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Over the past few years, researchers have developed various quantum technologies, alternatives to classical devices that operate by leveraging the principles of quantum mechanics. These technologies have the potential to outperform their classical counterparts in specific settings or scenarios.

Among the many quantum technologies proposed and devised so far are quantum batteries, energy storage devices that could theoretically store energy more efficiently than classical batteries, while also charging more rapidly. Despite their predicted potential, most quantum battery solutions proposed to date have not yet proven to exhibit a genuine quantum advantage, or in other words, to perform better than their classical counterparts.

Researchers at PSL Research University and the University of Pisa recently introduced a new deceptively simple quantum battery model that could exhibit a genuine quantum advantage over a classical analog battery. The new model, outlined in a paper in ÌÇÐÄÊÓƵical Review Letters, was found to successfully reach the so-called quantum speed limit, the maximum speed that a quantum system could theoretically achieve.

"Quantum batteries are microscopic devices that can exhibit quantum advantages over their classical counterparts in energy-related tasks," Vittoria Stanzione and Gian Marcello Andolina, co-authors of the paper, told ÌÇÐÄÊÓƵ. "This research area originated from quantum information theory, which predicts that quantum resources—such as entanglement—can dramatically enhance the charging power of quantum systems.

"In recent years, some of the authors of the present work proposed a model displaying such a quantum advantage: the Sachdev–Ye–Kitaev (SYK) model. However, this model is highly complex, both experimentally—due to its many-body interactions—and theoretically, as it is analytically challenging."

Earlier works demonstrating a quantum advantage of batteries based on the SYK model only did so using numerical simulations, without performing any further analyses. Building on their earlier efforts, Stanzione, Andolina and their colleagues tried to identify the simplest possible quantum battery model that could display a quantum advantage in terms of charging power.

"Our model consists of two coupled harmonic oscillators: one acts as the 'charger,' and the other serves as the 'battery,'" explained Stanzione and Andolina. "The key ingredient enabling the quantum advantage is an anharmonic interaction between the two oscillators during the charging process. This anharmonic coupling allows the system to access non-classical, entangled states that effectively create a 'shortcut' in Hilbert space, enabling faster energy transfer than in classical dynamics."

To rigorously certify their model's quantum advantage, the researchers compared it to a suitable classical battery model, while also implementing a formal bound that was outlined by Maciej Lewenstein and other researchers at the Institute of Photonic Sciences (ICFO) in Barcelona. Overall, their findings suggest that their quantum battery model does outperform its classical counterpart.

"To the best of our knowledge, this work provides the first rigorous certification of a genuine quantum advantage in a solvable model," said Stanzione and Andolina. "Furthermore, the proposed setup can be realized with current experimental technologies."

So far, the researchers' model is merely theoretical, and much work still needs to be done before it can be realized experimentally. In their paper, the team briefly explores the possibility of realizing their proposed battery model using superconducting circuits, which are electrical circuits made of materials that exhibit a resistance of zero at low temperatures.

"We now plan to collaborate with experimental groups in the future to pursue a proof-of-principle realization," added Stanzione and Andolina. "At the same time, the development of a fully functional quantum battery—integrated with other quantum technologies—remains a distant goal. We hope that our work will stimulate further research on this exciting topic, fostering progress on both the theoretical and experimental fronts."

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