Quantum effects: New blueprint for single-atom transistors
The most important component of a computer - so small that quantum physics takes over. Researchers have now demonstrated in the laboratory how to control electricity with just one atom.
For decades, chip manufacturers have been researching how to produce ever smaller transistors. The on/off switches are the central element of a computer chip. The smaller they are made, the more of them can be accommodated and the more powerful the computer is. At the lower end of the size scale, however, there is more than just an increase in performance: if the component shrinks below a certain limit, quantum effects dominate the process. And with these, it may one day be possible to build a quantum computer suitable for everyday use.
Researchers led by Richard Silver from the US National Institute of Standards and Technology now describe how to produce reliable transistors whose central element consists of just a single atom in the scientific journal "Nature Communications". They use the regular atomic lattice of a silicon surface to arrange phosphorus atoms in such a way that gaps of a precisely defined length are created between them. If a voltage is applied to the construct, individual electrons can repeatedly jump from phosphorus atom to phosphorus atom so that current flows between them.
The decisive factor here is that the electrons can only make the jump thanks to the quantum physical effect of tunnelling. They overcome a barrier that they cannot actually overcome. By changing the gaps between the atoms by a few nanometres, Silver and his team were able to manipulate the tunnelling properties of the transistor in a targeted manner.
A long way from theory to practice
The study is still purely basic research. The researchers have no concrete application in mind. However, as the transistor works strictly according to quantum physics principles, it could also be used to utilise other quantum effects - such as entanglement, which is generally required to build qubits. Qubits or quantum bits form the basis of every quantum computer and can be technically realised in a wide variety of ways. The best way to do this is still largely unclear.
Silver and colleagues praise the reliability of their manufacturing process. The fabrication of single-atom transistors is a "difficult and complex process that everyone has to gain their own experience with. But we have now written down what steps are necessary so that other teams no longer have to proceed according to trial and error," says Silver's co-author Curt Richter in a press release from the US authority NIST.
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