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A new approach to probing Landauer's principle in the quantum many-body regime

Landauer's principle is a thermodynamics concept also relevant in information theory, which states that erasing one bit of information from an information system results in the dissipation of at least a specific amount (i.e., k_BTln2) of energy. This principle has so far been primarily considered in the context of classical computers and information processing systems.

Yet researchers at TU Vienna, the Freie Universität Berlin, the University of British Columbia, the University of Crete and the Università di Pavia recently extended Landauer's principle to quantum many-body systems, systems made up of many interacting quantum particles.

Their paper, in Nature Â鶹ÒùÔºics, introduces a viable approach to experimentally probe this crucial principle in a quantum regime and test theoretical predictions rooted in quantum thermodynamics.

"It has long been recognized that the concepts of thermodynamics and information are deeply intertwined," Jens Eisert, senior author of the paper, told Â鶹ÒùÔº.

"Pioneers like Boltzmann and Gibbs were guided by profound insights into how the knowledge we have about a system shapes its meaningful description—an understanding later enriched by Shannon's foundational work in abstract information theory. At its core, information governs the behavior of thermodynamic systems, determining whether energy is channeled into useful work or dissipated as heat."

Two different thought experiments carried out by physicists James Clerk Maxwell and Leo Szilard in the 1860s and 1920s, respectively, were among the first to introduce the idea that thermodynamics arises from incomplete information. This idea ultimately challenged previous theories, outlining paradoxes that emerge under some hypothetical assumptions about one's access to information in a system.

The recent study by Eisert and his colleagues builds on these earlier works, while also leveraging an experimental platform developed by Jörg Schmiedmayer. This platform essentially consists of an atom chip architecture that offers exceptional control over ultracold atoms in continuous settings.

"Our interest centered on how concepts such as information deletion and heat production might manifest in this uniquely tunable quantum regime," said Eisert. "This naturally brought us to Landauer's principle, which asserts that erasing information necessarily involves the dissipation of heat into the environment—a fundamental connection between thermodynamics and information."

Landauer's principle has been widely studied in the past, thus it does need to be verified in an experimental setting. Instead, the researchers wanted to further explore its implications in the context of quantum many-body systems, as this could enrich both the understanding of the principle and of the studied systems.

"It is precisely with this perspective—both theoretical and experimental—that we set out to investigate," explained Eisert. "In our work, we precisely track the time evolution of a quantum field subjected to a global mass quench—from a massive to a massless Klein–Gordon model, a prototypical quantum field theory. We analyze the thermodynamic and information-theoretic contributions to generalized entropy production across various system–environment partitions of the composite system."

To test Landauer's principle in a complex quantum system, Eisert and his colleagues employed a quantum field simulator, a system that can be used to simulate the quantum mechanics-guided behavior of particles and fields. Their simulator relied on ultracold Bose gas atoms, which are known to behave like quantum systems when cooled down to temperatures around absolute zero. The experimental work for this study was carried out at a leading laboratory led by Jörg Schmiedmayer at TU Vienna.

Notably, the results of the team's quantum simulations were aligned with predictions rooted in quantum field theory, a framework that describes the behavior of particles and fields based on the laws of quantum mechanics. To explain their findings, the researchers combined classical physics theories with quantum corrections, thus employing a semi-classical quasiparticle framework.

"Methodologically, this is enabled by a dynamical tomographic reconstruction scheme we have co-developed, which exploits selected instances of time evolution to access and reconstruct otherwise incompatible quantum properties," said Eisert. "Our study first helps us understand better how Landauer's principle manifests itself in this quantum field theoretical setting, as a fundamental insight about nature.

"More technologically speaking, however, it helps us to better understand this experimental platform to develop it further to a thermodynamical engine acting in or close to the quantum mechanical regime."

This study highlights the potential of quantum simulators based on ultracold atoms for probing concepts rooted in quantum thermodynamics. In the future, it could inspire other research teams to perform similar experiments, which could eventually inform the development of new quantum processors and other quantum technologies.

"We would now like to together explore this platform better, develop it into a thermal machine, see entanglement and quantum correlations at work," added Eisert. "It is a fascinating playground for this."