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2
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0answers
98 views

Can the Born rule be derived? [duplicate]

$\renewcommand{ket}[1]{|#1\rangle}$ If we have a particle and we know the initial state $|\psi\rangle$ of everything that is relevant, and we know the full Hamiltonian $H$, then we should be able to ...
3
votes
3answers
183 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 ...
3
votes
1answer
207 views

Has this experiment really demonstrated wave-function collapse?

My question is: why did the following experiment claim that it had demonstrated the wave-function collapse? http://www.nature.com/ncomms/2015/150324/ncomms7665/full/ncomms7665.html I would have no ...
3
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2answers
256 views

How is decoherence due to the environment compatible with the Copenhagen interpretation?

Let's say that "decoherence" is that transition from a pure quantum state to a mixed state due to interactions with the environment. (A reasonable definition?) How is that compatible with the ...
6
votes
2answers
103 views

What state the wave function collapses into after an inaccurate measurement?

I'm watching MIT online lectures Quantum Physics I (roughly from one hour mark in the video). The lecturer explains wave functions that describe "Stationary States" that consist of a single energy ...
2
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1answer
121 views

Transition from one state to another in Quantum Mechanics

When we measure an electron's position we know that the wave function $\psi$ peaks at the measured position and the wave function as a function of momentum is a harmonic function. When it makes the ...
2
votes
3answers
172 views

What does quantum phenomena exist as prior to observation?

It's been said that according to the Schrodinger equation, independent of observation, particles exist in a state of a wave function, which is a series of potentialities rather than actual objects. ...
0
votes
5answers
114 views

Does measurement change the evolution of wave function?

Basically any measurement is on wave function $|\psi\rangle$ is done by operator $X$ such that $X|\psi\rangle$ results observable $x$ with some probability. But what happens to $|\psi\rangle$? Does ...
-2
votes
2answers
94 views

The relation between classical from quantum vs measurement problem

What is the relation between classical from quantum vs measurement problem. On the one hand they seem to be related on the other they seem to be of different nature. We always see our screens in ...
-1
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2answers
124 views

Doesn't Schrodinger's Cat depend on whether there's a quantum/classical boundary?

Everyone knows how Schrodinger's Cat is set up, so the question becomes whether there's a quantum/classical boundary and what that boundary is. Some people say everything is quantum while some may ...
0
votes
1answer
195 views

Is something beyond the material needed to solve the Von Neumann Chain?

A problem has been presented that goes like this: Particles normally exist as several mathematical possibilities rather than one actual object. It is said that in the absence of observation, ...
1
vote
1answer
54 views

Compatible Observables and Measurement

Suppose $A$ and $B$ are compatible observables (i.e. $[A,B] = 0$). We take the eigenkets of $A$ to be $|a_1 \rangle \ldots |a_N \rangle$. Further, we suppose that the first $k$ eignekets of $A$ are ...
6
votes
4answers
326 views

Is a photon always in a state of superposition while traveling through space?

In the double-slit experiment, we emit a photon that is in a state of superposition (wave form) which travels through both slits to interfere with itself. When we measure which slit it went through, ...
0
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2answers
138 views

Why superpositions? [closed]

I've seen a lot of stuff on superpositions, namely the double slit experiment. And every video I watch, it tells me the same thing: It's amazing that when these particles are being observed they ...
0
votes
2answers
42 views

What the wave function looks of a particle in the infinite square well looks like after collapse for measurements of position and energy

Consider a particle in a the infinite square well from x=0 to x=L. At t=to, I make a measurement of position and get x=L/2. What is the resulting wave function at t=to? My understanding, from reading, ...
1
vote
5answers
139 views

The nature of measurement

Does the measurement of the particle change it's physical state? Or does it only seem to do that? Ex. if a particle was measured before the slits, would we see an interference pattern, or a particle ...
19
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4answers
658 views

State collapse in the Heisenberg picture

I've been studying quantum mechanics and quantum field theory for a few years now and one question continues to bother me. The Schrödinger picture allows for an evolving state, which evolves through ...
2
votes
2answers
164 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 ...
0
votes
1answer
51 views

Time reversal on superposition: I think [duplicate]

Imagine I have a box, and in it, I have a photon in a superposition of state |1> and |0>. I look into the box and register that the photon is in state |1>. Now, if I have ALL information in the ...
0
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2answers
112 views

Eigenstate vs collapsed wave function

An eigenstate, or determinate state, is a state where the measurement of some observable always yields the same result. This means that the standard deviation of the observable is zero. If a ...
2
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2answers
58 views

Eigenstates into which a system can be projected after a measurement

I'm currently reading Dirac's Principles of Quantum Mechanics, on page 36, he says: Another assumption we make connected to the physical interpretation of the theory is that, if a certain real ...
4
votes
3answers
743 views

What happens after the collapse of a wavefunction?

If I have a quantum system which I prepare in a certain state, this state then evolves unitarily via a Hamiltonian. Suppose an observer provokes a collapse of the wave function by a certain ...
1
vote
2answers
156 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 ...
0
votes
3answers
165 views

Why does the electron wave function collapse in a double slit experiment?

Did the electron wave function collapse in the double slit experiment due to being observed, OR is it that the electron wave function collapsed because the instrument used to measure it physically ...
10
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3answers
1k 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 ...
1
vote
2answers
206 views

Why isn't transformation, caused by measurement, unitary?

It is said, that when measured, a quantum system undergoes "wave function collapse", which is a non-unitary transformation. Why? The wave function is $\Psi = \alpha \left|0\right\rangle + \beta ...
4
votes
2answers
176 views

Without apparatus can we say that the system is measured(decohered) by the environment?

"Einselection" and "tridecompositional uniqueness theorem" seem to resolve the preferred basis problem. But the premise is that there are three parts in discussion.(system, apparatus, environment) ...
0
votes
1answer
118 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 ...
3
votes
5answers
348 views

How does a Wavefunction collapse?

I have been wondering and researching... How does a wavefunction collapse into one state?More specifically, what conditions cause a wavefunction for a quantum particle to collapse? Does this have to ...
1
vote
1answer
80 views

What are observables? [closed]

What are observables and how are they related to quantum decoherence and wavefunction collapse. I read this: Observables - what are they? but it was about the technical details on observables. Even ...
2
votes
4answers
830 views

Decoherence and collapse

It is said that the decoherence does not solve the problem of measurement and/or the emergence of classicality, can somebody explain it with simple analogies or in a manner accessible to a ...
2
votes
2answers
98 views

Wave Function Collapse Versus Decoherence

I'm aware that wave function collapse is still a topic of debate-and that decoherence is a pretty good explanation for how things might approach wave function collapse, in some sense. But the way I've ...
0
votes
2answers
172 views

Collapse of the wave function and Heisenberg uncertainty

I have been studying quantum mechanics for a few weeks, in particular wave mechanics, as created by Schrodinger, and his equation. As a high school student, I haven't found an answer to this question ...
0
votes
1answer
89 views

Decoherence, collpse, and WHEN does the collapse occur?

The idea that decoherence stands behind the so-called collapse (reduction) of the wave-function doesn't seem satisfactory. Consider a quantum particle whose wave-function is of the form (1) ...
2
votes
1answer
237 views

Can the time direction of wave function collapse be reversed? [duplicate]

The laws of physics are invariant under CPT transformations reversing time, inverting space and flipping charges. Almost so. The collapse of the wave function is the odd man out. Can the time ...
3
votes
4answers
832 views

Is the wave function of a particle re-created after a measurement stops?

Yeah, I haven't quite understood, or been told, what happens to, for example an electron and it's wavefunction, when you stop to measure it? I mean, an electron has a wave function describing it's ...
7
votes
2answers
780 views

DIY Quantum Eraser Experiment by the Scientific American: Is this really quantum?

Click here for the publication. Having performed this experiment, I have gotten clean results. Essentially, a double slit is made by putting an photon beam in the way of a wire with orthogonal ...
2
votes
0answers
66 views

Quantum Mechanics and Direction of time [duplicate]

It has always fascinated me that time is symmetrical in classical physics while, in life, we all experience the flow of time in only one direction. There is no preference as to the direction of time ...
4
votes
1answer
416 views

If there is no collapse of the wave-function does this mean that the many worlds interpretation of QM must be wrong?

If as some people suggest, there is no collapse of the wave function (is there a standard name for this position), then must one rule out the many-worlds interpretation of QM?
4
votes
2answers
153 views

Does $\sigma_x\sigma_p = 0 \cdot \infty$ after a measurement of particle position?

I feel this question has an obvious answer that I should have been able to find independently, but I've searched for a while now it hasn't clicked. When position is measured, the uncertainty of the ...
2
votes
2answers
58 views

Observing a particle over a certain domain

I was just thinking: in Quantum Mechanics, we start out with that whole collapsing business by observing the x position of a particle. I was thinking: why do we have to do that? What if we only ...
4
votes
4answers
2k views

Does the observer or the camera collapse the wave function in the double slit experiment?

Ok so if we setup a camera before the slit we will find a single photon and will follow through accordingly, likewise by having a camera setup after the slit, we can retroactivly collapse the wave ...
0
votes
3answers
141 views

Discrete movement vs wave function collapse

I remember once, as a child, thinking that objects do not really "move," but that at a very small scale they would have to "disappear" and then "appear" again at their newly shifted position, just the ...
7
votes
2answers
625 views

Has the collapse of wave function due to observation been recorded?

I've seen pictures like this one, which depict the outcome of the Double-slit experiment with wave-like or particle features, depending how measurement has taken place. The graphic showing ...
9
votes
3answers
242 views

Does quantum collapse involve a loss of information? Does it require energy as suggested by the Landauer Limit?

I read in the context of quantum computing or of the minimal energy required for computation that there has to be a minimum possible amount of energy required to change one bit of information, called ...
1
vote
3answers
206 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 ...
0
votes
1answer
214 views

Double-slit-experiment but with unobserved alternating opening of slits. Does an interference pattern still arise?

Step #1 Imagine one preforms an electron based Double-slit-experiment and one does so with only one electron being fired at a time. Step#2 Also included in the experiment is an unobserved ...
4
votes
1answer
87 views

Where does either Bohr or Heisenberg mention the idea of the wave function collapsing?

Could someone reference a paragraph written either by Heisenberg or Bohr where they mention the idea of the wave function collapsing?
4
votes
4answers
182 views

What exactly is meant by “observed” when talking about the wave-particle duality?

When talking about the wave-particle duality, teachers and books say that when you send a single photon through a slit, it makes a wave pattern. But if you send that particle through the slit and "you ...
1
vote
1answer
93 views

A well-defined quantum probability in the beginning of the universe?

In mathematics or statistics, a well defined probability requires a large sample space. However, in the beginning of the universe, when the first quantum collapse happened, the sample space contains ...