IST Austria Researchers, International Team Develop Promising New Qubit with Holes

(HPCWire) Scientists from the Katsaros group at the Institute of Science and Technology (IST) Austria together with an international team of researchers have now created a new setup to control the absence of electrons in a solid material. They want to use these holes as a basis for a quantum computer.
Quantum computers with their promises of creating new materials and solving intractable mathematical problems are a dream of many physicists. Now, they are slowly approaching viable realizations in many laboratories all over the world. But there are still enormous challenges to master. A central one is the construction of stable quantum bits – the fundamental unit of quantum computation called qubit for short – that can be networked together.
A study led by Daniel Jirovec from the Katsaros group at IST Austria in close collaboration with researchers from the L-NESS Inter-university Centre in Como, Italy, scientists now have created a new and promising candidate system for reliable qubits.
The researchers created the qubit using the spin of so-called holes. Each hole is just the absence of an electron in a solid material. Amazingly, a missing negatively charged particle can physically be treated as if it were a positively charged particle. It can even move around in the solid when a neighboring electron fills the hole. Thus, effectively the hole described as positively charged particle is moving forward.
In their setup, Jirovec and his colleagues cannot only move holes around but also alter their properties. By engineering different hole properties, they created the qubit out of the two interacting hole spins using less than ten millitesla of magnetic field strength. This is a weak magnetic field compared to other similar qubit setups, which employ at least ten times stronger fields.
But why is that relevant? “By using our layered germanium setup we can reduce the required magnetic field strength and therefore allow the combination of our qubit with superconductors, usually inhibited by strong magnetic fields,” Jirovec says. Superconductors – materials without any electrical resistance – support the linking of several qubits due to their quantum-mechanical nature. This could enable scientists to build new kinds of quantum computers combining semiconductors and superconductors.