Making light of quantum machine learning

Emojis, light music, and other applications of quantum neural networks 🔥 🔥 🔥

By Juan Miguel Arrazola, Thomas R. Bromley, Josh Izaac, and Nathan Killoran

At Xanadu, we’re working hard to make quantum computing and quantum machine learning a reality. We’ve recently developed a new light-based quantum neural network scheme which can be used to tackle challenging scientific and technical problems. But after a hard day’s work, sometimes you just want to let loose and get creative.

This blog post will be all about having fun with our new toys. Let’s start with a little “light music”: grab your headphones!

Making music with quantum light

Quantum neural networks can be used to transform simple quantum states into more complex ones. In our recent paper, we trained quantum circuits that could convert laser light into states of a fixed number of photons. By appropriately selecting the brightness and phase of the incoming light, we can generate states of one, two, or three photons. Instead, by inappropriately selecting the brightness and phase of the incoming light, we can generate completely new kinds of quantum states that can interpreted as musical instruments.

Quantum instruments.

How does a quantum state make a musical instrument? The frequency of a wave determines its pitch, i.e., whether it sounds like the note C or the note A. The shape of a sound wave dictates its timbre: the difference between a piano or an electric guitar playing the same note.

Each quantum state of light is characterized by a unique wavefunction whose shape determines the timbre of its associated instrument. We can ‘play’ a quantum state by generating a sound wave built by repeating the shape of the wavefunction at a desired frequency.

Our quantum neural network can therefore be used to discover new instruments: by interpolating between the wavefunctions of known quantum states, we can discover new wavefunctions, and thus, new instruments

We experimented with this idea by choosing different kinds of input laser light and playing the resulting quantum instruments. After a careful selection process, Juan Miguel presents to you his creations: the Heisenbass, Diraclarinet, and Hilbertsichord.