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Studierende sitzt am Arbeitsplatz und schaut auf den Laptop. © Aliona Kardash​/​TU Dortmund

Physicists in Dortmund Predict Exotic Quantum State

© Luca Bradley
From left: Christof Weitenberg, Benedikt Fauseweh, David Haink
Quantum states at opposite ends of a chain can couple with one another even if their wave functions practically do not overlap. A research team at TU Dortmund University has predicted this unusual mechanism. The study combines theoretical physics and experimental expertise and was published in the journal *Physical Review Letters*.

The study resulted from a collaboration between David Haink and Benedikt Fauseweh from the Department of Theoretical Physics and experimental physicist Christof Weitenberg at TU Dortmund University. Dr. Andreas A. Buchheit from the Department of Applied Mathematics at Saarland University also contributed to the study.

The focus is on so-called Majorana edge states, which can occur at both ends of a chain in topological superconducting quantum systems. They are particularly interesting because they are considered potential building blocks for future quantum computers: spatially separated edge states could help protect quantum information from local disturbances.

© Benedikt Fauseweh

The team has now shown that long-range interactions can connect the two ends in a surprising way. The edge states remain tightly localized at their respective chain ends, yet they still couple across the entire chain. The researchers refer to this mechanism as “nonlocal hybridization of edge states.” In this process, the coupling decreases as the chain length increases, just as the long-range interaction does. Spatial separation alone therefore provides less protection for the states than one would expect based on the short-range model.

This prediction opens up new possibilities for investigating the interplay between topology and long-range interactions. At the same time, it provides important insights into the conditions under which Majorana states could be suitable for processing quantum information. This is where the collaboration between theory and experiment in Dortmund directly comes into play: The study describes how the model under investigation could be realized using ultracold polar molecules in a lattice generated by laser light—thus pointing to a concrete path for experimental verification.

The results can be found in: David Haink, Andreas A. Buchheit, Christof Weitenberg, and Benedikt Fauseweh, “Nonlocal Edge Mode Hybridization in the Long-Range Interacting Kitaev Chain”, *Physical Review Letters* 137, 146503 (2026).

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