Nanocomputers
Patrick Kennedy
John Maley
Sandeep Sekhon
History
 Since Feynam’s “There is Plenty of Room
at the Bottom”, nanotechnology has
become a hot topic.
 With computers being an integral part in
today’s society, nanocomputers are the
easiest and most likely route in which
computer development may continue.
Moore’s Law
 According to Moore’s Law, the number of
transistors that will fit on a silicon chip
doubles every eighteen months.
 Presently, microprocessors have more than
forty million transistors; by 2010 they could
have up to five billion.
 By the year 2020, the trend line of Moore’s
law states that there should be a one
nanometer feature size.
Transistors
 The transistor is the most important component
of a computer today.
 More transistors = larger computer memories and
more powerful computers
What is a nanocomputer?
 The general definition of a nanocomputer
is a computer which either uses nanoscale
elements in its design, or is of a total size
measured in nanometers.
Types of nanocomputers
 Electronic
 Mechanical
 Chemical
 Quantum
Electrical Nanocomputers
 Electronic nanocomputers would operate
in a manner similar to the way present-day
microcomputers work.
 Due to our fifty years of experience with
electronic computing devices, advances in
nanocomputing technology are likely to
come in this direction.
How it works
 Although electronic nanocomputers will not use
the traditional concept of transistors for its
components, they will still operate by storing
information in the positions of electrons.
 There are several methods of nanoelectronic
data storage currently being
researched. Among the most promising are
single electron transistors and quantum dots.
 All of these devices function based upon the
principles of quantum mechanics.
Transistor replacements
 Resonant Tunneling Transistor
 Single Electron Transistor
 Quantum Dot Cell
 Molecular Shuttle Switch
 Atom Relay
 Refined Molecular Relay
Single Electron Transistors
 The single electron transistor (SET) is a new
type of switching device that uses controlled
electron tunneling to amplify current
SET
 When the gate voltage is set to zero, very little tunneling
occurs.
 The charge transfer is continuous.
 This voltage controlled current behavior makes the SET
act like a field effect transistor, just on a smaller scale.
Resonant Tunneling Device
 RTD’s are constructed from semiconductors
hetero-structure made from pairs of different
alloys III-IV alloys.
Quantum Dots
 They are nanometer scaled “boxes” for
selectively holding or releasing electrons.
 The number of electrons can be changed
by adjusting electric fields in the area of
the dot.
 Dots range from 30nm to 1 micron in size
and hold anywhere from 0 to 100s of
electrons.
Quantum Dot Cell
 Logic gates can be created using dot cells.
Molecular Shuttle Switch
 The shuttle is a ring shaped molecule the encircles and
slides along a shaft-like chain molecule.
 The shaft also contains a biphenol and a benzidine
group which serve as natural stations between which the
shuttle moves.
Atom Relay
 It consists of a carefully patterned line of atoms
on a substrate.
 Consists of two atom wires connected by a
mobile switching atom.
Refined Molecular Relay
 Based on atom movement.
 Rotation of molecular group affects the electric
current.
Comparison
Mechanical Nanocomputers
 Mechanical nanocomputers would use tiny
moving components called nanogears to
encode information.
 Other than being scaled down in size
greatly, the mechanical nanocomputer
would operate similar to the mechanical
calculators used during the 1940s to
1970s.
Mechanical Nanocomputers
 Eric Drexler and Ralph Merkle are the
leading nanotech pioneers involved with
mechanical nanocomputers.
 They believe that through a process
known as mechanosynthesis, or
mechanical positioning, that these tiny
machines would be able to be assembled.
How it works
 In today’s conventional microelectronics,
voltages of conducting paths represent digital
signals, and logic gates used as transistors.
 For the mechanical nanocomputer, the displacement
of solid rods would represent the digital signal.
 Rod logic would enable, “the implementation of
registers, RAM, programmable logic arrays, mass
storage systems and finite state machines
Nanosystems
 Drexler declared that the nanocomputer could
contain about, 106 transistor like interlocks
within a 400nm cube, have clock speeds of
about 1 GHz with an execution time of about
1000 MIPS; all with only about 60nW of power
consumption.
 Ralph Merkle stated that, “In the future we'll
pack more computing power into a sugar cube
than the sum total of all the computer power that
exists in the world today.”
Problems!
 Slow process that would be required to
assemble the computers.
 Hand made parts would have to be
assembled one atom at a time by an STM
microscope.
 Due to this slow and tedious process,
researchers also believe that reliability of the
parts would suffer.
Quantum Nanocomputer
 The basis for the idea of a quantum
nanocomputer came from the work of Paul
Benioff and Richard Feynam during the
1980s.
How it works
 The quantum nanocomputers are planned
to hold each bit of data as a quantum state
of the computer
 By means of quantum mechanics, waves
would store the state of each nanoscale
component.
 Information would be stored as the spin
orientation or state of an atom.
How it works
 With the correct setup, constructive
interference would emphasize the wave
patterns that held the right answer, while
destructive interference would prevent any
wrong answers.
Problems with Quantum computers
 The main problem with this technology is
instability. Instantaneous electron energy
states are difficult to predict and even
more difficult to control.
 An electron can easily fall to a lower energy
state, emitting a photon
 A photon striking an atom can cause one of its
electrons to jump to a higher energy state.
Chemical Nanocomputers
 Also known as biochemical nanocomputers,
they would store and process information in
terms of chemical structures and interactions.
 The development of a chemical nanocomputer will
likely proceed along lines similar to genetic
engineering.
 Engineers must figure out how to get individual atoms
and molecules to perform controllable calculations
and data storage tasks
Advances
 In 1994, Leonard Adelman took a giant
step towards a different kind of chemical
or artificial biochemical computer.
 He used fragments of DNA to compute
the solution to a complex graph theory
graph.
Adelman’s methods
 Adleman's method utilized sequences of DNA's
molecular subunits to represent vertices of a
network or "graph".
 Combinations of these sequences formed
randomly by the massively parallel action of
biochemical reactions in test tubes described
random paths through the graph.
 Adleman was able to extract the correct answer
to the graph theory problem out of the many
random paths represented by the product DNA
strands.
Problems
 These systems are largely uncontrollable
by humans.
 Limited problem domain, lacking efficient
input and output techniques.
Big problems
 Though each nanocomputer has its own
set of problems, each share some
common problems.
 A way must be found to manufacture
components on the scale of a single
molecule.
 How to actually constructing a nanoelectric
device.
The Interconnect Problem
 Perhaps the greatest problem is
something termed the "Interconnect
Problem."
 Basically, it's the question of how to
interface with the nanocomputer.
 With such a dense computational structure,
how does one get information in or out?
 There so many separate elements that there
would have to be a multitude of connections
within the computer itself.
Future of nanocomputers
 Nanotechnology has huge potential in building smaller
and smaller computers.
 Far greater amounts of information would be stored in
the same amount of space. This has enormous spacesaving implications.
 Someday, all the books in the world could fit into the
space of a square inch. Such efficient data storage has
great potential for business and scientific research in all
fields.
 Such microcomputers also have great potential for the
entertainment industry. With such great data storage
capacity, extremely elaborate computer games and
virtual reality environments could be created.
Resources
 1. http://www.mitre.org/tech/nanotech/futurenano.html
 2. http://whatis.techtarget.com/definition/0,,sid9_gci514014,00.html
 3.http://searcht.aimhome.netscape.com/aim/boomframe.jsp?query=mechan
ical+nanocomputers&page=2&offset=0&result_url=redir%3Fsrc%3Dwebsea
rch%26requestId%3D7eb7002b08196fa7%26clickedItemRank%3D18%26u
serQuery%3Dmechanical%2Bnanocomputers%26clickedItemURN%3Dhttp
%253A%252F%252Fwww.rootburn.com%252Fportfolio%252Fnano%252F
%26invocationType%3Dnext%26fromPage%3DAIMNextPrev%26amp%3B
ampTest%3D1&remove_url=http%3A%2F%2Fwww.rootburn.com%2Fportfo
lio%2Fnano%2F
 4. http://washingtontimes.com/upi-breaking/20050317-124226-2271r.htm
 5. A. Aviram, M. Ratner, “Molecular Rectifiers” Chem.phys letter Vol. 29.
pgs 277-283
Questions??