Advantages and disadvantages of quantum computers?

The advantages of Quantum Computing

It has been shown in theory that a quantum computer will be able to perform any task that a classical computer can. However, this does not necessarily mean that a quantum computer will outperform a classical computer for all types of task. If we use our classical algorithms on a quantum computer, it will simply perform the calculation in a similar manner to a classical computer. In order for a quantum computer to show its superiority it needs to use new algorithms which can exploit the phenomenon of quantum parallelism.

Such algorithms are not easy to formulate, but once discovered they yield spectacular results. An example of one such algorithm is the quantum factorization algorithm created by Peter Shor of AT&T Bell laboratories. The algorithm tackles the problem of factorizing large numbers into its prime factors. This task is classically very difficult to solve; in fact it is so difficult that it forms the basis of RSA encryption, probably the most popular method of encryption used today. Shor's algorithm cleverly uses the effects of quantum parallelism to give the results of the prime factorization problem in a matter of seconds whereas a classical computer would take, in some cases, more than the age of the universe to produce a result!

The disadvantages of Quantum Computing

The technology needed to build a quantum computer is currently beyond our reach. This is due to the fact that the coherent state, fundamental to a quantum computers operation, is destroyed as soon as it is measurably affected by its environment. Attempts at combating this problem have had little success, but the hunt for a practical solution continues and some encryption Problem as well because mostly all the encryption-decryption Algorithms are based on Prime Factors and using Quantum Computer we can easily calculate the Prime factors of any number.