EU-Funded Researchers Create New Qubit System Using Spin of So-Called Holes

(EU.CORDIS) EU-funded researchers have created a promising new qubit system based on the interacting spins of holes confined in a nanosized silicon-germanium quantum device.
The MaGnum and microSPIRE projects have now developed a potential new system for reliable qubits using the spin of so-called holes.
Holes in materials such as the metalloid germanium are excellent candidates for spin qubits. The scientists built a nanostructure of various layers of germanium and silicon, making it possible for them to confine holes in a practically bi-dimensional region. Study lead author Daniel Jirovec of MaGnum project coordinator Institute of Science and Technology Austria described their collaboration with the Laboratory for Nanostructure Epitaxy and Spintronics on Silicon (L-NESS) at microSPIRE project coordinator Polytechnic University of Milan. “Our colleagues at L-NESS layered several different mixtures of silicon and germanium just a few nanometers thick on top of each other. That allows us to confine the holes to the germanium-rich layer in the middle,” explained Jirovec in a news item posted on ‘HPCwire’. “On top, we added tiny electrical wires – so-called gates – to control the movement of holes by applying voltage to them. The electrically positively charged holes react to the voltage and can be extremely precisely moved around within their layer.”
The research team used this technique to move two holes close to each other so that their spins would interact, in this way creating a spin qubit. More importantly, they were able to create the qubit out of the 2 interacting hole spins using less than 10 milliteslas of magnetic field strength – a value substantially weaker than the magnetic fields of other qubit set-ups