Physicists confirm the quantum state predicted more than 50 years ago

Physicists observed a quantum state, theorized more than 50 years ago, by pairing up electrons in an artificial atom on a superconductor, creating a basic version of superconductivity. This discovery displays the behavior of paired electrons (bosons) that can coexist in the same space, unlike single electrons. This work has implications for furthering the understanding of superconductivity in nanostructures and its potential application in modern quantum computers.

Discover the coupling of electrons in artificial atoms

Researchers from the University of Hamburg’s Department of Physics have observed a quantum state that was theoretically predicted by Japanese theorists more than 50 years ago, but has so far eluded discovery. by synthetic suture corn On the surface of a superconductor, the researchers have succeeded in pairing up the electrons of a so-called quantum dot, thus creating the smallest possible version of the superconductor. The work appears in the latest issue of the magazine nature.

Electron behavior and superconductivity

Electrons usually repel each other because of their negative charge. This repulsion phenomenon plays an important role in influencing many properties of materials, among which is the electrical resistance. However, the situation changes radically if the electrons are “glued” together in pairs and thus become bosons. Unlike lone electrons, which repel each other, boson pairs can coexist in the same space and perform identical motions.

Atom was built by Atom out of silver

3D rendering of some of the structures built atom by atom out of silver (little hills). A rectangular and circular letter cage is shown in the upper left quadrant of the image. Credit: Lucas Schneider

Superconductivity is one of the most interesting properties of materials containing these pairs of electrons – the ability to allow electric current to pass without any resistance. Superconductivity has been harnessed for many technological applications over the years, such as magnetic resonance imaging and highly sensitive magnetic field detectors. With the continued miniaturization of electronic devices, there is a growing interest in understanding how to achieve superconductivity in smaller, nanoscale structures.

Electron coupling in artificial atoms

Researchers from the Department of Physics and the Excellence Group “CUI: Advanced Imaging of Matter” at the University of Hamburg have realized the coupling of electrons in an artificial atom called a quantum dot, the smallest building block for nanostructured electronic devices. To this end, the experimenters, led by PD Prof. Jens Wiebe of the Institute for Nanostructure and Solid State Physics, trapped electrons in tiny cages they built of silver, atom by atom.

By coupling the locked electrons to an elemental superconductor, the electrons inherited the tendency toward pairing from the superconductor. Together with a team of theoretical mass physicists, led by Dr. Thor Boesky, the researchers correlated the experimental signature, a spectral peak at very low energy, with the quantum state predicted by Kazushige Machida in the early 1970s by Fumiaki Shibata.

While the state has so far only recovered direct detection by experimental methods, recent research by two teams from the Netherlands and Denmark shows that it is useful in suppressing unwanted noise in qubit transmissions, a building block of modern quantum computers.

In a private email, Kazushige Machida wrote to the publication’s first author, Dr. Lucas Schneider: “Thank you for ‘discovering’ my old paper half a century ago. I thought for a long time that non-magnetic transition metal impurities produce the gap state, but their location is very close to the edge of the gap.” superconducting, and therefore impossible to prove its existence. But by your ingenious method I have at last verified that it is experimentally correct.”

Reference: “Approximated Superconductivity in Quantum Dots Made Atom-by-Atom” By Lukas Schneider, Khai That Ton, Eunice Ionides, Janice Neuhaus Steinmetz, Thor Boesky, Roland Weisendinger, and Jens Wiebe, Aug. 16, 2023, Available Here. nature.
DOI: 10.1038/s41586-023-06312-0

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