Can an electron be in two places at the same time?

Vishwanath Rao said:
According to the double slit experiment electron's have the properties of both waves and particles if this is true then yes they can be at two places at once but according to quantum physics anything with mass however minute cannot be at two places at once.
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Electrons have a non zero mass.
 
Vishwanath Rao said:
According to the double slit experiment electron's have the properties of both waves and particles if this is true then yes they can be at two places at once but according to quantum physics anything with mass however minute cannot be at two places at once.
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That isn't what QM says. QM says a subatomic object is described by a wave function, which allows it to have diffraction/diffusion properties even when only one object is ever measured by a detector. The mass of the object is irrelevant, both massless and massive subatomic objects display such properties. There is no contradiction, other than between your ears.

As a piece of advice, if you don't know anything about QM don't just make stuff up on a forum where numerous posters do know QM.
 
AlphaNumeric said:
That isn't what QM says. QM says a subatomic object is described by a wave function, which allows it to have diffraction/diffusion properties even when only one object is ever measured by a detector. The mass of the object is irrelevant, both massless and massive subatomic objects display such properties. There is no contradiction, other than between your ears.

As a piece of advice, if you don't know anything about QM don't just make stuff up on a forum where numerous posters do know QM.
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I don't agree Alpha!

Sometimes posting a wrong answer elicits a good explanation, as demonstrated above...
 
Querying something, asking for clarification about what turns out to be an incorrect understanding, is one thing. Stating something as if you're familiar with it but are not is a completely different thing. If no one replies to the former than it's clear to the casual reader to take it with a pinch of salt. If no one replies to the latter than it only serves to spread the lack of understanding.
 
AlphaNumeric said:
Querying something, asking for clarification about what turns out to be an incorrect understanding, is one thing. Stating something as if you're familiar with it but are not is a completely different thing. If no one replies to the former than it's clear to the casual reader to take it with a pinch of salt. If no one replies to the latter than it only serves to spread the lack of understanding.
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My previous post was actually ment as kudos, to you. With the exception of the mention of what might exist between someone's ears I thought your clarification was good.
 
AlphaNumeric said:
That isn't what QM says. QM says a subatomic object is described by a wave function, which allows it to have diffraction/diffusion properties even when only one object is ever measured by a detector. The mass of the object is irrelevant, both massless and massive subatomic objects display such properties. There is no contradiction, other than between your ears.

As a piece of advice, if you don't know anything about QM don't just make stuff up on a forum where numerous posters do know QM.
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I went back and read up on my QM sorry about the earlier lapse.
What quantum physics says is that it is not just impossible to measure the exact position of an electron; an electron *does not have* an exact position. It is always spread out over a region of space, and it interacts with other objects within or close to that region of space. So it is more correct to say that an electron can have effects at two different places at one time.
You are right there is no contradiction.But it also doesn't say an electron can be at two places at once.
 
Space and time are conceptual constructs invented by the human mind to try to make sense of the physical world.
To that end they have been extremely successful, particularly at the human and surrounding scales.
Every concept has its limitations. 'Space' and hence 'place' does not apply to electrons.
 
After watching the Hitachi video, I was left with many questions. What, if any, are the assumptions in the premise? What, if any, are the assumptions in the conclusion? In what regard does an electron exhibit particle and wave propteries? What exactly is the process by which a "slit" is created?

The first statement I heard that surprised me was that exactly one electron is released. I am curious how it is possible to know that, with what certainty, and under what conditions.

I was immediately drawn to the idea that they are seeing an artifact of spurious interference from a power supply or some oscillator in the vicinity. One would expect that a detector with one electron of sensitivity would be very hard to shield. I had to force myself to assume the entire apparatus has been thoroughly scrubbed for systemic error such as this, so I could entertain the question at hand.

I spent a few minutes wondering what kind of phenomenon would present itself as dual wave interference, not on the single electron, but on the entire population, over time, as a statistical effect. In other words, at precisely the moment the electron passes through the slit, a trajectory has been determined, but that determination includes a random component which appears sinusoidal as the final screen develops. The PDF of this random component can only be visualized in this manner by noticing that the stripes look like peaks and valleys of a sinusoid. I am now imagining an app that reads the screen coordinates of the dots and builds a data set of coordinates for further statistical analysis.

Since the release of each electron appears random in time, I was left with the uncomfortable idea that the time of release, relative to a clock yet to be determined, establishes a random component of phase referenced to the clock, which I will call jitter. My discomfort comes from trying to relate jitter to the determination of where the electron, as particle, will land. But it seems plausible from the wave theory point of view, as if the jitter creates a sampling effect, that randomly picks a phase at which the reference clock will be interfered with. This would be analogous to two waves interfering at the far side of a dual slit which has a single wave source. The problem with this idea is that it requires a reference. What would be the cause of the reference? The wavelength associated with its energy? This also leads back to the inquiry about a possible spurious emitter.

At this point I was wanting to know the signal-to-noise ratio of the detector, and to see a block diagram, and where coupling with unwanted interference might occur, and EMI test results.

Finally I got to the last question in my mind, how does the apparatus work? It would appear that you start with a single negative charge at high velocity, which is fired toward a thin wire with gaps on each side bounded by plates. These elements are connected to a negative power supply, forming a repulsive barrier to the electron, leaving it to choose to go left or go right.

And this is where the apparatus is not operating perfectly. If it were perfect, it would be possible to reflect each and every electron back to the emitter with a thin wire.

Now, I asked myself, due to some miniscule noise component, the electron is forced to slide left or right. This delta in the transverse direction has some probability density as yet unknown. Assume it is uniform. What is the effect on the PDF of the trajectory, if the field around the wire is interacted by an electron with a miniscule uniformly random transverse component in its velocity vector? Because of the inverse square law of the field around the wire, in other words (ideally) the field is perfectly cylindrical about the wire, the expected interaction would be sinusoidal, thus a uniform density is warped into a sinusoidal density in this manner. But this does not explain the frequency (4 or 5 stripes) shown in the final screen. What is interesting is that wave interference allows for multiple stripes simply by changing the reference frequency mentioned above.

It would be interesting to hear what the folks at Hitachi think about their test apparatus and their results.
 
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I failed to mention in the preceding discussion that I was referring to the link given in post #4, which is:

electron double slit experiment


I might accept particle-wave duality as the explanation if someone could explain how the particle assumes a random phase and then chooses from among four or five fringe bands (in the reference) as it sets a course for the target.

Also: what is the particle's induced E-field doing, and where does it fit into the presumed wave behavior of the particle?
 
Maybe I can offer an analogy that might help. It isn't ideal, but it does relate to Maxwell's On Physical Lines of Force where the title is On the Theory of Molecular Vortices. Take a look at these pictures of a hurricane. Relate the eye of the storm to what you think of as the electron, and relate the surrounding vorticial winds to what you think of as its E-field. QM says a subatomic object is described by a wave function, so think of the electron wavefunction as being something like a spherical version of a hurricane. Now mentally grab hold of a "hurricane", and throw it at a wall of hurricanes where the eyes are arranged like this:

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You aren't throwing a point particle through a wall of point particles with a couple of slits in it. Each dot represents the centre of a particle, not a particle.
 
Farsight said:
Relate the eye of the storm to what you think of as the electron, and relate the surrounding vorticial winds to what you think of as its E-field. QM says a subatomic object is described by a wave function, so think of the electron wavefunction as being something like a spherical version of a hurricane.
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Except that you're mistaking the vector field associated to the electromagnetic field the electron interacts with with the electron field itself.

The wave function description of the electron passing through the double slit experiment has nothing to do with the electromagnetic field of the electron. Photons produce the same pattern and they don't interact with other photons in the electromagnetic field. Neutrons and even Bucky balls exhibit the same effect. The fields the particles couple to are not the same as the wave function of the fields.

Farsight said:
Now mentally grab hold of a "hurricane", and throw it at a wall of hurricanes where the eyes are arranged like this:

.........................................................
.........................................................
.........................................................
.........................................................
.........................................................
.........................................................


You aren't throwing a point particle through a wall of point particles with a couple of slits in it. Each dot represents the centre of a particle, not a particle.
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It's easy to draw pictures and use Google based analogies. But as I just demonstrated, they fall apart all too easily. Can you actually provide a quantitative model which has this interpretation and which works? Rather than constructing your idea via "Oh this looks like that!" can you construct it using clear and specific logic (yes, including mathematics) from base principles?

Remember, Maxwell was a mathematician, he was constructing his ideas in a formal manner. Only once you have the cold hard and perhaps non-user friendly formal description can you really start making analogies and simplifications with any degree of confidence.

Arguing by trying to generalise a simplified analogy is almost always going to end in failure. Unfortunately it seems to be the main method for 'armchair physicists' to work, as they (you) lack the ability to do the details.
 
I'm not mistaking the vector field associated to the electromagnetic field the electron interacts with with the electron field itself. I'm offering assistance. If you don't like it, you offer some assistance.
 
Farsight said:
You aren't throwing a point particle through a wall of point particles with a couple of slits in it. Each dot represents the centre of a particle, not a particle.
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Then what is being thrown at the target? The investigator says a particle, and gives it as a dot in his demonstration.
 
I think my statement is more directed at how the target works. Does it really intercept a particle? How does that work? Or is just measuring a voltage change by the arriving wavefront, not due to the quantum wave, but due to the impinging E-field.

I'm not disputing particle-wave duality. I'm questioning how the machine works and what the results really mean.
 
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