Recently, the Prime Minister of Canada Justin Trudeau amazed journalists by giving a short explanation of quantum computing. In the weeks after, many articles about quantum computing were written commending the president for explaining so eloquently this impenetrable new science. And while it is very exciting to have so many people engage with what is considered the next great frontier of computing, some of the explanations were rather disappointing, and because of the (perceived) complexity of quantum computing it is very easy to give the impression that it is even more magical and mysterious than it really is.
The biggest misconception that propagated was that the miracle of quantum computing is down to the wave-particle duality of fundamental components such as the proton, neutron, electron etc. The key to quantum computing in fact relies on the superposition of states: taking for example a proton, this has a property (which we don’t need to go into but you can read all about) called spin, which when measured in a laboratory will always be “up” or “down”. The fact that a stream of protons can also act as a wave is not the most relevant fact here.
So just quickly: what of the fact that spin is always measured as one of two states? It is that the only way of modelling mathematically the spin of a proton involves inherent randomness. It is possible to put the proton in an equal superposition of both up and down, with the binary result of an experiment only being resolved when actually measured, both up and down equally likely outcomes. Until then, the spin state is genuinely both up and down equally. But the very meaning of the word “quantum” implies the existence of distinct values and therefore no measurement can actually reveal the superposition we know is there. Rather, in a sense, we force the universe into making a decision at the last possible moment!
So Justin Trudeau and various journalists are right in saying that a bit is binary but a qubit (quantum bit) can hold multiple values at the same time, but it is not the wave-particle duality that underlies this phenomenon.
Quantum computing is obviously far too complex a subject to go into further, but I strongly encourage you to do your own research. It is fantastic that this subject has been given more media attention, but any subject that captures your interest always deserves further research beyond journalistic simplifications. This post isn’t so much about quantum computing itself, but a reminder that initial engagement is just the first step!
Written by William A. Lebreton.