We present, and mathematically describe, a proof-of-principle quantum-optical experiment that seemingly enables superluminal signaling, contrary to the import of the 'no-signaling' theorem.
A recently proposed gedanken experiment involving the (gravitational or electromagnetic) interaction between two objects---one placed in a state of quantum superposition of two locations---seems to allow for faster-than-light communication. However, it has been argued that, if the mediating fields are endowed with quantum properties, then the possibility for superluminal signaling is fully avoided. Moreover, in the gravitational case, this conclusion has been used to argue for the view that the gravitational field must be quantized. In this work, we clarify and complement some aspects of the discussion. In particular, by focusing on the way in which entanglement spreads across the components of the system, we offer some insights into the fundamental quantum features behind the impossibility of superluminal signaling and we provide a more general proof of such an impossibility in this and related protocols.
The no-signaling principle in quantum mechanics—that local operations on onesubsystem of an entangled pair cannot transmit information to a distant subsystem—has never been structurally proven from independent physical principles. Everyexisting derivation is circular: von Neumann constructed the tensor product for-malism specifically to enforce no-signaling [1], and all subsequent “proofs” deriveno-signaling from a structure that was designed to contain it [2, 3]. We present anon-circular structural proof. Starting from two premises independent of quantumformalism—the relativistic propagation limit c and the experimental record of Belltests, quantum erasers, and which-path experiments—we derive the no-signaling re-sult as a mathematical consequence of the tensor contraction structure. The proofproceeds in four steps: (i) the inscription tensor formalism, which encodes correla-tions in a rank-r tensor whose contraction rules are fixed by the mathematics, notby postulate; (ii) an exhaustive enumeration of all nine measurement configurationsfor an entangled pair, showing that partial contraction yields 12 in every case, in-dependent of the distant party’s choice; (iii) the cross-term kill theorem, provingthat one environmental inscription produces an exact, immediate, and idempotenttransition from quantum to classical probability structure; and (iv) the proof bycontrapositive via which-path and quantum eraser experiments, confirming bothdirections of the theorem against the complete experimental record. Four inde-pendent confirmations—information-theoretic, conservation-law, operational, andsymmetry-based—close every remaining escape route. The proof requires no newphysics, no new axioms, and no ontological commitment beyond what the existingformalism and experimental record already contain. We note that the Entropic Lat-tice Ontology’s fourth spatial degree provides a geometric explanation for why theproof works—the correlation occupies a spatial degree with no three-dimensionaladdress—but this theoretical framework is not required for the proof’s validity