Biblical theology is confronted with tensions between love and justice. There are sometimes attempts to avoid these tensions by dissolving one side of the opposing concept. One such attempt is to identify love and mercy as the essence of Christian theology, overcoming law and reciprocal justice. However, such a dissolution is irresponsible not only ethically, but also theologically--as the discussion in a number of the studies collected in the present volume will demonstrate.

As the implementation of new approaches and procedures of medical ethics is as complex and resource-consuming as in other fields, strategies and activities must be carefully planned to use the available means and funds responsibly. Which facilitators and barriers influence the implementation of a medical ethics decision-making model in daily routine? Up to now, there has been little examination of these factors in this field. A medical ethics decision-making model called METAP was introduced on three intensive care units and two (...) geriatric wards. An evaluation study was performed from 7 months after deployment of the project until two and a half years. Quantitative and qualitative methods including a questionnaire, semi-structured face-to-face and group-interviews were used. Sixty-three participants from different professional groups took part in 33 face-to-face and 9 group interviews, and 122 questionnaires could be analysed. The facilitating factors most frequently mentioned were: acceptance and presence of the model, support given by the medical and nursing management, an existing or developing ethics culture, perception of a need for a medical ethics decision-making model, and engaged staff members. Lack of presence and acceptance, insufficient time resources and staff, poor inter-professional collaboration, absence of ethical competence, and not recognizing ethical problems were identified as inhibiting the implementation of the METAP model. However, the results of the questionnaire as well as of explicit inquiry showed that the respondents stated to have had enough time and staff available to use METAP if necessary. Facilitators and barriers of the implementation of a medical ethics decision-making model are quite similar to that of medical guidelines. The planning for implementing an ethics model or guideline can, therefore, benefit from the extensive literature and experience concerning the implementation of medical guidelines. Lack of time and staff can be overcome when people are convinced that the benefits justify the effort. (shrink)

Abstract: A 1991 article by psychologist John D. Carter offers an underdeveloped insight that typologies for relating science and religion might be fruitfully formulated in discipline-specific perspectives. This essay thus covers a specifically theological perspective only briefly outlined in Carter, and it expands four models that theologians have used to relate religion and science. This essay renames these models and expands their implications, especially for addressing the behavioral sciences. (1) The contrarian model generally opposes science, (2) the apologetic makes theology (...) congenial to science, (3) the correlational holds both disciplines in tension, and (4) the synthetic attempts a grand unification of them. Arguing from the theologian's perspective, this essay is intended to demonstrate that different models/methods for relating science and religion are really reflections of deeper religious attitudes and argues that the task for which a method is employed ultimately determines its adequacy within that attitude's constraints. (shrink)

This essay argues that the American psychologist and philosopher William James should be viewed in the Lutheran Reformation’s tradition because this viewpoint offers the hermeneutical key to his philosophy of religion. Though James obviously didn’t ascribe to biblical authority, he expressed the following religious sensibilities made possible by Martin Luther and his contemporaries: 1) challenge of prevailing systems, 2) anti-rationalism, 3) being pro-religious experience and dynamic belief, 4) need for a personal, caring God, and also 5) a gospel of religious (...) comfort. This essay asks, in one specifi c form, how religious concerns can hold steady over time but cause very different expressions of faith. (shrink)

This essay argues that the American psychologist and philosopher William James should be viewed in the Lutheran Reformation’s tradition because this viewpoint offers the hermeneutical key to his philosophy of religion. Though James obviously didn’t ascribe to biblical authority, he expressed the following religious sensibilities made possible by Martin Luther and his contemporaries: 1) challenge of prevailing systems, 2) anti-rationalism, 3) being pro-religious experience and dynamic belief, 4) need for a personal, caring God, and also 5) a gospel of religious (...) comfort. This essay asks, in one specific form, how religious concerns can hold steady over time but cause very different expressions of faith. (shrink)

A 62-year-old female with Huntington’s disease presented after a suicide attempt. Her advance directive stated that she did not want intubation or resuscitation, which her family acknowledged and supported. Despite these directives, she was resuscitated in the emergency department and continued to state that she would attempt suicide again. Her suicidality in the face of a chronic and advancing illness, and her prolonged consistency in her desire to take her own life, left careproviders wondering how to provide ethical, respectful care (...) to this patient. Tension between the ethical principles of autonomy and beneficence is central in this case. The patient’s narrative demonstrated that her suicide was an autonomous decision, free from coercion or disordered thinking from mental illness. Beneficence then would seem to necessitate care aligned with the patient’s desire to end her life, which created ethical uneasiness for her family and careproviders. The case highlights several end-of-life ethical considerations that have received much recent attention. With ongoing discussions about the legalization of aid in dying across the country, caregivers are challenged to understand what beneficence means in people with terminal illnesses who want a say in their death. This case also highlights the profound moral distress of families and careproviders that arises in such ethically challenging scenarios. (shrink)

Therapieentscheidungen lösen in klinischen Teams häufig Unsicherheiten und Konflikte aus, insbesondere wenn es um schwerkranke Patienten geht. Fallen Entscheidungen vornehmlich situationsgeleitet, sind bestimmte Patientengruppen einem Risiko der Unter-, Über- oder Ungleichversorgung ausgesetzt. Der Metap-Leitfaden unterstützt Ärzte, Pfleger und Therapeuten daher in ihrer ethisch reflektierten Entscheidungskompetenz mit verschiedenen Orientierungs- und Entscheidungsinstrumentarien. Diese berücksichtigen eine gerechte Zuteilung der Ressourcen.

In this paper we assume that ‘theory’ is important for Clinical Ethics Support Services (CESS). We will argue that the underlying implicit theory should be reflected. Moreover, we suggest that the theoretical components on which any clinical ethics support (CES) relies should be explicitly articulated in order to enhance the quality of CES.A theoretical framework appropriate for CES will be necessarily complex and should include ethical (both descriptive and normative), metaethical and organizational components. The various forms of CES that exist (...) in North-America and in Europe show their underlying theory more or less explicitly, with most of them referring to some kind of theoretical components including ‘how-to’ questions (methodology), organizational issues (implementation), problem analysis (phenomenology or typology of problems), and related ethical issues such as end-of-life decisions (major ethical topics).In order to illustrate and explain the theoretical framework that we are suggesting for our own CES project METAP, we will outline this project which has been established in a multi-centre context in several healthcare institutions. We conceptualize three ‘pillars’ as the major components of our theoretical framework: (1) evidence, (2) competence, and (3) discourse. As a whole, the framework is aimed at developing a foundation of our CES project METAP.We conclude that this specific integration of theoretical components is a promising model for the fruitful further development of CES. (shrink)

In this paper we assume that ‘theory’ is important for Clinical Ethics Support Services (CESS). We will argue that the underlying implicit theory should be reflected. Moreover, we suggest that the theoretical components on which any clinical ethics support (CES) relies should be explicitly articulated in order to enhance the quality of CES.A theoretical framework appropriate for CES will be necessarily complex and should include ethical (both descriptive and normative), metaethical and organizational components. The various forms of CES that exist (...) in North‐America and in Europe show their underlying theory more or less explicitly, with most of them referring to some kind of theoretical components including ‘how‐to’ questions (methodology), organizational issues (implementation), problem analysis (phenomenology or typology of problems), and related ethical issues such as end‐of‐life decisions (major ethical topics).In order to illustrate and explain the theoretical framework that we are suggesting for our own CES project METAP, we will outline this project which has been established in a multi‐centre context in several healthcare institutions. We conceptualize three ‘pillars’ as the major components of our theoretical framework: (1) evidence, (2) competence, and (3) discourse. As a whole, the framework is aimed at developing a foundation of our CES project METAP.We conclude that this specific integration of theoretical components is a promising model for the fruitful further development of CES. (shrink)

Ethische Leitlinien für die klinische Praxis erfreuen sich zunehmender Beliebtheit. Damit klinisch-ethische Leitlinien aber überhaupt erfolgreich wirksam werden können, ist noch Pionierarbeit zu leisten. Solche Leitlinien müssen wissenschaftlich stärker fundiert und ihre praktische Anwendbarkeit muss verbessert werden. In dieser Arbeit werden die ersten Schritte des Projekts METAP zur methodischen Entwicklung und praktischen Implementierung einer Leitlinie für eine patientengerechte Versorgung am Krankenbett beschrieben und zur Diskussion gestellt. Das Projekt orientiert sich methodisch an der Entwicklung medizinischer Leitlinien und generiert damit eine forschungs- (...) und konsensgestützte Leitlinie, die systematischer Evaluation und Modifikation unterliegt und Rechenschaft über ihre wissenschaftliche Fundierung gibt. Zusätzlich zur Leitlinie bietet das Projekt in der Form eines Handbuchs ein Entscheidungsfindungsverfahren an, welches unter anderem deliberative Aspekte unterstützt. Das Handbuch konzentriert sich auf ethische Fragen der Mikroallokation und liefert darüber hinaus Informationen über empirische, ethische und rechtliche Grundlagen für Therapieentscheidungen. Anhand eines Eskalationsmodells können unterschiedliche Instrumente nach Bedarf als ethische Lösungsstrategien eingesetzt werden, von der Kurzfassung im Kitteltaschenformat („Leporello“) mit den wichtigsten Fakten, weiterführenden Texten und Empfehlungen mit normativen und prozeduralen Hinweisen, über stationsinterne Lösungsversuche bis hin zum Ethikkonsil. Klinische Partner sind von Beginn an aktiv in den Entwicklungsprozess eingebunden und verbessern so die Praxistauglichkeit und Akzeptanz sowie die Ausrichtung des Instrumentariums an den tatsächlichen Bedürfnissen. Dieses partnerschaftliche, partizipative Vorgehen scheint eine wichtige Voraussetzung dafür zu sein, dass METAP in der Klinik Fuß fassen konnte. (shrink)

Recently, ethical guidelines for clinical practice have gained increased popularity, but in order to become useful they require more pioneer’s work. Clinical-ethical guidelines need to be based on a scientific foundation and their practicability must be improved. We present and put to discussion the initial steps of the METAP Project about the development and practical implementation of a clinical-ethical guideline dedicated to a fair resource-allocation at the bedside. -/- With its methodological orientation, the project represents a guideline which is based (...) on both research and consensus-building, undergoing systematic evaluation and modification. In addition to the guideline, the project comes with a manual (a tool kit) including a procedural instrument for making decisions supporting deliberative aspects. It focuses on issues of micro-allocation; furthermore, it provides empirical, ethical and legal basics for making fair treatment decisions that should help to prevent overtreatment, undertreatment or discrimination in patient care. We propose an Escalation Model with various instruments serving as problem solving strategies that correspond to the respective needs; these instruments include a pocket-summary (“Leporello”) with the most important facts; further reading material; normative and procedural recommendations; ward-specific strategies, and also the option of clinical ethics consultation. -/- Clinical partners have been actively involved in the developmental process from the beginning and contributed to the practical applicability, acceptance and a valid need-orientation of the whole tool kit. This partnership and the participatory approach seem to have helped METAP to gain a foothold in the clinic. (shrink)

Medizinethische Entscheidungsfindungsmodelle müssen nachweisen können, weshalb die mit ihnen getroffenen Entscheidungen richtig oder zumindest „belastbar“ sind. Hierfür sind theoretische Rechtfertigungsansätze aus der Ethik unverzichtbar. Der Klinischen Ethik wird aber mitunter ein Mangel an theoretischer Fundierung vorgeworfen. Um diesem Vorwurf entgegenzutreten, soll unter Bezugnahme auf ein Projekt der Klinischen Ethik („METAP“) die ethische Unterstützung in Form der ethischen Fallbesprechung und der Ethikkonsultation mittels Prinzipienethik und Diskursethik gerechtfertigt werden. Prinzipienethik und Diskursethik können einander über das Medium der ethischen Fallbesprechung oder Ethikkonsultation fruchtbar (...) ergänzen. So können einige theoretische und praktische Schwächen der beiden Ansätze durch den jeweils anderen abgefedert werden. Die Diskursethik übernimmt bspw. die Sicherung der ethischen Gültigkeit von moralischen Entscheidungen bzw. Handlungsnormen und vermindert dadurch ein Rechtfertigungsdefizit, welches bei einem rein prinzipienorientierten Verfahren auftritt. Umgekehrt antwortet die Prinzipienethik u. a. auf Fragen der ethischen Angemessenheit und dient v. a. der adäquaten Einzelfallentscheidung. Durch die Integration des einen Ansatzes in den anderen ist eine umfassendere Rechtfertigungsleistung erzielbar als bei einem alleinigen Einsatz von Prinzipienethik oder Diskursethik. Selbst wenn einige Herausforderungen bestehen bleiben und auch das integrierte Modell moralische Dissense nicht immer verhindern kann, vermag es durch seine „doppelte“ Absicherung (Prinzipien und Diskurs) ein praktisches Vertrauen in die getroffene ethische Entscheidung zu stärken und so der Klinischen Ethik mehr „Robustheit“ zu geben, als sie bisher besitzt. (shrink)

Eine patientengerechte Versorgung ist ein hohes Ziel. Unangemessene Behandlung wie Unter- oder Überversorgung zu erkennen und zu vermeiden, stellt Ärztinnen/Ärzte und Pflegende am Krankenbett vor schwierige Entscheidungen. Hier ist die Entwicklung von praxistauglichen Orientierungshilfen angezeigt, die wissenschaftlichen Kriterien genügen und nicht allein auf Konsens beruhen. Die vorliegende Arbeit versucht, zentrale Normen zur Vermeidung von Über- und Unterversorgung zu formulieren und theoretisch zu fundieren. Dafür wird auf Basis einer Interessen-basierten Ethik eine Graduierung der Autonomie vorgenommen, indem zwischen schwacher und starker Autonomie (...) unterschieden wird. (shrink)

Eine patientengerechte Versorgung ist ein hohes Ziel. Unangemessene Behandlung wie Unter- oder Überversorgung zu erkennen und zu vermeiden, stellt Ärztinnen/Ärzte und Pflegende am Krankenbett vor schwierige Entscheidungen. Hier ist die Entwicklung von praxistauglichen Orientierungshilfen angezeigt, die wissenschaftlichen Kriterien genügen und nicht allein auf Konsens beruhen. Die vorliegende Arbeit versucht, zentrale Normen zur Vermeidung von Über- und Unterversorgung zu formulieren und theoretisch zu fundieren. Dafür wird auf Basis einer Interessen-basierten Ethik eine Graduierung der Autonomie vorgenommen, indem zwischen schwacher und starker Autonomie (...) unterschieden wird. (shrink)

ZusammenfassungMedizinethische Entscheidungsfindungsmodelle müssen nachweisen können, weshalb die mit ihnen getroffenen Entscheidungen richtig oder zumindest „belastbar“ sind. Hierfür sind theoretische Rechtfertigungsansätze aus der Ethik unverzichtbar. Der Klinischen Ethik wird aber mitunter ein Mangel an theoretischer Fundierung vorgeworfen. Um diesem Vorwurf entgegenzutreten, soll unter Bezugnahme auf ein Projekt der Klinischen Ethik („METAP“) die ethische Unterstützung in Form der ethischen Fallbesprechung und der Ethikkonsultation mittels Prinzipienethik und Diskursethik gerechtfertigt werden. Prinzipienethik und Diskursethik können einander über das Medium der ethischen Fallbesprechung oder Ethikkonsultation fruchtbar (...) ergänzen. So können einige theoretische und praktische Schwächen der beiden Ansätze durch den jeweils anderen abgefedert werden. Die Diskursethik übernimmt bspw. die Sicherung der ethischen Gültigkeit von moralischen Entscheidungen bzw. Handlungsnormen und vermindert dadurch ein Rechtfertigungsdefizit, welches bei einem rein prinzipienorientierten Verfahren auftritt. Umgekehrt antwortet die Prinzipienethik u. a. auf Fragen der ethischen Angemessenheit und dient v. a. der adäquaten Einzelfallentscheidung. Durch die Integration des einen Ansatzes in den anderen ist eine umfassendere Rechtfertigungsleistung erzielbar als bei einem alleinigen Einsatz von Prinzipienethik oder Diskursethik. Selbst wenn einige Herausforderungen bestehen bleiben und auch das integrierte Modell moralische Dissense nicht immer verhindern kann, vermag es durch seine „doppelte“ Absicherung (Prinzipien und Diskurs) ein praktisches Vertrauen in die getroffene ethische Entscheidung zu stärken und so der Klinischen Ethik mehr „Robustheit“ zu geben, als sie bisher besitzt. (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)

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)

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)

The transactional interpretation of quantum mechanics, following the time-symmetric formulation of electrodynamics, uses retarded and advanced solutions of the Schrödinger equation and its complex conjugate to understand quantum phenomena by means of transactions. A transaction occurs between an emitter and a specific absorber when the emitter has received advanced waves from all possible absorbers. Advanced causation always raises the specter of paradoxes, and it must be addressed carefully. In particular, different devices involving contingent absorbers or various types of interaction-free measurements (...) have been proposed as threatening the original version of the transactional interpretation. These proposals will be analyzed by examining in each case the configuration of absorbers and, in the special case of the so-called quantum liar experiment, by carefully following the development of retarded and advanced waves through the Mach-Zehnder interferometer. We will show that there is no need to resort to the hierarchy of transactions that some have proposed, and will argue that the transactional interpretation is consistent with the block-universe picture of time. (shrink)

The effective-photon hypothesis postulates a photon energy variable with light intensity according to a relation of the form ε=hv/[1−β 0 f(I)]=hv 1 . This hypothesis has been subjected to direct experimental test. A Mach-Zehnder interferometer is illuminated with aQ-spoiled Nd:glass laser and the time history of the interference fringes is recorded with an image converter camera. The experimental results show that indeed the laser pulse is not monochromatic and that a large frequency change occurs with light intensity. In addition, (...) the analysis of the results indicates that the principle of conservation of energy is not in contradiction with the hypothesis of “effective photon,” provided photons can exchange energy among themselves. (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.

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.

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)

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.

The operational definition of a weak value for a quantum mechanical system involves the limit of the weak measurement strength tending to zero. I study how this limit compares to the situation for the undisturbed system. Under certain conditions, which I investigate, this limit is discontinuous in the sense that it does not merge smoothly to the Hilbert space description of the undisturbed system. Hence, in these discontinuous cases, the weak value does not represent the undisturbed system. As a result, (...) conclusions drawn from such weak values regarding the properties of the studied system cannot be upheld. Examples are given. (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)

O experimento de Afshar foi proposto recentemente como sendo uma violação do princípio de complementaridade. Reconhecendo a novidade trazida pelo experimento, argumentamos que ele permite um refinamento de tal princípio, a partir do estabelecimento de dois pontos: (1) a possibilidade de modificar o "tipo" de fenômeno (onda ou partícula) sem alterar o estado quântico, e (2) a constatação de que o tipo de fenômeno, associado a um quantum detectado, refere-se a um trecho determinado percorrido pelo objeto quântico. O primeiro ponto (...) é explorado em interferômetros de Mach-Zehnder, com dispositivos de polarização e na montagem dupla de Unruh. O segundo ponto salienta que um fenômeno pode ser corpuscular com respeito a uma região e ondulatório com respeito a outra, estando a novidade de Afshar na proposta de uma maneira de constatar ambos simultaneamente. A restrição (1) acaba tendo um efeito desprezível no experimento de Afshar. Afshar's experiment was recently proposed as a violation of the principle of complementarity. Acknowledging the novelty brought by the experiment, we argue that it allows a refinement of this principle, with the establishment of two points: (1) the possibility of modifying the "type" of phenomenon (wave or particle) without changing the quantum-mechanical state, and (2) the recognition that the type of phenomenon, associated to a detected quantum, refers to a specific region traversed by the quantum object. The first point is explored in Mach-Zehnder interferometers, with polarization devices and in Unruh's double setup. The second point emphasizes that a phenomenon can be corpuscular with respect one region and undulatory with respect to another. Afshar's originality lies in his proposal of a way of ascertaining both simultaneously. Restriction (1) turns out having a negligible effect in Afshar's experiment. (shrink)

Quantum mechanical weak values of projection operators have been used to answer which-way questions, e.g. to trace which arms in a multiple Mach–Zehnder setup a particle may have traversed from a given initial to a prescribed final state. I show that this procedure might lead to logical inconsistencies in the sense that different methods used to answer composite questions, like “Has the particle traversed the way X or the way Y?”, may result in different answers depending on which methods (...) are used to find the answer. I illustrate the problem by considering some examples: the “quantum pigeonhole” framework of Aharonov et al., the three-box problem, and Hardy’s paradox. To prepare the ground for my main conclusion on the incompatibility in certain cases of weak values and logic, I study the corresponding situation for strong/projective measurements. In this case, no logical inconsistencies occur provided one is always careful in specifying exactly to which ensemble or sample space one refers. My results cast doubts on the utility of quantum weak values in treating cases like the examples mentioned. (shrink)

We propose a Quantum Field Theory description of beams on a Mach–Zehnder interferometer and apply the method to describe Interaction Free Measurements, concluding that there is a change of momentum of the fields in IFMs. Analysing the factors involved in the probability of emission of low-energy photons, we argue that they do not yield meaningful contributions to the probabilities of the IFMs.

Femtosecond laser microfabrication has emerged in the last decade as a powerful technique for direct inscription of low loss optical waveguides in practically any transparent dielectric substrate, showing outstanding versatility. Prototyping of new devices is made rapid, cheap and easy: optical circuits are written directly buried in the substrate, using the laser beam as an optical pen, without any need of costly masks as required by conventional photolithography. Many proof-of-principle demonstrations of integrated optics can be obtained, including splitters, directional couplers, (...) and Mach–Zehnder interferometers. Actually, the road towards applications has just been opened, and the unique capabilities of femtosecond laser micromachining will enable achievements inconceivable with other technologies. In this work, the femtosecond laser fabrication technique is discussed, together with its application to the realization of integrated photonic quantum circuits. (shrink)

Afshar et al. claim that their experiment shows a violation of the complementarity inequality. In this work, we study their claim using a modified Mach-Zehnder setup that represents a simpler version of the Afshar experiment. We find that our results are consistent with Afshar et al. experimental findings. However, we show that within standard quantum mechanics the results of the Afshar experiment do not lead to a violation of the complementarity inequality. We show that their claim originates from a (...) particular technique they use to analyze their results. In their analysis, they assume a classical concept, that particles have a definite trajectory before detection, thus, they obtain which-way information by particle detection plus path extrapolation by applying momentum conservation. This analysis technique is standard in experimental particle physics. Important discoveries such as the detection of vector bosons have been made through the application of this technique. We note that particle detection plus path extrapolation is a suitable technique within de Broglie-Bohm theory of quantum mechanics. (shrink)