Physics Blogging Round-Up: College Advice, Teleportation, Spin, and Bell Tests

I seem to be settling into a groove of doing about two posts a week at Forbes, which isn't quite enough to justify a weekly wrap-up, but works well bi-weekly. (I'm pretty sure that's the one that means "every two weeks" not "twice a week," but I always struggle with that one...) Over the last couple of weeks, I've hit a wide range of stuff:

-- Planning To Study Science In College? Here's Some Advice Pretty much what it says on the label. I saw a bunch of "advice to new students" posts, and said "Oh, I should do one of those..." so I did.

-- The Physics of Star Trek: Teleportation Versus Transporters: Somebody pointed out that Gene Roddenberry's birthday was last week, and Alex Knapp at Forbes is a big Trekkie, so he asked the science folks if we could write about Star Trek science. I had been thinking of writing about teleportation anyway, so this was an obvious choice.

-- How Quantum Symmetry Makes Solid Matter Possible: At the Schrödinger Sessions a few weeks back, Trey Porto of JQI gave a really nice explanation of quantum statistics that I said "I'm totally going to steal that." In the course of poking at ideas for a new book proposal, I ran across some mathematical physics papers showing that you need Pauli exclusion to explain the stability of solid matter, so I combined those here.

-- New Experiment Closes Quantum Loopholes, Confirms Spookiness: A new arxiv preprint is the first "loophole-free" test of Bell's inequality, which is something people have been working on for decades now. So I wrote up an explanation of what it means and how it works.

So, that's pretty much the full range of stuff I might write about over there: Two explainers, one with a pop-culture hook, one news story, and a thing about science education. Something about their system makes umpteen copies of the "photo gallery" for the old "Six Things Everyone Should Know About Quantum Physics" show up on my author page, making me look more insanely prolific than I really am, but that's a decent two weeks worth of stuff...

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I’m pretty sure that’s the one that means “every two weeks” not “twice a week,” but I always struggle with that one

You are correct. "Twice a week" would be semiweekly.

By Eric Lund (not verified) on 28 Aug 2015 #permalink

Pedant alert: According to the dictionaries I've checked in over the years, both meanings are correct - it's one that gets questioned all the time. That said, I've only ever actually seen the every two weeks usage.

I have a question about the Bell experiment paper, having finally read it. In the text they say QM predicts a value of 2*sqrt(2) from the experiment (about 2.8). If the result is robust enough to rule out local realism, doesn't it also rule out QM? Or to put it another way, if you try to compare hypotheses the measured value is almost exactly halfway between the two predicted values. It seems to me like the result is almost perfectly inconclusive. All they really said is they rejected the null, but which hypothesis you pick as the null seems arbitrary. Am I missing something?

QM allows any value up to two root two for that particular quantity. It varies depending on the exact angle of the polarizations they use. A local hidden variable theory can never exceed two.

Thus, anything over two can be said to exclude LHV models, but you can't exclude QM with anything less than 2.82... because the difference could be explained by experimental imperfections. To rule out QM, you would need to get a value of 3, or something like that.