Quantum Computation as Redirected Universal Rendering: Planck Cells, Coherence Times, and the Physical Substrate of Quantum Speedup

We examine quantum computation from the perspective of Pixel Theory — a framework treating spacetime as a discrete network of Planck-volume cells in which the speed of light represents the causal propagation rate. Qubits in superposition are Planck cells held in genuinely uncommitted states; measurement forces causal commitment; entanglement is a correlated rendering task. The maximum gate speed is bounded by one Planck tick (~5.4×10⁻⁴⁴ s), giving a theoretical ceiling of ~10⁴³ ops/sec. Coherence times increase at ~5×10⁻¹¹ per year as the Planck time grows with decreasing c. We propose that quantum computers access both temporal branches of the universe, providing a speculative physical substrate for quantum speedup. The universe itself performs ~4×10¹⁶⁴ ops/sec. The Lloyd consistency check — reconciling energy-based (~10¹⁰⁵) and pixel-based (~10¹⁶⁴) computation rates — is the central open problem. This is Paper 6 in the Pixel Theory series.