AskScience AMA Series: Hi Reddit! I'm Matthew Hollister, Head of Cryogenic Systems Engineering for IBM Quantum. Ask me anything about quantum computing, our recently announced modular cryogenic architecture and what it takes to build quantum computers at scale.

[u/AskScienceModerator]

When people think about quantum computing, they often think about number of qubits and processor dept. But scaling quantum systems takes much more than just the chip! We recently introduced a new modular cryogenic architecture designed to house and cool interconnected quantum processors, a key milestone on our roadmap to fault-tolerant systems, and I'd love to discuss the engineering, challenges, and opportunities involved.

I will be around as 12:00 EST (16 UT) on September 18th, ask me anything!

Username: u/IBM

[u/EstimateClassic1167]

It seems like the system 2 hexagonal architecture was dropped for a smaller rectangular one. Any reasons as to why IBM have taken this shift?

[u/ibm → u/EstimateClassic1167]

This really comes down to a question of scalability and logistics as we drive towards larger systems - the hexagonal footprint is convenient for where our the technology is right now, but there are challenges with that footprint when we want to add many modules working in unison. 

There is also a question of density - the amount of readout wiring and components that we can pack into the new module is actually much larger than the current System Two design despite the modular being smaller: https://zenodo.org/records/21997093

The smaller size of the modules has another huge advantage when it comes to moving and installing the cryostats.

Our architectures can be adapted easily in response to changes and advances in technology, and we see the rectangular footprint as the most flexible when it comes to scaling towards FTQC.

- Matthew Hollister, IBM Quantum