Researchers at the University of Twente and Utrecht University demonstrated for the first time that quantum states in the ultra-narrow material germanene can be switched on and off using only an electric field. The researchers were able to vary the electric field strength very precisely, causing the special ‘topological’ states in nanoribbons to disappear or appear.

The research, titled “Electric-Field Control of Zero-Dimensional Topological States in Ultranarrow Germanene Nanoribbons,” is published in Physical Review Letters.

Quantum computers will not use zeros and ones, but instead use quantum bits that can assume both states simultaneously. In theory, this makes them superfast and powerful, but in practice, building quantum bits is an enormous challenge: they are very sensitive to noise and quickly lose their information.

Quantum computers will be able to assume highly complex tasks in the future. With superconducting quantum processors, however, it has thus far been difficult to read out experimental results because measurements can cause interfering quantum state transitions.

Researchers at Karlsruhe Institute of Technology (KIT) and Université de Sherbrooke in Québec have performed experiments that improve our understanding of these processes and have shown that calibrating the charge at the qubits contributes to fault avoidance.

Their findings have been published in Physical Review Letters.

Scientists have taken another major step toward creating stable quantum computers. Using a specialized quantum computer chip (an essential component of a quantum computer) as a kind of tiny laboratory, a team led by Pan Jianwei at the University of Science and Technology of China has created and studied a rare and complex type of matter called higher-order nonequilibrium topological phases.

This digital matter (not conventional physical material) is unique because its key behaviors are super-stable and located only at its corners. But this stability is only maintained when the material is constantly bombarded with energy pulses.

The work is a big deal because it shows that quantum computers can be used as reliable simulators to discover and test new stable forms of matter. This will be necessary if scientists are to create quantum computers that never break down (or are at least highly reliable), because super-stable corner behaviors are the kind of error-proof properties needed to build trustworthy quantum hardware.

Over the past decades, physicists and quantum engineers introduced a wide range of systems that perform desired functions leveraging quantum mechanical effects. These include so-called quantum sensors, devices that rely on qubits (i.e., units of quantum information) to detect weak magnetic or electric fields.

Researchers at the HUN-REN Wigner Research Center for Physics, the Beijing Computational Science Research Center, the University of Science and Technology of China and other institutes recently introduced a new quantum sensing platform that utilizes silicon carbide (SiC)-based spin qubits, which store quantum information in the inherent angular momentum of electrons. This system, introduced in a paper published in Nature Materials, operates at room temperature and measures qubit signals using near-infrared light.

“Our project began with a puzzle,” Adam Gali, senior author of the paper told Phys.org. “Quantum defects that sit just a few nanometers below a surface are supposed to be fantastic sensors—but in practice, they pick up a lot of ‘junk’ signals from the surface itself. This is especially true in SiC. Its standard oxide surface is full of stray charges and spins, and those produce noise that overwhelms the quantum defects we actually want to use for sensing. We wanted to break out of this limitation.”