The Quantum Ledger Delusion — Post-Quantum Cryptographic Hype, Decentralized Ledger Incoherence, and the Thermodynamic Impossibility of Trustless Scale

As enterprise software vendors, venture capital syndicates, and sovereign regulatory bodies scramble to future-proof digital infrastructure against speculative quantum decryption threats, a compounding architectural delusion has taken root: the belief that distributed cryptographic ledgers can be seamlessly fused with quantum-resistant encryption and quantum-accelerated consensus algorithms to build infinitely scalable, trustless systems. This monograph analyzes "The Quantum Ledger Delusion": the systemic failure mode wherein the convergence of quantum computing marketing hype and decentralized ledger utopianism creates an impossible physical and computational hybrid. We examine the brutal physical realities of physical qubit decoherence (ℱ⁡(𝑡)=exp⁡(−𝑡/𝑇2)), the exponential scaling overhead of Quantum Error Correction (QEC), and the severe throughput degradation caused by post-quantum signature bloat. We construct a differential model of computational throughput decay(𝛹throughput→0) and establish non-negotiable defensive invariants (Classical-First Cryptographic Invariants, Strict Signature Size Ceilings, and the Separation of Consensus from Cryptographic Execution) to insulate critical state-transition infrastructure from thermodynamic incoherence.