**8. Why do these quantum effects matter?**

Simply put, they are extremely useful to the future of computing and communications technology. It is due to **superposition** and **entanglement,** a quantum computer carry out a vast number of calculations simultaneously. We know that a classical computer works with ones and zeros, however a quantum computer will have the advantage of using ones, zeros and "superpositions" of ones and zeros. Certain difficult tasks, e.g. code breaking, that have long been thought impossible (or "intractable") for classical computers will be achieved quickly and efficiently by a quantum computer.

Quantum computing is not just "faster" than classical computing, for many types of problems the quantum computer would excel, such as code breaking. The power, which is required for code breaking, is derived from quantum computing's use of "qubits" or "quantum bits."

#### **8.1 What can a quantum computer do that a classical computer cannot?**

It is easy for any computer to do factoring of large numbers or multiplying two large numbers. But calculating the factors of a very large (say, 500-digit) number, on the other hand, is considered impossible for any classical computer. In 1994, a mathematician from MIT, Peter Shor, came up with the claim that if a fully working quantum computer was available, it could factor large numbers easily.
