Gaps between equations and experiments in quantum cryptography

TL;DR

This paper examines the disconnect between theoretical models and actual experimental results in quantum cryptography, highlighting the role of guesswork and its implications for security and device modeling.

Contribution

It introduces a philosophical framework using Wittgenstein's language games to analyze the relationship between quantum models and experiments, revealing inherent gaps and the role of guesswork.

Findings

There is an inherent gap between quantum equations and experimental device behavior.

Models that match experimental results can still imply different security levels.

Recognizing guesswork can help improve security by informing feedback loop design.

Abstract

Proofs of the security of quantum key distribution are propositions about models written in the mathematical language of quantum mechanics, and the issue is the linking of such models to actual devices in an experiment on security. To explore this issue, we adapt Wittgenstein's method of language games to view quantum language in its application to experimental activity involving transmitting and receiving devices. We sketch concepts with which to think about models in relation to experiments, without assuming the experiments accord with any model included is a concept of one quantum-mechanical model enveloping another. For any model that agrees with given experimental results and implies the security of a key, there is an enveloping model that agrees with the same results while denying that security. As a result there is a gap between equations and the behavior recorded from devices in an experiment, a gap bridged only by resort to something beyond the reach of logic and measured data, well named by the word guesswork. While this recognition of guesswork encourages eavesdropping, a related recognition of guesswork in the design of feedback loops can help a transmitter and receiver to reduce their vulnerability to eavesdropping.