## Why do we need a quantum computer? How is it different from other computers? How does it work?

A quantum computer is a device that emerged from the need to use quantum mechanics to transmit data.

Why did we need such a device?

Long ago, when computers first appeared, the size of a computer was the size of a room. Therefore, computers were not as useful as they are today. Then the transistor was invented and computer sizes became smaller. Transistors serve as a type of switching in electrical circuits. In other words, the passage or failure of information through the circuit is under the control of these devices.

You can make a transistor smaller and smaller, which is what the scientific community has done. Finally, their sizes were reduced to atomic dimensions, but there was a problem that this situation caused: quantum tunneling.

We can say that the tunneling phenomenon has made the passage or stopping of information at the desired moment out of control. In this case, the increasing need for processing power and speed has reached its limit in classical physics. Especially some scientific simulations or calculations contain a lot of data and unknowns. Doing these with classical computers can take more than a human lifetime. Therefore, we needed a brand new technology and the sought-after blood was found in the quantum world.

Another reason is that quantum computers are safer. In a normal computer, the chance of cracking a password is high – even if it takes time – but in a quantum computer, this time can still exceed a human lifetime. Moreover, it is much more difficult to decrypt and infiltrate the system. This makes these computers more secure.

What is the difference of quantum computer? How is it working?

The smallest unit that carries information in a classical computer is a bit. The number of bits that can only take the value 0 or 1 can increase as the complexity of the information increases.

Quantum computers use qubits, not bits. qubits work with the principle of superposition, an interesting phenomenon of quantum mechanics. that is, they take the value of both 0 and 1 at the same time.

The values for 4 of the classical bits could be:

0000

0001

0010

0100

one thousand

1111

1110

etc…

You can already guess the remaining combinations. These are 16 in total, but the same number of qubits contain all 16 combinations at the same time. If we add a new qubit to the information, the number of combinations does not increase by 1. The increase in qubits is exponential. They do not give an input to an output like classical computers. They give a combination of outputs, again resulting from superposition.

Can these computers solve every problem?

No, although it may seem so. There is no such thing, at least for now. These computers are famous for being able to solve complex problems quickly, but they often have limited sets of algorithms that can only solve certain programs. So they are not experts in everything. Therefore, in some cases, a classical computer may be more useful to you.

It is unknown what the future will bring, but for now, these devices are not user-friendly devices that can enter everyone’s home or office. For now, they can only be used to solve some scientific problems. You can still build a quantum computer at home using qiskit.