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

2. 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

3. Clocked Molecular Quantum-dot Cellular Automata
The Moore’s Law

4. Clocked Molecular Quantum-dot Cellular Automata
It is necessary a new computational paradigm
Quantum-dot Cellular Automata

5. Clocked Molecular Quantum-dot Cellular Automata
What is it?

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

7. 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.

8. Clocked Molecular Quantum-dot Cellular Automata
These devices have some problems:
Too low working temperature (4°K)
A metastable configuration with long life time can be achieved ERROR IN COMPUTATION
High sensitiity to the position cell-to-cell (showing by simulation)

9. Clocked Molecular Quantum-dot Cellular Automata
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)

10. Clocked Molecular Quantum-dot Cellular Automata
Molecular quantum-dot proposed by
Lent – Isakcsen
Allyl
Alkyl

11. 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

12. 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
6.6Å

13. Clocked Molecular Quantum-dot Cellular Automata

14. 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

15. 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”

16. 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

17. 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 L1
in the second cell of this chain

18. 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

19. 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.

20. 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.