Building a Completely Reversible Computer

TL;DR

This paper critically examines the feasibility of building a fully reversible computer, highlighting fundamental physical and practical challenges, including energy dissipation and thermodynamic constraints, that hinder realization.

Contribution

It provides a detailed analysis of the physical and theoretical limitations of reversible computing and offers bounds on energy dissipation for such systems.

Findings

Reversible computers require energy for input setup and output readout.

Transport of information between logic elements consumes energy.

Thermodynamic constraints impose fundamental limits on reversibility.

Abstract

A critical analysis of the feasibility of reversible computing is performed. The key question is: Is it possible to build a completely reversible computer? A closer look into the internal aspects of the reversible computing as well as the external constraints such as the second law of thermodynamics has demonstrated that several difficulties would have to be solved before reversible computer is being built. It is shown that a conventional reversible computer would require energy for setting up the reversible inputs from irreversible signals, for the reading out of the reversible outputs, for the transport of the information between logic elements and finally for the control signals that will require more energy dissipating into the environment. A loose bound on the minimum amount of energy required to be dissipated during the physical implementation of a reversible computer is obtained and a generalization of the principles for reversible computing is provided.