Bounding the speed of ‘spooky action at a distance’

So what they actually measured is something that appears to go faster than light in the reference frame of measurement. This does <i>not</i> mean they measured the actual speed of the interaction. Instead, the point of this experiment is to lose a loophole in Bell test experiments: simply put, Bell experiments had previously proven that this seemingly-"non local" (bear with me) state exists and preserves dntanglement over long distances. The loophole was that it previously wasn't possible to time the ecperiment well enough to make sure that the whole thing didn't occur in some unexpected, <i>subluminal</i> way. Now we know it couldn't have occurred by some sort of classical interaction between the entangled qubits.<p>So how fast is the interaction, really? Well, it turns out that if something moves even 0.0001% faster than light, we can always find a reference frame in which it moves a million times faster than light, or infinitely fast, or even in which it appears to move at some huge negative velocity: back in time. See "tachyonic antitelephone". In other words, once something is faster than light, it is, essentially, instantaneous. This is in accordance with standard predictions of quantum mechanics.<p>Source: I'm a physics grad student.

Suppose you and a distant friend both agree to wave a flag at 1200 GST.<p>To an alien observing Earth, it looks as if the "human flag-raising interaction" is an instant effect that "travels" faster than the speed of light, since the flag raising happens at the same time in two places.<p>But really, nothing is travelling. You and your friend just pre-agreed to do something at the same time at different places.<p>If energy or information is not transmitted, then what is? I'd argue nothing.<p>(-A physicist)

Everyone here is getting confused by the fact that you cannot control the polarity/polarization of the qubits before/as you send them.<p>This means that one <i></i>cannot<i></i> send information faster than light.<p>What is useful however is the fact that when you send entangled qubits very far away, and measure them is the fact that the results of the measurements are always correlated/anti-correlated.<p>As an example.<p>Alice has a pair of entangled qubits, they are in a superposition of 1 and 0 (lets say they are an correlated pair, such that when measured both quibits will always agree).<p>She sends one to Bob.<p>Bob and Alice now hold one qubit each out of the entangled pair. They both measure their qubits. The measurement is probabilistic, you have a 50/50 chance of getting a 1 or a 0, but Bobs quibits and Alices quibit will agree everytime.<p>Since you can't control the outcome of the experiment you cannot decide which bit to send and hence cannot send information.<p>The useful result is that Alice and Bob have a string of bits which <i></i>only the two of them<i></i> know the arrangement of. They can use the string of bits as a one-time pad for encryption.<p>I have simplified this immensely but I think the point gets across.<p>Source : I currently undertake research into generating qubits for quantum computation and communication purposes.

It's like you and a friend have a deck of cards.<p>You each take a card from the deck, and then travel a million miles away.<p>Then, at the crack of noon (synchronized to GST, of course), you both look at your cards. Your card is the 3 of Clubs.<p>You travel back to meet your friend, and discover that his card (which he measured at noon, just like you) was the 7 of Diamonds.<p>You repeat this experiment a gazillion times and are amazed!! No matter how many times you run it, you and your friend never get the same card!!!<p>It's as if the cards are sending spooky signals to each other!<p>And after you double check that you and your friend are both looking only at 1200 GST, you realize that this spooky signal travels faster than the speed of light (since the it takes no time to "travel" a million miles).<p>It's like magic, eh?<p>Not really. The fact there is one of each card means it's impossible for you and your friend to have the same card. No magical spooky signals are being sent.<p>(The real question is whether the quantum mechanical case is analogous to this contrived example. I think it is. The important difference in quantum mechanics it that you really don't know what card you have until you look at it. However, that doesn't mean that your card is sending a faster-than-light spooky signal to tell the other card what to be. And you certainly can't use it for signalling or anything useful.)

Physics works as we already thought it did. Move along, folks. Nothing to see here. :)

This is ignorant speculation, but what if the interaction doesn't depend on distance, and instead always takes the same fixed amount of time? What if that delta t is equal to 1 plank time, one tick in the cosmic 3D simulation? Of course that's an advanced experiment to run, but the implications would be fun.

Watch out for arxiv.org, these papers may or may not have passed peer review. A lot of junk is deposited there.

I sent this to my friend who has a phd in physics and is a post-doc at Cambridge and he said it's bogus.

This would be helpful for intergalactic domination. Kidding.