Entanglement Done Right

I finally found post about quantum entanglement that does a great job of explaining entanglement, in the context of an attempt to entangle macroscopic objects: Spooky Mirror Tricks. As far as I have seen, it contains none of the “wall of shame statements” I ranted about recently. Quite the opposite.

[Entanglement] allows two particles to form a quantum object even when they are far apart.

[I]f one measures, on one particle, the quantum property through which that particle is entangled with other particles, the same property will promptly be determined for each of the particles involved.

[E]ntangled quantum particles behave similarly: there seems to be a strange connection between them. However, even this image is misleading, as there are no physical forces in play. In addition, only certain properties are ever entangled. For light quanta, for instance, this can be what is known as polarization, which can be imagined as a small pointer.If two entangled photons are prepared in a certain way, then the polarizations of both photons must point in exactly the same direction.

Now, although the two photons must obey this strict “principle of conservation,” the quantum world does not dictate the direction in which the polarizations must point in relation to their surroundings. This is a further quirk of the entangled quantum world: as long as a property isn’t measured, it isn’t fixed for the object being observed. Only when someone measures the polarization of one of the two photons does he give it a direction relative to its surroundings. The polarization of the other photon must then immediately point in the same direction, no matter how far away it is.

Voilà! It can be done! Hear ye, hear ye. Let the journalism world know that you can explain entanglement properly, without mentioning Star Trek at all.

The Tipping Point

There’s a neat effect just after the 2:00 point of this video: the pilot does a barrel-roll, and the beverage in his cup does not spill. Then, he pours iced tea into his cup while doing the maneuver. The beverage in the cup remains pretty much parallel to the support the whole time.

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The physics here is the same as with a swinging bucket; one must realize that the plane isn’t simply rotating along its axis — it’s following a circular path, and there is always lift (i.e. a force) going from the bottom of the plane to the top. I recreated this (to an extent) with a clear container and some Romulan Ale (I only use it for medicinal purposes). The first frame is where I was holding the bottle, so it’s at rest. The liquid is clearly at an angle to the container, and is parallel with the floor.

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And the second is while the bottle is a freely swinging pendulum, and you can see the liquid is now level with the bottom of the container.

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Blah, blah, blah. Oh, balls. I was working on this a while ago and now find that Rhett has a post up about it, though not following the same path I was going to take. Pouring tea in a plane – upside down, where he’s worked out all of the physics, with diagrams and pictures with circles and arrows and a paragraph under each one explaining what it is. So I’ve abandoned my v/2 (half-fast) explanation in favor of a link to his.