Plate Nº 85 · recorded October 13, 2026
PhysicsReported finding
Researchers spot islands of order in 24-qubit quantum chaos
Researchers from Zhejiang University and the University of Leeds, reporting in Nature Physics on October 5, 2026, identified the first stable 'islands' of regular motion within an otherwise chaotic quantum many-body system.
By Priya Raman4 min read704 words
In brief
- October 5, 2026: Findings published in Nature Physics (DOI: 10.1038/s41567-026-03431-z).
- 24-qubit superconducting ladder drawn from a processor containing more than 100 qubits.
- Joint team from Zhejiang University and the University of Leeds, led by Hang Dong and Zlatko Papić.
- Method requires only short quantum evolution and simple single-qubit measurements per round.
- Builds on a previous Nature Physics paper demonstrating 30-qubit quantum scars on a superconducting processor.
Twenty-four superconducting qubits, arranged in a ladder and steered through a feedback loop with a classical computer, settled into a repeating rhythm on October 5, 2026. The experiment, published in Nature Physics, marks what its authors describe as the first direct observation of stable "islands" of regular motion within a quantum many-body system whose overall behavior is chaotic.
The work was led by Hang Dong of Zhejiang University and Zlatko Papić of the University of Leeds, with contributions from postdocs Jie Ren and Andrew Hallam at Leeds.
What did the team actually build?
The 24-qubit ladder (a two-row arrangement of interacting quantum bits) was selected from a superconducting processor containing more than 100 qubits. Superconducting qubits are tiny electrical circuits that behave according to the rules of quantum mechanics when cooled to near absolute zero.
In each round, the researchers prepared a chosen quantum state on the ladder, let it evolve briefly, and then measured each qubit. A classical computer used those measurements to propose a simpler state resembling the result.
That updated state was loaded back onto the processor, and the cycle repeated. After many iterations, the loop converged on a pattern that returned to itself, even though no one had specified the target.
"The most striking finding is that there exist whole 'islands' of regular motion within a sea of chaotic behavior," Papić said.
How does this connect to earlier work?
The new study builds on a previous Nature Physics paper in which the same collaboration showed that carefully chosen starting states in a 30-qubit superconducting processor could repeatedly return close to their initial configuration.
That earlier phenomenon, known as quantum scars, describes recurring patterns that survive in systems otherwise expected to drift toward disorder. The earlier work led the team to ask whether such recurrences might belong to a larger, more general pattern.
What is hybrid feedback control?
The procedure alternates between quantum and classical steps, hence the label "hybrid." Each round requires only a short burst of quantum evolution and simple single-qubit measurements, which makes the method compatible with current processors that struggle to preserve delicate quantum behavior for long periods.
Ren and Hallam developed the theoretical backbone. They used tensor networks, a class of mathematical tools that represent complex quantum states compactly. Hang Dong and other Zhejiang collaborators then implemented the protocol on the hardware. The approach generalizes an algorithm called ScarFinder, which the team introduced earlier in PRX Quantum to search for recurring patterns tied to quantum many-body scars.
The researchers also observed that the shape of each regular island changed as they tuned the strength of the interactions between neighboring qubits. The islands were always present in the system's underlying behavior; the feedback loop simply made them visible.
What does the solar system comparison mean?
Papić draws a single concrete analogy with classical mechanics. "This structure of regular motion coexisting with chaos is very common in classical systems, e.g., the solar system works like this (planets move seemingly periodically, while the system's overall motion is chaotic and impossible to predict at very late times)," he said.
The new result suggests that quantum many-body systems can host the same coexistence between periodic islands and chaotic motion.
What comes next?
Larger studies lie ahead. Papić and his colleagues now plan to map which quantum systems support regular islands, what controls their stability, and how the islands evolve as the number of qubits grows.
They also want to clarify whether previously reported quantum scars are special cases within this broader phenomenon, or whether the two effects sometimes stand apart.
"Our approach gives us a practical way to explore this landscape experimentally," Papić said. "A broader implication of this study is that quantum processors can serve as instruments of scientific discovery. Learning how to find and control these regular motions could eventually help us preserve useful quantum behavior for longer."
A 24-qubit experiment cannot resolve whether these islands persist at the scale of hundreds or thousands of qubits, and the team plans to find out.
The paper, "Quantum many-body mixed phase space revealed by hybrid feedback control" (DOI: 10.1038/s41567-026-03431-z), appears in Nature Physics.
via Phys.org Physics (Source)
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Senior reporter covering people, launches and day-to-day practice in general science news at SciBeat.
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