Interesting
Sounds like it could be an important step. But why does my brain want to explode whenever I try to understand quantum computing?
Much of the current research on the development of a quantum computer involves work at very low temperatures. The challenge to make them more practical for everyday use is to make them work at room temperature. The breakthrough here came from the use of some everyday materials, with details published today in Nature …
An easy way of thinking is to think of it covering every possible state simultaneously. Due to limits in the number of bits needed to do this, it reduces your computational reach, but increases the speed (to theoretically instant results).
So say you had around 256bits worth of qbits (32bytes?) you could theoretically break 256bit encryption in an instance. The current problem is, you still need the rest of the computer to see if those bits decode your message. Which takes normal time. Which means currently there are very few applications for quantum computing.
But once we are also uploading your code breaking program and the encoded messages into a fully functional quantum computer, then we may be able to do really quick codebreaking (or search on Google in a femtosecond!). :P
"That is the part that I don't understand"
I'm with you. For me it seems like saying a totally black piece of paper contains the text of every and any book or text ever. I get this. I don't see how it helps though!
Didn't Richard Feynman say "If you think you understand quantum mechanics, you don't understand quantum mechanics."
"but how does the superposition of all states (0,1,2,3) collapse to the correct answer?"
This stuff gives me anxiety when I try to figure it out, but I find it perversely fascinating.
The best answer I can wrap my head around is that a superposition collapses to a known state when observed, and the observation itself determines the collapsed state.
In this case the the "observation" is actually done by the equation "3 - 2", which causes the superpostion to collapse to the desired state "1".
The word "observation" is actually misleading, as it implies intelligence and intent. It's actually any action on the superpostion that causes it to collapse.
That's why superpostion is so hard to maintain. Literally anything, energy, matter, random quantum fluctuations, can collapse it.
Where's my headache pills?
El Reg published a (rather better written) article on this two days ago. Why are we getting a reprint from The Conversation - with a lower information content?