The Physics of Computation: Fundamental Limits and the Honest Boundaries of Post-Classical Computing

Phase III of the Qubit Delusion series. Examines fundamental physical limits on computation: Landauer bound, Margolus-Levitin theorem, Bremermann limit, Bekenstein bound. Shows that quantum error-correction overhead (1e2-1e3 physical operations per logical operation) multiplies thermodynamic cost beyond what any polynomial algorithmic speedup can overcome. Proposes a falsifiable criterion: joules per solution on commercially relevant problems. Assesses all major quantum platforms against this criterion. Identifies reversible computing as the only paradigm that can approach the true physical limits.