In July, I wrote a post on the basics of quantum computation and the current state of the art. This field offers the promise of drastic improvements over our current computers, particularly in the ways they can factor large numbers. (That sounds dull, but it’s critical to modern cryptography, among other things.) Though quantum computers are not yet close to being cost-effective, their future is rapidly evolving from science fiction to science fact.
The development of real-world quantum computers relies on overcoming two challenges. The first is scientific: given the limitations of physics, is quantum computation possible? Physicists are currently hard at work pondering what sorts of calculations can be done with this powerful technique.
The second challenge is from the engineering standpoint; true quantum computers require atom-level precision and accuracy in the creation of the qubits. While current transistors in silicon-based chips are just reaching 22 nm in size, atoms themselves are a hundred times smaller. Truly controlling the positions of individual atoms on a surface might have, at one time, seemed an enormous hurdle to manufacturing quantum computers.
Recently, however, scientists at the University of New South Wales announced just that feat. On the surface of a silicon crystal, they placed a single phosphorus atom between two nanometer-scale electrodes, effectively creating a single-atom transistor. This work, which showcased the remarkable power of scanning tunneling microscopy, was published recently in Nature Nanotechnology.
Though similar devices have been produced in the past, the previous approach tended to be much more scattershot, and consisted of etching the electrodes, then implanting or isolating the atom later via a method that was much less precise. The capacity to place atoms correctly in any geometry, on the first try, makes the goal of designing complicated atomic-level systems much more feasible. From the perspectives of both science and engineering, we’re getting closer every day to the future of quantum computation.
Fuechsle M, Miwa JA, Mahapatra S, Ryu H, Lee S, Warschkow O, Hollenberg LC, Klimeck G, & Simmons MY (2012). A single-atom transistor. Nature nanotechnology, 7 (4), 242-6 PMID: 22343383