Importance of the observer in double slit experiment and entanglement

In summary, the conversation discusses the double slit experiment and entanglement in quantum mechanics, and how the observer's role in these phenomena is still not fully understood. Several interpretations of quantum mechanics are mentioned, but no one knows for certain what is occurring. The conversation also references the Wheeler's delayed choice experiment and the delayed choice quantum eraser, which involve picking a measurement at a later time that can affect past measurements. The conversation also mentions some mathematical explanations and resources for further understanding.
  • #1
Quarlep
257
4
Hi

In double slit experiment our observe can change the past and in the entanglement our observe affact other
particle pair. How could such a thing possible ?
 
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  • #2
I don't think the observer changes the past in the double slit experiment, but in any case, both things are just quantum reality. That is, they are observed phenomena.

In entanglement, the observer is not actually changing the "other" particle, he/she/it is defining the combined state of the particle-pair. What's weird is that it happens FTL, but no useful information is transmitted.
 
  • #3
Quarlep said:
How could such a thing possible ?

Welcome to PhysicsForms, Quarlep! A few comments to add to what phinds said.

There are several interpretations of Quantum Mechanics which are intended to account for these. And each has its own drawbacks as well. A few examples are: Many Worlds, dBB/Bohmian Mechanics, Time Symmetric, etc.

No one truly knows what is occurring. And yet, the current understanding is good enough that many experiments can be conceived, predicted and explained.
 
  • #6
It was good so it is evindence of my idea isn't it
 
  • #7
In the delayed choice quantum eraser you do not actually change the past. In a nutshell you can pick at a later point in time whether you want to perform a measurement which allows you to gather some more information about a second measurement done in the past or a measurement which does not allow you to do that.

One can give a more detailed description, but it involves quite some math. I am not sure you want the details.
 
  • #8
I wiil glad if you share it
 
  • #9
I didnt understand it. Can you explain it more simple.
I will be glad if you show me the math.And this idea is proved or its just
a mathematical explanation of this if its I want to learn other ideas.
 
  • #10
I posted the in-a-nutshell version here:

https://www.physicsforums.com/showpost.php?p=2241460&postcount=8

This is aimed at a version of the delayed choice quantum eraser done in the version by Kim et al.

The double slit version used by Walborn and others is maybe best explained by Walborn himself in the following paper: http://arxiv.org/abs/1010.1236.

You will find the important results around page 52. Equation 96 is especially important. It gives you coincidence count rates. They explain how to get conditional fringes and you can play around with that equation for yourself to check the influence of detector size or other important parameters. The equation is rather lengthy, though.
 
  • #11
Thank you very much
 

Related to Importance of the observer in double slit experiment and entanglement

1. What is the double slit experiment and why is the observer important in it?

The double slit experiment is a fundamental experiment in quantum mechanics that demonstrates the wave-particle duality of matter. It involves firing particles, such as photons or electrons, through two parallel slits and observing the resulting interference pattern on a screen. The observer is important in this experiment because the act of observation collapses the wavefunction of the particles and determines the outcome of the experiment. This phenomenon is known as the observer effect.

2. How does the observer influence the outcome of the double slit experiment?

The observer influences the outcome of the double slit experiment by collapsing the wavefunction of the particles. This means that the particles are forced to behave either as particles or as waves, depending on whether they are being observed or not. This effect is not fully understood and is still a subject of debate among scientists.

3. What is the role of the observer in the phenomenon of entanglement?

In the phenomenon of entanglement, two or more particles become connected in such a way that the state of one particle is dependent on the state of the other particle, regardless of the distance between them. The role of the observer in entanglement is similar to that in the double slit experiment - the act of observation collapses the wavefunction and determines the state of the particles.

4. Can the observer be eliminated from the double slit experiment and still obtain the same results?

No, the observer cannot be eliminated from the double slit experiment without changing the results. The observer is an essential part of the experiment and without their presence, the particles would not collapse into a definite state and the interference pattern would not be observed.

5. What are the implications of the observer's role in the double slit experiment and entanglement?

The observer's role in these experiments raises questions about the nature of reality and the role of consciousness in shaping it. It also challenges our understanding of cause and effect, as the act of observation seems to influence the behavior of particles without any direct physical interaction. These implications have sparked numerous philosophical and scientific debates about the nature of the universe and our place in it.

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