Physical Sciences

Abstract: We present a fully quantum-mechanical investigation of synchronisation in two inductively coupled superconducting oscillators modelled as nonlinear rf-SQUID circuits. Unlike semiclassical or hybrid treatments, both SQUID degrees of freedom are evolved as a joint two-body wavefunction by solving the time-dependent Schrödinger equation (TDSE) using a split-operator spectral method. This enables direct access to coherent flux dynamics, entanglement generation, and quantum phase-space structure without introducing dissipation, measurement back-action, or classical approximations. By varying the mutual inductive coupling strength, we identify a transition from effectively desynchronised tunnelling to quasi-periodic phase locking and, at stronger coupling, chaos-assisted synchronised tunnelling. Synchronisation is quantified using three complementary diagnostics: expectation-value locking of the flux variables ϕ_i(t), von Neumann entanglement entropy S(t), and Husimi phase-space distributions Q(ϕ,p). The results show that coherent quantum synchronisation can emerge solely from Hamiltonian evolution, with entanglement acting as a dynamical correlation channel rather than simply reaching a maximal value. At moderate coupling, bounded entropy oscillations accompany stable phase locking, while stronger coupling produces broadened Husimi structures and irregular but correlated flux dynamics characteristic of chaos-assisted coherence. These findings establish coupled SQUID oscillators as a physically relevant platform for studying Hamiltonian quantum synchronisation, entanglement-mediated phase control, and nonlinear quantum transport. The work also suggests possible routes towards synchronisation-based control in superconducting qubit networks, quantum metrology, and coherent neuromorphic superconducting architectures where dissipation is deliberately minimised.

Abstract: A smooth window function $\mathit{\Diamond}(x) \in [0,1]$ that restricts a field-theory action to a finite spacetime domain generates a common conservation structure across diverse experimentally realized finite-time quantum phenomena. Applying the windowed action principle yields windowed Noether identities of the form $\partial_{\mu}(\mathit{\Diamond}J^{\mu}) = 0$: exact conservation of the windowed current, with apparent non-conservation of local currents confined to the boundary layer where $\partial_{\mu}\mathit{\Diamond} \neq 0$. This boundary-layer structure is mathematically identical to open-system flux terms in decoherence theory. The formalism is applied to five experimentally established settings: the timelike Unruh effect in trapped-ion detectors, the dynamical Casimir effect in superconducting circuits, quench-induced currents in cold-atom systems, ultrafast coherent control with femtosecond laser pulses, and finite-time scattering theory. In each case the experimentally specified control window---switching function, drive envelope, quench ramp, pulse envelope, or scattering window---is shown to be an instance of the same formal object $ mathit{\Diamond}$, and the windowed Noether identity is derived for each setting in this unified form for the first time. Two results are new: the cross-case identification of all five control functions as instances of $\mathit{\Diamond}$ under a single formalism, and the formal consequence that identical Hamiltonians instantiated over different temporal domains generically produce inequivalent unitary evolutions, something not previously recognized as a structural consequence of domain restriction.

Abstract: High-dimensional quantum entanglement realized with orbital-angular-momentum (OAM) modes of photons provides a powerful platform for exploring the topology and geometry of quantum state spaces. Recent experiments using spontaneous parametric down-conversion have demonstrated entangled photon pairs occupying a seven-dimensional OAM Hilbert space whose topology is governed by the Lie group , giving rise to a 48-dimensional manifold of quantum states. In this work, we propose a geometric interpretation of this structure based on octonion algebra. The seven OAM basis modes are mapped onto the seven imaginary units of the octonions, whose multiplication rules are encoded by the Fano plane. Within this framework, nonlinear three-wave interactions that underlie photon-pair generation naturally correspond to cyclic triples in the Fano-plane geometry. This correspondence suggests that the observed topological structure of high-dimensional entangled photon states may admit an octonionic geometric description, providing a potential bridge between structured-light quantum optics and exceptional algebraic structures.

Abstract: In all-Josephson-junction (all-JJ) logic, cell area is determined by the size of Josephson junctions, enabling intrinsically compact layouts. Tunable kinetic inductance offers a route to add circuit reconfigurability, pushing further scaling within the same all-JJ framework. In this work we present a set of basic cells for reconfigurable superconducting “kinemonics” that exploit tunable kinetic inductances of a multi-layer nanostructure to realise multiple logic functions within a single compact circuit. We then combine these gates into a universal programmable logic cell consisting of only four reconfigurable gates supplemented by a single tunable kinetic-inductance key and demonstrate that it can realise all sixteen two-input Boolean functions, making it an analogue of a look-up table with in-hardware reconfigurability. We also discuss how the same principle can be used in superconducting neuromorphic circuits, where tunable kinetic inductance controls routing, coincidence detection, inhibition, and delay for soliton-like spikes in neuron-like elements.

Abstract: We investigate the dynamics of a driven quantum field coupled to a finite-temperature reservoir. The corresponding master equation is solved using superoperator techniques, yielding an analytical expression for the density operator. To obtain a compact and physically transparent description of the dynamics, we adopt a phase-space representation based on the Husimi Q-function. For an initially coherent state, we derive a closed-form Gaussian expression for the Husimi Q-function whose stationary limit corresponds to a displaced thermal state. This approach also enables an analytical study of quantum-interference dynamics for an initial superposition of coherent states. Furthermore, we derive the corresponding Fokker–Planck equation for the Husimi Q-function and obtain closed-form expressions for relevant statistical quantities, including the mean photon number, the photon-number standard deviation, and the Mandel parameter. We also investigate the Wehrl and linear entropies, which quantify the loss of phase-space information and purity induced by the thermal environment. The framework provides a complete analytical characterization of the phase-space dynamics, photon statistics, and entropic properties of driven–dissipative quantum fields while avoiding the explicit manipulation of the density operator.

Abstract: Quantum metrology exploits quantum states to achieve estimation sensitivity beyond classical limits. In the continuous-variable (CV) regime, the squeezed state has been used to implement deterministic quantum sensing. However, the quantum metrology sensitivity of the squeezed state is significantly affected by losses or detection inefficiencies, which restrict its applications. In this work, quantum distributed sensing is proposed using optical parametric amplified multi-mode entanglement generated from squeezed states. It is found that the sensitivity is robust to loss or detection inefficiency with introduction of optical parametric amplification (OPA), where a two-mode Einstein-Podolsky-Rosen entangled state and a four-mode cluster state are exploited for analysis. The quantum information matrix is calculated for two-mode squeezed state to obtain the optimal bound in comparison with our scheme. It is found that with sufficient OPA gain, the overall sensitivity is robust across a wide range of loss values. This work provides a method for realizing large-scale quantum metrology in real-world applications despite losses or detection inefficiencies.

Abstract: Entanglement swapping is not only one of the core resources of quantum information processing, but also the backbone of long-distance quantum communication and quantum networks. Naturally, quantum information processing schemes based on entanglement swapping, such as quantum cryptography protocols and quantum algorithms, are more adaptable to quantum network environments. In this paper, we achieve quantum anonymous computation through entanglement swapping, the basic idea of which comes from our previous work [2019, Quantum Information Processing, 18(6), 168]. We propose two quantum anonymous computation protocols, in which entanglement swapping plays a crucial role in transmitting information and enhancing information security.

Abstract: Quantum uncertainty and wavefunction collapse remain among the most conceptually unresolved aspects of microscopic physics. Here, we investigate whether uncertainty and collapse-like electron localization may admit a complementary thermodynamic interpretation through recursive entropy-field dynamics. The electron is modeled as a dynamically evolving entropy field–geometry composed of structural, electromagnetic, and thermal entropy components maintained through continuous recursive interaction with the surrounding vacuum entropy field. Within this framework, uncertainty emerges from incomplete temporal accessibility to rapidly evolving recursive electron configurations occurring beneath experimentally accessible measurement timescales. Repeated recursive phase sampling naturally produces probabilistic measurement behavior and approximately Gaussian localization statistics. Electron–photon interaction is further modeled through phase-matched recursive entropy coupling, where repeated entropy transfer progressively reorganizes the electron entropy geometry toward localization. Numerical simulations reproduce finite-width Dirac-delta–like localization behavior, finite collapse thresholds, and nonzero collapse timescales, suggesting that wavefunction collapse may emerge as a finite recursive thermodynamic process rather than instantaneous projection. The framework further suggests that localization saturation may naturally redirect subsequent entropy transfer toward electron motion, scattering, and orbital restructuring.

Abstract: Two features of fundamental physics are normally taken as brute postulates: that the spacetime metric is four-dimensional with Lorentzian signature, and that matter obeys the Dirac equation. We obtain both from a single definition, which we introduce: that of an observer-bearing spacetime. A spacetime is observer-bearing if some frame within it admits a positive-definite probability density—read along an observer's direction—together with a conserved vector current; that is, if it can carry a readable, conserved probability at all. The "observer'' here is algebraic, a direction of positive-definite conserved current, not a physical organism. For this criterion to have force, the amplitude must be a multivector in the Clifford algebra of the tangent space, rather than the usual complex amplitude; the two are isomorphic in 3+1 dimensions but diverge in others, and that divergence is the source of the selection. To recover the dynamics, we then ask for the information-preserving transport of the conserved current—the flow that produces no net entropy. The result is the Dirac equation, in which the relativistic mass term emerges automatically as the constraint that makes the flow entropic, the mass appearing as its Lagrange multiplier. We distinguish this from anthropic (Tegmark) and orbital-stability (Ehrenfest–Tangherlini) accounts of dimensionality, and from Fisher-information (Frieden) and quantum-cellular-automaton (D'Ariano–Perinotti) reconstructions of the Dirac equation.

Abstract: Quantum mechanics is characterized by several distinctive features: (1) wave–particle duality, (2) the uncertainty principle, (3) superposition of states, (4) wave function collapse, (5) the tunneling effect, (6) quantum entanglement, and (7) the dominance of probability. Proposed interpretations include the Copenhagen interpretation, the de Broglie–Bohm pilot-wave theory, and the many-worlds interpretation. Despite sustained debate, no unified consensus has emerged. A central obstacle may lie in the unresolved ambiguity over whether a quantum entity is fundamentally a wave or a particle. Although photons and electrons exhibit wave-like and particle-like properties, the concepts of “wave” and “particle” are inherently mutually exclusive. This paper proposes that the true nature of a quantum is a quantized wave interacting at a single spatial point. Based on this premise, the study investigates the vacuum structure and interactions, together with the relationship between wave function collapse and the conservation of physical quantities. The mechanisms underlying the photoelectric effect and quantum tunneling are reexamined, along with the double-slit and delayed-choice quantum eraser experiments. By treating photons and electrons as quantized waves confined to point interactions, this work demonstrates that puzzling quantum behaviors, long considered obstacles to a coherent understanding of quantum mechanics, admit straightforward explanations.

Abstract: Two foundational problems afflict our description of gravity: ultraviolet divergences in its quantum formulation and a curvature singularity at the Big Bang in its classical one. Both are addressed here by imposing a single kinematic restriction — a Planck-scale mode cutoff on the temporal frequency in conformal time, |k| ≤ ℓₚ⁻¹, on a massless spin-2 field propagating in a structureless void — and deriving its consequences. For the radiation-dominated FLRW case this is equivalent to restricting the spatial momentum magnitude to sub-Planckian values in the comoving frame. The band-limited projection of the singular scale factor a(η) = |η|/ℓₚ yields the closed-form entire function aᴿᵉᶢ(η) = (2/π)[(η/ℓₚ) Si(η/ℓₚ) + cos(η/ℓₚ)], with strictly positive global minimum aᴿᵉᶢ(0) = 2/π and Kretschmann scalar Kᴿᵉᶢ(0) = (3/4)π⁴ℓₚ⁻⁴ ≈ 73.06 ℓₚ⁻⁴; both are parameter-free. The classical Big Bang singularity is replaced by a smooth bounce whose properties are fixed by ℓₚ alone. Two formal results follow from the same restriction: the Deser bootstrap produces the Einstein–Hilbert action within the restricted field space, and all graviton loop integrals are finite by power counting. A companion paper [34] addresses the gauge-consistency question on which both rest, proving an exact one-loop transverse-traceless Ward identity at all sub-Planckian momenta, bounding the deviation from general relativity by a measured function f(k) ≈ k/Mₚ that is of order 10⁻⁶⁰ at cosmological scales, and quantifying the residual Planck-scale breaking of nonlinear diffeomorphism invariance as a prediction rather than an inconsistency. The regulated metric satisfies the projected Einstein equations with a geometry-derived effective stress-energy that recovers radiation asymptotically; the consistency check is given in Section 5.5.

Abstract: Linear Dichroism (LD) optical absorption spectroscopy historically has had substantial but limited application in various domains of science. In particular, full-tensor reconstruction has been tedious and difficult, usually requiring extensive measurements on single crystals at many orientations using a four-circle goniometer. As a consequence it is very seldom done. Here we propose, and test by numerical simulation, a simple, novel method of determining the full dipole optical absorption tensor of homogeneous planar films in real-time as a function of energy (or wavelength), while requiring only minimal additional time and instrumentation. The full-tensor spectrum, after construction from the experimental data, allows one to instantly calculate the absorption for any selected polarization direction, even those that are physically inaccessible to experimental measurement. Although our specific application in this paper is to X-ray Absorption Fine Structure Spectroscopy, the method should be adaptable to UV-Vis, IR, THz, microwave, and other wavelengths. A strength of this measurement modality is that full tensor data can be acquired using essentially the same sort of scanning geometry that is normally used for XAFS, with only a one discrete shift in spin axis orientation between groups of scans. The additional instrumentation needed to determine the five Fourier components of the signal at each energy is minimal; two angles gives up to ten parameters, while six are needed, and the others can be put to good use. Outside of XAFS, FTMAS also should be applicable to diverse scientific and technological areas such as oriented bio-molecular films, semiconductor and materials physics, and process control of thin-film photovoltaics and semiconductors.

Abstract: Quantum entanglement produces nonlocal correlations for which no local dynamical account is known. In Ref.~\cite{PRR} we proposed that these correlations are mediated through an extra temporal dimension and introduced a $(3,2)$-dimensional spacetime framework on a phenomenological basis; the present paper derives that framework from the bulk geometry. A single extra spatial dimension admits no effective superluminal shortcut on the brane, this rules it out as a candidate mediator and motivates the extra-time setting. Within the warped-product metric ansatz the five-dimensional vacuum Einstein equations fix the warp factor uniquely, leaving no freedom in the geometry once $\mathbb{Z}_2$ symmetry is imposed. A massless bulk field $\mathscr{X}_a(\mathbf{x},t,\tau)$, sourced on the brane by the preparation event and by the measurement interactions, propagates causally through the extra-time dimension; equal-time correlations at arbitrarily large brane separation arise via the $E=0$ null geodesic family, without admitting controllable superluminal signaling. The propagation time and crossed ratios of Ref.~\cite{PRR}, previously postulated, emerge here from the null geodesic kinematics. The Bohm--Bub collapse framework is extended to a bipartite entangled system by replacing the abstract hidden vector with the brane-projected bulk field $\mathscr{X}_a$. At fixed contextual microstate $\lambda$ collapse is deterministic; Born statistics follow upon averaging over an equivariant ensemble. When the framework is extended to two independent Bell pairs, the bulk field sourced by one pair reaches the detectors of the other and induces a cross-pair correlation scaling as the square of the intra-pair to inter-pair separation ratio, a concrete falsifiable prediction with no counterpart in standard quantum mechanics, accessible with existing photonic Bell-test technology.

Abstract: Despite the tremendous progress of quantum physics, there is a widespread belief that something is missing in our knowledge. A belief that maybe the answer is not in more abstractions, extra dimensions, or higher mathematics. I suggest we reexamine our foundational assumptions. First off, mechanics – classical or quantum – assumes a reality of existing objects in space bearing properties, including kinetic energy (KE). Fudges to “existing” (being massless or mathematical) and to “space” (e.g., Hilbert) have only taken us so far. I submit that the essence of radiation (the photon) is immaterial occurrence. Why do we force it to obey a model (mechanics) based on existing constituents? Second, I contend that quantum pioneers were too quick to accept – and we have been too lazy/busy to question – the equivalence of photon momentum with rest mass momentum. We actually don’t understand momentum.

Abstract: Quantum tunneling is conventionally described using the stationary Schrödinger equation with an externally imposed potential barrier. In this work, we present a dynamical formulation of quantum tunneling in which the barrier is modeled as a structured medium possessing quantized internal modes that interact coherently with an incident electron. Using the Heisenberg operator formalism and a second-quantized representation of the barrier medium, we derive coupled dynamical equations governing the electron–barrier interaction. Under a continuum-mode and mean-field approximation, the collective response of the barrier modes generates an effective potential that reproduces the conventional rectangular barrier model and the standard tunneling transmission probability obtained from the Schrödinger equation. Within this framework, a tunneling traversal time is naturally defined from the dynamical evolution of the electron and is shown to depend on the barrier width, barrier height, and incident electron energy. Numerical simulations illustrating the transmission probability and tunneling-time behavior are presented. The results provide a complementary microscopic interpretation of tunneling processes in structured quantum media and may be relevant to nanoscale transport, photonic barriers, and coherent quantum devices.

Abstract: The standard interpretation of quantum measurement on entangled systems holds that measuring one particle nonlocally collapses the wavefunction of its spacelike-separated partner. We argue that this conclusion rests on a false presupposition: that subsystems of entangled systems possess independent ontic states. If the global wavefunction is the sole ontic object (ψ-ontic holism), then for entangled systems there is no “state of B” to be affected by measurement at A. The reduced density matrix of a subsystem, while operationally useful, is not ontologically real for non-factorizable states. Measurement is a local dynamical process — concretely modeled by continuous spontaneous localization (CSL) — that destroys one local wavefunction component at the measurement site. The global state factorizes as a consequence, and subsystem ontology emerges for the first time. The transition of the distant particle’s reduced density matrix from mixed to pure reflects this emergence of separability, not a physical change at the distant location. We show that this framework is consistent with no-signaling, with the contextuality required by the Kochen–Specker and GHZ theorems, and with the local measurement axiom (Postulate M) proposed in a companion paper. Bell’s theorem does not force nonlocality upon our framework because it presupposes outcome determinism — the assignment of definite values to observables prior to measurement — which several quantum mechanical theorems and our ψ-ontic ontology explicitly deny. Decoherence, which is ubiquitous in nature, provides the mechanism by which the global wavefunction factorizes and classical separability emerges. The apparent nonlocality of quantum mechanics is thus reinterpreted as nonseparability: the fundamental ontology is holistic, but the dynamics are local.

Abstract: The standard measurement postulate of quantum mechanics stipulates an instantaneous, non-local update of the global wavefunction upon measurement of an entangled subsystem. This postulate has been a persistent source of foundational tension, both with the locality structure of relativistic physics and with the dynamical character of the decoherence program. We separate the measurement postulate into three logically independent claims: definite outcome realization, Born-rule probability assignment, and instantaneous projection for the global wavefunction. We argue that the third claim can be eliminated at the axiomatic level and propose a modified measurement postulate, Postulate M, that replaces it. Under Postulate M, a single pointer outcome is realized locally when environmental decoherence has einselected a pointer basis at the measurement site; the corresponding selection acts on the global wavefunction as a conditional restriction to a branch rather than as a physical operation on spacelike-separated regions. We show that Postulate M recovers the standard measurement postulate as a limiting idealization for vanishing decoherence time, derives Lüders’ rule for sequential measurements, and yields no-signaling as an automatic structural consequence — not only at the level of measurement statistics but at the level of physical states themselves. Two explicit illustrations in the EPR scenario — with one and with both particles coupled to local spin environments — demonstrate the framework concretely and exhibit its frame-independent, manifestly local character. The framework is built on standard decoherence theory, compatible with multiple candidate mechanisms for single-outcome realization including gravitationally-induced collapse proposals, and naturally situated within a ψ-ontic reading of the quantum state. It represents, we argue, a reformulation of quantum mechanics as a local, state-realist theory — preserving Einstein’s aspiration for an objective physical world in the only form consistent with the empirical content of quantum mechanics, namely realism about the wavefunction rather than about pre-measurement observable values.

Abstract: This manuscript develops a quantum-mechanical foundations reading of the coarse-grained state as a persistent timelike process. The central claim is that a coarse-grained state should not be interpreted as a halted microscopic configuration. It is a stable reference process whose internal contribution structure remains active while its accessible readout appears persistent. The phrase “silence speaks volumes” is used in a controlled double sense: silence denotes the pre-record situation in which no displayed answer is yet available, while volumes denote stored, structured, and repeatedly readable boundary content. Quantum effects are then read as uncertainty-limited deviations and alternatives relative to the coarse-grained reference state. Interference suppresses non-stationary alternatives, while decoherence stabilizes the accessible record of the coarse-grained state. A short self-reference discussion connects the construction to the logical issue raised by Gödel, Turing, and Russell without claiming that physical measurement solves incompleteness, undecidability, or paradox. The manuscript remains within quantum-mechanical foundations. It proposes a local assignment and readout hierarchy: coarse-grained reference, silent non-displayed content, cut-local difference, stationary remainder, decohered record, and classical readout.

Abstract: The original Bell inequalities were derived with four terms of channel-to-channel correlations of paired photons but are violated with sixteen terms of channel-to-channel correlations. The same correlation function can be derived for non-entangled photons as it was for entangled ones. The correlation probability for independent photons and qubits exceeds that of the entangled photons. Entanglement reduces the detection probability of the first measurement to 1/2 but does not affect the second photon’s maximal probability of detection. For one channel-to-one channel correlation, the quantum probability of entangled photons can be factorized, which should enable a local determination of a quantum nonlocal effect. A single photon is scattered by the quantum Rayleigh scattering making it impossible to synchronize the detections of an original pair of photons. All experimental results can be explained by means of the intrinsic field of photons as confirmed by independently published experimental results involving independent photons.

Abstract: We propose a novel interpretation of quantum mechanics in which microscopic particles possess definite positions, momenta, and spins at every moment, independent of measurement. These physical quantities are not determined by hidden variables but are randomly realized according to the wave function’s probability distribution. Measurement outcomes reflect the particle’s actual state rather than a wave-function collapse. By treating the measured and measuring systems as a single composite system, we introduce a conditional probability decomposition of the wave function that preserves interference without invoking instantaneous collapse. Potential experimental tests of the conditional probability decomposition are discussed. This framework provides a coherent understanding of quantum measurement, nonlocal correlations, and the EPR paradox, while remaining consistent with all standard quantum predictions including Bell inequality violations and GHZ state.