The Informatics of Heat, Time, and Causality

When a cryptographic scheme is devised and its security proven, one has to take into account all the adversarial possibilities including (possibly quantum-) computing power, side channels, etc. — ultimately every attack that is compatible with the laws of physics. This is one of the reasons for the intimate and as such inescapable connection between informatics and physics. In this broad context, the proposed research focuses on an “informatics” understanding and potential of the laws and phenomena of quantum theory, special and general relativity, and thermodynamics. As a central part of this consideration, we revisit the underlying physical theories from the point of view of information: When the latter is put to the center, as it turns out, it is possible to rid the views from certain historical contingencies, conceptual inconsistencies, and detours, and to concentrate on their fundamental essence — which in our view is often informatics, as it has been already recognized to some degree in quantum theory and thermodynamics. We aim at reworking these theories with the goal of getting out novel information-processing, e.g., cryptographic, possibilities. As an illustrative example, our informational view of the second law of thermodynamics has given rise, as we showed in the predecessor project, to achieving cryptographic functionalities like secret-key agreement and oblivious transfer, among others, from free-energy bounds only. In particular, the functionality of oblivious transfer is of great interest here since it is known impossible to be obtained from relativistic and quantum-physical phenomena.

Our project is subdivided into four interconnected parts with the following respective goals.

Sub-Project A. “Quantum Informatics.”

In this part, we plan to advance the understanding of quantum phenomena of interest in the context of information processing: Multi-partite nonlocal correlations (network nonlocality) on the one hand, and the Kochen/Specker theorem on the other, have not yet been understood adequately for fully grasping their informational possibilities. In turn, we want to determine the exact classical-communication (round-) complexity of quantum correlations.

Sub-Project B. “Physiocryptography.”

In this, cryptographic and as such most applied, part of the proposed project, we plan to focus on cryptographic primitives such as secrecy, authenticity, and secure cooperation, their provably secure realization in a quantum-computational setting, based on physical restrictions on computing power or more basic physical limitations such as speed of communication, available binary degrees of freedom or energy, among others.

Sub-Project C. “Thermoinformatics.”
Of great interest for the success of the entire project is an information-centered understanding and view of thermodynamics. Such a perspective can also be expected to be more general and unified, ridding the theory of certain historical contingencies. For instance, our view of temperature as energy per information — the work required for creating a binary degree of freedom — does not only render Boltzmann’s constant obsolete, but also recognizes temperature as a fundamental (as opposed to emergent) microscopic concept independent of traditional preconditions such as heat baths and thermal equilibria, and is thus independent of the debated zeroth law of thermodynamics. It is the longer-term goal of this part of our project to understand and reformulate the entire theory of thermodynamics in that spirit.

Sub-Project D. “Causalgorithmics.”

While, as just explained, we aim at considering temperature as fundamental, we have several motivations to believe the exact opposite for space and time: Motivated by, e.g., the “weirdness” of Bell correlations, we propose to start from the premise of viewing spacetime as based on informational concepts such as algoithmic (Kolmogorov) complexity. This program is in line with a number of approaches, e.g., due to Wheeler/De Witt and Page/Wootters, to see quantum theory as fundamentally timeless. We plan to pursue related considerations in particular with respect to space.