Quantum Computing

Applications

    As of yet nobody has built a fully functioning quantum computer for everyday use. However, interesting experimental applications of small quantum computers do exist. The most iconic among these is Shor's Algorithm, which is capable of factoring a number in log(N) time, where N is the number of inputs. Shor's Algorithm is incredibly complex, typically ending quantum computing courses. In brief is uses Fourier Analysis, and understanding of sequences and their periods, to produce a factoring in much less time than classical computing.
    A more practical application of quantum computers is in the cyber security world. Commonly encrypted keys are passed between computers to verify security. If the key is invalid, the interaction cannot go through. This plays an important role in many online commercial interactions. However, a skilled hacker could intercept this key, change the instructions of a communication over a network, and then once again submit this communication. Quantum Cryptography makes this impossible; if photons are passed in a superposition of states to verify the security of an interaction a hacker cannot intercept this key, in the form of photons, change the information, and resubmit they key as viewing the key will cause collapse of the superposition of the photons. By the No-Cloning theorem described earlier an attacker also cannot clone the superposition of photons. In essence Quantum Cryptography guarantees a single-use key.
    Such things are interesting, but do not answer the question; can quantum computers bring about a new age of computing? Classical computers are already reaching the limits imposed by the size of an electron, meaning quantum computers may have to be the next stage in hardware development, if there is to be one. Theoretically quantum computers have been proven to be capable of handling all problems a classical computer can handle, but the state collapse caused by large scale quantum computers may limit the size and scope of such machines. The future of quantum computing is unknown at this point.