Anyone can understand quantum mechanics - Part 1

Pixar’s delightful movie Ratatouille – an animated film inspired by the world of French haute cuisine – features two characters with opposing views on cooking. On one hand we have Gusteau, a jolly and chubby chef with an optimistic message that he constantly repeats in his books and TV shows:

What do I always say? Anyone can cook!

On the other hand there is Anton Ego, a famous food critic who doesn’t just like food, he loves it. And if he doesn’t love it, he doesn’t eat it (hence his skinny figure). Mr. Ego is of a very different opinion than chef Gusteau:

I take cooking seriously. And no, I don't think anyone can do it.

At the end of the movie (spoiler alert!), Anton Ego has a change of heart, which he expresses beautifully in one of the greatest reviews ever.

To me, the answer to their dilemma is obvious: of course anyone can cook, cooking is easy – even I can do it! It definitely takes practice, with a few burnt dishes along the way, but it’s not like there is an insurmountable barrier only a few chosen ones can overcome. In fact, out of plain necessity, billions of people around the world cook their own food every day. However, it is also clear that we all cook with different degrees of skill and not anyone can do it as well as the best chefs in the world. For instance, I doubt that I could ever prepare this dish, “Lily bulbs, distillation of finger lime and lily and apple blossoms” from the restaurant Alinea in Chicago:

Lily bulbs, distillation of finger lime and lily and apple blossoms” from the restaurant Alinea in Chicago

Looks amazing! How do they do this?

So what does all of this have to do with quantum mechanics?

Simple: I believe that the Anton Egos of the scientific world have been spreading the message that quantum mechanics is a mind-boggling, counter-intuitive, and spooky theory that not even the greatest geniuses can understand. The truth, however, is that quantum mechanics is as easy to grasp as any other theory in science and its basic principles are something that anyone can understand; just like cooking.

Why would anyone spread the message that quantum mechanics is so difficult to understand?

A hundred years ago, when quantum mechanics was first emerging as a physical theory, everyone was extremely confused. Researchers had been trained following a scientific tradition that had been brilliantly successful at explaining the natural world and which gave a very compelling picture of what the universe was really like. In particular, scientists had been taught to view the universe as composed of elementary particles whose properties could be known and whose behaviour could, in principle, be predicted perfectly. Just try and imagine how difficult it was for them to deal with a new theory that was turning this picture of the universe upside down, a theory which claimed that the properties of physical systems couldn’t always be known perfectly and their behaviour could only be predicted probabilistically! The situation was not unlike what happened during Dagen H, the day when Sweden changed from driving on the left-hand side of the road to the right. Chaos, confusion, and disputes were inevitable.

Kungsgatan in Stockholm on Dagen H, September 3, 1967

Kungsgatan in Stockholm on Dagen H, September 3, 1967.

As a consequence of this clash with pre-existing views came the first examples of renowned physicists boasting about the difficulty of understanding quantum mechanics. In fact, at the time, there were many scientists who were manifestly arguing that the theory had to be wrong or incomplete. In retrospect, this comes as no surprise; it is to be as expected as traffic jams in Stockholm on September 3, 1967. The issue is that this confusion continues to propagate in many introductory courses and most tragically, in countless books and articles for the general public. As an example, the following is a recurring quote by Niels Bohr which I find to be the most irritating:

If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.

If Bohr is right, then either we’ll be shocked when learning one of the most important and fundamental truths about the universe – as opposed to enlightened and happy – or if we aren’t shocked, we’ll have to come to terms with the fact that we are not smart enough to comprehend it. A no-win situation. Thanks Niels.

This was the first generation of quantum physicists, people who were around at the time when the theory was actually proposed and built from scratch. With them came the first wave of confusion, caused by the clash between their pre-existing worldview and the basic principles of quantum mechanics. Their bewilderment is understandable and to be expected, but not something we should be teaching in the 21st century. Think about it, why would anyone keep bringing up this quote by Bohr? What are they trying to achieve? Nothing good in my opinion.

After quantum mechanics was developed into a complete and well-defined mathematical theory, it quickly begun to be successfully applied to many areas of physics. This lead to new technologies such as lasers and transistors, as well as to a deeper understanding of the properties of matter and elementary particles. This was the second generation of quantum physicists, the people that grew up with the theory and learnt about it in university, people who even had textbooks to follow with exercises and solutions in the back. With them came the second wave of confusion. Their generation did not have doubts concerning the validity of the theory, which had passed every single empirical test with flying colours. The issue was that nobody could pin down what kind of universe is ruled by the laws of quantum mechanics! They knew the rules, but could not provide a coherent picture of the world to go with it. To no surprise, once again came famous figures in science telling us that the quest for understanding quantum mechanics was destined for failure, for not even the greatest geniuses could emerge victorious. The most annoying of such claims is this quote by Feynman:

I think I can safely say that nobody understands quantum mechanics

So, the person who won a Nobel Prize for developing quantum electrodynamics and wrote a best-selling series of physics textbooks is saying that nobody understands quantum mechanics? No way! Why did they give him a prize then? Why are people buying his textbooks? What Feynman meant was that there remained some profound foundational questions about quantum mechanics for which nobody had been able to provide satisfactory answers. To him, this meant that the theory was not completely understood. But of course it was understood, he was teaching it to hundreds of students!

Why do we keep quoting Feynman on this? How are we supposed to get people excited about learning quantum mechanics when we tell them from the start that nobody can understand it?

Thankfully, like Bob Dylan said, “the times they are a changin.” Now it’s time for us, the third generation of quantum scientists, to give quantum mechanics the reputation it deserves: that of a beautiful and simple theory that should be understood by as many people as possible. Here at the Institute for Quantum Computing, we are making great efforts to share our research and teach quantum theory to our community. Every year we host around 40 high school students from Canada and the world and teach them the basics of quantum mechanics in the Quantum Cryptography School for Young Students. IQC has also recently started a training program called Teaching Quantum Technology, aimed for teachers who are interested in introducing the ideas behind quantum mechanics and their application to technology in their classrooms. Recently, we even created a video game: Quantum Cats! This is only an example of a worldwide trend to spread our knowledge of quantum mechanics, a movement that is guided by the conviction that Bohr and Feynman were wrong: anyone can understand quantum mechanics.

If you are interested in being one of the growing number of people that have added quantum theory to their database of knowledge, please join me for part 2 of this series, where I will teach you the basics of this most splendid theory. No matter your age, your background or your preferences, I am sure that these are ideas that you can grasp and that you will enjoy learning. I will be expecting you!

 Anyone can understand quantum mechanics


Very good writing. Liked it very much.

Thank you Shihan :)

Very encouraging article, Juan Miguel. I'll be joining you in part 2 (where?, when?)

In the meanwhile I will follow the Quantum Cats.

Vielen Dank Herr Rivas!

Part 2 should be coming out on December 1st in this blog :)

Thanks.  Am a Waterloo math grad, 77141250! (some things you never forget) and bumped into this page after doing some  reading on cryptography, following an article to a link about one of my profs (William Tutte) then seeing IQC which I'm afraid I've been too busy to learn about, but am interested in reading part 2.

We're glad you bumped into our blog Larry! You'll be able to read part 2 on Tuesday, December 1. We always post around noon.


i am ecstatic to read someone else write that anyone can learn quantum mechanics. I give you kudos, my friend!

Thank you!

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