Daniel Faircloth, PhD is an unusual figure in the quantum ecosystem: a computational electromagnetics engineer who actually helped build trapped-ion hardware before pivoting to the software stack the field was missing. He's a co-author on the 2013 New Journal of Physics paper that demonstrated reliable ion transport through a microfabricated X-junction surface-electrode trap at Georgia Tech Research Institute, and he spent the years afterward inside a defense contractor, IERUS Technologies, building the electromagnetic simulation engine that has now spun out as Nullspace.

If you've been following the trapped-ion race — Quantinuum, IonQ, Oxford Ionics, AQT, and the academic groups feeding them — this episode fills in a layer of the story that rarely gets airtime. As the field moves from clever physics demonstrations toward genuinely scaled architectures, the design tools, the file formats, and the iteration loops start to matter as much as the qubits themselves. Listeners interested in quantum engineering, the analog of EDA in semiconductors, or how dual-use defense R&D translates into commercial quantum infrastructure will find a lot to chew on.

What We Get Into

• Why the standard "gapless approximation" for ion trap modeling — treating electrodes as polygons on an infinite metal sheet — breaks down well before you're ready to fabricate.
• How Faircloth's graduate-school question ("can better tools turn a good engineer into a super engineer?") became the design philosophy behind Nullspace ES.
• What turning an X-junction corner actually requires: two-stage optimization across trap geometry and control voltages, so the ion doesn't get heated out of the trap.
• Why general-purpose electrostatic solvers struggle with ion trap problems that demand nanometer ion-height precision and millivolt-level shuttling voltage accuracy.
• The technical leap in Nullspace ES 2025 R1: pairing high-order basis functions with a compression solver to cut memory usage roughly 5× while preserving accuracy.
• The awkward commercial reality of selling neutral simulation infrastructure to companies that are direct competitors with each other.
• The "build vs. buy" tension for hardware startups deciding whether to roll their own solver in Python or adopt a purpose-built commercial tool.
• How the dual-use defense / commercial-quantum positioning shapes Nullspace's roadmap — and where lessons flow in both directions.
• Where the roadmap might lead: multi-physics, tightly integrated workflows that eliminate the CAD-cleanup and file-format-exchange tax engineers pay today.

Resources & Links

Guest & Company

• Daniel Faircloth Bio — Nullspace, Inc. — Background on Daniel's path from GTRI and IERUS to co-founding Nullspace.
• Nullspace, Inc. — Company homepage covering the Nullspace EM and Nullspace ES product suites.
• Inside Nullspace: Rethinking Electromagnetic Simulation with Dr. Daniel Faircloth — A longer-form interview on why Daniel rebuilt EM simulation from scratch.

Product & Technical Resources

• Nullspace ES — Electrostatic Simulation for Quantum Computing — Product page detailing the ion-trap-specific capabilities discussed in the episode.
• Nullspace ES 2025 R1 Tech Brief — The release notes behind the high-order basis functions and 5× memory reduction Daniel describes.
• Precision Ion Trap Modeling and Simulation for Quantum Applications — Webinar featuring Oxford Ionics' Curtis Volin demonstrating Nullspace ES on a surface-electrode trap.

Papers & Background Reading

• Reliable Transport Through a Microfabricated X-Junction Surface-Electrode Ion Trap (NJP, 2013) — The GTRI paper Daniel co-authored, including the corner-turning ion transport work referenced in the episode.
• Daniel Faircloth — ResearchGate profile — Additional EM and ion trap publications from Daniel's GTRI/IERUS years.

Company & Funding Context

• Nullspace Raises $2.5M Seed Round (PR Newswire, Aug 2025) — The seed round led by Fathom Fund with Golden Seeds.
• Nullspace Raises $2.5M — The Quantum Insider — Quantum-sector framing of the dual-use RF/quantum positioning.
• Nullspace Inc. Launches as an Engineering Software Company (PR Newswire, Jun 2023) — The spin-out announcement and origin story.

Key Quotes & Insights

• On the original product question (paraphrase): If you give powerful EM and optimization tools to a well-trained engineer, can you effectively turn them into a "super engineer" and unlock the kind of creativity that textbook parameterizations can't reach? That question became the through-line from Daniel's graduate work to Nullspace.
• On why existing tools fall short (paraphrase): The community was trying to shoehorn ion trap design into solvers that were never built for it — gapless approximations, weak optimizers, and accuracy levels that simply don't hold up when you need nanometer ion heights and millivolt shuttling voltages.
• On corner-turning in an X-junction (Daniel, lightly edited): "If you think of an ion trap as a fancy train track system, the ions are being shuttled around — you need to be able to turn left and turn right as you grow and scale. How do you get the ion to turn but not get heated in that process and lose the ion?"
• On serving competing customers (paraphrase): A rising tide floats all boats. The better the underlying simulation tools, the more sophisticated the architectures every team can attempt — and the more chances the field has of someone breaking through.
• On the long-term vision (Daniel): "Being able to provide all of that in an appropriate fidelity, one-stop shop for the designers. I don't want them to have to go to a bunch of different tools and try to kind of piece together dealing with file format exchange issues."

Related Episodes

• Episode 91 — Hardware-Faithful Digital Twins for Quantum Computing with Izhar Medalsy — A complementary view of simulation infrastructure, focused on superconducting digital twins.
• Episode 17 — The Enchilada: Microfabricated Ion Trap Qubits with Daniel Stick — The Sandia pers...

EeroQ is unusual in two ways. It's the only company in the world commercializing electrons-on-helium qubits, a modality first proposed by Platzman and Dykman in Science in 1999. And it was founded by Nick Farina — a software entrepreneur, not a physicist — who got pulled into the field through a Chicago theater board where he met his future co-founder, then-PhD student Johannes Pollanen.

This conversation matters now because EeroQ has had an unusually productive twelve months: a Physical Review X paper demonstrating single-electron control above 1 Kelvin, a January 2026 result on controlling up to a million electrons with fewer than 50 control lines, and — published in Nature Physics on June 15, 2026 — the first demonstration of strong coupling between a microwave photon and a single electron on helium, the cavity-QED readout-and-control link the platform depends on. If you're trying to understand which "second-tier" modalities deserve serious attention — and how a small, capital-light team in Chicago is thinking about scale-first hardware design — this is a useful listen.

Sponsor

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It's time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power.

Learn more about the Cisco Universal Quantum Switch at Outshift.com.

Go deeper with the blog post The switch that quantum networking has been waiting for.

What We Get Into

• How a Chicago theater board led to one of the most unique qubit companies in the field
• Why electrons-on-helium failed in the early 2000s and why circuit QED, dry fridges, and CMOS now make it viable
• The physical picture: a thin superfluid helium film coating a CMOS chip, with electrons trapped a few nanometers above the surface by their own image charge
• Why EeroQ pivoted from motional states to spin qubits after Steve Lyon (Princeton) joined as CTO — and the predicted 10+ second coherence times that come with it
• The "build a quantum computer in reverse" philosophy: starting from a million-qubit architecture and working back toward two-qubit gates
• How the "Wonder Lake" chip controls 2,432 future qubit sites today, and why that's an engineering milestone rather than a qubit count
• Honest framing of where EeroQ actually is: no two-qubit gate demonstrated yet, with a tape-out target of ~10,000 qubits by late 2028
• Why dipole-dipole gates come first and exchange gates come later, borrowing from the spin qubit playbook
• The case that scaling — not qubit quality — has been the field's slowest-moving problem over the last decade

Resources & Links

Guest & Company

• EeroQ — Company site for the only commercial electron-on-helium quantum hardware effort.
• EeroQ Publications — Peer-reviewed papers and preprints from the team.
• Building a Quantum Computer in Reverse (EeroQ Blog, July 2023) — Farina's own articulation of the scale-first design philosophy discussed in the episode.

Key Papers

• Koolstra, Glen, Beysengulov et al., "Strong coupling of a microwave photon to an electron on helium," Nature Physics, June 2026 — First demonstration of strong coupling between a microwave photon and the quantized motional state of a single electron on helium, including observation of vacuum Rabi splitting — establishing the cavity-QED readout link at the heart of EeroQ's architecture. This result was under embargo when the episode was recorded.
• Castoria et al., "Sensing and Control of Single Trapped Electrons Above 1 Kelvin," Physical Review X (2025) — The 1 K result Nick references; demonstrates charge sensing but not yet coherent spin manipulation.
• Koolstra et al., "High-impedance Resonators for Strong Coupling to an Electron on Helium," Physical Review Applied (Feb 2025) — The resonator architecture underlying EeroQ's cQED control approach.
• Electron-on-helium qubit (Wikipedia) — Useful overview including the original 1999 Platzman & Dykman Science proposal and Steve Lyon's 2006 spin-qubit paper in Physical Review A.

Press & Context

• EeroQ Makes World-First Breakthrough in Electron Qubits Floating on Helium (EeroQ, June 2026) — Company announcement of the Nature Physics strong-coupling result.
• EeroQ Solves the "Wire Problem" (PRNewswire, Jan 2026) — The million-electrons / fewer-than-50-wires result Nick cites.
• Individual electrons trapped and controlled above 1 K (Phys.org) — Independent coverage of the PRX paper.
• EeroQ Achieves Tape-Out of "Wonder Lake" Chip (The Quantum Insider, July 2023) — Background on the 2,432-site CMOS chip discussed in the episode.

Ecosystem

• Chicago Quantum Exchange — The regional consortium EeroQ benefits from.
• Illinois Quantum and Microelectronics Park — The state-backed quantum park anchored in Chicago.

Key Quotes & Insights

• On the contrarian thesis: "Scaling is actually the hardest part of building a quantum computer." Nick argues the field has made real strides on gate fidelity, error correction, and algorithms over the last decade — but not nearly enough on the path to hundreds of thousands or millions of qubits.
• On building in reverse: Rather than starting from a two-qubit gate and "hoping and praying to find ways to scale," EeroQ started by asking what a million-qubit processor would have to look like — which forced the choice of CMOS as the only manufacturing technology humanity has ever used to build features at that scale.
• On honest status: "We d...

Why This Episode Matters

Sabrina Maniscalco is one of the few people in quantum who has lived the full arc: two decades of academic work on open quantum systems and non-Markovian noise at Palermo, Turku, Edinburgh, and Helsinki, followed by founding Algorithmiq with three of her former researchers after an early Qiskit Camp. That trajectory matters now because Algorithmiq just had a landmark stretch — sole winner of the $2M Wellcome Leap Q4Bio prize for a quantum-enabled cancer drug discovery workflow, an €18M Series B, a global HQ move to Milan, and its Tensor Network Error Mitigation (TEM) function landing in IBM's Qiskit Functions catalog.

If you're trying to make sense of where quantum software actually creates value before fault tolerance arrives — and what a credible "trajectory to advantage" looks like when paired with real clients in life sciences — this is a grounded, technically specific conversation with someone building it.

EPISODE SPONSOR

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It's time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power.

Learn more about the Cisco Universal Quantum Switch at Outshift.com.

Go deeper with the blog post The switch that quantum networking has been waiting for.

What We Get Into

• Why a background in open quantum systems and non-Markovian noise turned out to be unusually well-suited to running algorithms on noisy near-term hardware
• The actual science behind the Q4Bio winning workflow: simulating excited-state dynamics of a photosensitizer drug already in Phase II clinical trials, on up to 100 qubits
• How quantum-boosted DMRG works — and why it gives you a built-in benchmark against the best classical method via the bond dimension
• The tradeoff Sabrina would and wouldn't make between more qubits and lower noise, and why neutral atoms' slower sampling rates matter for chemistry
• Why even fault-tolerant algorithms like quantum phase estimation still depend on getting state initialization and measurement right
• Algorithmiq's two-product structure: the Digital Quantum Interface (hardware-agnostic infrastructure) and the life sciences application framework
• How methods built for chemistry are now opening doors into optimization and GenAI — and why that direction emerged from the work, not from a strategy deck
• What the move from Helsinki to Milan signals about the European quantum ecosystem and Algorithmiq's commercial scale-up
• How an active learning pipeline is already proposing novel drug variants for synthesis in Prof. Sherri McFarland's lab

Resources & Links

Guest & Company

• Algorithmiq — The company Sabrina co-founded with Guillermo García-Pérez, Matteo Rossi, and Boris Sokolov; quantum software for life sciences and chemistry.
• Sabrina Maniscalco — University of Helsinki Research Portal — Publication record covering open quantum systems, non-Markovian dynamics, and quantum information.
• Sabrina Maniscalco — AI for Good Bio — Consolidated bio covering academic roles and advisory positions, including IQOQI Austria and CERN's Quantum Technology Initiative.

The Q4Bio Win

• Algorithmiq Wins $2M Wellcome Leap Q4Bio Prize — Company announcement detailing the photodynamic therapy workflow.
• Wellcome Leap — Q4Bio Prize Announcement — Funder's perspective on finalists and criteria.
• IBM Quantum Blog — Q4Bio Finalists — IBM's account of the workflow and quantum-classical integration.

Funding & HQ Move

• Tech.eu — Algorithmiq's €18M Series B and Milan move — Coverage of Italy's largest quantum VC round to date.
• Quantum Computing Report — Algorithmiq Relocates to Milan — Strategic context including the Q4Bio win and IBM partnership.
• EU-Startups coverage — Investor lineup and Italy's National Quantum Strategy framing.

Quantum Advantage & Tooling

• IBM Quantum Blog — The Dawn of Quantum Advantage — Includes Algorithmiq's TEM (Tensor Network Error Mitigation) function in the Qiskit Functions catalog.
• Algorithmiq & IBM Quantum Advantage Tracker — The heterogeneous materials experiment Algorithmiq and IBM put forward as a community benchmark.
• Silicon Republic interview with Sabrina — Useful prior context on her philosophy of using quantum to simulate quantum systems.

Key Quotes & Insights

• On the foundation of the company's approach: "We learned very early what we thought were the bottlenecks of quantum computers — what you really need to worry about if you want to implement computation at scale." A direct line from Qiskit Camp Vermont to Algorithmiq's product strategy.
• On Q4Bio, in Sabrina's words: "This molecule is already in Phase II clinical trial. So it's not hydrogen. It's a real molecule." A useful counter to the common critique that quantum chemistry demos still live in toy-model land.
• On quantum-boosted DMRG (insight): In the worst case, the method matches the best classical technique; in the better case, it outperforms it — and the bond dimension tells you which regime you're in. Built-in benchmarking against the classical baseline.
• On the hardware tradeoff: Asked whether she'd prefer 100 higher-fidelity qubits or 200 noisier ones, Sabrina's answer is "it depends" — and the explanation about why neutral atoms' lower sampling rates limit chemistry use cases is one of the more concrete things you'll hear on platform tradeoffs.
• On strategy (insight): New verticals at Algorithmiq are ...

Why This Episode Matters

Firgun Ventures launched in late 2025 with a $70M first close anchored by the Qatar Investment Authority and a mandate that doesn't exist anywhere else in the market: lead Series A and B rounds in quantum scale-ups globally. Kris Naudts is a neuroscientist and former Culture Trip founder whose path to quantum runs through a near-fatal medical misdiagnosis. Zeynep Koruturk spent over a decade building the Goldman Sachs Tech Initiative and meeting more than a thousand founders. Both were early angels in what became Quantinuum.

If you're trying to understand how quantum companies actually get financed between the lab and the IPO window — or why a specialist fund needed to exist at all — this conversation is one of the clearest views available. It's also a useful frame for founders thinking about what an informed institutional investor actually does in a round.

Sponsor

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It's time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power.

Learn more about the Cisco Universal Quantum Switch at Outshift.com.

Go deeper with the blog post The switch that quantum networking has been waiting for.

What We Get Into

• Why Kris's ALS misdiagnosis became the conviction event that pulled him from media entrepreneurship into quantum investing
• How Zeynep's decade at Goldman Sachs Tech Initiative shaped her pattern-matching for deep tech, and where that pattern-matching breaks down in quantum
• The structural reason Series A/B is the real bottleneck in quantum financing — and why precede and seed capital is no longer the gap people assume it is
• How Firgun underwrites engineering and execution risk after the scientific risk is largely retired
• Why a quantum-specialist fund unlocks soft commitments from larger institutions that otherwise stay on the sidelines
• The role of Firgun's "scientific co-founder" Professor Mete Atatüre and the need for sub-specialist diligence across modalities
• How Firgun thinks about portfolio construction across silicon-spin/photonic (Photonic Inc.), silicon CMOS (Quantum Motion), and other architectures without picking a qubit winner
• Why a truly global mandate is a feature, not a focus problem, given how concentrated quantum talent is in roughly a dozen ecosystems
• How sovereign capital, US equity-stake announcements, and geopolitical fragmentation are starting to reshape who can invest in what
• Why the binary "fault-tolerant or bust" framing of quantum investing misses the gradient of capability that drives near-term value

Resources & Links

Guest & Firm

• Firgun Ventures — The fund's homepage, with the team and "Time to Talk Quantum" podcast featuring the founders' own framing of the market.
• Firgun Ventures on Crunchbase — Confirms London HQ, global mandate, and Series A/B focus.

Fund Launch & Thesis

• Firgun Ventures Launches $250M VC Fund to Invest in Quantum — The Quantum Insider — Launch details, QIA anchor commitment, and founder backgrounds.
• Firgun Ventures Launches With $70M for Quantum Tech Innovation — TechFundingNews — Deeper breakdown of the LP roster and market rationale.
• Firgun Ventures: Scaling Quantum Beyond the Early Stages — Future of Computing — Extended interview with Kris and Zeynep on the Series A/B bottleneck.

Portfolio Companies Mentioned

• Firgun Invests in Photonic Inc. — The Quantum Insider — Firgun's first portfolio investment in DARPA-validated Photonic Inc.
• Photonic Inc.'s World-First Quantum Teleportation — QC Report — Technical context on the "Entanglement First" silicon-spin/photonic architecture.
• Photonic Inc. Closes $200M+ Round — The Quantum Insider — Final close at a $2B valuation.
• Quantum Motion Raises $160M Series C — The Quantum Insider — Firgun's first European investment in silicon CMOS quantum computing.
• Quantum Motion's Silicon CMOS Approach — Technologies.org — Technical analysis of the CMOS scalability thesis.

Key Quotes & Insights

• Kris on the conviction event: "If you're expecting to die and then you're told you're going to live, you have to rethink it yet again… You can go in the direction of enjoy every day, or you can go in the direction of let's try to do something meaningful with whatever time I have left."
• Zeynep on the real bottleneck: Pre-seed and seed capital in quantum is no longer the gap — the A and B rounds are. Roughly 40% of companies in the space need that bridge to unlock larger institutional capital, and almost no one is set up to lead it.
• Kris on diligence limits: No one person can underwrite the full quantum stack. Firgun pairs a "scientific co-founder" with sub-specialists for each modality, because in quantum "no propositions sound stupid" — and that's exactly the problem.
• Zeynep on the asymmetric bet: Quantum is one of the few areas where geopolitical reality creates a floor under the downside. The West can't afford to lose, which means funding will be there long enough for the right companies to mature.
• Kris on willing the timeline: "You cannot will it into being. The space will evolve at the pace it is set to evolve with the capital and the talent in it." A useful corrective for anyone pitching a five-year cure-for-Parkinson's roadmap.

Related Episodes

Why This Episode Matters

Yuval has a rare profile in the quantum industry: an M.Sc. in physics from Tel Aviv University, an MBA from Kellogg, two decades as a CEO and CMO in deep tech before quantum, and now the commercial lead at QuEra — the company whose neutral-atom architecture is colocated with NVIDIA H100s inside Japan's ABCI-Q supercomputer and just demonstrated 96 logical qubits from 448 physical atoms in Nature. He also hosts The Superposition Guy's Podcast and has just published Quantum Bits, a comic-book guide to quantum computing.

This is a crossover conversation — Sebastian's book A New Quantum Era came out the same week — so the episode reads as two practitioners comparing their explanatory strategies, their reading of the modality race, and their honest forecasts for when a quantum computer becomes genuinely non-simulatable. If you want a candid look at how the commercial side of quantum thinks about hardware timelines, error-correction overhead, and the work of translating physics into procurement, this is the episode.

Sponsor

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It's time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power.

Learn more about the Cisco Universal Quantum Switch at Outshift.com.

Go deeper with the blog post The switch that quantum networking has been waiting for.

What We Get Into

• Why Vladan Vuletić's confidence horizon for neutral atoms expanded from 5 years to 10 years in a single 18-month window — and what changed
• The honest case for neutral atoms when wall-clock speed is the obvious weakness: parallelism, algorithmic fault tolerance, and a 2:1 physical-to-logical ratio for quantum memory
• Why "time to solution" — not gate speed — is the metric Yuval thinks the industry should be arguing about
• How Shor's algorithm went from requiring a million qubits to roughly 30,000, and what that compression means for cryptographically relevant timelines
• The craft problem of explaining quantum without saying "zero and one at the same time" — and why both Yuval and Sebastian refused to use it
• What it took to make a quantum comic funny in German (the German is perfect, the joke is not)
• Sebastian's read on the modality race: neutral atoms short-term, superconducting mid-term, spin and photonics long-term — and Yuval's pushback
• Why Yuval thinks Sebastian's five-year forecast for a non-simulatable machine is pessimistic
• The shift inside QuEra from "95% science, 5% everything else" to a company that has to ship serviceable systems and uptime
• How podcasting becomes a business development tool once the microphone is off

Resources & Links

Guest Links

• The Superposition Guy's Podcast — Yuval's interview show with quantum CEOs and technical leaders across computing, sensing, and communications.
• Quantum Bits Comics — Yuval's comic-book guide to quantum computing, including custom editions and multilingual versions.
• QuEra Computing — The neutral-atom quantum computing company where Yuval serves as Chief Commercial Officer.
• Yuval's published writing — Aggregated Forbes, HPCwire, and Built In bylines on quantum ROI, workforce, and commercialization.

Papers & Articles

• QuEra and collaborators on Algorithmic Fault Tolerance (Nature, 2025) — The paper behind the claim that syndrome measurements can happen per algorithmic block rather than per operation.
• HPCwire coverage of the AFT result — Independent take on the 10–100x runtime overhead reduction.
• IEEE Spectrum on neutral-atom quantum computing in 2026 — Context for the AIST Gemini deployment and Yuval's time-to-solution argument.
• 2026 Quantum Readiness Report, Part 2 — The survey of 291 stakeholders behind Yuval's "show-me phase" framing of the market.

Books

• A New Quantum Era by Sebastian Hassinger — Sebastian's outsider's introduction to quantum computing, referenced throughout the conversation.
• Quantum Bits: A Comic Book Guide to Quantum Computing by Yuval Boger — Yuval's illustrated explainer, with a glossary covering terms from superposition to QLDPC codes.

Background Reading Mentioned

• The Soul of a New Machine by Tracy Kidder — Sebastian's inspiration for the working title of his next book.

Key Quotes & Insights

• On the magic of neutral atoms: "We've got this rubidium atoms, we hold them in place using tiny lasers, they're four microns apart, we shoot lasers, and then we take a photograph and see how they're doing. It's science fiction until it isn't."
• On the modality timeline (Yuval, paraphrasing Vladan Vuletić): Eighteen months ago Vladan was confident about neutral atoms for the next five years. Six months ago, after recent results, that confidence horizon stretched to ten.
• On what actually matters: "Obviously what matters is time to solution and not clock speed." Yuval's core rebuttal to the standard critique that neutral-atom gates are slow.
• On the error-correction compression: A recent Harvard result showed the physical-to-logical qubit ratio for quantum memory dropping toward roughly 2:1 — not the thousand-to-one figure that dominates most public discourse.
• On the takeaway from his book (Yuval): "Quantum is magical, but it's not magic."

Related Episodes

• Episode 18 — Neutral atom arrays with Alex Keesling of QuEra Computing — Sebastian's earlier conversation with QuEra's CEO on the foundational technology.

Fault Tolerance for Quantum Inputs and Outputs with Matthias Christandl

Why This Episode Matters

Most discussions of fault tolerance quietly assume a classical-in, classical-out picture: you feed in bits, the noisy quantum machine does its work, and a stable classical answer comes out the other side. Christandl — a mathematically trained quantum information theorist who also leads a Novo Nordisk Foundation–funded life sciences center — argues that this framing is too narrow for the era we are actually entering, where multi-core processors, networked QPUs, and quantum communication links all need to exchange quantum information between noisy machines.

If you care about how quantum networks, distributed quantum computers, and quantum simulation workflows for chemistry and biology actually get built, this episode lays out a foundational way of thinking about the problem and connects it directly to current hardware and algorithm co-design.

Sponsor

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It’s time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power. Learn more about the Cisco Universal Quantum Switch at Outshift.com.

Go deeper with the blog post.

What We Get Into

• Why the fault tolerance theorem as usually stated leaves out the case that matters most for networking: quantum inputs and quantum outputs.
• How Christandl's group shows you can still prepare arbitrarily complex quantum states on a noisy machine, paying only one final layer of physical noise rather than collapsing the whole computation.
• What this means for restoring meaning to quantum channel capacity results in the presence of noisy encoders and decoders.
• Why distributed quantum computing — multi-core QPUs talking to each other in quantum, not classical, information — is the natural setting for this work.
• How recent quantum LDPC code work fits in, and why the team is now focused on making encoders and decoders more space-efficient.
• Christandl's debate with Gil Kalai: which skeptical assumptions are worth taking seriously, and which he thinks the fault tolerance machinery is robust against.
• The Quantum for Life workflow: zooming in on the quantum-relevant region of a protein–ligand interaction, running a small quantum simulation, and feeding the result into a classical machine-learning pipeline that needs many such small computations.
• Why "co-design" has replaced "bridging the gap" as the right metaphor for where quantum hardware and quantum software meet.
• How quantum sensing — for example, magnetic-field sensing with atomic clouds — could one day deliver genuine quantum inputs into a fault-tolerant quantum computer.

Resources & Links

Guest Links

• Matthias Christandl — University of Copenhagen Research Portal — Official institutional profile with publications and affiliations.
• Quantum for Life Center — University of Copenhagen — The Novo Nordisk Foundation–funded center Christandl leads, focused on quantum algorithms for the life sciences.
• UCPH Quantum Hub launch — The cross-faculty quantum community Christandl helped found at the University of Copenhagen.
• Christandl appointed 2024 Turing Chair — CWI/QuSoft — Background on his honorary visiting chair at QuSoft and CWI in Amsterdam.

Papers & Articles

• Fault-Tolerant Coding for Quantum Communication (arXiv:2009.07161) — The foundational paper (IEEE TIT 2024, with Müller-Hermes) that motivates the episode: channel coding when the encoder and decoder circuits themselves are noisy.
• Fundamental Limit on the Power of Entanglement Assistance in Quantum Communication (arXiv:2408.17290) — Christandl and collaborators settle a 2002 conjecture of Bennett et al. on entanglement-assisted capacity (PRL 2025).
• Asymptotic tensor rank is characterized by polynomials (arXiv:2411.15789) — STOC 2025 result connecting tensor theory to the matrix multiplication exponent.
• How to Use Quantum Computers for Biomolecular Free Energies (2026)
• More Quantum Chemistry with Fewer Qubits — Physical Review Research (2024) — The Quantum for Life paper underlying the protein–ligand workflow discussed in the episode.
• A Cornerstone of Entanglement Theory Restored — Nature Physics (2025) — Christandl's News & Views on the re-proof of the generalized quantum Stein's lemma.
• Quantum Duel: Matthias Christandl x Gil Kalai 

Key Quotes & Insights

• On reframing fault tolerance: Christandl argues that the fault tolerance theorem, as usually stated, assumes classical inputs and outputs — but the most important near-term use cases, from networked QPUs to multi-core processors, need quantum inputs and quantum outputs.
• On the unavoidable final layer of noise: "There will always be a final layer of noise being applied" when a noisy machine prepares a quantum state — and that single layer, not the whole computation, is the real price you pay.
• On the new metaphor: "A few years back, I would have told you the really important thing is bridging the gap between the hardware and the software. Now it's not anymore about bridging the gap. It's about working together."
• On Kalai's skepticism: Christandl finds the debate clarifying rather than threatening — the fault tolerance techniques look robust to the noise-model perturbations skeptics raise, and the engineering question is which code, not whether codes work at all.
• On what quantum advantage in life sciences might actually look like: Not one heroic simulation, but many small, exact quantum computations feeding training data into a much larger classical machine-learning workflow that predicts protein–ligand interactions.

Related Episodes

Philosophy of Physics Meets Quantum Engineering with Elise Crull

Why This Episode Matters

Elise Crull is Associate Professor of Philosophy at CCNY and the CUNY Graduate Center, co-author with Guido Bacciagaluppi of The Einstein Paradox (Cambridge, 2024), and was named a Fellow of the American Physical Society in 2025 for her archival work recovering voices like Grete Hermann from the foundations of quantum mechanics. She was also one of the speakers on Helgoland in June 2025 for the centenary of quantum mechanics — opening, as Sebastian notes, by thanking the organizers for the courage to invite a philosopher.

This conversation matters because the truce between physicists and philosophers of physics is over. Quantum computing has turned interpretive questions — what counts as entanglement, what decoherence really is, whether causal order can be put in superposition — into engineering questions with budget consequences. If you build, fund, or write about quantum hardware, this episode will sharpen how you hear the words being used around you.

Sponsor

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It’s time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power. Learn more about the Cisco Universal Quantum Switch at Outshift.com.

Go deeper with the blog post.

What We Get Into

• Why "decoherence" and "noise" are not interchangeable, and why error correction strategy depends on telling them apart
• The six-plus working definitions of entanglement currently circulating in physics — and why "classical entanglement" makes a philosopher's eye twitch
• What Einstein actually objected to in EPR (hint: it wasn't really determinism), drawn from Schrödinger's "Einstein-Paradoxon" correspondence folder
• Indefinite causal ordering: whether the experimental speedups reflect genuinely acausal physics or our stubbornly classical definitions of "cause" and "signal"
• How monogamy of entanglement is only monogamous with respect to a single degree of freedom — and why that nuance is already being exploited in entanglement harvesting
• Why "it's just a tool" is the most insidious thing an engineer can say about quantum or AI technology
• How the standard heroic-origin story of quantum mechanics structurally erased experimentalists — many of them women like Hertha Sponer — and what that pattern predicts about quantum computing's own emerging origin story
• What Grete Hermann did to von Neumann's impossibility proof forty years before anyone listened
• Why Crull thinks the next physical theory, whatever succeeds quantum field theory, is likely to be stranger, not tamer

Resources & Links

Guest Links

• Elise Crull — CCNY Faculty Profile — Her institutional home, with current research interests and talks.
• Elise Crull — CUNY Graduate Center Profile — Full publications list including forthcoming work.
• Elise Crull — Academia.edu — Preprint archive, including her 2024 Leggett–Garg/Feyerabend paper and earlier decoherence work.

Books & Papers

• The Einstein Paradox (Bacciagaluppi & Crull, Cambridge UP, 2024) — The archival reconstruction of the debate EPR unleashed; the centerpiece of the conversation.
• Ryckman's BJPS review of The Einstein Paradox (2025) — A scholarly assessment of what the book changes about how we read 1935.
• "Realism with Quantum Faces: The Leggett–Garg Inequalities as a Case Study for Feyerabend's Views" (Crull, 2024) — Her most recent standalone article on macroscopic realism.
• "Physics Scratches a Philosopher's Itch" — APS Physics (2022) — A feature on her work on indefinite causal ordering and causation.

Helgoland & History

• Physics World: Helgoland 2025 — the Inside Story — Post-event report on the centenary where Sebastian and Elise first met.
• AIP: "What Happened on Helgoland" — Historiographical pushback on the Heisenberg origin myth.
• AIP: Crull on Hertha Sponer and the path to wave/particle duality (2026) — Her most recent piece on how standard histories minimize experimentalists.

For General Audiences

• StarTalk: "The Philosophy of Physics with Elise Crull" (June 2025) — Crull with Neil deGrasse Tyson, kicking off the Einstein Paradox promotion cycle.
• StarTalk: "How Quantum Physics Complicates Objective Truth" (April 2026) — A complementary, more recent treatment of the same themes.

Key Quotes & Insights

• On what philosophy is for: "Every aspect of science we do requires interpretation, because the world isn't just out there. We make choices about how to encounter it."
• On decoherence vs. noise: Crull notes the question physicists at Duke recently raised with her — how do you tell the difference between decoherence and noise? — and stresses that one is something you shield against, the other is something else entirely. Error correction strategy depends on the distinction.
• On what really bothered Einstein: Despite the popular story, "He wasn't as concerned about determinism as you would think." What Einstein wanted was a theory whose mathematics had a one-to-one mapping to individual systems with their own states — and entanglement broke that.
• On indefinite causal order: Experimentalists often equate causation with signaling constraints, but "those are very different things." The superposition-of-causal-orders results may reveal less about causation than about the fact that temporal ordering itself remains defined in irreducibly classical ways.

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

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It’s time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power.
Learn more about the Cisco Universal Quantum Switch at Outshift.com.

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.

Stay in the Ecosystem

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Hardware-Faithful Digital Twins for Quantum Computing with Izhar Medalsy

Izhar Medalsy is not a career qubit theorist. His path runs from a physical chemistry PhD and an ETH Zurich postdoc in atomic force microscopy and ternary nanoscale logic, through productizing scientific instruments at Bruker, through building one of the fastest resin 3D printers on the market, into co-founding Quantum Elements in 2023 with Daniel Lidar (USC) and Amir Yacoby (Harvard). That arc — nanoscale measurement scientist turned deep-tech operator — shapes how he thinks about the simulation gap in quantum computing.

The conversation lands at a specific moment. In April 2026, Quantum Elements published a joint result with AWS, USC, and Harvard simulating a distance-7 rotated surface code with 97 physical qubits using full quantum master equations on AWS HPC7a, and announced a deeper collaboration with Rigetti Computing on next-generation superconducting processors. If you care about how error correction strategies, decoders, and pulse-level controls actually get developed before they ever touch hardware, this episode is for you.

EPISODE SPONSOR

This episode is brought to you by Outshift, Cisco's incubation engine. The need for computational power is rapidly increasing in every sector. From drug discovery to material innovation to complex financial modeling, classical systems are reaching their absolute limits. It’s time for a paradigm shift. The answer is a scalable quantum network, built on open standards and vendor-agnostic architecture. By uniting distributed quantum devices, you unlock limitless computational power.

Learn more about the Cisco Universal Quantum Switch at Outshift.com
Go deeper with the blog post The switch that quantum networking has been waiting for

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What We Get Into

• Why generic noise models fall short and what "hardware-faithful" actually means when two nominally identical QPUs have different noise fingerprints
• How Quantum Elements scaled open-system master-equation simulation from a brute-force ceiling around 16 qubits to 97 qubits using stochastic compression on top of Quantum Monte Carlo
• The compute reality of the distance-7 surface code run on AWS HPC7a — only 96 vCPUs and a few hundred gigabytes of memory, not the thousands of vCPUs they initially feared
• Why decoders are the invisible bottleneck in fault tolerance, and where AI-trained decoders fed by digital twin data could plausibly run inside the real-time quantum-classical loop
• Extending error suppression from physical qubits up to logical qubits — the IBM Eagle work where digital-twin-guided strategies reportedly took entangled logical qubit fidelity from 43% to 95%
• How the same digital twin approach extends to neutral atoms (live today) and ion traps (on the roadmap)
• What Rigetti gets out of the partnership, what it means to have Chad Rigetti on the board, and how Constellation fits alongside real hardware time
• Izhar's "wooden models in the air tunnel" critique of how the quantum industry currently iterates — and what a parallel virtual development track buys you

Resources & Links

Guest & Company

• Izhar Medalsy — Quantum Elements team page — Background and role at Quantum Elements.
• Izhar Medalsy on LinkedIn — Full career arc from ETH biophysics through 3D printing to quantum.
• Quantum Elements — Constellation platform, where listeners can build their own virtual QPU and run circuits, error suppression, and QEC experiments.

Papers & Articles

• AWS Quantum Computing Blog: Decoding realistic QEC syndrome with Quantum Elements digital twins — Primary technical reference for the 97-qubit distance-7 result discussed in the episode.
• The Next Platform: How HPC and AI Digital Twins Accelerate Quantum Error Correction (Apr 17, 2026) — Independent reporting on the AWS/USC/Harvard simulation.
• The Quantum Insider: Quantum Elements & Rigetti collaboration (Apr 21, 2026) — Details on the partnership Izhar describes.
• Guest post: Quantum Digital Twins — The Missing Acceleration Layer — Izhar's own framing of the thesis.
• The Next Platform: Startup Profile of Quantum Elements (Jan 2026) — Background on the company.
• arXiv 2603.14607 — Calibration-Based Digital Twins for IBM Quantum Hardware — Useful independent context on the limits and promise of calibration-based twins.

Key Quotes & Insights

• "Sometimes when I look at the quantum industry, there are instances where you think, well, it's almost like building the next fighter jet with wooden models in the air tunnel." — Izhar's framing for why the field needs a real simulation layer.
• On hardware awareness: each modality, each QPU, sometimes each calibration cycle has its own pulses, its own noise processes, and its own failure modes. You cannot build the control stack without modeling where you are starting from and where you are trying to get to.
• Insight: The brute-force ceiling for open-system master-equation simulation is roughly 16 qubits. Stochastic compression layered on Quantum Monte Carlo is what let Quantum Elements reach distance-7 surface code at 97 qubits — exploiting sparsity rather than enumerating the full state space.
• On logical qubits: "We cannot assume that logical qubits will be noise-free." Error suppression strategies developed at the physical level need to be re-derived at the logical level, and digital twins are how you train and test those strategies before hardware.
• Insight: The most interesting downstream story may not be simulation itself but AI decoders trained on digital-twin-generated data — small enough to run at the edge, fast enough to live inside the real-time quantum-classical loop.

Related Episodes

• Episode 52 — Quantum noise with Daniel Lidar — Quantum Elements' co-founder and CSO on the noise suppression and error correction foundat...

Are We Computing Quantum in the Wrong Base? with Ivan Deutsch

Ivan Deutsch is Distinguished Regents' Professor of Physics and Astronomy at the University of New Mexico and the founding director of CQuIC, the Center for Quantum Information and Control. Along with his longtime collaborator Poul Jessen, Ivan helped lay the theoretical foundations for neutral-atom quantum computing in the 1990s: trapping individual atoms in optical lattices, cooling them to near absolute zero, and shuttling them in parallel to perform quantum logic. The companies commercializing those ideas today — QuEra, Pasqal, Atom Computing, Infleqtion, and the newly announced Aurora out of Caltech — are building on architectural concepts that trace directly to his group's early papers. His 9,600+ citations across quantum information, atomic physics, and quantum control place him among the most-cited theorists in the field.

The reason to talk to Ivan now is that he has been making a quietly heterodox argument: every one of those commercial platforms encodes information in two energy levels of an atom that has ten or sixteen, and Ivan thinks the field should be asking whether that's the right choice — not for information density, which is only a logarithmic gain, but for fault tolerance. This conversation goes deep on qudits, spin cat codes, and the co-design philosophy that has shaped Ivan's career at the interface between theory and experiment, ions and neutral atoms, and academia and industry. If you are following neutral-atom hardware, fault-tolerant quantum error correction, or the emergence of regional quantum ecosystems, this episode is essential.

What You'll Learn

• Why neutral atoms were the "underdog cousins" of trapped ions — and the precise trade-off at the heart of a 30-year rivalry: ions are great and terrible because they're charged; neutral atoms are great and terrible because they're neutral
• What the original neutral-atom quantum computing paper actually got right: the parallel atom-movement architecture now central to QuEra, Atom Computing, and Infleqtion's roadmaps was already there — even if the Rydberg blockade's full power wasn't appreciated until later
• What qudits are and why fault tolerance, not information density, is the compelling argument: the information gain from base-2 to base-10 is only logarithmic, but co-designing error-correcting codes with the physical structure of the hardware may be transformative
• How spin cat codes work: using the extra energy levels inside a single atom for error redundancy, directly analogous to bosonic cat codes in microwave cavities, with fault-tolerant thresholds that may surpass standard qubit surface codes
• Why biased error correction matters: real physical errors in neutral atoms aren't arbitrary, and codes designed around the dominant error channels — including leakage and erasure — can dramatically outperform worst-case generic schemes
• How leakage becomes an asset: when population escapes the qubit subspace into other levels, detecting that escape converts it from an unknown error into an erasure error, which is far easier to correct
• Why working at interfaces is where the creative work happens: Ivan's career has been built at the boundary between theory and experiment, between ion-trap and neutral-atom communities, and now between research and industry
• How New Mexico became a quantum hub: the founding of QNM-I, the partnership with Colorado, and the Elevate Quantum Tech Hub — turning decades of national-lab and university strength into an actual industrial ecosystem

Resources & Links

Guest Links

• Ivan Deutsch — CQuIC Faculty Page — Research profile and publication list at the Center for Quantum Information and Control at UNM
• Google Scholar Profile — 9,600+ citations across quantum information, atomic physics, quantum optics, and quantum control
• NSF Q-SEnSE Research Profile — Ivan's role in the NSF quantum sensing and engineering center

Key Papers

• Quantum optimal control of ten-level nuclear spin qudits in Sr-87 (LANL/CQuIC) — The theoretical demonstration of arbitrary SU(10) maps in strontium-87 with average fidelity ~0.9992; the core technical result behind the qudit computing program discussed in the episode
• Spin-cat code paper (ResearchGate) — The fault-tolerant encoding proposal that embeds a qubit in a large-spin qudit, analogous to bosonic cat codes; fault-tolerant thresholds that surpass standard qubit-based encodings

Talks & Context

• IMSI Talk — "Neutral Atom Quantum Computing with Nuclear Spin Qudits" — Ivan's accessible lecture-format talk on the full qudit computing research program; a good companion to the episode
• Quanta Magazine Q&A with Ivan Deutsch (2015) — Still the most accessible public articulation of his philosophy on qudits and computation

Ecosystem

• Quantum New Mexico Institute Launch (Jan 2024) — The founding of the joint UNM/Sandia/LANL institute Ivan established
• UNM/QNM-I Ecosystem Update (Feb 2026) — The current state of the New Mexico quantum industrial ecosystem, including Quantinuum, QuEra, and QNet presence in Albuquerque
• Elevate Quantum profile — Background on the only quantum-focused EDA Tech Hub in the country

Field Context

• Nature (Jan 2026) — Harvard/QuEra fault-tolerant neutral-atom paper — Up to 448 neutral atoms demonstrating below-threshold fault-tolerant QEC; the hardware milestone Ivan's theoretical work is designed to exploit

Key Quotes & Insights

"I don't want to be an evangelist, because I don't really feel I've studied this well enough to say we really should do quantum computation base-10 rather than base-two. But I think it's an important question." — Ivan Deutsch, on qudits — a carefully calibrated position from a theorist making a strong technical bet

"We just wanted to make the whole thing faster." — Steve Rolston (Ivan's co-author), on the mindset behind the Rydberg blockade paper, which ultimately unlocked the entire commercial neutral-atom industry

Insight: The spin cat code ...

Your host, Sebastian Hassinger, is joined on this episode by Garnet Chan, the Bren Professor of Chemistry at Caltech, a member of the National Academy of Sciences, and among the most cited computational chemists in the world (34,000+ Google Scholar citations). Garnet is neither a quantum computing booster nor a dismissive skeptic. He's a theorist who works at the exact boundary between what classical algorithms can and cannot do — and who keeps finding that boundary further out than the quantum computing community has claimed. The FeMo-cofactor has been a flagship quantum computing use case for nearly a decade: a catalytic core of the enzyme that fixes atmospheric nitrogen into ammonia, and a molecule widely described as "beyond classical reach." Chan's January 2026 paper challenges that framing directly. This conversation explains what was actually solved, what wasn't, and what it would genuinely take for quantum computers to contribute to the chemistry of nitrogen fixation. This episode is for researchers, engineers, and informed observers who want an honest, technically grounded view of where quantum computers genuinely help in chemistry — and where classical methods are more capable than the field has admitted. 

What You'll Learn

• Why the FeMo-cofactor became one of the quantum computing community's favorite benchmark — and why the framing around energy savings from nitrogen fixation is less accurate than it sounds
• What "chemical accuracy" (~1 kcal/mol) actually means as a precision target, and why hitting it classically undermines a decade of quantum resource estimates
• Why real chemical systems are only "slightly entangled" — and what that means for the general argument that quantum computers are the natural tool for quantum chemistry
• The difference between a problem being hard and a problem being exponentially hard — and why that distinction matters enormously for quantum advantage claims
• Where the genuine classical wall might be: bridging 15 orders of magnitude in timescale to simulate an enzyme's full catalytic mechanism — and whether quantum computers have anything to say about that
• Why Chan wrote a public blog post explaining his own paper — and what that reveals about the state of discourse in quantum chemistry and the quantum computing industry
• The broader impact of quantum information science on chemistry — beyond hardware, the conceptual tools of quantum information have genuinely reshaped how chemists think about many-body states
• What Chan is actually working toward: a full computational understanding of the nitrogenase reaction mechanism, using machine learning to bridge timescales classically — a decade-long journey he finds genuinely exciting

Resources & Links

The Central Paper & Commentary

• Zhai et al. (2026) — "Classical Solution of the FeMo-Cofactor Model to Chemical Accuracy and Its Implications" arXiv:2601.04621 — The January 2026 preprint at the heart of this episode; the classical solution of the standard 76-orbital/152-qubit FeMo-co benchmark.
• Chan — Quantum Frontiers Blog Post (March 2026) The FeMo-Cofactor and Classical and Quantum Computing — Chan's own accessible commentary on the paper, written in response to widespread misinterpretation; essential reading alongside the paper.

Key Papers for Context

• Chan (2024) — "Spiers Memorial Lecture: Quantum Chemistry, Classical Heuristics, and Quantum Advantage" Faraday Discussions, 254, 11–52 — The formal theoretical framework behind Chan's thinking, including the "classical heuristic cost conjecture"; the deep-dive companion to this episode.
• Lee et al. (2023) — "Evaluating the Evidence for Exponential Quantum Advantage in Ground-State Quantum Chemistry" Nature Communications — Chan group's landmark 2023 paper concluding that evidence for exponential quantum advantage across chemical space has yet to be found.
• Begušić & Chan (2023/2024) — "Fast Classical Simulation of Evidence for the Utility of Quantum Computing Before Fault Tolerance" Science Advances — The paper showing classical simulation on a single laptop core could reproduce and exceed IBM's 127-qubit "utility" experiment.
• Bauer, Bravyi, Motta & Chan (2020) — "Quantum Algorithms for Quantum Chemistry and Quantum Materials Science" arXiv:2001.03685 — A balanced review by Chan and colleagues showing he takes quantum algorithms seriously; useful counterpoint to the skeptical framing.
• Babbush et al. (2025) — "The Grand Challenge of Quantum Applications" arXiv:2511.09124 — Google Quantum AI's direct engagement with Chan's skeptical position; argues polynomial speedups may still be practically decisive.
• Computational Chemistry Highlights — Review of FeMo-co Paper compchemhighlights.org — Third-party commentary from Jan Jensen (University of Copenhagen).

Tools & Software

• PySCF — Python-based Simulations of Chemistry Framework https://pyscf.org — The open-source quantum chemistry package co-stewarded by Chan's group; widely used for electronic structure calculations.
• BLOCK — DMRG and Matrix Product State Algorithms https://github.com/sanshar/Block — Chan group's open-source implementation of density matrix renormalization group methods; the tensor network engine underlying much of this work.

Guest Links

• Chan Lab at Caltech chan-lab.caltech.edu — Research group homepage with publications, software, and group members.
• Garnet Chan — Caltech Faculty Profile cce.caltech.edu/people/garnet-k-chan — Official Caltech Division of Chemistry & Chemical Engineering page.
• Google Scholar Profile scholar.google.com — 34,000+ citations across theoretical chemistry and condensed matter physics.
• Caltech Science Exchange — Ask a Caltech Expert: Quantum Chemistry scienceexchange.caltech.edu — Accessible overview of Chan's perspective for a general science audience.

Key Quotes