Entropy diagnostics for cryptographic key material from random circuit sampling

Random Circuit Sampling (RCS) has emerged as a leading paradigm for demonstrating quantum advantage. Beyond computational complexity, RCS provides a high-dimensional, chaotic probability distribution whose structure is characteristic of random unitary dynamics; here, we study its entropy properties in an ideal statevector baseline intended for later hardware validation. In this work, we present a reproducible validation framework for certifying cryptographic keys using a 12-qubit RCS ensemble (N = 4096 “ states” ) within an ideal quantum simulation framework. Unlike standard Quantum Random Number Generators (QRNGs), which often rely on single-qubit optics, our protocol utilises multiqubit entanglement to ensure nonlocality. We quantify the security of the system using a dual-metric approach: basis-dependent Min-Entropy (H∞ ≈ 9.05 “ bits” ) for cryptographic extractability, and basis-independent Subsystem Von Neumann Entropy (S ≈ 3.96 bits) for quantum certification. We further demonstrate a privacy-amplification pipeline that uses a frequency-preserving, endian-corrected SHA-3 extraction to produce a 256-bit secure key (candidate key material). This study provides a transparent methodological bridge between the theoretical “Quantum Supremacy” regime and practical cryptographic key generation.