Building a silicon quantum computer chip atom by atom

A University of Melbourne led team has perfected a technique for embedding single atoms in a silicon wafer one-by-one. Their technology offers the potential to make quantum computers using the same methods that have given us cheap and reliable conventional devices containing billions of transistors.

Until now, implanting atoms in silicon has been a haphazard process. A silicon chip gets showered with phosphorus which implant in a random pattern, like raindrops on a window.

However, this new research – published in Advanced Materials and assisted by ANFF-VIC and ANFF-NSW – demonstrates a far more predictable and repeatable method. “We embedded phosphorus ions, precisely counting each one, in a silicon substrate creating a qubit “chip”, which can then be used in lab experiments to test designs for large scale devices,” lead author Professor David Jamieson of The University of Melbourne explained.

The team drilled a tiny hole in an AFM cantilever, so that when it was showered with phosphorus atoms one would occasionally drop through the hole and embed in the silicon substrate.

The key, however, was knowing precisely when one atom – and no more than one – had become embedded in the substrate. Then the cantilever could move to the next precise position on the array.

The team discovered that the kinetic energy of the atom as it ploughs into the silicon crystal and dissipates its energy by friction can be exploited to make a tiny electronic ‘click’.

Read more about the approach on the University of Melbourne website.