Quantum Computing - from a novice point-of-view

Quantum Computing promise to change the world in the ways we will do computing and solve problems that we are unable to solve with traditional computers based on silicon transistors. We all have observed the physical limitation of the incumbent transistor gate that is currently down to about 10nm of contact length and provided the researchers can successfully use nanotubes as the new material, we may see 5 nm transistors in the near future.

Conceptually this technology and how the Quantum Computer is built could not be more different. Therein lay also the challenges and application constraints of the two technologies. Our conventional  silicon based computers  have already stopped scaling vertically due to heat issues when trying to reduce the contact length of the transistor gates, thus we are now resolving this issue by building multi-core systems, i.e. a horizontal scaling scheme requiring new programming models applied each individual operating systems as well as individual applications that enables different threads to be processed in parallel in multiple cores.

As it so happens, parallelism is what is the strength of the Quantum Computer.
Conventional digital computers store information as binaries, i.e. as bits that takes a value of either 0 or 1. Quantum Computers use the superposition of quantum states of particles, i.e. they use atoms, electrons, ions or photons to store information in elements called qubits.

As qubit can exist in superposition they can represent 0 or 1 or a superposition of 0 and 1 at the same time:

Unlike an electrical circuit, qubits are tiny particles (atoms has a size of 0.1-0.5 nm) that are magnetically suspended (or suspended by laser beams) in an extremely cold environment - fractions of a degree above absolute zero. What's so clever about this is that by keeping these particles in a state of superposition, they can simultaneously take on the role of both the 0 and the 1 in binary code.

Because qubits can contain these quantum multiple states simultaneously, Quantum Computers have the potential to be millions of times more powerful than today's conventional supercomputers.

The information in a qubit is encoded into its quantum properties such as the spin of an electron. The number of possible states equals 2^n for n qubits, i.e. two qubits can process four states simultaneously (in parallel) and 6 qubits can process 2^6 = 64 states simultaneously.  Each qubit can give just one answer when measured (under the mind-bending rules that govern the quantum world, measuring or even observing a subatomic particle alters it), but the superposition of states provides extraordinary processing power (if we can work out how to build them into a computer).

Currently the future quantum computer is targeting specialised parallel tasks including complex computations of possible folding configurations of complex molecules. Protein folding is an enormously complex computational problem (ref DNA/RNA) that is near impossible to solve with conventional computers.

Google has built a Quantum Computer with 9 qubits, IBM Research claims they will be able to build a ~50 qubits Quantum Computer in a few years, conversely IBM Research has also achieved to build a 5nm transistor based on silicon nanosheets that promises a 40% performance improvement over todays 10-14nm chips. To me, this pushes the Quantum Computer further into the oblivious future as we incline to lean towards conventional digital computers that are general purpose computers.