Open thread, Dec. 22 - Dec. 28, 2014

Gondolinian

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

Notes for future OT posters:

1. Please add the 'open_thread' tag.

2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)

3. Open Threads should be posted in Discussion, and not Main.

4. Open Threads should start on Monday, and end on Sunday.

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

Previous Open Thread

Notes for future OT posters:

1. Please add the 'open_thread' tag.

2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)

3. Open Threads should be posted in Discussion, and not Main.

4. Open Threads should start on Monday, and end on Sunday.

Does this mean something? http://phys.org/news/2014-12-quantum-physics-complicated.html

They found that 'wave-particle duality' is simply the quantum 'uncertainty principle' in disguise, reducing two mysteries to one.

That seems like the kind of thing that sounds cool to say but doesn't represent anything new, except that it's being widely reported (Google news search) as a spanking-new revolution in QM, which is evidence for it being at least slightly significant. Can anyone who understands what's going on (or knows someone that does) tell me whether this is anything significantly new?

Edit: looks like the HN people aren't too impressed either. https://news.ycombinator.com/item?id=8772422

Imagine you build a computer model, and it has an ontology. Ontolgy 1.

This computer model simulates the behavior or particles. These particles and their interactions form another computer. A computer inside a computer simulation. The internal computer has its own ontology. Ontology 2. The internal computer performs measurements of its world.

Basically, the idea is that Ontology 2 is what the computer model knows about itself. And that the uncertainty principle applies to our measurements, which in the model are represented by Onotology 2.

That means Ontology... (read more)

10passive_fist11y

It's just an example of lousy reporting. But first, some background. Whether a 'particle' or 'wave' approximation is more accurate depends on energy density. When the density of energy is relatively low compared to the energy of the photons (such as gamma rays coming off from a sample of radioactive material), the particle approximation is far more appropriate. When the energy density is high relative to the energy of the photons (like in a microwave oven), the wave approximation fits better. This is what was traditionally meant by 'wave-particle duality'. This idea is indeed connected with the fact that the more localized a wavefunction is, the more spread is spectrum of momenta is (uncertainty principle). This is widely known and is nothing new. What they've done in this paper - which despite the lazy reporting of the paper is actually a thought-provoking bit of work - is consider 'wavefunction collapse', which is just the process of entanglement of the 'observer' wavefunction with the 'experiment' wavefunction. They've essentially shown that the amount of information that can flow from the 'experiment' to the 'observer' when the wavefunctions become entangled has an entropic bound. This idea has been thrown about for years; here they claim to have finally found a satisfying proof.

2jsteinhardt11y

I'm not a physicist but I think it's been well-known for a while that wave-particle duality arises from the uncertainty principle.