Does the wave function spread more quickly after it is observed?

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Discussion Overview

The discussion revolves around the behavior of the wave function, particularly its spreading characteristics after a measurement is made, with a focus on position measurements. Participants explore the implications of wave function collapse, the Heisenberg Uncertainty Principle, and the relationship between measurement and wave packet dynamics. The conversation touches on theoretical aspects, experimental observations, and thought experiments related to quantum mechanics.

Discussion Character

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

Main Points Raised

  • Some participants propose that the wave function collapses to a few states upon measurement, leading to a tighter wave packet and increased uncertainty in momentum, which may cause the wave function to spread more quickly afterward.
  • Others argue that the spreading of the wave function after collapse and before collapse is governed by the same Schroedinger equation, suggesting that the equation's consistency does not imply identical behavior in different scenarios.
  • A participant mentions that if a particle is observed in an energy eigenstate, it should not spread at all, indicating that the behavior of the wave function can depend on the nature of the measurement.
  • Some participants express uncertainty about whether the spreading of the wave function can be directly attributed to its collapse, raising questions about different types of measurements and their effects.
  • A thought experiment is introduced regarding a photon passing through a clear film that records its position, questioning whether this would lead to faster spreading compared to other measurement methods.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the wave function spreads more quickly after measurement. There are multiple competing views regarding the implications of wave function collapse, the role of the Schroedinger equation, and the effects of different measurement techniques.

Contextual Notes

Participants note that the behavior of the wave function is influenced by the specific conditions of measurement and the initial state of the system. The discussion highlights the complexity of quantum mechanics and the need for careful consideration of different scenarios.

  • #31
Sciencemaster said:
Of course, I could be wrong, I am human after all. The skeptical emoji is making me nervous...
The Internet is awash with simulations and lectures on the free particle wave-packet:



 
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  • #32
Honestly, I was hoping for an interactive simulation. I was hoping to create something like the first video, but then partway through collapse the wave function. Reflecting on this further, I can better say this as the collapse of the wave function creating a wider spread in the momentum space wave function through the Fourier Transform, which does indeed seem to happen, please correct me if I am wrong.
 
  • #33
Sciencemaster said:
Honestly, I was hoping for an interactive simulation. I was hoping to create something like the first video, but then partway through collapse the wave function. Reflecting on this further, I can better say this as the collapse of the wave function creating a wider spread in the momentum space wave function through the Fourier Transform, which does indeed seem to happen, please correct me if I am wrong.

That's correct. A wave function with a narrow spread in position has a broad spread in momentum. That is the uncertainty principle. However, this does not say anything about how the spread changes with time.
 
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