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Asked by byronlogan12345 to Claire, Kate, Matt, Rob, Sam on 20 Jun 2013.
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Robert Woolfson answered on 20 Jun 2013:
Quantum states are very complicated as they have so many different aspects. This makes it generally impossible to copy them once they’ve been made. To the best of my knowledge, the only way to copy quantum states is to make two copies when you first make it.
There’s a whole branch of research called quantum communication that is based on the fact you can’t clone quantum states, have a look at this link for a bit more information.
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Claire Lee answered on 20 Jun 2013:
Do you have a little brother? Let’s pretend you do (or if you do, even better) and he’s standing in front of you.
To see your brother, light is bouncing off him and going into your eye which sends a signal to your brain, telling you where he was. Now, your brother is pretty big compared to particles of light, so he is not really affected by the light hitting him, and so he’s still standing there.
However, imagine that instead of using light, you want to observe your brother by using a bowling ball (DO NOT TRY THIS AT HOME). You blindfold yourself (to make this more interesting) and throw the ball at your brother and it would bounce back to you, and you could get an idea of where he he was. But this time after the bowling ball hits him, because it’s about the same size as he is, he wouldn’t be standing in the same place after you made your measurement! (He could be flat on the floor, or running towards you in rage, and you wouldn’t have a single clue where he could be! – you’re blindfolded, remember!)
This is the problem in the quantum world. The particles that you observe something with are about the same size as the things you are trying to observe, so any time you make a measurement, you change the original in some unknown way! So then the clone is not really a clone.
Also, I *think* the idea of quantum cloning is that you want to clone an unknown state. But if it’s unknown, you don’t know what to clone, so you need to make a measurement, but then you change it and it’s unknown again and…. aaaaAAAAHHHH!
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Sam Geen answered on 20 Jun 2013:
It’s not impossible, it’s just very very difficult. People have cloned single particles before, but entire people is a little more difficult, considering a person has, what, a hundred thousand trillion trillion particles in them? Maybe one day. But right now you need a different alibi to prove it wasn’t you that stole those sweets. Sorry!
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