1. Terminology here is fluid: except when quoting or paraphrasing others, this entry uses “quantum theory” to label a genus of which quantum field theories as well as non-relativistic quantum mechanics are species.

2. SIC abbreviates Symmetric, Informationally Complete positive operator-valued measure (POVM): see Renes, Blume-Cohout, Scott, and Caves 2004.

3. With a time-like world-line, an agent has no experience of space-like separated events.

4. They have been shown to exist at least in spaces of dimension \(d=2-53\); with high numerical precision for \(d=2-193\); and also for many other values of \(d\) (Grassl, 2021, Other Internet Resources, slide 40).

5. Interview of Niels Bohr by Thomas S. Kuhn, Leon Rosenfeld, Aage Petersen, and Erik Rudinger on 1962 November 17, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA: see the link in the Other Internet Resources.