Probability Amplitude: Understanding Photons

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Discussion Overview

The discussion revolves around the nature of photons, particularly focusing on their paths, probability amplitudes, and interactions with other particles. Participants explore the implications of quantum mechanics on the understanding of photons, debating whether they possess a defined path or properties that can be ascribed to them.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants assert that a photon does not have a path, suggesting that this is dependent on interpretation.
  • Others argue that the absence of a position operator for photons implies they cannot be said to have a path.
  • There is a contention regarding the interaction of photons with electrons, with some participants asserting that common sense implies photons must have a path.
  • One participant notes that while light may have a path, it does not mean that photons do, emphasizing the difference between classical and quantum perspectives.
  • Concerns are raised about the implications of describing photons as particles, particularly due to their lack of rest mass and the complexities this introduces.
  • Participants discuss the concept of polarization in relation to the orientation of photons, questioning how this fits into the broader discussion of their properties.

Areas of Agreement / Disagreement

Participants express differing views on whether photons have a defined path, with no consensus reached. The discussion remains unresolved regarding the implications of quantum mechanics on the nature of photons and their interactions.

Contextual Notes

The discussion highlights limitations in understanding due to the abstract nature of quantum mechanics and the potential misalignment between common sense and quantum behavior. The lack of a clear definition of "path" for photons is a recurring theme.

Daniel Petka
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https://www.physicsforums.com/attachments/197770The path of a photon is a perfect straight line not a sine wave, right? (if the probability amplitude is zero)https://www.physicsforums.com/attachments/197771
 

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The y-axis is the strength of the electric (or magnetic), field, not a position.

A photon does not have a path.
 
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Daniel Petka said:
The path of a photon is a perfect straight line not a sine wave, right? (if the probability amplitude is zero)
The attached image is a graph showing the strength of the electric and magnetic fields associated with a classical electromagnetic wave at different places at the same time. It has nothing to do with photons (which, as mfb says, don't have a path).
 
mfb said:
A photon does not have a path.
This is interpretation dependent statement.
 
How can this be interpretation dependent statement if there is no position operator for photons (which AFAIK is not interpretation dependent)?
 
If a model would make prediction that leads to discontinuous path for a photon you could say that photon does not have a path. If a model is silent on the matter you can't draw any conclusions from that.
 
If a photon doesn't have any path, how can it then interact with let's say only electrons in front of him? Common sense tells me that light must have a path.
 
Daniel Petka said:
If a photon doesn't have any path, how can it then interact with let's say only electrons in front of him? Common sense tells me that light must have a path.

Why do you think a photon has the property of something in front of it?

As has been said many times before be very careful of ascribing properties to quantum objects independent of actual observation.

QM and commonsense are not necessarily the best of friends.

Thanks
Bill
 
Daniel Petka said:
Common sense tells me that light must have a path.
Light has a path, but that doesn't mean a photon does. A beam of light is not a stream of photons flowing by the way a river is a stream of water molecules flowing by.

Our common sense comes from a lifetime of experience with macroscopic objects obeying the laws of classical physics, so doesn't work especially well for quantum objects. Your common sense was already leading you astray when it tempted you to think about how a photon might interact with an electron "in front" of it; what does "in front" or "behind" mean for something that has no position?
 
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  • #10
Ok... photons are strange [emoji23]
 
  • #11
Daniel Petka said:
Ok... photons are strange [emoji23]
They are indeed... much of the problem comes from the word "particle", which as used in quantum physics doesn't mean at all what you'd expect from the common English-language meaning of the word. Photons are especially complicated because they have no rest mass, so cannot be treated using "ordinary" non-relativistic quantum mechanics, the stuff you study in your first few undergraduate years.

The links in the first two posts of this thread are pretty good but maybe a bit more than you're up for.
 
  • #12
OK but please don't tell me that photons don't have a 3 dimensional orientation... cause then my brain's going to explodes
 
  • #13
Daniel Petka said:
OK but please don't tell me that photons don't have a 3 dimensional orientation.
Are you referring to the polarisation here?
 
  • #14
Daniel Petka said:
OK but please don't tell me that photons don't have a 3 dimensional orientation... cause then my brain's going to explodes
I think the polarization angle lies in the plane orthogonal to the momentum. Which is only one degree of freedom.
 
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