Design and simulation of reversible molecular mechanical logic gates and circuits

Thesis

In this thesis, I outline a framework for constructing molecular mechanical circuits from logic gates and components that I have designed and optimised, and describe the results of simulations conducted to determine the thermodynamic properties of these circuits with a coarse-grained rigid body simulator. The molecular mechanical logic gates I have designed can be used to construct logically reversible circuits, which have the potential to be far more efficient than their irreversible counterparts due to the fact that they can easily be operated in a thermodynamically reversible manner.

Using the rigid body simulator, I first demonstrate Landauer's principle, a fundamental principle of information theory which relates the change in information entropy of a given process to the work required to complete it, thus showing that my rigid body simulator is thermodynamically self-consistent. I then simulate a novel molecular mechanical NAND gate design and use it to construct complex logically and thermodynamically reversible combinatorial circuits, including a half-adder. Subsequently, I investigate the use of pipelining to increase the throughput of a circuit at the cost of potential logical irreversibility, and show that it is possible to perform pipelining efficiently under certain conditions. Finally, I use a genetic algorithm to optimise various circuit components, demonstrating a novel technique to reduce the number of costly simulations that must be run in order to calculate the fitness function.

Authors: Seet, I

• DOI: 10.5287/ora-o5rbkkork
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Subjects: Chemistry, Physical and theoretical