Physicists Prove Long-Suspected Quantum Speed Limit for Thermalization

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When waiting for the ice on a car window to melt in winter, or for a warm drink to cool down, the time it takes for an object to reach a stable and balanced temperature with its surroundings (thermal equilibrium) depends on numerous factors. These include surface area, the material properties of the object, and air flow.

However, as we approach the subatomic scale at which qubits operate in quantum computers, a different set of rules comes into play. External conditions still matter, but according to a new article published in Nature Physics, quantum mechanics imposes a fundamental speed limit on how fast different quantum systems can reach thermal equilibrium.

The significance of this finding is that this limit is universal. No matter how much energy is applied, or however strongly a system is driven, the process cannot be forced to happen faster.

The 検索 for a Universal Speed Limit

For years, physicists have observed hints of this Planckian bound in superconductors and quantum systems, leading them to suspect the existence of a universal speed limit. However, a general mathematical proof establishing such a bound had been missing.

At this point, Paolo Abiuso of the Austrian Academy of Sciences and his colleagues take the stage.

Researchers developed a universal mathematical framework that treats thermalization as a process capable of driving various quantum systems toward their corresponding thermal states. Using quantum information theory, they calculated how quickly this could occur under the laws of quantum mechanics.

To make their findings concrete, the team applied their equations to a theoretical model of interacting quantum particles and examined their behavior mathematically.

An unbreakable speed limit

So, what conclusion did all these numerical calculations and formalization lead to?

The team demonstrated that quantum mechanics imposes a speed limit on how fast different quantum systems can reach thermal equilibrium. They discovered that this limit is determined by temperature and by two fundamental constants of nature: the reduced Planck constant and the Boltzmann constant.

“This limit arises from the observation that the thermalization machine cannot violate the Heisenberg limit [a fundamental limit on how precisely quantum properties can be measured],” the paper’s authors write.

This means that the minimum time required for quantum systems to reach thermal equilibrium can be shorter at higher temperatures, but when applicable, they still cannot exceed this fundamental speed limit. Their findings confirm that this speed limit depends on temperature and quantum mechanics, regardless of how complex the surrounding environment is.

However, at extremely low temperatures, the cutoff is determined by the energy difference between the system’s two lowest energy states.

This article is much more than an ingenious piece of mathematical work. Understanding these universal speed limits can help researchers develop better quantum computers, among other applications.

This article was written by Paul Arnold, edited by Lisa Lock, and fact-checked and reviewed by Robert Egan; it involved careful human effort in its preparation. Science X relies on the support of its readers to maintain independent science journalism. If this news is important to you, you may consider making a donation, particularly a monthly contribution. As a thank-you, you’ll receive an ad-free account.

Paolo Abiuso ve ark., Isınma için Planck sınırı bilgi teorisinden kanıt, (2026). DOI: 10.1038/s41567-026-03397-y

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