Scientists successfully manipulate qubits with electrical fields

Scanning electron image of the nanowire device with gate electrodes used to electrically control qubits, and source and drain electrodes used to probe qubit states

Until now, the common practice for manipulating the electron spin of quantum bits, or qubits, – the building blocks of future super-fast quantum computers – has been through the use of magnetic fields. Unfortunately, these magnetic fields are extremely difficult to generate on a chip, but now Dutch scientists have found a way to manipulate qubits with electrical rather than magnetic fields. The development marks yet another an important development in the quest for future quantum computers, which would far outstrip current computers in terms of speed.

Just like a normal computer bit, a qubit can adopt the states ‘0’ and ‘1’. One way to make a qubit is to trap a single electron in semiconductor material. It’s state can be set by using the spin of an electron, which is generated by spinning the electron on its axis. As it can spin in two directions, one direction represents the ‘0’ state, while the opposite direction represents the ‘1’ state.

Until now, the spin of an electron has been controlled by magnetic fields but the scientists from the Kavli Institute of Nanoscience at Delft University of Technology and Eindhoven University of Technology have now succeeded in controlling the electron spin in a qubit with a charge or an electric field.

According to Leo Kouwenhoven, scientist at the Kavli Institute of Nanoscience at TU Delft this form of control has major advantages. "These spin-orbit qubits combine the best of both worlds. They employ the advantages of both electronic control and information storage in the electron spin," he said.

In another important quantum computing development, the scientists have also been able to embed these qubits into semiconductor nanowires. The scientists were able to embed two qubits in nanowires measuring just nanometers in diameter and micrometers in length made of indium arsenide.

"These nanowires are being increasingly used as convenient building blocks in nanoelectronics. Nanowires are an excellent platform for quantum information processing, among other applications," said Kouwenhoven.

The scientists’ findings appear in the current issue of the journal Nature.