The research team that last month announced creating a wire one atom tall and four atoms wide has also built a working transistor from a single atom. Physicists from the University of New South Wales and Purdue University took a single phosphorous-31 isotope and were able to precisely place individual phosphorous atoms in a base of silicon using a scanning tunneling microscope in an ultra-high vacuum chamber. Though single-atom transistors date to 2002, The New York Times explains the advances in this work on two fronts: the precision in placing the atom and the use of industry-standard techniques to build the circuitry, making it possible to read and write information from the tiny switch. The Times explains how this tiny circuitry could create smaller, faster circuitry based on quantum mechanics rather than the silicon variety in use today:
In contrast to conventional computers that are based on transistors with distinct “on” and “off” or “1” and “0” states, quantum computers are built from devices called qubits that exploit the quirky properties of quantum mechanics. Unlike a transistor, a qubit can represent a multiplicity of values simultaneously. That might make it possible to factor large numbers more quickly than with conventional machines, thereby undermining modern data-scrambling systems that are the basis of electronic commerce and data privacy. Quantum computers might also make it possible to simulate molecular structures with great speed, an advance that holds promise for designing new drugs and other materials.
There are significant hitches to be overcome. One that looms large, as Nanowerk points out, is that the transistor must be kept very cold – at least as cold as liquid nitrogen, or minus 391 degrees Fahrenheit (minus 196 Celsius). And Forbes' Alex Knapp points out that scanning tunneling microscopy is far too expensive at this point to be used in manufacturing. However, the work holds promise to be compatible with CMOS systems used in today’s computers, he says. With Moore's Law expected to reach its limit with existing technology in 2020, this concept may make that whole point moot. As Michelle Simmons, group leader and director of the ARC Centre for Quantum Computation and Communication at the University of New South Wales, put it:
This is a beautiful demonstration of controlling matter at the atomic scale to make a real device. Fifty years ago when the first transistor was developed, no one could have predicted the role that computers would play in our society today. As we transition to atomic-scale devices, we are now entering a new paradigm where quantum mechanics promises a similar technological disruption. It is the promise of this future technology that makes this present development so exciting.