User login

Molecular Quantum Cellular Automata

Abstract

Molecular Quantum Cellular Automata (QCA), is an exploratory computing paradigm in which information is encoded in the electronic charge configuration of a QCA cell (built from one or two individual molecules). The charge interaction between neighbouring cells enables the transmission and processing of information. Our research focus is on the design and simulation of QCA using numerical tools such as the QCADesigner tool developed in our lab.
QCA processor designed using QCADesigner

Project Description

The seemingly endless progress of microelectronics has been a result of the semiconductor industry's ability to continuously scale down the transistor, which is the fundamental computing component of the modern computer. Scaling of the transistor to low-nanometer scales is limited by effects such as gate leakage, drain induced barrier lowering, and the extreme power dissipation.

Molecular quantum cellular automata (QCA) is an exploratory computing paradigm in which information is encoded in the electronic charge configuration of a QCA cell. The charge interaction between neighbouring cells enables the transmission and processing of information. The underlying building block of any QCA circuit is the QCA cell, which is constructed with either a single molecule or a set of coupled quantum dots (in quantum-dot cellular automata (QCA)) or metallic islands (in metallic-island QCA).

MiNa members have developed a QCA design and simulation tool called QCADesigner. This tool is being used to evaluate this emerging technology by looking a circuits and computer architectures that can be implemented with QCA. For more information about QCADesigner, go to www.qcadesigner.ca.

Clocking Design for Molecular Quantum-Dot Cellular Automata

QCA circuits require an external clock, which can be generated using a network of submerged electrodes, to synchronize information flow and provide the required power to drive the computation. An example of the clocking network is shown below.


In our research, the effect of electrode separation and applied potential on the likelihood of different QCA cell states of molecular cells located above and in between adjacent electrodes is analysed. Using this analysis, estimates of operational ranges are developed for the placement, applied potential, and relative phase between adjacent clocking electrodes to ensure that only those states that are used in the computation, are energetically favourable.

Simulation of Molecular Quantum-Dot Cellular Automata Circuits (QCADesigner)

QCADesigner has been applied towards the high-level design and exploration of both sequential and combinational circuits. In QCADesigner, an N-cell system is decoupled into a set of N single-cell subsystems that are assumed to interact classically through expectation values without any quantum mechanical coherence between neighboring cells. Using this approximation, it is only necessary to diagonalize N 2x2 Hamiltonians as opposed to one 2^N x 2^N Hamiltonian. While this assumption makes it possible to solve large systems which would otherwise be computationally intractable, it can also result in the incorrect ground state wavefunction. By including the various quantum degrees of freedom such as quantum correlations, the coupling energy between cells can be better approximated and allow the system to converge at the correct ground state wavefunction. However, solving for all possible intercellular correlations can be prohibitive. In our research, we are developing a numerical method for solving large systems of cells that provides both accuracy and maintains a high level of computational efficiency.

For more information on Molecular QCA, visit:

1) http://www.qcadesigner.ca
2) http://www.nd.edu/~qcahome/javademo.html
3) http://virlab.virginia.edu/VL/QCA_cells.htm

Faculty Supervisor(s)

    Konrad.Walus   

Researchers(s)

    Faizal.Karim    Nick.Geraedts   

Research Area(s)

    Electronics