Quantum Fractal Spacetime (QFS) has been proposed as a scale-invariant framework in which the smooth macroscopic spacetime of general relativity emerges from a nondifferentiable microscopic geometry with effective Hausdorff dimension D ≈ 2. Existing QFS work suggests that scale-dependent path lengths, vacuum fluctuations, and reduced ultraviolet dimensionality could generate experimentally accessible noise and decoherence in quantum systems. Here we develop a falsifiable test program that maps QFS-inspired spacetime fluctuations onto observables available in present-day superconducting and trapped-ion quantum hardware. We combine two modern descendants of Wheeler’s spacetime-foam intuition—holographic-like correlated geometric noise and intrinsic decoherence sourced by quantum spacetime itself—into a common effective qubit-noise framework. In this description, QFS contributes both local colored dephasing and nonlocal phase correlations, which can be probed with Ramsey interferometry, dynamical decoupling, rotating-frame relaxometry, multilevel spectroscopy, and cross-qubit covariance analysis. The resulting near-term experimental signatures are: (i) an irreducible residual 1/fα phase-noise floor that survives aggressive subtraction of known technical noise, (ii) decoherence rates that scale systematically with transition energy or qudit level, and (iii) spatially correlated phase fluctuations across qubits or devices that cannot be explained by shared electronics, cryogenic vibrations, cosmic rays, or environmental backgrounds. We show that superconducting processors and trapped-ion platforms provide complementary leverage: transmons offer high bandwidth, dense multiplexing, and multilevel access, while trapped ions provide extreme coherence, narrow spectroscopic control, and substrate-independent cross-checks. We further place the proposal in the context of existing bounds from interferometric holographic-noise searches and neutrino decoherence constraints, arguing that qubit experiments are not redundant because they probe internal phase evolution of bound quantum systems rather than free propagation alone. The framework developed here turns near-term quantum processors into tabletop sensors of QFS-inspired spacetime phenomenology and, at minimum, enables meaningful bounds on a broad class of fractal-spacetime couplings.
Quantum Fractal Spacetime (QFS) has been proposed as a scale-invariant framework in which the smooth macroscopic spacetime of general relativity emerges from a nondifferentiable microscopic geometry with effective Hausdorff dimension D ≈ 2. Existing QFS work suggests that scale-dependent path lengths, vacuum fluctuations, and reduced ultraviolet dimensionality could generate experimentally accessible noise and decoherence in quantum systems. Here we develop a falsifiable test program that maps QFS-inspired spacetime fluctuations onto observables available in present-day superconducting and trapped-ion quantum hardware. We combine two modern descendants of Wheeler’s spacetime-foam intuition—holographic-like correlated geometric noise and intrinsic decoherence sourced by quantum spacetime itself—into a common effective qubit-noise framework. In this description, QFS contributes both local colored dephasing and nonlocal phase correlations, which can be probed with Ramsey interferometry, dynamical decoupling, rotating-frame relaxometry, multilevel spectroscopy, and cross-qubit covariance analysis. The resulting near-term experimental signatures are: (i) an irreducible residual 1/fα phase-noise floor that survives aggressive subtraction of known technical noise, (ii) decoherence rates that scale systematically with transition energy or qudit level, and (iii) spatially correlated phase fluctuations across qubits or devices that cannot be explained by shared electronics, cryogenic vibrations, cosmic rays, or environmental backgrounds. We show that superconducting processors and trapped-ion platforms provide complementary leverage: transmons offer high bandwidth, dense multiplexing, and multilevel access, while trapped ions provide extreme coherence, narrow spectroscopic control, and substrate-independent cross-checks. We further place the proposal in the context of existing bounds from interferometric holographic-noise searches and neutrino decoherence constraints, arguing that qubit experiments are not redundant because they probe internal phase evolution of bound quantum systems rather than free propagation alone. The framework developed here turns near-term quantum processors into tabletop sensors of QFS-inspired spacetime phenomenology and, at minimum, enables meaningful bounds on a broad class of fractal-spacetime couplings.
Version: v1.0 DESCRIPTION: We introduce Coherence Field Dynamics (CFD), a theoretical framework that extends holographic quantum gravity by promoting quantum coherence — the off-diagonal density matrix elements — to an independent geometric degree of freedom. While standard holographic frameworks (AdS/CFT, Ryu-Takayanagi) encode bulk geometry through entanglement entropy alone, CFD posits that coherence parameterizes effective bulk depth, complementary to entanglement's encoding of connectivity. The coherence field φ(p,γ) satisfies a wave equation in information-geometric parameter space, generating a Lorentzian metric that degenerates at a critical decoherence threshold γ_c. The framework predicts the existence of such a threshold from geometric stability analysis; its specific numerical value is system-dependent. Connections are established between information geometry, MERA tensor networks, and holographic entropy. The variational principle coupling coherence to an effective gravitational action is presented as an analogue gravity model (c and G are effective parameters), not a claim about physical 4D spacetime. Key results: Theoretical framework: coherence field equation, information-geometric metric, variational principle, and five testable predictionsCompanion experimental work demonstrates a fidelity threshold at γ ≈ 0.535 on IonQ Forte-1 (F = 0.988 baseline, collapse to F ≈ 0 under dephasing) and consistency with the dephasing response on Pasqal FRESNEL_CAN1 QPU (noise ratio 1.13×). These results are consistent with CFD's predicted critical behavior, though they do not uniquely distinguish CFD from standard noise models. The specific threshold value (0.535) is determined by the experimental circuit geometry, not derived from CFD aloneFour predictions remain open and experimentally accessible on current NISQ hardware: coherence-depth complementarity, MERA-decoherence correspondence, coherence-modulated entropy scaling, and hardware demonstration of non-trivial reversibilityThis paper presents the theoretical framework. The detailed experimental protocols and hardware data are reported in the companion publication "Cross-Platform Noise Thresholds in Quantum Teleportation: Trapped-Ion and Neutral-Atom Architectures" (see Related Identifiers).
We present a general open-quantum-system framework to model decoherence induced by stochastic Planck-scale fluctuations of spacetime, focusing on the κ -Minkowski noncommutative geometry as a representative quantum gravity scenario. Treating the deformation parameter as Gaussian white noise, we derive a Lindblad-type master equation applicable to arbitrary quantum systems and obtain a distinctive inverse-energy scaling of the decoherence rate, Γ ∝ E − 4 . As an illustrative example, we analyze a three-level system motivated by neutrino flavor oscillations and derive closed-form expressions for survival and transition probabilities with spacetime-induced damping. The E − 4 scaling contrasts sharply with the positive power laws often invoked in quantum gravity phenomenology and predicts negligible decoherence for high-energy neutrinos—consistent with IceCube observations—while implying that the strongest effects arise in the extreme low-energy regime. In this context, the sub-eV-scale energies characteristic of the cosmic neutrino background provide a natural infrared benchmark for illustrating the enhanced sensitivity to quantum spacetime fluctuations. Our results establish a unified formalism connecting quantum information methods, open-system dynamics, and quantum spacetime phenomenology, thereby offering a framework for exploring potential signatures of Planck-scale physics in future low-energy neutrino studies.
We present a general open-quantum-systems framework to model decoherence induced by stochastic Planck-scale fluctuations of spacetime, focusing on the kappa-Minkowski noncommutative geometry as a representative quantum-gravity scenario. Treating the deformation parameter as Gaussian white noise, we derive a Lindblad-type master equation applicable to arbitrary quantum systems and obtain a distinctive inverse-energy scaling of the decoherence rate, Gamma proportional to E^{-4}. As an illustrative example, we analyze a three-level system motivated by neutrino flavor oscillations and derive closed-form expressions for survival and transition probabilities with spacetime-induced damping. The E^{-4} scaling contrasts sharply with the positive power laws often invoked in quantum-gravity phenomenology and predicts negligible decoherence for high-energy neutrinos consistent with IceCube observations, while implying that the strongest effects arise in the extreme low-energy regime. In this context, the sub-eV-scale energies characteristic of the cosmic neutrino background provide a natural infrared benchmark for illustrating the enhanced sensitivity to quantum-spacetime fluctuations. Our results establish a unified formalism connecting quantum-information methods, open-system dynamics, and quantum-spacetime phenomenology, thereby offering a framework for exploring potential signatures of Planck-scale physics in future low-energy neutrino studies.
Every matter-based qubit platform—superconducting circuits, trapped ions, nitrogen- vacancy centres—exhibits decoherence in excess of what the standard two-level error model predicts from known noise sources. In superconducting qubits, two-level system (TLS) defect coupling accounts for 30–50% of the dephasing budget with debated mi- croscopic origin. In trapped ions, anomalous motional heating exceeds Johnson noise predictions by two to six orders of magnitude. In NV centres, residual pure dephasing persists after the nuclear spin bath and all identified sources are eliminated. These phenomena are platform-specific in detail but share a common structural feature: they all involve coupling of the qubit’s spin-projection state to spatial or motional degrees of freedom that the two-level model does not describe. Photonic qubits, by contrast, exhibit none of these anomalies. We propose that this asymmetry has a topological origin. A recent classifica- tion of electromagnetic field configurations into open (Class O, massless) and closed (Class C, massive) Poynting topologies [1] implies that massive particles carry internal structure—chirality, spatial mode geometry, Beltrami eigenstate classification—beyond their spin projection. Photons do not. The anomalous decoherence channels observed in every matter-based platform, and absent in every photonic platform, are the envi- ronmental coupling to this internal topological structure that the standard qubit model omits. This is not a small correction: the topological channels account for 5–50% of the observed decoherence, depending on the platform, and their platform-specific coupling fractions are consistent with known spin-to-spatial-mode coupling mechanisms at each scale.
Decoherence and parameter fluctuations are two of the mayor obstacles for solid-state quantum computing. In this work, decoherence in superconducting qubits of the transmon type is investigated. For this purpose, a time-multiplexed measurement protocol was developed and applied in long-term measurements. The resulting simultaneous measurement of the qubit's relaxation and dephasing rate, as well as its resonance frequency enables analysis of correlations between these parameters. A spectral noise analysis complements these measurements. Together, the results agree well with the interacting defect model of two-level-systems and yield information about the microscopic origin of the intrinsic decoherence mechanisms in Josephson qubits. Our measurements show inherent correlations between dephasing and fluctuations in qubit frequency on the timescale of seconds to days, which is attributed to the influence of individual defects, located close to conductor edges. Cross-correlation and spectral noise analysis confirm this interpretation and ascribe the source of fluctuation to interactions between thermal fluctuators and surface defects. Single defects reducing the coherence of qubits by up to one order of magnitude are a major challenge for future quantum computers. Non-tunable qubits are intrinsically insensitive to some decoherence channels and thus ideal for this fundamental analysis. However, to widen the focus and contrast the results of different material systems, we pursue the fabrication of voltage controlled gatemon qubits. In the course of this work, the theoretical foundation and technical implementation of transmon qubits based on regular Josephson weak links, and semiconducting nanowires is given. The experimental design and measurement setup are explained in detail. Our findings make continuous re-calibration a necessity in today's solid-state qubits, although new materials or processing techniques might mitigate the problem. However, the results of this work imply that fundamental improvements of qubit parameter stability are necessary in order to realize scalable and coherent qubit circuits.
The challenge of making nano-scale quantum systems experimentally accessible is being overcome for an increasing diversity of systems by improved fabrication techniques and experimental control. Despite rapid progress, one of the main hindrances in all experiments is the difficulty of isolating the quantum system from the surrounding environment and its fluctuations. This experimental “noise” perturbs the quantum system, a process that is generally referred to as decoherence: the system slowly loses its distinguishing quantum features. In this thesis the effects of spatial correlations in the noise environment with a finite correlation length are investigated. The consequences for the experimental design of controlled quantum systems as well as the dynamics of solid state systems are presented. We utilize the Bloch-Redfield formalism, a Markovian master equation approach, which gives a close connection to the underpinning system-environment model. We show how to use this formalism to model any spatial correlation function of the noise environment. Using microscopic environmental models, several correlation functions are derived and their properties connected to the environmental parameters. Several phenomenological correlation functions are also studied and a mapping to the Lindblad master equation is presented, which provides a test of positivity for phenomenological models. For quantum transport through spin chains and networks, noise is generally detrimental. Spatial correlations however reduce the effect of dephasing noise and can reinstate the transport dynamics. The critical correlation length proves to be closely connected to the maximal packet width of one excitation in the transfer process. For dissipation noise, relaxation-free states emerge with spatial correlations. The decay of an excitation is therefore fundamentally modified into a fast decay towards an intermediate relaxation-reduced state and a subsequent decay to the ground state on a much longer time scale. In quantum metrology noise correlations have been observed in experiments with trapped ions, in which they limit the use of such experiments for metrology. Quantum advantage, i.e. a better precision scaling than the standard quantum limit has been proven impossible in the presence of uncorrelated Markovian noise only. We show that for certain optimized states the best possible quantum advantage, Heisenberg scaling, can be achieved in the presence of noise with a finite spatial decay of correlations. We furthermore identify how dephasing effects change and a topology dependence arises in strength with increasing correlation length for entangled states in a general way. Biological photosynthetic complexes have recently been found to potentially include quantum coherent dynamics, particularly in the process of transmitting an exciton from the point of creation to the reaction centre. We show how the formalism of spatially correlated decoherence adapts to this significantly different energy regime. Typical effects of decoherence in this field are presented and we show how the light-harvesting efficiency is influenced by spatial correlations in the noise. This thesis highlights the fundamental relevance of noise correlations to several fields of quantum physics and the importance of the efficient and comprehensive modelling techniques presented.