Quantum Computing - WTF is that?

As Richard Feynman said "if you think you understood quantum theory then you have not understood it".Using quantum mechanics in computation is the next revolution the tech-world is going through, but it seems tough to understand. Let see if we can digest it.

Unlike classical computer which has a basic unit called "bit" which can either be a 'zero' or a 'one', quantum computer has a basic unit termed as "Qubit" (Quantum Bit), which has typical property it can have 'zero', 'one' as well as 'both', yes you read it right both. A typical qubit can have both zero and one at the same time. Its like yes and no at the same time, wait what?

Its like being sociopath and psychopath the same time (although psychology says you can)....how is it even possible.If qubit gets bit by a Dracula and Zombie at the same time it can be both, although humans are not experimented and if done the scientists conducting the same are not alive to publish the results (sad..... I know...).

Lets visualize it by flipping an unbiased coin in air as a part of experiment. The outcome can be a head or tail with a 50% probability of occurrence. But what will be the state of coin when it's in air, heads or tails? We cannot say cause it's still in air. This state is referred as both head and tail state in quantum qubits, though the example is an analogy and qubit not really flips in air. But the question lies is this state useful and if yes then how can we come up with something meaningful with it.

To understand this let us take a scenario in which the user has to find password of an car key given we know that it's four bits. Conventional computer will try each an every options available one by one individually and then for the right combination of bits the car unlocks. So combinations from 0000 ,0001.......,1111 will be tried individually and in worse case scenario that's 1111 it will go through 16 iterations. But as the qubits can be zero and one at the same time, thus all the combinations will be checked at the same time and walla!!!the password will be breached in one iteration and the Mustang roars,

Actually not so. 

The password status will be correct and incorrect at the same time as the invalid combinations are also present. So the question of usefulness pops out. But scientists are the most smartest people around us.

Lov Kumar Grover devised one of the few operator to settle this issues called "Grover's operator" which eliminates all invalid combination. 

    "hail Grover".

The encryption used today are too secured and may even take a lifetime to break using algorithms based on conventional computer, but there are some algorithms devised for quantum computers which can break these encryption in exponentially reduced time period. 

So is this the end of the world?

Not quite, "Post Quantum Cryptography standardization" initiative has already started. To fight the encryption issue raised due to quantum computer ,Quantum computers are used. Hence, the Harry potter prophecy,"either must die at the hand of the other for neither can live while the other survives ..."