Classical and quantum orbital correlations in molecular electronic states

• Published in: New journal of physics Vol. 24; no. 10; pp. 102001 - 102013
• Main Authors: Pusuluk, Onur, Yeşiller, Mahir H, Torun, Gökhan, Müstecaplıoğlu, Özgür E, Yurtsever, Ersin, Vedral, Vlatko
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.10.2022
• Subjects: Chemical bonds; Chemistry; Correlation; Electron states; fermionic information theory; fermionic super-selection rules; Information theory; Molecular orbitals; orbital discord; orbital entanglement; Phase transitions; Physics; quantum discord; Quantum entanglement; Quantum mechanics; Qubits (quantum computing); Superposition (mathematics); Wave functions
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/ac932b

Abstract The quantum superposition principle has been extensively utilized in the quantum mechanical description of 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 as a resource in quantum technologies. Here, we approach the electronic ground states of three prototypical molecules in the light of the framework set by fermionic information theory. By introducing the notion of orbital discord, we additively 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. Moreover, 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.