Two Types Of Mechanical Reversible Logic

Molecular mechanical logic devices have been proposed as a method of eventually achieving very small size (device volumes of a few cubic nanometers) and thus of achieving very high packing densities. However, the heat generated by mole quantities of molecular mechanical logic devices packed into a small volume can be a major problem. Previous mechanical logic devices (in which the logic gates in a digital system are implemented using mechanical components) required that some part slide or rotate past another part, resulting in friction and heat generation when the parts move. This is not an inherent requirement in the operation of mechanical logic. This paper describes two types of mechanical reversible logic which eliminate sliding contact. In the first type contact between parts, when it does occur, involves only pressure. In the second, all contact between parts is eliminated. The entire computation could in principle be performed by a single block of complexly shaped oscillating elastic material. The state of the computation is stored in the elastic deformations of this single block. If the material is perfectly elastic, the resulting computer will dissipate no energy. Real material moving sufficiently slowly can approximate a perfectly elastic material as closely as desired. In real materials, energy dissipation occurs during successive cycles of compression and decompression of the material much as energy dissipation occurs when a gas is compressed by a piston. However, at sufficiently low temperatures, this mechanism of energy dissipation might no longer be operative. It is not impossible that energy