Quantum computer works best switched off

Metatwaddle · Post by **Metatwaddle** » 2006-02-25 04:43am

CaptainChewbacca wrote:So, when do we plug it into the Heart of Gold?

We don't plug this one into the Heart of Gold, we ask it the answer to Life, the Universe, and Everything.

This is Deep Thought. Remember? "Even before its data banks had been connected up it had started from 'I think therefore I am' and got as far as deducing the existence of rice pudding and income tax before anyone managed to turn it off."

Siege · Post by **Siege** » 2006-02-25 12:37pm

Surlethe wrote:However, if the percentage of deflection is small enough, on average only a percent of an actual photon will be deflected, and thus, after enough turns around, no photons will actually have gone through the box, but the wavelength will have been affected by the probability of something going through the box. Then, we bounce the light over the mirror, separate it into a spectrum, and compare it to what we expect for no deflection at all, to find out if there's a probability of anything in the box. Did I get it?

If that is the case, then I *think* I now have a vague shadow of an idea of how this whole thing works.

That is, I'd know vaguely how. My mind is in the process of screaming BUT WHY!!!!11! at me now.

Yay!

Tasoth · Post by **Tasoth** » 2006-02-25 08:22pm

See, I started this thread with no fucking clue how this worked and now I'm pretty sure I understand the concept.

I love this board.

CarsonPalmer · Post by **CarsonPalmer** » 2006-02-25 09:16pm

I think this is one of those things that certain people can understand, and the brains of everyone else start shouting "DOES NOT COMPUTE! DOES NOT COMPUTE!" My brain is kind of screaming that now.

J · Post by J » 2006-02-25 09:47pm

CarsonPalmer wrote:I think this is one of those things that certain people can understand, and the brains of everyone else start shouting "DOES NOT COMPUTE! DOES NOT COMPUTE!" My brain is kind of screaming that now.

But does that mean it computes in the quantum sense since the quantum computer computes by not computing?

I think I'll just call it the Zen computer, it does by not doing.

CaptainChewbacca · Post by **CaptainChewbacca** » 2006-02-25 11:00pm

J wrote:
CarsonPalmer wrote:I think this is one of those things that certain people can understand, and the brains of everyone else start shouting "DOES NOT COMPUTE! DOES NOT COMPUTE!" My brain is kind of screaming that now.
But does that mean it computes in the quantum sense since the quantum computer computes by not computing?

I think I'll just call it the Zen computer, it does by not doing.

It computes in the quantum sense because it computes in realities in which it IS on, if I understand correctly.

Post by **Surlethe** » 2006-02-26 01:40pm

I think it might be good to discard conventional notions of "on" and "off". A quantum computer might be 99% off, but it's still 1% on, and that 1% can still give an answer, if I understand correctly.

Macross · Post by **Macross** » 2006-02-26 02:20pm

Dr Farnsworth: "No fair! You changed the outcome by measuring it!"

drachefly · Post by **drachefly** » 2006-02-27 12:02pm

Surlethe wrote:Drachefly, please correct me if I'm wrong, but here's what I get in my head from your post:

You're missing the mirror that would re-integrate the photon stream. Note that I have no clue how THAT optical element works.

Surlethe wrote:IF there is nothing in the box, on the other side, the reflected will reintegrate into the light wave -- but in doing so, it will slightly affect the wavelength of the light.

it will affect the phase of the light, not the wavelength.

Aside from that, yeah.

After a bit more thought, we have two eigenstates,
|+> and |->
where |-> has not gone through the box and |+> is the orthonormal eigenstate such that after going through the box, the state is

|b> = |->cos a + |+> sin a

with a small.

For photon interception, the probability is
(sin a)^2 ~= aa

but for looking at the phase shift, we have interference effects that vary as the cross-term,
(cos a) (sin a) ~= a

and these disappear much more slowly as you reduce a.

That, I think, is the crux.

Post by **Surlethe** » 2006-02-27 02:44pm

drachefly wrote:You're missing the mirror that would re-integrate the photon stream. Note that I have no clue how THAT optical element works.

Yeah; I did forget that, didn't I? My bad.

Surlethe wrote:IF there is nothing in the box, on the other side, the reflected will reintegrate into the light wave -- but in doing so, it will slightly affect the wavelength of the light.
it will affect the phase of the light, not the wavelength.

Thanks for the correction.

White Haven · Post by **White Haven** » 2006-02-27 04:24pm

Hmm. We need to expand this, so that I can achieve a state of quantum employment, where I get paid for work that was done by a partial probability of me working in another reality.

Keevan_Colton · Post by **Keevan_Colton** » 2006-02-27 04:30pm

White Haven wrote:Hmm. We need to expand this, so that I can achieve a state of quantum employment, where I get paid for work that was done by a partial probability of me working in another reality.

It already exists, it's called government work.

Plushie · Post by **Plushie** » 2006-02-28 11:27pm

I read through half the first article, a quarter the second article, and the first sentence of the posted explanation, then my brain looked at me weird and said, "You're on your own", and dribbled out my ear.

Jaepheth · Post by **Jaepheth** » 2006-03-02 10:48pm

There's fliers around some of the engineering buildings here advertising a graduate computer science course that introduces quantum computer programming.

One of the questions on there (that I assume is covered in the course) is "What is the square root of the logical operator OR?"

Post by **Surlethe** » 2006-03-03 12:02am

Jaepheth wrote:One of the questions on there (that I assume is covered in the course) is "What is the square root of the logical operator OR?"

How does that work?

drachefly · Post by **drachefly** » 2006-03-03 12:52pm

In quantum mechanics, all the operators are linear operators (i.e. they can be represented as matrices).

You can take linear operators to powers, including 1/2.

So, you get the operator which does the job of the OR operation, and take it to the 1/2 power.

I THINK...
on a state vector | a b > with a = 'true' or 'false' and same for b, then the 'or' operation is the matrix

(0 1 1 1)
(1 1 1 1)
(1 1 1 1)
(1 1 1 1)

or perhaps it's just

I - |false false><false false|

I'm not sure which, I'd have to fool around a bit with it.

Now all you need is to find a matrix which when multiplied by itself yields that.
In the second case, the 'or' operator is its own square root.

Yogi · Post by **Yogi** » 2006-03-03 02:11pm

So this is why security in Star Trek sucks.

"But Sir, I specifically programmed the computer not to run any strange programs it came accross."

Stile · Post by **Stile** » 2006-03-04 01:03am

And just for some fun on what this computer might look like: +http://www.sluggy.com/daily.php?date=060304