Quantum computer vs conventional computer?

Julieta Suleiman: well its great i say but one odf the imacs i saw was 2098 dollars and mac OS sucks personally they are not that fast either and can't do operation that quick so imagine how much one of those would cost

Angelyn Ducas: If I had a quantum computer, I would be able to break into your Yahoo! Mail account and read all that information that you don't want me to see. Quantum computing is amazing, but, like the atomic bomb, I'm not sure if the human race can handle it right now. Since large numbers can be factorized very quickly using quantum algorithms, classical encryption schemes relying on the difficulty of factorizing integers will become useless. In fact it's difficult to say that the American intelligence agencies (and others) aren't already in possession of quantum computing technology, and that they don't use it routinely to access information you think is secure.It's not true that you won't have to upgrade a quantum computer, however. I don't see ! why this would be true. What about the hard drive? The amount of information possessed by the human race is increasing exponentially (yes, I actually mean exponentially - not quadratically or something like that.)...Show more

Iris Shawcroft: Your understanding of quantum computing is flawed. As it turns out, quantum computers do not perform operations faster than classical computers. The speed of an operation is based ENTIRELY on the system that is being used. You can make a classical computer out of M&M's and trained monkey. It will be very slow and you would be much better making it out of silicon transistors, but both will be classical computers. Similarly, you can make a quantum computer out of different systems (ions, josephson junctions, etc) and the speed of operations depends on what you use. But, as it turns out, all of them are currently slower than silicon transistors and have little or no prospect of being any faster.You are also wrong about the tran! sfer of information. Quantum computers can utilize quantum te! leportation to transfer information, and part of this protocol involves an instant (faster than light) transfer. However, to finish the protocol, information needs to be sent which has to be sent over a classical channel. The fastest a classical channel can be is the speed of light, but if you are planning on transferring the information only over the length of the quantum processor, you would be better off just using an electrical wire which is what is used in classical computers. So the transfer rate is no better than a classical computer.Furthermore, quantum computers will be no better than classical computer at almost all tasks. There are only two or three tasks that a quantum computer out performs a classical computer: factoring (ie 15=3*5), and various types of unstructured search (ie database searching). But for almost everything else a computer does, which is almost everything your computer does, a quantum computer is not advantageous.The utility in quantum com! puting lies in the fact that a quantum computer uses a fundamentally different computing mechanism that requires superposition (something a classical computer is incapable of). This different mechanism allows a few types of problems to be solved more efficiently. It is not that the operations are faster in a quantum computer (because they are not), it is that a quantum computer will require fewer operations!And there aren't even that many people interested in the types of problems that a quantum computer would be good at. Database searching is not something that current computers are too slow at, so no one really needs to make a quantum computer for that purpose. The other main use of quantum computing is factoring numbers. The only reason anyone cares about this is that it would allow the owner of the computer to crack codes, which in turn would allow them to spy or steal credit card numbers. You see, all encryption these days is based on RSA or RSA-like codes that c! an be cracked if you can factor a really really big number. But classi! cal computers are not efficient at factoring, so to crack a 128-bit number would require months or years on a classical computer. A quantum computer, if sufficiently big and fast, could beat the classical computer at this factoring, possibly by a lot. So, if you aren't interested in database searching or spying on people, you probably should not be that excited about quantum computers. Or course, there is always a chance someone will come up with a way to make quantum computers more generally useful, but that has not yet happened....Show more