Simulating Quantum Mechanics by Non-Contextual Hidden Variables

No physical measurement can be performed with infinite precision. This leaves a loophole in the standard no-go arguments against non-contextual hidden variables. All such arguments rely on choosing special sets of quantum-mechanical observables with measurement outcomes that cannot be simulated non-contextually. As a consequence, these arguments do not exclude the hypothesis that the class of physical measurements in fact corresponds to a dense subset of all theoretically possible measurements with outcomes and quantum probabilities that \emph{can} be recovered from a non-contextual hidden variable model. We show here by explicit construction that there are indeed such non-contextual hidden variable models, both for projection valued and positive operator valued measurements.Comment: 15 pages. Journal version. Only minor typo corrections from last versio

Negativity and contextuality are equivalent notions of nonclassicality

Two notions of nonclassicality that have been investigated intensively are: (i) negativity, that is, the need to posit negative values when representing quantum states by quasiprobability distributions such as the Wigner representation, and (ii) contextuality, that is, the impossibility of a noncontextual hidden variable model of quantum theory (also known as the Bell-Kochen-Specker theorem). Although both of these notions were meant to characterize the conditions under which a classical explanation cannot be provided, we demonstrate that they prove inadequate to the task and we argue for a particular way of generalizing and revising them. With the refined version of each in hand, it becomes apparent that they are in fact one and the same. We also demonstrate the impossibility of noncontextuality or nonnegativity in quantum theory with a novel proof that is symmetric in its treatment of measurements and preparations.Comment: 5 pages, published version (modulo some supplementary material

An Investigation into the Precipitation of Copper from Mine Water, using Sulfur Dioxide to Reduce the Ferric Ion Content

The experiments which were preformed showed that sulfur dioxide would reduce the ferric ion content of the mine waters to a very low figure. The reduction in the ferric ion content would improve the efficiency of the precipitation process, and also increase the recovery of copper

A Comparative Study of Standard American English and Non-Standard American English Accents

Through the birth and maturation of the American society, dominant cultures have developed and become the accepted norm of America. However, with the constant flow of immigrants entering America, a variety of cultures and languages entered, also. The English language has remained the dominant language, while Standard American English has remained the dominant accent. Those who do not display Standard American English (SAE) often fall victim to a lower level of speaker credibility than those who speak SAE. One\u27s sex may also affect speaker credibility due to different communication styles. The affect one\u27s combination of accent and sex has on his or her speaker credibility is explored in this study. The first study attempts to determine one\u27s accent, sex, and the combination thereof, affects speaker credibility based on speech evaluation scores. The second study attempts to determine if the speech\u27s subject matter affects one\u27s evaluation scores, both non-SAE and SAE accented speakers. The research questions answered in the studies are the following: What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on accent? What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on sex? What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on the social-identity of the speaker? What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on the subject matter of the speech? The results of this three level study suggest that a significant difference exists in the evaluation scores based on the speakers\u27 accent

A Comparative Study of Standard American English and Non-Standard American English Accents

Through the birth and maturation of the American society, dominant cultures have developed and become the accepted norm of America. However, with the constant flow of immigrants entering America, a variety of cultures and languages entered, also. The English language has remained the dominant language, while Standard American English has remained the dominant accent. Those who do not display Standard American English (SAE) often fall victim to a lower level of speaker credibility than those who speak SAE. One\u27s sex may also affect speaker credibility due to different communication styles. The affect one\u27s combination of accent and sex has on his or her speaker credibility is explored in this study. The first study attempts to determine one\u27s accent, sex, and the combination thereof, affects speaker credibility based on speech evaluation scores. The second study attempts to determine if the speech\u27s subject matter affects one\u27s evaluation scores, both non-SAE and SAE accented speakers. The research questions answered in the studies are the following: What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on accent? What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on sex? What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on the social-identity of the speaker? What is the difference in the evaluation of non-Standard American English accent speakers and Standard American English speakers based on the subject matter of the speech? The results of this three level study suggest that a significant difference exists in the evaluation scores based on the speakers\u27 accent

Covariant quantum measurements may not be optimal

Quantum particles, such as spins, can be used for communicating spatial directions to observers who share no common coordinate frame. We show that if the emitter's signals are the orbit of a group, then the optimal detection method may not be a covariant measurement (contrary to widespread belief). It may be advantageous for the receiver to use a different group and an indirect estimation method: first, an ordinary measurement supplies redundant numerical parameters; the latter are then used for a nonlinear optimal identification of the signal.Comment: minor corrections, to appear in J. Mod. Opt. (proc. of Gdansk conf.

Is there contextuality for a single qubit?

It was presented by Cabello and Nakamura [A. Cabello, Phys. Rev. Lett. 90, 190401 (2003)], that the Kochen-Specker theorem applies to two dimensions if one uses Positive Operator-Valued Measures. We show that contextuality in their models is not of the Kochen-Specker type. It is rather the result of not keeping track of the whole system on which the measurement is performed. This is connected to the fact that there is no one-to-one correspondence between POVM elements and projectors on the extended Hilbert space and the same POVM element has to originate from two different projectors when used in Cabello's and Nakamura's models. Moreover, we propose a hidden-variable formulation of the above models.Comment: 4 pages, 1 figure, comments welcom

A Bayesian Analogue of Gleason's Theorem

We introduce a novel notion of probability within quantum history theories and give a Gleasonesque proof for these assignments. This involves introducing a tentative novel axiom of probability. We also discuss how we are to interpret these generalised probabilities as partially ordered notions of preference and we introduce a tentative generalised notion of Shannon entropy. A Bayesian approach to probability theory is adopted throughout, thus the axioms we use will be minimal criteria of rationality rather than ad hoc mathematical axioms.Comment: 14 pages, v2: minor stylistic changes, v3: changes made in-line with to-be-published versio