AN INTRODUCTION TO NANOCOMPUTING - Bio-Inspired and Nanoscale Integrated Computing - page 3

nanoscale are used when considering devices that are at least one dimension
smaller than 100 nanometers (nm). Today, devices such as transistors have
channels that are well below 100 nanometers in length. Eventually the size of
entire computers may also be measured in nanometers.
Just how small is a nanometer? A nanometer is one-billionth of a meter
(10 9 m). Figure 1.1 shows the approximate size of various physical entities at the
nanometer scale. If it were possible to arrange 10 hydrogen atoms side by side,
their combined width would measure approximately 1 nanometer. A typical
processor found in a modern desktop computer is roughly 10 millimeters wide and
10 millimeters long—in terms of nanometers, this is nearly 10 million nanometers
in width and length! Other computers are commonly much smaller; embedded
processors used today in cell phones, cars, and many other devices are as small as
a fraction of a millimeter squared. Nanocomputers will be even smaller; electrons,
atoms, DNA, and proteins are all nanometer scale or smaller and offer a huge
variety of ways to represent and manipulate data.
At first this description may seem to be simply a matter of size. For more than
50 years, computers have continued to get smaller and faster, and so it may not be
obvious that nanocomputing is drastically different than microcomputing. Look-
ing deeper, however, the nanometer size opens a new world of possibilities.
Nanocomputers will be able to fit anywhere, even inside our own bodies. They
may be nearly undetectable, certainly invisible to the naked eye. Millions of such
computers could work together and intelligently collect data about the world.
Quantum physics makes it difficult to continue using old microcomputing
techniques, but it also gives us infinitely more possibilities.
With all this in mind, nanocomputing can be defined as the study of devices,
paradigms, and applications that surpass the domain of traditional microcomputers
by using physical phenomena and objects measuring 100 nm or less. This definition
clarifies that nanocomputing encompasses a large variety of challenges, ranging
from effectively fabricating nanoscale devices to creating revolutionary applica-
tions for nanocomputers.
In the nanoscale world, it is unlikely that computers will work the same way
they work today. Figure 1.2 lists some of the novel paradigms that can be realized
with nanoscale physics, roughly estimating how they may be compared to each
other given today's understanding of nanocomputing. As the figure shows, there is
a vast amount of untapped potential computational power beyond CMOS logic,
today's dominant technology.
Another important aspect of nanocomputing is the new set of applications
that will be possible with such tiny, powerful computers. In turn, the plethora of
applications raises ethical, social, and economic questions that are also of great
interest.
The applications and impact of nanocomputing will be discussed later in this
chapter, but let us first turn our attention to the fundamental question stated
above, that is, exploring how physics can be used for computation. Over the next
several sections we will discuss this idea, providing a historical context and generic
taxonomy of nanocomputing topics that are detailed in the rest of this topic.