When the wave function collapses, how long is it collasped?

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Discussion Overview

The discussion centers around the concept of wave function collapse in quantum mechanics, specifically addressing how long the wave function remains collapsed after a measurement and the implications of this collapse on the behavior of particles. The conversation includes theoretical considerations, interpretations of quantum mechanics, and references to simulations that illustrate these concepts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that after a measurement collapses the wave function, it begins to spread out again according to the Schrödinger equation, leading to a less defined position over time.
  • Others reference simulations that demonstrate how wave functions evolve and collapse, highlighting the educational value of these tools.
  • A participant questions whether the concept of wave function collapse should be understood literally or as a figurative tool for calculations.
  • Another participant suggests that the characterization of 'collapse' may not be the best term, noting that particles can persist long enough for a classical world to emerge, which is interpretation-dependent.
  • Some participants express their learning experiences and challenges with understanding quantum mechanics, indicating a personal engagement with the topic.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement regarding the interpretation of wave function collapse and its implications. There is no consensus on whether the wave function should be considered a real entity or merely a calculational tool.

Contextual Notes

Discussions include references to the Schrödinger equation and the nature of measurements in quantum mechanics, but the implications of these concepts remain unresolved and depend on individual interpretations.

Who May Find This Useful

This discussion may be useful for individuals interested in quantum mechanics, particularly those exploring the nuances of wave function collapse and its interpretations, as well as those seeking educational resources to better understand these concepts.

wolfy
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TL;DR
When wave function collapses how long is it collasped
When wave function collapses how long is it collasped...

Shooting electrons at a double slit and observing the electrons before they reach the 2 slits collasped the wave function...so is its behavior particle like forever?

Quantum mechanics is simple however wrapping ones head around it is harder than I thought it would be
 
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Measurements collapse the wave function, but in between measurements the wave function changes according to the Schroedinger equation.

So after one make a position measurement and the wave function collapses to have a fairly well defined position, it will immediately start to spread out again (according to the Schroedinger equation), and its position will become less and less well defined as time passes.
 
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Look at this simulation: https://phet.colorado.edu/en/simulation/quantum-tunneling

This shows how a wavefunction evolves in time according to the Schrödinger equation (at least for scattering states). There is a button that says "make quantum measurement" which will collapse the wavefunction.
 
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wolfy said:
Summary:: When wave function collapses how long is it collasped

When wave function collapses how long is it collasped...

you ask,
How fast is the wave function collapse?

.
 
atyy said:
Measurements collapse the wave function, but in between measurements the wave function changes according to the Schroedinger equation.

So after one make a position measurement and the wave function collapses to have a fairly well defined position, it will immediately start to spread out again (according to the Schroedinger equation), and its position will become less and less well defined as time passes.
Thank you very much for your time and helping...I think I'm beginning to see what your saying. It begins reverting to it's fuzzy state again if I'm understanding correctly? Forgive me if I'm misunderstanding.
 
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Isaac0427 said:
Look at this simulation: https://phet.colorado.edu/en/simulation/quantum-tunneling

This shows how a wavefunction evolves in time according to the Schrödinger equation (at least for scattering states). There is a button that says "make quantum measurement" which will collapse the wavefunction.
Very very cool indeed. Bit of a learning curve but it is worth it.

Thank You
 
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wolfy said:
Very very cool indeed. Bit of a learning curve but it is worth it.

Thank You
Of course. And if you have any specific questions about the simulation, feel free to post it or private message me-- it's probably my favorite simulation on the site.
 
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Isaac0427 said:
Of course. And if you have any specific questions about the simulation, feel free to post it or private message me-- it's probably my favorite simulation on the site.
Your on ... And Thank You so much again for taking the time, once I get my payment options set up again I can buy the app...it's only a dollar, however just need my plastic to work...the pandemic is financialy hard on many of us
 
wolfy said:
Your on ... And Thank You so much again for taking the time, once I get my payment options set up again I can buy the app...it's only a dollar, however just need my plastic to work...the pandemic is financialy hard on many of us
Wait...what app? The simulation should be free to use.
 
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Isaac0427 said:
Wait...what app? The simulation should be free to use.
The app is at the bottom of the page I see it on my cell phone...however my computer is down so I can only use the app...it's only a dollar...hope to get it tomorrow or Friday when I get some money. I would like to ask you a question or two about it when I get it so I can accelerate the learning...I really do think it's wonderful
 
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  • #11
wolfy said:
Summary:: When wave function collapses how long is it collasped

When wave function collapses how long is it collasped...

Shooting electrons at a double slit and observing the electrons before they reach the 2 slits collasped the wave function...so is its behavior particle like forever?

Quantum mechanics is simple however wrapping ones head around it is harder than I thought it would be
'Collapse' is probably not the best characterization. We can observe at the macro scale that particles can persist for as long as necessary for the emergence of a 'classical' macro world. How that works is interpretation dependent. But there are ways to infer the wave nature of matter.
 
Last edited:
  • #12
wolfy said:
Summary:: When wave function collapses how long is it collasped

When wave function collapses how long is it collasped...

Shooting electrons at a double slit and observing the electrons before they reach the 2 slits collasped the wave function...so is its behavior particle like forever?

Quantum mechanics is simple however wrapping ones head around it is harder than I thought it would be
EPR said:
'Collapse' is probably not the best characterization. We can observe at the macro scale that particles can persist for as long as necessary for the emergence of a 'classical' macro world. How that works is interpretation dependent. But there are ways to infer the wave nature of matter.
For macroscopic particles, because of their extremely short wavelengths, wave properties usually cannot be detected
 
  • #13
Isaac0427 said:
Look at this simulation: https://phet.colorado.edu/en/simulation/quantum-tunneling

This shows how a wavefunction evolves in time according to the Schrödinger equation (at least for scattering states). There is a button that says "make quantum measurement" which will collapse the wavefunction.

I was finally able to install it tonight, learning it now, it is amazing.

Thank You.
 
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  • #14
atyy said:
Measurements collapse the wave function, but in between measurements the wave function changes according to the Schroedinger equation.

So after one make a position measurement and the wave function collapses to have a fairly well defined position, it will immediately start to spread out again (according to the Schroedinger equation), and its position will become less and less well defined as time passes.

Is this valid literally (where the wave function is real) or figuratively (where the wave function is calculational tool only)?
 
  • #15
Secan said:
Is this valid literally (where the wave function is real) or figuratively (where the wave function is calculational tool only)?
That (what @atyy said) is what the math says. That math accurately describes the behavior of the physical system, and does so whether interpreted literally or figuratively.
 
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