Eur. Phys. J. Plus (2026) 141: 152
https://doi.org/10.1140/epjp/s13360-026-07324-1

Regular Article

Quantum-first engineering of causal structure: from Uhlmann correlations to a local sector with a wider true front

FAST Foundation, 32541, Destin, FL, USA

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Received: 24 September 2025
Accepted: 13 January 2026
Published online: 13 February 2026

Abstract

What if physics had discovered quantum mechanics first, and only later constructed relativity from it? In this quantum-first perspective, the causal structure of spacetime—usually taken as a primitive axiom fixed by Einstein’s postulate of a universal speed of light—emerges instead as a property of the correlation geometry of many-photon states. We explore this inversion systematically. Starting from the purification of classical electromagnetic waves by ancillas, we employ the Uhlmann bundle and its associated gauge connection to encode classical attributes (phase, wavelength, coherence, polarization) as specific quantum correlations. Ancilla manipulations then introduce a correlation gauge Q(k, t) which directly controls interference conditions in multimode light. This reshapes the operational cone inferred from coherence ridges or wave packet maxima, permitting superluminal group velocities as emergent interference effects. Crucially, we then distinguish this operational cone from the true front cone, defined by the support of the retarded response function and responsible for microcausality. To alter the latter requires new sector dynamics. We therefore propose a minimal, gauge-invariant correlation-dressed Maxwell theory in which the ultraviolet kinetic term depends on a correlation order parameter $\mathrm{\Sigma }[Q]$ (and optionally on a topological Uhlmann charge $Q_{\text{top}}$). In such a prepared sector, the local front velocity becomes $c_{\text{front}}=\frac{c}{\sqrt{1-\xi (\mathrm{\Sigma })}}\sim c\sqrt{1+\xi (\mathrm{\Sigma })}$, exceeding the usual vacuum c while preserving causality relative to the new cone. This is not an aether: the preferred direction $u^{\mu }$ is defined only by the prepared quantum state, and outside the engineered region standard relativity holds. We outline decisive experimental tests in vacuum: (i) front timing at fixed false-positive rate, scaling linearly with path length, (ii) Kramers–Kronig analysis of the complex transfer function to detect a shifted high-frequency asymptote, (iii) anisotropy under programmed rotation of $u^{\mu }$, and (iv) discrete front steps from topological Uhlmann sectors. Extended “correlation-condensate bubbles” or Floquet shells could realise regions of tens of metres with modified cones. If verified, the framework legitimises entropic force phenomenology, predicts mass and coupling shifts, and offers a falsifiable, laboratory-based route to controlled causal structure engineering. In contrast to Alcubierre-type proposals, our method requires no exotic matter, only the controlled quantum correlation of light with ancillas. This abstract thus articulates both a conceptual inversion—relativity from quantum correlations—and an experimental plan to probe whether the true front velocity of light in vacuum can be increased by quantum engineering.