I've heard of two ways to interpret the concept of "superposition": 1) particles existing in more than one place at a time, and 2) particles existing in more than one universe at a time.

 

Is there any scientific reason to choose one interpretation over the other, or is this just a matter of philosophical speculation?

it explains the behavior of single photons in De Young double slit experiment, but that's more fitting an explanation to an observation. There is no empirical evidence.

They're just nice ways of thinking about it. I've always been taught the first one, so tend to think that way.

it explains the behavior of single photons in De Young double slit experiment, but that's more fitting an explanation to an observation. There is no empirical evidence.

 

Is the 'De Young' experiment any different from the ones I've heard of? The ones I've heard involve single electrons (or photons) being fired at a double slitted wall and observing the interference pattern building up after a while.

It was originally done with a stream of particles I believe. But fundamentally no.

 

http://en.wikipedia.org/wiki/Double-slit_experiment

I've heard of two ways to interpret the concept of "superposition": 1) particles existing in more than one place at a time, and 2) particles existing in more than one universe at a time.

 

Is there any scientific reason to choose one interpretation over the other, or is this just a matter of philosophical speculation?

 

The superposition can also be more generically interpreted as that our information is a weighted sum of our options, in which case it seems almost obvious, if you take the view that the wavefunction represents the observers information about the system described. But in the case of transformed or entangled information, the options in the sum, need not be individually "physical" or "classical". (Whatver that means, I don't like that word:) - just as a reminder that in QM, also classically forbidden paths are summed.

 

Often "the superposition principle" also refers to the fact that a linear combination of solutions to the QM equations, is also a solution, simply because the equation itself is linear.

 

/Fredrik