Nonlocality and entanglement are now generally accepted as a fundamental finding of quantum theory, empirically confirmed beyond any doubt. Quite to the contrary, extensions to macroscopic systems (macro‐entanglement) have scarcely been analysed. It is the purpose of this paper to study conditions under which macro‐entanglement may occur, but also situations in which it can be jeopardized. The crucial new term for a theoretical understanding is “common prearranged context.” Two entangled entities may have a common historic, biographic or organizational context—which means that they are both involved in the same organized process. An existing macro‐entanglement cannot simply be annihilated, but it can be disturbed by competing effects at the same level. Practical consequences for special tests (randomized double‐blind controlled tests) are discussed as an example.
Nonlocality and entanglement are now generally accepted as a fundamental finding of quantum theory, empirically confirmed beyond any doubt. Quite to the contrary, extensions to macroscopic systems (macro‐entanglement) have scarcely been analysed. It is the purpose of this paper to study conditions under which macro‐entanglement may occur, but also situations in which it can be jeopardized. The crucial new term for a theoretical understanding is “common prearranged context.” Two entangled entities may have a common historic, biographic or organizational context—which means that they are both involved in the same organized process. An existing macro‐entanglement cannot simply be annihilated, but it can be disturbed by competing effects at the same level. Practical consequences for special tests (randomized double‐blind controlled tests) are discussed as an example.
Whereas entanglement and nonlocality belong to the fundamental findings of quantum theory, possible extensions to macroscopic systems outside the quantum laboratory are scarcely studied. This paper analyses conditions for entanglement to occur on a macrophysical level. An empirical basis is given by historic episodes and modern quantitative data. Theoretical understanding can start from the concept of perspective notions; the crucial new term is "common prearranged context", which characterizes the preparation to be made in advance (or naturally given conditions) in order to enable entanglement. A mathematical formalization is possible and gives some insight about how to handle perspective notions. 1. Entanglement in Quantum Theory and on a Macrophysical Level Entanglement and nonlocality belong to the eminent findings of modern quantum theory, confirmed experimentally beyond any doubt, and also by the functioning of quantum communication. Some years after the famous experiments by Aspect et al., 3 the idea was sketched that EPR correlatedness could be generalized beyond the original domain. 4 Along this line, series of fascinating experiments were performed inside the quantum laboratories. 5
Introduction The historical development of scientific progress teaches us that every theory that was established and broadly accepted at a certain time was later inevitably replaced by a deeper and more fundamental theory of which the old one remains a special case. One celebrated example is Newtonian (classical) mechanics, which was superseded by quantum mechanics at the beginning of the last century. It is natural to ask whether in a similar manner there could be logically consistent theories that are more generic than quantum theory itself. It could then turn out that quantum mechanics is an effective description of such a theory, only valid within our current restricted domain of experience. At present, quantum theory has been tested against very specific alternative theories that, both mathematically and in their concepts, are distinctly different. Instances of such alternative theories are non-contextual hidden-variable theories [1], local hidden-variable theories [2], crypto-nonlocal hidden-variable theories [3, 4], or some nonlinear variants of the Schrödinger equation [5–8]. Currently, many groups are working on improving experimental conditions to be able to test alternative theories based on various collapse models [9–14]. The common trait of all these proposals is to suppress one or the other counterintuitive feature of quantum mechanics and thus keep some of the basic notions of a classical worldview intact. Specifically, hidden-variable models would allow us to preassign definite values to outcomes of all measurements; collapse models are mechanisms for restraining superpositions between macroscopically distinct states, and nonlinear extensions of the Schrödinger equation may admit more localized solutions for wave-packet dynamics, thereby resembling localized classical particles.
Macroscopic quantum phenomena refer to quantum features in objects of 'large' sizes, systems with many components or degrees of freedom, organized in some ways where they can be identified as macroscopic objects. This emerging field is ushered in by several categories of definitive experiments in superconductivity, electromechanical systems, Bose-Einstein condensates and others. Yet this new field which is rich in open issues at the foundation of quantum and statistical physics remains little explored theoretically (with the important exception of the work of A J Leggett [1], while touched upon or implied by several groups of authors represented in this conference. Our attitude differs in that we believe in the full validity of quantum mechanics stretching from the testable micro to meso scales, with no need for the introduction of new laws of physics.) This talk summarizes our thoughts in attempting a systematic investigation into some key foundational issues of quantum macroscopic phenomena, with the goal of ultimately revealing or building a viable theoretical framework. Three major themes discussed in three intended essays are the large N expansion [2], the correlation hierarchy [3] and quantum entanglement [4]. We give a sketch of the first two themes and then discuss several key issues in the consideration of macro and quantum, namely, a) recognition that there exist many levels of structure in a composite body and only by judicious choice of an appropriate set of collective variables can one give the best description of the dynamics of a specific level of structure. Capturing the quantum features of a macroscopic object is greatly facilitated by the existence and functioning of these collective variables; b) quantum entanglement, an exclusively quantum feature [5], is known to persist to high temperatures [6] and large scales [7] under certain conditions, and may actually decrease with increased connectivity in a quantum network [8]. We use entanglement as a measure of quantumness here and pick out these somewhat counter-intuitive examples to show that there are blind spots worthy of our attention and issues which we need to analyze closer. Our purpose is to try to remove the stigma that quantum only pertains to micro, in order to make way for deeper probes into the conditions whereby quantum features of macroscopic systems manifest.
ABSTRACT: The theory of decoherence, provided we accept its validity, partially solves the quantum-macro clash as it had been seen few decades before. Namely, the theory of decoherence permits us to understand (better) why a given macro-system, in contrast to the quantum entities that compose it, does not superpose simultaneously several possible states. Subsequently, the theory of decoherence partially solves the paradox stemming from the Gedankenexperiment known as “Schrodinger's cat”. In terms of decoherence, it seems reasonable to admit that the feline, independently from any measurement process, is either alive or dead, but never superposes these mutually exclusive states. On the other hand, the resolution of a second essential aspect of the quantum-macro clash cannot find any help from the theory of decoherence. While now the overall wave packet reduction by the macroscopic environment of each quantum phenomenon manifesting itself at our scale seems quite plausible, the theory of decoherence does not explain from where our macroscopic world – ultimately irreducible to the only quantum axioms and laws – could emerge. In other words, whereas the macro-non-superposition problem seems almost solved, the supra-quantum emergence problem entirely persists. From the (current) perspective of the macroscopic non-superposition problem, Schrodinger's cat perhaps retains only a historical interest . But in the present paper, we will try to show that in the context of the supra-quantum emergence problem, the “cat” continues to have a specific relevant significance. On the other hand, it seems commonly admitted that the special status of the “cat” as a representative of living matter does not have any intrinsic meaning within the Gedankenexperiment. Other antithetical “macroscopic superpositions” such as a broken-intact phial or simply the needle of a measurement apparatus pointing simultaneously upwards and downwards would express the same message than the dead-living “cat.” However, here we aim to prove that the living matter status of the “cat”, when related to the supra-quantum emergence problem, does have – despite its author – an intrinsic signification which the modern philosophy of science generally denies. Indirectly inspired by certain assumptions of the neo-Darwinian biologist Ernst Mayr denoting that the existence of living matter expresses a key aspect of the supra-quantum emergence problem, this paper is purposed to establish 1° that the efficient elucidation of the supra-quantum emergence problem should have a formally and experimentally operating “general systems theory” according to Ludwig von Bertalanffy, 2° that this “general systems theory” still looking for its own scientificity remains until further notice reduced to a kind of not entirely full scientific “world vision” or “intellectual attitude” commonly called “holism”. 3° that a generally neglected text passage of Schrodinger's article “Die gegenwartige Situation in der Quantenmechanik” containing the “cat” closely anticipates – despite its author and far ahead of time – the fundamental assumption of “general systems theory”, i.e. “the whole transcends the 'sum' of its parts”, 4° that the factors ensuring the powerful formal consistence of quantum physics are – except for one determining detail – the same which hamper the creation of a scientifically relevant “general systems theory” and, subsequently, impede the elucidation of the supra-quantum emergence problem.
Entanglement can be understood as an extraordinary degree of correlation between states of quantum systems – a correlation that cannot be given an explanation in terms of something like a common cause. Entanglement can occur between two or more quantum systems, and the most interesting case is when these correlations occur between systems that are space-like separated, meaning that changes made to one system are immediately correlated with changes in a distant system even though there is no time for a signal to travel between them. In this case one says that quantum entanglement leads to non-local correlations, or non-locality. More precisely, entanglement can be defined in the following way. Consider two particles, A and B, whose (pure) states can be represented by the state vectors ψA and ψB. Instead of representing the state of each particle individually, one can represent the composite two-particle system by another wavefunction, Ψ AB. If the two particles are unentangled , then the composite state is just the tensor product of the states of the components: Ψ AB = ψ A ⊗ ψ B; the state is then said to be factorable (or separable). If the particles are entangled, however, then the state of the composite system cannot be written as such a product of a definite state for A and a definite state for B. This is how an entangled state is defined for pure states: a state is entangled if and only if it cannot be factored: Ψ AB ≠ ψ A ⊗ ψ B.
The functioning of complex natural systems, such as living systems, still lacks a generally accepted theoretical basis and respective empirical verification. We propose an experiment to test whether such systems are subject to a hitherto unknown organizing principle, in which the quantum mechanical uncertainty principle enables ordering phenomena in chaotic or nearly chaotic systems in the sense of a strong emergence principle. Contrary to previous proposals, our hypothesis does not require fragile macroscopic quantum coherence, ensuring compatibility with the harsh conditions in living systems. To test this hypothesis, we suggest comparing two virtually identical, complex artificial neural networks as a quantitative benchmark. One setup utilizes deterministic pseudo-random number generators at key sensitive points, while the other uses quantum-based physical random-number generators. A favorable outcome demonstrating the superiority of quantum randomness would have considerable implications beyond artificial networks, particularly for the discussions on consciousness and free will.