Group 2 – Nanocomputers
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Transcript Group 2 – Nanocomputers
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
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serQuery%3Dmechanical%2Bnanocomputers%26clickedItemURN%3Dhttp
%253A%252F%252Fwww.rootburn.com%252Fportfolio%252Fnano%252F
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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
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