Assuming the validity of the equivalence principle in the quantum regime, we argue that one of the assumptions of the usual definition of quantum mechanics, namely separation between the “classical” detector and the “quantum” system, must be relaxed. We argue, therefore, that if both the equivalence principle and quantum mechanics continue to survive experimental tests, then this favors “informational” interpretations of quantum mechanics (where formalism is built around relations between observables, defined as information that can be accessed by an observer of the system. In particular “collapse” is understood as a change of relative information as the detector interacts with the system) over “ontic ones” (assuming the physical reality of states and wave functions, which are assumed to be more than informational objects. In particular collapse is understood as a physical process). In particular, we show that relational-type interpretations can readily accommodate the equivalence principle via a minor modification of the assumptions used to justify the formalism. We qualitatively speculate what a full generally covariant quantum dynamics could look like, and comment on experimental investigations.
Assuming the validity of the equivalence principle in the quantum regime, we argue that one of the assumptions of the usual definition of quantum mechanics, namely separation between the “classical” detector and the “quantum” system, must be relaxed. We argue, therefore, that if both the equivalence principle and quantum mechanics continue to survive experimental tests, then this favors “informational” interpretations of quantum mechanics (where formalism is built around relations between observables, defined as information that can be accessed by an observer of the system. In particular “collapse” is understood as a change of relative information as the detector interacts with the system) over “ontic ones” (assuming the physical reality of states and wave functions, which are assumed to be more than informational objects. In particular collapse is understood as a physical process). In particular, we show that relational-type interpretations can readily accommodate the equivalence principle via a minor modification of the assumptions used to justify the formalism. We qualitatively speculate what a full generally covariant quantum dynamics could look like, and comment on experimental investigations.
There is a long history in both general relativity and quantum mechanics of removing fixed background structures, thereby making observed objects and measurement processes dynamical. We continue this evolution by combining central insights from both theories to argue that physical limits on information collection resulting from quantum gravity coupled with general covariance preclude the fixed information geometry still assumed in both information theory and quantum mechanics. As a consequence there must be a gravitized, generally covariant extension of both theories. We also propose a novel experimental test involving intrinsic triple and higher-order quantum interferences that would provide evidence for dynamical information metrics and a dynamical Born rule.
Quantum mechanics has transformed our understanding of reality, yet deep philosophical puzzles remain unresolved. Is there a consistent way to describe quantum measurement, the emergence of space and time, and the role of observers within one coherent ontology? This paper introduces Relational Quantum Dynamics (RQD), an interpretation that places relationships and information—not isolated objects—at the foundation of physics. Unlike traditional views, such as the Copenhagen interpretation, Everett’s many-worlds theory, or hidden-variable approaches, RQD denies a single observer-independent reality, instead proposing that facts only become definite within specific observational contexts. It explicitly addresses foundational no-go results, including Bell’s theorem, the Kochen–Specker theorem, and the Frauchiger–Renner paradox, by replacing absolute facts with relational, context-dependent truths. RQD rests on five interlocking principles: (1) quantum states are contextual and observer-relative, (2) time emerges from quantum interactions rather than existing as an external parameter, (3) space is constructed from patterns of quantum entanglement, (4) observers emerge as systems with highly integrated information, and (5) classical reality appears through quantum decoherence without special wavefunction collapse. Philosophically, RQD aligns with ontic structural realism, proposing that the fundamental ontology of the universe consists entirely of informational relations. It avoids collapsing into relativism or solipsism by ensuring intersubjective agreement through physical interactions. Ultimately, RQD may offer a unified picture in which quantum mechanics, spacetime, and observers are no longer separate domains but aspects of one interconnected informational web.
A recent concept in theoretical physics, motivated in string duality and M-theory, is the notion that not all quantum theories arise from quantising a classical system. Also, a given quantum model may possess more than just one classical limit. In view of these developments, we analyse some general properties that quantum mechanics must satisfy, if it is not to be formulated as a quantisation of a given classical mechanics. Instead, our approach to quantum mechanics is modelled on a statement that is close in spirit to the equivalence principle of general relativity, thus bearing a strong resemblance with the equivalence principle of quantum mechanics formulated by Faraggi-Matone.
The act of quantum measurement is traditionally regarded as an instantaneous collapse of the wavefunction, an idealization that underpins most interpretations of quantum mechanics. Recent advances in ultrafast measurement techniques, however, have begun to challenge this assumption by revealing temporal structure in the measurement process. This paper proposes a theoretical framework in which the measurement‑induced state change is preceded by a fundamental causal delay, denoted τ_m, that is intrinsic to the interaction between the quantum system and the measurement apparatus, rather than an artefact of detector bandwidth or environmental noise. We argue that τ_m represents a minimal temporal separation between the preparation of a quantum state and the definitive update of its ontic status, and we develop a simple dynamical model to illustrate how such a delay could manifest in experimental observables. The implications of a nonzero τ_m are far‑reaching: they necessitate a revision of the standard projection postulate, modify the causal structure of quantum histories, and suggest new pathways for quantum control protocols that exploit the window of delayed collapse. The paper concludes with a discussion of possible experimental tests using state‑of‑the‑art ultrafast photodetection and superconducting qubit readout, and outlines the theoretical modifications required to accommodate a quantum measurement causal delay within both Copenhagen‑style and relational interpretations of quantum theory.
Both classical and quantum mechanics assume that physical laws are invariant under changes in the way that the world is labeled. This Principle of Decompositional Equivalence is formalized, and shown to forbid finite experimental demonstrations that given pointer states |p1> and |p2> refer to the same physical system S. It is then shown that any extra-theoretical assumption that given pointer states |p1> and |p2> with indistinguishable coefficients in a Schmidt basis for the universe refer to the same physical system S is stronger than the assumption of classicality. Standard interpretations of quantum mechanics make such as assumption in analyzing measurement; hence they are logically inconsistent.
The act of quantum measurement is traditionally regarded as an instantaneous collapse of the wavefunction, an idealization that underpins most interpretations of quantum mechanics. Recent advances in ultrafast measurement techniques, however, have begun to challenge this assumption by revealing temporal structure in the measurement process. This paper proposes a theoretical framework in which the measurement‑induced state change is preceded by a fundamental causal delay, denoted τ_m, that is intrinsic to the interaction between the quantum system and the measurement apparatus, rather than an artefact of detector bandwidth or environmental noise. We argue that τ_m represents a minimal temporal separation between the preparation of a quantum state and the definitive update of its ontic status, and we develop a simple dynamical model to illustrate how such a delay could manifest in experimental observables. The implications of a nonzero τ_m are far‑reaching: they necessitate a revision of the standard projection postulate, modify the causal structure of quantum histories, and suggest new pathways for quantum control protocols that exploit the window of delayed collapse. The paper concludes with a discussion of possible experimental tests using state‑of‑the‑art ultrafast photodetection and superconducting qubit readout, and outlines the theoretical modifications required to accommodate a quantum measurement causal delay within both Copenhagen‑style and relational interpretations of quantum theory.