When Einstein came up with relativity, we had to rethink time and space. I’m traveling in a boxcar and you’re standing beside the track; I turn on a light pointed straight ahead and we both measure the speed. The same! The speed of light.
The measured speed was the same, even though I’m traveling in the boxcar at a given speed, even though the earth is rushing around the sun at some huge speed, even though the galaxy is…etc. BUT, it is important to note, each of us just experienced time and space differently, even though we measured the same speed for light. So now let’s use this lightclock.
I’m far away in a spaceship moving at a tenth of the speed of light, and you’re on earth watching me go by. My light goes up and down very quickly, the speed of light over a few meters. To you though, the light would streak across the sky, traveling a great distance for each up and down pulse. In fact, many thousands of miles would be covered. This would take a much longer time for you…and only a fraction of a second would go by for me.
So in fact our speeds of light are the same, but TIME is different for us. So as I streak through space, you grow old. Thus the twin paradox:
Here is an amazing Queen song about love lost via time dilation. Brian May had a B.S. in both Physics and Math, and was working on a PhD in Astronomy when Queen blew up. He finished his PhD 30 years later in May 2008. SUP. The middle vocal belt-it-out in this clip is hilariously off, here’s the lyrics in case.
So this post is about entanglement not relativity, but I wanted to refresh the topic because the point here is very important: Once apon a time, relativity WRECKED our view of reality. But that sort of thing doesn’t usually happen immediately…it takes time to sink in. THAT IS PRECISELY THE SITUATION WITH QUANTUM THEORY TODAY (TIMES A MILLION). If you wrap your head around what is happening, you realize that we are in the midst of a great epistemological shakedown. We have not learned all of the lessons the quantum world is trying to teach us (read: never will if we’re reading it right). I feel that kids in 2060 will say: KID_A, “Hah, remember in 2036 when CERN invented time travel?” KID_B, “Yeah, crazy. Remember how they knew all the pieces in 2009 but just couldn’t solve the riddle?” We cannot fit entanglement into a world view born out of classical physics without major kicking and screaming. One time the world was flat, and one time lightning was an act of the gods…remember that time we didn’t know all the mysteries of entanglement? Wait, wait, what is entanglement?
Well, objects start behaving very strangely on the quantum scale. Physical properties of these objects, such as the position and momentum of a photon of light, are more accurately described in probabilities rather than definite values (and they’re complex probabilities like 30%+20%i). Nature unrelenting, the more you know about one property, the less you know about the others. So the more I know the exact position of this photon, the less I know about it’s momentum (see Heisenberg’s uncertainty principle).
The reason you know less about A when you try to learn more about B is because an object can only be seen to a precision of about the wavelength of the radiation used to observe it. You have to literally shoot a beam at a quantum object, and you have to decide how much juice to crank it up to. So if you want to learn the precise position of a photon, shoot a short wavelength at it and wait for it to bounce back. But, momemtum and energy correspond directly to wavelength, and, remember, you’re actually striking the object with this beam in order to measure it! So the instant you make your measurement you change the momentum, and in a short time, the position! So if you want to affect it less, use a wide, long wavelength beam, but then you will get a low resolution read of the position. Doh. Thus the uncertainty principle. It’s like a basketball being the smallest thing in the universe, it’s traveling way too fast, and you’re trying to measure its speed and direction by throwing another basketball at it and waiting for it to bounce back. Then imagine practicing it a lot and getting really damn good at it, and that’s about where we’re at.
In walks superposition. Is the photon/basketball spinning upwards or downwards (or sidewards-left or sidewards-right)? Well, both, and at the same time. A coin spinning in the air–is it heads or tails? Exactly. We don’t know, yet. It’s both outcomes. That’s why quantum computers are (potentially) so incredibly powerful. Instead of being normal bits represented by a 1 or a 0, quantum bits (stored on actual quantum objects) contain all possible values and configurations all at once. When you grab the spinning coin out of the air, it collapses from superposition into a “chosen” state. this is the same idea as in the uncertainty principal where you only get one chance to make a measurement. Once you interact with it you’re done, your chance has been used up.
What happens when photons of light go through a splitter like this calcite crystal? Some go one way, some go the other…and some go both ways. Whoops.
Or, sometimes with an excited atom, the atom will emit 2 photons at the same time instead of just one. These two will travel away from the atom in separate directions. In both of these cases you can’t fully describe the one without talking about the other. These are entangled.
When you make a measurement on one of the two, you instantly know the measurement on the other. Let’s say we have two entangled photons, Kasch and Clarke. I measure the spin of photon Kasch on the z-axis, and I find that it is spin-up, then I instantly know that Clarke is spin-down. BOOM. That’s it. Instant. It’s not that the information is available at the speed of light, it is instant. Scientists have sent streams of entangled photons down fiber optic tubes, had them travel 18km apart, then made the simultaneous measurements that confirmed this. In accounting for their experiments, they found that the decision for the second particle to collapse from superposition into its “chosen” state happened at AT LEAST 10,000 TIMES THE SPEED OF LIGHT. But, in fairness, instantly.
Sometimes they are called an EPR pair. This stands for Einstein-Podolsky-Rosen, the jokers that couldn’t stomach them. Quantum theory predicted the probabalistic behavior and this superluminal connection and Einstein hated it. He called it “spooky action at a distance” and stood firm that “God does not play dice.” The EPR paradox (1935) essentially explained it away by saying there were hidden variables at work. Even though the particles are in superposition before the measurement, they “know” what they really are. One is heads, one is tails. Once you coax them they admit it.
There is a problem here, either the entangled pair communicate instantly with each other upon measurement, or they always had a chosen state. When I measure the spin over the x-axis on one of our entangled pair, I successfully predict the spin on the x-axis of the other. But now I’ve disturbed the entangled state through measuring, and I can’t go back and measure the spin on, say, the z-axis, and have that be predicitive. But I can measure whatever axis I want the first time and it works. Extremely well. It’s 100% predictive. John S. Bell decided to play with the numbers. He cleverly developed a real experiment (taking it from metaphysics to physics) where he analyzed the spin from various 45 degree angles off of a particular axis. Classical statistics dictated that the results should behave one way if there were predetermined local hidden variables. But they didn’t. Instead of being correllated 50% of the time (which would have seemed obvious), the alternate angles matched 71%, as predicted by quantum mechanics. Bell showed that the particles were actually talking to each other (instantly), changing direction in response to the other’s measurement. The math behind this is tricky, but please have a go at it.
Bell’s experiments have been reproduced a ton of new ways, one of the newer being the 18km test mentioned above. These experiments overwhelmingly support nonlocality over the idea of hidden variables. Here is the basic original setup:
In fairness there are still a couple of objections to these experiments, the detection loophole and the communication loophole. But overall, there have been a slew of experiements in the past few decades that have backed the predicted behaviors of quantum theory against all intuition. The two times the results favored hidden variables, the results could not be recreated.
QUANTUM CRYPTOGRAPHY AND QUANTUM COMPUTING
So, entanglement is real and with us. What can be done with it? So far it doesn’t necessarily violate special relativity (which more accurately puts a cap on the speed of information, not light). Just because you measure and thus predict the spin of a photon doesn’t mean you can encode a message across the instant divide. You can, however, use it for completely unbreakable encryption.
If you analyze a stream of photons, (the picture helps visualize the stream) and you and your sender know which ones to look for, and what orientations, you can use it as a key. If a thief tried to tap the fiber optic line, her analysis of the stream would, as we know, alter it and the code would no longer be valid. Keep in mind, this is just the key, not the information itself. In 2004 the central bank of Vienna, Austria successfully completed the first quantum encrypted bank transfer using entanglement. Currently there are four companies (e.g.) worldwide who offer quantum cryptographic installations. I just called one to get pricing but I got the sales guy’s voicemail.
So remember we’re just passing a key. Right now it is easy to make an encryption algorithm too complex for ordinary supercomputers to break. Basically multiply a bunch of prime numbers together until you get a huge number, that’s your key. This is because factoring numbers is orders more difficult than multiplying them.
BUT, if we had better quantum computers, they could factor primes much, much faster, making this quantum cryptography not so amazing after all. Wiki gave the example of 300-digit prime numbers. Multiply a few of them together to form a badass encryption key, and an ordinary computer would compute for years(?) before figuring it out. Quantum computers can quickly arrive at the solution. So basically, the first person/government/corporation to develop a functionally robust quantum computer gets the password to everything.
The current problem but also the glory of quantum computing is that it fuses information with the physical world. The information is no longer a simple bit–an electrical pulse in circuitry, or a symbolic impression on a CD/DVD–it is a base physical object, the probabilities of orientation of a particle in superpostion. It is the machine code of the universe. The language of god.
Enough about computers, here is the reason this is interesting, the reason why you’ve read this far…time travel! Yessh. I read this in a book (The God Effect), but then I let someone borrow it, so I can’t look back for the full details…so here are the basics. Let’s suppose you can find a way to send a message across a stream of entangled pairs. If that is possible, then all you have to do is shoot the stream into some super dense near zero Kelvin liquidish goo (I think it’s possible, I don’t remember what it is though), which slows down a beam of light to ~1cm/sec. Basically you need a way to store entangled particles. Hopefully there’s a better way than this. Now, one person takes the briefcase full of half of the entangled pair into space, and travels away from the earth at high speeds. Years later, (several decades later on Earth as we know it), they make their measurements…send the message. However that works. The point is, if there is a way to encode a message across entangled particles, it means it is logically possible to send a message instantly across some time divide caused by time dilation. The praciticalities of making it happen are near impossible, but if it is rationally possible, that plays with the idea of causality quite a bit, and then we will be forced to live with John Titor’s reality. Let me know if you borrowed my book.
So here is what I suppose is happening. This next idea has no testing, research or math behind it, but it seems pretty intuitive to me. When entangled particles part ways, they do so in our simple 4 dimensions of spacetime, but they travel together in a 5th or 6th or 7th unseen folded spatial dimension. They dash along this straight line together until you disturb them, at which point their bond in that dimension is broken. That’s that.