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

learn more… | top users | synonyms

0
votes
2answers
34 views

Books on Quantum Measurement

I have been trying to understand clearly the concept of non locality, hidden variables, quantum measurement etc through research papers. I also read Quantum Theory and measurment by Wheeler and Zurek ...
1
vote
0answers
31 views

How can a spinor represent an “epistemic” state?

I have read a lot of stuff on the seemingly endless debate on ontology/epistemology of the quantum state $\psi$. But I always wonder: how can a spinor be considered epistemic when $\psi$ really ...
0
votes
0answers
15 views

Does quantum complementarity inherently require ensembles?

If there are two complementary observables, $P$ and $Q$, it does superficially appear as if the only kind of empirical evidence we can get for complementarity has to come from statistical data from an ...
2
votes
2answers
78 views

How do probabilities emerge in the many-worlds interpretation?

My understanding is that at each quantized unit of time that a split occurs, every possible recombination of particles occurs in the 'objective' universe. If this is the case, what relevance to ...
-2
votes
0answers
55 views

What would be to live at the quantum level? [closed]

I modify this question so that it can be took as an exercise for the mind a "thought experiment". My main purpose is to "see" the whole picture and my second purpose with this "mind exercise" is to ...
0
votes
0answers
37 views

finetuned quantum experiments by Murch lab, do any have dynamics outside of basic QM formalism/ axioms?

a series of very finetuned quantum experiments have been reported by the Murch lab eg in 2 articles in Nature & analysis there,[1][2][3] some leading to dramatic accounts in the media.[4] do ...
81
votes
3answers
13k views

How come some people are claiming that the Big Bang never happened?

A news story is going viral on social media networks claiming that two physicists have found a way to eliminate the Big Bang singularity, or in layman's terms (as claimed by many sensationalist news ...
2
votes
3answers
141 views

Can existing quantum computers be considered evidence for parallel universes?

In this video ( http://www.youtube.com/watch?v=bJpIclDmi2M ) Max Tegmark , a MIT cosmologist says that if we build a quantum computing successfully it will be a evidence that Parallel Universes ...
13
votes
9answers
1k views

“Reality” of EM waves vs. wavefunction of individual photons - why not treat the wave function as equally “Real”?

In thinking how to ask this question (somewhat) succinctly, I keep coming back to a Microwave Oven. A Microwave Oven has a grid of holes over the window specifically designed to be smaller in ...
2
votes
0answers
87 views

Is it possible to travel between worlds in the many worlds interpretation of quantum theory? [closed]

In the Many Worlds Interpretation (MWI) of quantum mechanics, all possible outcomes of a measurement occur, and each possible outcome corresponds to a distinct "world" or universe. Is it possible to ...
0
votes
2answers
103 views

How does De Broglie–Bohm theory or pilot wave theory explain the results of the Stern–Gerlach experiment?

The Copehagen interpretation of QM explains the Stern–Gerlach experiment by asserting that a particle is in a superposition of states and doesn't have a definite spin until measured. However, the de ...
1
vote
1answer
67 views

What is the significance of Planck's constant in De Broglie–Bohm theory or Pilot-wave theory?

In standard QM, Planck's constant seems to be a constant that describes the smallest quanta of energy in some way. Does De Broglie–Bohm theory have an alternate interpretation of that constant and ...
1
vote
0answers
35 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 ...
3
votes
1answer
107 views

What specifically is incorrect about the Dirac Sea interpretation?

So taking the square root of $E^2 = (m_oc^2)^2 + p^2c^2$ yields two solutions. The Dirac Sea treats the negative solution as an infinite space of electrons with negative energy. All the observable ...
1
vote
1answer
29 views

Bypassing complementarity with cumulative weak measurements?

Consider the standard double slit experiment with one photon at a time. Now, replace the photographic plate (or fine resolution single photon detector screen) with a converging lens, and move the ...
2
votes
2answers
130 views

What does density operator being same for two sytems tells us?

Yesterday I asked a question. I got it that if a density operator is given as $$\rho=\sum_{i=1}^{i=k}p_i|\psi_i\rangle \langle\psi_i| \tag{1}$$ then it means that the system is one of the states ...
2
votes
1answer
163 views

How does many-worlds interpretation make measurement unitary?

Does many-worlds interpretation of QM make the process of measurement (wavefunction collapse) be an unitary transform? If so, how does it do this? If we have an "object" qubit in state ...
0
votes
0answers
32 views

Clarification about time in quantum Bayesianism

What is the nature of time in quantum Bayesianism? At one point, Chris Fuchs claims that time evolution, the past and the laws of physics are subjective inferences. But he also claims quantum ...
1
vote
0answers
37 views

Information loss from entanglement and cosmological horizons?

Suppose we have a qubit P in an unknown quantum state. Unknown as in we didn't prepare it, and don't know how it was prepared either. Without measuring the qubit in any way, we encode it into two ...
0
votes
1answer
51 views

Interpretations of Stern-Gerlach experiment

In many textbooks (J.J. Sakurai for instance) S-G experiment is explained through the idea of a collapse of a state of a system. So here, in this discrete case, we can see quantum behavior more ...
2
votes
1answer
83 views

Do electrons have a location before they are observed/measured? [closed]

Is this in all interpretations of QM? What about interpretations that are realist (MWI, penrose, ect)?
-1
votes
1answer
109 views

In Quantum mechanics, what is realism? [closed]

Some interpretations of QM are realist and some are anti-realist. But, it is the idea that something exists before it is measured, correct?
2
votes
2answers
122 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
6answers
576 views

On the foundations of quantum physics

Quantum physics has to be validated by experiments. But experiments are to be interpreted in the context of quantum physics. Isn'it like a snake biting its own tail? For example, using a scanning ...
1
vote
1answer
53 views

Does the difference between contextuality, nonlocality and retrocausality depend on where we draw the boundaries? [closed]

Suppose we have a quantum system and a measuring apparatus in a superposition of detector settings. Different detector settings would measure "complementary" properties of the quantum system. The act ...
0
votes
0answers
30 views

In MWI, how to make sense of the nonuniqueness of decomposing mixed states into pure states?

It's well known that in quantum mechanics, a generic mixed state can be decomposed into pure states in infinitely many different ways. While this property is kind of understandable if quantum states ...
18
votes
6answers
768 views

Simple example showing why measurement & interaction are different

Does someone know of a clear (pedagogical) example where one can really see(with the math) where interaction and measurement are not synonymous in quantum mechanics? I know that every measurement ...
2
votes
1answer
64 views

Are there any viable toy models of superdeterministic quantum mechanics?

As far as I know, superdeterminism in quantum mechanics is only considered as a theoretical possibility. Are there any fleshed out superdeterministic toy models so far which isn't nonlocal?
6
votes
1answer
142 views

Has the Copenhagen Interpretation remained accurate?

Almost a century past, has the Copenhagen Interpretation (CI) undergone any modification? In other words, has any of its underlying principles been reformulated since? The notable (usual) examples ...
1
vote
0answers
50 views

Would it be possible to Loschmidt reverse Wigner's friend using future technology?

Would it be possible to Loschmidt reverse Wigner's friend using future technology? Why or why not? Can a human be isolated in a decoherence shielded box? Can we have fine control over every single ...
4
votes
3answers
441 views

Why is Wheelers Delayed Choice Experiment Incorrect?

I have come across 'Wheelers Delayed Choice Experiment' which tries to prove that you can work out which Slit a Photon Goes Through in the Double Slit Experiment. But I thought it was impossible to ...
1
vote
2answers
63 views

Does information paradox in the Many Worlds interpretation cause a problem? [closed]

I'm taking a philosophy of time travel class. In one of the lectures, the teacher was discussing problems with the Many Worlds interpretation. He talked about how since anything that can possibly ...
0
votes
3answers
118 views

EPR Paradox resolution: the spin is fixed at creation but its measurement isn't?

The Wikipedia article on the EPR paradox uses the example of an electron and positron created from a common source, each moving in an opposite direction to the other. Detector A is used to measure the ...
1
vote
1answer
152 views

Do consciousnesses get “scattered” across the many worlds of the MWI?

According the many worlds-interpretation (MWI) of quantum mechanics, following a decision with possible outcomes $A$ and $B$, with respective probabilities $p_A=P(A)$ and $p_B=P(B)$, a proportion ...
3
votes
0answers
156 views

Testing Many-Worlds Interpretation (MWI) with a causality-violating configuration of “superluminal cables”

Suppose we managed to arrange a causality-violating transmission of data with hypothetical “superluminal cables” (SLC; see both links for respective descriptions) and expect, similarly to ideas ...
2
votes
1answer
110 views

Why no Top Physicists Work on Bohmian Mechanics? [duplicate]

I'm curious to hear some opinions from serious physicists on this site as to why no top physicists have ever worked on Bohmian Mechanics. Except Bohm and Bell, the theory has received virtually no ...
10
votes
4answers
523 views

What is an interpretation of quantum mechanics?

In the sense of "Copenhagen Interpretation", what exactly is an interpretation? What purpose does an interpretation serve? Can an interpretation be tested or even be correct or incorrect independent ...
1
vote
3answers
167 views

Why does the Copenhagen interpretation assert randomness if this cannot be tested?

Why does the Copenhagen interpretation of QM assert that random events occur if such a claim cannot ever be proven or disproven? A related question: How to tell if QM is really random? Edit On ...
4
votes
1answer
159 views

Does Hardy's paradox represent a proof against Bohm's interpretation of the quantum mechanics?

This is a thought-experiment, see "Quantum Mechanics, Local Realistic Theories, and Lorentz-Invariant Realistic Theories", Phys. Rev. Lett., Vol. 68, No. 20, page 2981, year 1992, that rules out local ...
2
votes
1answer
138 views

What obstacles does de Broglie's pilot theory have to overcome? [duplicate]

I have been reading through a Wired article on pilot wave theory which talks about new evidence in support of Louis de Broglie's concept of pilot theory through experiments showing that the droplet in ...
1
vote
1answer
104 views

Argument for proving that the universe must be indeterministic [duplicate]

Can there exist an argument that could be used for proving that the universe is indeterministic? If this one seems to be too strict (rigorous), I would also be interested to know a 1-sentence ...
2
votes
2answers
114 views

Unitarity and measurement

I used to believe that the wavefunction collapse came from the interaction of the system we want to measure {S} with the measurement apparatus {M} : {S} undergoing a non unitary transformation, but ...
1
vote
0answers
48 views

Many Worlds or Infinite Worlds?

Looking at the latest paper to deal with the topic: where it purports to show that QM can be recovered from the interactions of a multitude of Newtonian worlds, we have the following statements: ...
0
votes
0answers
36 views

Arrow of Time in Information transfer

I am writing a sci-fi script and need some legitimate theory to back up a central story element (so there's no real world application): Could there be a logically consistent theory supporting the ...
0
votes
0answers
85 views

I don't get the concept of “God plays with dice” - In what scenario is it proven that he does? [duplicate]

Does God Play With Dice? by Stephen Hawking I am no physicists, but I don't get the concept of God playing with dice. Logic shows me that the entire universe is calculated very precisely according ...
0
votes
1answer
95 views

Atom in a box and collapse of the wave-function

Suppose I have an atom trapped in an optically transparent box. I'm assuming the atom is bouncing off of the walls and not bonding, i.e. the center of mass of the atom experiences a square well. Now ...
0
votes
0answers
34 views

How would the transactional interpretation “bootstrap”

I have an interest in quantum physics and have been trying to educate myself here, other places on line and by reading "The Quantum Universe". During this process I became quite drawn to the ...
0
votes
0answers
58 views

Bell's inequality

For a project, I'm planning to study Bell's inequality, which as far as I can gather is taken to rule out hidden variable theories of QM. I'm looking for recommendations of decent sources which derive ...
2
votes
3answers
188 views

What is the best article presenting counterarguments to a many-world interpretation? [duplicate]

I'd like to see a clear overview of why the many-world interpretation (WWI) of quantum is wrong, written by someone who believes that. This would be aimed at a technically aware audience, yet as an ...
0
votes
1answer
69 views

Entanglement Distillation - Interpretate a protocol

I have a general question to the interpretation of a enganglement distillation protocol. In general you have a set of entanglet qubit pairs in a Werner-state. Point of matter of this is that I can ...