Clocked Molecular
Quantum

dot Cellular
Automata
A NEW COMPUTATIONAL
PARADIGM
Gabriele Dura
Clocked
Molecular Quantum

dot
Cellular Automata
Recent computation is achieved thanks to
the enormous number of C

MOS per area
Now there is a problem to continue this
trend
Clocked Molecular Quantum

dot
Cellular Automata
The Moore’s Law
Clocked Molecular Quantum

dot
Cellular Automata
It is necessary a new computational
paradigm
Quantum

dot Cellular Automata
Clocked Molecular Quantum

dot
Cellular Automata
What is it?
Clocked Molecular Quantum

dot
Cellular Automata
How to use it?
We can make quantum wire
Quantum inverter
Quantum Majority Gate
Quantum fanout
Clocked Molecular Quantum

dot
Cellular Automata
How does it work?
Every cell has two extra charge, that could
be electrons or holes.
Coulombic interaction between this extra
charge will achieve a ground state in the
cell, moving in the cell by tunneling
The two extra charges are confined in the
cells by a high potential barrier.
Clocked Molecular Quantum

dot
Cellular Automata
These devices have some problems:
1.
Too low working temperature (4
°
K)
2.
A metastable configuration
with long life time
can
be achieved
ERROR IN COMPUTATION
3.
High sensitiity to the position cell

to

cell (showing by
simulation)
How to solve this problem:
Temperature
Molecular Quantum

dot
cells
Metastable configuration
four phase
clock and quasi

adiabatic transition
Imperfections
actually there is no
indication about (only simulation)
Clocked Molecular Quantum

dot
Cellular Automata
Clocked Molecular Quantum

dot
Cellular Automata
Molecular quantum

dot proposed by
Lent
–
Isakcsen
Allyl
Alkyl
Clocked Molecular Quantum

dot
Cellular Automata
Allyl groups serve
as dots with his red

ox centre that can
be achieved cy halls
Alkyl groups serve
as tunnel barrier that
halls can pass
through
Clocked Molecular Quantum

dot
Cellular Automata
Molecule was driven by a
driver dipole
and
clocked by a perpendicular electric field
This give a highly nonlinear dipole
moment
6.6
Å
Clocked Molecular Quantum

dot
Cellular Automata
Molecular Quantum

dot Cell
Clocked Molecular Quantum

dot
Cellular Automata
It is possible to enable the
clock in this device using
some buried wires
The current flow through
wires generates an Electric
Field that drives the state of
the molecule
Clocked Molecular Quantum

dot
Cellular Automata
Clock must have four

phase that allows
quasi

adiabatic interaction cell

to

cell
Applied Signal Value of Electric Field Electric Field Distribution
That implies this “truth table”
Clocked Molecular Quantum

dot
Cellular Automata
Influence of imperfection on the dynamical response in QCA
Nowadays only considered in model simulations.
Ideal chain of cells:
Imperfection introduced between
the fifth and the sixth
the third and the fourth the driver and the chain
Correct polarization
Acceptable polarization
Capability whole disappears
Clocked Molecular Quantum

dot
Cellular Automata
Imperfection due to interdot distance defects
Imperfection introduced in the interdot barriers in the second cells
Dependence of the output cell
Response of polarization with this imperfection
on the tunneling parameter L
1
in the second cell of this chain
Clocked Molecular Quantum

dot
Cellular Automata
Imperfection due to interdot distance defects
Imperfection introduced in the interdot barriers in the middle cell
Imperfection introduced in the interdot barriers in the last cell
Clocked Molecular Quantum

dot
Cellular Automata
Conclusion:
We can see that Molecular Quantum

dot
Cellular Automata produce a highly non

linear characteristic that can be used to
get something like logic gates with a very
low power dissipation and very high device
densities.
Clocked Molecular Quantum

dot
Cellular Automata
L
Conclusion:
There is too much work to do to design a
good real device that can operate at room
temperature and can resist to the
imperfections occurring in the industrial
process for large scale diffusion
.
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