Can an Electron be in Two Places at the Same Time?

Max Planck Society ^ | 11 October 2005 | Staff

[Physicist]

People tend to try to read too much philosophy into the science of quantum mechanics. Wave-particle duality means just what it says; no explicit or implicit statements about "independent reality" lie within it.

Oh, there's plenty of philosophical red meat in quantum physics; it's just that most people get the philosophy wrong. Reality is weird, nonlocal, superposed, indeterminate, random, and even retroactive, but in the final analysis, everyone's measurements of this reality will agree.

[Netheron]

Actually, there is only one electron field. Individual electrons are merely excited states of it.

[PatrickHenry]

... and even retroactive ...

Better watch out. Your grandchildren might decided to wipe you out in your childhood as part of a lab in time travel. It could happen to any of us at any --

[Doctor Stochastic]

. So, depending on how the experiment is carried out, the electron is either at position A, position B, or at both at the same time.

I don't like the phrasing much. These are two different experiments with differing setups. There's no a priori reason to expect the same result.

[Doctor Stochastic]

Yep. Electrons are electrons. We assign the concept "wave" or "particle" as is convenient.

[Doctor Stochastic]

It's also a big leap to realize that wave functions are additive, not probabilities. QM probability lies not on a Boolean algebra but on a lattice. Also there are no marginals.

[LogicWings]

quantum physics has simply come to accept as a given over the years that there does not seem to be an independent reality

This statement bothered me too and was totally contradicted by the conclusion the article was trying to prove:

. . . have shown for the first time that electrons have characteristics of both waves and particles at the same time . . .

The state isn't determined by the observer, observing doesn't change anything. Both states exist at the same time and it has proved, up until this point, impossible to observe that fact.

This experiment, if it bears out, proves that there is an independent, objective reality and elementary particles exist in both states at the same time.

Only thing left to do is coin a new term to define this state, like "time-space-continuum" did for whatever this nuthouse is we exist in.

[js1138]

Passing a stream of electrons through a pair of closely spaced slits and seeing an interference pattern similar to light would not be surprising as within that stream each electron would have some small effect on any other electrons near it, possibly pushing them to the side enough to go through the 2nd slit. All of this I have had to deal with in color CRT (picture tubes) construction.

But what if the interference pattern appears when you use one electron or photon at a time?

which is how the experiment is done.

[js1138]

http://www.colorado.edu/physics/2000/schroedinger/two-slit3.html

[Doctor Stochastic]

"Wave-Particle Duality" is more a description of measurements than of objects. (At least that's what I think today.)

[js1138]

Whatever it is, it makes a lot of experience based intuitive thinking obsolete.

[RightWingAtheist]

When they talk about the electron double-slit experiment, do they mean GP Thomson and Davisson's experiments? One of my favorite ironies is that nearly a half century after JJ Thomson proved both the electron was a particle, his own son showed that it was also a wave.

[Doctor Stochastic]

Good intuition comes from experience.
Experience comes from misusing intuition.

[PatrickHenry]

When they talk about the electron double-slit experiment, do they mean GP Thomson and Davisson's experiments?

I'm not sure. Maybe someone who knows will chime in.

[phantomworker]

It's also a big leap to realize that wave functions are additive, not probabilities. QM probability lies not on a Boolean algebra but on a lattice. Also there are no marginals.

Brings back memories... The lattice of wave functions would be Lebesque integrals. How about fuzzy set theory for marginals?

[chaosagent]

Bookmark for later.

[phantomworker]

http://www.spacedaily.com/news/physics-05zk.html

Check out this quantum computer using quantum bits. They were talking about teleporting.

That is one way electrons could be in two places at the same time...

[grey_whiskers]

Wave-particle duality means just what it says; no explicit or implicit statements about "independent reality" lie within it.

The reason they tend to think that is due to the Heisenberg uncertainty principle.

Anything you do to measure the system will interact with it. When you get down to atomic scales, your measurement will perturb the system from its original state and information about the system "as it was" gets lost.

Just remember. Schroedinger saved a fortune on kitty litter.

Cheers!

[Quark2005]

Anything you do to measure the system will interact with it. When you get down to atomic scales, your measurement will perturb the system from its original state and information about the system "as it was" gets lost.

Strange stuff indeed. I've been in grad school studying the stuff for a few years now - I've gotten better at doing the math behind it, but the more I learn about quantum physics the more I realize that my knowledge of it is insignificant in the grand scheme of things, and I can't say my philosophical understanding of it is any better than it was before I starting studying it. Even the simplest results in QM are very difficult to understand thoroughly.

I do wonder what the crazies at PETA would think of Schroedinger and his dead cat if he had done his thought experiment in this day and age.

[Wurlitzer]

"But what if the interference pattern appears when you use one electron or photon at a time? which is how the experiment is done. "

That would an atomic particle of a different color. I did not pick up that it was a single electron. Thanks for pointing that out.

I would still need to know how many electrons were measured at the target site. If a single electron is always received yet an interference pattern exists then it is out of my league. However, two or more electrons hitting the target when only one was sent can be explained depending upon the voltage potentials at the emitter, mask with the slit and the target.