An international team of scientists from IBM, the University of Manchester, the University of Oxford, ETH Zurich, EPFL and the University of Regensburg has created and characterized a molecule unlike any other known so far: its electrons travel through the molecule’s structure in a corkscrew-like pattern that fundamentally alters its chemical behavior. Published in Science, this work describes the first experimental observation of a half-Möbius electronic topology in a single molecule.
To the best of scientists’ knowledge, a molecule with such an electronic topology has never before been synthesized, observed, or even formally predicted. Understanding the behavior of this molecule at the level of electronic structure required something equally fundamental: a high-fidelity quantum computing simulation capable of precisely analyzing every property of the molecule.
Quantum simulation
The discovery represents a scientific advance on two fronts. For chemistry, it demonstrates that electronic topology—the property that governs how electrons move through a molecule—can be deliberately designed and not simply found in nature. For quantum computing, it is a concrete demonstration of a quantum simulation doing what it was designed to do: directly represent the behavior of quantum mechanics, at the molecular scale, to produce scientific knowledge that would otherwise have remained out of reach.
“We first designed a molecule that we thought could be created, then we built it and finally validated it, along with its exotic properties, with a quantum computer,” says Alessandro Curioni, IBM Fellow, vice president for Europe and Africa and director of IBM Research Zurich. “This is a big step toward the dream that renowned physicist Richard Feynman laid out decades ago: building a computer capable of simulating quantum physics in the best possible way and a demonstration where, as he said, ‘there’s a lot of room at the bottom.’” The success of this research marks a step towards this vision, opening the door to new ways of exploring the world and the matter that makes it up, including deep understanding of each molecule.
A molecule never seen before
The molecule, with the formula C₁₃Cl₂, was assembled atom by atom in IBM laboratories from a custom precursor synthesized at the University of Oxford. To build the molecule, individual atoms were removed, one by one, using precisely calibrated voltage pulses under ultra-high vacuum conditions and at temperatures close to absolute zero.
Experiments with scanning scanning and atomic force microscopy—both techniques pioneered by IBM—were combined with quantum computing to reveal an electronic configuration unparalleled in the existing record of chemistry: a molecule with an electronic structure that undergoes a 90-degree turn in each circuit, requiring four complete turns to return to the initial phase.
This half-Möbius topology is qualitatively different from that of any previously known molecule and can reversibly switch between clockwise, counterclockwise, and non-twisted states. This demonstrates that the electronic topology of a molecule is not just an undiscovered property, but one that can now be deliberately designed under specific conditions.
A disruptive scientific tool
The scientists in this experiment created a molecule that had never existed. Now they had to figure out why it worked, a task that challenged conventional computers. The electrons within the C₁₃Cl₂ molecule interact in deeply intertwined ways, all influencing each other simultaneously. Modeling that behavior in a molecule requires tracking every possible configuration of those interactions at once, which requires computational power that grows exponentially and can quickly surpass classical machines.
Quantum computers are different in nature because they operate according to the same laws of quantum mechanics that govern electrons in molecules and can represent these systems directly rather than approximating them. They “speak” the same fundamental language as the subject matter they are designed to study, and that distinction, once largely theoretical, can now contribute to concrete scientific results.
To the best of scientists’ knowledge, a molecule with such an electronic topology has never before been synthesized, observed or predicted.
This capability offers enormous potential for quantum computers to support real-world experimentation through quantum-centric supercomputing workflows. By integrating quantum processing units (QPUs), CPUs, and GPUs, this approach allows complex problems—such as the behavior of a molecule—to be decomposed into parts that are orchestrated and solved according to the strengths of each system, achieving what no computing paradigm can offer on its own.
More exotic molecular structures
Using an IBM quantum computer within that workflow, the team found helical molecular orbitals for electron binding, a fingerprint of the half-Möbius topology in the studied molecule. Furthermore, simulation using quantum computing helped reveal the mechanism behind the formation of this unusual topology in the molecule: a helical pseudo-Jahn-Teller effect.
This achievement builds on IBM’s long legacy in nanoscale science. The scanning tunneling microscope (STM) was invented by IBM in 1981, for which IBM scientists Gerd Binnig and Heinrich Rohrer received the Nobel Prize in 1986. Their creation allowed researchers to image surfaces atom by atom. In 1989, IBM scientists developed the first reliable method for manipulating individual atoms. Over the past few decades, the IBM team has extended these techniques to build and control increasingly exotic molecular structures, including this extraordinary molecule.
