Resumen de Local quantum uncertainty as a robust metric to characterize discord-like quantum correlations in subsets of the chromophores in photosynthetic light-harvesting complexes
Green sulfur bacteria is a photosynthetic organism whose light-harvesting complex accommodates a pigment-protein complex called FennaMatthews-Olson (FMO). The FMO complex sustains quantum coherence and quantum correlations between the electronic states of 7 separated chromophores as energy moves with nearly a 100% quantum efficiency to the reaction center. We present a method based on the quantum uncertainty associated to local measurements to quantify discord-like quantum correlations between two subsystems where one is a qubit and the other is a qudit. We implement the method by calculating local quantum uncertainty (LQU), concurrence, and coherence between subsystems of pure and mixed states represented by the eigenstates and by the thermal equilibrium state determined by the FMO Hamiltonian. Three partitions of the seven chromophores network define the subsystems: one chromophore with six chromophores, pairs of chromophores, and one chromophore with two chromophores. The robustness of the LQU method allows quantification of quantum correlations that had not been studied before, identification of the strongest correlations in qubits networks , and a possible implementation in dynamical models to study efficient energy transport pathways. Finally, we take the LQU of the most quantum correlated subsets of chromophores as the signature of the non-classicity of the system to study physical properties such as populations, energy fluctuations, and specific heat. We find that a Schottky-like anomaly in the specific heat identifies the availability of energy levels, which in turn define the relation between a measurable macroscopic magnitude and non-classical resources.
