Clocked Molecular Quantum-dot Cellular Automata

Clocked Molecular Clocked Molecular Quantum-dot Cellular Quantum-dot Cellular

AutomataAutomata

A NEW COMPUTATIONAL A NEW COMPUTATIONAL PARADIGMPARADIGM

Gabriele Dura

ClockedClocked Molecular Quantum-dot Molecular Quantum-dot Cellular AutomataCellular Automata

Recent computation is achieved thanks to Recent computation is achieved thanks to the enormous number of C-MOS per areathe enormous number of C-MOS per area

Now there is a problem to continue this Now there is a problem to continue this trendtrend

Clocked Molecular Quantum-dot Clocked Molecular Quantum-dot Cellular AutomataCellular Automata

The Moore’s Law The Moore’s Law


It is necessary a new computational It is necessary a new computational paradigmparadigm

Quantum-dot Cellular AutomataQuantum-dot Cellular Automata


What is it?What is it?


How to use it?How to use it?We can make quantum wireWe can make quantum wire

Quantum inverterQuantum inverter

Quantum Majority GateQuantum Majority Gate

Quantum fanoutQuantum fanout


How does it work?How does it work?

Every cell has two extra charge, that could Every cell has two extra charge, that could be electrons or holes.be electrons or holes.

Coulombic interaction between this extra Coulombic interaction between this extra charge will achieve a ground state in the charge will achieve a ground state in the cell, moving in the cell by tunnelingcell, moving in the cell by tunneling

The two extra charges are confined in the The two extra charges are confined in the cells by a high potential barrier.cells by a high potential barrier.


These devices have some problems:These devices have some problems:

1.1. Too low working temperature (4°K)Too low working temperature (4°K)

2.2. A metastable configuration A metastable configuration with long life timewith long life time can can be achievedbe achieved ERROR IN COMPUTATIONERROR IN COMPUTATION

3.3. High sensitiity to the position cell-to-cell (showing by High sensitiity to the position cell-to-cell (showing by simulation)simulation)

How to solve this problem:How to solve this problem:

Temperature Temperature Molecular Quantum-dot Molecular Quantum-dot cellscells

Metastable configurationMetastable configuration four phase four phase clock and quasi-adiabatic transitionclock and quasi-adiabatic transition

ImperfectionsImperfections actually there is no actually there is no indication about (only simulation)indication about (only simulation)



Molecular quantum-dot proposed byMolecular quantum-dot proposed by

Lent – IsakcsenLent – Isakcsen

AllylAllyl

AlkylAlkyl


Allyl groups serve Allyl groups serve as dots with his red-as dots with his red-ox centre that can ox centre that can be achieved cy hallsbe achieved cy halls

Alkyl groups serve Alkyl groups serve as tunnel barrier that as tunnel barrier that halls can pass halls can pass throughthrough


Molecule was driven by a Molecule was driven by a

driver dipoledriver dipole

andand

clocked by a perpendicular electric clocked by a perpendicular electric fieldfield

This give a highly nonlinear dipole This give a highly nonlinear dipole

moment moment

6.6Å


Molecular Quantum-dot CellMolecular Quantum-dot Cell


It is possible to enable the It is possible to enable the clock in this device using clock in this device using some buried wiressome buried wires

The current flow through The current flow through wires generates an Electric wires generates an Electric Field that drives the state of Field that drives the state of the moleculethe molecule


Clock must have four-phase that allows Clock must have four-phase that allows quasi-adiabatic interaction cell-to-cellquasi-adiabatic interaction cell-to-cell

Applied Signal Value of Electric Field Electric Field DistributionApplied Signal Value of Electric Field Electric Field Distribution

That implies this “truth table”That implies this “truth table”


Influence of imperfection on the dynamical response in QCAInfluence of imperfection on the dynamical response in QCANowadays only considered in model simulations.Nowadays only considered in model simulations.

Ideal chain of cells:Ideal chain of cells:

Imperfection introduced betweenImperfection introduced betweenthe fifth and the sixththe fifth and the sixth the third and the fourth the driver and the chain the third and the fourth the driver and the chain

Correct polarizationCorrect polarization Acceptable polarization Acceptable polarization Capability whole Capability whole disappearsdisappears


Imperfection due to interdot distance defectsImperfection due to interdot distance defects

Imperfection introduced in the interdot barriers in the second cellsImperfection introduced in the interdot barriers in the second cells

Dependence of the output Dependence of the output cell Response of polarization with this imperfectioncell Response of polarization with this imperfection on the tunneling parameter on the tunneling parameter LL11

in the second cell of this chainin the second cell of this chain


Imperfection due to interdot distance defectsImperfection due to interdot distance defectsImperfection introduced in the interdot barriers in the middle cell Imperfection introduced in the interdot barriers in the middle cell

Imperfection introduced in the interdot barriers in the last cellImperfection introduced in the interdot barriers in the last cell


Conclusion:Conclusion:

We can see that Molecular Quantum-dot We can see that Molecular Quantum-dot Cellular Automata produce a highly non-Cellular Automata produce a highly non-linear characteristic that can be used to linear characteristic that can be used to get something like logic gates with a very get something like logic gates with a very low power dissipation and very high device low power dissipation and very high device densities.densities.


Conclusion:Conclusion:

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

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Clocked Molecular Quantum-dot Cellular Automata