From Quantum Collapse to Coherence: A New Framework for Wigner’s Friend and the Frauchiger-Renner Paradox

Abstract

Wigner’s Friend and the Frauchiger-Renner paradox explore fundamental tensions in quantum mechanics, particularly how measurement, observer perspectives, and entangled states yield contradictory or paradoxical conclusions when extended universally. Conventional treatments prioritize wavefunction collapse or large-scale entanglement, often neglecting the role of partial decoherence. Here, I develop a “Wigner’s Buddy” framework that refocuses these thought experiments on quantum coherence, treating measurement as a continuous, environment-driven process rather than an abrupt collapse. By systematically quantifying off-diagonal terms through measures such as the ℓ1-norm or relative entropy of coherence, and employing techniques that measure coherence such as tomography, interferometry, and ultrafast spectroscopy, I highlight how gradual phase damping reconciles local classicality with residual global coherence. This approach surpasses limitations of fragility in entanglement-based protocols, addresses nested-observer inconsistencies without invoking universal collapse, and accommodates real-world noise in biological systems such as photosynthesis, magnetoreception. Coherence thus bridges theoretical paradoxes and practical phenomena, demonstrating a scalable mechanism by which quantum effects can persist in macroscopic or dissipative environments.In doing so, it aligns Wigner’s Friend and Frauchiger-Renner analyses with a broader spectrum of interpretative frameworks—including Copenhagen, Many-Worlds, relational, Bayesian perspectives, and pilot-wave views—while underscoring the adaptability of quantum mechanics across multiple scales and contexts. Moreover, this perspective resonates with quantum Darwinism, which posits that the environment redundantly encodes pointer states, promoting effective classical objectivity from purely quantum substrates. By clarifying how partial decoherence can stabilize measurement outcomes, the “Wigner’s Buddy” proposal enhances our understanding of quantum theory’s capacity to describe itself without logical contradictions. It also has implications for quantum computing, where maintaining and controlling coherence amid noise is pivotal for scalable information processing. Furthermore, analyzing coherence measures can, in principle, distinguish gradual phase suppression from hypothetical non-unitary collapse if robust empirical tests are devised, though interpretation remains context-dependent. Ultimately, this modification unifies theoretical paradoxes with real-world systems, suggesting that coherence-based approaches can illuminate the transition from micro-level superpositions to macro-level classicality and guide future developments in both foundational studies and emergent quantum technologies.