## 1 Introduction  
Photosynthesis is a fundamental process for life on Earth through which light energy coming from the sun is absorbed and used by photosynthetic organisms to perform necessary metabolic reactions. Its success is the result of millions of years of evolution during which those organisms have developed highly specialized structures able to capture, transfer and store light energy by a series of physical and chemical transformations. An important group of these structures are the light-harvesting complexes (LHC), responsible for capturing photons and transferring their energy to the reaction centers (RC), where charge separation takes place. Since their early discovery, LHCs have captured the attention of researchers due to their remarkable nearly 100% photochemical quantum yield [1; 2; 3; 4]. The study of photosynthesis continued as theories on electron transfer in biological systems matured [5; 6], and the Fenna-Matthews-Olson (FMO) complex took the spotlight as it became the first mapped LHC structure [7; 8]. Multiple disciplines are actively collaborating in the race for unraveling the mechanism behind this energy transfer efficiency and its large range of possible applications that range from photovoltaics to quantum computing [9; 10]. New and improved information about the structure and its behaviour continues to emerge [1; 11; 12]. While theoretical physics has provided the basis for advanced femtosecond laser techniques necessary for tracing excitation energy transfer (EET) dynamics [13; 14], biochemical studies on the species [15; 16] and genetic methods are being used for purifying, characterizing and even modifying the protein structure [17; 18; 19; 20]. Additionally, improving X-ray crystallographic procedures have been key for obtaining high resolution electron density maps of protein complexes which allow insight into existing interactions within the macro molecule [7; 8; 21]. Though the presence of long-lived quantum coherence in the FMO complex has been confirmed [22; 23; 24], its role and relevance for the high energy transfer efficiency properly in the central photosynthetic processes within the protein is still a matter of debate [25; 26]. The conflict originates from the comparison between coherent (e.g., Lindblad equation) and incoherent (e.g., Forster theory) theories which appear to yield similar approximations since coherence decay occurs on different timescale as the energy transfer, thus questioning the actual importance of quantum coherence [21; 25]. Many authors have stated that the observed efficiency in energy transfer within light-harvesting complexes such as the FMO require both coherent and incoherent energy transfer [23; 27; 28; 29]. Although the presence of environmental noise and the acceleration of decoherence may seem counterproductive, this transition might be necessary to assure fast unidirectional transfer towards the reaction center [23; 30; 31]. Going further, theoretical physics and chemistry are developing a better understanding of the mechanisms involved from a quantum perspective that enables their simulation and allows tracking of possible control parameters still for further technological applications exploding the quantum features on a biological substrate. This may lead to the hopeful application of this system as a biological resource of quantum processing, particularly due to its room temperature performance [22; 30; 32]. This merge of disciplines has resulted in the introduction of physical concepts into a biological context for the wide study of photosynthesis. For instance, in solid-state physics the exciton refers to a collective electronic excitation with well-defined quantum properties in a molecular crystal. Though lacking the same ordered and static structure, photosynthetic proteins also share excitation among their pigment molecules in a more ordered manner than pure pigments in solution [21]. Thus, these systems have been settled to be somewhere between crystals and fluids [21].