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arXiv2012

Is Entanglement Sufficient to Enable Quantum Speedup?

According to the Gottesman-Knill theorem, any quantum algorithm utilising operations chosen exclusively from a particular restricted set are efficiently simulable by a classical computer. Since some of these algorithms involve entangled states, it is commonly concluded that entanglement is insufficient to enable quantum speedup. As I explain, however, the operations belonging to this set are precisely those which will never yield a violation of the Bell inequalities. Thus it should be no surprise that entangled quantum states which only undergo operations in this set are efficiently simulable classically. What the Gottesman-Knill theorem shows us is that it is possible to use an entangled state to less than its full potential. Nevertheless, there is a meaningful sense in which entanglement is sufficient for quantum speedup: an entangled quantum state provides sufficient physical resources to enable quantum speedup, whether or not one elects to use these resources fully.

quant-ph↗

arXiv2012

Quantum Randi Challenge

Observed violations of Bell type inequalities exclude all relativistic micro causal ("local"), counterfactual definite ("real") hidden variable models of nature. This further relativization of our concept of reality triggers a growing pseudoscientific resistance against quantum mechanics (QM). I define Didactic Randi Challenges (DRC) via five characteristics. These are challenges which, according to the laws of nature, are impossible to meet. They effectively refute pseudoscientific claims according to which the challenge could easily be met. DRC work by being known to exist while never having been overcome, despite the large rewards which would follow from meeting the challenge. Pseudoscience exploits well meaning engagement in argument to create the appearance of an expert dispute (sowing doubt). DRC decline to discuss "until the challenge is met", without solidifying the perception of establishment conspiracy. This requires transparency, thus DRC are efficient didactic tools. The Quantum Randi Challenge (QRC) is a DRC designed to reject hidden variable models by simply teaching QM; there is no bet or interaction with challengers. The QRC is a computer game that anybody can modify. The present version includes a simulation of true QM behavior that violates Bell 99% of the time, hidden variables that violate the Bell and CHSH inequality with 50% probability, and ones which violate Bell 85% of the time when missing 13% anti-correlation. The DRC challenge is to modify the hidden variables so that the predicted QM behavior arises, including anti-correlation. If such were possible, the presented programs would make it trivial to meet the challenge. This fact and the whole QRC can be taught to a wide audience via the presented heuristics. Demanding anti-correlation is argued to be superior to employing CHSH.

physics.hist-ph↗

arXiv2012

Ockham's Razor, Probability and Quantum Physics as Logic

This is a philosophy-intense physics article, or, if you wish, a physics-intense philosophy article. Also, being a mathematician, I tend to view the physics, in particular the essence of quantum physics, in emphasizing the mathematical structure that serves as its language. However, I do express views on typically philosophical/epistemological matters. Since these points of view do not seem to me too widely expressed in the literature, while I find them quite compelling, I think this note has some interest.

math.HO↗

arXiv2012

The orientation of Trajan's town of Timgad

An equation, generally used for solar energy applications, can be applied to archaeoastronomical calculations to determine the day of foundation of ancient towns. The equation is that giving the sunrise amplitude, and, the direction of the sunrise on the day of foundation was sometimes used to determine the main street of the town. Here we discuss the case of Timgad, a town founded by the Roman emperor Trajan. Probably, Timgad was founded during the first decade of September.

physics.hist-ph↗

arXiv2012

Arthur Neville Brown: schoolmaster and variable star observer

Arthur Neville Brown, MA, FRAS (1864-1934) was a prolific variable star observer and served for many years as Secretary of the BAA Variable Star Section. This paper discusses Brown's life and career, both as a variable star enthusiast and as a dedicated and highly respected schoolmaster.

physics.hist-ph↗

arXiv2012

Maria Reiche's Line to Archaeoastronomy

Maria Reiche devoted her life to the study of the Nazca Lines, the most famous Peruvian geoglyphs. In fact, she was an archaeoastronomer that proposed for the Lines some interesting astronomical interpretations. We can appraise her approach using satellite imagery and a free planetarium software. A discussion of some geoglyphs is also proposed.

physics.hist-ph↗

arXiv2014

Probabilistic and Geometric Languages in the Context of the Principle of Least Action

This paper explores the issue of the unification of three languages of physics, the geometric language of forces, geometric language of fields or 4-dimensional space-time, and probabilistic language of quantum mechanics. On the one hand, equations in each language may be derived from the Principle of Least Action (PLA). On the other hand, Feynman's path integral method could explain the physical meaning of PLA. The axioms of classical and relativistic mechanics can be considered as consequences of Feynman's formulation of quantum mechanics.

physics.hist-ph↗

arXiv2013

Constructor Theory

Constructor theory seeks to express all fundamental scientific theories in terms of a dichotomy between possible and impossible physical transformations - those that can be caused to happen and those that cannot. This is a departure from the prevailing conception of fundamental physics which is to predict what will happen from initial conditions and laws of motion. Several converging motivations for expecting constructor theory to be a fundamental branch of physics are discussed. Some principles of the theory are suggested and its potential for solving various problems and achieving various unifications is explored. These include providing a theory of information underlying classical and quantum information; generalising the theory of computation to include all physical transformations; unifying formal statements of conservation laws with the stronger operational ones (such as the ruling-out of perpetual motion machines); expressing the principles of testability and of the computability of nature (currently deemed methodological and metaphysical respectively) as laws of physics; allowing exact statements of emergent laws (such as the second law of thermodynamics); and expressing certain apparently anthropocentric attributes such as knowledge in physical terms.

physics.hist-ph↗

arXiv2013

The Objective Indefiniteness Interpretation of Quantum Mechanics

The common-sense view of reality is expressed logically in Boolean subset logic (each element is either definitely in or not in a subset, i.e., either definitely has or does not have a property). But quantum mechanics does not agree with this "properties all the way down" picture of micro-reality. Are there other coherent alternative views of reality? A logic of partitions, dual to the Boolean logic of subsets (partitions are dual to subsets), was recently developed along with a logical version of information theory. In view of the subset-partition duality, partition logic is the alternative to Boolean subset logic and thus it abstractly describes the alternative dual view of micro-reality. Perhaps QM is compatible with this dual view? Indeed, when the mathematics of partitions using sets is "lifted" from sets to vector spaces, then it yields the mathematics and relations of quantum mechanics. Thus the vision of micro-reality abstractly characterized by partition logic matches that described by quantum mechanics. The key concept explicated by partition logic is the old idea of "objective indefiniteness" (emphasized by Shimony). Thus partition logic, logical information theory, and the lifting program provide the back story so that the old idea then yields the objective indefiniteness interpretation of quantum mechanics.

quant-ph↗

arXiv2012

Effective Field Theories and the Role of Consistency in Theory Choice

Promoting a theory with a finite number of terms into an effective field theory with an infinite number of terms worsens simplicity, predictability, falsifiability, and other attributes often favored in theory choice. However, the importance of these attributes pales in comparison with consistency, both observational and mathematical consistency, which propels the effective theory to be superior to its simpler truncated version of finite terms, whether that theory be renormalizable (e.g., Standard Model of particle physics) or nonrenormalizable (e.g., gravity). Some implications for the Large Hadron Collider and beyond are discussed, including comments on how directly acknowledging the preeminence of consistency can affect future theory work.

physics.hist-ph↗

arXiv2012

Nonlinear Wightman fields

A nonlinear Wightman field is taken to be a nonlinear map from a linear space of test functions to a linear space of Hilbert space operators, with inessential modifications to other axioms only to the extent dictated by the introduction of nonlinearity. Two approaches to nonlinear quantum fields are constructed and discussed, the first of which, starting from Lagrangian QFT, offers a fresh perspective on renormalization, while the second, starting from linear Wightman fields, provides an extensive range of well-defined nonlinear theories.

math-ph↗

arXiv2012

The center of mass and center of charge of the electron

If the assumption that the center of mass(CM) and the center of charge(CC) of the electron are two different points was stated 100 years ago, our conceptual ideas about elementary particles would be different. This assumption is only compatible with a relativistic description. It suggests, from the classical point of view, that the angular momentum of the electron has to have a unique value. In the free motion, the CC follows a helix at the speed of light. The spin with respect to CC and to CM satisfy two different dynamical equations which shows that Dirac spin operator in the quantum case satisfies the same dynamical equation as the classical spin with respect to the CC. This means, among other things, that the addition of the three Dirac's spin operators of the three quarks can never give rise to the spin of the proton, so that the proton spin crisis could be related to this incompleteness in the addition of the quark's angular momenta. Some other effects related to spinning particles like the concept of gyromagnetic ratio, a classical description of tunneling and the formation of bound pairs of electrons, are analized.

physics.hist-ph↗

arXiv2012

The Quantum Zeno Effect -- Watched Pots in the Quantum World

In the 5th century B.C.,the philosopher and logician Zeno of Elea posed several paradoxes which remained unresolved for over two thousand five hundred years. The $20^{th}$ century saw some resolutions to Zeno's mind boggling problems. This long journey saw many significant milestones in the form of discoveries like the tools of converging series and theories on infinite sets in mathematics. In recent times, the Zeno effect made an intriguing appearance in a rather unlikely place - a situation involving the time evolution of a quantum system, which is subject to "observations" over a period of time. Leonid Khalfin working in the former USSR in the 1960s and ECG Sudarshan and B. Misra at the University of Texas, Austin, first drew attention to this problem. In 1977, ECG Sudarshan and B. Misra published a paper on the quantum Zeno effect, called "The Zeno's paradox in quantum theory". Their fascinating result revealed the bizarre workings of the quantum world. Misra and Sudarshan's 1977 paper activated over two decades of theoretical and experimental explorations into the subject and still continues to evoke a lot of interest. In the following, the quantum Zeno effect is described and a brief outline of some of the work following Misra and Sudarshan's paper is given. The quantum Zeno effect is yet another example of the myriad unimaginable possibilities that lie waiting in the magical world of the quantum.

physics.hist-ph↗

arXiv2013

On the Unavoidability of the Interpretations of Quantum Mechanics

Recently, the presence in the literature (also recent) of voluminous discussions about the interpretation of quantum mechanics has been labelled as scandalous. We claim that a weak point of the debate which hosted such a conclusion is a lack of a definition of the term "interpretation". In the present note, we would "like to make precise" that meaning and to show how such a clarification is necessary in order to avoid misunderstandings.

physics.hist-ph↗

arXiv2013

From cosmic ray physics to cosmic ray astronomy: Bruno Rossi and the opening of new windows on the universe

Bruno Rossi is considered one of the fathers of modern physics, being also a pioneer in virtually every aspect of what is today called high-energy astrophysics. At the beginning of 1930s he was the pioneer of cosmic ray research in Italy, and, as one of the leading actors in the study of the nature and behavior of the cosmic radiation, he witnessed the birth of particle physics and was one of the main investigators in this fields for many years. While cosmic ray physics moved more and more towards astrophysics, Rossi continued to be one of the inspirers of this line of research. When outer space became a reality, he did not hesitate to leap into this new scientific dimension. Rossi's intuition on the importance of exploiting new technological windows to look at the universe with new eyes, is a fundamental key to understand the profound unity which guided his scientific research path up to its culminating moments at the beginning of 1960s, when his group at MIT performed the first in situ measurements of the density, speed and direction of the solar wind at the boundary of Earth's magnetosphere, and when he promoted the search for extra-solar sources of X rays. A visionary idea which eventually led to the breakthrough experiment which discovered Scorpius X-1 in 1962, and inaugurated X-ray astronomy.

physics.hist-ph↗

arXiv2013

Francesco Ingoli's essay to Galileo: Tycho Brahe and science in the Inquisition's condemnation of the Copernican theory

In January of 1616, the month before before the Roman Inquisition would infamously condemn the Copernican theory as being "foolish and absurd in philosophy", Monsignor Francesco Ingoli addressed Galileo Galilei with an essay entitled "Disputation concerning the location and rest of Earth against the system of Copernicus". A rendition of this essay into English, along with the full text of the essay in the original Latin, is provided in this paper. The essay, upon which the Inquisition condemnation was likely based, lists mathematical, physical, and theological arguments against the Copernican theory. Ingoli asks Galileo to respond to those mathematical and physical arguments that are "more weighty", and does not ask him to respond to the theological arguments at all. The mathematical and physical arguments Ingoli presents are largely the anti-Copernican arguments of the great Danish astronomer Tycho Brahe; one of these (an argument based on measurements of the apparent sizes of stars) was all but unanswerable. Ingoli's emphasis on the scientific arguments of Brahe, and his lack of emphasis on theological arguments, raises the question of whether the condemnation of the Copernican theory was, in contrast to how it is usually viewed, essentially scientific in nature, following the ideas of Brahe.

physics.hist-ph↗

arXiv2012

The Cosmological Constant

Contrary to popular mythology, Einstein did not invent the cosmological constant just in order construct his model universe. He discussed it earlier in "The Foundations of General Relativity" in connection with the proper structure of the source-free field equations. There he dismissed it as arbitrary and unnecessary. It was later that he found its inclusion to be essential to the construction of his model.

physics.hist-ph↗

arXiv2015

The Universe is not a Computer

When we want to predict the future, we compute it from what we know about the present. Specifically, we take a mathematical representation of observed reality, plug it into some dynamical equations, and then map the time-evolved result back to real-world predictions. But while this computational process can tell us what we want to know, we have taken this procedure too literally, implicitly assuming that the universe must compute itself in the same manner. Physical theories that do not follow this computational framework are deemed illogical, right from the start. But this anthropocentric assumption has steered our physical models into an impossible corner, primarily because of quantum phenomena. Meanwhile, we have not been exploring other models in which the universe is not so limited. In fact, some of these alternate models already have a well-established importance, but are thought to be mathematical tricks without physical significance. This essay argues that only by dropping our assumption that the universe is a computer can we fully develop such models, explain quantum phenomena, and understand the workings of our universe. (This essay was awarded third prize in the 2012 FQXi essay contest; a new afterword compares and contrasts this essay with Robert Spekkens' first prize entry.)

quant-ph↗