Quantum entanglement within the polarization propagator approach

MILLÁN, LEONARDO A.; AUCAR, GUSTAVO A.; GIRIBET, CLAUDIA G.

Munich

Congreso; 11th Triennial Congress of the World Association of Theoretical and Computational Chemists; 2017

Comité organizador local e internacional

For vicinal and indirect NMR J-couplings there is a well-known empirical rule, the Karplus rule, which states a functional dependence of such J-couplings with the dihedral angle between the coupled nuclei.Recently we have found that the two-electron integrals that both, introduce the electron correlation at the RPA level of approach within the polarization propagator formalism and follow the Karplus rule, have a non-local behavior.[1] After this finding we started to think about whether the excitations that contain those orbitals are entangled. If indeed they are, we might suggest that quantum entanglement would be the phenomenon that can explain the Karplus rule.Until now it was not possible to study the quantum entanglement applying polarization propagators. The reason is the fact that it is not an easy task to define a proper density function and then to calculate the entropy of the system using those propagators. In this presentation we propose a partition function that is valid within the polarization propagator scheme.[2] From such a function we take an additional step forward and define a density function, which allow us to quantify the entanglement between molecular orbital excitations.[3]We present preliminary results calculated with our novel scheme, where it is shown that the above mentioned excitations are actually entangled.[1] G. A. Aucar, R. H. Romero, A. F. Maldonado, Int. Rev. in Phys. Chem. 29, 1-64 (2010).[2] G. A. Aucar, Phys. Chem. Chem. Phys. 16, 4420-4438 (2014).[3] K. Boguslawski, P. Tecmer, G. Barcza, O. Legeza, M. Reiher, J. Chem. Theory Comput. 9, 2959-3973 (2013)