What is the biggest advantage to building a Quantum Computer?

Nature is already using the Quantum Computer. That is how it controls all of the red blood cells in the human body. It is also used in the eye to detect colors.

It is not an issue of building one- it is an issue of how to access the ones already in existence.

Trying to re-program or even construct on where an existing computer is can prove disastrous. Consider trying to load a windows program into an apple computer that is running a "program" already! If we turn the existing unit off to reboot it for our needs what kind of problems can come up is a real issue.

Would such an attempt result in a failure of the primary operating system of the universe or will it affect only the structure we are messing with is a question that no one has an answer for.

The Quantum computer is not limited to a binary reasoning system. It is faster, takes up less space and has more memory capacity then any computer we now have.

They can solve problems that cannot be solved by conventional computers. Generally, these problems involve the requirement for massive parallelism.

The easiest way to understand a quantum computer is to look at it from the Many Worlds Interpretation (MWI) of quantum reality. This is for visualization purposes only as the MWI inetretation may not be correct, however it does give you an idea of how quantum computing differs from normal classical computing.

In a classical computer, generally things are computed sequentially. While you can create some level of parallelism through multiple classical computers or to an extent with multiple software threads on a single computer, it is poor approach for combinatorial problems where you are ‘searching’ for a solution in an enormous search space. In practice, the problem cannot be solved in a reasonable amount of time.

With a quantum computer, thinking of it in terms of the MWI interpretation, you can view it as acting like a computer in each of multiple worlds all working on different parallel threads of the same problem at the same time. The more qubits you add, the more parallelism you can get. This makes it practical to solve some problems in a short amount of time that are not solvable by classical computers. Again, just using MWI as an easy way to build the mental model of what’s going on and not advocating that it is the correct interpretation of Quantum Mechanics.

A decent quantum computer would be thousands of times faster than a regular computer, for one thing.