The Quantum Control Stack with Niels Bultink

Why This Episode Matters

Niels Bultink earned his PhD at QuTech under Leonardo DiCarlo, where he performed some of the first real-time feedback experiments on solid-state qubits — the foundational primitive behind quantum error correction. He spun Qblox out of TU Delft in 2018, and has grown it to roughly 140 people serving 150+ customers worldwide, mostly on revenue rather than venture capital, before raising a $26M Series A in 2024.

This conversation matters now because the goalposts for useful quantum computing have moved closer in the last 12 months. Recent estimates suggest breaking RSA may need ~10,000–100,000 qubits, not tens of millions — and at that scale, the control stack is no longer a lab afterthought. It is a strategic supply chain question, which is why the DOE just picked Qblox to manufacture Fermilab's QICK platform domestically. If you care about how quantum computers actually get built — the layer between the qubit and the software — this is the episode for you.

Sponsor

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Go deeper with the blog post.

What We Get Into

• Why the IBM Quantum Experience originally needed a meter of rack equipment per qubit, and what had to change architecturally to scale past that
• How a quantum control stack can be genuinely qubit-agnostic — and where modality differences actually live (mostly in the analog front end, not the digital core)
• Why pre-compiled pulse sequences hit a wall, and how dynamic, adaptive control is a prerequisite for fault tolerance, not a nice-to-have
• The role of Qblox's SYNQ and LINQ protocols in achieving picosecond-level synchronization and low-latency feedback across hundreds of cores
• Why FPGAs are the right substrate today, and why the field will need to move toward ASICs as production volumes grow
• The strategic logic behind manufacturing Fermilab's open-source QICK platform — and how it complements rather than cannibalizes the Qblox Cluster
• What the Quantum Utility Block partnership with QuantWare and Q-CTRL actually delivers, including a full-stack demo built in a weekend at APS March Meeting
• Why Qblox opened a Boston HQ and started U.S. manufacturing in Canton, Massachusetts in 2026, and how geopolitics is reshaping quantum supply chains
• Niels's read on which qubit modalities are gaining ground fastest right now — including a notable jump in spin qubits and neutral atoms
• What's special about the Dutch quantum ecosystem, and why a value-chain culture produced multiple revenue-driven hardware companies

Resources & Links

Guest & Company

• Qblox — Delft-based control stack company at the center of this episode
• Niels Bultink on Google Scholar — Niels's research record from his QuTech years, useful background on his feedback control work
• Qblox North America HQ announcement — Context for the Boston expansion discussed in the episode
• Qblox "Made in America" manufacturing announcement — Background on the Canton, MA manufacturing milestone

Partnerships Discussed

• Fermilab × Qblox QICK partnership announcement — The DOE-backed deal for Qblox to manufacture and distribute QICK
• Quantum Utility Block press release — Joint reference system with QuantWare and Q-CTRL referenced in the episode
• APS 2024 full-stack demo recap — The 48-hour conference-floor build Niels mentions

Foundational Paper

• "Feedback Control of a Solid-State Qubit Using High-Fidelity Projective Measurement" — Ristè, Bultink et al., the 2012 work that grounds Niels's perspective on real-time control

Funding & Market Context

• Qblox Series A announcement — Context for the revenue-first growth story discussed
• The Quantum Insider on the Series A — Independent coverage with quotes from Quantonation

Key Quotes & Insights

• On why the control stack is more than picks and shovels: "Sometimes companies like us are called picks and shovels. It's a nice analogy, but it doesn't hold entirely. The qubits are just the bottom layer of the stack — and all the other layers are also crucial to develop."
• On flexibility as a requirement, not a feature: Pre-compiled, rigid sequences can't support quantum error correction. Adaptive, real-time control flows aren't a performance upgrade — they're "a basic need for this new era of quantum fault tolerance."
• On the moving goalposts for useful quantum computing: A year ago, breaking RSA looked like tens of millions of qubits. Recent estimates put it at 10,000–100,000 — "a factor hundred smaller what we now think we need versus a year ago."
• On the future of FPGAs: FPGAs are the right substrate for today's flexibility, but already at current production volumes, "it makes more sense to put things in chips, in ASICs."
• On the Dutch ecosystem: What sets Delft apart isn't a slogan about ecosystems but a value-chain culture — companies that focus on one layer, work together, and grow on customer revenue rather than venture rounds.

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