Tagged Questions
0
votes
0answers
17 views
Showing that the CHSH inequality is not violated
I can usually work out whether CHSH inequality is violated when the observables that we are measuring and the state we are in is given explicitly, but I'm struggling with the generality of the ...
12
votes
2answers
111 views
Is every quantum measurement reducible to measurements of position and time?
I am currently studying Path Integrals and was unable to resolve the following problem. In the famous book Quantum Mechanics and Path Integrals, written by Feynman and Hibbs, it says (at the beginning ...
3
votes
1answer
77 views
Motivation for Wigner Phase Space Distribution
Most sources say that Wigner distribution acts like a joint phase-space distribution in quantum mechanics and this is justified by the formula
...
6
votes
1answer
83 views
What experiments have been proposed to discriminate between interpretations of quantum mechanics?
There are a lot of potentially correct interpretations of quantum mechanics. While I've heard descriptions of a lot of them, I've never heard of an experiment being done to test any of them aside from ...
12
votes
3answers
592 views
Is the universe fundamentally deterministic?
I'm not sure if this is the right place to ask this question. I realise that this maybe a borderline philosophical question at this point in time, therefore feel free to close this question if you ...
7
votes
7answers
332 views
Why Quantum Mechanics as a non-fundamental effective theory?
My question: What (physical or mathematical) reasons (not philosophical) do some physicists ('t Hooft, Penrose, Smolin,...) argue/have in order to think that Quantum Mechanics could be substituted by ...
3
votes
2answers
144 views
Determinism, classical probabilities, and/or quantum mechanics?
[I]f you want a universe with certain very generic properties, you seem forced to one of three choices: (1) determinism, (2) classical probabilities, or (3) quantum mechanics. [My emphasis.]
...
1
vote
0answers
33 views
What is the difference between Cramer and Vaidman?
Two very interesting new papers on arXiv last night by Lev Vaidman and friends lead me to ask about the differences between Cramer's transactional interpretation of quantum mechanics (TIQM) and the ...
1
vote
1answer
62 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 ...
0
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0answers
51 views
Hamiltonian matrix propertu
A professor made an statement to prove the variational theorem:
Because the Hamiltonian (H operator of quantum physics) is diagonal in its own eigenfunction, the terms in $\left \langle \Phi _{m} ...
4
votes
1answer
108 views
Quantum Mechanics - Hidden Variables
In Steven Weinberg's Lecture on Quantum Mechanics (p. 342), he writes:
The correlation between the spins of the two particles can be
expressed as the average value of the product of the ...
2
votes
2answers
154 views
How do we know that there isn't a classical solution to the measurement problem/Quantum Mechanical uncertainty?
It was mentioned to me that it can be shown that there is no classical explanation for the uncertainty in Quantum Mechanics -- i.e. that there are no hidden workings that we have just not yet seen, ...
5
votes
2answers
133 views
Bell's Theorem graph
My friends and I got into an argument about determinism, and I brought up that quantum events are random. But I couldn't prove it.
I found the Wikipedia page on Bell's theorem, which seems to imply ...
0
votes
2answers
80 views
EPR vs. EPRBB? Why can't we perform the original EPR experiment?
The EPR gedanken experiment was invented by Einstein Podolsky and Rosen in 1935.
It involved positions and momenta. In 1957, Bohm revised this gedanken experiment into one involving spins, or ...
0
votes
2answers
75 views
If inherent randomness exist in quantum mechanics, what then of eternalism implied by relativity?
I am nothing but a curious layman so don't go too technical on me.
First of all, I am well aware that a lot of people consider the question of determinism vs indeterminism to be unsolved and others ...
0
votes
1answer
66 views
Why is the energy spectrum of bound QM plane wave continuous?
Please explain it in the context of this task: we have a potential barrier that looks like $\prod$, with $E<U$. There are 3 regions:
1) no field
2) barrier
3) no field
Solution could be ...
0
votes
1answer
85 views
Does quantum reversibility require many worlds?
The source S sends a photon into the beam splitter below.
There is a 50% chance that it will be detected at A and a 50% chance it will be detected at B.
...
2
votes
2answers
164 views
What does the Copenhagen interpretation say about the position of a particle before measurement?
Suppose there is a particle in space. When we measure the position of that particle, we get a particular value with a probability that can be calculated from the wave function. But, according to the ...
13
votes
3answers
367 views
Does quantum computing rely on particular interpretations of quantum mechanics?
It is my understanding that quantum computing relies on quantum superposition and entanglement to work--qbits must exist in all states simultaneously before giving a particular result when observed.
...
2
votes
0answers
43 views
Why should multiple versions of a weak measurement preclude it from being a measurement of intrinsic properties of some system
I've been trying to understand Stephen Parrott's criticisms of weak measurement, outlined most concisely here: http://arxiv.org/abs/0909.0295
One of his major criticisms is that weak measurement is ...
2
votes
2answers
105 views
Cardinality of the Universes Set
No expert by any means, but sometimes, in different contexts the term multiverse used. In quantum mechanics, some say that it is possible that there are actually many universes where all the possible ...
1
vote
2answers
139 views
Is the movement of electrons truly random?
The result of rolling dice is considered pseudo-random because it depends on an almost endless list of factors (how you roll it, the terrain it lands on, etc.), but it is not TRULY random. Is the ...
0
votes
2answers
126 views
What are hidden variables exactly?
What are hidden variables in quantum mechanics? I am aware there are many types but what exactly do they mean or even "do" exactly?
Do they mean that the quantum indeterminacy becomes hidden but ...
1
vote
3answers
171 views
Is a quantum system mandatory for generating true random sequence?
Is a quantum system necessary if we want to generate true random sequence? The mathematical framework used for classical mechanics doesn't involve any random value. But the mathematical framework of ...
6
votes
1answer
358 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, ...
3
votes
3answers
187 views
Are quantum mechanics and determinism actually irreconcilable? [closed]
As a preface, I am not a physicist. I'm simply interested in abstract physics and fundamental principles of the universe and such. As such, if you can provide an answer for the layman (as ...
3
votes
3answers
247 views
How do we show that no hidden variable theories can replace QM?
I've always hit two big stumbling blocks in conceiving of the proof or disproof of hidden variable theories as being even valid idea, let alone an answerable question... I feel I must be ...
-1
votes
1answer
307 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 ...
7
votes
2answers
235 views
Should it be obvious that independent quantum states are composed by taking the tensor product?
My text introduces multi-quibt quantum states with the example of a state that can be "factored" into two (non-entangled) substates. It then goes on to suggest that it should be obvious1 that the ...
0
votes
1answer
73 views
Does the measurement on a subatomic particle give its mass?
No doubt I am wondering about the Young's double slit phenomena. If we observe or measure the properties of a subatomic particle, we are able to know its mass,velocity and it comes to existance. So is ...
1
vote
3answers
168 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 ...
0
votes
1answer
127 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.
1
vote
1answer
118 views
Can silicon droplets bouncing on a vibrating surface be a model for Quantum Mechanics?
In
this video on
youtube
it is claimed that silicon droplets bouncing on a vibrating surface show behaviour in analogy to particle/wave duality in Quantum Mechanics.
Is this true? Did they ...
3
votes
1answer
135 views
Question about Wigner's friend
The Wigner's friend thought experiment can be used to understand non-realism in quantum mechanics. For anyone not familiar, the thought experiment involves two researchers observing an experiment at ...
0
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0answers
130 views
Recent poll on quantum interpretations [closed]
I'm talking about this poll:
http://www.nature.com/news/experts-still-split-about-what-quantum-theory-means-1.12198
I don't now much about quantum mechanics but this reminded me of the state of math ...
1
vote
2answers
160 views
Do scientists literally believe the Schröedinger's cat though experiment?
I've heard the Schrödinger's cat "paradox" (although there's nothing particularly paradoxical about it, just counterintuitive), but I've never been clear on whether or not it's meant to be taken with ...
0
votes
2answers
157 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 ...
1
vote
0answers
87 views
Consistent histories and Bohm mechanics, many worlds in disguise?
This was posted on here in someone's Phys.SE answer:
No, in the many worlds interpretation, every parallel universe is real, but in consistent histories, once you choose your projection operators, ...
1
vote
3answers
118 views
How would a realist interpretation of the Mermin-Peres square look like?
How would a realist interpretation of the Mermin-Peres square with counterfactual definiteness and the existence of states prior to measurements look like?
1
vote
3answers
382 views
Is the classical world an illusion?
In the paper
Zeh, H. D. The Wave Function: It or Bit? In Science and Ultimate Reality, eds. J.D. Barrow, P.C.W. Davies, and C.L. Harper Jr. (Cambridge University Press, 2004), pp. 103-120. ...
0
votes
2answers
166 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 ...
0
votes
1answer
129 views
Who are “we”, and what counts as a “question” in consistent histories?
If the preferred basis in quantum mechanics and/or choice of consistent histories in consistent histories is arbitrary, and can only be determined by the "questions we ask", just who exactly is this ...
0
votes
1answer
211 views
Quantum superposition and fate
First of all, sorry for my knowledge of physics. Maybe my question is too obvious but I want to ask it.
I am thinking about fate and if it exist or no.
According to my assumption if I take any ...
3
votes
5answers
625 views
Connection between quantum physics and consciousness
Can someone explain the quantum physics-consciousness connection? In the double slit or quantum eraser experiments, the system behaves as a whole, with some apparent time independent traits. Invoking ...
1
vote
2answers
124 views
According to wave function collapse you only have one outcome, so what happens to the other superpositions?
If the superpositions of a wave function are not needed because only one of the superpositions is allowed, what happens to the eigenvalues of the "null" superpositions?
Is the energy transferred ...
3
votes
2answers
204 views
Weak measurements rule out Many Worlds Interpretation?
I came across a paper that claims to prove that the Many Worlds interpretation is invalid by applying weak measurements.
The paper can be found here: ...
4
votes
3answers
380 views
How does Bell's theorem rule out the possibility of local hidden variables?
It seems to be common consensus that the world is non-deterministic and this is proved by Bell's theorem.
But even though Bell's experiments proved that the theory of quantum mechanics work, How does ...
3
votes
2answers
143 views
Interpretation of $e|\psi|^2$ as electron density
In solid state physics the electron density is often equated to $e|\psi|^2$. However, the Sakurai says (Chapter 2.4, Interpretation of the Wave Function, p. 101) that adopting such a view leads "to ...
2
votes
1answer
97 views
What is the spatial mode of light or the spatial mode of a massive particle?
I'm extremely confused by what physicists mean by the spatial mode of light. I am also equally if not more confused by what the spatial mode of a massive particle is. Can anyone help me out by ...
4
votes
1answer
107 views
Temporal part of Quantum Wavefunction
I was hoping that someone could give me the more fundamental reason that we take as the temporal part of a quantum wavefunction the function $e^{-i\omega t}$ and not $e^{+i\omega t}$? Clearly ...
