Implementable building blocks for fluctuation based calculation in single electron tunneling technology

Generally speaking, fluctuations and noise are unwanted factors interfering with the operation of devices and circuits, and their effect is becoming stronger as the fabrication technology feature size is decreasing. Recently, single electron tunneling (SET) circuit implementations were proposed for two building blocks that were designed for Brownian motion circuits, i.e., circuits which instead of trying to suppress fluctuations (noise) are taking advantage of it. These are the so-called Hub and Conservative Join. The Hub provides its output to other building blocks by repeatedly offering its state at its output terminals, and taking it back when it cannot be delivered. Based on a random scheme of signaling, the Hub requires fluctuations to drive its operation. The other building block, the Conservative Join, is designed to work in cooperation with the Hub, though it does not require fluctuations. Those two building blocks constitute a universal set thus any logic function can be implemented only with such blocks. However, the proposed implementations require topologies and circuit parameters that are not realizable for the state of the art fabrication technology. This paper presents single electron tunneling (SET) circuit implementations for the two building blocks which are taking into account realizability constraints. We propose novel SET circuit topologies for both blocks that satisfy topology and circuit parameters constraints and analyze their behavior at a temperature of 1K by computer simulations with SIMON 2.0. We demonstrate that the two different modes of operation in the blocks, fluctuation vs. non-fluctuating, can be accommodated by appropriately tuning circuit parameters. Utilizing these proposed topologies we then present an example of a half adder circuit constructed using the two building blocks and demonstrate that it functions correctly by means of simulations.