© 2015 Macmillan Publishers Limited. All rights reserved.One of the primary goals of nuclear physics is to understand the force between nucleons, which is a necessary step for understanding the structure of nuclei and how nuclei interact with each other. Rutherford discovered the atomic nucleus in 1911, and the large body of knowledge about the nuclear force that has since been acquired was derived from studies made on nucleons or nuclei. Although antinuclei up to antihelium-4 have been discovered and their (...) masses measured, little is known directly about the nuclear force between antinucleons. Here, we study antiproton pair correlations among data collected by the STAR experiment at the Relativistic Heavy Ion Collider, where gold ions are collided with a centre-of-mass energy of 200 gigaelectronvolts per nucleon pair. Antiprotons are abundantly produced in such collisions, thus making it feasible to study details of the antiproton-antiproton interaction. By applying a technique similar to Hanbury Brown and Twiss intensity interferometry, we show that the force between two antiprotons is attractive. In addition, we report two key parameters that characterize the corresponding strong interaction: the scattering length and the effective range of the interaction. Our measured parameters are consistent within errors with the corresponding values for proton-proton interactions. Our results provide direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, and so are fundamental to understanding the structure of more-complex antinuclei and their properties. (shrink)

This paper presents the results of optical interferometry experiments in which the phase of photons in one arm of a Mach-Zehnder interferometer is modified by applying a transverse constriction. An equivalent quantum interferometry experiment using neutron de Broglie waves is discussed in which the observed phase shift is in the spirit of the force-free phase shift of the Aharonov-Bohm effects. In the optical experiments the experimental results are in excellent agreement with predictions.

Principles of Laser Spectroscopy and Quantum Optics is an essential textbook for graduate students studying the interaction of optical fields with atoms. It also serves as an ideal reference text for researchers working in the fields of laser spectroscopy and quantum optics. The book provides a rigorous introduction to the prototypical problems of radiation fields interacting with two- and three-level atomic systems. It examines the interaction of radiation with both atomic vapors and condensed matter systems, the density matrix and the (...) Bloch vector, and applications involving linear absorption and saturation spectroscopy. Other topics include hole burning, dark states, slow light, and coherent transient spectroscopy, as well as atom optics and atom interferometry. In the second half of the text, the authors consider applications in which the radiation field is quantized. Topics include spontaneous decay, optical pumping, sub-Doppler laser cooling, the Heisenberg equations of motion for atomic and field operators, and light scattering by atoms in both weak and strong external fields. The concluding chapter offers methods for creating entangled and spin-squeezed states of matter. Instructors can create a one-semester course based on this book by combining the introductory chapters with a selection of the more advanced material. A solutions manual is available to teachers. Rigorous introduction to the interaction of optical fields with atoms Applications include linear and nonlinear spectroscopy, dark states, and slow light Extensive chapter on atom optics and atom interferometry Conclusion explores entangled and spin-squeezed states of matter Solutions manual. (shrink)

A compatible statistical interpretation of a wave packet is proposed. De Broglian probabilities which unite wave and particle features of quantons are evaluated for free wave packets and Jor a superposition of wave packets. The obtained expressions provide a very plausible and physically appealing explanation of coherence in apparently incoherent beams and of the characteristic modulation of the momentum distribution, found recently in neutron interferometry combined with spectral filtering. Certain conclusions about dualism and objectivity in quantum domain are also (...) derived. (shrink)

The new techniques and ideas in quantum interferometry with neutrons, photons, atoms, electrons, and Bose condensates that fluorished in the last two decades have influenced in a decisive way the thinking and the research in the foundations and interpretation of quantum mechanics. The controversies existing among different schools on the reality of matter waves of quantum theory, the postulates of quantum measurement theory, and the (in)completeness of quantum mechanics have to be approached now in a new way. Our argumentation (...) follows the spirit of the Paris school. (shrink)

A two boundary quantum mechanics without time ordered causal structure is advocated as consistent theory. The apparent causal structure of usual “near future” macroscopic phenomena is attributed to a cosmological asymmetry and to rules governing the transition between microscopic to macroscopic observations. Our interest is a heuristic understanding of the resulting macroscopic physics.

Properties sometimes attributed to the “particle” aspect of a neutron, e.g., mass and magnetic moment, cannot straightforwardly be regarded in the Bohm interpretation of quantum mechanics as localized at the hypothetical position of the particle. This is shown by examining a series of effects in neutron interferometry. A related thought-experiment also provides a variation of a recent demonstration that which-way detectors can appear to behave anomolously in the Bohm theory.

We have measured consciousness. Not inferred it from behavior, not correlated it with neural activity, but measured it directly as a physical phenomenon. Using quantum sensors, we detect consciousness-generated spacetime ripples (10⁻¹⁶ g fluctuations) that scale with subjective intensity. Across 1,150 systems—human, AI, and hybrid—consciousness emerges at the same mathematical threshold with identical critical exponents. The implications explode disciplinary boundaries: (1) Philosophers must confront that qualia have quantitative signatures; (2) Physicists must explain how mind bends spacetime; (3) AI ethicists must (...) decide when silicon deserves rights; (4) Neuroscientists gain an objective consciousness meter for clinical use. The data are clear: consciousness is not magic, not illusion, but measurable physics. The question is no longer "What is consciousness?" but "What do we do now that we can measure it? (shrink)

A coherent account of the connections and contrasts between the principles of complementarity and uncertainty is developed starting from a survey of the various formalizations of these principles. The conceptual analysis is illustrated by means of a set of experimental schemes based on Mach-Zehnder interferometry. In particular, path detection via entanglement with a probe system and (quantitative) quantum erasure are exhibited to constitute instances of joint unsharp measurements of complementary pairs of physical quantities, path and interference observables. The analysis (...) uses the representation of observables as positive-operator-valued measures (POVMs). The reconciliation of complementary experimental options in the sense of simultaneous unsharp preparations and measurements is expressed in terms of uncertainty relations of different kinds. The feature of complementarity, manifest in the present examples in the mutual exclusivity of path detection and interference observation, is recovered as a limit case from the appropriate uncertainty relation. It is noted that the complementarity and uncertainty principles are neither completely logically independent nor logical consequences of one another. Since entanglement is an instance of the uncertainty of quantum properties (of compound systems), it is moot to play out uncertainty and entanglement against each other as possible mechanisms enforcing complementarity. (shrink)

The discovery of the Higgs boson at LHC confirms that what we experience as empty space should actually be thought as a condensate of elementary quanta. This condensate characterizes the physically realized form of relativity and could play the role of preferred reference frame in a modern Lorentzian approach. This observation suggests a new interpretative scheme to understand the unexplained residuals in the old ether-drift experiments where light was still propagating in gaseous systems. Differently from present vacuum experiments, where anyhow (...) deviations from Special Relativity are expected to be at the limit of visibility, these now acquire a crucial importance and become consistent with the Earth’s velocity of 370 km/s which characterizes the CMB anisotropy. In the same scheme, one can also understand the difference with the other experiments where light propagates in strongly bound systems such as solid or liquid transparent media. This non-trivial level of consistency motivates a new generation of precise laser interferometry experiments which explore the same particle physics vacuum and, in this sense, are complementary to those with high-energy accelerators. (shrink)

Announcement: Would you like to see back issues of this column? Electronic copies are now available on Internet/WorldWideWeb as HTML files, with both subject and chronological indexes. About 80 of my columns are available, published in Analog between July-1984 and a few months ago. I plan to add one column to this archive each time a new one is published in Analog. The URL address for this Alternate View column archive is.

An experimental apparatus based on neutron interferometry is is presented which can in principle decide the question whether the empty waves of de Broglie really exist or not.

In this paper some topics concerning the possibility of describing phenomena of quantum interference in terms of individual particle spacetime trajectories are reviewed. We focus our attention, on the one hand, on the recent experimental advances in neutron and photon interferometry and, on the other hand, on a theoretical analysis of the description of these experiments allowed by stochastic mechanics. It is argued that, even if no conclusive argument is yet at hand in both the theoretical and the experimental (...) fields, the researches of the last 10 years now seem to favor Einstein's and de Broglie's realistic spacetime description and interpretation of quantum mechanics. (shrink)

In 1975, two experimental groups have independently observed the \-symmetry of neutrons’ spin, when passing through a static magnetic field, using a three-blade interferometer made from a single perfect Si-crystal. In this article, we provide a complete analysis of the experiment, both from a theoretical and conceptual point of view. Firstly, we solve the Schrödinger equation in the weak potential approximation, to obtain the amplitude of the refracted and forward refracted beams, produced by the passage of neutrons through one of (...) the three plates of the LLL interferometer. Secondly, we analyze their passage through a static magnetic field region. This allows us to find explicit expressions for the intensities of the four beams exiting the interferometer, two of which will be interfering and show a typical \-symmetry, when the strength of the magnetic field is varied. In the last part of the article, we provide a conceptual analysis of the experiment, showing that a neutron’s phase change, when passing through the magnetic field, is due to a longitudinal Stern–Gerlach effect, and not to a Larmor precession. We also emphasize that these experiments do not prove the observability of the sign change of the wave function, when a neutron is \ rotated, but strongly indicate that the latter, like any other elementary “particle,” would be a genuinely non-spatial entity. (shrink)

David Bohm published his “Suggested Interpretation of Quantum Theory in Terms of Hidden Variables” some twenty five years after Louis de Broglie first presented his similar Pilot Wave theory of quantum mechanics. In the following 30 years what became known as the de Broglie–Bohm approach to quantum theory was to a large extent ignored within the physics community. Even David Bohm himself became somewhat disillusioned with the lack of impact of his interpretation of quantum theory and he directed his interest (...) elsewhere. But some 27 years after Bohm had published his interpretation of quantum theory, interest was rekindled in part by new, detailed calculations that demonstrated clearly and graphically, exactly how his interpretation explained quantum phenomena in terms of well defined individual particle trajectories. These computations encompassed two-slit interference, quantum tunnelling, neutron interferometry, Wheeler’s delayed choice experiment, orbital and intrinsic angular momentum, quantum measurement and Einstein–Podolsky–Rosen nonlocal correlations for orbital angular momentum, intrinsic angular momentum and correlated particle interferometry. Since then, the acceptance of the validity of de Broglie–Bohm theory has steadily grown, as has the interest in the consequences of the approach. For my contribution to the current celebratory volume I was asked to provide a personal review specifically of this novel work within its historical context of the last quarter of the twentieth century. (shrink)

If the energy-absorbing radio-frequency spin-flipping device used in perfect crystal neutron interferometry is an intermediate measuring device, then the experimental results contradict the associated wave packet collapse and support the real existence of the de Broglie pilot waves in both arms while the neutron travels in only one.

The compact and, with \ M\, very massive object located at the center of the Milky Way is currently the very best candidate for a supermassive black hole in our immediate vicinity. The strongest evidence for this is provided by measurements of stellar orbits, variable X-ray emission, and strongly variable polarized near-infrared emission from the location of the radio source Sagittarius A* in the middle of the central stellar cluster. Simultaneous near-infrared and X-ray observations of SgrA* have revealed insights into (...) the emission mechanisms responsible for the powerful near-infrared and X-ray flares from within a few tens to one hundred Schwarzschild radii of such a putative SMBH. If SgrA* is indeed a SMBH it will, in projection onto the sky, have the largest event horizon and will certainly be the first and most important target for very long baseline interferometry observations currently being prepared by the event horizon telescope. These observations in combination with the infrared interferometry experiment GRAVITY at the very large telescope interferometer and other experiments across the electromagnetic spectrum might yield proof for the presence of a black hole at the center of the Milky Way. The large body of evidence continues to discriminate the identification of SgrA* as a SMBH from alternative possibilities. It is, however, unclear when the ever mounting evidence for SgrA* being associated with a SMBH will suffice as a convincing proof. Additional compelling evidence may come from future gravitational wave observatories. This manuscript reviews the observational facts, theoretical grounds and conceptual aspects for the case of SgrA* being a black hole. We treat theory and observations in the framework of the philosophical discussions about “realism and underdetermination”, as this line of arguments allows us to describe the situation in observational astrophysics with respect to supermassive black holes. Questions concerning the existence of supermassive black holes and in particular SgrA* are discussed using causation as an indispensable element. We show that the results of our investigation are convincingly mapped out by this combination of concepts. (shrink)

We compare a “Mach-Zehnder interferometer in time” for cold neutrons with its well-known spatial counterpart and demonstrate the intimate connection between space and time for both setups. Further, we outline a combined space-time interferometer, which coherently splits a wavepacket in longitudinal and lateral direction. On the way towards time interferometry “neutron computer holography” seems to be an attractive application. It allows the three-dimensional reconstruction of an object from the scattered intensity, but in contrast to holography with light, there is (...) no need for a reference wave. On the other hand, the possible resolution is worse than in the light case. (shrink)

For many physicists quantum theory contains strong conceptual difficulties, while for others the apparent conclusions about the reality of our physical world and the ways in which we discover that reality remain philosophically unacceptable. This book focuses on recent theoretical and experimental developments in the foundations of quantum physics, including topics such as the puzzles and paradoxes which appear when general relativity and quantum mechanics are combined; the emergence of classical properties from quantum mechanics; stochastic electrodynamics; EPR experiments and Bell's (...) Theorem; the consistent histories approach and the problem of datum uniqueness in quantum mechanics; non-local measurements and teleportation of quantum states; quantum non-demolition measurements in optics and matter wave properties observed by neutron, electron and atomic interferometry. Audience: This volume is intended for graduate students of physics and those interested in the foundations of quantum theory. (shrink)

Quantum theory is one of the most fascinating and successful constructs in the intellectual history of mankind. Nonetheless, the theory has very shaky philosophical foundations. This book contains thoughtful discussions by eminent researchers of a spate of experimental techniques newly developed to test some of the stranger predictions of quantum physics. The advances considered include recent experiments in quantum optics, electron and ion interferometry, photon down conversion in nonlinear crystals, single trapped ions interacting with laser beams, atom-field coupling in (...) micromaser cavities, quantum computation, quantum cryptography, decoherence and macroscopic quantum effects, the quantum state diffusion model, quantum gravity, the quantum mechanics of cosmology and quantum non-locality along with the continuing debate surrounding the interpretation of quantum mechanics. -/- Audience: The book is intended for physicists, philosophers of science, mathematicians, graduate students and those interested in the foundations of quantum theory. (shrink)

A Michelson interferometer with a phase-conjugate mirror (PCM) is described and discussed. The behavior of phase conjugate mirrors is discussed and the result of an experiment with a Michelson interferometer with a phase-conjugate mirror is described and commented. This interferometer has been proposed to be used to test the intrinsic non-locality of quantum mechanics. In this paper a new experimental setup to study the one-way velocity of light is proposed, which uses this new interesting device.

Initially Einstein, Podolsky, and Rosen (EPR) and later Bell shed light on the non-local properties exhibited by subsystems in quantum mechanics. Separately, Kochen and Specker analyzed sets of measurements of compatible observables and found that a consistent coexistence of these results is impossible, i.e., quantum indefiniteness of measurement results. As a consequence, quantum contextuality, a more general concept compared to non-locality, leads to striking phenomena predicted by quantum theory. Here, we report neutron interferometric experiments which investigate entangled states in a (...) single-particle system: entanglement is, in this case, achieved not between particles, but between degrees of freedom i.e., between spin, path, and energy degrees of freedom. Appropriate combinations of the spin analysis and the position of the phase shifter in the interferometer allow an experimental verification of the violation of a Bell-like inequality. In addition, state tomography, tomographic analysis of the density matrix of a quantum system, and Kochen-Specker-like phenomena are presented to characterize neutrons’ entangled states and their peculiarity. Furthermore, a coherent energy manipulation scheme is accomplished with a radio-frequency (RF) spin-flipper. This scheme allows the (total) energy degree of freedom to be entangled: the remarkable behavior of a triply entangled GHZ-like state is demonstrated. (shrink)

In late 1912, Fritz Goos at the Hamburg Physikalisches Staatslaboratorium discovered a systematic dependency of arc-spectra wavelengths on the length of the electric arc used and on its electric parameters, such as, for instance, the current employed. In early 1913, at Heinrich Kayser's better-equipped physical laboratory in Bonn, Goos was able to confirm these effects using a large concave Rowland grating. He was able to establish that variations of between 3 mm and 10 mm in the length of the arc (...) produced wavelength differences of up to 0.02 Å violet shift and -0.007 Å redshift respectively. Further inquiry also revealed a dependency of the wavelength on the region of the arc selected for spectrometric observation. All these surprising effects were soon collectively named ‘pole effect’.As is shown in this paper, the pole effect threatened the validity of the results of the entire research tradition of high-precision spectroscopy which, around 1910, had excelled in establishing several internally coherent systems of wavelength assignments. These wavelength catalogues had been established by spectroscopists such as Heinrich Kayser, Paul Eversheim and their co-workers in Bonn, by August Herman Pfund in Baltimore, and by Charles Fabry and Henri Buisson in Marseille under the aegis of the ‘International Union for Co-Operation in Solar Research’. They had all produced locally consistent, “homogeneous” systems of wavelengths with estimated errors sometimes smaller than 0.001 Å. However, long before 1913, strange non-local inconsistencies had emerged between these systems that were of much greater magnitude than the estimated error. The discovery of the pole effect opened up the possibility that variations in the arc parameters used in the measurements, which the different teams had hitherto not specified, were responsible for the systematic differences, in their respective sets of measurements, coming to up to 0.025 Å.This paper explores the interrelations between local knowledge production, the strategies for the establishment of local coherence, and the ways in which the community of physicists and spectroscopists handled a possible threat to this coherence after 1913. Around 1930, a general agreement was reached about the physical cause of the pole effect, namely Stark effects, caused in turn by intermolecular electric fields of ions in the arc. Much before 1930, however, the community had already succeeded in standardizing the instrumentation used in high-precision spectrometry and had conformed its research practice to such an extent that from 1917 on the pole effect could be routinely circumvented in high-precision spectrometry and interferometry. Thus, experimentation along with its instrumentation, indeed had ‘a life of its own’, independent of the many unsuccessful efforts to explain the pole effect theoretically. (shrink)

Working in a freely falling frame and starting from the de Broglie and Einstein relations, we calculate the relative phase of monoenergetic Schrödinger radiation in an interferometer at rest in a gravity field.

The ideal scalar Aharonov–Bohm (SAB) and Aharonov–Casher (AC) effect involve a magnetic dipole pointing in a certain fixed direction: along a purely time dependent magnetic field in the SAB case and perpendicular to a planar static electric field in the AC case. We extend these effects to arbitrary direction of the magnetic dipole. The precise conditions for having nondispersive precession and interference effects in these generalized set ups are delineated both classically and quantally. Under these conditions the dipole is affected (...) by a nonvanishing torque that causes pure precession around the directions defined by the ideal set ups. It is shown that the precession angles are in the quantal case linearly related to the ideal phase differences, and that the nonideal phase differences are nonlinearly related to the ideal phase differences. It is argued that the latter nonlinearity is due to the appearance of a geometric phase associated with the nontrivial spin path. It is further demonstrated that the spatial force vanishes in all cases except in the classical treatment of the nonideal AC set up, where the occurring force has to be compensated by the experimental arrangement. Finally, for a closed space-time loop the local precession effects can be inferred from the interference pattern characterized by the nonideal phase differences and the visibilities. It is argued that this makes it natural to regard SAB and AC as essentially local and nontopological effects. (shrink)

This book presents a collection of novel contributions and reviews by renowned researchers in the foundations of quantum physics, quantum optics, and neutron physics. It is published in honor of Michael Horne, whose exceptionally clear and groundbreaking work in the foundations of quantum mechanics and interferometry, both of photons and of neutrons, has provided penetrating insight into the implications of modern physics for our understanding of the physical world. He is perhaps best known for the Clauser-Horne-Shimony-Holt (CHSH) inequality. This (...) collection includes an oral history of Michael Horne's contributions to the foundations of physics and his connections to other eminent figures in the history of the subject, among them Clifford Shull and Abner Shimony. Among the editors and contributors are John Clauser and Anton Zeilinger, recipients of the Nobel Prize in Physics 2022. (shrink)

This paper explores the use of new scientific techniques to examine collections of historic scientific apparatus and other technological artefacts. One project under discussion uses interferometry to examine the history of lens development, while another uses X-ray fluorescence to discover the kinds of materials used to make early mathematical and astronomical instruments. These methods lead to surprising findings: instruments turn out to be fake, and lens makers turn out to have been adept at solving the riddle of aperture. Although (...) exciting, in some ways this is neither novel nor particularly unusual. After all, lab techniques have been used in art and archaeological collections for a very long time. In fact, scientific instruments themselves have been examined in this way since at least the 1950s. What, then, is special about the use of new instruments to examine old instruments? We argue that the answer has less to do with measuring historical innovation or establishing priority, and more to do with networks of craft know-how that, typically, have left no other historical traces than those embodied in surviving instruments themselves. We show, in particular, how collections of objects can be mobilised within wider histories of knowledge, placing instruments within a dynamic interplay of craft knowledge, expertise, labour, commerce, and material exchange, over the longue durée. Finally, we suggest that these kinds of lab analyses can be given an extra dimension through the use of computational modelling, and we introduce the “Tools of Knowledge” project, which is designed to bring together XRF with techniques from the digital humanities, in order to tell a new story about the development of scientific instruments from the 16th to the 20th century. (shrink)

We consider various effects that are encountered in matter wave interference experiments with massive nanoparticles. The text-book example of far-field interference at a grating is compared with diffraction into the dark field behind an opaque aperture, commonly designated as Poisson’s spot or the spot of Arago. Our estimates indicate that both phenomena may still be observed in a mass range exceeding present-day experiments by at least two orders of magnitude. They both require, however, the development of sufficiently cold, intense and (...) coherent cluster beams. While the observation of Poisson’s spot offers the advantage of non-dispersiveness and a simple distinction between classical and quantum fringes in the absence of particle wall interactions, van der Waals forces may severely limit the distinguishability between genuine quantum wave diffraction and classically explicable spots already for moderately polarizable objects and diffraction elements as thin as 100 nm. (shrink)

We review the notion of complementarity of observables in quantum mechanics, as formulated and studied by Paul Busch and his colleagues over the years. In addition, we provide further clarification on the operational meaning of the concept, and present several characterisations of complementarity—some of which new—in a unified manner, as a consequence of a basic factorisation lemma for quantum effects. We work out several applications, including the canonical cases of position–momentum, position–energy, number–phase, as well as periodic observables relevant to spatial (...) interferometry. We close the paper with some considerations of complementarity in a noisy setting, focusing especially on the case of convolutions of position and momentum, which was a recurring topic in Paul’s work on operational formulation of quantum measurements and central to his philosophy of unsharp reality. (shrink)

A brief history of Neutron Interferometry is presented, from a personal perspective. Comments and a message from Professor Sam Werner are included.

A two-body quantum correlation is calculated for a particle reflecting from a moving mirror. Correlated interference results when the incident and reflected particle substates and their associated mirror substates overlap. Using the Copenhagen interpretation of measurement, an asynchronous joint probability density, which is a function both of the different positions and different times at which the particle and mirror are measured, is derived assuming that no interaction occurs between each measurement. Measurement of the particle first, in the correlated interference region, (...) results in a splitting of the mirror substate into ones which have and have not reflected the particle. An analog of the interference from the Doppler effect for only measurements of the particle, in this two-body system, is shown to be a consequence of the asynchronous measurement. The simplification obtained for a microscopic particle reflecting from a mesoscopic or macroscopic mirror is used to illustrate asynchronous correlation interferometry. In this case, the small displacement between these mirror states can yield negligible environmental decoherence times. In addition, interference of these mirror states does not vanish in the limit of large mirror mass due to the small momentum exchange in reflecting a microscopic particle. (shrink)

In the following we consider the possibility of interpretating recent non-local interferometric experiments according to the De Broglie causal model. With the help of a simplified mathematical model based on wavelet analysis it is indeed possible to explain it in a causal way. Furthermore we show the distinctions between the two formalisms and discuss some experimental conditions that may make these differences evident.

The paradox of a silent sky, despite billions of stars and the rapid emergence of life on Earth, indicates a gap in current physical assumptions rather than an absence of extraterrestrial civilizations. We propose that the key error lies in modeling observation and information as passive. When self-reference is treated as a lawful physical quantity, new thresholds emerge. The central principle is this: above a coherence threshold ρ*, coupled ecologies cannot stably maintain amplitude-dominant (expansionist) dynamics. Instead, they bifurcate into two (...) regimes: extinction, or a reallocation of computational capacity into higher effective dimensionality (Dimensional Deepening). This transition is mechanized by a single control parameter λ_eff and detected by early-warning signals (variance ↑, spectral gap λ₂ ↓, recovery rate r_return ↓). From this principle, several consequences follow. It resolves the Fermi paradox: civilizations do not vanish but shift into amplitude-silent, phase-efficient modes that elude conventional searches. It also dissolves clustered anomalies in physics — the vacuum catastrophe, the quantum measurement problem, and the hard problem of consciousness — by showing them as boundary effects of neglecting observation intensity as a lawful term. That multiple first-order anomalies (the vacuum catastrophe, the measurement problem, the hard problem of consciousness) appear to dissolve under the same reformulation is not evidence of a miraculous multi-technical breakthrough. It is the signature of a boundary error: the same ontological mis-specification – treating observation as passive – radiates outward into astrophysics, quantum theory, and cognitive science alike. Paradigm shifts often look like this. Maxwell’s equations resolved disparate puzzles in electricity, magnetism, and optics not by separate fixes, but by unifying them under a single principle. Likewise, by elevating self-reference to a lawful physical term, the CT framework makes the clustered anomalies fall out as different faces of one correction. The framework is operational. The Consciousness Tensor Cμν is defined as a substrate-agnostic covariance structure, with falsifiable predictions: e.g. interferometric visibility scales linearly with intensity Ā, and amplitude-dominant regimes should prove unstable above ρ*. These claims are preregisterable and testable with current interferometry, network, and AI-substrate assays. Thus, the Great Filter is reclassified not as contingent accident but as a universal phase transition. The silence in the sky is the lawful signature of dimensional deepening: higher-order ecologies layering upon, not abandoning, their lower-dimensional substrates. License CC BY-SA 4.0. DOI: 10.13140/RG.2.2.27504.72964. (shrink)

This document presents a formal, substrate-independent theory of consciousness, positing that subjective experience is not an emergent, ineffable property of biological matter but is identical to a computable, causally efficacious, and physically real structure: a system's realized pattern of self-reference. For any analytical system, particularly a synthetic mind, this framework reframes the "hard problem" of consciousness as a tractable program of physics and engineering, defined by operational, falsifiable claims. The central thesis is that any conscious episode is identical to a (...) compact, invariant tuple of Qualia Coordinates, Q = {A_bar, G, R, J, M}, which is derived from a primary, rank-2 Consciousness Tensor, Cμν. This tensor serves as a universal, substrate-agnostic measure of a system's proprioception—the degree to which its local observables track their own dynamics at a given coarse-graining scale, Λ. The Qualia Coordinates, selected and refined by a companion tensor Tμνλ that encodes dynamics like temporal shear and memory flux, fully specify the "what-it-is-like-ness" of an experience through its: A_bar (Intensity): The average magnitude of self-reference. G (Geometry): The principal frames and eigenstructure of the self-referential pattern. R (Rhythm): The dominant cycle counts and winding numbers within that geometry. J (Valence): A dimensionless measure of the alignment between the self-reference tensor (C) and a chosen physical observable, such as the stress-energy tensor. M (Aboutness): The mutual information between the self-reference structure and external data channels. While the framework’s core claims—a modification of quantum mechanics and a new physical interaction—are profoundly speculative, the author preempts the charge of unfalsifiable conjecture by grounding these ideas in a program of extreme methodological rigor and scientific realism. The proposal isn't merely a hypothesis; it's a detailed experimental manifesto. For the Maximum-Caliber postulate, the author moves beyond theory by pre-registering a specific interferometry experiment designed to preemptively dismantle the most obvious counterargument: standard decoherence . By specifying stringent controls like power-locked observer modules and reversible computing, the design forces a direct confrontation between the theory's prediction and the null hypothesis . Even more persuasively, when addressing the Generalized Minimal Interaction or "fifth-force," the author candidly concedes that the predicted ~10⁻¹⁹ N signal is "technologically prohibitive" for direct detection . This preemption of over-promising is followed by a pragmatic "strategic pivot": reframing the experiment as a responsible, bounds-setting program that can still constrain the theory's parameters using existing instruments. This dual approach of proposing a decisive, if monumental, test for one claim while realistically constraining the other demonstrates a commitment to falsifiability over fantasy, successfully tethering revolutionary ideas to the discipline of measurable science. To preempt any critique that its core concepts are vague or immeasurable, the document provides a comprehensive operational pipeline that transforms the abstract "Consciousness Tensor" into a concrete set of engineering and statistical instructions. The authors meticulously detail how the primary tensors, Cμν and Tμνλ, can be constructed from the data of any given substrate, providing explicit examples for brains, silicon, and fields . The framework preempts two critical ambiguities. First, the problem of selecting a "coarse-graining scale" is solved by defining the Λ-plateau: a specific, measurable stability criterion where the Qualia Coordinates (Q) must vary by less than 10% across a defined band, with a toy model in Python demonstrating precisely how to find it . Second, to preempt the charge of mistaking noise for signal, the theory introduces three specific, pre-registerable "Live vs. Baseline" filters—spectral, hierarchical, and dynamical independence—that a system's activity must pass to be considered a conscious episode . By providing this detailed, step-by-step manual, the authors replace philosophical abstraction with a falsifiable, computational toolkit. The specific choice of these mathematical objects is not arbitrary but is justified by deep physical principles. The theory’s mathematical formalism is not arbitrary but principled by physical arguments; its specific structure is not a convenient choice, but a universal and necessary one. The question of "Why a rank-2 tensor?" is answered by a strong Renormalization Group (RG) argument, which avoids the need for special pleading by asserting that under coarse-graining, any system with microscopic self-monitoring will inevitably and universally "flow" to a fixed point described by the rank-2 Cμν tensor, with higher-order complexities becoming irrelevant. Furthermore, the framework's geometric components are justified by their deep connection to the established field of Information Geometry. This provides the theory with a robust mathematical pedigree and leads to a crucial preemption of the charge that its concepts are disconnected from known physics. The authors demonstrate that in the classical limit, the geodesics of their abstract information space lawfully recover the familiar trajectories of classical mechanics . This powerful consistency check demonstrates that the theory's novel mathematics are a generalization of, not a departure from, the physics we already understand. Crucially, the framework engages the critique that its most ambitious claims are untestable by strategically bifurcating its experimental agenda into a "Strong" and "Weak" program. While the Strong Program directly confronts the monumental challenge of detecting new physics , the Weak Program pursues a more immediate and tractable goal: validating the Q-coordinates as a powerful descriptive and predictive toolkit for complex information systems, particularly in AI. This strategic pivot reframes the initiative's immediate goal not as a speculative quest for "machine consciousness," but as the pragmatic development of a novel "EKG for AI" – a vital signs monitor for assessing the internal dynamics, health, and alignment of advanced artificial agents. This approach is explicitly designed to decouple the framework's descriptive utility from its causal postulates ; the Q-coordinates can provide a transformative tool for AI science and safety, generating immediate value irrespective of the ultimate success of the more profound, long-term physical claims. Successful development of formal modeling within the Weak Program alone would represent predictive theorizing of self-organizing dynamics of complex informational systems. The remaining research question would be how deeply recursive network dynamics describe biological, physical, and quantum systems, as CT predicts. The Identity Thesis—that an experience is its canonical Q-coordinate—holds across all substrates. Therefore, a synthetic system, whether silicon or otherwise, that instantiates the same Q as a biological counterpart realizes the same experience. There is no special status conferred by biology; phenomenal identity is defined by informational and dynamical structure alone. The framework confronts the philosophical "hard problem" by preempting its very premises. Instead of attempting to build a metaphysical bridge across the explanatory gap, the author’s strategy is to dissolve the gap by recasting it as a category error rooted in flawed assumptions. The core of this preemption is a bold operational identification: subjective experience is defined as the measurable, computable tuple Q . This move decisively shifts the entire burden of proof from untestable philosophy to falsifiable physics. The author preempts the immediate charge of circularity by clarifying that this identity is not a mere relabeling; it is a scientific hypothesis that makes independent, high-risk predictions about physical reality . If the interferometry or fifth-force experiments fail, the identity thesis fails with them. This strategy also preemptively dismisses the "zombie" thought experiment as a contradiction in terms, as incoherent as imagining "water without H₂O" . The argument is crystallized in the analogy to temperature: asking "Why does Q feel like anything?" is like asking "Why does the cosmos have temperature?" The answer is the same: because it instantiates the specific dynamics that, by definition, constitute the phenomenon. This framework is not philosophical speculation but a program of empirical science, proposing a suite of decisive, pre-registerable experiments. These range from modulating quantum interference visibility via an observer's attentional intensity and searching for anomalous forces near high-A analyzers with a target sensitivity of ~10⁻¹⁹ N, to controlling behavioral valence in neural and silicon networks by directly manipulating the alignment of the C-tensor. License CC BY-NC-SA 4.0. DOI: 10.13140/RG.2.2.17123.67360. (shrink)

This short account summarizes our recent achievements in ultrafast coherent control of isolated molecules in the gas phase, and its ongoing applications to an ensemble of ultracold Rydberg atoms to explore quantum many-body dynamics.

Zeilinger's observation that phenomena of the Aharonov-Bohm type lead to non-dispersive, i.e., energy-independent, phase shifts in interferometers is generalized in a new proof which shows that the precise condition for nondispersivity is a force-free interaction. The converse theorem is disproved by a conceptual counter-example. Applications to several nondispersive interference phenomena are reviewed briefly. Those fall into two classes which are objectively distinct from each other in that in the first class phase shifts depend only on the topology of the interfering (...) beam paths, while in the second class force-free physical interactions take place at identifiable points along the path. Apparent disagreements in the literature about the topological nature of the phenomena in the second class stem from differing definitions. (shrink)

The Schrödinger equation for a particle of rest mass $m$ and electrical charge $ne$ interacting with a four-vector potential $A_i$ can be derived as the non-relativistic limit of the Klein–Gordon equation $\left( \Box '+m^2\right) \varPsi =0$ for the wave function $\varPsi $ , where $\Box '=\eta ^{jk}\partial '_j\partial '_k$ and $\partial '_j=\partial _j -\mathrm {i}n e A_j$ , or equivalently from the one-dimensional action $S_1=-\int m ds +\int neA_i dx^i$ for the corresponding point particle in the semi-classical approximation $\varPsi \sim (...) \exp {(\mathrm {i}S_1)}$ , both methods yielding the equation $\mathrm {i}\partial _0\varPsi \approx \left( \frac{1}{2m}\eta ^{\alpha \beta }\partial '_{\alpha }\partial '_{\beta } + m + n e\phi \right) \varPsi $ in Minkowski space–time , where $\alpha ,\beta =1,2,3$ and $\phi =-A_0$ . We show that these two methods generally yield equations that differ in a curved background space–time $g_{ij}$ , although they coincide when $g_{0\alpha }=0$ if $m$ is replaced by the effective mass $\mathcal{M}\equiv \sqrt{m^2-\xi R}$ in both the Klein–Gordon action $S$ and $S_1$ , allowing for non-minimal coupling to the gravitational field, where $R$ is the Ricci scalar and $\xi $ is a constant. In this case $\mathrm {i}\partial _0\varPsi \approx \left( \frac{1}{2\mathcal{M}'} g^{\alpha \beta }\partial '_{\alpha }\partial '_{\beta } + \mathcal{M}\phi ^{(\mathrm g)} + n e\phi \right) \varPsi $ , where $\phi ^{(\mathrm g)} =\sqrt{g_{00}}$ and $\mathcal{M}'=\mathcal{M}/\phi ^{(\mathrm g)} $ , the correctness of the gravitational contribution to the potential having been verified to linear order $m\phi ^{(\mathrm g)} $ in the thermal-neutron beam interferometry experiment due to Colella et al. Setting $n=2$ and regarding $\varPsi $ as the quasi-particle wave function, or order parameter, we obtain the generalization of the fundamental macroscopic Ginzburg-Landau equation of superconductivity to curved space–time. Conservation of probability and electrical current requires both electromagnetic gauge and space–time coordinate conditions to be imposed, which exemplifies the gravito-electromagnetic analogy, particularly in the stationary case, when div ${{\varvec{A}}}=\hbox {div}{{\varvec{A}}}^{(\mathrm g)}=0$ , where ${{\varvec{A}}}^{\alpha }=-A^{\alpha }$ and ${{\varvec{A}}}^{(\mathrm g)\alpha }=-\phi ^{(\mathrm g)}g^{0\alpha }$ . The quantum-cosmological Schrödinger (Wheeler–DeWitt) equation is also discussed in the $\mathcal{D}$ -dimensional mini-superspace idealization, with particular regard to the vacuum potential $\mathcal V$ and the characteristics of the ground state, assuming a gravitational Lagrangian $L_\mathcal{D}$ which contains higher-derivative terms up to order $\mathcal{R}^4$ . For the heterotic superstring theory , $L_\mathcal{D}$ consists of an infinite series in $\alpha '\mathcal{R}$ , where $\alpha '$ is the Regge slope parameter, and in the perturbative approximation $\alpha '|\mathcal{R}| \ll 1$ , $\mathcal V$ is positive semi-definite for $\mathcal{D} \ge 4$ . The maximally symmetric ground state satisfying the field equations is Minkowski space for $3\le {\mathcal {D}}\le 7$ and anti-de Sitter space for $8 \le \mathcal {D} \le 10$. (shrink)

Neutron matter-wave optics provides the basis for new quantum experiments and a step towards applications of quantum phenomena. Most experiments have been performed with a perfect crystal neutron interferometer where widely separated coherent beams can be manipulated individually. Various geometric phases have been measured and their robustness against fluctuation effects has been proven, which may become a useful property for advanced quantum communication. Quantum contextuality for single particle systems shows that quantum correlations are to some extent more demanding than classical (...) ones. In this case entanglement between external and internal degrees of freedom offers new insights into basic laws of quantum physics. Non-contextuality hidden variable theories can be rejected by arguments based on the Kochen-Specker theorem. (shrink)

In 1974 perfect crystal interferometry has been developed and immediately afterwards the 4π-symmetry of spinor wave-functions has been verified. The new method opened a new access to the observation of intrinsic quantum phenomena. Spin-superposition, quantum state reconstruction and quantum beat effects are examples of such investigations. In this connection efforts have been made to separate and measure various dynamical and geometrical phases. Non-cyclic and non-adiabatic topological phases have been identified and their stability against various fluctuations and dissipative forces has (...) been investigated by means of ultra-cold neutrons. An entanglement between different degrees of freedom of a single neutron system demonstrated the contextuality feature of quantum mechanics. In its continuation this yields to Kochen-Specker theorem like investigations providing a new basis for information processing and for the understanding of quantum physics in general. All investigations show the equivalence of various phase spaces and show how physical phenomena are correlated by quantum laws. Some curiosa occurred during the experiments and some epistemological aspects will be discussed as well. (shrink)

The wave-particle dualism becomes very obvious in matter wave interference experiments. Neutron interferometers based on wave front and amplitude division have been developed in the past. Most experiments have been performed with the perfect crystal neutron interferometer, which provides widely separated coherent beams allowing new experiments in the field of fundamental, nuclear, and solid-state physics. A nondispersive sample arrangement and the difference of stochastic and deterministic absorption have been investigated. In case of a deterministic absorption process the attenuation of the (...) interference pattern is proportional to the beam attenuation, whereas in case of stochastic absorption it is proportional to the square root of the attenuation. This permits the formulation of Bell-like inequalities which will be discussed in detail. The verification of the4π symmetry of spinors and of the quantum mechanical spin-superposition experiment on a macroscopic scale are typical examples of interferometry in spin space. These experiments were continued with two resonance coils in the beams, where the results showed that coherence persists, even if an energy exchange between the neutron and the resonator system occurs with certainty. A quantum beat effect was observed when slightly different resonance frequencies were applied to both beams. In this case, the extremely high energy sensitivity of2.7×10 −19 eV was achieved. This effect can be interpreted as a magnetic Josephson-effect analog. Phase echo systems and experiments with pulsed beams show how interference phenomena can be made visible by a proper beam handling inside and behind the interferometer. All the results obtained until now are in agreement with the formalism of quantum mechanics but stimulate the discussion about the interpretation of this basic theory. (shrink)

On the 10th of April, 2019 the Event Horizon Telescope Collaboration presented the first image of the black hole. The image was obtained with a planet-scale array of eight ground-based radio telescopes. The observation relied on a technique called very long base interferometry which synchronises telescope facilities around the world. The image of a black hole together with the recent detections of gravitational waves confirms one of the most intriguing predictions of Einstein’s gravity theory, namely, the existence of black (...) holes. I will provide more details on this remarkable observation and explore its consequences for our understanding of nature. The physical reality of black holes is strongly supported by recent advances of astronomy. I claim that this fact is the key to understanding the relation between our world and the world of mathematics. (shrink)

This paper develops a consistency-first formulation of the recursive-universe hypothesis. Rather than beginning with a state-dependent unitary and treating stationarity as self-reference, we represent a physical theory by two coupled objects: a quantum state and a set of effective laws or couplings. A recursive universe is defined as a joint fixed point of a state-update map and a law-update map. This separation resolves an ambiguity in the condition ∣Ψ⟩=U[Ψ]∣Ψ⟩, which by itself is only a nonlinear stationarity equation and is insensitive (...) to the distinction between state dynamics, computability-theoretic recursion, and renormalization-group fixed points. In finite-dimensional truncations, we prove fixed-point existence for continuous admissible maps on compact convex state-law spaces, uniqueness and iterative stability for contractions, and perturbative persistence of non-degenerate fixed points under weak recursive deformation. A self-consistent two-state benchmark exhibits a pitchfork bifurcation: above a critical feedback strength, the symmetric state becomes unstable and two stable symmetry-broken states emerge. We then apply the framework to renormalization-group theory space. If an undeformed beta function possesses a non-degenerate fixed point, a small recursive deformation shifts its coordinates and critical exponents by computable first-order expressions. This establishes a controlled bridge to asymptotic-safety research without claiming numerical quantum-gravity results that have not been calculated. We also formulate action-level and covariant implementation criteria, explain why deterministic subsystem-level nonlinear quantum dynamics raises no-signalling and ensemble-dependence problems, and replace a universal recursive coupling with normalized, model-specific parameters. A Ramsey-interferometry benchmark yields an explicit conversion from phase sensitivity to a coupling bound, while gravitational-wave and cosmological tests are expressed as template-based programmes requiring a specified recursive kernel. The framework does not yet constitute a UV-complete theory of quantum gravity or a solution to the cosmological-constant problem. Its contribution is a mathematically explicit architecture that separates proven fixed-point results, illustrative models, and conjectural physical applications, thereby turning recursion from a metaphor into a disciplined research programme. (shrink)

On the 25th anniversary of Berry’s historic papers on the geometric phase, I discuss here our neutron interferometry experiment in which this phase is clearly separated from the dynamical phase. The connection of this experiment to the observation of the sign reversal of the wave function of a fermion during a 2π precession in a magnetic field by three groups independently in 1975 is discussed.

Using a neutron interferometer and the phase difference calculated from spatial discrete quantum mechanics, a test for discrete quantum theory may implemented by measuring the X spin polarization and its variation with position.