We present a unified metric framework describing the loss of spatial interference visibility in relativistic quantum superposition states driven by path-dependent proper-time mismatch. By condensing special-relativistic kinematic time dilation and general-relativistic gravitational redshift into a single, dimensionless differential proper-time rate parameter, ∆τ̇ ≡ |∆Φ/c² − v∆v/c²|, we trace the evolution of spatial trajectories coupled to an internal clock ensemble. Using the reduced density matrix formalism and tracing over internal degrees of freedom, we show that a continuous internal energy dispersion ∆E generates path-discriminating phase information. Evaluating the Fourier transform of a Gaussian spectrum yields an exact, closed-form expression for the spatial coherence envelope decay, defining the characteristic coherence timescale τG = ℏ/(∆E · ∆τ̇). We delineate the physical boundary of this framework: elementary point particles lacking internal energy variance (∆E = 0) experience a deterministic relative phase shift while retaining full quantum contrast, whereas composite systems (∆E > 0) undergo spatial decoherence through relativistically induced path distinguishability. Finally, we demonstrate that expanding the rest-mass phase factor exp(−imc²τ/ℏ) in the weak-field, low-velocity limit naturally yields the time-dependent Schrödinger equation, confirming full compatibility with standard non-relativistic quantum mechanics.
We present a unified metric framework describing the loss of spatial interference visibility in relativistic quantum superposition states driven by path-dependent proper-time mismatch. By condensing special-relativistic kinematic time dilation and general-relativistic gravitational redshift into a single, dimensionless differential proper-time rate parameter, ∆τ̇ ≡ |∆Φ/c² − v∆v/c²|, we trace the evolution of spatial trajectories coupled to an internal clock ensemble. Using the reduced density matrix formalism and tracing over internal degrees of freedom, we show that a continuous internal energy dispersion ∆E generates path-discriminating phase information. Evaluating the Fourier transform of a Gaussian spectrum yields an exact, closed-form expression for the spatial coherence envelope decay, defining the characteristic coherence timescale τG = ℏ/(∆E · ∆τ̇). We delineate the physical boundary of this framework: elementary point particles lacking internal energy variance (∆E = 0) experience a deterministic relative phase shift while retaining full quantum contrast, whereas composite systems (∆E > 0) undergo spatial decoherence through relativistically induced path distinguishability. Finally, we demonstrate that expanding the rest-mass phase factor exp(−imc²τ/ℏ) in the weak-field, low-velocity limit naturally yields the time-dependent Schrödinger equation, confirming full compatibility with standard non-relativistic quantum mechanics.
Current attempts to probe general relativistic effects in quantum mechanics focus on precision measurements of phase shifts in matter–wave interferometry. Yet, phase shifts can always be explained as arising because of an Aharonov–Bohm effect, where a particle in a flat space–time is subject to an effective potential. Here we propose a quantum effect that cannot be explained without the general relativistic notion of proper time. We consider interference of a 'clock'—a particle with evolving internal degrees of freedom—that will not only display a phase shift, but also reduce the visibility of the interference pattern. According to general relativity, proper time flows at different rates in different regions of space–time. Therefore, because of quantum complementarity, the visibility will drop to the extent to which the path information becomes available from reading out the proper time from the 'clock'. Such a gravitationally induced decoherence would provide the first test of the genuine general relativistic notion of proper time in quantum mechanics. In the theory of general relativity time flows at different rates depending on the space–time geometry. Here, a drop in the visibility of a quantum 'clock' interference in a gravitational potential is predicted, which cannot be explained without the general relativistic notion of time.
We present a phase-based formulation of special relativity in which the kinematical structure of the theory is reconstructed from the requirement of phase coherence of localized wave states. Starting from the assumption that physical propagation is associated with surfaces of constant phase and that matter admits an intrinsic rest-frame oscillation, we show that the relativistic relations for time dilation, energy, and momentum follow from the invariant accumulation of phase along particle trajectories. In this framework, proper time is identified operationally as the phase count of an internal clock, and the Minkowski interval arises as the quadratic form consistent with phase invariance across inertial observers. The relation between mass and rest-frame frequency emerges naturally, providing a unified interpretation of relativistic kinematics in wave-mechanical terms. This formulation does not introduce new dynamics but offers a coherent structural perspective that bridges relativistic kinematics and wave propagation.
In this work, we study the emergence of relativistic effects in a composite quantum clock within the Page-Wootters relational formulation of quantum mechanics. We consider a system with internal and center-of-mass degrees of freedom and analyze the conditioned evolution of the center-of-mass relative to the internal system treated as an internal clock. We show that the internal sector exhibits an effective time dilation. Retaining the full mass-energy structure of the composite particle, a back-reaction of the internal energy on the center-of-mass sector appears through an operator-valued normalization factor. As a direct consequence of the back-reaction, the conditioned center-of-mass dynamics is governed by a Schroodinger equation that is non-local in the clock time, with an effective temporal non-locality of the order of the Compton time of the composite system. Applying the formalism to a center-of-mass momentum superposition, we find that the interferometric visibility acquires a correction that is quadratic in the internal energy, and therefore depends on the absolute distribution of clock energies rather than only on the energy gaps that control the standard time-dilation dephasing. Although this correction is parametrically small, it is a generic feature of relativistic composite clocks and can, in principle, be isolated through a differential visibility measurement comparing clocks with equal transition frequency but different mean internal energies.
In general relativity, the description of spacetime relies on idealised rods and clocks, which identify a reference frame. In any concrete scenario, reference frames are associated to physical systems, which are ultimately quantum in nature. A relativistic description of the laws of physics hence needs to take into account such quantum reference frames (QRFs), through which spacetime can be given an operational meaning. Here, we introduce the notion of a spacetime quantum reference frame, associated to a quantum particle in spacetime. Such formulation has the advantage of treating space and time on equal footing, and of allowing us to describe the dynamical evolution of a set of quantum systems from the perspective of another quantum system, where the parameter in which the rest of the physical systems evolves coincides with the proper time of the particle taken as the QRF. Crucially, the proper times in two different QRFs are not related by a standard transformation, but they might be in a quantum superposition one with respect to the other.Concretely, we consider a system of N relativistic quantum particles in a weak gravitational field, and introduce a timeless formulation in which the global state of the N particles appears "frozen", but the dynamical evolution is recovered in terms of relational quantities. The position and momentum Hilbert space of the particles is used to fix the QRF via a transformation to the local frame of the particle such that the metric is locally inertial at the origin of the QRF. The internal Hilbert space corresponds to the clock space, which keeps the proper time in the local frame of the particle. Thanks to this fully relational construction we show how the remaining particles evolve dynamically in the relational variables from the perspective of the QRF. The construction proposed here includes the Page-Wootters mechanism for non interacting clocks when the external degrees of freedom are neglected. Finally, we find that a quantum superposition of gravitational redshifts and a quantum superposition of special-relativistic time dilations can be observed in the QRF.
This paper introduces a dual-clock framework that unifies quantum mechanics, general relativity, and thermodynamics through a single dynamical equation governing temporal evolution. The model proposes that physical time emerges from interference between two counter-propagating temporal waves: an entropic wave driving phase-space exploration and a Lagrangian wave driving action minimization. Their interaction produces a universal refresh constant τ that regulates coherence across all physical systems. The framework recovers standard quantum and relativistic equations as limiting cases (τ = 0) while predicting measurable deviations for τ ≠ 0. The primary experimental prediction is a differential frequency offset between co-located optical atomic clocks of different species: δR ≈ -7 × 10⁻¹⁸, testable with emerging 10⁻¹⁹-precision clock technology. Numerical simulations demonstrate stability over 3.17 × 10¹⁵ equivalent years, reproducing FRW cosmological expansion, gravitational time dilation, and QED phase behavior. The model provides geometric explanations for quantum measurement collapse, black-hole singularities as temporal degree-of-freedom mergers, and biological quantum coherence in photosynthetic systems. This work presents a falsifiable, minimal extension to the Standard Model requiring no new particles or hidden dimensions, testable with near-term atomic clock experiments.
This work investigates the biophysical implications of a fundamental limit already established in the literature at the interface between quantum mechanics and relativity, namely, the decoherence induced by time dilation in composite systems, formally derived by Pikovski et al. This effect demonstrates that, even in the absence of an external environment, differences in proper time couple the internal and external degrees of freedom of quantum systems, leading to a loss of interferometric coherence as a direct consequence of the relativistic structure of spacetime. The present study does not introduce modifications to this formalism nor proposes new decoherence mechanisms; it starts explicitly from these results as a background physical constraint. Our objective is distinct: to analyze complex molecular systems operating persistently in non-equilibrium regimes — notably biological systems — in light of this universal limit. We propose that biochemical functionality should not be described solely by structural or energetic criteria, as in the classical spatial affinity paradigm (“lock-and-key”), but also by the system's ability to maintain temporal compatibility between its internal modes during finite operational intervals. We term this operational regime the Simultaneity Window, characterizing a dynamic condition of effective coherence sustained by a continuous flow of free energy. In this framework, processes involving the loss of functional viability can be modeled as the transition of the molecular system to the intrinsic decoherence regime predicted by relativistic-quantum theory, occurring when the variance of internal energy (ΔE) exceeds the range compatible with the maintenance of this operational coherence. The notion introduced here does not alter the underlying physical mechanism but identifies a domain in which biochemical systems explore — and need to circumvent — such a limitation. Based on this operational interpretation, we introduce the concept of Chrono-Inhibitors: agents capable of modifying the internal spectral distribution of a target biological system, shifting it in a controlled manner into the effective decoherence regime without requiring direct structural modification. We operationally define a \emph{chrono-inhibitor} as any external perturbation capable of altering the internal spectral variance ΔE without directly modifying the system's average structure.