A team of researchers has developed a new silicon construction technique that could potentially improve the affordability and reliability of building quantum computers.
This new technique, jointly developed by researchers from the University of Melbourne, the University of New South Wales and the Royal Melbourne Institute of Technology in Australia, as well as the Helmholtz-Zentrum Dresden-Rossendorf and the Leibniz Institute for Surface Engineering in Germany, is to precisely integrate single atoms, one by one, into silicon wafers.
According to the researchers, the technique, which was published in an “Advanced Materials” paper, takes advantage of the precision of the atomic microscope, which has a pointed cantilever that “touches” the surface of a chip with a positioning accuracy of only half a nanometer, which is roughly the space between atoms in a silicon crystal. The researchers describe how a tiny hole was punched in the cantilever so that when it is sprayed with phosphorus atoms, one of them sometimes falls through the hole and becomes embedded in the substrate of silicon.
A critical aspect is knowing precisely when an atom is sinking into the substrate, so that the cantilever can move to the next precise position on the lattice.
Image: University of Melbourne
A qubit chip for testing large-scale devices
The article notes that until now, implanting atoms into silicon has been a random process. Indeed, when a silicon chip was sprinkled with phosphorus, an atom fell randomly, like raindrops on a window. However, the team found they could identify the accuracy through an audible “click” that occurs when an atom falls into the silicon crystal.
“An atom colliding with a piece of silicon produces a very weak click, but we have invented very sensitive electronics used to detect the click: it is very amplified and gives a strong and reliable signal”, explains David Jamieson, professor at the University of Melbourne and lead author. “This allows us to be very confident in our method. We can say, “oh, there was a click. An atom just arrived. Now we can move the cantilever to the next place and wait for the next atom.” »
To develop this technique, the researchers used equipment including sensitive X-ray detectors, an atomic force microscope originally developed for the Rosetta space mission, and a computer model of the trajectory of ions implanted in silicon.
Andrea Morello, one of the co-authors, adds that using this precision and this new technique, it would be possible to create a qubit “chip”, which could then be used in experiments to test large-scale device designs. . “This will allow us to design the quantum logic operations between large arrays of individual atoms, maintaining very precise operations throughout the processor,” he says. “Instead of implanting many atoms in random places and picking out the ones that work best, they will now be placed in an ordered array, similar to transistors in conventional solid-state computer chips. »
David Jamieson further cites tamper-proof cryptography and computational drug design, such as rapid vaccine development, among large-scale quantum devices that could be developed using this concept. “We believe that ultimately we could fabricate large-scale machines based on single-atom quantum bits using our method and taking advantage of fabrication techniques that the semiconductor industry has perfected” , he explains.
Source: ZDNet.com