Weekly Papers on Quantum Foundations (4)

Decoherence-Free Subspaces Cannot Prevent the Collapse of Wave Functions 

from quant-ph by Alfred Li Herschel A. Rabitz Benjamin LienhardFri Feb 02 2024 20:56:49 (16 hours)# 1.

Ensuring the effectiveness of quantum information processing relies on prolonged coherence times and precise quantum control. Investigating the limitations of quantum information processing is vital for advancing the development of quantum processors and algorithms. One common challenge in operating quantum systems is an unintended wave function collapse. A random wave function collapse associated with the loss of energy is referred to as spontaneous emission. Spontaneous emission may limit the maximal performance at the physical quantum processor level. Decoherence-free subspaces, theoretically immune to non-unitary dynamics induced by environmental interactions, offer a potential solution. Encoding quantum information in such a subspace can protect it from environmental disturbances, maintaining coherence for extended periods. In this study, we explore the existence of a decoherence-free subspace resilient to spontaneous wave function collapses modeled by continuous spontaneous localization — a mathematical framework at the forefront of addressing the measurement problem in quantum mechanics. Our findings reveal that decoherence-free subspaces cannot shield against spontaneous wave function collapses modeled by continuous spontaneous localization, establishing the spontaneous emission rate as an upper limiting factor on the physical coherence time of quantum systems.

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The development of the concept of exchange forces in the 1930s: close encounters between Europe and Japan and the birth of nuclear theory 

from physics.hist-ph by Marco Di Mauro Salvatore Esposito Adele NaddeoFri Feb 02 2024 17:57:49 (19 hours)# 2.

The onset and the development of the concept of exchange force in quantum physics are historically reconstructed, starting from Heisenberg’s seminal contributions in 1926 and going through the great developments in nuclear physics, which allowed the emergence of the idea of force mediating virtual quanta. Although most of such work was performed in Europe, the last and decisive effort in this long path was carried out by Japanese scientists in the 1930s. This is the main focus of the present work, which retraces the achievements of Yukawa and Tomonaga, whose results and mutual interactions are carefully analyzed and related to those of European physicists.

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Quantum Nonlocality: how does Nature do it? 

from physics.hist-ph by Marian KupczynskiFri Feb 02 2024 17:57:46 (19 hours)# 3.

We answer the question asked by Nicolas Gisin in his article in Science few years ago. He claimed that quantum correlations are coming from outside space time. We explain that Bell Tests allow only rejecting probabilistic coupling provided by a local hidden variable model, but they do not justify metaphysical speculations about quantum nonlocality and objects which know about each other state, even when separated by large distances. We claim that the violation of Bell inequalities in physics and in cognitive science can be explained using the notion of Bohr contextuality. If contextual variables, describing varying experimental contexts, are correctly incorporated into a probabilistic model, then the inequalities cannot be proven and nonlocal correlations may be explained in an intuitive way. We elucidate the meaning of statistical independence assumption called incorrectly: free choice, measurement independence or no conspiracy. Since the correlation does not mean causation the violation of statistical independence should be rather called contextuality and it does not restrict experimenter freedom of choice. Therefore, contrary to what is believed, closing freedom of choice loophole does not prove statistical independence. We claim that quantum correlations are not coming from outside space time, but instead they are due to global space time symmetries.

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Virtuality in modern physics in the 1920s and 1930s: Meaning(s) of an emerging notion 

from philsciFri Feb 02 2024 09:17:26 (1 day)# 4.

Martinez, Jean-Philippe (2024) Virtuality in modern physics in the 1920s and 1930s: Meaning(s) of an emerging notion. In: UNSPECIFIED.

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Real virtuality and actual transitions: Historical reflections on virtual entities before Quantum Field Theory 

from philsciFri Feb 02 2024 09:17:23 (1 day)# 5.

Blum, Alexander and Jähnert, Martin (2024) Real virtuality and actual transitions: Historical reflections on virtual entities before Quantum Field Theory. In: UNSPECIFIED.

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The Property Theory of Space and Non-Spacetime Quantum Gravity Theories 

from philsciThu Feb 01 2024 01:50:24 (2 days)# 6.

Slowik, Edward (2024) The Property Theory of Space and Non-Spacetime Quantum Gravity Theories. [Preprint]

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The physicists philosophy of physics 

from physics.hist-ph by P. J. E. PeeblesWed Jan 31 2024 12:57:36 (3 days)# 7.

I argue that research in physics operates under an implicit community philosophy, and I offer a definition I think physicists would accept, by and large. I compare this definition to what philosophers, sociologists, and historians of science, with physicists, say we are doing.

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Tracing quantum correlations back to collective interferences 

from physics.hist-ph by Ming Ji Jonte R. Hance Holger F. HofmannWed Jan 31 2024 12:57:35 (3 days)# 8.

In this paper, we investigate the possibility of explaining nonclassical correlations between two quantum systems in terms of quantum interferences between collective states of the two systems. We achieve this by mapping the relations between different measurement contexts in the product Hilbert space of a pair of two-level systems onto an analogous sequence of interferences between paths in a single-particle interferometer. The paradoxical relations between different measurement outcomes can then be traced to the distribution of probability currents in the interferometer. We show that the relation between probability currents and correlations can be represented by continuous conditional (quasi)probability currents through the interferometer, given by weak values; the violation of the noncontextual assumption is expressed by negative conditional currents in some of the paths. Since negative conditional currents correspond to the assignment of negative conditional probabilities to measurements results in different measurement contexts, the necessity of such negative probability currents represents a failure of noncontextual local realism. Our results help to explain the meaning of nonlocal correlations in quantum mechanics, and support Feynman’s claim that interference is the origin of all quantum phenomena.

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En Route to Reduction: Lorentzian Manifolds and Causal Sets. (arXiv:2401.15474v1 [physics.hist-ph]) 

from physics.hist-ph by Jeremy ButterfieldTue Jan 30 2024 10:11:23 (4 days)# 9.

I present aspects of causal set theory (a research programme in quantum gravity) as being en route to achieving a reduction of Lorentzian geometry to causal sets. I take reduction in philosophers’ sense; and I argue that the prospects are good for there being a reduction of the type envisaged by Nagel. (I also discuss the prospects for the stronger functionalist variant of Nagelian reduction, that was formulated by Lewis.)

One main theme will be causal set theory’s use of a physical scale (viz. the Planck scale) to formulate how it recovers a Lorentzian manifold. This use illustrates various philosophical topics relevant to reduction, such as limiting relations between theories, and the role of analogy. I also emphasise causal set theory’s probabilistic method, viz. Poisson sprinkling: which is used both for formulating the reduction and for exploring its prospects.

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The Combination Problem for Relational Quantum Mechanics. (arXiv:2401.15790v1 [quant-ph]) 

from physics.hist-ph by Emily AdlamTue Jan 30 2024 10:11:21 (4 days)# 10.

This article uses the existing literature on the panpsychist combination problem as a starting point to think about how to address a structurally similar combination problem in relational quantum mechanics. I note some similarities and differences between the two problems, and I consider various proposed solutions to the panpsychist problem, assessing the prospects for a similar solution in the context of RQM. I argue that overall the prospects for solving RQM’s combination problem look better for RQM with cross-perspective links than for orthodox versions of RQM.

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Probabilities and certainties within a causally symmetric model. (arXiv:2112.10022v4 [quant-ph] UPDATED) 

from physics.hist-ph by Roderick SutherlandTue Jan 30 2024 10:11:19 (4 days)# 11.

This paper is concerned with the causally symmetric version of the familiar de Broglie-Bohm interpretation, this version allowing the spacelike nonlocality and the configuration space ontology of the original model to be avoided via the addition of retrocausality. Two different features of this alternative formulation are considered here. With regard to probabilities, it is shown that the model provides a derivation of the Born rule identical to that in Bohm’s original formulation. This derivation holds just as well for a many-particle, entangled state as for a single particle. With regard to “certainties”, the description of a particles spin is examined within the model and it is seen that a statistical description is no longer necessary once final boundary conditions are specified in addition to the usual initial state, with the particle then possessing a definite (but hidden) value for every spin component at intermediate times. These values are consistent with being the components of a single, underlying spin vector. The case of a two-particle entangled spin state is also examined and it is found that, due to the retrocausal aspect, each particle possesses its own definite spin during the entanglement, independent of the other particle. In formulating this picture, it is demonstrated how such a realistic model can preserve Lorentz invariance in the face of Bell’s theorem and avoid the need for a preferred reference frame.

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Historical curiosity: how asymptotic freedom of the Yang-Mills theory could have been discovered three times before Gross, Wilczek, and Politzer, but was not. (arXiv:2203.12030v2 [physics.hist-ph] UPDATED) 

from physics.hist-ph by M. ShifmanTue Jan 30 2024 10:11:18 (4 days)# 12.

This article was published in 2001 in Festschrift “At the Frontier of Particle Physics; Handbook of QCD”, Ed. M. Shifman, (World Scientific, Singapore, 2001), Vol. 1, page 126. Asymptotic freedom as the basic property of QCD was discovered by Gross, Wilczek, and Politzer in 1973. Personal recollections of David Gross which are being published in this Volume vividly describe the historical background and the chain of events which led to this fundamental breakthrough. Unfortunately, I failed to obtain Politzer’s side of the story. Some details can be found in an interview which Prof. Politzer gave to R. Crease and C. Mann on February 21, 1985 \cite{DP}. Below I acquaint the reader with the pre-1973 appearances of asymptotic freedom which, unfortunately, went unnoticed

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Bell’s Theorem Begs the Question 

from philsciMon Jan 29 2024 16:23:04 (4 days)# 13.

Christian, Joy (2024) Bell’s Theorem Begs the Question. [Preprint]

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Counterparts, Determinism, and the Hole Argument 

from philsciSun Jan 28 2024 11:17:43 (6 days)# 14.

Cudek, Franciszek (2024) Counterparts, Determinism, and the Hole Argument. [Preprint]

Gao, Shan (2024) Why the global phase is not real. [Preprint]

Struyve, Ward (2024) Lorentz invariance and quantum mechanics. [Preprint]

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