Danny ChaiI came across this really interesting article about quantum computers. I’m afraid this mymind won’t interest very many of you, because it involves both physics and philosophy. But it’s really interesting to me. The article involves the idea of the quantum computer. Here’s the thing; in quantum physics, things that are apart, maybe even far away, still seemed to be linked to each other in a weird way. It’s what the article refers to as entanglement.
Here’s an example. Let’s say you have a half-silvered mirror, so it lets half of all light through. OK, this will get a little weird, and I don’t fully understand it myself, but I will do my best from what I remember. A much better explanation can be found in the book The Emperor’s New Mind, by Roger Penrose. I highly recommend that book if you are into math, computer science, or physics, and philosophy. It’s a lot of philosophy and science. Not philosophy of science, which is different, but philosophy and science.
So as I was saying, you have this half silvered mirror. Now we all know light is both a particle and a wave. A photon is an elementary particle of light. Maybe that’s an inaccurate description, but that’s the idea. It’s like one unit of light. Ok, so what’s happens to the photon when you send it through that half silvered mirror?
One answer is, it’s a particle, so it either is reflected or not. That would be the wrong answer. The weird thing here is, the photon is in both places, but can only be described using like some wave equation or something bizarre. So like it’s in neither place. At least theoretically. OK, here’s where stuff gets weird and I might be explaining wrong. But as long as you don’t look at it, don’t observe it, it will behave like it’s in both places. But as soon as you look at it, or try to observe it, it’s in one or the other place. I think that’s how it goes. So there’s this experiment, where they make an opening so small that only one photon can get through at a time, and they do something like that, the half-silvered mirror thing. And they have detectors at the two places where the photon could go, either through or reflected at an angle. Anyway, when they do this, the detectors don’t like pick up some photons or others, but it’s like a smooth thing, like it’s constantly picking up some of it, as if each photon were going to both places. But as soon as they put some kind of detector, like on the opening or at the mirror to see where the photon goes, it starts going to one or the other. Weird stuff.
That whole observer thing in quantum physics is bizarre. If you can find out about it, look up the idea of Shroedinger’s cat. His idea was to make a quantum machine that would kill the cat only in some quantum event, but he supposed that there could be a situation where the cat is both dead and alive. Strange thought experiment.
So another idea is this, like you have the photon or maybe a group of photons I can’t remember, maybe it’s even a particle, but like the one sent through the half-silvered mirror, it’s two things going in different places but linked. What happens is, the spin of the things (all things have this quantum quality called spin) are not defined or anything, but as soon as you look at and record the spin of one of them, instantly the other spins in the other direction. I have not done justice to this idea, but that’s like the jist. I mean, it’s even more insane than I’ve described, but I don’t remember exactly how it works. And it’s not like they had opposite spin and you just found out when you detected, it’s that they weren’t defined or something like that, and as soon as you observe it, the other one gets opposite spin. It’s really nutty.
Oh wait, I think I remember it better. You can measure the spin in like whatever direction you want. What happens is when you measure the spin in a direction, the other one will get the exact opposite spin relative to the direction you measured it in. But it couldn’t have known ahead of time what relative direction you would choose. So it’s strange. Something like that. It’s as if they communicated over a large distance.
OK, so really interesting things come out of this. First, as Penrose talks about, it seems to violate the idea that things cannot move faster than light. Because these things could conceivably be light years away, and still, as soon as that observation happens, the other thing will instantly get that spin information. It’s like instantaneous communication over large distances.
The question then is whether this quantum phenomena could be used to our advantage. For example, what if we used like spin information to communicate over large distances instantaneously? Could that even be done? Or what if we had a quantum computer, a computer that harnessed that quantum phenomena? That would be the fastest computer ever, because the information is passed instantly. And that’s kind of the idea behind those quantum computers mentioned in the article. So it’s really exciting and interesting.
So what these scientists did was replicate the information of particles in one place to another place. So it’s like it didn’t really teleport, but because it had exactly the same quantum information, it was the same light beam in another place. And they imagine they could somehow do that with particles someday as well.
Essentially, it’s the idea in the movie the Fly, the remake, with Jeff Goldblum and Geena Davis. The guy in the movie didn’t actually move particles from one thing to another, but reconstructed it with the same information. So if you remember, early on it doesn’t work so well, and the steak tastes synthetic, but he gets it down in the end.
So if you’re a careful thinker, you realize that all this is based on the idea that if two things have the same quantum information, they’re the same thing. But that is disputable. So let’s think about it. We have one photon, with certain quantum information. Then we transfer that information (in a detructive process, as it turns out) to another photon. Is it the same photon? It’s a really interesting question. Because you want to say both yes and no. Yes because, I mean, how is it not the same photon, if it’s exactly the same in every respect except location? Especially since we’ve found that location is a tenuous thing. I mean. In what sense then are they different?
But in some intuitive sense, they must be different. I mean, it’s a different photon, it’s got to be different. And you just kind of feel, they’re exactly the same, yet in some way you can’t really explain, they must be different.
So the philophical question then is what makes things different. The easy answer is that if there is any difference between two things at all, then they’re different. But think about it, you are a different person than you were even 1 second ago. I mean, your physical makeup is different, cells have dies, cells have been made, you have different thoughts… But a person is too complex a case; I think I’ve talked about personal identity before, so let’s stick to something simple for now: Photons.
So what makes a photon the same photon? Like with a person, it can’t be being exactly the same, because photons, like people, change. They change spin, location, momentum, all this stuff. So what is it? Maybe what it is is some kind of physical continuity. Like, a photon might have been physically connected with the photon in the same place 1 millisecond ago, so it’s the same photon. Well, maybe there’s more to it; like in addition to being physically continuous, it’s got to have similar attributes. But maybe this isn’t enough. It’s debatable. So if you saw this photon sitting there, then all of a sudden, it totally changed properties, would you say it’s the same photon or not? I guess one could argue about it.
Ok, let’s go back to people. Is it really physical continuity that makes us the same person? I would think that most people think it’s not that but the way we’re put together that makes us the same. Think also that there are quantum effects going on in us all the time. So location is really not secure, with all our body parts, and there’s no guarantee that there’s any type of continuity. So it’s really the way we’re put together, down to the quantum level, that makes us the same, right?
But not really. I mean, most people, whether you recognize it or not, use a standard for being the same, and that is a continuity of memories. This is an idea first put forth by John Locke and it’s a good one. We’re the same because we have memories of stuff that happened to us before, real one, not made up ones, and that’s what makes us the same. That’s a pretty good standard, to me. Of course, there are problems with it. Like, how do we know what memories are real or not? What if we lose memories? And others. But if you fudge around with the definition, it’s still pretty good. And it matches how we think. When someone gets amnesia, we don’t really think it’s the same person, just the same body. If we were to imagine that someone’s brain was put in a machine body, we’d still think it’s the same person. In fact, forget the brain; if somehow the person’s mind was put into machine form, we’d still say it’s the same person. So that’s what it is.
I think if we really thought about it, we’d say that if a person were recreated in a different place put together exactly the same way, that they’d be the same person. Like in the Fly, he’s not really teleported, but we might as well say he was, since he’s the same person.
But then here’s the deal; what if that information could be recreated without destroying the original? It just happens that the process those scientists used destroyed the original, but does it have to be that way? What if the information could be copied without destroying the original? Then you have two things which are both the former thing. And that’s such a paradoxical situation. Can two things come from one? Can they both be that one? It’s just so strange. Did one continue to be the one, or was the one destroyed? How can two be one? It’s bizarre to think about. The scary thing is how close we are to thinking about stuff like that. Creepy.
And what if someone was “teleported.” Is he the same person? That’s really just a matter of opinion, I guess. There’s no way to say for sure. Whether being a copy with exactly the same setup and memories is enough to be the same person. But if it’s not, what is? Strange.
The point of the Fly is that we need to be careful when playing around with technology. It’s a good lesson to heed. I don’t know if you read this, but this guy is planning on cloning humans. It’s a scary world. Also, this scientist figured out how to grow fetuses that have no heads. You might think this is lame. But the idea behind it is to use the process to grow organs for transplants. Scary world we’re living in.
I’m tired. I just found out that since we students kept crashing the Ontolingua server, we got an extension until 6 PM tomorrow! Yippee!