- Oct 9, 2005
- 168
Please explain
- Thread starter Titch
- Start date
Titch said:
Well, headache here too, been reading it this morning and uhhhh.
And I studied physics, but this
I've been reading some of the background articles about Grover's algorithm, which is implemented in this computer and about counterfactual computations (which is what makes it work) and all I can say is I can read and understand the formulas and it's all great, but there's no way I can explain it. Grover's algorithm (written down in 1996 i believe) and counterfactual computations (something from 5 years ago or so) are both based on the basic principle of quantum mechanics (for which I had an 8 out of 10 score at university, but that's not helping a lot here :cry: ) dating from 1926 or so (you might have heard of it, it's called Heisenberg's uncertainty principle, something which made Einstein say 'God doesn't play dice' or so, guess even he can be wrong).
That computer is even weirder than it seems at first glance. You'll get the right answer if you have it -not- compute the answer (so the algorithm isn't executed, but you do get the answer to the question). If it executes the algorithm, the answer will be wrong
At least the guys who came up with this computer say it's weird too.
Sandre
For mathematicians and computational science people among us:
fastest normal search algorithm in an unordered list executed on a non quantum computer is of the order O(N).
Grover's algorithm on this quantumcomputer searches an unordered list in O(N^1/2). So you could say it defies normal mathematical possibilities
Nice question though: does that matter at all, since you don't even need to execute the algorithm? Guess I'll be getting another headache now
Ayu said:
Almost. The issue with 42 is not knowing the question.
In this case you know the question and get the answer without executing the algorithm that computes the answer
42 is mentioned a lot in threads on this topic on different forums though
I dropped QM from my chemistry classes because of this and did laserspectroscopy PhD instead, but the basic principle of uncertainty (non-)measurement in QM is very similar to determining the life/death of Schroedingers cat experiment. Bear with me for i am just a physical-chemist, not hardcore like Sandre 
Put a cat in a light and soundsealed box, place a contraption with cyanide gas inside, which is triggered by a photon, and place in front of the contraption a 50% transparent mirror, shoot a photon at it and start discussing if the cat is alive or dead.
Naturally the photon will either reflect (cat ia alive) or pass through (cat is dead). But the trick is that it is NOT not known if the cat is alive or dead, but that it cannot be determined, because you sealed the box.
The cat is now in a 50% dead 50% alive situation, according to QM theory. Exactly this "superposition" is crucial with respect to the quantum experiments based on solving algorithms.
When running such an experiment, all solutions of the algorithm appear quickly and on top of eachother (wavefunction superposition), and when you keep the box closed, like in Schroedingers cat, all possible outcomes of the algorithm are intact.
As soon as you open the box and start measuring, the solutions collapse into only one state, the "solution" you just measured, and you've ruined the algorithm calculation.
So the trick is to "read" the solution without looking into the box. I think this has been achieved by Kwiat. How exactly he did it, i don't know, because the counterfactual experiment baffles me. By not running it, so not letting the photons do their work, he found the solution?
I would rather see something like, by not running through MC you complete MC? I have hopes for my Pally
Put a cat in a light and soundsealed box, place a contraption with cyanide gas inside, which is triggered by a photon, and place in front of the contraption a 50% transparent mirror, shoot a photon at it and start discussing if the cat is alive or dead.
Naturally the photon will either reflect (cat ia alive) or pass through (cat is dead). But the trick is that it is NOT not known if the cat is alive or dead, but that it cannot be determined, because you sealed the box.
The cat is now in a 50% dead 50% alive situation, according to QM theory. Exactly this "superposition" is crucial with respect to the quantum experiments based on solving algorithms.
When running such an experiment, all solutions of the algorithm appear quickly and on top of eachother (wavefunction superposition), and when you keep the box closed, like in Schroedingers cat, all possible outcomes of the algorithm are intact.
As soon as you open the box and start measuring, the solutions collapse into only one state, the "solution" you just measured, and you've ruined the algorithm calculation.
So the trick is to "read" the solution without looking into the box. I think this has been achieved by Kwiat. How exactly he did it, i don't know, because the counterfactual experiment baffles me. By not running it, so not letting the photons do their work, he found the solution?
I would rather see something like, by not running through MC you complete MC? I have hopes for my Pally
Galatea said:just to scare you even more Lia, even *I* passed A lvl physics.... (ok so its not much, but it might scare you nonetheless
*runs away*
I don't know anything about physics, scary stuff :cry:
Archeology and ancient Latin/Greek studies ftw :|
Liandra said:Galatea said:just to scare you even more Lia, even *I* passed A lvl physics.... (ok so its not much, but it might scare you nonetheless
*runs away*
I don't know anything about physics, scary stuff :cry:
Archeology and ancient Latin/Greek studies ftw :|
Pff, I can tell you you handle the physical stuff perfectly
arty:
- Aug 26, 2005
- 15,256
Johras said:Liandra said:Galatea said:just to scare you even more Lia, even *I* passed A lvl physics.... (ok so its not much, but it might scare you nonetheless
*runs away*
I don't know anything about physics, scary stuff :cry:
Archeology and ancient Latin/Greek studies ftw :|
Pff, I can tell you you handle the physical stuff perfectly
And Gala knows how to do it with the best aerodynamics
0.5*m*v
I have been reading this thread...now I liked the kitty thingy but could someone please tell me what I have been reading?
/me casts Greater Blessing of Salvation on StuvvieStuvvie said:I have been reading this thread...now I liked the kitty thingy but could someone please tell me what I have been reading?
Your first steps into Quantum Mechanics!
http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat has some interesting stuff about this thought experiment. BTW they use a radioactive decaying nucleus, instead of the photon interacting by a semitransparent mirror. Woteva
Vegana said:/me casts Greater Blessing of Salvation on StuvvieStuvvie said:I have been reading this thread...now I liked the kitty thingy but could someone please tell me what I have been reading?
Your first steps into Quantum Mechanics!
http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat has some interesting stuff about this thought experiment. BTW they use a radioactive decaying nucleus, instead of the photon interacting by a semitransparent mirror. Woteva
Owwww shit, so when do I turn the homework in?
OP
- Oct 9, 2005
- 168
Stuvvie said:Vegana said:/me casts Greater Blessing of Salvation on StuvvieStuvvie said:I have been reading this thread...now I liked the kitty thingy but could someone please tell me what I have been reading?
Your first steps into Quantum Mechanics!
http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat has some interesting stuff about this thought experiment. BTW they use a radioactive decaying nucleus, instead of the photon interacting by a semitransparent mirror. Woteva
Owwww shit, so when do I turn the homework in?
The cool thing is, you can turn the homework in, but if anyone tries to read it, they will no longer know where it is, or when it was there. As long as they don't look, you're OK.
So just say "My homework is in the box with the cat" or something. They'll never be able to prove you wrong, because the act of observing your homework will destroy it! Neat-o!
This is so weird :|
Also after reading a bit of that link in time all I see is: Blablabla, blabalbalblalbal.Bla!.
I shouldn't be busy with stuff that you can't really touch.
Also after reading a bit of that link in time all I see is: Blablabla, blabalbalblalbal.Bla!.
I shouldn't be busy with stuff that you can't really touch
.Speaking of blablabla, blabla, blablabla, try reading this wonderful article about bridge for a high "wtf?!" factor :lol: I wonder if anyone else besides me has a clue what it's about :|