The Chemical Bond in the Age of Quantum Information: Atoms in Molecules as Entangled Open Systems
Abstract
The chemical bond is among the oldest ideas in chemistry and still among the least settled: chemists continue to disagree about what a bond is. We argue that the recurring controversies (ionic versus covalent, dative versus shared-electron, hypervalent versus metavalent, whether metal–metal contacts are genuinely collective) are not disputes about the physics but about an unstated reference against which a bond is declared. Removing the reference forces a change of viewpoint: an atom in a molecule is not a fixed piece of electron density but an open quantum system, a mixed state that is a probabilistic superposition over how many electrons it owns. From this vantage the electronnumber fluctuations that the theory of electron distribution functions has long measured acquire a sharp meaning: they are the quantum correlation, the entanglement, shared between the atoms of a molecule. Measured directly between the Bader basins chemists already draw, this entanglement yields a single, reference-free bond order in which the electron pair of Lewis, the resonance of Pauling and the delocalization of Mulliken reappear not as assumptions but as consequences. We outline the open-systems formulation of Quantum Chemical Topology that makes the picture exact, and sketch how the same quantity is the natural readout of molecular quantum computation.
Related
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BibTeX
@misc{rodrigues2026chemical,
title = {{The Chemical Bond in the Age of Quantum Information: Atoms in Molecules as Entangled Open Systems}},
author = {D. J. L. Rodrigues and E. Francisco and A. Martín Pendás and Ángel Martín Pendás},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010244/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010244/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - The Chemical Bond in the Age of Quantum Information: Atoms in Molecules as Entangled Open Systems
AU - D. J. L. Rodrigues
AU - E. Francisco
AU - A. Martín Pendás
AU - Ángel Martín Pendás
PY - 2026
DA - 2026/10/11
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010244/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010244/v1
AB - The chemical bond is among the oldest ideas in chemistry and still among the least settled: chemists continue to disagree about what a bond is. We argue that the recurring controversies (ionic versus covalent, dative versus shared-electron, hypervalent versus metavalent, whether metal–metal contacts are genuinely collective) are not disputes about the physics but about an unstated reference against which a bond is declared. Removing the reference forces a change of viewpoint: an atom in a molecule is not a fixed piece of electron density but an open quantum system, a mixed state that is a probabilistic superposition over how many electrons it owns. From this vantage the electronnumber fluctuations that the theory of electron distribution functions has long measured acquire a sharp meaning: they are the quantum correlation, the entanglement, shared between the atoms of a molecule. Measured directly between the Bader basins chemists already draw, this entanglement yields a single, reference-free bond order in which the electron pair of Lewis, the resonance of Pauling and the delocalization of Mulliken reappear not as assumptions but as consequences. We outline the open-systems formulation of Quantum Chemical Topology that makes the picture exact, and sketch how the same quantity is the natural readout of molecular quantum computation.
ER -