Long-lived qubits in silicon
One of the challenges of building a future quantum computer is to develop qubits that are both scalable and robust. Researchers at the Kavli Institute of Nanoscience Delft and the University of Wisconsin have now demonstrated that a long-lived qubit can survive in silicon, the most widely used material in the modern semi-conductor industry. The research, which was partially funded by FOM, was published in Nature Nanotechnology on 10 August 2014.
A quantum computer can be used to solve problems that even a supercomputer cannot answer. One of the main challenges is the fact that qubits are easily disturbed by even the slightest interference in the environment. A lot of work is now going into developing qubits in surroundings with a minimum of disturbance.
Spin
A qubit is represented by the minuscule magnetic moment of an electron, known as the ‘spin’. In previous experiments involving qubits in semi-conductors, the qubits were affected by the presence of other spins in the surroundings, which disturbed the electron spin and rendered the qubit useless. These other spins were bound to the atom nuclei in the material confining the electron spin. In silicon, where spin only occurs in 5% of all atom nuclei, researchers expect the qubit to experience far less disruption.
100 times longer-lived
The researchers from Delft and Wisconsin showed that in silicon, electron spin survived almost 100 times longer than in previous experiments using the most commonly used material up until then (Gallium arsenide). Whereas the state of spin used to remain at approximately 10 nanoseconds, the researchers were now able to extend the lifespan of spin in a qubit in silicon to 1 microsecond. Although this may not seem very long, if it is long enough to make calculations, 1 microsecond is long enough.
Future of qubits
These results are promising for the future of qubits in semi-conductors. Further improvements to the lifespan of qubits will be possible if the silicon can be purified so that it only contains the atoms without nuclear spin. Silicon is compatible with the most common semi-conductor technology (CMOS) currently used in all kinds of equipment. As the technology already exists, integrating qubits should be a far quicker process.
More information
For more information, please contact:
Pasquale Scarlino, Kavli Institute of Nanoscience Delft
Carola Poleij, science information officer at TU Delft, +31 (0)6 182 421 97