More on whether useful quantum computing is “imminent”
Source: Hacker News
More on whether useful quantum computing is “imminent”
These days, the most common question I get goes something like this:
A decade ago, you told people that scalable quantum computing wasn’t imminent.
Now, though, you claim it plausibly is imminent. Why have you reversed yourself??
I appreciated the friend of mine who paraphrased this as follows: “A decade ago you said you were 35. Now you say you’re 45. Explain yourself!”
A couple weeks ago I was delighted to attend Q2B (link) in Santa Clara, where I gave a keynote talk entitled “Why I Think Quantum Computing Works” (PowerPoint slides here). This is one of the most optimistic talks I’ve ever given. Uncharacteristically for me, I gave short shrift to the challenge of broadening the class of problems that achieve huge quantum speed‑ups and instead focused on the experimental milestones achieved over the past year. With every experimental milestone, the little voice in my head that asks “what if Gil Kalai turned out to be right after all? What if scalable QC wasn’t possible?” grows quieter; now it can barely be heard.
Going to Q2B was extremely helpful in giving me a sense of the current state of the field.
- Ryan Babbush gave a superb overview (I couldn’t have improved a word) of the current status of quantum algorithms.
- John Preskill’s annual “where‑we‑stand” talk was “magisterial” as usual (that’s the word I’ve long used for his talks), making mine look like just a warm‑up act for his.
- Meanwhile, Quantinuum took a victory lap, boasting of their recent successes in a way that I considered basically justified.
After returning from Q2B I did an hour‑long podcast with “The Quantum Bull” on the topic “How Close Are We to Fault‑Tolerant Quantum Computing?” – you can watch it here:
As far as I remember, this is the first YouTube interview I’ve ever done that concentrates entirely on the current state of the QC race, skipping any attempt to explain amplitudes, interference, and other basic concepts. Despite (or perhaps because of) that, I’m happy with how this interview turned out. Watch if you want to know my detailed current views on hardware—as always, I recommend 2× speed.
Quick summary (for those who don’t have the half hour)
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Two kinds of companies
- Large firms and startups that are actually trying to solve the real technical problems; many are making amazing progress.
- Companies that have optimized for IPOs, astronomical valuations, and selling a narrative to retail investors and governments about how quantum computing will revolutionize optimization, machine learning, and finance.
Right now these two sets are almost entirely disjoint.
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Condemnation of misrepresentations – The interview contains my most direct condemnation yet of some of the wild misrepresentations that IonQ has made to governments (e.g., “unlike AI, quantum computers won’t hallucinate because they’re deterministic!”).
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Most impressive demonstrations (past year)
- Trapped ions – especially Quantinuum (also Oxford Ionics)
- Superconducting qubits – especially Google (also IBM)
- Neutral atoms – especially QuEra (also Infleqtion and Atom Computing)
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My views haven’t dramatically changed – As I have for a quarter‑century, I continue to have a lot of confidence in the basic principles of quantum‑computing theory worked out in the mid‑1990s, and I also remain ignorant of exactly how many years it will take to realize those principles in the lab, or which hardware approach will get there first.
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But I do update in response to developments on the ground – 2025 was clearly a year that met or exceeded my expectations on hardware, with multiple platforms now boasting > 99.9 % fidelity two‑qubit gates, at or above the theoretical threshold for fault‑tolerance. This year nudged me toward taking the aggressive “roadmaps” of Google, Quantinuum, QuEra, PsiQuantum, and others (2028‑2029 targets) more seriously.
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Known applications (still the same three)
- Simulation of quantum physics and chemistry.
- Breaking a lot of currently deployed cryptography.
- Eventually achieving some modest benefits for optimization, machine learning, and other areas (though it will probably be a while before those modest benefits win out in practice).
The detailed list of quantum speed‑ups expands over time (as new algorithms are discovered) and contracts (as some algorithms are de‑quantized), but the “30,000‑foot‑view” list remains fairly close to what it was a quarter‑century ago, after you cut through the dense thickets of hype.
A warning from history
When Frisch and Peierls wrote their now‑famous memo in March 1940, estimating the mass of U‑235 needed for a fission bomb, they didn’t publish it in a journal but communicated the result through military channels only. As recently as February 1939, Frisch and Meitner had published in Nature their theoretical explanation of recent experiments, showing that the uranium nucleus could fission.
Similarly, at some point the people doing detailed estimates of how many physical qubits and gates it will take to break actually deployed cryptosystems using Shor’s algorithm are going to stop publishing those estimates, if for no other reason than the risk of giving too much information to adversaries. Indeed, for all we know, that point may have already been passed. This serves as a reminder that, as a field, we sometimes have to balance openness with security considerations.
Nearest warning that I can offer in public right now about the urgency of migrating to post‑quantum cryptosystems, a process that I’m grateful is already underway.
Update: Someone on Twitter who’s “long $IONQ” says he’ll be posting about and investigating me every day, never resting until UT Austin fires me, in order to punish me for slandering IonQ and other “pure‑play” SPAC‑IPO quantum companies. He also claims it’s because I’ve been anti‑Trump and pro‑Biden. He confabulates that I must be trying to profit from my stance (e.g., by shorting the companies I criticize), finding it inconceivable that anyone would speak out purely because they care about what’s true.
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Comments
Michael Marthaler – quantumsimulations.de
Comment #1 – December 21st, 2025 at 1:32 pm
Do you know if the Q2B Talks will also be online available?
Scott – scottaaronson.com
Comment #2 – December 21st, 2025 at 1:48 pm
Michael #1: At least some of them, I think, but not sure when.
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