Characterising Quantum Phenomena

Vinicius P. Rossi, Matty J. Hoban, Ana Belén Sainz

Abstract Characterising non-classical quantum phenomena is crucial not only from a fundamental perspective, but also to better understand its capabilities for information processing and communication tasks. In this work, we focus on exploring the characterisation of Einstein–Podolsky–Rosen inference (a.k.a. steering): a signature of non-classicality manifested when one or more parties in a Bell scenario have their systems and measurements described by quantum theory, rather than being treated as black boxes. We propose a way of characterising common-cause assemblages from the correlations that arise when the trusted party performs tomographically-complete measurements on their share of the experiment, and discuss the advantages and challenges of this approach. Within this framework, we show that so-called almost quantum assemblages satisfy the principle of macroscopic noncontextuality, and demonstrate that a subset of almost quantum correlations recover almost quantum assemblages in this approach.

John Richard Smith

Abstract This paper proposes a conservative reinterpretation of quantum phenomena within standard Hilbert space formalism. Rather than treating superposition, decoherence, and measurement as ontologically distinct primitives requiring separate explanatory frameworks, we suggest these phenomena can be coherently understood as dynamical regimes of a single system oscillating between two macrostates: a coherent steady-state regime characterised by constraint-aligned stability, and a transient underconstrained regime characterised by temporarily increased degrees of freedom. Within this framing, decoherence is reinterpreted not as collapse or information loss, but as natural dynamical recovery toward a coherence attractor following environmental perturbation. This interpretive compression introduces no new postulates, no modifications to the quantum formalism, and no claims of empirical novelty. It is offered as a conceptual reorganisation that may reduce interpretive proliferation by unifying apparently disparate phenomena under a common dynamical description. The approach is compatible with standard decoherence theory and maintains neutrality with respect to existing interpretations of quantum mechanics.

Collective

Martin Pieper

Gerardo Ortíz, C. D. BATISTA

We introduce an algebraic framework for interacting quantum systems that enables studying complex phenomena, characterised by the coexistence and competition of various broken symmetry states of matter. The approach unveils the hidden unity behind seemingly unrelated physical phenomena, thus establishing exact connections between them. This leads to the fundamental concept of universality of physical phenomena, a general concept not restricted to the domain of critical behaviour. Key to our framework is the concept of languages and the construction of dictionaries relating them.