How solved is microwave-to-optical transduction, really?

I interviewed Sebastian Hassinger last week, who worked on the IBM Quantum team and later led GTM for AWS Quantum Technologies. Sadly, we ran out of time before I could push on this properly, so I'm bringing it here. His argument was that scaling superconducting qubits past a single dilution refrigerator forces you into transduction, converting the state to a telecom photonic frequency, carrying it over fiber, then converting back in the second fridge. And that none of the currently known conversion methods gets you the fidelity a reliable device needs, with no clear picture of what closing that gap requires. But his framing was that this is a scientific unknown rather than an engineering one, and that the distinction matters because roadmaps are engineering documents projecting deterministic milestones onto problems that aren't deterministic yet. So there are two things I'm curious about. Is transduction actually the binding constraint for superconducting approaches, or is it downstream of something else like fabrication yield or decoder latency? And does modular architecture genuinely require it, or are there routes around it people are taking seriously? Saqib here, I edit Deep Engineering. Asking partly because photonic and modular approaches are underrepresented in our coverage and I'd like to fix that. submitted by /u/DeepEngineeringPackt [link] [comments]