Rod photoreceptors are among the most sensitive light detectors in nature. They achieve their remarkable sensitivity across a wide variety of species through a number of essential adaptations: a specialized cellular geometry, a G‐protein cascade with an unusually stable receptor molecule, a low‐noise transduction mechanism, a nearly perfect effector enzyme, and highly evolved mechanisms of feedback control and receptor deactivation. Practically any change in protein expression, enzyme activity, or feedback control can be shown to impair photon detection, either by decreasing (...) sensitivity or signal‐to‐noise ratio, or by reducing temporal resolution. Comparison of mammals to amphibians suggests that rod outer‐segment morphology and the molecules and mechanism of transduction may have evolved together to optimize light sensitivity in darkness, which culminates in the extraordinary ability of these cells to respond to single photons at the ultimate limit of visual perception. (shrink)

This thesis uses high-precision single-photon experiments to shed new light on the role of reality, causality, and uncertainty in quantum mechanics. It provides a comprehensive introduction to the current understanding of quantum foundations and details three influential experiments that significantly advance our understanding of three core aspects of this problem. The first experiment demonstrates that the quantum wavefunction is part of objective reality, if there is any such reality in our world. The second experiment shows that quantum correlations cannot (...) be explained in terms of cause and effect, even when considering superluminal influences between measurement outcomes. The final experiment in this thesis demonstrates a novel uncertainty relation for joint quantum measurements, where the textbook relation does not apply. (shrink)

We review the present status of wave-particle duality of single-photon states in the context of some recent experiments. In particular, Bohr's complementarity principle is critically reexamined. It is explained in detail how this principle is confronted in these experiments and how a contradiction with the notion of “mutual exclusiveness” of classical wave and particle pictures emerges.

Simultaneous observation of the wave-like and particle-like aspects of the photon in the double-slit experiment is unallowed. The underlying reason behind this limitation is not understood. In this paper, we explain this unique behavior by considering the communicational properties of the photons. Photons have three independently adjustable properties (energy, direction, and spin) that can be used to communicate messages. The double-slit experiment setup fixes two of these properties and confines the single photon’s capacity for conveying messages to (...) no more than one message. With such a low communication capacity, information theory dictates that measurements associated only with one proposition can obtain consistent results, and a second measurement associated with an independent proposition must necessarily lead to randomness. In the double-slit example, these are the wave or particle properties of the photon. The interpretation we offer is based on the formalism of information theory and does not make use of Heisenberg’s uncertainty relation in any form. (shrink)

The theory of causal Bayes nets [15, 19] is, from an empirical point of view, currently one of the most promising approaches to causation on the market. There are, however, counterexamples to its core axiom, the causal Markov condition. Probably the most serious of these counterexamples are EPR/B experiments in quantum mechanics (cf. [13, 23]). However, these are also the only counterexamples yet known from the quantum realm. One might therefore wonder whether they are the only phenomena in the quantum (...) realm that create problems for causal Bayes nets. The aim of this paper is to demonstrate that not only the phenomenon of quantum correlations in EPR/B experiments create problems for causal Bayes nets, but also the temporal evolution of quantum systems, which is described as dualistic by quantum mechanics. For this purpose, it is shown that single photon experiments in a Mach-Zehnder interferometer (MZI) violate the causal Markov condition as well. It is then argued, however, that the Markov violation does not occur under the de Broglie-Bohm interpretation of Bohmian mechanics. (shrink)

IntroductionDeep brain stimulation is an effective treatment for advanced Parkinson’s disease with the targeting bilateral subthalamic nucleus or globus pallidus internus. So far, detailed studies on the efficacy of unilateral STN-DBS for motor symptoms have been reported, but few studies have been conducted on unilateral GPi-DBS.Materials and MethodsSeventeen patients with Parkinson’s disease who underwent unilateral GPi-DBS were selected. We conducted comparison analyses between scores obtained 6–42 months pre- and postoperatively using the following measurement tools: the Movement Disorder Society Unified Parkinson’s (...) Disease Rating Scale part III, the Hoehn and Yahr stage, the presence/absence of dyskinesia, Mini-Mental State Examination, Frontal Assessment Battery, Geriatric Depression Scale, levodopa equivalent dose, and cerebral blood flow by single photon emission computed tomography. Patient backgrounds were compared between four cohorts with favorable and unfavorable postoperative outcome.ResultsSignificant improvement was observed postoperatively in the following: total MDS-UPDRS Part III scores during the off period, contralateral scores, ipsilateral scores, and axial scores. Similarly, the Hoehn and Yahr stages during the off period, and GDS also showed significant decrease. In contrast, LED, MMSE, and FAB remained unchanged while the number of patients who scored positive for dyskinesia decreased by 40%. Abnormal cerebral blood flow preoperatively seen in the cerebral cortex had normalized in the total score-based good responder cohort. In the ipsilateral score-based good responder cohort, cerebral blood flow increased in the contralateral frontal lobe including in the premotor cortex, contralateral to the DBS. Compared to the poor responders, postoperative good responders demonstrated significantly higher preoperative MMSE scores.DiscussionUnilateral GPi-DBS therapy was effective in improving contralateral, ipsilateral, and axial motor symptoms of patients with advanced PD; in particular, it was found to be especially beneficial in PwPD whose cognitive function was unimpaired; the treatment efficacy rivaled that of bilateral counterparts up till at least 6 months postoperatively. Finally, normalization of preoperative abnormalities in cerebral blood flow and increased cerebral blood flow in the contralateral frontal lobe indicated the beneficial potential of this therapy on ipsilateral motor symptoms. (shrink)

A prominent way through which wave-particle duality has been ascribed to photons is by illustrating their “wave-like” behaviour in the Mach-Zehnder interferometer and “particle-like” behaviour in the anti-correlation experiment. This duality has been formulated in two ways. Some have based the claim on the complementarity principle. This formulation, however, has already been shown to be problematic. Others have made a much simpler duality claim by considering that single-photons are analogous to waves and particles in the above experiments. (...) I criticise this formulation by arguing that the analogies cannot be distinctly established. Thus, this duality claim is found to be unsubstantiated. (shrink)

This paper takes as its point of departure recent research into the possibility that human beings can perceive single photons. In order to appreciate what quantum perception may entail, we first explore several of the leading interpretations of quantum mechanics, then consider an alternative view based on the ontological phenomenology of Maurice Merleau-Ponty and Martin Heidegger. Next, the philosophical analysis is brought into sharper focus by employing a perceptual model, the Necker cube, augmented by the topology of the (...) Klein bottle. This paves the way for addressing in greater depth the paper’s central question: Just what would it take to observe the quantum reality of the photon? In formulating an answer, we examine the nature of scientific objectivity itself, along with the paradoxical properties of light. The conclusion reached is that quantum perception requires a new kind of observation, one in which the observer of the photon adopts a concretely self-reflexive observational posture that brings her into close ontological relationship with the observed. (shrink)

In a quantum mechanical two-slit experiment one can observe a single photon simultaneously as particle (measuring the path) and as wave (measuring the interference pattern) if the path and the interference pattern are measured in the sense of unsharp observables. These theoretical predictions are confirmed experimentally by a photon split-beam experiment using a modified Mach—Zehnder interferometer.

When a single beam-splitter receives two beams of bosons described by Fock states (Bose-Einstein condensates at very low temperatures), interesting generalizations of the two-photon Hong-Ou-Mandel effect take place for larger number of particles. The distributions of particles at two detectors behind the beam splitter can be understood as resulting from the combination of two effects, the spontaneous phase appearing during quantum measurement, and the quantum angle. The latter introduces quantum “population oscillations”, which can be seen as a generalized Hong-Ou-Mandel (...) effect, although they do not always correspond to even-odd oscillations. (shrink)

Under an approach advocated by Noyes, this paper introduces a testable theory which explains a single-photon type of nonlinear photoionization described by Panarella. The present theory differs from that of Panarella in that the former depends upon the standard first principles of quantum mechanics, while the latter seeks to revise these principles.

Maxwell's equations are formulated as a relativistic “Schrödinger-like equation” for a single photon of a given helicity. The probability density of the photon satisfies an equation of continuity. The energy eigenvalue problem gives both positive and negative energies. The Feynman concept of antiparticles is applied here to show that the negative-energy states going backward in time (t → −t) give antiphoton states, which are photon states with the opposite helicity. For a given mode, properties of a photon, such as (...) energy, linear momentum, total angular momentum, orbital angular momentum, and spin are equivalent in both classical electromagnetic field theory and quantum theory. The single-photon Schrödinger equation is field (or “second”) quantized in a gauge-invariant way to obtain the quantum field theory of many photons. This approach treats the quantization of electromagnetic radiation in a way that parallels the quantization of material particles and, thus, provides a unified treatment. (shrink)

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)

The number of independent messages a physical system can carry is limited by the number of its adjustable properties. In particular, systems that have only one adjustable property cannot carry more than a single message at a time. We demonstrate this is the case for the single photons in the double-slit experiment, and the root of the fundamental limit on measuring the complementary aspect of the photons. Next, we analyze the other ‘quantal’ behavior of the systems (...) with a single adjustable property, such as noncommutativity and no-cloning. Finally, we formulate a mathematical theory to describe the dynamics of such systems and derive the standard Hilbert-space formalism of quantum mechanics. Our derivation demonstrates the physical foundation of the quantum theory. (shrink)

The evolution of a single trapped ion exhibiting intermittent fluorescence and dark periods may be described either as a continuous process, using differential rate equations, or discretely, as a Markov process. The latter models the atom as making instantaneous transitions from one energy eigenstate to another, and is open to the objection that superpositions of energy states will form which are not covered by the Markov process. The superposition objection is replied to, and two new mathematical elements, Markov vectors (...) and Markov matrices, are proposed as additions to quantum theory. The paper concludes by attributing the cause of dark periods in the ion's history to instantaneous transitions in the ion itself, rather than to photon detection or other components of measurement. (shrink)

The recent development of single molecule detection techniques has opened new horizons for the study of individual macromolecules under physiological conditions. Conformational subpopulations, internal dynamics and activity of single biomolecules, parameters that have so far been hidden in large ensemble averages, are now being unveiled. Herein, we review a particular attractive solution‐based single molecule technique, fluorescence correlation spectroscopy (FCS). This time‐averaging fluctuation analysis which is usually performed in Confocal setups combines maximum sensitivity with high statistical confidence. FCS (...) has proven to be a very versatile and powerful tool for detection and temporal investigation of biomolecules at ultralow concentrations on surfaces, in solution, and in living cells. The introduction of dual‐color cross‐correlation and two‐photon excitation in FCS experiments is currently increasing the number of promising applications of FCS to biological research. BioEssays 24:758–764, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

We describe in detail the first experimental test that distinguishes between an event-based corpuscular model of the interaction of photons with matter and quantum mechanics. The test looks at the interference that results as a single photon passes through a Mach-Zehnder interferometer. The experimental results, obtained with a low-noise single-photon source, agree with the predictions of standard quantum mechanics.

Dans le titre un peu provocateur de ce livre, les lecteurs reconnaîtront sans peine un clin d’œil fait à la parabole du « fils prodigue » de l’évangile de Luc. D’emblée, l’auteure explique l’intérêt de ce récit biblique : alors que le fils dont il est question, revient à la maison, domaine privilégié des femmes, la parabole ne parle jamais d’elles. L’histoire de Luc ne concerne que des hommes. Pour Élisabeth Parmentier, ce silence est significatif de l’expérience des femmes dans (...) la « maison-É... (shrink)

Alternative theories to quantum mechanics motivate important fundamental tests of our understanding and descriptions of the smallest physical systems. Here, using spontaneous parametric downconversion as a heralded single-photon source, we place experimental limits on a class of alternative theories, consisting of classical field theories which result in power-dependent normalized correlation functions. In addition, we compare our results with standard quantum mechanical interpretations of our spontaneous parametric downconversion source over an order of magnitude in intensity. Our data match the quantum (...) mechanical expectations, and do not show a statistically significant dependence on power, limiting quantum mechanics alternatives which require power-dependent autocorrelation functions. (shrink)

Since 1990, the multinational public accounting firms have all adopted flexible work arrangement policies. In part, the firms are doing this to fulfill an ethical obligation in creating an appropriate professional environment for their employees. This study examines the effect of participation in a flexible work arrangement program on an individual''s professional success and anticipated turnover as perceived by the participant''s peers and superiors. Subjects from one Big Five accounting firm read a description of a manager and answered a series (...) of questions about the likelihood of the manager''s promotion to partner, voluntary and involuntary turnover, and desirability on a job. Gender and participation in a flexible work arrangement were manipulated in a 2×2 design. The results indicate that participation in a flexible work arrangement evoked significantly more pessimistic predictions on all of the dimensions. Gender did not have an effect on the likelihood ratings. Follow-up questions about the factors that enhance and hinder individuals career success in each work scenario indicated that the perceived ability to "juggle" and the ability to "pull one''s weight" potentially affects evaluations of what it takes to be a successful professional in the financial services environment. Implications for professional and ethics practice and research are also presented. (shrink)

J’ai rencontré Marie-Jeanne Bérère à Lyon en 1994. C’était une petite femme vive, à la parole claire et précise, avec un bel accent bourguignon. Elle avait accepté une interview, à son domicile lyonnais, le 23 mars 1995. Je souhaitais la revoir pour ce numéro de CLIO, Histoire, Femmes et Sociétés sur les Chrétiennes mais elle est décédée dans l’été 2000, à 73 ans, sans avoir eu le temps de rédiger ses mémoires. Son itinéraire de femme engagée dans l’Église catholique est (...) celui d’une chrétienn... (shrink)

Flexible work arrangements (FWAs) are widely offered in public accounting as a tool to retain valued professional staff. Previous research has shown that participants in FWAs are perceived to be less likely to succeed in their careers in public accounting than individuals in public accounting who do not participate in FWAs (Cohen and Single, 2001). Research has also documented an increasing backlash against family–friendly policies in the workplace as placing unfair burdens on individuals without children. Building directly on a (...) previous study in this journal (Cohen and Single, 2001), this study addresses the issue of whether the documented perceptions toward FWA participants are the result of electing to take part in the FWA or the result of bias against employees with children. The research questions are addressed in a 3 × 2 experimental setting in which we manipulate FWA participation, along with family status and gender of a hypothetical manager in a public accounting firm. Our findings indicate that FWA participants are viewed as less likely to advance and as less committed than individuals without children or individuals who had children but who were not taking part in a FWA. Male FWA participants are viewed as less likely to succeed than female FWA participants. This effect appears to arise from a perception that FWA participants are willing to make sacrifices in their careers to accommodate family needs and thus may not be as committed to making the sacrifices perceived as necessary to meet the rigorous demands of the public accounting environment. This raises the ethical question of what could be done to change the culture in public accounting to foster a substantive support system for individuals who want to balance a family and a career. (shrink)

Flexible work arrangements (FWAs) are widely offered in public accounting as a tool to retain valued professional staff. Previous research has shown that participants in FWAs are perceived to be less likely to succeed in their careers in public accounting than individuals in public accounting who do not participate in FWAs (Cohen and Single, 2001). Research has also documented an increasing backlash against family–friendly policies in the workplace as placing unfair burdens on individuals without children. Building directly on a (...) previous study in this journal (Cohen and Single, 2001), this study addresses the issue of whether the documented perceptions toward FWA participants are the result of electing to take part in the FWA or the result of bias against employees with children. The research questions are addressed in a 3 × 2 experimental setting in which we manipulate FWA participation, along with family status and gender of a hypothetical manager in a public accounting firm. Our findings indicate that FWA participants are viewed as less likely to advance and as less committed than individuals without children or individuals who had children but who were not taking part in a FWA. Male FWA participants are viewed as less likely to succeed than female FWA participants. This effect appears to arise from a perception that FWA participants are willing to make sacrifices in their careers to accommodate family needs and thus may not be as committed to making the sacrifices perceived as necessary to meet the rigorous demands of the public accounting environment. This raises the ethical question of what could be done to change the culture in public accounting to foster a substantive support system for individuals who want to balance a family and a career. (shrink)

Neurotherapies for diagnostics and treatment—such as electroencephalography (EEG) neurofeedback, single-photon emission computerized tomography (SPECT) imaging for neuropsychiatric evaluation, and off-label/experimental uses of brain stimulation—are continuously being offered to the public outside mainstream healthcare settings. Because these neurotherapies share many key features of complementary and alternative medicine (CAM) techniques—and meet the definition of CAM as set out in Kaptchuk and Eisenberg—here we refer to them as “alternative neurotherapies.” By explicitly linking these alternative neurotherapy practices under a common conceptual framework, this (...) paper draws attention to, and critically considers, the cross-cutting ethical and legal issues related to the provision of these services. The first section of this paper provides an updated empirical overview of uses of SPECT neuropsychiatric evaluations, EEG neurofeedback, and experimental/off-label forms of brain stimulation. Next, drawing on CAM bioethics scholarship, we highlight the pertinent ethical issues in the alternative neurotherapy context, including the truthful representation of evidence base, marketing to vulnerable populations, potential harms, provider competency, and conflicts of interest. Finally, we consider the principal legal issues at stake for the provision of alternative neurotherapies in the U.S., namely those related to licensing and scope-of-practice considerations. We conclude with recommendations for future research in this domain. (shrink)

We report on the simultaneous determination of complementary wave and particle aspects of light in a double-slit type “welcher-weg” experiment beyond the limitations set by Bohr’s Principle of Complementarity. Applying classical logic, we verify the presence of sharp interference in the single photon regime, while reliably maintaining the information about the particular pinhole through which each individual photon had passed. This experiment poses interesting questions on the validity of Complementarity in cases where measurements techniques that avoid Heisenberg’s uncertainty principle (...) and quantum entanglement are employed. We further argue that the application of classical concepts of waves and particles as embodied in Complementarity leads to a logical inconsistency in the interpretation of this experiment. (shrink)

Few revolutions in science have been more far-reaching--but less understood--than the quantum revolution in physics. Everyday experience cannot prepare us for the sub-atomic world, where quantum effects become all-important. Here, particles can look like waves, and vice versa; electrons seem to lose their identity and instead take on a shifting, unpredictable appearance that depends on how they are being observed; and a single photon may sometimes behave as if it could be in two places at once. In the world (...) of quantum mechanics, uncertainty and ambiguity become not just unavoidable, but essential ingredients of science--a development so disturbing that to Einstein "it was as if God were playing dice with the universe." And there is no one better able to explain the quantum revolution as it approaches the century mark than David Lindley. He brings the quantum revolution full circle, showing how the familiar and trustworthy reality of the world around us is actually a consequence of the ineffable uncertainty of the subatomic quantum world--the world we can't see. (shrink)

Precise and timely diagnosis of Parkinson’s disease is important to control its progression among subjects. Currently, a neuroimaging technique called dopaminergic imaging that uses single photon emission computed tomography (SPECT) with 123I-Ioflupane is popular among clinicians for detecting Parkinson’s disease in early stages. Unlike other studies, which consider only low-level features like gray matter, white matter, or cerebrospinal fluid, this study explores the non-linear relation between different biomarkers (SPECT + biological) using deep learning and multivariate logistic regression. Striatal binding (...) ratios are obtained using 123I-Ioflupane SPECT scans from four brain regions which are further integrated with five biological biomarkers to increase the diagnostic accuracy. Experimental results indicate that this investigated approach can differentiate subjects with 100% accuracy. The obtained results outperform the ones reported in the literature. Furthermore, logistic regression model has been developed for estimating the Parkinson’s disease onset probability. Such models may aid clinicians in diagnosing this disease. (shrink)

Consider the case of the double slit expt where a single photon lands on the film and twenty years later the film gets developed and a human observer looks at it. Question: What is the state of the universe during those twenty years ? (The Schrodinger cat business).

The statistical aspects of quantum explanation are intrinsic to quantum physics; individual quantum events are created in the interactions associated with observation and are not describable by predictive theory. The superposition principle shows the essential difference between quantum and non-quantum physics, and the principle is exemplified in the classic single-photon two-slit interference experiment. Recently Mandel and Pfleegor have done an experiment somewhat similar to the optical single-photon experiment but with two independently operated lasers; interference is obtained even with (...) beam intensity so small that only one photon is in the apparatus at a time. The result can be understood in terms of the superposition of states; or, in terms of the Uncertainty Principle, which is found to forbid the determination of which of the two lasers is the source of a given photon (if conditions for interference are to obtain). The Mandel-Pfleegor experiment gives a physical argument against the continuous localization of a photon that is assumed in the hidden variable theories and therefore gives further support for the generally accepted view that an observed entity (observed state) is created in the observation event. This aspect of quantum physics implies a subjectivism on the level of individual quantum-level occurrences, since there is in quantum theory no basis for asserting the existence of the event independently of observation of it. Extension of this subjectivism to large scale, non-quantum phenomena falls within the principles of quantum theory; counter considerations that argue against such an extension are noted. (shrink)

The issues, raised in Żukowski (arXiv:0809.0115v1, 2008), concerning the relevance of the von Neumann theorem for the single-system’s quantumness test proposed in Alicki and Van Ryn (J. Phys. A: Math. Theor. 41:062001, 2008) and performed for the case of single photon polarization in Brida et al. (Opt. Express 16:11750, 2008; arXiv:0811.3376, 2008) and the usefulness of Bell’s inequality for testing the idea of macroscopic quantum systems are discussed in some details. Finally, the proper quantum mechanical description of the (...) experiment with polarized photon beams is presented. (shrink)

Two luminaries of 20th century astrophysics were Sir James Jeans and Sir Arthur Eddington. Both took seriously the view that there is more to reality than the physical universe and more to consciousness than simply brain activity. In his Science and the Unseen World Eddington speculated about a spiritual world and that "conscious is not wholly, nor even primarily a device for receiving sense impressions." Jeans also speculated on the existence of a universal mind and a non-mechanical reality, writing in (...) his The Mysterious Universe "the universe begins to look more like a great thought than like a great machine." In his book QED Feynman discusses the situation of photons being partially transmitted and partially reflected by a sheet of glass: reflection amounting to four percent. In other words one out of every 25 photons will be reflected on average, and this holds true even for a "one at a time" flux. The four percent cannot be explained by statistical differences of the photons nor by random variations in the glass. Something is "telling" every 25th photon on average that it should be reflected back instead of being transmitted. Other quantum experiments lead to similar paradoxes. To explain how a single photon in the two-slit experiment can "know" whether there is one slit or two, Hawking and Mlodonow write: In the double-slit experiment Feynman's ideas mean the particles take paths that thread through the first slit, back out though the second slit, and then through the first again; paths that visit the restaurant that serves that great curried shrimp, and then circle Jupiter a few times before heading home; even paths that go across the universe and back. This, in Feynman's view, explains how the particle acquires the information about which slits are openŠ. It is hard to imagine a more absurd physical explanation. We can think of no way to hardwire the behavior of photons in the glass reflection or the two-slit experiments into a physical law. On the other hand, writing a software algorithm that would yield the desired result is really simple. A digital reality whose laws are software is an idea that has started to gain traction in large part thanks to an influential paper in Philosophical Quarterly by Oxford professor Nick Bostrom. Writing in the New York Times John Tierney had this to say: Until I talked to Nick Bostrom, a philosopher at Oxford University it never occurred to me that our universe might be somebody else's hobby. But now it seems quite possible. In fact, if you accept a pretty reasonable assumption of Dr. Bostrom's, it is almost a mathematical certainty that we are living in someone else's computer simulation. An alternate view is that there exists a great consciousness whose mind is the hardware, and whose thoughts are the software creating a virtual universe in which we as beings of consciousness live. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}. (shrink)

The question of which is the logic that underlies quantum physics does not have an absolute answer, but only in relation to a conventional choice of interpretation . Most of the interpretations that have been offered work within the framework of classical logic. In contrast to these, we examine the corpuscular interpretation which is assumed in the application of non-distributive logic . The experiment in which single photons pass through a Mach-Zehnder interferometer is examined, indicating the difficulty of (...) employing a realist corpuscular interpretation in this context. One way to save this interpretation would be to use non-distributive logic to analyze the experiment, but this is not satisfactory . However, the use of an alethic modal logic solves the problem, blocking the argument that put the aforementioned corpuscular interpretation into difficulty. In the discussion of the conceptual problems involved, we suggest that a stochastic corpuscular interpretation is well adapted to this logical description. The project of extending this modal logical approach to other experiments in quantum physics, and of providing a rigorous logical treatment, is left open. (shrink)

We consider QED processes in the presence of an infinitely thin and infinitely long straight string with a magnetic flux inside it. The bremsstrahlung from an electron passing by the magnetic string and the electron-positron pair production by a single photon are reviewed. Based on the exact electron and positron solutions of the Dirac equation in the external Aharonov-Bohm potential we present matrix elements for these processes. The dependence of the resulting cross sections on energies, directions, and polarizations of (...) the involved particles is discussed for low energies. (shrink)

Despite attempts to apply causal modeling techniques to quantum systems, Wood and Spekkens argue that any causal model purporting to explain quantum correlations must be fine tuned; it must violate the assumption of faithfulness. This paper is an attempt to undermine the reasonableness of the assumption of faithfulness in the quantum context. Employing a symmetry relation between an entangled quantum system and a “sideways” quantum system consisting of a single photon passing sequentially through two polarizers, I argue that Wood (...) and Spekkens’s analysis applies equally to this sideways system also. As a result, we must either reject a causal explanation in this single photon system, or the sideways system must be fine tuned. If the latter, a violation of faithfulness in the ordinary entangled system may be more tolerable than first thought. Thus, extending the classical “no fine-tuning” principle of parsimony to the quantum realm may be too hasty. (shrink)

Recently a quite stimulating paper (Heaney et al. arXiv:0911.0770v2 [quant-ph], 2010) dealing with the possibility of exploiting the nonlocal aspects of a superposition of states of a single photon appeared. We regard as greatly relevant the results which have been obtained. However we think that the presentation of the matter and the way to derive the conclusion are not fully satisfactory and do not put the necessary emphasis on some subtle basic aspects like locality and realism. In view of (...) its interest we consider it useful to reconsider the line of reasoning of Heaney et al. (in arXiv:0911.0770v2 [quant-ph], 2010) and to derive once more its results by following a procedure which seems to us more lucid and which makes fully clear the role of the various conceptual aspects of the treatment. We hope that our analysis will contribute to clarify and to deepen the interesting results of Heaney et al. (in arXiv:0911.0770v2 [quant-ph], 2010). (shrink)

The chapters published in this volume developed from presentations, and their associated discussions at a conference organised by the Scottish Branch of the British Psychological Society, held at Rothesay, Isle of Bute, Scotland in September 1987. The goal of the conference was to bring together workers across a wide area of neuropsychological research to discuss recent technological advances, developments in assessment and rehabilitation, and to address theoretical issues of current interest. Thus, the chapters in this book include contributions on the (...) use of Magnetic Resonance Imaging and Single Photon Emission Computed Tomography in neuropsychological research, studies of hemi spheric specialisation and cooperation, alcoholic and Alzheimer type dementia, prosopagnosia and facial processing, the assessment, management and rehabilitation of memory problems, the assessment of premorbid intellectual status and issues in developmental neuropsychology. Many of those engaged in research and clinical practice in neuropsychology encounter a range of topic at least as wide as this in their professional lives. The opportunity for researchers and clinicians to discuss some of the key issues in the field was invaluable and we hope that readers gain as much from the material presented here as the participants did from the meeting itself. (shrink)

In this paper we study in details a system of two weakly coupled harmonic oscillators from the point of view of Bohm’s interpretation of quantum mechanics. This system may be viewed as a simple model for the interaction between a photon and a photodetector. We obtain exact solutions for the general case. We then compute approximate solutions for the case where one oscillator is initially in its first excited state (a single photon) reaching the other oscillator in its ground (...) state (the photodetector). The approximate solutions represent the state of both oscillators after the interaction, which is not an eigenstate of the individual hamiltonians for each oscillator, and therefore the energies for each oscillator do not exist in the Copenhagen interpretation of Quantum Mechanics. We use the approximate solutions that we obtained to compute Bohmian trajectories and to study the energy transfer between the oscillators. We conclude that, even using the Bohmian view, the energy of each individual oscillator is not well defined, as the nonlocal quantum potential is not negligible even after the coupling is turned off. (shrink)

Recently highly-efficient quantum engines were devised by exploiting the stochastic energy changes induced by quantum measurement. Here we show that such an engine can be based on an interaction-free measurement, in which the meter seemingly does not interact with the measured object. We use a modified version of the Elitzur–Vaidman bomb tester, an interferometric setup able to detect the presence of a bomb triggered by a single photon without exploding it. In our case, a quantum bomb subject to a (...) gravitational force is initially in a superposition of being inside and outside one of the interferometer arms. We show that the bomb can be lifted without blowing up. This occurs when a photon traversing the interferometer is detected at a port that is always dark when the bomb is located outside the arm. The required potential energy is provided by the photon even though it was not absorbed by the bomb. A natural interpretation is that the photon traveled through the arm which does not contain the bomb—otherwise the bomb would have exploded—but it implies the surprising conclusion that the energy exchange occurred at a distance despite a local interaction Hamiltonian. We use the weak value formalism to support this interpretation and find evidence of contextuality. Regardless of interpretation, this interaction-free quantum measurement engine is able to lift the most sensitive bomb without setting it off. (shrink)

In this paper we study in details a system of two weakly coupled harmonic oscillators from the point of view of Bohm's interpretation of quantum mechanics. This system may be viewed as a simple model for the interaction between a photon and a photodetector. We obtain exact solutions for the general case. We then compute approximate solutions for the case where one oscillator is initially in its first excited state (a single photon) reaching the other oscillator in its ground (...) state (the photodetector). The approximate solutions represent the state of both oscillators after the interaction, which is not an eigenstate of the individual hamiltonians for each oscillator, and therefore the energies for each oscillator do not exist in the Copenhagen interpretation of Quantum Mechanics. We use the approximate solutions that we obtained to compute Bohmian trajectories and to study the energy transfer between the oscillators. We conclude that, even using the Bohmian view, the energy of each individual oscillator is not well defined, as the nonlocal quantum potential is not negligible even after the coupling is turned off. (shrink)

The photocycle of visual opsins is essential to maintain the light sensitivity of the retina. The early physical observations of the rhodopsin photocycle by Böll and Kühne in the 1870s inspired over a century's worth of investigations on rhodopsin biochemistry. A single photon isomerizes the Schiff‐base linked 11‐cis‐retinylidene chromophore of rhodopsin, converting it to the all‐trans agonist to elicit phototransduction through photoactivated rhodopsin (Rho*). Schiff base hydrolysis of the agonist is a key step in the photocycle, not only diminishing (...) ongoing phototransduction but also allowing for entry and binding of fresh 11‐cis chromophore to regenerate the rhodopsin pigment and maintain light sensitivity. Many challenges have been encountered in measuring the rate of this hydrolysis, but recent advancements have facilitated studies of the hydrolysis within the native membrane environment of rhodopsin. These techniques can now be applied to study hydrolysis of agonist in other opsin proteins that mediate phototransduction or chromophore turnover. In this review, we discuss the progress that has been made in characterizing the rhodopsin photocycle and the journey to characterize the hydrolysis of its all‐trans‐retinylidene agonist. (shrink)