Katie McCormick
is a postdoctoral scholar at the Department of Physics at the University of Washington. Her science writing has appeared in Scientific American, The Conversation and Massive Science, among others. She lives in Seattle, WA.

Physics has long looked to harmony to explain the beauty of the Universe. But what if dissonance yields better insights?

Quantum physics is weird and counterintuitive. For this reason, the word ‘quantum’ has become shorthand for anything powerful or mystical, whether or not it has anything whatsoever to do with quantum mechanics. As a quantum physicist, I’ve developed a reflexive eyeroll upon hearing the word applied to anything outside of physics. It’s used to describe homeopathy, dishwasher detergents and deodorant.

If I hadn’t first heard of Quantum Music from a well-respected physicist, I would have scoffed the same way I did at the other ridiculous uses of the word. But coming from Klaus Mølmer it was intriguing. In the Quantum Music project, physicists and musicians worked together to unite ‘the mysterious worlds of quantum physics and music for the first time’. They developed a device that attaches to each key of a piano so that, when the pianist plays, the information is piped to a computer and synthesiser, which plays ‘quantum’ tones in addition to the familiar reverberations in the piano.

Among the tones used are those that represent a very quantum object: a Bose-Einstein condensate (BEC). This is a cloud of atoms that have been cooled down to just above absolute zero. At this low temperature, the microscopic quantum properties of the individual particles can all be treated collectively as a single, macroscopic quantum entity. Studying BECs is a way of examining the consequences of quantum mechanics on a larger scale than is typically possible.

One aspect that can be studied with a BEC is quantum acoustics – the behaviour of oscillations and vibrations in the cloud. These same types of vibrations in the air produce the sounds we hear. The quantum properties of the atoms, such as how they interact with one another, determine the frequencies of sound waves that can propagate in the BEC.

The Quantum Music project combined a piano with these quantum sounds to produce strange but beautiful music unlike anything I’d heard before. I thought it was a very nice outreach project. But, apparently, Mølmer hoped for more. In a promotional video from 2016, he expressed his hopes that musicians might be able to give him insights into quantum mechanics:

If you take people who have strong intuition, for example, in waves and wave behaviour, like musicians, will they be able to bring in an extra insight? Can their professional knowledge about waves – the kind of knowledge that a musician has – can that also be used in quantum research?

My eyes might not have rolled, but they certainly narrowed in scepticism. I couldn’t imagine anyone who didn’t have a physics background bringing any sort of useful intuition to quantum mechanics. It was so contrary to our everyday experience, I thought that the only way to grasp the quantum world was to study and grapple with the mathematics that describe it. On top of that, it seemed like the goals of a musician and a physicist are entirely different – perhaps even competing. While a composer works within a framework of music theory to produce something beautiful and interesting, a physicist is interested only in finding the truth of how the world works, regardless of whether that truth is beautiful or not.

But then again, quantum mechanics is largely about waves. And what is music but the combination of waves? While there certainly are quantum mechanical phenomena that are too weird to capture with classic sound waves used in music, many aspects of quantum mechanics arise from one fact: that everything, from light to particles, even to humans, has a particle-like nature and a wave-like nature. For something as large as a human, the length of this wave – the so-called ‘de Broglie wavelength’ – is so small that it’s negligible, so we needn’t worry about superpositions or entanglement of people. But the smaller and colder you get, the longer the de Brogliewavelength becomes, and the more this wave-like nature of the particle plays a role. (This is over-simplifying the problem but, for the sake of this piece, I’ll leave it at that. Philip Ball’s Aeon essay ‘Quantum Common Sense’ is great at explaining how our classical experience arises from quantum rules.)

Perhaps experience combining sound waves into compositions of music does give people deep, intuitive insights into the physics of other wave-related phenomena, including quantum mechanics. Perhaps there is a connection between music and physics in general. Perhaps it’s not a coincidence that so many of the most successful physicists in the past were also musicians.[…]

Continue reading: https://aeon.co/essays/uniting-the-mysterious-worlds-of-quantum-physics-and-music