Programmable and deterministic chiral transfer of an entangled state between two distant giant superatoms, each comprising two or more correlated atoms. Credit: Du et al.

Quantum technologies are systems that leverage quantum mechanical effects to perform computations, share information or perform other functions. These systems rely on quantum states, which need to be reliably transferred and protected against decoherence (i.e., a gradual loss of quantum information).

In recent years, quantum physicists and engineers have introduced so-called giant atoms, artificial structures that behave like enlarged atoms and could be used to develop quantum technologies. In a recent paper published in Physical Review Letters, researchers at Chalmers University of Technology built on this concept and introduced new carefully engineered giant ‘superatoms’ (GSAs), a new type of giant-atom-like structures that could generate entanglement and enable the reliable transfer of quantum states between different such devices.

"Over the past years, there has been growing interest in so-called ‘giant atoms,’ which are quantum emitters that couple to their environment at multiple, spatially separated points," Lei Du, first author of the paper, told Phys.org.

"These setups allow light emitted from one coupling point to interfere with light from another, leading to unusual quantum effects like decoherence-free behavior and chiral (directional) emission. Our inspiration was to go a crucial step further by asking: what happens when you introduce internal interactions to such nonlocal quantum systems?"

Building on earlier works, Du and his colleagues devised the concept of GSAs, composite systems made up of two or more artificial atoms that collectively behave as a higher-dimensional (multilevel) giant quantum emitter. A key objective of their recent study was to explore the potential of these systems for the generation, control and distribution of quantum entanglement, while preventing decoherence.

A shift from giant atoms to giant superatoms

Giant atoms are atom-like systems with discrete energies that behave in ways that are aligned with the laws of quantum mechanics. As part of their study, the researchers set out to develop new giant-atom-like systems whose effective energy levels are collectively formed by two or more coupled artificial atoms.

"Giant atoms are dubbed ‘giant’ because they are larger than the wavelength of light that they interact with, which is very different from usual atoms," explained Janine Splettstoesser, co-senior author of the paper.

"The GSAs introduced here are groups of artificial atoms which are strongly connected to each other and have coupling points arranged such that the group becomes ‘giant.’ This arrangement opens possibilities for radically new concepts."

In their paper, the research team introduced two GSA configurations characterized by different coupling-point arrangements. These include braided GSAs, in which the coupling points of the GSAs intertwine, and separate GSAs, in which these couplings do not intertwine.

Braided GSAs were found to be promising for the transfer or swapping of quantum information between them while retaining quantum coherence. Separate GSAs, on the other hand, were found to be better suited for the realization of chiral emission, a phenomenon that entails the emission of photons that preferentially travel in one direction along a waveguide or optical interface.

"We showed how GSAs can be engineered to deterministically transfer entangled states from one place to another without losing information—something that’s crucial for building quantum communication systems," said Splettstoesser.

Possibilities for advancing quantum technologies

The researchers showed that carefully engineered GSAs could be promising platforms for realizing decoherence-free transfer of quantum states and state-dependent chiral emission. In the future, the GSA configurations they introduced could be leveraged to create networks of quantum devices or distributed quantum computing systems.

"I believe the key achievement of the paper is the conceptual leap from giant atoms to GSAs," said Anton Frisk Kockum, co-senior author of the paper.

"Going from small to giant atoms ten years ago opened our eyes to simple, yet powerful interference effects that had not previously been exploited. Now we extend the applications of these interference effects to a much larger class of systems."

In recent years, giant atoms have proven to be promising systems for protecting and controlling quantum information. Du, Splettstoesser, Kockum and their collaborator Xin Wang hope that GSAs will offer similar benefits but on a larger scale, facilitating the reliable transfer of quantum information between different systems or devices.

"We’re very interested in exploring how GSAs behave in more exotic environments, such as topological or non-Hermitian photonic structures," added Du.

"These environments could offer new ways to protect entanglement or guide photons in unusual ways. Another promising direction for future research is to extend our proposal to higher-excitation manifolds or continuous-variable systems, where more complex quantum states can be efficiently accessed and manipulated. Ultimately, our goal is to move from theoretical proposals to practical quantum technologies that leverage the unique properties of GSAs."

Written for you by our author Ingrid Fadelli, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You’ll get an ad-free account as a thank-you.

More information: Lei Du et al, Dressed Interference in Giant Superatoms: Entanglement Generation and Transfer, Physical Review Letters (2025). DOI: 10.1103/crzs-k718.

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Citation: Newly engineered giant superatoms show promise for reliable quantum state transfer (2025, December 15) retrieved 15 December 2025 from https://phys.org/news/2025-12-newly-giant-superatoms-reliable-quantum.html

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