LMU physicists develop a new framework for understanding chemical bonding through quantum entanglement.

Chemical bonding is one of the central organizing principles of the microscopic world. It determines how atoms combine and thereby governs a wide range of physical and chemical properties of quantum systems across many length scales, ranging from small molecules and biomolecules to macroscopically large solid materials. Yet, despite its fundamental importance and its prominent role already in high school science education, chemical bonds remain surprisingly elusive from the perspective of quantum mechanics. They are indispensable for describing matter, even though they are not directly observable quantities.

In a recent article published in Nature Communications, the group led by LMU physicist Christian Schilling and member of the MCQST Cluster of Excellence, addresses this long-standing challenge using concepts from quantum information theory. Building on their expertise in orbital entanglement in quantum chemistry, Christian Schilling and his PhD student Lexin Ding, now an ETH Fellow at ETH Zurich, together with collaborator Eduard Matito from the Donostia International Physics Center in Spain, developed a new framework for understanding chemical bonding through quantum entanglement.

The researchers introduced the notion of maximally entangled atomic orbitals (MEAOs), whose entanglement patterns reveal the bonding structures of molecules in a natural and systematic way. Remarkably, the framework captures not only conventional two-center bonds described by Lewis structures, but also more complex bonding phenomena including multicenter bonding, aromatic systems such as benzene, and transient bonding patterns emerging during chemical reactions. Such diverse bonding scenarios can now be described within a single unified and fully ab initio framework.

The work reveals a deep connection between chemical bonding and quantum entanglement and establishes a unified and quantitative language for describing bonding phenomena. “In the future, the framework could become a powerful tool for studying complex molecular systems, chemical reactions, and unconventional bonding mechanisms for which traditional approaches often fail”, says Schilling.