What is Hidden variables: Definition and 62 Discussions
In physics, hidden-variable theories are proposals to provide explanations of quantum mechanical phenomena through the introduction of unobservable hypothetical entities. The existence of fundamental indeterminacy for some measurements is assumed as part of the mathematical formulation of quantum mechanics; moreover, bounds for indeterminacy can be expressed in a quantitative form by the Heisenberg uncertainty principle. Most hidden-variable theories are attempts at a deterministic description of quantum mechanics, to avoid quantum indeterminacy, but at the expense of requiring the existence of nonlocal interactions.
Albert Einstein objected to the fundamentally probabilistic nature of quantum mechanics, and famously declared "I am convinced God does not play dice". Einstein, Podolsky, and Rosen argued that quantum mechanics is an incomplete description of reality. Bell's theorem would later suggest that local hidden variables (a way for finding a complete description of reality) of certain types are impossible.
A famous non-local theory is the De Broglie–Bohm theory.
I was revisiting @DrChinese 's Bell's Theorem with Easy Math which sparked a few questions, which I am hoping might offer a potential path to a deeper understanding of Bell's Theorem and Quantum Mechanics (QM) in general.
The explanation uses light polarisation experiments to explain how we...
Hi,
I have a basic understanding of quantum physics. I was reading a Wikipedia article on hidden variables, https://en.wikipedia.org/wiki/Hidden-variable_theory . The article says the following.
I was confused about the words "local" and "nonlocal" in the quote above so I checked out another...
Suppose the EPR* concept were true as it would be applied to entangled photon polarization. (Please note: I am not saying it is.) They thought QM was incomplete, because there must exist "elements of reality" (hidden variables) that supplied the highly correlated results on entangled particle...
I can remember reading something about a future experiment which alledgely could decide if there is an underlying deterministic layer governing quantum phenomena or if pure, empty chance rules suppreme (which I can't imagine).
It had something to do with arrival times but I can't imagine how...
If individual atoms are indistinguishable from one another, then how can you tell if atom A will experience radioactive decay before identical atom B? ISTM there would have to be some underlying structure beyond electrons and quarks and unique to each atom / particle to be able to do this...
In one of the Insights. Either QM is incomplete (because we only have access to probabilities in conventional experiment) or there are Many Worlds. I want to pick incompleteness.
But in Einstein context of it. Incompleteness means there were hidden variables.
Is there another meaning of...
Summary: Bell's Theorem rules out any hidden variables but does it rule out some finer structure to quantum particles?
At larger scales of the universe, we would see entanglement as cloning. For example, two human clones have the same color eyes because their DNA is identical. I've been...
Smolin latest book about the quantum is quite interesting. Its called "Einstein Unfinished Revolution: Search for What Lies Beyond the Quantum" and he has a new theory or interpretation. Id like to know what you make of it. The theory is very simple. Similar views produce QM. May i know how this...
If we would learn (somehow) that the pilot wave theory is false, that there are not even "non local" hidden variables, would this lead to a paradigm shift in physics?
I ask because it would mean that a Laplace demon wouldn't even in theory able to predict the exact future motions of particles...
In https://arxiv.org/ftp/arxiv/papers/1409/1409.5158.pdf, the author (Donald A. Graft) concludes that Bell tests cannot refute local realism, because they employ a wrong analysis. He says:
"The quantum joint prediction cannot be recovered in an experiment with separated (marginal) measurements...
Modal interpretations are a class of realist non local hidden variable theories. However, they cannot be made fundamentally lorentz invariant. However, neither can bohmian mechanics but BH is still emprically lorentz invariant. So are modal interpretation empirically lorentz invariant as well?
I was just reading this paper:
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.130401
It essentially shows that if the dynamics of the signalling mechanism in a nonlocal hidden variable theory were computable, then Alice and Bob in the typical EPR set up could use it to signal to...
I just came across the following paper:
Gisin, N. (2011). Impossibility of covariant deterministic nonlocal hidden-variable extensions of quantum theory. Physical Review A, 83(2), 020102.
proving that, under sensible hypotheses, nonlocal hidden variable theories for relativistic quantum...
If it is true that the different QM interpretations all make the same experimental predictions, because they all use the same underlying math of QM. That's why they are called "interpretations" instead of "different theories" then it is a fool's errand to keep searching for interpretations to...
I'd like to start off by saying I'm just a 52 yo interested layman with no back ground in physics so apologize up front for my ignorance!
I understand the basic principle behind Bell's Inequality and how it disproves that when measuring the different spin states of a particle, the particle...
So I've been reading David Bohm's original paper on the alternative interpretation of quantum mechanics in terms of hidden variables, just out of interest. In the 4th section he presents a complex function ψ in terms of R and S, and then (using the time dependent schrodinger equation, TISE)...
Would hidden variables still be consistent with QM if we abandon the concept of locality? For example, entangle particles could be connected via Einstein-Rosen bridges and any measurement would cause this bridge to collapse.
When I hear that mass of a particle has managed to hop through a solid barrier ..it tells me that the mass was a variable and not physical at the time.
If there were nonlocal hidden variables that are indeterministic and doesn't obey counterfactual definiteness. What terms should they be called. I think hidden variable should only be reserved for deterministic counterfactual definite.
What then should we refer to indeterministic...
Hi.
In most articles on Bell's inequalities, both the reality and locality assumptions are thrown at the reader from the beginning. DrChinese however starts with only the reality assumption and shows that it doesn't comply with QM IF it were possible to measure two non-commuting observables...
Hi.
I'm still confused about those three concepts. They sound pretty much the same to me, but this does not comply with Wikipedia's table of comparison of QM interpretations, where pretty much all combinations seem to be present.
Actually, is the "Wavefunction real?" column even about...
It is often said that the Bell's theorem precludes local hidden variables. From a "modern" point of view one should never deduce conclusions from the existence of outputs in non commutative measurements.
It seems that the derivations of this theorem use such results.
Is there a proof which uses...
By the definition of hidden variable (HVs); they are the parameters that determine what quantum states of two entangled particles will be after they are measured at particular measurement setups. Therefore and by definition, HVs should be reproducible and by undertaking measurements once or at...
There's something I don't quite get about most illustrations about Bell's inequality theorem. I will explain what:
Consider a pair of entangled photons fired at two arbitrarily oriented polarizers. I most explications, it seems the author suggests that the hidden variable represents the binary...
[Mentor's note: Moved from a thread about field theories as this is just about the basic meaning of the theorem for ordinary entangled particles]]
Suppose that there are photon spin outcomes that are pre existing from entanglement or from local hidden variables.
For every detector angle...
Does QM uncertainty cause/explain the Second Law of Thermodynamics? If so is entropy the contribution of hidden variables, to our classical world? How about negentropy?
http://arxiv.org/abs/quant-ph/0605031
Irreversibility in Collapse-Free Quantum Dynamics and the Second Law of Thermodynamics...
Bohm writes in his 1951 book "Quantum Theory" (p623): "We conclude then that no theory of mechanically determined hidden variables can lead to all the results of quantum theory". He bases his argument on the uncertainty principle. Presumably the argument is not correct, since Bohm himself...
I recently understood Bell’s theorem (the inequality and the QM calculation), with the help of you guys. But something still bothers me: assuming for the moment that Bell’s inequalities were NOT violated by experiment, how we would we understand the dependence of the varying correlations on the...
The double slit experiment is not known to violate any Bell inequality, and thus may have a local hidden variables description. Does Bohm-Dirac theory provide a local hidden variables description for the double slit? Are there other local hidden variables descriptions for the double slit?
(If...
I'm reading up on interpretations of quantum theory, and I just came across Bell's theorem, which is confusing me. My main concern is this:
Why would quantum mechanics predict something different than hidden variables?
I hope that question is coherent enough. I'm not sure if I'm using the...
This post is my reply to a blog comment by billschnieder, since I do not think it is wise to start a discussion in the blog's comments directly, nor in private messages, because of both the reduced visibility of the discussion and the increased spam-like characteristics of such communication for...
I remember an argument, I think due to David Mermin, that refutes local hidden variables in a single measurement (as opposed to Bell's Inequality, which requires gathering statistics of many measurements). I know that's not a lot to go on, but I'm wondering if this rings a bell (no pun...
Could the "hidden variables" be encoded in the observer?
The hidden variables that have been proposed to dictate the action of quantum outcomes,
Could they be in observer dependent as opposed to encoded in the particle?
We know the observer is an integral part of the process.
Has this...
Invariably in the lay literature when it comes time to show that EPR hidden variables are incompatible with QM, Bell's Theorem is invoked (e.g. Greene's "Fabric of the Cosmos", Zeilinger's "Dance of the Photons", Rosenblum's "Quantum Enigma", ...).
I don't see why a simple application of...
I have a question regarding the paper by John Bell (www.drchinese.com/David/Bell_Compact.pdf ) in which he shows that a certain hidden variable approach cannot reproduce the expectation values predicted by QM for a pair of particles in the singlet state.
After eqn 15 on page 4, I don't...
Everyday analogy why hidden variables can’t explain entanglement
I tried to come up with an everyday “obvious” analogy that explains why a hidden variable theory cannot explain quantum entanglement.
Here’s the story: There are two guests and one moderator on a stage. The moderator...
Hi, another thread talking sbout QM interpertations sparked my interest on the subject.
Now let's assume that we have electrons in a box, it could be anywhere inside.
And let us assume that the electrons do indeed have unique positions instead, that each electron has a set of three continuos...
(Part of) The proof/logic of Bell's theorem goes thus:
With the measurements oriented at intermediate angles between these basic cases, the existence of local hidden variables would imply a linear variation in the correlation. However, according to quantum mechanical theory, the correlation...
Hello everyone,
I was reading about Bell's theorem on Wikipedia. One thing I found particularly interesting:
In particular number 2. The points he made can be found at http://bayes.wustl.edu/etj/articles/cmystery.pdf . While I did not understand all the steps from Bell's Theorem, I think...
It is an old idea that, at least in principle, hidden variables could be local if they are superdeterministic. However, so far this idea seemed too speculative for highly respectable journals such as Physical Review Letters to publish research on it.
But now it seems that it has changed. The...
It is said that experiment which unproves Bell's unequation does not unprove Bohm hidden variables.
To me Bohm's interpratation seem rather unbeliveable. But it should exist experiment which could unprove it. Which is this experiment? Maybe it is enough that Bohm equation does not work in...
Let me pose a brain teaser for those who believe that they understand quantum (non)locality, Bell, EPR, as well as logic, very well. :wink:
Assume that quantum mechanics is correct (i.e., that future loophole-free experiments will confirm violation of Bell inequalities).
Consider 2...
If we assume that an electron in an entangled pair has more than 2 plans (plans that determine if an electron go up or down through a magnet) to choose from, can we create a local hidden variable theory? If this is true, how many plans to choose from would an electron need for this to work...
Some systems are said to not obey the superposition principle. This is because certain relations are found which are not arrived at by simple addition or subtraction. However, I wonder if some "non-linear systems" can be modeled directly from an underlying set of linear equations. Now, I don't...
Hi everybody!
I would like to understand how entaglement is calculated in Bohm's theory.
I know that in Bohm theory, the particle's spin is not an intrinsic property of the particle, but it depends on the global wave function (particle + device used to mesasur the spin).
So, in the case of...
I've been trying to wrap my head around the issues with Bell's Inequalities (while following the three related threads in this forum) and I think I finally have it figured out well enough to ask a question that's been bothering me.
In particular, I'll start with...
Hello all,
I'm having a couple of problems with interpretations of Quantum mechanics and just want to summarise my understanding so that it can be verified and/or corrected.
Schroedinger's cat leads to the idea of entanglement, namely the observation of one event indicates that other...