Classical and Quantum Orbital Correlations in the Molecular Electronic States

Abstract

The quantum superposition principle has been extensively utilized in the quantum mechanical description of the bonding phenomenon. It explains the emergence of delocalized molecular orbitals and provides a recipe for the construction of near-exact electronic wavefunctions. On the other hand, its existence in composite systems may give rise to nonclassical correlations that are regarded now as a resource in quantum technologies. Here, we approach the electronic ground states of three prototypical molecules from the point of view of fermionic information theory. For the first time in the literature, we properly decompose the pairwise orbital correlations into their classical and quantum parts in the presence of superselection rules. We observe that quantum orbital correlations can be stronger than classical orbital correlations though not often. Also, quantum orbital correlations can survive even in the absence of orbital entanglement depending on the symmetries of the constituent orbitals. Finally, we demonstrate that orbital entanglement would be underestimated if the orbital density matrices were treated as qubit states.

Quantum correlations in molecules: from quantum resourcing to chemical bonding

“…This historic opportunity has boosted many studies on fermionic correlation and entanglement in the quantum information (QI) community [4][5][6][7][8][9][10][11][12][13][14][15][16][17], with an emphasis on the conceptual formalism and resource utilization aspects. Independently, fermionic correlation has been used in the quantum chemistry (QC) community to describe the electronic structure of chemical systems [18][19][20][21][22][23][24][25][26][27][28][29] and to improve as well as optimize the initial ansatz of numerical methods [30][31][32]. Yet, only rudimentary QI tools have thus far been widely adopted for such type of studies.…”

Quantum Correlations in Jahn-Teller Molecular Systems Simulated with Superconducting Circuits

“…Quantum entanglement in natural systems, in particular molecules, has been attracted much attention for its fundamental and practical significance [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Due to their complex structure and many interactions within, it is difficult to isolate the quantum entanglement route in molecules.…”