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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2answers
64 views

Can the Copenhagen interpretation and the many-worlds theory be somehow reconciled? [on hold]

Is it possible that, at the moment of observation, a timeline is created where an object is in a state which contrasts its state in the current timeline? Using Schrodinger's cat as an example, let's ...
0
votes
1answer
45 views

What happens with QM particle at constant velocity? [on hold]

In QM particles have wavefunctions that disperse quite fast. The FWHM for gaussian wavepacket increases in time as $\Delta x(t)= \Delta x_0\sqrt{1+(t/\tau)^2} $, $\tau=2m(\Delta x_0)^2/\hbar$ What ...
-2
votes
0answers
49 views

Does “Schroedinger's cat” need entity knowledge to work? [on hold]

I've never studied physics, but am interested in whether this paradox, from an interpretation of quantum mechanics, can still be stated if we don't know anything about unobservable entities. My ...
3
votes
1answer
110 views

On a measurement level, is quantum mechanics a deterministic theory or a probability theory?

Quantum mechanics is a non-commutative probability theory. As such, it fundamentally behaves differently from classical probability theories. This manifests itself most pronouncedly in the uncertainty ...
3
votes
2answers
275 views

Logic of the 'imaginary wave function collapse' argument in Double Slit experiment

My question is in regards to the stance that the 'wave function collapse' is not an actual physical occurrence. That is, you are not, by observation, changing the particles position from a wave to a ...
4
votes
2answers
122 views

By what logic does one come to support a certain interpretation of quantum mechanics?

I have been on Wikipedia reading up on the various interpretations of quantum mechanics. I am entering my final semester as an undergraduate and have taken a QM course, so I am familiar with the basic ...
-1
votes
1answer
70 views

Feynman path integral interpretation of the Aharonov Bohm effect [closed]

I have recently been reading about the interpretation of the Aharonov-Bohm effect via Feynman's path integral (see viXra:1403.0950). I do not know whether I am missing something, but I do not ...
1
vote
4answers
125 views

Information, entanglement and EPR

I'm currently trying to understand why superluminal information transport is not possible. Therefore, I would like to get some help concerning the definition of information or the general setting. ...
13
votes
4answers
2k views

Is the collapse of the wave function inherently time asymmetric?

Schroedinger's equation, as we all know, is time symmetric. In quantum field theory, we have to come up with a more sophisticated CPT reversal, but the essential point remains unchanged. However, the ...
2
votes
1answer
57 views

Different postulates and statistical interpreations of quantum mechanics

Hi I have a query about the difference of two aspects of the statistical interpretation of quantum mechanics given in the popular introductory quantum mechanics books "Introduction to Quantum ...
14
votes
7answers
1k views

Are coherent states of light 'classical' or 'quantum'?

Coherent states of light, defined as $$|\alpha\rangle=e^{-\frac{|\alpha|^2}{2}}\sum_{n=0}^\infty \frac{\alpha^n}{\sqrt{n!}}|n\rangle $$ for a given complex number $\alpha$ and where $|n\rangle$ is a ...
5
votes
1answer
172 views

Is frequency or Bayesian interpretation used in quantum mechanics?

In quantum mechanics, we deal with probability. There are two kinds of interpretations: frequency and Bayesian. Which one is actually used in quantum mechanics? My impression is, it doesn't matter. ...
0
votes
7answers
1k views

Could this mean that Schrodinger's Cat thought experiment is false?

Since it is uncertain on whether or not the cat could be dead or alive, it is concluded that it depends on the observer to make it either dead or alive. But lets look at a clock. It doesn't take ...
1
vote
2answers
82 views

De Broglie- Bohm Quantum Theory

From what I have read the Standard Model of Particle Physics uses quantum mechanics,special relativity, along with other assorted mathematics to make predictions and provide a framework for QED, QCD, ...
1
vote
1answer
76 views

Is the MWI symmetric in time?

Reading the blog of Sean Carroll (I recognize he isn't the only voice) has made me more sympathetic to the notion of many worlds, but reading Susskind (also not the only voice) has made me think that ...
8
votes
1answer
700 views

Many-worlds: Where does the energy come from?

With regard to the theory that each time a wave function collapses the universe splits so that each possible outcome really exists - where does all the energy required to create all the new universes ...
3
votes
1answer
431 views

Double slit experiment and entanglement [duplicate]

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 ...
1
vote
1answer
92 views

Probability in QM: derivation or interpretation? [duplicate]

It is known that coordinates $C_k\in\mathbb{C}$ of the QM-state vectors $|\psi\rangle$ has an interpretation as probability weights $p_k$ in the whole state through the formula like $|C_k|^2=p_k$. We ...
8
votes
5answers
408 views

In the oil droplet experiments that suggest de Broglie’s pilot wave theory might be accurate, what does the fluid surface correspond to?

As a particle travels to a screen, it is traveling through 3-dimensional space. In the oil droplet experiment, there are only two dimensions of any importance—the droplet merely moves along the ...
16
votes
4answers
2k views

Is the statistical interpretation of Quantum Mechanics dead?

I'm sure this question is a bit gauche for this site, but I'm just a mathematician trying to piece together some physical intuition. *Question:*Is the statistical interpretation of Quantum ...
8
votes
1answer
238 views

Does it make sense to speak of amplitudes of finite closed boundaries in QFT?

A example of amplitude in Relativistic Quantum Mechanics or specifically in QFT is the amplitude of a field configuration on a space-like hyper-surface of space-time to "lead" to another field ...
5
votes
1answer
251 views

Calculate the entropy per atom in Bohmian Mechanics

Bohmian mechanics description of a large number of interacting atoms would require a large phase space due to the large number of classical degrees of freedom. The entropy per atom is given as the ...
-1
votes
2answers
115 views

Do conservation laws contradict quantum mechanics? [closed]

Take for example the double-slit experiment interpreted in the Copenhagen sense. The particle leaves as an object with mass, yet passes through the slits as a massless wave, only to collapse again as ...
8
votes
4answers
794 views

Does Dirac's argument against classical mechanics stand in contradiction to Bohm's theory?

In his book on Quantum Mechanics, P.A.M. Dirac talks about the stability of the atom as a means of demonstrating the need for quantum mechanics. He writes: The necessity for a departure from ...
-1
votes
2answers
154 views

Would Einstein have accepted the presumptions that lead to the Bell inequality?

To check the correlation between Hidden Variable Theory and Quantum Mechanics, Bell calculated the expectation value $$<\sigma_{e}(\vec a,\vec V) \sigma_{p}(\vec b,\vec V)> = \int d^n V \rho(\...
4
votes
4answers
264 views

Many-worlds interpretation

Regarding many-worlds interpretation as an alternative explanation to Copenhagen. If we take the generation or possibility of alternative universes as an explanation for the collapse of wavefunction ...
2
votes
3answers
316 views

Is Bohmian Mechanics incompatible with loop corrections?

For those who continue to be unsatisfied with Quantum Mechanics (QM), Bohmian Mechanics (BM) is an alternative worth considering. It is sometimes claimed that BM is equivalent to QM, but Lubos Motl ...
14
votes
2answers
2k views

Is the preferred basis problem solved?

Once and for all: Is the preferred basis problem in the Everettian Interpretation of QM considered solved by decoherence or not? THere are a few people who claim that it's not, but it seems the vast ...
2
votes
2answers
367 views

Does recent paper show Bohmian mechanics is correct?

The following paper was recently featured in a German science magazine (Spektrum der Wissenschaft): "Experimental nonlocal and surreal Bohmian trajectories" (DOI:10.1126/science.1501466) The abstract ...
5
votes
5answers
182 views

What is the explanation for the interference patterns in MWI?

In Young's double-slit experiment, MWI states that in some "worlds" the particle goes through one slit, and in others it goes through the other. If this is so, why do we get an interference pattern? ...
1
vote
1answer
88 views

How is no-conspiracy theory compatible with determinism? [closed]

Bell's theorem states that any physical theory that incorporates local realism and the no-conspiracy assumption cannot reproduce all the predictions of quantum mechanical theory. Hence, we cannot ...
3
votes
4answers
422 views

Is there any quantum interpretation which isn't “crazy” at all? [closed]

Is there any quantum interpretation which isn't "crazy" at all? Exponentially many parallel worlds in MWI, superdeterministic conspiracies, and/or nonlocality in hidden variables, idealism and the ...
-1
votes
1answer
59 views

What is the difference and/or similarity between multiple universes in inflation and in quantumphysics? [duplicate]

Some theories propose that there are more universes. In one of them it is said that there are parallel universes, due to inflations after the big bang that created them. But in the two-slit ...
4
votes
2answers
655 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 ...
5
votes
2answers
151 views

Bell's theorem and fluid-mechanical experiments using droplets: are local hidden-variable theories possible after all?

Recent fluid-mechanical experiments by the groups of Couder in Paris and Bush at MIT, mimic a surprisingly wide range of quantum effects. The essential ingredient of these fluid-mechanical systems is ...
4
votes
1answer
59 views

Born-like measuring rule in classical experiments

this 2011 paper "Born's rule from measurements of classical signals by threshold detectors which are properly calibrated" by Khrennikov investigates the theoretical possibility of Born-like ...
9
votes
3answers
665 views

Couder-Fort Oil Bath Experiments and Quantum Entanglement Phenomena

The oil bath experiments of Couder and Fort have been able to reproduce various "pilot wave like" quantum behavior on a macroscopic scale. Particularly striking is the fact that the double-slit ...
0
votes
1answer
84 views

In the many worlds interpretation of q.m. what makes a superposition af states split in two sepearate ones?

I was wondering, what agent makes a superposition of, let´s say, the two spins of an electron, máke them split into two separate ones (up and down). And is this not in contradiction to the law of ...
0
votes
0answers
76 views

Can't many-worlds interpretation explain wavefunction collapse?

According to the many-worlds interpretation when universe splits in interaction, the observer in each universe measures corresponding pure state thus seeing collapse. Well, it may be an interpretation,...
6
votes
4answers
2k views

Does physics claim that every possible world has or will exist? [closed]

Has physics proven that every possible world has or will exist? Someone on-line, who actually seems fairly intelligent, but troll-ish, claims that there is good reasons for it, not from any ...
0
votes
1answer
46 views

Multiple measurements and the any worlds interpretation

My question has some similarities to but also differs significantly from this question which was described in many of its answers as not being a quantum mechanical measurement and was I think, ...
1
vote
0answers
66 views

Why not measure the velocity of a quantum particle by $\frac{\Delta \vec{x}}{\Delta t}$

Why is it not possible in quantum mechanics to measure the velocity (and thus momentum) of a particle just by two position and time measurements and get it approximately by $$ \vec{v} = \frac{\vec{x}...
3
votes
2answers
123 views

When does the world split in MWI

I've been reading Eliezer Yudkowsky's blog post regarding decoherence and many worlds, and although he is not a physics but a strong proponent of MWI, I can basically see why he feels that MWI is a "...
0
votes
0answers
49 views

Interpretation of a case of the double square well

Consider a 'double square well' potential (where $E < 0$) defined as: $$V(x) :=\begin{cases} -V_0~~~~~~~~~~~~~\text{for }\frac{b}{2} < x < \frac{b}{2} + a \text{ and } -a - \frac{b}{2} < ...
4
votes
5answers
732 views

Do we really know which slit the photon passed through in Afshar's experiment?

The plain old double slit experiment displays interference when we don't measure which slit the photon passed through, and no interference when it is measured. Let's turn our attention to the case ...
2
votes
2answers
139 views

Meaning of “realism” in quantum mechanics

When physicists doing work in quantum measurement, decoherence, Bells' inequalities etc. use the term "realism" what exactly do they mean? I'm looking for answers targeted towards, say, someone whose ...
0
votes
0answers
36 views

Statement of vector model of angular momentum in Eisberg and Resnick

While serving as a teaching assistant for a sophomore-level Quantum Physics course, I came across the following paragraph in Eisberg and Resnick regarding orbital angular momentum (section 7-8, page ...
3
votes
1answer
87 views

Is the trajectory of a quantum particle a well defined concept and how does this depend on the interpretation of quantum mechanics?

A common statement about quantum physics is that the "trajectory" of a particle is no longer a well defined concept because of the uncertainty relations for position and momentum. If one interprets ...
2
votes
4answers
242 views

Does Free Will Theorem imply that quantum mechanics plays crucial role in our brain’s functioning (consciousness)?

Does Free Will Theorem imply that quantum mechanics plays crucial role in our brain’s functioning (consciousness)? Is opposite statement of Free Will Theorem right: If elementary particles have a ...
2
votes
1answer
49 views

Question about Bell's Theorem and hidden variable equations [closed]

I am trying to understand Griffiths explanation of Bell's theorem in chapter 12 of 2nd edition Intro to QM (or the afterword section A.2 in the 1st edition). He starts with given two detectors ...