We propose a modification of the coupling between classical spacetime geometry and quantum matter in which the spacetime metric at each event is sourced by the stress-energy tensor evaluated on a locally decohered density matrix constructed from the causal past of that event. This replaces the usual semiclassical expectation value with a coarse-grained stress tensor derived from a decoherence channel acting on the quantum state restricted to the causal past. In this framework, decoherence determines which sector of the quantum state can influence classical spacetime geometry: coherent phase correlations remain present in the quantum state but do not source classical spacetime geometry. The resulting effective stress tensor is formulated to be covariant and compatible with the Bianchi identities under branchwise conservation. The framework avoids macroscopic-superposition paradoxes of the traditional semiclassical approach and predicts the absence of gravitationally mediated entanglement in the Bose–Marletto–Vedral protocol. Observation of such entanglement would therefore falsify the proposal.
We propose a modification of the coupling between classical spacetime geometry and quantum matter in which the spacetime metric at each event is sourced by the stress-energy tensor evaluated on a locally decohered density matrix constructed from the causal past of that event. This replaces the usual semiclassical expectation value with a coarse-grained stress tensor derived from a decoherence channel acting on the quantum state restricted to the causal past. In this framework, decoherence determines which sector of the quantum state can influence classical spacetime geometry: coherent phase correlations remain present in the quantum state but do not source classical spacetime geometry. The resulting effective stress tensor is formulated to be covariant and compatible with the Bianchi identities under branchwise conservation. The framework avoids macroscopic-superposition paradoxes of the traditional semiclassical approach and predicts the absence of gravitationally mediated entanglement in the Bose–Marletto–Vedral protocol. Observation of such entanglement would therefore falsify the proposal.
We argue that semiclassical gravity can be made consistent if quantum systems source gravity only when they participate in non-gravitational interactions that can lead to environment-induced decoherence, and which select conditional states that lead them to source such a field. If they do not participate in those interactions, systems do not contribute their stress-energy to the semiclassical equations, where regions lacking a gravitational field may remain flat. This proposal of conditional gravity is testable by probing the gravitational field sourced by systems, which should depend entirely on environment-induced decoherence in this context; by gravity not mediating entanglement in the Bose-Marletto-Vedral (BMV) experiment; and by how the reversibility of the initial state in this experiment would depend solely on this decoherence, distinguishing it from competing approaches. Our approach involves different theories. A distinct one involves chains of causally ordered interactions between quantum matter fields, which may show how gravity arises from QFT, and provide benefits to other areas of physics. To distinguish between the different theories that our approach allows for, and possibly test them, we present a generalization of the process operator and quantum causal models, which is applicable to quantum measurements in QFT implemented via the Fewster-Verch framework. However, we will also propose another approach. These different theories can be seen as arising from different ways quantum operations are classically controlled, since outcomes obtained along this chain determine which quantum operations are implemented next. We propose an experiment to test them using quantum circuits, which may allow us to probe how precisely gravity arises from quantum systems. We thus propose another application of quantum computers, which is to control the sourcing of gravity by quantum systems.
This note extends the quantum reference-frame framework from charge, time, and position to geometry itself. It studies the consequences of treating spacetime geometry as a quantum variable in exactly solvable models. An observer without access to a superposed geometry register is shown to possess a geometric information deficit: the inaccessible geometry information is quantified by the entropy of the geometry sectors. Conditioning on the geometry register recovers the individual geometric branches exactly, establishing geometry as a quantum reference frame with the same structure as charge, time, and position reference frames. The work studies clocks evolving in superposed gravitational redshifts and derives exact proper-time interference. Different geometric branches generate which-geometry records in the clock, producing decoherence and periodic recoherence according to the same information-transfer structure found throughout the reference-frame framework. The note further investigates the emergence of classical spacetime. Multiple quantum systems coupled to the same geometry register collectively decohere the geometric superposition faster than a single system, while non-universal coupling does not produce the same amplification. This provides an exactly solvable realization of the idea that spacetime classicality can emerge through continuous measurement by matter. Finally, the paper derives the effective energy-product interaction used in gravitationally induced entanglement models. By introducing a dynamical geometry mode sourced by matter energy and eliminating the mediator, the familiar energy-product coupling emerges directly from the quantum geometry model rather than being assumed. The results connect quantum reference frames, proper-time superposition, gravitationally induced decoherence, gravitational entanglement, and the emergence of classical geometry within controlled finite models. The declared limits are finite geometry registers, simplified sourced geometry modes, and no claim of a complete theory of dynamical quantum gravity. Verification and reproducibility materials are included.
We formulate the gravitationally induced quantum decoherence of a massive object prepared in a spatial superposition. Starting from linearized gravity coupled to a massive system particle and an environmental scalar field, we derive a closed-time-path influence functional governing the reduced system dynamics. In the nonrelativistic and quasi-static regime, the decoherence exponent can be written as a bilinear functional of the difference of the system stress-energy tensors and an effective noise kernel obtained by dressing the environmental stress-energy tensor correlator with graviton propagators. We then apply this framework to the Newtonian long-range gravitational interaction and evaluate the resulting decoherence function for a dilute nonrelativistic gas modeled by finite wave packets and coarse-grained in time and space. By performing controlled approximations, we obtain analytic expressions for the cumulative decoherence function and show that the dominant contribution is accumulated logarithmically over a broad range of distances, while remaining subdominant to conventional collisional decoherence under realistic conditions.
We present Chronon Field Theory (CFT), a covariant framework in which large–scale spacetime geometry—including temporal order and causal structure—emerges from the coarse–grained dynamics of a single future–directed timelike field Φμ(x). Within this approach, both the unit–norm property of Φμ and the Lorentzian signature of gμν are not postulated but arise uniquely from random microscopic chronon dynamics under broad symmetry and locality assumptions. Quantum phenomena are reinterpreted in this geometric setting: double–slit interference results from phase–coherent Φ–threads rather than superposed particle paths, and measurement appears as a boundary–induced alignment of microscopic orientations with the apparatus’s macroscopic field, yielding definite outcomes without collapse or branching. Schrödinger’s cat is then a straightforward macro–micro coupling with no persistent macroscopic superposition, while EPR–type entanglement reflects shared Φ–thread ancestry across spacelike separations. The Born rule follows from the unbiased martingale structure of alignment dynamics and from coarse–graining symmetries, making it an emergent statistical law; the uncertainty principle appears as a statistical bound on chronon fluctuations, with ℏ arising as the variance of coarse–grained action. CFT thus provides a covariant and ontologically economical framework linking spacetime symmetries to quantum measurement, and predicts scale–dependent effects—such as nonlinear decoherence and curvature–sensitive timing shifts—that are open to experimental test.
Abstract We propose a covariant multiverse framework in which quantum phenomena arise effectively for observers restricted to a single semiclassical universe. Each universe is endowed with a classical Lorentzian metric and a scalar--tensor sector that realizes a spacetime- and age-dependent gravitational coupling G(x,τ), where τ is a cosmic-age scalar defined with respect to a preferred cosmological congruence. Inter-universe interactions are modeled by proximity-weighted couplings that permit coherent amplitude exchange between nearby universes and by stochastic sector events that induce transitions and decoherence. For an observer in a given universe, tracing over the remaining sectors yields a reduced, open-system description that is linear and completely positive in the weak-coupling/Markovian regime, providing an explicit route to Lindblad-type generators. Metric superpositions are excluded within each universe by construction; apparent ``superpositions of geometries'' are instead identified with coherence over universe labels, with a definite classical geometry in every sector. We relate this construction to Many-Interacting-Worlds models, semiclassical and stochastic gravity, and standard open-quantum-systems techniques, and we outline phenomenological constraints from bounds on G˙/G and proposed gravitationally mediated entanglement tests. We outline concrete next steps, including toy-model demonstrations of interference and tunneling, parameterization of scalar–tensor functions consistent with Solar-System bounds, and quantitative predictions for gravitationally mediated entanglement experiments. We supplement the conceptual framework with quantitative toy-model demonstrations (qutrit and oscillator), including plots of coherence C01(t), purity P(t), and interferometric visibility V(t), and we illustrate departures from Markovian LGKS dynamics via time-dependent rates in a non-Markovian variant.
We propose a geometric decoherence mechanism within the rotational-order unification framework built upon the Zhang Effective Metric. Stochastic zero-point fluctuations of the internal S³ orientation field generate fluctuations of the effective spacetime metric, imprinting random relative phases on quantum superpositions. The derived decoherence rate scales as M² at leading order, naturally suppressing macroscopic superpositions while preserving coherence for microscopic particles. This mechanism is qualitatively distinct from Diósi–Penrose / Károlyházy gravitational decoherence: the metric fluctuations originate from the internal fibre geometry rather than the mass distribution of the quantum system itself. The fluctuations couple only to massive matter-wave phases at leading order and do not produce photon dispersion. This work predicts a universal, shielding-insensitive noise floor for macroscopic quantum experiments.