A group of physicists from the University of Arizona have developed a so-called Quantum Interference Effect Transistor (QuIET), a single molecule that functions through quantum mechanical effects as a working transistor. The discovery might have major implications for the future of nanomedicine:
The simplest molecule they propose for a transistor is benzene, a ring-like molecule. They propose attaching two electrical leads to the ring to create two alternate paths through which current can flow.
They also propose attaching a third lead opposite one of the electrical leads. Other researchers have succeeded in attaching two contacts to a molecule this small, but attaching the third is the trick — and the point. The third lead is what turns the device on and off, the “valve.”
“In classical physics, the two currents through each arm of the ring would just add,” Stafford said. “But quantum mechanically, the two electron waves interfere with each other destructively, so no current gets through. That’s the ‘off’ state of the transistor.”
The transistor is turned on by changing the phase of the waves so they don’t destructively interfere with each other, opening up addiitonal paths through the third lead.
“It took a while to go from the idea of how this could work to developing realistic calculations of this kind of system,” Stafford said. “We were able to do the simplest kind of quantum chemical calculations which neglect interactions between different electrons within a few weeks. But it took some time to put in all the electron interactions that demonstrate this really is a very robust device.”
According to the Semiconductor Research Corp. it typically takes a dozen years for a new idea to go from initial scientific publication to commercial technological application, Stafford noted.
“That means if the computer industry is to continue its recent pace in making smaller-scale computers, we should have had this idea yesterday, ” Cardamone said…
Nanocomputers could have a major impact in medicine, Cardamone said. “These machines could operate in solution, in vivo. There already are clinical trials of nanoparticles to deliver medicinal drugs. Imagine how much more powerful those little nanoparticles or nanorobots would be if they could count, or do simple computation. With our transistors packed at maximum density, you could put a microprocessor as powerful as the top-of-the-line workstation on the back of an E. coli.”
“Have you seen the movie, Fantastic Voyage?” Stafford asked.