what is mean by quantum computer?

Answer 1

Here are some very interesting reference sites:

This is my favorite for explaining them and how they work! ...(they even provide a simulator!)
http://www.cit.gu.edu.au/~s55086/qucomp/

Quantum computation
http://www-users.cs.york.ac.uk/schmuel/comp/comp.html

How quantum computers will work:
http://computer.howstuffworks.com/quantum-computer.htm

The Quantum Computer:
http://www.cs.caltech.edu/~westside/quantum-intro.html#qc

Answer 2

MANOJ will this help

First proposed in the 1970s, quantum computing relies on quantum physics by taking advantage of certain quantum physics properties of atoms or nuclei that allow them to work together as quantum bits, or qubits, to be the computer's processor and memory. By interacting with each other while being isolated from the external environment, qubits can perform certain calculations exponentially faster than conventional computers.

Qubits do not rely on the traditional binary nature of computing. While traditional computers encode information into bits using binary numbers, either a 0 or 1, and can only do calculations on one set of numbers at once, quantum computers encode information as a series of quantum-mechanical states such as spin directions of electrons or polarization orientations of a photon that might represent a 1 or a 0, might represent a combination of the two or might represent a number expressing that the state of the qubit is somewhere between 1 and 0, or a superposition of many different numbers at once. A quantum computer can do an arbitrary reversible classical computation on all the numbers simultaneously, which a binary system cannot do, and also has some ability to produce interference between various different numbers. By doing a computation on many different numbers at once, then interfering the results to get a single answer, a quantum computer has the potential to be much more powerful than a classical computer of the same size. In using only a single processing unit, a quantum computer can naturally perform myriad operations in parallel.

Quantum computing is not well suited for tasks such as word processing and email, but it is ideal for tasks such as cryptography and modeling and indexing very large databases.

AND THIS

A future technology for designing computers based on quantum mechanics, the science of atomic structure and function. It uses the "qubit," or quantum bit, which can hold an infinite number of values. In 1999, the feasibility of such a computer was demonstrated by a collaboration of scientists at MIT, the University of California at Berkeley and Stanford University, which used a technique similar to MRI scans in hospitals. The computation that was accomplished was an ingenious search algorithm devised by Lov K. Grover of Bell Laboratories.

The concept is that the atoms can be made to perform higher level gating functions rather than just be used to store 0s and 1s. It is believed that such a device can handle multiple operations simultaneously and can factor large numbers 10,000 times faster than today's computers. In late 2001, researchers at IBM computed the factors of the number 15 using quantum techniques. Although there are gigantic hurdles to overcome, scientists believe this will be feasible some time in the future.

If quantum computing were to come about, the world of cryptography would undergo a dramatic change. In a short amount of time, such a device could be used to find the secret keys to all encryption algorithms.

Answer 3

Normally, we consider a bit to be on or off depending upon the voltage. Well, what if we were able to entail more information in a single bit.... or more precisely in the relationship between the bits. It amounts to being able to process much more data using fewer bits. It's still in its infancy but see the wikipedia entry for more information.