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Forecasting timelines of quantum computing

Jaime Sevilla, C. Jess Riedel

2020 · arXiv

PhysicsStatistics & probabilityDistributed systems
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From the abstract

We consider how to forecast progress in the domain of quantum computing. For this purpose we collect a dataset of quantum computer systems to date, scored on their physical qubits and gate error rate, and we define an index combining both metrics, the generalized logical qubit. We study the relationship between physical qubits and gate error rate, and tentatively conclude that they are positively correlated (albeit with some room for doubt), indicating a frontier of development that trades-off between them. We also apply a log-linear regression on the metrics to provide a tentative upper bound on how much progress can be expected over time. Within the (generally optimistic) assumptions of our model, including the key assumption that exponential progress in qubit count and gate fidelity will continue, we estimate that that proof-of-concept fault-tolerant computation based on superconductor technology is unlikely (<5% confidence) to be exhibited before 2026, and that quantum devices capable of factoring RSA-2048 are unlikely (<5% confidence) to exist before 2039. It is of course possible that these milestones will in fact be reached earlier, but that this would require faster progress than has yet been seen.

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4 selected excerpts · 4 total mentions

rhaps0dy
Neutral mention · rule
Thank you for the explanation. It's still an upwards update on the qubit timelines of https://arxiv.org/pdf/2009.05045 (see Fig. 7), but not by an insane amount. We've realized their 95% expectation of qubit progress (1 logical qubit) for 2026, in 2024.92 instead. Which to be clear is quite a bit faster than expected in 2020, but still within the realm of plausible stuff.
Original comment Willow, Our Quantum Chip
jessriedel
Neutral mention · rule
> I thought the error rate has stayed pretty exponential in terms of the number of physical qubits needed to express a logical qubit There is finite a threshold error rate (roughly 0.1-1%) at which you can produce a single logical qubit with an unbounded number of physical qubits (infinite overhead). For error rates below the threshold, the overhead becomes much less. People expect overheads in the thousands. See Fig. 1 in our paper. https://arxiv.org/pdf/2009.05045 > and it’s not actually known if we’re any closer on that metric vs other more easily achieved metrics. We are getting lower error rates. But until we cross the error threshold, the overhead for a logical…
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qubit is infinity. > I was under the impression that not all QCs being built are able of executing Shor’s algorithm Correct. > which added additional challenges that aren’t solved. Logical qubits enable general purpose quantum computing, which includes Shor's algorithm. As mentioned, we don't have logical qubits yet, and some people are trying to build less general devices to solve certain math problems in the meantime. But the overall goal for the field is still logical qubits, and there's steady progress on that. > My final impression is that having the QC algorithm run faster than a classical computer doing the same operation has also not necessarily gotten better I can't really parse the claim, but I think your impression is wrong. Supremacy has always been a fuzzy bound, since it's defined in terms of the best known classical algorithms. But the supremacy results have gotten more unambiguous over time.
Original comment What You Shouldn't Know About Quantum Computers
jessriedel
Neutral mention · rule
At least as of 2020, it looked like both qubit counts and two-qubit gate quality were improving exponentially, and our naive extrapolation said RSA 2048 wouldn't get cracked by 2039 at 95% confidence. https://arxiv.org/abs/2009.05045 As far as I can tell, this website suggests that two-qubit gate infidelity has continued to improve exponentially, although it's hard to tell if these are reliable datapoints. https://metriq.info/Task/38 Because there's typically an engineering tension between qubit count and gate quality, what you want to track is something like quantum volume, which looks to be on trend https://metriq.info/Task/34 but it's notable that Google achieved…
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quantum supremacy without having amazing quantum volume numbers, so it's not a perfect metric https://spectrum.ieee.org/quantum-computing-google-sycamore Worth noting that once you cross the fault tolerant threshold you will probably see a big shift in how engineering effort is distributed: many researchers think it will be harder to improve gate quality than just increase increase qubit counts to make up for it, so you may see gate quality stall and extrapolation become even less reliable.
Original comment 2048 Bit RSA and the Year 2030

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