CONCLUDING REMARKS AT THE BEGINNING OF A NEW COMPUTING ERA - Bio-Inspired and Nanoscale Integrated Computing - page 538

are challenging to determine, but understanding these bounds has implications on
the benefits of quantum computation versus classical computation. More infor-
mation about this author's research, including work on quantum computing, may
be found at the home page of Professor John H. Reif at Duke University, http://
www.cs.duke.edu/

reif/.
Chapter 4 described quantum-dot cellular automata (QCA), a paradigm that
uses ground-state computation instead of switching technology. In this paradigm,
QCA cells are used for both the logic function itself and interconnections between
functions. It first introduced the operation of a single QCA cell and discussed that
kink energy is an important parameter that makes the physical simulation of QCA
tractable. It then discussed several issues of designing QCA circuits, specifically,
the challenges of clocking and wire crossing. The chapter discussed the simulation
tool, QCADesigner. Throughout the chapter, implementations of simple Boolean
logic circuits, adders, multipliers, and even a simple processor, were shown with
QCA. Finally, how QCA devices can be implemented using quantum dots,
magnetic nanoparticles, or molecules was discussed. More information about
the authors' affiliations and research can be found at the Microsystems and
Nanotechnology Group at the University of British Columba, http://www.mina.
ubc.ca/, and ATIPS Labs, http://www.atips.ca/.
This topic then looked at how the dielectrophoretic effect can be exploited to
move nanoscale structures-Chapter 5, which discussed the use of dielectrophoresis
for assembly, reconfiguration, and disassembly of a nanoscale device. It also
described circuit-level architectures that could be used to create crossbars and
field-programmable gates. This effect is also envisioned to be used for fault
tolerance, where the functionality to replace faulty circuits using dielectrophoresis
could potentially be contained in a chip's packaging. More information about this
and the author's other research may be found at the home page of Dr. Alexander
D. Wissner-Gross, http://www.alexwg.org/index.html.
Data storage is also an important aspect of nanocomputing. Chapter 6
studied multilevel magnetic recording, a data storage technique that can attain
storage densities of more than 10 terabits/in 2 , and possibly up to 100 terabits/in 2 .
The chapter illustrated that the superparamagnetic limit is a fundamental
limitation to improving traditional magnetic storage density, even with recent
perpendicular recording techniques. It described how multilevel magnetic record-
ing would work, and compared it to existing multilevel optical recording
techniques. It also discussed how data would need to be encoded to use a
multilevel magnetic storage system. More information about the authors and
their research can be found at the Center for Nanomagnetic Systems at the
University of Houston, http://www.uh.edu/cns/, and the Center for 3D Electro-
nics at the University of California, Riverside, http://c3de.ee.ucr.edu/.
The use of spin-waves for nanoscale computation was presented in Chapter 7.
Chapter 7 first described how spin waves propagate. Then, it discussed three main
architectures that benefit from spin waves: reconfigurable mesh, crossbar, and
fully interconnected cluster. Because of wave properties, these three architectures
can transmit multiple signals simultaneously, perform concurrent writes, and

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