Scott Aaronson, Is Quantum Mechanics An Island In Theoryspace?, Arxiv.Org, 2004 quant-ph/0401062v2, quant-ph.
This recreational paper investigates what happens if we change quantum mechanics in several ways. The main results are as follows. First, if we replace the 2-norm by some other p-norm, then there are no nontrivial norm-preserving linear maps. Second, if we relax the demand that norm be preserved, we end up with a theory that allows rapid solution of PP-complete problems (as well as superluminal signalling). And third, if we restrict amplitudes to be real, we run into a difficulty much simpler than the usual one based on parameter-counting of mixed states.
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David Albert, How to Teach Quantum Mechanics, , 2019 pp. 1-56.
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Ali Barzegar, QBism Is Not So Simply Dismissed, Foundations Of Physics, 50 (2020) 693-707.
QBism is one of the main candidates for an epistemic interpretation of quantum mechanics. According to QBism, the quantum state or the wavefunction represents the subjective degrees of belief of the agent assigning the state. But, although the quantum state is not part of the furniture of the world, quantum mechanics grasps the real via the Born rule which is a consistency condition for the probability assignments of the agent. In this paper, we evaluate the plausibility of recent criticism of QBism. We focus on the consequences of the subjective character of the quantum state, the issue of realism and the problem of the evolution of the quantum state in QBism. In particular, drawing upon Born’s notion of invariance as the mark of the real, it is argued that there is no essential difference between Einstein’s program of ‘the real’ and QBists’ realism. Also, it will be argued that QBism can account for the unitary evolution of the quantum state.
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Herbert Capellmann, Space-Time in Quantum Theory, Arxiv.Org, 2020.
Max Born, not Werner Heisenberg as is usually assumed, created the original version of Quantum Theory, "Matrix Mechanics". The fundamental laws, commutation relations and quantum equations of motion, resulted from Born's recognition of the basic principle of quantum physics: To each change in nature corresponds an integer number of quanta of action h. Action variables may only change by integer values of h, requiring all other physical quantities to change by discrete steps, "quantum jumps". The mathematical implementation of this principle led to commutation relations and quantum equations of motion, published by Born and Jordan in September 1925. Most importantly, the classical notion of "time", as one common continuous time variable and nature evolving continuously "in time", has to be replaced by an infinite manifold of transition rates for discontinuous quantum transitions. The notion of a point in space-time looses its physical significance. Quantum uncertainties of time, position, just as any other physical quantity, are necessary consequences of quantization of action. The essential differences of Born's discontinuous quantum physics to the standard interpretation, relying on classical space-time concepts, will be described.
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Matteo Carlesso and Mauro Paternostro, Opto-mechanical tests of collapse models, Arxiv Preprint, 2019 1906.11041, quant-ph.
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Eddy Keming Chen, Realism about the Wave Function, Arxiv.Org, 2018 1810.07010v2, quant-ph (7) p. 177.
A century after the discovery of quantum mechanics, the meaning of quantum mechanics still remains elusive. This is largely due to the puzzling nature of the wave function, the central object in quantum mechanics. If we are realists about quantum mechanics, how should we understand the wave function? What does it represent? What is its physical meaning? Answering these questions would improve our understanding of what it means to be a realist about quantum mechanics. In this survey article, I review and compare several realist interpretations of the wave function. They fall into three categories: ontological interpretations, nomological interpretations, and the sui generis interpretation. For simplicity, I will focus on non-relativistic quantum mechanics.
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George F R Ellis and Rituparno Goswami, Space time and the passage of time, Arxiv.Org, 2012 1208.2611v4, gr-qc.
This paper examines the various arguments that have been put forward suggesting either that time does not exist, or that it exists but its flow is not real. I argue that (i) time both exists and flows; (ii) an Evolving Block Universe (`EBU') model of spacetime adequately captures this feature, emphasizing the key differences between the past, present, and future; (iii) the associated surfaces of constant time are uniquely geometrically and physically determined in any realistic spacetime model based in General Relativity Theory; (iv) such a model is needed in order to capture the essential aspects of what is happening in circumstances where initial data does not uniquely determine the evolution of spacetime structure because quantum uncertainty plays a key role in that development. Assuming that the functioning of the mind is based in the physical brain, evidence from the way that the mind apprehends the flow of time prefers this evolving time model over those where there is no flow of time.
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S Gao, Why protective measurement establishes the reality of the wave function, , 2018.
It has been debated whether protective measurement implies the reality of the wave function. In this paper, I present a new analysis of the relationship between protective measurement and the reality of the wave function. First, I briefly introduce protective measurements and the ontological models framework for them. Second, I give a simple proof of Hardy's theorem in terms of protective measurements. It shows that when assuming the ontic state of the protected system keeps unchanged during a protective measurement …
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Shan Gao, Against the field ontology of quantum mechanics, , 2018 pp. 1-13.
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Gabriel Guerrer, Consciousness-related interactions in a double-slit optical interferometer, Files.Osf.Io, 2017.
Motivated by a series of reported experiments and their controversial results, the present work investigated if volunteers could causally affect an optical double-slit system through mental efforts alone. The participants task alternated between intending the increase of the (real-time feedback informed) amount of light diffracted through a specific single slit and relaxing any intention effort. The 160 data sessions contributed by 127 volunteers revealed a statistically significant 6.37 sigma difference between the measurements performed in the intention versus the relax conditions (p = 1.89 × 10−10, es = 0.50 ± 0.08), while the 160 control sessions conducted without any present observer resulted in statistically equivalent samples (z = −0.04, p = 0.97, es = 0.00 ± 0.08). The results couldn’t be simply explained by environmental factors, hence supporting the previously claimed existence of a not yet mapped form of interaction between a conscious agent and a physical system.
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S Hossenfelder and T N Palmer, Rethinking Superdeterminism, Arxiv.Org, 2019.
Quantum mechanics has irked physicists ever since its conception more than 100 years ago. While some of the misgivings, such as it being unintuitive, are merely aesthetic, quantum mechanics has one serious shortcoming: it lacks a physical description of the measurement process. This "measurement problem" indicates that quantum mechanics is at least an incomplete theory -- good as far as it goes, but missing a piece -- or, more radically, is in need of complete overhaul. Here we describe an approach which may provide this sought-for completion or replacement: Superdeterminism. A superdeterministic theory is one which violates the assumption of Statistical Independence (that distributions of hidden variables are independent of measurement settings). Intuition suggests that Statistical Independence is an essential ingredient of any theory of science (never mind physics), and for this reason Superdeterminism is typically discarded swiftly in any discussion of quantum foundations. The purpose of this paper is to explain why the existing objections to Superdeterminism are based on experience with classical physics and linear systems, but that this experience misleads us. Superdeterminism is a promising approach not only to solve the measurement problem, but also to understand the apparent nonlocality of quantum physics. Most importantly, we will discuss how it may be possible to test this hypothesis in an (almost) model independent way.
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Rocco Martinazzo and Irene Burghardt, Local-in-Time Error in Variational Quantum Dynamics., Physical Review Letters, 2020 32357037, 124 (15) p. 150601.
The McLachlan "minimum-distance" principle for optimizing approximate solutions of the time-dependent Schrödinger equation is revisited, with a focus on the local-in-time error accompanying the variational solutions. Simple, exact expressions are provided for this error, which are then evaluated in illustrative cases, notably the widely used mean-field approach and the adiabatic quantum molecular dynamics. Based on these findings, we demonstrate the rigorous formulation of an adaptive scheme that resizes on the fly the underlying variational manifold and, hence, optimizes the overall computational cost of a quantum dynamical simulation. Such adaptive schemes are a crucial requirement for devising and applying direct quantum dynamical methods to molecular and condensed-phase problems.
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Kelvin J McQueen, Is QBism the Future of Quantum Physics?, Arxiv.Org, 2017 1707.02030v1, quant-ph.
The purpose of this book is to explain Quantum Bayesianism ('QBism') to "people without easy access to mathematical formulas and equations" (4-5). Qbism is an interpretation of quantum mechanics that "doesn't meddle with the technical aspects of the theory [but instead] reinterprets the fundamental terms of the theory and gives them new meaning" (3). The most important motivation for QBism, enthusiastically stated on the book's cover, is that QBism provides "a way past quantum theory's paradoxes and puzzles" such that much of the weirdness associated with quantum theory "dissolves under the lens of QBism". Could a non-technical book that almost fits in your pocket really succeed in resolving the notorious paradoxes of quantum theory? I believe the answer is: not in this case. There are three primary reasons. Firstly, the argument that QBism solves quantum paradoxes is not convincing. Secondly, it proves difficult to pin down exactly what QBism says. Thirdly, as a scientific theory QBism seems explanatorily inert, which is maybe why the topic of scientific explanation is not broached. Sections 2-4 below discuss each of these problems in turn. However, there is still a wealth of insights that make this book a worthwhile read, and I shall begin with those.
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Sébastien Poinat, Quantum Mechanics and Its Interpretations: A Defense of the Quantum Principles, Foundations Of Physics, 2020 pp. 1-18.
One of the most striking features of the epistemological situation of Quantum Mechanics is the number of interpretations and the many schools of thought, with no consensus on the way to understand the theory. In this article, I introduce a dis- tinction between orthodox interpretations and heterodox interpretations of Quantum Mechanics: the orthodox interpretations preserve all the quantum principles while the heterodox interpretations replace at least one of them. Then, I argue that we have strong empirical and epistemological reasons to prefer orthodox interpretations to heterodox interpretations. The first argument is that all the experiments on the foun- dations of Quantum Mechanics give a high degree of corroboration to the quantum principles and, consequently, to the orthodox interpretations. The second argument is that the scientific progress needs a consensus: this consensus is impossible with the heterodox interpretations, while it is possible with the orthodox interpretations. Giving the preference to the orthodox interpretations is a reasonable position which could preserve both a consensus on quantum principles and a plurality of views on Quantum Mechanics.
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Sandu Popescu, Nonlocality beyond quantum mechanics, Nature Physics, 2014 pp. 1-7.
Nonlocality is the most characteristic feature of quantum mechanics, but recent research seems to suggest the possible exist- ence of nonlocal correlations stronger than those predicted by theory. This raises the question of whether nature is in fact more nonlocal than expected from quantum theory or, alternatively, whether there could be an as yet undiscovered principle limiting the strength of nonlocal correlations. Here, I review some of the recent directions in the intensive theoretical effort to answer this question.
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