Abstract Biological systems are currently analysed from deeper approaches considering not only their chemical features but also their quantum ones. Such elusive features sometimes account for specific phenomena related to their evolution and survival. Green sulphur bacteria are very simple microorganisms performing a highly photosynthetic process to survive. The Fenna-Mathew-Olson (FMO) complex is a macro-molecule responsible for such efficiency exhibiting interesting quantum features. Post-experimental biology together with Physics able the possibility to research and analyse them. In the current work, a synthetic roadmap for the FMO simulation is presented with comprehensive literature. The density matrix evolution is obtained to then discuss other derived features such as coherence, entanglement, state transference, and energy transmission efficiency.
Abstract Biological systems are currently analysed from deeper approaches considering not only their chemical features but also their quantum ones. Such elusive features sometimes account for specific phenomena related to their evolution and survival. Green sulphur bacteria are very simple microorganisms performing a highly photosynthetic process to survive. The Fenna-Mathew-Olson (FMO) complex is a macro-molecule responsible for such efficiency exhibiting interesting quantum features. Post-experimental biology together with Physics able the possibility to research and analyse them. In the current work, a synthetic roadmap for the FMO simulation is presented with comprehensive literature. The density matrix evolution is obtained to then discuss other derived features such as coherence, entanglement, state transference, and energy transmission efficiency.
Fenna-Mathews-Olson complexes participate in the photosynthetic process of Sulfur Green Bacteria. These biological subsystems exhibit quantum features which possibly are responsible for their high efficiency; the latter may comprise multipartite entanglement and the apparent tunnelling of the initial quantum state. At first, to study these aspects, a multidisciplinary approach including experimental biology, spectroscopy, physics, and math modelling is required. Then, a global computer modelling analysis is achieved in the computational biology domain. The current work implements the Hierarchical Equations of Motion to numerically solve the open quantum system problem regarding this complex. The time-evolved states obtained with this method are then analysed under several measures of entanglement, some of them already proposed in the literature. However, for the first time, the maximum overlap with respect to the closest separable state is employed. This authentic multipartite entanglement measure provides information on the correlations, not only based on the system bipartitions as in the usual analysis. Our study has led us to note a different view of FMO multipartite entanglement as tiny contributions to the global entanglement suggested by other more basic measurements. Additionally, in another related trend, the initial state, considered as a Förster Resonance Energy Transfer, is tracked using a novel approach, considering how it could be followed under the fidelity measure on all possible permutations of the FMO subsystems through its dynamical evolution by observing the tunnelling in the most probable locations. Both analyses demanded significant computational work, making for a clear example of the complexity required in computational biology.
Abstract Fenna-Matthews-Olson (FMO) bacteriochlorophylls (BChls) are molecules responsible of the high efficiency energy transfer in the photosynthetic process of green sulfur bacteria, controversially associated to quantum phenomena of long lived coherence. This phenomenon is modelled using Quantum Open Systems (QOS) without include memory effects of the surrounding approximated as a phonon bath on thermal equilibrium. This work applies the Hierarchical Equations of Motion method (HEOM), a non-Markovian approach, in the modelling of the system evolution of FMO complex to perform predictions about the coherence times scales together with global and semi-local entanglement during the quantum excitation.
A study published on arXiv has strictly demonstrated the existence of true multipartite quantum entanglement between bacteriochlorophyll-a (BChl a) molecules within the Fenna-Matthews-Olson (FMO) light-harvesting complex of green sulfur bacteria. Using entanglement measures in the single-excitation subspace (bipartite concurrence and a global entanglement measure), the study proved for the first time in a biological system that these entanglement states persist for approximately 2 picoseconds (ps) not only at cryogenic temperatures but also at physiological temperatures (300 K, room temperature), surviving macroscopically. The findings suggest that strong quantum entanglement between distant molecules can enhance the robustness and efficiency of the energy transfer network as the exciton moves toward the reaction center, even amidst environmental noise (decohering effects). [Quantum Biology Society] Photosynthesis, known as one of the most efficient energy conversion processes in nature, has long been a subject of wonder for scientists. While previous research focused on quantum coherence at the single-particle level, a groundbreaking study has recently been published mathematically proving that "true quantum entanglement"—the non-local correlation between multiple pigment molecules—actually operates within living organisms, drawing global attention. The paper titled "Quantum entanglement in photosynthetic light harvesting complexes," published in the preprint repository arXiv, is evaluated as a monumental achievement in elucidating macroscopic quantum phenomena in biological systems. An international joint research team led by Mohan Sarovar, Akihito Ishizaki, Graham R. Fleming, and K. Birgitta Whaley from UC Berkeley and Lawrence Berkeley National Laboratory (LBNL) in the USA spearheaded this innovative research. ■ Demonstration of Multipartite Quantum Entanglement within the FMO Complex The researchers focused on the FMO (Fenna-Matthews-Olson) light-harvesting complex of green sulfur bacteria (Chlorobium tepidum). By precisely analyzing the exciton dynamics between the pigment molecules within the complex using a non-Markovian quantum master equation, they proved through bipartite concurrence and a measure of global entanglement that true multipartite quantum entanglement is formed, going beyond simple individual coherence. This marks the first rigorous instance of quantifying quantum entanglement in a biological system. ■ Quantum Information Maintained Through Room-Temperature Noise The most surprising discovery is that these delicate quantum entanglement states survive meaningfully even at warm and wet physiological temperatures. While it was generally thought that quantum states are instantly destroyed by the thermal fluctuations of the surrounding proteins and solvent (decohering effects), the study's results confirmed that the natural FMO complex maintains bipartite entanglement between dimerized pigments and even a small amount of long-range and multipartite entanglement at 300 K. This entanglement plays a crucial role in enhancing the efficiency and robustness of the energy transfer network as the exciton travels to the reaction center. ■ Living Organisms as Optimized Quantum Machines This study suggests that living organisms are not merely losing quantum phenomena in harsh environmental noise but are rather highly designed, optimized quantum machines that endure and actively utilize them. Mimicking these perfect energy transfer mechanisms of nature is expected to provide key physical clues for maximizing the efficiency of next-generation solar cells or developing innovative quantum communication and metrology devices that operate robustly even at room temperature. https://arxiv.org/abs/0905.3787
Abstract Quantum effects in photosynthetic energy transport in nature, especially for the typical Fenna-Matthews-Olson (FMO) complexes, are extensively studied in quantum biology. Such energy transport processes can be investigated as open quantum systems that blend the quantum coherence and environmental noise, and have been experimentally simulated on a few quantum devices. However, the existing experiments always lack a solid quantum simulation for the FMO energy transport due to their constraints to map a variety of issues in actual FMO complexes that have rich biological meanings. Here we successfully map the full coupling profile of the seven-site FMO structure by comprehensive characterisation and precise control of the evanescent coupling of the three-dimensional waveguide array. By applying a stochastic dynamical modulation on each waveguide, we introduce the base site energy and the dephasing term in coloured noise to faithfully simulate the power spectral density of the FMO complexes. We show our photonic model well interprets the phenomena including reorganisation energy, vibrational assistance, exciton transfer and energy localisation. We further experimentally demonstrate the existence of an optimal transport efficiency at certain dephasing strength, providing a window to closely investigate environment-assisted quantum transport.
The Fenna-Mathews-Olson (FMO) complex present in green sulfur bacteria is known to mediate the transfer of excitation energy between light-harvesting chlorosomes and membrane-embedded bacterial reaction centers. Due to the high efficiency of this transport process, it is an extensively studied pigment-protein complex system with the eventual aim of modeling and engineering similar dynamics in other systems and using it for real-time application. Some studies have attributed the enhancement of transport efficiency to wavelike behavior and non-Markovian quantum jumps resulting in long-lived and revival of quantum coherence, respectively. Since dynamics in these systems reside in the quantum-classical regime, quantum simulation of such dynamics will help in exploring the subtle role of quantum features in enhancing the transport efficiency, which has remained unsettled. Discrete simulation of the dynamics in the FMO complex can help in efficient engineering of the heat bath and controlling the environment with the system. In this work, using the discrete quantum jump model we show and quantify the presence of higher non-Markovian memory effects in specific site pairs when internal structures and environmental effects are in favor of faster transport. As a consequence, our study leans toward the connection between non-Markovianity in quantum jumps with the enhancement of transport efficiency.
The Fenna-Matthews-Olson (FMO) complex - a pigment protein complex involved in photosynthesis in green sulfur bacteria - is remarkably efficient in transferring excitation energy from light harvesting antenna molecules to a reaction center. Recent experimental and theoretical studies suggest that quantum coherence and entanglement may play a role in this excitation energy transfer (EET). We examine whether bipartite quantum nonlocality, a property that expresses a stronger-than-entanglement form of correlation, exists between different pairs of chromophores in the FMO complex when modeling the EET by the hierarchically coupled equations of motion method. We compare the results for nonlocality with the amount of bipartite entanglement in the system. In particular, we analyze in what way these correlation properties are affected by different initial conditions. It is found that bipartite nonlocality only exists when the initial conditions are chosen in an unphysiological manner and probably is absent when considering the EET in the FMO complex in its natural habitat. It is also seen that nonlocality and entanglement behave quite differently in this system. In particular, for localized initial states, nonlocality only exists on a very short time scale and then drops to zero in an abrupt manner. As already known from previous studies, quantum entanglement between chromophore pairs on the other hand is oscillating and exponentially decaying and follow thereby a pattern more similar to the chromophore population dynamics. The abrupt disappearance of nonlocality in the presence of nonvanishing entanglement is a phenomenon we call nonlocality sudden death; a striking manifestation of the difference between these two types of correlations in quantum systems.