This tag is for questions relating to what, if anything, the quantum mechanical formalism and experimental results say about the way the world works.

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3answers
239 views

Are there any QM effects where charged particles are not intimately involved?

Are there any QM effects that have been/could be measured from interactions involving non-charged particles? Elementary QM is all about the electron energy levels in the atom, photon - atom ...
16
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3answers
1k views

How much is quantum computation changing the interpretation of quantum theory, and, if at all, how?

At the beginning of quantum computation, David Deutsch made a strong claim that the Many Worlds interpretation of quantum theory was at the foundation of his ability to do what he did. There was a lot ...
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2answers
194 views

What are the practical applications of quantum foundations?

Many quantum foundation researchers keep emphasizing that For All Practical Purposes (FAPP), quantum foundations are irrelevant. They even invented an acronym for it! Does that mean that quantum ...
4
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2answers
355 views

Determinism loophole?

I was thinking about the question I posted yesterday, and I thought of a better way to ask it. I'm trying to figure out why QM necessitates "pure randomness". Assume you have a photon that has a ...
0
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1answer
205 views

Many worlds interpretation

I think many worlds interpretation is inconsistent with the EPR paradox. Quantum mechanics says that particles are really in more places at the same time and the particle is really only probability ...
3
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2answers
240 views

Does quantum randomness predicate an infinite number of realities?

I am a layman when it comes to physics and especially quantum mechanics. I have seen many documentaries on the subject, and often in these productions there is a physicist featured explaining the ...
0
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1answer
135 views

If Copenhagen interpretation is true, why can't a blind man throw a ball through a wall?

If it is true that particles are in different potential locations until an observer comes along and collapses the wave function, then how can a blind man throw a ball and hit a wall if the particles ...
0
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0answers
112 views

Test for Many Worlds Hypothesis

If one actually ran an experiment similar to the Schrodinger's cat thought experiment, and ran it enough times (with the same cat) to get the confidence interval good enough, could one say that ...
12
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3answers
1k views

Why am I wrong about how to view gauge theory?

Edit: I know there have been some similar questions but I don't think any had quite articulated my particular confusion. If gauge symmetries are really just redundancies in our description accounting ...
0
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0answers
26 views

Representation of a Signal and its evolution via Quantum System

I am a total beginner in the field of Quantum Mechanics. So, the question I am asking may be a silly one. So kindly give me possible answers or advice for modifications. Recently I am learning the ...
4
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2answers
302 views

Can the quantum eraser experiment result indicate a 'computed universe'?

The quantum eraser experiment tells us that a photon shot at two slits is a wave, unless you measure which slit is taken and you do not destroy the measurement result. I've found this very similar to ...
1
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1answer
246 views

Quantum randomness and brownian motion in biological systems, e.g., fertilization

I am looking for examples of physical indeterminacy impacting the macroscopic world. By physical indeterminacy, I mean physical sources of randomness such as quantum indeterminacy or brownian motion. ...
3
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0answers
93 views

Are frequency and likelihood the same across the multiverse?

My probability text distinguishes between two interpretations of probability values: the frequency of occurrence "as percentage of success in a moderately large number of similar situations" (coin ...
5
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0answers
106 views

Free Will Theorem question

The Kochen-Specker Theorem says, if I understand it correctly, that the results of spin measurements cannot be predetermined independent of measurement. They get to this conclusion by describing 33 ...
1
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2answers
247 views

Many world interpretation on test

Is there any experiment conducted to prove Many world interpretation of Quantum mechanics? If it can't be proved why we should take MWI seriously? Recently I read some papers of Max Tegmark who is an ...
1
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4answers
1k views

Do multiple electrons exist during superposition?

Wikipedia says: Quantum superposition is a fundamental principle of quantum mechanics that holds that a physical system—such as an electron—exists partly in all its particular, theoretically ...
2
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0answers
82 views

Quantum mechanics formulations [closed]

There are about 9 different formulations of quantum mechanics. What are the merits and setbacks of each formulation? In the path integral formulation, is the sum over all possible paths idea purely ...
3
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1answer
552 views

(thought) experiment re: Bell's Theorem and Schrodinger's cat

I apologize if this question is naive. I am wondering about what would happen with the following experiment. Start with a standard Bell's Theorem setup: We have two quibits entangled in a particular ...
9
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3answers
337 views

Is the Copenhagen interpretation merely an approximation to quantum mechanics?

So, I'm reading Max Tegmark's Our Mathematical Universe (Knopf edition, p. 229). He's discussing Everett/MWI for a bit and I'm not really paying attention and then I wake up to this: [I]t's time ...
-1
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1answer
84 views

Does alternative reality theoretically prove? [closed]

Does Hugh Evert theory means Alternative-Reality (or in general, Parallel-Worlds) and Many-Worlds-Interpretation theoretically prove? Or are scientists have any progress to prove it?
0
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2answers
331 views

Is there anything wrong with the cybernetic interpretation of quantum mechanics by Ross Rhodes?

The interpretation is outlined here It certainly gives a good logical explanation of most quantum oddities.
2
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0answers
358 views

Double slit experiment and entanglement

Just wondering, what would happen in this experiment. In the experiment you would first have two entangled particles. Then you fire one of the particles, lets say "Particle A", at a double slit ...
0
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0answers
91 views

Born rule and Feynman propagators

Let us assume that we want to describe the full process of photon emission by electron A and absorption by electron B. Therefore electron B must be on the forward lightcone of electron A. In the ...
23
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5answers
6k views

Why do people rule out local hidden variables?

I bet the automatic response to my question would be "Bell's theorem" and of course I am not disputing Bell's proof. I am however uncertain of one of his assumptions. The so called "no conspiracy" ...
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0answers
126 views

Why are cosmic conspiracies considered undesirable in quantum interpretations?

Quantum interpretations like superdeterminism, nonlocal hidden variables, etc. are regularly dismissed by the vast majority of physicists because they require "cosmic conspiracies" which can ...
2
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0answers
134 views

How can the pre-measurement be fulfilled?

In the decoherence program, the pre-measurement refers to the evolution in which the system and apparatus form a Schmidt state. In Maximilian Schlosshauer's review article(2005), I read "the linearity ...
7
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2answers
411 views

Interpretation: probability form probability amplitude (free particle)

If you compute the probability amplitude of a free 1D non-relativistic particle with mass $m$, located at position $x_0$ at time $t_0$, for beeing detected at some other point $x_N$ at time $t_N$ you ...
0
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0answers
111 views

The status of unobservable quantum mechanical predictions

Orthodox quantum mechanics intrinsically requires an observer - since the only connection from the mathematical formalism to physical reality is through the measurement axiom (probability of observing ...
24
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7answers
6k views

Why do people still talk about bohmian mechanics/hidden variables [closed]

I was reading the Feynman lectures in physics and after thinking about it for a while it seems particularly unreasonable to talk about hidden variables. Let us say that the electron has some internal ...
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0answers
100 views

What is a potential in De-Broglie-Bohm theory?

As I have so far understood, the De-Broglie-Bohm theory is based on two equations: The Schrödinger equation. The Guiding equation of the De-Broglie-Bohm theory. In the Schrödinger equation (as ...
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0answers
59 views

Is there any “fundamental” uncertainty to the timing of the Big Bang?

I wondered whether, under the probabilistic interpretations of QM, the timing of the Big Bang (or perhaps any other historical event) is fundamentally as uncertain as (or: like) other (e.g., future) ...
3
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1answer
496 views

What is the difference between realism in locality, and counterfactual definiteness?

I understand the EPR-experiment and the Bell inequalities. I can see how dropping 'locality' solves the issue, and how dropping 'realism' solves the issue (e.g. there are really no hidden variables ...
2
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1answer
179 views

Question about Weinberg's derivation of a one-particle states under the Poincare group

I'm reading QFT: Vol 1 by Weinberg and I have a (perhaps trivial) question about a statement he makes on page 63. I can follow him to his derivation of equation (2.5.2): \begin{equation} P^\mu ...
2
votes
1answer
140 views

Product of position eigenvectors at different times

I've been thinking about this, and it might sound like a stupid question, but I can't seem to find an answer anywhere, here goes: Whenever we calculate expecation-values between two position ...
0
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1answer
176 views

The System and the Measuring Gadget

In Quantum Mechanics the value of an observable results from the interaction between the "system" with the "Measuring gadget". But when the experimenter[or the technologist concerned] is ...
5
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2answers
168 views

Basic Interpretation of Compostion of Observables and their Measurement

Given two (or more) observables $A, B$ which commute one can construct a third observable $C= A \circ B$. If $\psi$ is a common eigenvector of $A, B$ with eigenvalues $\lambda_1, \lambda_2$ then it is ...
3
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0answers
83 views

How many worlds does the world split into in the Many Worlds Interpretation? [duplicate]

I've been reading up on the Many Worlds Interpretation of Quantum Mechanics, and there is one thing (among many) that I really don't understand. How many worlds are 'created' by an 'observation' or ...
3
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2answers
1k views

EPR-type experiments and faster-than-light communication using interference effects as signaling mechanism

I understand that faster-than-light communication is impossible when making single measurements, because the outcome of each measurement is random. However, shouldn't measurement on one side collapse ...
15
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13answers
4k views

Arguments for and against Many Worlds?

I would like to hear the best arguments for and against the Many Worlds interpretation of QM.
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0answers
225 views

Is the Copenhagen interpretation still valid?

"The secret lives of photons revealed" - physicsworld.com. It seems that this experiment violates the Copenhagen interpretation. Is it still valid? Can you please give me more insight on this ...
2
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1answer
153 views

Is Dirac's description of a photon in a split beam still seen as correct today?

This comes from the Interference of Photons section in the book The Principles of Quantum Mechanics by P Dirac: We shall discuss the description which quantum mechanics provides of the ...
3
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3answers
1k views

Can superdeterminism resolve contextuality, entanglement and Shor's algorithm in quantum mechanics?

Superdeterminism is the idea that the apparent freedom for the choice of experimental apparatuses and their settings are nothing but an illusion. Contextuality is the dependence of the properties of a ...
5
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1answer
535 views

't Hooft for laypersons

I have looked at some of 't Hooft's recent papers and, unfortunately, they are well beyond my current level of comprehension. The same holds for the discussions that took place on this website. (See, ...
2
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0answers
228 views

Uncertainty Principle and Bohmian mechanics

The Uncertainty Principle is a relationship between measurements of pairs of attributes, position and momentum, as well as energy and time. Perfect precision of one attribute's measurement leads to a ...
2
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1answer
655 views

What is the preferred basis objection to the many-worlds interpretation of quantum mechanics?

I've seen the preferred basis problem referred to in many places, but have not seen a clear explanation of what the problem is. For example, this question asks whether the problem has been solved, but ...
7
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5answers
671 views

How isolated must a system be for it's wave function to be considered not collapsed?

As an undergrad I was often confused over people's bafflement with Schodinger's cat thought experiment. It seemed obvious to me that the term "observation" referred to the Geiger counter, not the ...
3
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2answers
272 views

Are probability-preserving variations of QT with respect to the Born rule mathematically possible?

Is it possible to create (m)any theoretically workable framework(s) - that do(es) produce probabilities - by taking QM and replacing the Born(-like) rule(s) with something that is not equivalent to it ...
9
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4answers
2k views

Why is Gleason's Theorem not enough to obtain Born Rule in Many Worlds Interpretation?

The Many Worlds interpretation suffer from at least 2 "wounds", the preferred basis issue and perhaps the most notorious probability issue. How do you make sense of probability in a model where ...
6
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3answers
560 views

Could quantum mechanics work without the Born rule?

Slightly inspired by this question about the historical origins of the Born rule, I wondered whether quantum mechanics could still work without the Born rule. I realize it's one of the most ...
6
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3answers
292 views

How can the quantum state of the universe decohere

Decoherence explains how a classical state appears once quantum information in a quantum state leaks out. But presumably that environment has its own quantum state which then leaks out to a larger ...