Posted on 10/23/2001 5:15:41 PM PDT by Starmaker
A few weeks ago we just got one big step closer to having quantum computers and teleportation. This is because atoms have an almost ‘psychic´ ability that Einstein once termed spooky. It seems that distant atoms are almost ‘telepathically´ linked to each other in what scientists call entanglement. Plainly put, it means that a group of atoms ‘over here´ knows what a group of atoms ‘over there´ are doing. This is one of the properties of atoms described by of a branch of science called Quantum Theory.
The word ‘quantum´ means a discrete or separate unit of energy, and Quantum Theory tries to explain the properties of these basic units of nature. When people think of atoms, they usually envision solid, separate balls of matter like a group of billiard balls. However, according to Quantum Theory, atoms are much less tangible, with properties that can only be described (right now) as spooky.
One of the first weird things we learned about quantum particles was that we could know where a particle was, or when a particle was, but we could never know both at the same time. Because it reminds me of the socks I always lose in the wash, I call it "Beth´s Principle of Lost Socks and Quantum Particles." (I would know when I had a full pair of socks, or where that full pair had been, but do the laundry and the full pair would be gone.) In fancy terms, we´d say we knew a particle´s location or it´s velocity, but not both. This discovery is called the Heisenberg Uncertainty Principle, and understanding it is critical to understanding the possibilities inherent in Quantum Theory.
Quantum particles such as atoms or photons can exist in distinct states, like the head or tail of a coin. But these same particles can also exist in both states at once (known formally as superposition). This is comparable to a coin spinning in the air before it lands.
Now let´s suppose we toss two coins at once. Whichever way one coin lands has no bearing on how the other coin lands. Because of this, we say their outcomes are independent -- if one coin lands heads up, it will not effect the way the other coin lands. However, two entangled quantum particles are not like coins. The fate of one effects the fate of the other. For instance, if one entangled quantum particle is in a 'heads' state, the other must be in a 'tails' state. We say that they are interdependent. And this interdependence is the whole key to teleportation.
For any practical applications, entanglement has to embrace thousands, or even millions, of particles, and maintaining total entanglement is very difficult. However, the scientists have found a way around this problem.
They do without complete entanglement, where the state of each particle depends on the state of every other particle. Instead, they generate two loosely entangled clouds of cesium gas, one with slightly more atoms in a 'heads' state and the other with slightly more in a 'tails' state. (These two states are actually defined by the directions of the atoms' magnetic fields.) By doing it this way, many more atoms can be entangled, and stay that way for a longer period of time.
So how does this translate into teleportation? Well, it does and it doesn´t. But the final effect is the same as teleportation. One set of quantum particles can be instantaneously reproduced somewhere else. So unlike Star Trek, objects are not broken down and their particles ‘beamed´ somewhere. Instead, they are reproduced somewhere. In this way a message encoded in photons of light could be transmitted from one place to another without sending the photons across the intervening space, effectively bypassing the speed-of-light barrier.
Up until now, the maximum amount of particles that scientists could entangle were a measly four atoms. This most recent experiment entangled about a million atoms, bringing us much closer to the realization of teleportation, quantum computers, and a new form of instant communication over vast distances.
Reminds me of the street where I grew up.
It is cool and spooky at the same time.
Could this explain the current geopolitical status???
Dubya (heads-up)good affects Osama bin Laden heads (heads-down)bad????
Quantum Physics of Politics?
NeverGore
The effect can't be used to transmit information through the actual entanglement, but the particles can be shared between two locations, then the information of one of them can be measured and transmitted at normal speeds to the other location, where they will discover that their particle has a corresponding (usually opposite) measurement. It's a bit like destructive testing though - you can't find out anything about the particles without breaking the entanglement - thus no info can be transmitted at faster than light speed. I seem to remember that this effect has some obscure use for checking if a fibre optic cable is being eavesdropped upon etc, (oops - as mentioned in the article). I think the coin toss metaphor is one of the better ways I’ve heard of explaining this effect so far.
One set of quantum particles can be instantaneously reproduced somewhere else. So unlike Star Trek, objects are not broken down and their particles ‘beamed´ somewhere. Instead, they are reproduced somewhere.
So, instead of sending the original particles somewhere else, a copy of these particles are "assembled" at the new location — But, from what? Wouldn't some form of particles already have to be present at the new location in order to serve as the "raw material" for the reproduction, or are we literally making particles out of nothing?
To the best of my understanding, that's simply not the case--and if it were the case, a number of paradoxes could be created, such as "sending information into the past" and other such paradoxes in simultaneity.
Of course, every few months one encounters another "scientists break the speed of light barrier" story in the press, but then again, you also find the occasional "perpetual motion machine invented" headline as well. I've never placed stock in such articles. I am trying to figure out, is this such an article?
There's alot of things I don't know, but I do know some quantum physics, and what the author of the article saying is indeed true. Einstein was right to call it spooky, because it is.
Take an entangled pair, break it apart and drag one way over to the other side of the universe. You can alter the state of one particle and *instantly*, the other particle will reverse it's state as well. Creepy? Yeah. Of course, there's the question of how practical it is. I mentioned this very same principle to some friends probably 10 years ago and they thought I was full of it. Glad to know that word is getting out.
Personally, quantum physics bothers me in many ways because it seems to, in some ways, contradict certain laws. Such as, quantum mechanics allows for something to be in two places at once. Urgh. And faster than light "information" flow. Urgh.
At any rate, "traditional" physics has it's inviolate laws, and quantum theory does in fact encompass them, but models things in a different way. Spend a couple years studying it and maybe it'll make sense... Lord knows it doesn't make absolute sense to me either, but at least I apprehend it, even if I don't comprehend it.
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