled, many-body quantum systems, in which electronic coherence has recently been shown to survive for relatively long time scales despite the decohering effects of their environments. Within this context, we analyze entanglement in multi-chromophoric light harvesting complexes, and establish methods for quantification of entanglement by presenting necessary and sufficient conditions for entanglement and by deriving a measure of global entanglement. These methods are then applied to the Fenna-Matthews-Olson (FMO) protein to extract the initial state and temperature dependencies of entanglement. We show that while FMO in natural conditions largely contains bipartite entanglement between dimerized chromophores, a small amount of long-range and multipartite entanglement exists even at physiological temperatures. This constitutes the first rigorous quantification of entanglement in a biological system. Finally, we discuss the practical utilization of entanglement in densely packed molecular aggregates such as light harvesting complexes.