Physicists at TU Wien, led by Jörg Schmiedmayer and his team at the Atominstitut, have demonstrated a quantum system in which mass and energy move without any measurable loss. The group confined a cloud of ultracold rubidium atoms to a one-dimensional trap, forming what they describe as a quantum wire. In this setting, collisions do not cause scattering or friction. Instead, momentum is continuously passed along the atomic chain, allowing transport to remain stable even over long observation times. Their findings add to earlier theoretical and experimental work suggesting that certain one-dimensional quantum systems can support forms of flow that are resistant to dissipation.
Schüttelkopf, P., Tajik, M., Bazhan, N., Cataldini, F., Ji, S.-C., Schmiedmayer, J., & Møller, F. (2025). Characterizing transport in a quantum gas by measuring Drude weights. Science. https://doi.org/10.1126/science.ads8327
The researchers constructed the system using a combination of magnetic and optical fields on an atom-chip platform. This technology, which has been refined over the past decade at TU Wien, allows precise control of ultracold gases at length scales comparable to microfabricated structures. When the atoms were cooled into a quantum degenerate state and constrained to a single line, the usual transport processes found in everyday materials no longer applied. Instead of spreading out diffusively, mass and energy moved as if they were being transferred directly from one atom to the next.
Jörg Schmiedmayer from TU Wien stated,
“In principle, there are two very different types of transport phenomena. We speak of ballistic transport when particles move freely and cover twice the distance in twice the time, like a bullet traveling in a straight line.”
In typical materials, electrical, thermal, or mechanical transport eventually slows down because collisions randomize momentum. The group at TU Wien compared this familiar behaviour to diffusive heat conduction, in which energy spreads unevenly until it eventually smooths out. Their experiment, however, showed almost no evidence of diffusion. Measurements of atomic current revealed that the flow persisted without decreasing, even though collisions between atoms were frequent. According to the researchers, the atomic cloud behaved more like a perfect conductor than a conventional gas.
One way the team explains this observation is through the analogy of a Newton’s cradle. In that system, momentum moves linearly through the row of spheres without accumulating losses inside the chain. Something similar occurs in the quantum wire: each collision transfers momentum directly rather than scattering it into random directions. Because the atoms can only interact along one axis, their possible motion is tightly constrained. This restriction prevents the usual redistribution of energy that makes systems thermalize.
The TU Wien team analysed this behaviour by measuring so-called Drude weights, quantities used in condensed-matter physics to evaluate how well a system conducts without resistance. Data from the experiment aligned with predictions from integrable one-dimensional models, which have long suggested the existence of transport channels immune to dissipation. Related work in the field has explored how quasi-one-dimensional materials, such as certain spin chains or cold-atom lattices, can show similar behaviour, but direct measurement in an isolated and tunable gas has been limited.
The results help clarify why the atomic wire does not reach thermal equilibrium in the usual sense. Because momentum is conserved and passed forward rather than lost, the system lacks the mechanisms required to redistribute energy across all degrees of freedom. This also makes the platform valuable for studying how resistance emerges in quantum systems and how it may be avoided. Understanding these processes could support the design of new low-loss quantum circuits, inform the theory of strongly correlated systems, and potentially guide engineering approaches for coherent transport in quantum devices.
Although the experiment is primarily fundamental in nature, the researchers note that controlled one-dimensional systems provide a clean environment for testing questions that are otherwise difficult to probe in solid-state materials. As techniques for trapping and manipulating ultracold atoms continue to advance, systems like this may play a role in connecting quantum many-body theory with practical engineering applications. For now, the quantum wire offers a clear demonstration that mass and energy can propagate without friction under the right conditions, challenging the expectation that collisions in matter always lead to loss.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
