Detail Project and Funding

Abstract: The role of quantum mechanics in biological organisms has been a fundamental question of twentieth-century biology. However, only recently, by exploiting new experimental spectroscopy techniques, it has been possible to observe quantum mechanical effects in biomolecules and, in particular, in light-harvesting systems at the basis of photosynthetic processes in plants, algae, and in some bacteria. Here, the energy of the absorbed solar photons is transferred from an “absorbing centre” to a “reaction centre”, where the effective photosynthesis occurs, via a very-high efficiency transport mechanism (above 95%). It is now widely believed that quantum effects play a fundamental role in making such a process remarkably robust and efficient.
A complete understanding of this high-efficiency quantum transport scheme would help clarifying the role of quantum mechanics in biological systems and could also open very interesting perspectives in the field of solar energy. In particular, it could give useful information for the synthesis of new molecular systems for artificial photosynthesis, which can mimic the behavior of light-harvesting complexes and be employed for the realization of a new generation of more efficient solar energy devices.
In this context, the main goal of this proposal is the theoretical analysis and the experimental realization of optical simulators, made only by optical components, to reproduce the transport mechanism of light-harvesting systems, with particular attention to quantum effects that can increase the energy transfer efficiency (i.e., noise-assisted transport, suppression of dark states, and entanglement). The role of the electronic excitation in a given biological molecule will be played by the presence or absence of a single photon (the quantum of excitation of the electromagnetic field) in a particular spatial-temporal field mode. The best setup to simulate the complex interacting many-body system of the light-harvesting protein has to be a good compromise between the complexity of the real system and the experimental feasibility. In order to obtain the ambitious goal of the proposal, theoretical and experimental works are needed, respectively to identify an optical
model simulating “as closely as possible” the complexity of biological systems, and to check the practical capability of realizing such an optical system with controllable and detectable parameters. The comparison between numerical simulations of theoretical models and experimental measurements will allow us to identify, realize, and characterize the more scalable, tunable, and feasible optical simulator.
Differently from what can be done with real biological samples, a purely optical setup has the remarkable advantage of allowing a complete control over all the fundamental system parameters. Indeed, an optical system can be initialized in a well-defined arbitrary quantum state, the couplings between different molecules/modes and the effect of noise in the excitation transfer scheme can be easily adjusted, and the intermediate and final states of the system are directly accessible for monitoring the evolution of the excitation and its transport across the optical network in a complete way. Furthermore, if a sufficiently re-configurable experimental setup is available, the effect of different network topologies can be investigated. Obviously, it is impossible to have such a control by directly investigating natural photosynthetic systems, and, also in the case of artificial photosynthetic molecules, the remarkable cost of producing them does not allow one to freely manipulate and explore too many different configurations. Our simulator will, instead, give us access to a wide and perfectly controllable parameter space, where the direct monitoring of the quantum evolution of the system will lead us to a better understanding of the quantum effects influencing the energy transfer mechanisms.
Finally, the comparison between the experimental results, obtained in different optical configurations, and the numerical predictions, calculated according to theoretical models developed for this specific purpose, will allow us to better model and investigate the processes involved in excitation energy transfer in quantum bio-networks, and to pave the way for the development of novel molecular geometries that might be used for future, more efficient, and strategically important, solar
energy technologies.

INO’s Experiments/Theoretical Study correlated:
Optical simulators of quantum transport in photosynthetic systems and prospects for new solar energy technologies
Quantum light state engineering