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The sound of quantum

The sound of quantum
Samin Ishtiaq
11 May, 2023

What sound does a quantum computer make? A recent hackathon at our Deltaflow.Control team led to the world’s first (unofficial) QuantumVision Song Competition. 

The purpose of the hackathon was twofold. First, to use a pulse-generating control system to make some music. Our Deltaflow.Control system effectively controls qubits using radio pulses in the 10 to 450 MHz frequency range. During the hackathon, we switched these control pulses to something more melodic, using self-composed and well-known songs to get our control system to “sing”.  

The winner in the “best song” category went to our Quantum Control Engineer Mitch Peaks who used the Deltaflow.Control library to create this: 

The second purpose of the hackathon was to “eat our own dogfood”. We wanted to use our control system like our users would use it, and to come up with improvements to our documentation, the usability of our libraries, quality of examples, etc. In this category, the winner was Anton Buyskikh, our Senior Quantum Scientist: 

The hackathon was a lot of fun – and of course, being Riverlane, involved a free lunch. But it also had a very serious side to it. One of the most challenging requirements in scaling up a quantum computer is guaranteeing the precise alignment between multiple high frequency outputs. The Deltaflow.Control team are obsessed with building useable tools that guarantee the deterministic behaviour of the hardware controlling the qubits, which is an important step towards quantum error correction. 

Most trapped-ion quantum architectures, for example, use pairs of laser beams to execute a quantum gate on a qubit. Each laser beam must be aligned with incredible accuracy – within a few microns, while stabilising each beam’s power, position and phase. The slightest deviation stops the quantum computer from working effectively. And when you scale up to the million-qubit range then millions of lasers must be precisely tuned and aligned. 

The same requirement holds for other quantum architectures like superconducting and neutral atoms: large-scale quantum computers need highly determinate, high-accuracy, high-speed pulse sequences to control their qubits. 

This is where our high-speed, high-accuracy control solution Deltaflow.Control comes in. Deltaflow.Control abstracts and simplifies the configuration and running of a qubit control system, leaving scientists more time to focus on their research. 

To extend the music analogy further, while current qubit control systems are the equivalent of sending a WAV file, we are building a system than sends MIDI files. A WAV file is just a collection of sound samples at a given rate, but a MIDI is a file of directions to a player, telling it when and how to play a given note.  

Using Deltaflow.Control, users define timing-deterministic sequences of operations for which the Control software stack will output the required low-level micro-instructions. Achieving this requires more than just mastery in crafting the hardware boards and FPGA logic, it also requires extremely smart mapping of the application program into low level pulse sequences.

Our Deltaflow.Control team has also developed a compiler that allows precise alignment across multiple boards via latency compensation and multi-pass analysis of the intermediate representations. If a user asks for more than the hardware can do, then the Deltaflow.Control software will raise an informative error at compile time and suggest changes. This means there are no nasty surprises in the lab, which helps reduces a user’s workload, instead of creating the need for extra checks. 

Deltaflow.Control is already being used today by some of the world’s leading academic labs including the University of Wisconsin, Duke University, University of Oxford and University of Innsbruck. Riverlane is also partnering with more than a third of the world’s quantum hardware companies, such as Infleqtion (formerly Cold Quanta), Qolab, Quera, Seeqc, Rigetti and Universal Quantum. 

This work has an impact on quantum error correction. This is because guaranteeing the deterministic behaviour of the control hardware is the first step towards fault tolerant execution.  

It affects the quality of the control sequences, the complexity of the interaction between the different moving parts (calibration, quantum error correction, operation scheduling and more).  

It is probably the hardest feature to “post”-insert in a system and it has ramifications for all aspects of hardware and software design. 

The Deltaflow.Control team understood the importance of deterministic behaviour and designed its solution to generate high accuracy, high speed pulse sequences to control qubits. It has taken less than 12 months from a whiteboard sketch to a software stack that is robust and easy enough that people can even make very precise “music” out of it.  

During the hackathon, one of two approaches was taken. While the musicians amongst the Deltaflow.Control team composed their music from scratch, the computer scientists wrote translators from standard music formats into Deltaflow.Control control scripts. This allows Deltaflow.Control to play *any* music you can find on the internet. (Only from reputable sources, of course!) 

If you work in a quantum lab and want to more effectively control your qubits, then please get in touch with our team at  As you’ve seen, you can also use it to make music 😊 

And if you think you’ve got an idea for next year’s QuantumVision Song Competition, just send a tweet us with your suggestion using the handle @Riverlane_io.  

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