Actualization as Physical Mechanism: Implications of Relational Actualism for Quantum Computing and Quantum Thermodynamics

Relational Actualism (RA) proposes that the transition from quantum potentia to
classical actuality is grounded in a precise physical criterion: an irreversible
increase in quantum relative entropy Δ S(ρ\|σ₀) > 0 with respect
to the vacuum. In the perturbative regime this coincides with the on-shell
condition p^μ p_μ = m²c², at which a mediating boson crosses the
kinematic threshold from virtual to real and an irreversible vertex is inscribed
into the growing causal DAG. This paper develops the implications for quantum
computing and quantum thermodynamics.

For quantum computing, the Kinematic Snap provides a principled physical floor
on decoherence and yields the *Kinematic Coherence Bound*: the maximum
fault-tolerant array size is N\ₘax = η · pₜh,
where η is the single-qubit quality factor and pₜh is the
fault-tolerance threshold. This is a structural constraint not anticipated by
standard quantum error correction theory: logical error rates grow with N
because each added qubit is an additional kinematic site at which actualization
can occur.

For quantum thermodynamics, RA grounds Landauer's principle in the causal DAG
structure, resolves Maxwell's demon without information-theoretic postulates,
gives the fluctuation theorems a precise actualization-event interpretation, and
establishes that the thermodynamic arrow of time is structural rather than emergent.

A key technical result: the quantum relative entropy is frame-independent by a
machine-verified Lean 4 theorem (`frame\_independence` in
`RA\_AQFT\_Proofs\_v10.lean`), proved using the continuous functional
calculus unitary-conjugation lemma of the Lean-QuantumInfo library. The
fault-tolerance threshold, the speed of light c = lP/tP, and the biological
Causal Firewall are all the same Erdős-Rényi percolation transition
at different scales of the causal graph.