When Does a Spin Flip? Arrival Time Distributions and Information Propagation in Discrete Quantum Systems

We analyze three distinct approaches to time of arrival (TOA) distributions for discrete quantum systems using a spin-12 particle in a constant magnetic field as a paradigmatic example. We argue that these distributions should not be regarded as competing predictions for the same notion of arrival time, but rather relate to fundamentally different notions whose relevance depends on the physical context. These results are used to analyze information propagation arrival time distributions in XX spin chain systems, and discuss potential applications in quantum information science.