Experimental test of local observer independence

In 1962, Eugene P. Wigner introduced a thought experiment that highlighted the incompatibility in quantum mechanics between unitary evolution and wave function reduction in a measurement. This work resulted in a class of thought experiments often called Wigner's Friend Scenarios, which have been providing insights over many frameworks and interpretations of quantum theory. Recently, a no-go theorem obtained by Daniela Frauchiger and Renato Renner brought attention back to the Wigner's Friend and its potential of putting theories to test. Many answers to this result pointed out how timing in the thought experiment could be yielding a paradox. In this work, we ask what would happen if the isolated friend in a Wigner's Friend Scenario did not share a time reference frame with the outer observer, and time should be tracked by a quantum clock. For this purpose, we recollect concepts provided by the theory of quantum reference frames and the quantum resource theory of asymmetry, to learn how to internalize time in this scenario, and introduce a model for a feasible quantum clock proposed by Mischa P. Woods, Ralph Silva and Jonathan Oppenheim, called the quasi-ideal clock. Our results have shown that no decoherent behavior comes from this approach, and the disagreement between the superobserver and its friend persists even for an imprecise clock, indicating that the source of paradox in a Wigner's Friend Scenario may be elsewhere.

According to QBism, quantum states, unitary evolutions, and measurement operators are all understood as personal judgments of the agent using the formalism. Meanwhile, quantum measurement outcomes are understood as the personal experiences of the same agent. Wigner's conundrum of the friend, in which two agents ostensibly have different accounts of whether or not there is a measurement outcome, thus poses no paradox for QBism. Indeed the resolution of Wigner's original thought experiment was central to the development of QBist thinking. The focus of this paper concerns two very instructive modifications to Wigner's puzzle: One, a recent no-go theorem by Frauchiger and Renner, and the other a thought experiment by Baumann and Brukner. We show that the paradoxical features emphasized in these works disappear once both friend and Wigner are understood as agents on an equal footing with regard to their individual uses of quantum theory. Wigner's action on his friend then becomes, from the friend's perspective, an action the friend takes on Wigner. Our analysis rests on a kind of quantum Copernican principle: When two agents take actions on each other, each agent has a dual role as a physical system for the other agent. No user of quantum theory is more privileged than any other. In contrast to the sentiment of Wigner's original paper, neither agent should be considered as in "suspended animation." In this light, QBism brings an entirely new perspective to understanding Wigner's friend thought experiments.

Considering a minimal number of assumptions and in the context of the timeless formalism, conditional probabilities are derived for subsequent measurements in the non-relativistic regime. Only unitary transformations are considered with detection processes described by generalized measurements (POVM). One-time conditional probabilities are unambiguously derived via the Gleason-Bush theorem, including for puzzling cases like the Wigner's friend scenario where their form underlines the relativity aspect of measurements. No paradoxical situations emerge and the roles of Wigner and Wigner can be seen by his friend as being in a superposition.

A fully relational quantum theory necessarily requires an account of changes of quantum reference frames, where quantum reference frames are quantum systems relative to which other systems are described. By introducing a relational formalism which identifies coordinate systems with elements of a symmetry groupG, we define a general operator for reversibly changing between quantum reference frames associated to a groupG. This generalises the known operator for translations and boosts to arbitrary finite and locally compact groups, including non-Abelian groups. We show under which conditions one can uniquely assign coordinate choices to physical systems (to form reference frames) and how to reversibly transform between them, providing transformations between coordinate systems which are `in a superposition' of other coordinate systems. We obtain the change of quantum reference frame from the principles of relational physics and of coherent change of reference frame. We prove a theorem stating that the change of quantum reference frame consistent with these principles is unitary if and only if the reference systems carry the left and right regular representations ofG. We also define irreversible changes of reference frame for classical and quantum systems in the case where the symmetry groupGis a semi-direct productG=N⋊Por a direct productG=N×P, providing multiple examples of both reversible and irreversible changes of quantum reference system along the way. Finally, we apply the relational formalism and changes of reference frame developed in this work to the Wigner's friend scenario, finding similar conclusions to those in relational quantum mechanics using an explicit change of reference frame as opposed to indirect reasoning using measurement operators.

Exploiting the tension between the two dynamics of quantum theory (QT) in the Wigner's Friend thought experiment, we point out that the standard QT leads to inconsistency in observed probabilities of measurement outcomes between two superobservers: Wigner and his Student. To avoid such inconsistent predictions of QT, we hypothesize two distinct perspectives. The first one is ``absoluteness of measurement (AoM),'' that is, any measurement process is an absolute event irrespective of other observers and yields a single outcome. The other is ``nonabsoluteness of measurement (NoM)'' as the negation of AoM. We introduce an operational approach, first with one friend and then with two spatially separated friends, to test the validity of these two perceptions in quantum theory without assuming the details of the experiment. First, we show that the set of probabilities obtainable for NoM is strictly larger than the set obtainable for AoM. We provide the simplest scenario so far, involving a single quantum preparation and one unitary operation by a superobserver that can demonstrate correlations incompatible with AoM. Remarkably, in the scenario with spatially separated observers, we present a strict hierarchy among the sets of probabilities observed in the following three theories: classical or local realist, quantum theory with AoM, and quantum theory with NoM.

Local Friendliness (LF) inequalities follow from seemingly reasonable assumptions about reality: (i) ``absoluteness of observed events'' (e.g., every observed event happens for all observers) and (ii) ``local agency'' (e.g., free choices can be made uncorrelated with other events outside their future light cone). Extended Wigner's Friend Scenario (EWFS) thought experiments show that textbook quantum mechanics violates these inequalities. Thus, experimental evidence of these violations would make these two assumptions incompatible. In [Nature Physics 16, 1199 (2020)], the authors experimentally implemented an EWFS, using a photonic qubit to play the role of each of the ``friends'' and measured violations of LF. One may question whether a photonic qubit is a physical system that counts as an ``observer'' and thereby question whether the experiment's outcome is significant. Intending to measure increasingly meaningful violations, we propose using a statistical measure called the ``branch factor'' to quantify the ``observerness'' of the system. We then encode the EWFS as a quantum circuit such that the components of the circuit that define the friend are quantum systems of increasing branch factor. We run this circuit on quantum simulators and hardware devices, observing LF violations as the system sizes scale. As errors in quantum computers reduce the significance of the violations, better quantum computers can produce better violations. Our results extend the state of the art in proof-of-concept experimental violations from branch factor 0.0 to branch factor 16.0. This is an initial result in an experimental program for measuring LF violations at increasingly meaningful branch factors using increasingly more powerful quantum processors and networks. We introduce this program as a fundamental science application for near-term and developing quantum technology.

In the libertarian “agent causation” view of free will, free choices are attributable only to the choosing agent, as opposed to a specific cause or causes outside the agent. An often-repeated claim in the philosophical literature on free will is that agent causation necessarily implies lawlessness, and is therefore “antiscientific.” That claim is critiqued and it is argued, on the contrary, that the volitional powers of a free agent need not be viewed as anomic, specifically with regard to the quantum statistical law (the Born Rule). Assumptions about the role and nature of causation, taken as bearing on volitional agency, are examined and found inadequate to the task. Finally, it is suggested that quantum theory may constitute precisely the sort of theory required for a nomic grounding of libertarian free will. Born Rule; free will; anomic action 1. The Born Rule and Free Choices The agent causation (AC) theory of free will holds that truly free human choices are attributable not to specific events or causes external to a choosing agent, nor to desires or other internal psychological influences, but only to the volitional power of the choosing agent. In effect, that is what “volition” means according to AC. But the latter is currently a minority view. The more “mainstream,” conservative approach to the problem of free will is to assert that “free will” simply means acting in accordance with our desires in a way that is free of external constraints. This view is called compatibilism, because it was developed specifically to be compatible with deterministic laws. In effect, it defines the term “free will’ in such a way that we can say we are making free choices as to how to behave even when all of our behaviors are fully determined by past causes and inexorable deterministic laws (or even fated in the sense of being elements of a “block world” in which the future exists in the same way as the past and present). In contrast, AC is a form of incompatibilism, which denies that free will is compatible with determinism. It holds that in order for us to have free will, the world must be fundamentally indeterministic. AC is the libertarian form of incompatibilism; it asserts that the world is in fact indeterministic, and that we do have free will. Our own volitional power is taken as the primary cause of our choices. The complementary form of incompatibilism is to assert that the world is deterministic and therefore to deny that we have free will. It is often asserted that the agent causation view requires lawlessness, and is necessarily ”antiscientific.” For example, the entry on incompatibilism in the Stanford Encyclopedia

What is fundamentally quantum? We argue that most of the features, problems, and paradoxes – such as the measurement problem, the Wigner's friend paradox and its proposed solutions, single particle nonlocality, and no-cloning – allegedly attributed to quantum physics have a classical analogue if one is to interpret classical physics as fundamentally indeterministic. What really characterizes non-classical effects are incompatible physical quantities, which, in quantum quantum theory are associated to the fundamental constant ℏ.

A necessary condition for the probabilities of a set of events to exhibit Bell non-locality or Kochen-Specker contextuality is that the graph of exclusivity of the events contains induced odd cycles with five or more vertices, called odd holes, or their complements, called odd antiholes. From this perspective, events whose graph of exclusivity are odd holes or antiholes are the building blocks of contextuality. For any odd hole or antihole, any assignment of probabilities allowed by quantum theory can be achieved in specific contextuality scenarios. However, here we prove that, for any odd hole, the probabilities that attain the quantum maxima cannot be achieved in Bell scenarios. We also prove it for the simplest odd antiholes. This leads us to the conjecture that the quantum maxima for any of the building blocks cannot be achieved in Bell scenarios. This result sheds light on why the problem of whether a probability assignment is quantum is decidable, while whether a probability assignment within a given Bell scenario is quantum is, in general, undecidable. This also helps to understand why identifying principles for quantum correlations is simpler when we start by identifying principles for quantum sets of probabilities defined with no reference to specific scenarios. This article is part of the theme issue 'Quantum contextuality, causality and freedom of choice'.

An impossibility theorem for parameter independent hidden variable theories

هدفت الدراسة إلى التأكد من مدى تحقيق مقياس كاليفورنيا للدافعية العقلية لافتراضات نظرية الاستجابة للمفردة، والتحقق من مطابقة مفردات كاليفورنيا للدافعية العقلية لنموذج سلم التقدير، وتمثلت أداة الدراسة في مقياس كاليفورنيا للدافعية العقلية الذي أعده كلا من (Giancarlo& Urdan, 2004) والمكون من (24) مفردة موزعة على أربعة أبعاد (التوجه نحو التعلم، الحل الابداعي للمشكلات، التركيز الذهني، التكامل المعرفي)، وقد بلغ عدد المشاركين في الدراسة (783) طالبا وطالبة من بين طلاب المرحلة الثانوية، وقد استخدمت الباحثتان البرامج الحاسوبية المتمثلة في (SPSS. V.22), جي ميتريك (jMetrik. V.4.1.1), باراسكال (PARSCALE-4.1.28303.1)، وتوصلت الدراسة إلى تحقق افتراضات نظرية الاستجابة للمفردة في استجابات طلاب المرحلة الثانوية على مقياس كاليفورنيا للدافعية العقلية، عدم ملاءمة بعض مفردات مقياس كاليفورنيا للدافعية العقلية لدى طلاب المرحلة الثانية لنموذج سلم التقدير (3 مفردات) وذلك بالاعتماد على مؤشر مربع كاي (CHI.SQ)، وتراوحت قيم بارامترات الصعوبة لمفردات المقياس بين (-0,744)، و(0,982)، بمتوسط (0,151) وانحراف معياري (1,110)، وكانت قيم قدرات الأفراد الناتجة من تدريج مفردات مقياس كاليفورنيا للدافعية العقلية لدى طلاب المرحلة الثانوية وفق نموذج سلم التقدير بين (-0,4176: 2,0219)، بمتوسط (0,445) وانحراف معياري قدره (0,367) وتتمحور معظمها حول القيمة المتوسطة، وكانت نسب الثبات الهامشي لمقياس الدافعية العقلية وفق نموذج سلم التقدير ما بين (0,733: 0,800).

In this letter, we point to three widely accepted challenges that the quantum theory, quantum information, and quantum foundations communities are currently facing: indeterminism, the semantics of conditional probabilities, and the spooky action at a distance. We argue that these issues are fundamentally rooted in conflations commonly made between causal dependencies, counterfactual dependencies, and statistical dependencies. We argue that a simple, albeit somewhat uncomfortable shift of viewpoint leads to a way out of the impossibility to extend the theory beyond indeterminism, and towards the possibility that sound extensions of quantum theory, possibly even deterministic yet not super-deterministic, will emerge in the future. The paradigm shift, which we present here, involves a non-trivial relaxation of the commonly accepted mathematical definition of free choice, leading to non-Nashian free choice, more care with the choice of probabilistic notations, and more rigorous use of vocabulary related to causality, counterfactuals, and correlations, which are three concepts of a fundamentally different nature.

Quantum theory predicts the existence of genuinely tripartite-entangled states, which cannot be obtained from local operations over any bipartite-entangled states and unlimited shared randomness. Some of us recently proved that this feature is a fundamental signature of quantum theory. The state |GHZ_{3}⟩=(|000⟩+|111⟩)/sqrt[2] gives rise to tripartite quantum correlations that cannot be explained by any causal theory limited to bipartite nonclassical common causes of any kind (generalizing entanglement) assisted with unlimited shared randomness. Hence, any conceivable physical theory that would reproduce quantum predictions will necessarily include genuinely tripartite resources. In this Letter, we verify that such tripartite correlations are experimentally achievable. We derive a new device-independent witness capable of falsifying causal theories wherein nonclassical resources are merely bipartite. Using a high-performance photonic |GHZ_{3}⟩ state with fidelities of 0.9741±0.002, we provide a clear experimental violation of that witness by more than 26.3 standard deviations, under the locality and fair sampling assumption. We generalize our Letter to the |GHZ_{4}⟩ state, obtaining correlations that cannot be explained by any causal theory limited to tripartite nonclassical common causes assisted with unlimited shared randomness.

Rasch analysis informed modifications to the Work Instability Scale for Rheumatoid Arthritis for use in work-related upper limb disorders

Crime and violence are fundamental threats to human security. Safety from crime and violence including the resulting fear of insecurity are not only, increasingly recognized as international public good, but also a basic human right. During this decade, over 60% of all urban residents in developing countries have been documented as focal points of victims of crime. The distribution of crime is not random in time and space. Interventions for this skewed crime are theoretically informed by the crime strategies used by the perpetrators. The general objective of this study was to analyze crime management strategies and their effect on insecurity within Mukuru Kayaba Slums, Nairobi County. This study was guided by the following specific objectives; to assess the influence of crime prevention strategies on insecurity, to investigate the relationship between crime detection strategies and insecurity slums, to evaluate crime deterrence strategies on insecurity within Mukuru Kayaba slums and to explore crime-reporting strategies on insecurity. The study was guided by the general strain theory, and broken window theory. The study adopted descriptive research design. The study targeted population was 557 police officers of all working in police commands within Embakasi Police Division and crime victims which represented the entire police service as well as key informants from Nyumba Kumi and Community Policing Committees. A sample size of 226 was selected was purposively selected using multi stage sampling. This study used a structured questionnaire to collect primary data in line with the research study objectives Mean and standard deviations were used for descriptive analysis. The study carried out tests of regression assumptions; normality using Q-Q plot, linearity using correlation coefficient r, test of independence using Durbin Watson d-statistic and test of multicollinearity Variance Inflation Factors, and test of homoscedasticity using p-plot. Based on the test of regression outputs, multiple linear regression was used for inferential analysis. This study generated a Model fitness (R-Square of.508%), implying that approximately 50.8% of the variation in insecurity could be explained by this model. Further the ANOVA statistics were; F value of 3.775 and p-value of.008, implying a statistically significant relationship between crime management strategies and insecurity. Based on these findings, the study concluded that is a significant relationship between crime prevention strategies, crime detection strategies, and crime reporting strategies and insecurity. On the other hand, the study concluded that despite its importance in theory management, there was no statistically significant relationship between crime deterrence and insecurity. This study recommend that in order to reduce insecurity in Mukuru slums and in similar contexts, crime detection, crime prevention and crime reporting should be given priority in that order. Further, the study recommends that although appears that crime deterrence strategies is less elastic to insecurity and hence a lot of resources should be prioritized to other strategies and less on crime deterrence. The civil society and private sector is paramount in crime management within Mukuru Kayaba Slum.