Physicists at the Department of Physics at Universität Hamburg have made a groundbreaking discovery by observing a quantum state that was theorized over 50 years ago. By pairing electrons in an artificial atom on a superconductor, the researchers were able to create a basic version of superconductivity. This discovery sheds light on the behavior of paired electrons, known as bosons, which can coexist in the same space unlike single electrons.
The study, published in the journal Nature, demonstrates the potential for advancing the understanding of superconductivity in nanoscale structures and its application in modern quantum computers.
Electrons typically repel each other due to their negative charge, which influences various material properties, including electrical resistance. However, when electrons are paired together to form bosons, they can coexist and move in sync. This phenomenon is crucial for superconductivity, which allows electrical current to flow without any resistance. Superconductivity has been utilized in technologies such as magnetic resonance imaging and magnetic field detectors.
The researchers from Universität Hamburg achieved the pairing of electrons in an artificial atom called a quantum dot, which serves as the smallest building block for nanostructured electronic devices. They constructed tiny cages for the electrons using silver atoms. By coupling these locked electrons to a superconductor, they inherited the tendency towards pairing from the superconductor.
The team of theoretical physicists at the Cluster of Excellence “CUI: Advanced Imaging of Matter,” led by Dr. Thore Posske, related the experimental signature of the paired electrons to a quantum state predicted by Japanese theoreticians Kazushige Machida and Fumiaki Shibata in the early 1970s.
While the quantum state had previously eluded direct detection, recent research from teams in the Netherlands and Denmark has shown its potential for suppressing unwanted noise in transmon qubits, a crucial component of modern quantum computers.
In response to the publication, Kazushige Machida expressed his gratitude to the researchers for “discovering” his old paper from half a century ago. He had long believed that transition metal non-magnetic impurities produced the in-gap state, but its location near the superconducting gap edge made it impossible to prove its existence. The researchers’ ingenious method finally confirmed the validity of his theory experimentally.
This discovery opens up new possibilities for understanding and harnessing superconductivity in nanoscale structures, paving the way for advancements in quantum computing and other technological applications.
Reference:
“Proximity superconductivity in atom-by-atom crafted quantum dots” by Lucas Schneider, Khai That Ton, Ioannis Ioannidis, Jannis Neuhaus-Steinmetz, Thore Posske, Roland Wiesendanger, and Jens Wiebe, Nature, August 16, 2023.
DOI: 10.1038/s41586-023-06312-0
What potential applications can arise from a deeper understanding and manipulation of paired electrons in the field of superconductivity
D particle accelerators.
To observe this quantum state, the researchers fabricated an artificial atom on a superconducting platform. By carefully controlling the number of electrons in the system, they were able to pair them up, forming bosons. This pairing, known as Cooper pairing, is a fundamental concept in superconductivity theory.
Using a technique called tunnel spectroscopy, the scientists were able to measure the energy required to break the Cooper pairs. They found that the energy required was in agreement with theoretical predictions made over 50 years ago, confirming the existence of this long-theorized quantum state.
This groundbreaking discovery opens up new possibilities for studying and manipulating superconductivity at the nanoscale level. By understanding the behavior of paired electrons, researchers may be able to develop more efficient and robust superconducting materials for use in various applications, including quantum computers.
Quantum computers rely on the principles of quantum mechanics to perform incredibly complex calculations. Superconducting materials are a promising platform for building these computers because of their ability to carry electrical current without resistance. This discovery brings us one step closer to realizing the full potential of quantum computing.
In addition to its applications in computing, superconductivity also has broader implications for energy storage and transmission. With superconductors, energy losses during transmission can be significantly reduced, leading to more efficient power grids and a greener energy future.
The researchers at Universität Hamburg have made a significant contribution to the field of superconductivity with this breakthrough discovery. Their findings not only confirm a long-standing theory but also pave the way for further advancements in the understanding and application of superconductivity in nanoscale structures.
