Recent models have demonstrated that quantum superpositions undergo inevitable decoherence due to gravitational time dilation, even in the absence of external classical environments. In this work, we show that such results can be naturally misinterpreted within the context of General Relativity as a Quantum Theory (GRQT) as a consequence of the geometric spectral stability of spacetime. Without modifying the known dynamic formalism, we interpret the decoherence time as an operational coherence limit imposed by the spectral discretization of geometry. The approach remains conservative, introduces neither new fields nor collapse mechanisms, and suggests experimental regimes where the effect can be tested.
Abstract In this paper, we study the phenomenon of quantum interference in the presence of external gravitational fields described by alternative theories of gravity. We analyze both non-relativistic and relativistic effects induced by the underlying curved background on a superposed quantum system. In the non-relativistic regime, it is possible to come across a gravitational counterpart of the Bohm–Aharonov effect, which results in a phase shift proportional to the derivative of the modified Newtonian potential. On the other hand, beyond the Newtonian approximation, the relativistic nature of gravity plays a crucial rôle. Indeed, the existence of a gravitational time dilation between the two arms of the interferometer causes a loss of coherence that is in principle observable in quantum interference patterns. We work in the context of generalized quadratic theories of gravity to compare their physical predictions with the analogous outcomes in general relativity. In so doing, we show that the decoherence rate strongly depends on the gravitational model under investigation, which means that this approach turns out to be a promising test bench to probe and discriminate among all the extensions of Einstein’s theory in future experiments.
We present a unified and minimal theoretical framework addressing the quantum-classical transition, the measurement problem, and the emergence of the arrow of time, grounded in gravitational physics. Building on the insight that quantum superpositions of mass distributions necessarily imply superpositions of gravitational potentials, we show that such states are unavoidably associated with superpositions of proper times due to gravitational time dilation. By extending the system Hilbert space to include a temporal degree of freedom, we demonstrate that matter-time entanglement leads naturally to effective decoherence when the time degree of freedom is traced out. The resulting reduced dynamics takes the form of a Lindblad master equation derived from an underlying unitary evolution. This framework reproduces the correct microscopic and macroscopic limits, clarifies the relation to Diósi-Penrose-type models, and provides a coherent account of classicality and temporal irreversibility without postulating observers, environmental decoherence as fundamental, or objective wavefunction collapse.
The gravitational decoherence field studies the suppression of coherence in quantum systems caused by effects rooted in the gravitational interaction. This models are not just important to yield interesting ideas about the search, in regimes others than the Planck scale, for the interplay between quantum mechanics and general relativity, but also from a theoretical point of view. The fact that the gravitational field can not be shielded opens the question of how strong will the gravitational ‘environment’ decohere a quantum system? and if this decoherence can somehow explain the absence of macroscopical super- positions? This thesis studies in depth the ‘Classical Channel Gravity’ (CCG) model, a recent proposal of gravitational decoherence that assumes that the gravitational interac- tion is always accompanied with an intrinsic decoherence mechanism which ensures that there is no transmission of quantum information between the parties involved. This model can be understood a series of weak continuous quantum measurements accompanied with a feedback term produced by some underlying hidden gravitational degrees of freedom. We first study all the possible emergent dynamics from collisional Markovian dynamics; these ones range from exact unitary to arbitrary fast decoherence (Zeno effect). The second part of the thesis is devoted to study the Newtonian and post Newtonian limits of the CCG model, with particular focus on the testability features of CCG. In particular, we apply this model to coupled clocks and find that the amount of decoherence predicted by CCG is the same as the decoherence that an ‘environment of clocks’ will imprint in a single clock in the context of unitary evolution. On the other hand, we find that this effect is far from being detectable with the current achieved time accuracy. However, CCG as a model for multi partite systems and two systems with very different masses seems to yield an amount of decoherence that is not only able to be detectable with current experiments but also seems to indicate that this model is ruled out. Nevertheless, we also mention potential caveats with our assumptions and discuss other physically motivated directions to further study this result. Finally, we also explore the extension of CCG for the cosmological scenario. In this context the scale factor is being decohered by test particles ‘sitting’ on spacetime. We find that this decoherence will be seen by an observer unaware of the CCG fundamental mechanism as an emergent form of dark energy filling the universe.
We propose a conservative theoretical framework addressing the emergence of classical time and the uniqueness of the past within quantum mechanics, without modifying its fundamental postulates or introducing objective collapse mechanisms. The central observation is that quantum superpositions of mass–energy distributions necessarily imply superpositions of gravitational potentials, and therefore superpositions of proper times. By treating time as an effective quantum degree of freedom and extending the system Hilbert space accordingly, we show that matter–time entanglement leads to an intrinsic dispersion of proper time. Gravitational fluctuations and irreversible memory formation dynamically suppress this dispersion, giving rise to an effective closure of temporal histories. The resulting dynamics admits stable fixed points corresponding to classical time and a unique past, while remaining fully compatible with global unitarity. We analyze the stability of this closure, its relation to decoherence and quantum Darwinism, and its implications for cosmology, including the interpretation of the Big Bang as a temporal closure process rather than a fundamental beginning of time. The framework clarifies the role of gravity in the quantum–classical transition and delineates the physical conditions under which a unique history can emerge.
Both quantum mechanics and general relativity are based on principles that defy our daily intuitions, such as time dilation, quantum interference and entanglement. Because the regimes where the two theories are typically tested are widely separated, their foundational principles are rarely jointly studied. Recent works have found that novel phenomena appear for quantum particles with an internal structure in the presence of time dilation, which can take place at low energies and in weak gravitational fields. Here we briefly review the effects of time dilation on quantum interference and generalize the results to a variety of systems. In addition, we provide an extended study of the basic principles of quantum theory and relativity that are of relevance for the effects and also address several questions that have been raised, such as the description in different reference frames, the role of the equivalence principle and the effective irreversibility of the decoherence. The manuscript clarifies some of the counterintuitive aspects arising when quantum phenomena and general relativistic effects are jointly considered.
This Volume III develops a complete geometric formulation of quantum mechanics, demonstrating that quantum phenomena emerge from the very structure of spacetime. We demonstrate that Einstein's field equations—when interpreted in the spectral domain and taking phase coherence into account—already contain the entire structure of quantization. Quantum mechanics appears not as an axiom, but as a geometric consequence. Based on the experimental and mathematical results consolidated in Volumes~0, I, and II, the present work shows that quantization need not be postulated: it arises inevitably from three fundamental geometric elements—proper frequency, parallel transport, and phase coherence. The action appears as the phase accumulated along the worldline, and its discretization into coherence windows, derived without external hypotheses, naturally leads to the condition
Sn=nh and to all associated quantum phenomenology. We derive the Schrödinger equation as the limit of short windows, obtain the commutator
[x,p]=iℏ from the incompatibility between spatiotemporal synchronizations, and reinterpret interference, propagators, and decoherence as spectral properties of parallel transport. The Hilbert space arises as the spectral space of the metric, observables correspond to generators of isometric deformations, while the collapse is understood as the geometric selection of coherent subspaces. The formalism extends to relativistic particles, spin, quantum statistics, the Dirac equation, harmonic oscillators, and field quantization, where spectral modes of the metric assume the role of particles: photons as harmonic 1-forms, weak modes as connections of 2-forms, gluons as 3-forms, and the Higgs as the fundamental scalar curvature mode. The reinterpretation of the Standard Model thus becomes a direct consequence of spectral geometry. The Volume culminates in the Central Theorem —Geometry = Quantization— showing that the entire quantum structure is a manifestation of the spectral granularity of spacetime. We conclude with experimental predictions and falsification criteria, as well as the conceptual framework necessary for Volume~IV, dedicated to the complete quantization of the metric within the same paradigm.