A formulary for the application of the Diosi-Penrose criterion to solids in quantum superpositions is developed, which takes the solid's microscopic mass distribution (resulting from its nuclei) and its macroscopic shape into account, where the solid's states can differ by slightly different positions or extensions of the solid. For small displacements, smaller than the spatial variation of the solid's nuclei, the characteristic energy of the Diosi-Penrose criterion is mainly determined by the mass distribution of the nuclei. For large displacements, much larger than the solid's lattice constant, the solid can be idealised as a continuum, and the characteristic energy depends on the solid's shape and the direction of the displacement. In Diosi's approach, in which the mass density operator has to be smeared, the solid's microscopic mass distribution plays no role. The results are applied to a special single-photon avalanche photodiode detector, which interacts as little as possible with its environment. This is realised by disconnecting the detector from the measurement devices when it is in a superposition, and by biasing the photodiode by a plate capacitor, which is charged shortly before the photon's arrival. For a suitable choice of components, the detector can stay in a superposition for seconds; its lifetime can be shortened to microseconds with the help of a piezoactuator, which displaces a mass in the case of photon detection.
A formulary for the application of the Diosi-Penrose criterion to solids in quantum superpositions is developed, which takes the solid's microscopic mass distribution (resulting from its nuclei) and its macroscopic shape into account, where the solid's states can differ by slightly different positions or extensions of the solid. For small displacements, smaller than the spatial variation of the solid's nuclei, the characteristic energy of the Diosi-Penrose criterion is mainly determined by the mass distribution of the nuclei. For large displacements, much larger than the solid's lattice constant, the solid can be idealised as a continuum, and the characteristic energy depends on the solid's shape and the direction of the displacement. In Diosi's approach, in which the mass density operator has to be smeared, the solid's microscopic mass distribution plays no role. The results are applied to a special single-photon avalanche photodiode detector, which interacts as little as possible with its environment. This is realised by disconnecting the detector from the measurement devices when it is in a superposition, and by biasing the photodiode by a plate capacitor, which is charged shortly before the photon's arrival. For a suitable choice of components, the detector can stay in a superposition for seconds; its lifetime can be shortened to microseconds with the help of a piezoactuator, which displaces a mass in the case of photon detection.
For special single-photon detectors that are isolated from their environment during detection (so-called indirect detectors), it is investigated how long they stay in a superposition of a photon-detected and a no-photon-detected state according to the Diósi–Penrose criterion for wavefunction collapse. To suppress interactions with the environment during detection, the avalanche photodiodes of the indirect detectors are biased using plate capacitors rather than conventional voltage sources, and the detection outcome is read out a sufficient time after the superposition in the detector has reduced. For the analysis, the Diósi–Penrose criterion is applied to solids in quantum superpositions that are slightly displaced relative to each other or have slightly different expansions in the superposed states, where both the parameter-free Diósi–Penrose model and Diósi’s version, in which the microscopic mass distribution is spatially averaged, are discussed. It is shown that indirect single-photon detectors can be constructed in such a way that they remain in superposition for seconds. It is proposed to use indirect detectors for the generation of mirror superpositions with the help of piezo-actuators, where the superposed mirror can have a displacement of about 50 Å for approximately half a microsecond. Even though the superposed mirror states generated in this way are decoherent superpositions (improper mixtures) and therefore cannot be detected by conventional methods, their generation opens new perspectives for probing wavefunction collapse.
In the Diósi–Penrose (DP) model a superposition of two mass distributions decays at the rate E_G/ħ. Diósi's master equation uses the mass-density operator smeared over a length R0; Penrose's formulation uses the density of the stationary state, and the "parameter-free" choice R0 = u_rms (the zero-point amplitude) links the two. This preprint examines what each choice implies for spontaneous heating and for collapse rates, and states separately which results are standard and which are new. Main results:• Heating per unit mass is 2πGħ∫g², i.e. Għ/(4√π σxσyσz) for Gaussian smearing of per-axis widths σi. With R0 equal to the per-axis zero-point amplitude, Diósi's functional reproduces Penrose's E_G for displacements smaller than the lattice spacing.• For a crystal ball, E_G splits exactly into a continuum term and a per-atom granular term. The continuum term is already contained in the per-atom term (the gravitational analogue of the Lorentz local field), the granular term is lattice periodic, and it carries a Madelung reduction of 0.90 (Cu) and 0.29 (⁴He).• Copper is predicted to heat at 12.1–12.8 pW/kg. This is in mild tension with the 10 pW/kg figure adopted after background subtraction from the Bayreuth heat leak.• The published Debye–Waller values of hcp ⁴He follow a convention in which the reported ⟨u²⟩ is half the one-dimensional mean-square displacement. One direct cross-check and four consistency checks support this reading. With it, the solid-helium prediction becomes 6–8 fW/kg instead of 21 fW/kg.• For any liquid (⁴He or ³He) the one-body density is uniform, so Penrose's granular E_G vanishes. The solid/liquid ⁴He collapse-rate ratio is ≈6 for d ≪ u, 2.8 at 0.2 nm and 1.15 at 1 nm, which quantifies a conjecture of Diósi (2013).• Heating under Penrose's prescription depends on the dynamical completion. For every completion that splits ⟨ρ⟩ into non-negative pieces, the liquid heats at most 2πGħn = 1.15 fW/kg; maximal localization then gives a liquid/solid ratio of 0.155. Density-matrix and configuration-based completions give anything from ~10⁻²⁶ to order one.• Experiment: – Ionizing radiation deposits nearly the same power per kilogram in every material and therefore mimics the fixed-R0 signal. – Underground at LNGS, unshielded environmental gammas still deposit 0.6–8 pW/kg, so ≥20 cm of lead is needed. – The nearest-term test of the zero-point prescription is to compare the heat leaks of heavy, stiff metals with copper; tungsten is predicted at ≈77 pW/kg, six times copper. – Underground helium calorimetry at 1–0.1 pW/kg would test colored fixed-R0 models up to R0 ≈ 10–21 pm, provided the cell-wall heat release can be subtracted to 5–0.5%.
Version 4 (October 2026), interim correction: an independent review found that the main result is a reformulation rather than a recovery. Both inputs to the budget-saturation condition, the superposition cost and the budget B = ħ/τ, are posited, so its agreement with the Penrose–Diósi criterion holds by construction. The uniform-sphere coefficient in the testable prediction is off by a factor of 6/5, and the tabulated collapse times use a small-displacement formula outside its range. These results should not be cited until the revised version is posted. Details are in the Revision History of the PDF.We show that the Penrose–Diósi gravitational collapse criterion — which predicts that quantum superpositions decay on a timescale τ = ℏ/E_G, where E_G is the gravitational self-energy of the difference mass distribution — arises as the budget-saturation condition of the selective reconstruction framework (Russell 2026a). When the reconstruction budget B is identified with ℏ/τ_local via the Margolus–Levitin theorem, the Russell constraint C_super ≤ B becomes the Penrose–Diósi inequality E_G ≤ ℏ/τ. "Observation" is thereby reframed not as a primitive physical event but as the condition under which the gravitational self-energy of a superposition exhausts the geometric reconstruction budget of the boundary observer. The result is observer-dependent and recovers relational quantum mechanics as a consequence of resource constraints. A falsifiable, mass-scaling prediction (τ ∝ M⁻² d⁻² R³) is derived for levitated-nanosphere experiments. A structural isomorphism with Nanite's LOD scheduling algorithm is noted as a conceptual heuristic. Epistemic status: The budget identification is motivated by the Margolus–Levitin theorem but is not formally derived from AdS/CFT. This is a working paper inviting scrutiny, not an established result.v3 (2026-05-27): Format converted from HTML to LaTeX. §5 collapse-time table recomputed under the stated d=R, ρ=2200 kg/m³ convention (prior values were inconsistent with the formula by ~30 orders of magnitude). Reference 8 updated per consolidation of Virtualized Geometry into Spacetime as Optimal Allocation. Minor text corrections: sub-femtokelvin → sub-microkelvin, Verlinde (2010) → (2011), Stanford → ETH Zurich. Figures regenerated with layout fixes (no content changes). ORCID, email, and concept DOI added to front matter.
Abstract The possibility that gravity plays a role in the collapse of the quantum wave function has been considered in the literature, and it is of relevance not only because it would provide a solution to the measurement problem in quantum theory, but also because it would give a new and unexpected twist to the search for a unified theory of quantum and gravitational phenomena, possibly overcoming the current impasse. The Diósi–Penrose model is the most popular incarnation of this idea. It predicts a progressive breakdown of quantum superpositions when the mass of the system increases; as such, it is susceptible to experimental verification. Current experiments set a lower bound R 0 ≳ 4 Å for the free parameter of the model, excluding some versions of it. In this work we search for an upper bound, coming from the request that the collapse is effective enough to guarantee classicality at the macroscopic scale: we find out that not all macroscopic systems collapse effectively. If one relaxes this request, a reasonable (although to some degree arbitrary) bound is found to be: R 0 ≲ 10 6 Å. This will serve to better direct future experiments to further test the model.
Single-photon detectors have become more important with the advent of set-ups for optical communication using single-photon pulses, mainly quantum key distribution. The performance of quantum key distribution systems depends strongly on the performance of single-photon detectors. In this paper, aiming to overcome the afterpulsing that limits strongly the maximal transmission rate of quantum key distribution systems, three smart strategies for single-photon detection are discussed using analytical and numerical procedures. The three strategies are: hold-off time conditioned to avalanche presence, termed the Norwegian strategy, using one avalanche photodiode, using two raffled avalanche photodiodes and using two switched avalanche photodiodes. Finally we give examples using these strategies in a quantum key distribution set-up.
Significant — Diósi–Penrose Gravitational Collapse Under Universal Containment: Time Position Rules, Mass–Gravity Formation, and the Moving S = 0 Crossover — Presents a containment-based response to gravitational collapse, placing competing mass configurations under common Time Position Rules. The proposed cycle connects stationary gravitational memory, passage of the moving S = 0 window, Mass–Gravity formation, and subsequent photon-carried return through the true-zero door to future placement. Physical state reduction, environmental decoherence, photon transport, and return certification receive distinct roles. A worked stationary-sphere benchmark calculates gravitational difference-energy, waiting times, and outcome probabilities using the Diósi–Penrose rate and an explicitly assumed stochastic state-selection rule. Eight proposed tests address memory stationarity, branch comparison, outcome selection, readout controls, transport history, and structural consistency. The article specifies the additional dynamics, measurable gravitational-memory observables, and radiation predictions required to complete a native Mass–Gravity collapse theory.