Wave function collapse Definition and 89 Threads

I've recently been reading the book The Dancing Wu Li Masters which is supposed to be a very basic introduction to quantum physics. I have a question on the following quote: "Up to now, we have said that the collapse occurs when somebody looks at the observed system. This is only one point of...

While I was daydreaming in my boring math class today I came across a weird problem. What ACTUALLY causes a wave function to collapse. I had a discussion with my teacher the week prior and she was telling me that it has something to do with your brain. I didnt really believe her, I just thought...

The hypothesis that a conscious observer collapses the wave function has been discarded, right? The real reason is that the particle you use to measure the other disrupts the wave function, forcing it to choose an eigenvalue. So since we are able to remove the conscious observer as the...

Hi, I was wondering whether we are sure (I know, strong word) that decoherence is the mechanism that takes us from the quantum world to our classical world. Correct me if I'm wrong, but basically decoherence is a phenomenon where we have a bunch of quantum states that, when piled onto each...

Does the measurement problem ("wave function collapse") or something similar somehow manifest itself in QED and other quantum field theories? Is it somehow built-in into the propagators etc. "away from sight"? If so, how does it affect the theories and is this a problem, which needs to be...

Hey. Given that if you measure the energy of a wave function, the wave function must collapse to the eigenstate corresponding to the eigenvalue measured. Does that mean when you measure the energy of a wave function it must collapse the wave function into one of these stationary states...

I came across this statement by bhobba in another thread and it got me to thinking, if the "environment" itself is capable of collapsing the wave function, then how is it possible to produce an interference pattern in a double slit experiment? After all, the particle isn't traveling through a...

In QM theory entangled particles or photons are in superposition for spin (spin up or spin down) or for polarization angles. When one of the space like separated pair is measured for a spin or polarization observable, the wave function collapses and the other particle is then in a...

In flat spacetime, there isn't any problem with wave function collapse. I think that's the "textbook" position, although the only citation I have off the top of my head is the discussion in http://arxiv.org/abs/0706.1232 (section 1.1). How about in curved spacetime (working in the regime where...

Apologies if these questions have been answered before - I didn't have any luck with google. Something has bugged me for a while about quantum experiments like Schrödinger's cat where a 'black box' system is theorized to be in a superposition of states until observation causes wave function...

I don't want to argue about whether the notion of "wave function collapse" is a good way of understanding quantum mechanics, or not. For the purposes of this discussion, let's just adopt uncritically the naive approach to quantum mechanics, that: Between measurements, the system evolves...

Hi, I've done a lot of personal research on the internet trying to understand what exactly is happening in this experiment but I keep seeing contrasting information about what the role of observation actually had on the experiment. What I understand is that when they try to figure out which...

I was trying to understand wave function collapse in terms of superposition, but I ran into some problems when relating back to information theory/entropy. It is given in the definition of information in terms of entropy energy is needed to transfer information. That is something we have always...

Homework Statement A particle is in the state 1/2 |1> - 1/2 |2> + 1/2 |3> - 1/2 |4> A detector is placed to measure state |4>. What the particle's wave function collapses into, if the detector does not find a particle Homework Equations <i|j> = delta (i, j) The Attempt at a...

i was going through the quantum mechanics book by griffith and on the very first chapter i read that the wavefunction of the quantum particle collapse on measurement. and if the interval between the succesive measurement is shorter the particle will be found at the very same location. the...

I have some doubts about the implications of the orbital angular operators and its eigenvectors (maybe the reason is that I have a weak knowledge on QM). If we choose the measurement of the z axis and therefore the Lz operator, the are the following spherical harmonics for l=1...

I'm curious as to whether or not there is a connection to be drawn between the phenomenon of wave function collapse and the idea of Bayesian inference. I began thinking about this within the context of one of the variants of the Monty Hall problem. If you have one kid, what's the probability...

I have what is probably a very basic question about the Schrödinger's cat thought experiment. As I understand it, in order for the counter tube to break and release the deadly poison, the Geiger counter must measure whether or not an atom decays. So, why doesn't that measurement collapse the...

I have a question regarding Young's double slits experiment. To my understanding, wave function of a photon somehow collapses according to the probability function (which has a interference pattern). But at the very moment the wave hits the screen, it seems to me that there should be no...

consider a atom who's single electron is made to jump into conduction band ,after some time the electron will come into it's valence band by releasing the quanta of energy but if an observer observes the electron in it's excited state continuously it's wave function will collapse to bring about...

The postulates of quantum mechanics include: (1) Schrodinger's equation describes how the wave function of a system changes over time, and appears to make the wave function continuous over time. (2) When a measurement is made of quantity m, the wave function instantly changes to an...

I’ve been fascinated with the different QM interpretations since I discovered them… but I want to sort of restrict my imagination to more solid ideas. I know about the Double-Slit experiment and that there are many misconceptions about the correct definition of an ‘observer’ and what role the...

Hello: I know it's a rather subjective title. But I am no expert in the subject and I've read a lot of information in the Internet that is contradictory. I have read that the collapse of the wave function requires interaction with an observer. But is that collapse in any way related to the...

Hi. I have a simple question- Does the wave function describe probability of finding a particle in a certain state upon collapse of the wave function?

N.B. I am not trying to send information back in time or generate infinite free energy (also I couldn't find how to delete the other thread but could a moderator please delete it for me) If you could send classical information signals faster than light, then according to relativity you could...

I'm still wrestling with the whole uncertainty principal / wave function collapse idea. Obviously a basic building block of QM, I'm having a hard time understanding the real world evidence which supports these QM piles. 1. So from my understanding, the uncertainty principle tells us it is...

Hi. I've asked the question many times (as I'm sure many others have) why does the particle behave differently once it has been observed? Does that not mean it knows it has been observed? How does it know? The only answer I get is: "observing destroys the wave function" , but that doesn't...

It is my understanding that a measurement of S_z followed by a measurement of S_y will result in a particle which is in an eigenstate of S_y . But it appears that a measurement of say S_y followed by a measurement of S_x results in zero. I see this from a question in which I am asked to...

Hello, I'm new to Physics Forums, so I apologize if this question seems somewhat uninformed, but I have recently started studying quantum mechanics, and was curious about the idea of the wave function collapse, and how, from what I can tell, it seems to be approached completely independently...

Sorry for a (maybe) dumb question, but... I understand that according to QM, the description of the situation for a particle or system is described by a linear superposition of the wave functions of all the possible states (eigenstates) of the system. When a measurement is made, the wave...

Sorry people but some quantum mysteries look quite trivial to me. Wave function collapse for photons is actually subsampling of whole sample of photons. That way wave function collapse can happen instantaneously in the whole experimental setup or even backwards in time. Photon entanglement...

What about the act of observation actually causes a particle to break the superpostion and "decide" what its state is? What property does the observer posses that changes the the way particles behaves?

http://arxiv.org/abs/0902.1464 Does wave function collapse cause gravity? Authors: Lajos Diósi (Submitted on 9 Feb 2009) Abstract: We give a twist to the assumption - discussed in various earlier works - that gravity plays a role in the collapse of the wave function. This time we discuss...

As far as I understand it, an electron exists as a probability cloud around an atom, representing all the possible places it could be. Then when we make an observation the wave function collapses to one point where we see the electron. So what happens if we keep looking at it? Does the elctron...

why is not need for introducing a true collapse in bohmian interpretation?

Why is it that when observing an electron or photon it causes the wave function to collapse, surely the photons that cause this collapse were still "colliding" with it when we wern't looking. Or does it only collapse the wave function from the observers viewpoint? (I'm abit of a noob so if...

Hello. In QM we can determine the probability of any event ocurring given the wavefunction. Once we actually take a measurement the particle 'picks' a state to be found in. so my question is how do we know a priori that the particle is in two or more states at the same time before we make a...

Scientists wan't to know where wave function collapse occures. I have found at least one. Take the experiment of shooting electrons through two holes that are close together and seeing where they land at a detection screen on the other side. If you shut one hole you get a particle or lump...

Hate to ask another one of these questions, but I've just read something about the collapse of the wave function that does not seem consistent with other accounts I've read about it. From what I understand, the wave function of a system is collapsed automatically by interaction with another...