AAWSAP DIRD, Quantum Computing and Utilizing Organic Molecules in Automation Technology, December 2010

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pitch.d By comparison, atomic diameters range from around 0.1 nm to 0.5 nm, with silicon
~0.2 nm, or only a factor of 100 smaller.
As circuit elements decrease in size, the number of atoms making up the bulk materials
decreases and ignoring individual quantum effects becomes problematic. This is the
mesoscopic scale. At this size, quantum effects can introduce noise into the circuit as the
unpredictablee nature of the underlying wave functions. Once the circuit size shrinks to only a
few atoms, quantum effects will emerge from the noise domain to dominate the electrical
behavior. It is thought that exploiting rather than avoiding quantum phenomena may prove
useful in this regime for inorganic technologies.
Following Moore's law, in less than 10 years inorganic circuit elements will be less than 5x5
molecules in 2-D extent. (Molecular machines built of organic components, primarily DNA,
are discussed in a later section.) Shrinking traditional silicon-based general-processing
technology to this microscopic scale is one motivation for developing new types of machines
based on quantum phenomena, but it is not the only one. Smaller circuit elements decreased
the settling time of transistors and thus gates on CPUs, allowing increasing clock speed (the
CPU can execute the next instruction with shorter delay from the last instruction). CPUs
today get most of their performance with parallel architecture, executing several instructions
at once in different pipelines. Using smaller circuitry in general consumes less power, and
this allows more parallel elements to be packed into a reasonable wattage package. The
march toward smaller circuitry is continuing unabated so planning for the eventual quantum­
dominant characteristics is essential.
It is common to use the analogy of the laser to elucidate the application developments
possible with quantum computing. In one sense, the laser is just another hardware
technology that makes light. Earlier light technologies include organic-fueled fire (~50,000
BC), incandescent bulbs (early 19th c.), and fluorescent chambers (mid-19th c.). The light
source to utilize is not governed by the highness of the technology, but by requirements of
the application. One can read by laser light, but older and cheaper incandescent light will
provide superior perceptible illumination to a page. Traditional semiconductor-based
computing is cheap and plenty powerful for controlling navigation or driving ship status
displays.
The laser analogy is further revealing in that it is quantum effects producing a special kind of
light that is coherent. Coherent light is single wavelength with all photons travelling in the
same direction .f This coherence is a natural consequence of conservation of momentum in
the absorption/emission process. (4) Coherent light is very useful for some applications that
require low dispersion; for example, bouncing a beam off of a mirror on the moon, or the
more pedestrian pinpoint highlight of a projected PowerPoint presentation.
The practical uses of the laser are not universally bigger or smaller, faster or slower, or more
or less energy efficient than the other hardware technologies that produce light, they are just
different. Similarly, when we think of what hardware and applications will arise for quantum
computing, they too are not necessarily bigger, smaller, or faster than traditional methods;
they are just different, and many could not be accomplished with traditional technologies. (5)
d Pitch is the distance between repeat circuit elements. What is most interesting about the 22 nm technology is that it was
produced with 192 nm lithography.
• At the mesoscopic scale, individual wave functions are not prepared a priori or controlled in their propagation. Some of
the noise components are correlated.
'Laser light is actually very narrow bandwidth rather than single-valued.
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