A University of Melbourne-led team has developed a method to make quantum computers cheaply and reliably. It embeds single atoms into silicon wafers. This mirrors the methods used to create conventional devices. The process is described in an Advanced Materials article.
Professor David Jamieson, Helmholtz-Zentrum Dresden-Rossendorf, UNSW Sydney, and Leibniz Institute of Surface Engineering, (IOM) are the co-authors of this new technique. It can create large-scale patterns of counted Atoms that can be controlled so their quantum state can be modified, coupled, and read out.
Professor Jamieson, the lead author of this paper, stated that his team had envisioned using this technique to create a large-scale quantum device.
Professor Jamieson stated, “we believe we could eventually make large-scale machines using single atom quantum bits by using this method and taking advantage of the manufacturing techniques the semiconductor industry has perfected.”
This technique uses the precision of an atomic force microscope. It has a sharp cantilever that “touches” the chip’s surface with a positioning accuracy of only half a nanometer. This is about the same spacing as between the silicon crystal atoms.
This cantilever was drilled with a small hole so that phosphorus atoms could be poured into it.
It was crucial to know exactly when an atom, and only one, had been embedded in the substrate. The cantilever could then move to the next position on the array.
Professor Jamieson explained that one atom colliding with a silicon piece produces a faint click. However, we have developed very sensitive electronics to detect this click.
This allows us to feel very confident in our method. It is possible to say, “Oh, there was click.” Just now, an atom arrived. Professor Jamieson stated, “Now we can move our cantilever to the next spot, and wait for another atom.”
Up until now, the process of implanting atoms into silicon was haphazard. A silicon chip is sprayed with phosphorus, which implants in a random pattern like raindrops on windows.
Scientia Professor Andrea Morello, University of New South Wales, was a co-author. The new technique embedded phosphorus ions in silicon substrates, counting each individually, creating a qubit chip. This can be used to perform lab experiments and test designs for large-scale devices.
We have already achieved ground-breaking results with our Centre partners on single atom qubits created using this technique. However, the discovery will accelerate work on large-scale devices.”
Quantum computers could have practical implications for optimizing timetables and finances, unbreakable encryption, computational drug design, and developing new vaccines.