Emergence of the Born rule in quantum optics*

The Born rule provides a fundamental connection between theory and observation in quantum mechanics, yet its origin remains a mystery. We consider this problem within the context of quantum optics using only classical physics and the assumption of a quantum electrodynamic vacuum that is real rather than virtual. The connection to observation is made via classical intensity threshold detectors that are used as a simple, deterministic model of single-photon detection. By following standard experimental conventions of data analysis on discrete detection events, it can be shown that this model is capable of reproducing several observed phenomena thought to be uniquely quantum in nature.