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2answers
61 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
60 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
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3answers
603 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
1answer
210 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
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4answers
609 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 ...
0
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1answer
55 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, ...
6
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2answers
567 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 ...
4
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2answers
156 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) ...
2
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0answers
64 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 ...
3
votes
1answer
314 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
140 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
51 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
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4answers
1k 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
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3answers
122 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 ...
6
votes
2answers
505 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
222 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
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3answers
192 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
111 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
72 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?
3
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4answers
124 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
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1answer
80 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 ...
0
votes
2answers
63 views

Superpositions and expectation values in quantum mechanics

When the wavefunction of a particle is not an eigenfunction of an operator, the property to which the operator corresponds does not have a definite value, Why? Also consider a linear combination of ...
0
votes
1answer
97 views

Postulate of Quantum Mechanics on Wavefunction collapse [closed]

There is a postulate in quantum mechanics about wavefunction collapse. Can anyone provide me some intuitive perspective into it along with the concept of projection (I mean mathematical treatment).
0
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1answer
63 views

How can we “know” that system interacted with another system or environment in quantum mechanics/decoherence?

I might be raising measurement problem in quantum physics in different words, but I will ask the question. Quantum decoherence has been proposed by proponents as a theory that eliminates all weird ...
4
votes
3answers
149 views

When you measure position of an electron in a energy pure state, what happens to the energy?

When you measure the position of an electron that is in a pure energy state, what happens the energy becomes non-deterministic. That is future measurements of energy can only be predicted with respect ...
0
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2answers
204 views

Can you read and write a quantum state to a particle without collapsing its probability field?

I know the main problem with a quantum computer is that you can't read and write data from it until after it has run though all of its calculations. But would reading and writing quantum data to ...
2
votes
2answers
99 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 ...
2
votes
3answers
164 views

Wavefunction collapse to a state that seems impossible

Let $\Omega$ be an observable and let $\Psi = \sum a_i\phi_i$ be a decomposition of a state of a system (satisfying the Schrödinger equation) in eigenfunctions of $\Omega$ (assume for simplicity it is ...
1
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0answers
109 views

Beginner Quantum Mechanics Questions and Theories [closed]

So, I recently read the following article: http://www.preposterousuniverse.com/eternitytohere/quantum/ and I have some questions on some of the things it discussed, as well as some theories of my ...
0
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0answers
42 views

Double slit experiment using 2 electrons

Suppose 2 electron guns shoot an electron at a double slit at the same time, then how do you predict for each electron the probability density of it landing at each position when the 2 electrons repel ...
1
vote
1answer
104 views

Understanding wave functions

I'm currently writing an essay on the measurement problem, and I'm not quite certain that I've fully understood the purpose of the wave function, in that does the following sentence make sense with ...
0
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0answers
101 views

Examples of symmetric field collapse to produce asymmetry

It would really help me with an idea I have if I could see how something such as a symmetric field could collapse to something asymmetric. I know that if $x$ occures before $y$ is symmetric, then $y$ ...
1
vote
1answer
113 views

Collapse of the Free Particle Wave Function

The time evolution of the one-dimensional quantum mechanical free particle ($V(x) = 0$ $\forall x$) is described by the following Schroedinger equation $ -\frac{\hbar^2}{2m}\frac{\partial^2 ...
0
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0answers
22 views

Average value of consecutive measurements of two observables

Suppose we had two boxes named "1" and "2", and suppose we can measure observables $A_1$ and $A_2$ from these boxes, respectively. $A_1$ and $A_2$ commute, meaning we can find a basis of simultaneous ...
1
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1answer
152 views

Are we so sure about superposition?

Apparently particles can be anywhere when not observed. How strong is this theory really? Okay the wave-function can be collapsed through observation but how are we so sure that when an object is not ...
0
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1answer
115 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 ...
-3
votes
1answer
80 views
1
vote
3answers
261 views

How does wave function collapse when I measure position?

Text books say that when you measure a particle's position, its wave function collapses to one eigenstate, which is a delta function at that location. I'm confused here. A measurement always have ...
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votes
7answers
6k views

Why does observation collapse the wave function?

In one of the first lectures on QM we are always taught about Young's experiment and how particles behave either as waves or as particles depending on whether or not they are being observed. I want to ...
1
vote
1answer
96 views

Does light or observation collapse wave functions? [duplicate]

I hear that observation is what causes the wave function collapse, but that doesn't make sense considering that an eye or camera is just a physical system with no particularly special properties. In ...
-1
votes
2answers
101 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. ...
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6answers
993 views

Is there a difference between observing a particle and hitting it with another particle?

First, let me state that I'm a lot less experienced with physics than most people here. Quantum mechanics was as far as I got and that was about 9 years ago, with no use in the meantime. A lot of ...
3
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1answer
131 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 ...
13
votes
4answers
530 views

How is it possible that quantum phenomenons (e.g. superposition) are possible when all quantum particles are being constantly observed?

I don't understand how quantum mechanics (and therefore also quantum computers) can work given that while we work with quantum states, particles that this quantum state consist of cannot be observed, ...
8
votes
3answers
281 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 ...
-5
votes
1answer
126 views

Collapse in Quantum Field Theory? [duplicate]

I do not want answers telling me that wave-function collapse is not real and decoherence is the answer (I know the situation with that). I am asking a question purely on the basis if wave-function ...
2
votes
5answers
259 views

The quantum state just after a position measurement

The wave function of a free particle is given as, $$\psi(x) ~=~ e^{-{ x }^{ 2 }/{ a }^{ 2 }}.$$ Then a position measurement is made and the position of the particle is found to be at $x=a$. My ...
2
votes
0answers
107 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 ...
0
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3answers
204 views

Why does a wavefunction collapse when observation takes place?

Why does a wavefunction collapse when observation takes place? Can this question be explained in non mathematical terms? I have tried finding the answer but couldn't find a clear explanation.
5
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2answers
145 views

Inexact measurement and wavefunction collapse

As is usually said, measurement of an observable $q$ leads to collapse of wavefunction to an eigenstate of the corresponding operator $\hat q$. That is, now the wavefunction in $q$ representation is ...