Atom by Atom

Quantum computers could be constructed cheaply and reliably using a new technique perfected by a University of Melbourne-led team that embeds single atoms in silicon wafers, one-by-one, mirroring methods used to build conventional devices, in a process outlined in an Advanced Materials paper.

The new technique – developed by Professor David Jamieson and co-authors from UNSW Sydney, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Leibniz Institute of Surface Engineering (IOM), and RMIT – can create large scale patterns of counted atoms that are controlled so their quantum states can be manipulated, coupled and read-out.

Lead author of the paper, Professor Jamieson said his team’s vision was to use this technique to build a very, very large-scale quantum device.

“We believe we ultimately could make large-scale machines based on single-atom quantum bits by using our method and taking advantage of the manufacturing techniques that the semiconductor industry has perfected,” Professor Jamieson said.

The technique takes advantage of the precision of the atomic force microscope, which has a sharp cantilever that “touches” the surface of a chip with a positioning accuracy of just half a nanometre, about the same as the spacing between atoms in a silicon crystal.

The team drilled a tiny hole in this 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 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 plows into the silicon crystal and dissipates its energy by friction can be exploited to make a tiny electronic “click.”  READ MORE...