Thermodynamic cost of reversible computing

Since reversible computing requires preservation of all information throughout the entire computational process, this implies that all errors that appear as a result of the interaction of the information-carrying system with uncontrolled degrees of freedom must be corrected. But this can only be done at the expense of an increase in the entropy of the environment corresponding to the dissipation, in the form of heat, of the ``noisy'' part of the system's energy. This paper gives an expression of that energy in terms of the effective noise temperature, and analyzes the relationship between the energy dissipation rate and the rate of computation. Finally, a generalized Clausius principle based on the concept of effective temperature is presented.Comment: 5 pages; added two paragraphs and fixed a number of typo

Using reversible computing to achieve fail-safety

This paper describes a fail-safe design approach that can be used to achieve a high level of fail-safety with conventional computing equipment which may contain design flaws. The method is based on the well-established concept of reversible computing. Conventional programs destroy information and hence cannot be reversed. However it is easy to define a virtual machine that preserves sufficient intermediate information to permit reversal. Any program implemented on this virtual machine is inherently reversible. The integrity of a calculation can therefore be checked by reversing back from the output values and checking for the equivalence of intermediate values and original input values. By using different machine instructions on the forward and reverse paths, errors in any single instruction execution can be revealed. Random corruptions in data values are also detected. An assessment of the performance of the reversible computer design for a simple reactor trip application indicates that it runs about ten times slower than a conventional software implementation and requires about 20 kilobytes of additional storage. The trials also show a fail-safe bias of better than 99.998% for random data corruptions, and it is argued that failures due to systematic flaws could achieve similar levels of fail-safe bias. Potential extensions and applications of the technique are discussed

Reversible Logic Elements with Memory and Their Universality

Reversible computing is a paradigm of computation that reflects physical reversibility, one of the fundamental microscopic laws of Nature. In this survey, we discuss topics on reversible logic elements with memory (RLEM), which can be used to build reversible computing systems, and their universality. An RLEM is called universal, if any reversible sequential machine (RSM) can be realized as a circuit composed only of it. Since a finite-state control and a tape cell of a reversible Turing machine (RTM) are formalized as RSMs, any RTM can be constructed from a universal RLEM. Here, we investigate 2-state RLEMs, and show that infinitely many kinds of non-degenerate RLEMs are all universal besides only four exceptions. Non-universality of these exceptional RLEMs is also argued.Comment: In Proceedings MCU 2013, arXiv:1309.104