It's become accepted wisdom that Moore's Law -- the pace at which transistor density increases (or, roughly, the pace at which computers keep getting faster) -- will run into a fabrication wall fairly soon. Etching chips already requires the use of high-energy lithographic techniques, and quantum effects at the smaller and smaller distance between components is becoming harder to deal with. For some pundits, this means the end of the steady growth of computer improvements. They're right, but not in the way they expect. The imminent demise of silicon transistors has led researchers down new pathways with far greater potential than mere doubling every 18 months.
Last week's Journal of Applied Physics contained an article by physicists from HP's Quantum Science Research center entitled "The crossbar latch: Logic value storage, restoration, and inversion in crossbar circuits." The article describes the development of nanoscale circuits which perform the core logical functions of transistors -- AND, OR, and NOT.
The experimentally demonstrated latch consists of a single wire acting as a signal line, crossed by two control lines with an electrically switchable molecular-scale junction where they intersect. By applying a sequence of voltage impulses to the control lines and using switches oriented in opposite polarities, the latch can perform the NOT operation, which, along with AND and OR, is one of three basic operations that make up the primary logic of a circuit and are essential for general computing. In addition, it can restore a logic level in a circuit to its ideal voltage value, which allows a designer to chain many simple gates together to perform computations.
The BBC report on the research gives a good explanation of how it works, and the usual disclaimers apply -- still years away, may not work in the way initially thought, etc. Still, expect to see more of these kinds of announcements over rest of the decade. The "end of silicon" threat was recognized awhile back, and most of the big IT research groups -- Intel, IBM, Motorola, along with HP -- started their post-silicon teams long ago. That research should soon be bearing fruit. Most of it will almost certainly involve nanotechnology, but be prepared for interesting results with polymers and even biotechnology.
