How does a quantum computer exploit quantum mechanics ? More precisely, what is the usefulness of a qubit ?
???? Quantum computers ?????
Gabriel Lewis
Ian Garcia
I was gonna explain but then I realized that I don't actually understand it.
I know a qubit is a superposition of 1 and 0, and if you combine n qubits without collapsing the wavefunction, you have a superposition of 2^n states. You're essentially doing 2^n calculations simultaneously. But in the end (as far as my understanding goes) you have to collapse the wavefunction and you can sample just a single one of all the states to get an answer. So I still don't understand why it's actually faster.
Connor Richardson
>So I still don't understand why it's actually faster.
it just werks
Wyatt Garcia
Thanks, it's all clear to me now.
Found this, gonna read it, looks like it will make things clearer
cs.virginia.edu
Owen Allen
That picture doesn't really make any sense, it suggests that they are vectors and that (1)=-(0) so (0)+(1)=0
Jose Baker
That's it exactly, I don't really understand what the quantum mechanics are used for.
Apparently, according to your document, there's a thing called "destructive interference", wich "destroys" quantum states wich have a low probability in relation to something, in relation to the problem I guess. But how the problem is expressed and transmitted to the particles I don't understand ...
In short they found a way to make the interference chose not some random state but one that has a neutral amplitude somehow in relation to the problem.
Anthony Sanchez
ops pic is misleading
on top of qubit should be 0,0 0,1 1,1 1,0 and bottom should also be 0,0 0,1 1,1 1,0
Luke Rogers
Where once there was only either 0 or 1, now there is 0(0) or 0(1) and 1(0) or 1(1). The quantum part is just a homage to quantum superposition, similar thing
Jonathan King
If you want to see simple algorithms where quantum computers perform better than classical ones, look up the Deutsch-Jozsa algorithm (probably the simplest "useful" algorithm) or the Grover search. Both use only elementary linear algebra (contrary to e.g. Shor's algorithm, which is more difficult to understand).
Kevin Bell
>there's a thing called "destructive interference"
Brandon Jenkins
Isn't quantum mechanics like when you have some small thing and then it changes according to your willpower or something. Like it proves that Jesus is Lord or something my pastor said.
Cameron Fisher
For [math] e \in \bar{R} \\For~~e=i\\ Then~ |~0> and~|~1>\\~~~Becomes~ |~i> and ~|~i> \\Cycle~thru~"e's"~for~the "lengths"~of~a~qubit. \\
[/math]
Am I close?
Matthew Wood
*sigh* You know I do have like a physical form and an address and a phone number and blah.
Why does Veeky Forums keep pumping the G.O.A.t whilst claiming y'all aren't into bestiality?
Cooper Sanchez
In layman's terms, do you know how some computational problems exhibit the so called exponential "blow up"?
Quantum computers, from my understanding so please take this idea with a grain of salt, allow you to explore this exponential complexity and offer more computational power by its inherent ability to explore an exponential number of solutions.
For example, as of now, it is believed that there is no efficient algorithm for computing the prime factorization of integers in polynomial time. It is believed that the problem of finding of factoring integers on a classical computer is non polynomial, meaning that it will take an incredibly long time to factor these integers. According to Wikipedia, just to factor a 232 digit integer took a lot of computers 2 years to do so.
But there is a quantum algorithm, called Shor's algorithm, that can do it in this so called polynomial time. Once a fully realized quantum computer can be built, it can do this 232 integer factorization in a considerable much less time than 2 years.
But how does it exploit quantum mechanics? By the principle of superposition, by being in two states at the same time can you only explore an exponential amount of solutions.
If you have two qubits in a superposition you can be in a superposition of 4 classical states at a time.
If you have three qubits in a superposition you can be in a superposition of 8 classical states at a time.
...
If you have n qubits in a superposition you can be in a superposition of 2^n classical states at a time.
This is why a cubit is incredibly useful. It can only be useful to us if a physical representation of it can be manipulated and controlled. In its own right, it's definitely interesting.
Chase Perez
I'm pretty sure it involves doing the computation multiple times and getting a probability distribution of the answer.
Idk where all the speedup is coming from though.
I already grasp finite state automata, pushdown automata, and turing machines. I'm looking at their quantum analogs.
Nolan Reed
Quantum computers works with the fact that every qbit is 0 and 1 at the same time, so you can process that 1 or 0 at that moment, in conventional computers you need a step to process an 1 and another step to process an 0.
Dylan Moore
I'll take 'what is a brain' for t=0 please thank you bob.
Parker Jackson
Well that explanatin is not very suitable for one qbit, but for two or more, anyways, is the simplest description i can present.
Colton Stewart
Frame of essence did a fantastic video on this, check it out:
Oliver Gonzalez
...but i am.
Andrew Murphy
Qubits aren't useful. Entangled qubits are useful.
Brayden Brown
great video
Jaxon Gutierrez
i was gonna post this before, but i went to get food, anyways here are 2 links, one is to the first lecture in a course on quantum computing, one is a paper on quantum computing, unfortunately this will be impossible at least for maybe 50+ years, the main issues is the 3 qbits for ever qbit issue, the error correcting code for a qbit requires 3 qbits for each one, this 46 bit qbit computer by google requires about 1 petabyte of data for it to run
cs.cmu.edu
arxiv.org