West LA Times

A team led by researchers from the California NanoSystems Institute at UCLA has designed a unique material based on a conventional superconductor, a substance that enables electrons to travel through it with zero resistance under certain conditions, such as extremely low temperature. The experimental material exhibited properties signaling its potential for use in quantum computing, a developing technology with capabilities beyond those of classical digital computers.

Conventional superconductors typically fail under magnetic fields of a certain strength. However, the new material retained superconducting properties under a much higher magnetic field than the theoretical limit of a conventional superconductor. The team also measured how large an electrical current the new material can accommodate before it breaks superconductivity, applying electricity from one direction and then again from the opposite direction. They found that one direction allowed notably higher current than the other, often referred to as the superconducting diode effect. In contrast, conventional superconductors would lose their zero-resistance property at equal current from either direction.

Quantum computers operate based on the counterintuitive rules governing subatomic particle interactions. The basic unit of information in quantum computing, the qubit, can have multiple values, unlike bits in classical computing which can only have one of two values.

While quantum computers could perform calculations that traditional computers cannot, the technology is still in its early stages with obstacles left to overcome before realizing its promise. One such obstacle is the fragility of qubits; minor changes in conditions can cause qubits to lose their quantum properties within millionths of a second.

Researchers have theorized that an unconventional type of superconductor called a chiral superconductor may help increase qubits’ ability to maintain accuracy while performing program steps. Both chiral and conventional superconductors depend on quantum phenomena where pairs of electrons become linked at a distance in a state known as entanglement. In conventional superconductors, entangled electrons move and spin in opposite directions. In chiral superconductors, entangled electrons could spin in the same direction and abide by complex rules potentially opening new possibilities for tailoring current flow or processing information.

The activity of electrons in conventional superconductors displays symmetries broken in chiral superconductors favoring flow in one direction over another as seen in the superconducting diode effect. Today, only a few compounds are candidates for chiral superconductivity and they are extremely rare. In this study, researchers found a way to customize their material to coax a conventional superconductor to act like a chiral one.

The UCLA-led team created a lattice with alternating layers: one layer made of tantalum disulfide (a conventional superconductor) was as thin as three atoms; another layer was made of “left-handed” or “right-handed” molecular layers of different compounds. They tested tiny nanoscale devices made from their lattice to evaluate whether the material showed properties of a chiral superconductor.

Quantum computing may yield innovations such as unbreakable cybersecurity, advanced artificial intelligence and high-fidelity simulations ranging from drug actions within bodies to city traffic flows and financial market fluctuations. To achieve these applications, quantum computers must improve their ability to function despite disturbances affecting fragile qubits. Superconducting circuits are foundational to many quantum computing approaches and achieving the superconducting diode effect via chiral superconductors is expected to be useful for creating more efficient and stable qubits.

In addition to its utility for quantum computing, chiral superconductors’ diode effect could make electronics and communication technologies operate faster while minimizing energy consumption — qualities particularly suited for specialized applications like deep space computers working at extremely low temperatures.

Engineering chiral superconductors from more readily available ingredients — as demonstrated by this study’s hybrid material — could help unlock quantum computing’s potential while driving improvements in electronic devices.

The study’s corresponding authors are CNSI members Yu Huang (Traugott and Dorothea Frederking Endowed Professor and chair of materials science and engineering department at UCLA Samueli School of Engineering), Kang Wang (Raytheon Company Professor of Electrical Engineering and distinguished professor at UCLA Samueli), and Xiangfeng Duan (professor of chemistry and biochemistry at UCLA College). Co-first authors include Zhong Wan (UCLA postdoctoral researcher) and Gang Qiu (former UCLA postdoctoral researcher now faculty at University of Minnesota). Other co-authors are Huaying Ren, Qi Qian, Yaochen Li, Dong Xu, Jingyuan Zhou, Jingxuan Zhou, Boxuan Zhou, Laiyuan Wang and Ting-Hsun Yang (all from UCLA) along with Zdeněk Sofer from University of Chemistry and Technology Prague.

There are no disclosures associated with this research which was published in Nature journal supported by U.S Office Naval Research Army Research Office Czech Republic Ministry Education Youth Sports Advanced Functional Nanorobots project.