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

In summary, the wave function collapses when a measurement is made, but then immediately starts to spread out again according to the Schrodinger equation. This can lead to a fuzzy state for the particle's position. The simulation at phet.colorado.edu/en/simulation/quantum-tunneling shows how the wavefunction evolves over time, and there is a button to make a quantum measurement and collapse the wavefunction. However, for macroscopic particles, wave properties are usually not observable due to their short wavelengths.
  • #1
wolfy
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TL;DR 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
 
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  • #2
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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  • #3
Look at this simulation: https://phet.colorado.edu/en/simulation/quantum-tunneling

This shows how a wavefunction evolves in time according to the schrodinger equation (at least for scattering states). There is a button that says "make quantum measurement" which will collapse the wavefunction.
 
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  • #4
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?

.
 
  • #5
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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  • #6
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 schrodinger 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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  • #7
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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  • #8
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
 
  • #9
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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  • #10
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.
 
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  • #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 schrodinger 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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Related to When the wave function collapses, how long is it collasped?

1. How long does the wave function stay collapsed?

The duration of the wave function collapse can vary depending on the specific system and measurement being observed. In some cases, it may only last for a fraction of a second, while in others it can persist for much longer. The collapse is typically considered to be instantaneous, but the effects of it may be observed over a longer period of time.

2. Can the wave function collapse multiple times?

Yes, the wave function can collapse multiple times within a single system. This can occur when multiple measurements are made on the same system, causing the wave function to collapse and then reform multiple times. It is also possible for the wave function to collapse and then reform due to interactions with other systems or particles.

3. Does the collapse of the wave function follow a predictable pattern?

No, the collapse of the wave function is considered to be a random process. It cannot be predicted exactly when or how the collapse will occur. However, the probability of the wave function collapsing to a certain state can be calculated using the Schrödinger equation.

4. Is the wave function collapse a physical or mathematical phenomenon?

The wave function collapse is a fundamental aspect of quantum mechanics, which is a mathematical framework used to describe the behavior of particles at the subatomic level. While it is a mathematical concept, the collapse of the wave function has been observed in experiments and has real-world implications.

5. Can the collapse of the wave function be reversed?

No, once the wave function collapses, it cannot be reversed. This is due to the irreversible nature of quantum measurements. Once a measurement is made, the state of the system is determined and the wave function collapses to reflect this new information. However, the wave function can continue to evolve and change over time through quantum processes.

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