So i've been working out of town and living in a hotel and I get crazy bored and I'm a huge geek... What does this lead to? me writing abotu quantum computing for those who might be interested.

I came up with the idea while reading the Funny Pictures Forum and stumbled across this picture:

http://img526.imageshack.us/img526/7569/schroedingerscatwantedwc1.jpg

Which is quite funny... but I happened to think I could perhaps contribute something and make you all sound a little smarter knowing more about Schroedinger's cat.

The poster basically sums up the idea behind S's (i'ma use S as a reference to Schroedinger because its too long to type out everytime...) cat. Basically you put the cat in a sealed box with poison in the box... I mean completelly sealed so there is absolutely no way of knowing anything about the cat, specifically whether the cat is dead or alive.

The theory is that during this moment in time that cat actually exists simultaneously in both states (both dead and alive). Some people like to describe it as the universe splitting into two parallel universes one with the dead cat and one with a live cat. Anyway, when you open the box and observe, then the 2 parallel universe rejoin and leave you with one answer (i.e. dead or alive).

Now I know this sounds crazy and dumb, but there are some pretty convincing scientific experiments to show this phenomenom of one item existing in 2 places or states at once. An easy example (that is also hard to grasp without somewhat of a physics background... but bear with me) is that of interference.

http://farm2.static.flickr.com/1273/532869775_3274e4548a.jpg?v=0


This photo displays the basic concept. If you shine a beam of light that passes through 2 small slits and then strikes a screen you will see an interference pattern on the screen. This pattern is caused by the fact that the distance that the light travels from the top slit to a point on the screen is slightly different then the distance that the light travelling through the bottom slit to that same point. If that difference in distance is equal to a whole number multiple of the wavelength (i.e. 1 or 2 or 3 times the wavelength) of the light then you get constructive interference and you see a bright spot. if the distance is equal to .5 or 1.5 or 2.5 times that of the wavelength, then the 2 incident beams of light destructivelly interfere and you get a dark spot.

Don't worry if you don't quite follow exactly how interference works, the point is that in order to get an interference pattern you need 2 photons, or 2 beams of light interacting with one another. (A photon can be thought of as a small packet of light containing exactly 1 wavelength of that light... please for all the other geeks don't get all nit picky and correct stuff I'm doing my best to make this as simple as possible). In the picture above these 2 beams are caused by the light coming from both the top slit and the bottom slit.

So... what happens if you have a light source (i.e. a light bulb) that is powered so minutely that only 1 photon is released every minute. (there are such light bulbs in existence and there are special screens that can detect 1 photon striking them). Anyway, logic and commen sense dictate that this photon can either travel through the top slit or the bottom slit and then strike the screen. In this case you would not have interference (as interference requires a photon coming from the top slit and one coming from the bottom slit interacting with one another).

However... you guessed it.. it still creates an interference pattern!!! this is scientifically proven. Ok... now how can this be? I've shown and it has been shown that interference requires 2 photons or beams of light having traveled slightly different distances interacting with one another... Well it all boils back down to S's cat! During the time that the photon leaves the light bulb and before it strikes the screen we have absolutelly no way of observing it... this means (if you still remember from before) that it actually exists simultaneously in both states. This means that that photon actually travels through both the top and the bottom slit! and when we can observe it again... i.e. when it strikes the screen, well we are left with the result of the photon having travelled through both the top and bottom slit, and get interference.

ok... more in a second (I'm typing just didn't want to post to get too long)

so evo X = Time Travel??? :godance:

Ok... this leads us to QUANTUM COMPUTING... lol, I like this stuff if you hadn't guessed by now.

Normal computing, or the vast majority of computing today, is sequential computing. This means exactly like the name implies, first line1 is computed, then line 2 (which may or may not depend on the result of line 1) is computed... and so on and so forth. Now the first thing to understand with quantum computing is that it is Parallel computing, so a quantum computer (if ever built) cannot just be plugged in and loaded with todays software and expected to be as much faster as you've all probably heard quantum computers are.

However, parallel computing does serve its applications. There has actually even been code written already to run on parallel processing computer (lookup Shor's Algorith.. i believe thats what its called). Primarilly this code has been written by those trying to break codes. To give you an idea of the power of a quantum computer (if ever developed), a quantum computer running this parallel code could crack a code 1million times the size in 1/millionth the time as todays fastest computers. So yeah... pretty cool.

Oh yeah, the best way to think of parallel computing is to think of modern day computer games and video cards. GPUs (graphic processors) are largelly parallel because they repeatedly do calculations on a large number of things that aren't dependant on the previous calculations result.

Anyway... on to the theory of quantum computing. Most of you know that computers operate using 1s and 0s (or in binary). A 5 bit number is therefore a combination of 5 1s and 0s. so 00000 is = 0. 00001 is 1, 00010 is 2, 00011 is 3 (2+1), 01000 is 8, and so on so forth. (wikipedia or google binary) but the point is that a 5bit number can reprent 2^5 or 32 numbers (0 through 31). A 7bit number can reprent 2^7 or 128numbers.

So, if you were asked to find the first whole number that contain certain features.. for example the first whole number whose square and power to the third contained all the digits 0 through 9. Then with modern day computer you would write a code the started with 1 and took its square and power to the third and checked it to see if it contained all the numbers, if not then you would move on to 2, then 3 and so on and so forth untill you found the answer.

if your confused here's an example. 64 squared = 4096, and 64 to the third = 262144. So you have a 0,1,2,4,6,9. So this is missing a 3,5,7 and 8. So this is not a solution. However, 69 squared = 4761, and 69 cubed = 328509. Thats your answer.

With your modern day computer it would have taken 69 iterations to solve this problem. With a quantum computer it would only take 1! HOW?

If you found a way to represent a 7 bit number and then to perform an action to the bits representing that number that either made them a 1 or a 0... and then you did computation on those bits all without ever observing the bits, and then finally observed the result... the result would be 69, or 0100101. OK... I know that didn't make alot of sense.. so a more detailed version:

Imagine you could use the spin of an electron to represent a bit. If that electron is spinning clockwise then its a 1 and if its spinning counterclockwise then its a 0. Now take 7 atoms and put them in your quantum computer (Oh yeah, a quantum computer would almost definetly look absolutelly nothing like what modern computers look like...). Start each atom with the electron spinning counterclockwise (representing 0). Now seal up the computer and bombard the atoms with enough energy that it either could or could not reverse the spin of the elctrons. This would now put the system in a state similar to S's cat. Since we don't know anymore which direction the electron is spinning, it actually exists in both states (remember our interference example).

This means that our seven electrons now represent the numbers 0-127 simultaneously. Why because it could be 0000000, or 0011010 or whatever other combination. So, if you can now perform a calculation on these electrons... (in this case comparing them to see if the square and the cube of the number contain all the digits 0-9) without ever observing the electrons (tricky part of quantum computing) and then observe the result... well the result will be 0100101! which is our answer! 69!

This is because after the computation the electrons contain the result for all the numbers 0-127. (if you want to imagine there being 128 parallel universes each with one result thats fine) But when we observe the result it re-combines those 128 universes into 1 universe, and that universe is the universe where the electrons that reverse spin with that initial bombardement of energy were the ones for the number 69!

anyway, pretty cool. And the best part, the one that will really blow your mind, is that they have built quantum computers that can perform very basic operations, like 1+1, but they actually work!


anyway... thanks for entertaining my boredom. (And thanks for the reply right in the middle of my posts Antics, and yes now I'm going to have to go back in time and kill you before you could make that post:evillaugh:)

my head a splode (http://www.homestarrunner.com/sbzone.html)

I get the cat example (I've heard it before), but I'm not quite sure on how a computer would operate as you described to solve that problem.

Lol... its ok. I tried the bestest I could. The hardest part to grasp for me is that the actual act of observing the result also plays an important role in the computational process. (Well i guess its all hard to grasp). But anyway, when you observe the result then you are also removing that possibility for each electron to exist in either state. Now as to why the electrons will be in the proper state to give you the proper answer? that I can't really explain. I've read alot and tried to figure that out and I believe it has to do with how the computation is performed on the electrons during the period that they can exist in either state.

Anyway, I'm not an expert on this, but I've read quite a bit and did a 20 pager report (I know its not a thesis or anything) on quantum computing. More what I was trying to convey was the basic principles behind it just to sort of skim the surface of how it works. Just was hoping that if anyone actually read that entire post that they would feel like they had learned something and that they knew alot more about the basics of quantum computing then before.

In the end though, I've been a physics guy my whole life. Did electrical engineering and learned a great deal about quantum mechanics and quite a bit of advanced computing and electronics and physics, and to me quantum computing still doesn't fully make sense and still is hard to grasp. So if you don't get it thats expected, but if you maybe sort of got the basic principles that it is based off of then i did my job lol.

LOL... and to blabber some more. Just thinking about this now, and what I'm about to say has absolutely no research or backing to it.

Anyway, as part of the computational process for that problem there would need to be a compare. now if that compare step turns out true... i.e. all the numbers 0-9 are represented in the square and the cube of the number tested, then you would somehow need to store that result. so i guess if its true then if you set somehow another set of 7 electrons to have the same spin as the set that resulted in true, then you would have your result.

This is interesting stuff, what I am getting at is that the computer can do math in 2 different dimensions?

haha... yeah... but not just 2. With a 7bit number your talking a 128 possible "states" which in other words means 128 different dimensions.

Now... just imagine a quantum computer running 64bits.... thats 2^64 different possible state and therefore 2^64 different computations would all occure simultaneously in 2^64 different "realms" if you would like to think of it that way.

fyi... 2^64 = 18,446,744,073,709,551,616

haha... yeah... but not just 2. With a 7bit number your talking a 128 possible "states" which in other words means 128 different dimensions.

Now... just imagine a quantum computer running 64bits.... thats 2^64 different possible state and therefore 2^64 different computations would all occure simultaneously in 2^64 different "realms" if you would like to think of it that way.

fyi... 2^64 = 18,446,744,073,709,551,616

Oh, I think I got it. Interesting stuff :thumbup:

haha... yeah... but not just 2. With a 7bit number your talking a 128 possible "states" which in other words means 128 different dimensions.

Now... just imagine a quantum computer running 64bits.... thats 2^64 different possible state and therefore 2^64 different computations would all occure simultaneously in 2^64 different "realms" if you would like to think of it that way.

fyi... 2^64 = 18,446,744,073,709,551,616

Who knows really... because they rejoin as immediately split. Is it really another dimension or the same dimension while in calculates. What's crazier is getting into fractals.

http://www.popsci.com/entertainment-gaming/article/2008-03/super-mario-multiverse

Mario does a better job hahaha