Quantum Computing (N04)

Is Quantum Computing (QC) hype or realistic? A major consulting firm McKinsey did an analysis in June 2021 and rated the market adaptation maturity of QC at 2.9 on a scale of 1 to 5 where 1 is for bystanders, 2 for beginners, 3 for learners, 4 for professionals, and 5 for legends. Another leading technology company IBM has published its QC technology roadmap to 2024 and gave very specific technology development targets. QC appears real and not hype.

What is the current technology readiness position? IBM said the fastest classical computer was equivalent to a quantum computer of about 50 Qubits and IBM has recently achieved making a QC with 50 Qubits. What is Qubit? Qubit is the building block of a quantum computer just like bit for classical computers. A bit has a state of 0 or 1, whether we measure it or not. A Qubit has a state of 0 and 1. When measured, Qubit shows either 0 or 1 like a bit. But we must not assume the status when unmeasured is the same as measured. This is confusing. This weird property of Qubit is called Superposition.

IBM uses an expensive superconducting approach to make Qubits. Superconducting means electricity passes through a conductor without loss, and this is achieved when temperature is absolute zero (-273C) or close to. The low temperature is needed to minimize the unrest of atomic states called noise. The measured state remains stable for a very brief period in nanoseconds.

The power of Qubits amplifies when they entangle. This is weird too although we can relate the idea to bundling teamwork for higher productivity. When 2 Qubits entangle, measurement of state could show 00, 01, 10, or 11. When 4 Qubits entangle, the possible number of measured values increases to 8. In mathematical terms, the number of states of entangled Qubit is 2^N where N is the number of entangled Qubits. For examples, if N =2 then states = 4, if N=3 then states = 8, and if N=50 then states= 1130 trillion. This exponential rise of states enables Quantum Computers to execute in parallel exponentially faster than classical computers. A simplistic analogy (not technically correct) is that a QC with 50 Qubits is equivalent to 2^50 classical single core computers or a super classical computer with 2^50 cores. The current challenge is how to make QC with a lot of Qubits such as 1000.

Having read about these weird features, do we still want to develop Quantum Computers? Yes, because they are superfast. There are still a lot of applications taking billions of years to compute by classical computing. They will only take seconds if computed by a quantum computer. Nevertheless, not all applications can make use of the weird features of Quantum Computers. Classical computers serve general purpose applications, and they will stay for a long time. Decryption (factorization of security keys) is a killer application of QC. Deciding the best route to visit 50 cities on one trip for the shortest time or lowest cost is another well known application example easily computed by QC.

This article does not explain how the weird properties of quantum computers come about. It simply explains that quantum computer is not hype and is genuinely usable. It also provides some comparisons of quantum computing with classical computing as the first step towards understanding this topic. Perhaps we have obtained more questions than answers after reading this article. This situation motivates us to understand more of what we do not understand.