Quantum Regime-First Laboratory Bench Book An Outcome-Agnostic Experimental Framework for Coherence, Noise, and Decoherence in Qubits and Quantum Systems

. Purpose and Scope This document defines a regime-first, outcome-agnostic experimental framework for the systematic study of coherence, noise, and decoherence in qubits and quantum systems. It is intended for use as a laboratory bench book, providing diagnostic protocols, classification rules, decision heuristics, and logging templates that enable rigorous, reproducible investigation of quantum system behaviour. 1.1 Applicability The framework is applicable to, but not limited to, the following quantum platforms: Superconducting qubits (transmon, fluxonium, and related architectures) Trapped ion systems Spin qubits (semiconductor quantum dots, NV centres, donor spins) Photonic and linear-optical quantum systems Other coherent quantum platforms exhibiting regime-dependent behaviour 1.2 Historical Motivation Quantum experimental science faces persistent methodological problems that are often treated as performance issues rather than as regime identification failures. Decoherence times drift between calibration cycles without explanation. Noise spectra change character in ways that are attributed to hardware degradation when they may instead reflect a regime transition. Over-instrumentation and aggressive calibration loops perturb the very coherence they seek to optimise. Gate fidelities fluctuate in ways that resist simple explanation. This framework reframes these problems as regime classification challenges. By identifying the experimental regime before attempting optimisation, and by treating measurement itself as a perturbation that must be managed, the framework provides a disciplined basis for reproducible quantum experimentation. 1.3 What This Document Is Not This document is a methods standard and experimental hygiene protocol. It does not propose new quantum interpretations or challenge existing theory. It does not claim that noise is beneficial, that decoherence can be reversed by observation, or that any particular performance outcome can be achieved by following these protocols. It is fully compatible with standard quantum mechanics and open quantum systems theory. It treats null results as informative data and is designed to improve interpretability and reproducibility without making claims about performance. 1.4 Design Principles The following principles are embedded throughout this document and should be treated as standing instructions: Regime identification before optimisation: identify the regime before attempting to improve performance. Stability before fidelity: a system in a stable regime is more valuable than a system showing intermittent high fidelity. Recovery before intervention: verify that the system can return to baseline after perturbation before applying further changes. Noise characterisation before suppression: understand the noise spectrum before attempting to suppress it. Collapse as data, not failure: the loss of coherence under specific conditions is informative, not a result to be discarded.