QuTech develops germanium transistors for quantum computers

Researchers from TNO and QuTech have developed a germanium-based transistor that has good properties to serve as a qubit for quantum computers. They demonstrate calculations with the transistor.

It has been known for some time that germanium is a suitable material to base quantum bits on and researchers worldwide are working on this. For a long time there were problems with its manufacture and it was also not yet possible to perform quantum calculations with only these transistors. The researchers at TNO and QuTech have now succeeded in producing working transistors based on germanium in a relatively short period of time. “Germanium has been developed in just over a year from a material that allows stable construction to a platform on which quantum calculations are performed,” says Nico Hendrickx of QuTech.

The researchers show that a single germanium transistor can function as a quantum bit, paving the way for wider use. More precisely, they demonstrate a universal quantum gate with a gate time of 20 nanoseconds and a two-qubit computation performed in 75 nanoseconds.

They describe that on the one hand, quantum dots based on gallium arsenide, or GaAs, have shown good properties for controlling the qubits, while on the other hand, reliable quantum calculations with two qubits based on silicon can be performed. The transistors, or more precisely hole quantum dots, based on germanium would combine these good properties.

The very first transistors were based on germanium in the 1940s, but silicon was then favored by the semiconductor industry because it is cheaper and easier to use in manufacture.

The researchers describe their work under the title Fast two-qubit logic with holes in germanium in the scientific journal Nature.

Illustration of two quantum bits based on a germanium transistor