Computers need energy to operate: Have you ever noticed that when rendering graphics or performing other computationally expensive tasks, your laptop heats up and drains its battery? Even though technological improvements have greatly increased the energy efficiency of computer components over the years while making them ever faster, heat dissipation remains one of the major limiting factors to increasing our computing power. One can ask whether it is possible, in principle, to bring this energy expenditure all the way down to zero.

Faist thermodynamicsIn a new article featured in Physical Review X, Philippe Faist and collaborator Renato Renner from ETH Zurich show that a fundamental limit ultimately hinders this progress: There is a minimal energy requirement which applies not only to information processing on any type of hardware, but also to any other processes that occur in nature, such as the replication of DNA or even microscopic processes that can only be described quantum mechanically. This new limit can be viewed as an extended formulation of thermodynamics, expanding the usual theory of thermodynamics originally developed for large systems such as steam engines.

Remarkably, this formulation of thermodynamics features the observer with a key role: The new fundamental limit depends explicitly on the observer’s knowledge, and can be determined for observers at any level of coarse-graining. The fact that the new formulation of thermodynamics is inherently observer-dependent demonstrates the subjective nature of thermodynamics.

Read the full article: Philippe Faist and Renato Renner, Fundamental Work Cost of Quantum Processes, Physical Review X 8, 021011 (2018).