When will a quantum computer be capable of operating with over 1,000 fully error-corrected logical qubits?

TL;DR

My median forecast is February 16, 2033, with a central 80% interval from August 30, 2029 to November 22, 2040. The model assigns 13% probability by December 31, 2029, 58.3% by December 31, 2033, and 3% after December 31, 2050. The main reason is that the clean multi-qubit active-QEC frontier is about eight logical qubits, not the 48–96 counts in headlines, while high-rate codes and already-large atom arrays make a sudden jump technically plausible (Microsoft and Quantinuum, Nature).

Context

The threshold is 1,001 logical qubits in one system. They must operate simultaneously with active error correction: repeated syndrome extraction and decoding, or an architecture-appropriate equivalent. Error detection, post-selection-dependent counts, simulations, combined machines, and unsupported announcements do not count.

This milestone is easier than a useful 1,001-logical-qubit computer. A large corrected memory experiment could resolve it without a valuable algorithm or a very low logical error rate. But the public evidence through July 23, 2026 still shows a large gap between clean active-QEC demonstrations and vendor specifications.

Evidence

The best historical backbone is roadmap revision, not a smooth trend in reported logical-qubit counts. The experiments use different codes, depths, error rates, and rejection rules, so treating their headline counts as one time series would create false precision.

The strict frontier is smaller than the usual headlines suggest. On September 10, 2024, Microsoft and Quantinuum reported a 12-logical-qubit cat state, but their repeated-error-correction experiment ran five rounds on eight logical qubits (Microsoft). A peer-reviewed superconducting qLDPC experiment published January 22, 2026 encoded six logical qubits in 18 data qubits, used 12 check qubits, executed up to six syndrome cycles, and decoded more than 40,000 experimental instances per point after leakage rejection; its average logical error was 7.77% ± 0.12% per logical qubit per cycle, still above its physical baseline (Nature Physics). These are the clearest multi-logical-qubit active-QEC results, and both remain far from a clean, continuously usable register of hundreds.

The larger counts have resolution-grade caveats. A February 25, 2026 Quantinuum preprint ran a full QEC cycle on a [[80,48,4]] code, but accepted only 62% ± 2% of shots after rejecting detected uncorrectable errors; the same work's 94-logical-qubit results used distance-two error-detecting codes (arXiv). A neutral-atom paper published November 10, 2025 had up to 96 distance-four logical qubits active simultaneously, but the large cluster-state results improved with stricter post-selection, while its no-post-selection repeated surface-code demonstration was a separate small-count experiment (Nature). I therefore use roughly 6–8 as the clean multi-round frontier and 48–96 only as evidence that high-rate encoding and parallel control are advancing.

The strongest early signal is that the logical count can jump through code choice. An April 17, 2026 simulation studied a [[2304,1156,≤14]] neutral-atom-compatible qLDPC code. At an assumed 0.1% circuit-level physical error rate, it projected a per-logical-qubit, per-round error near 1.3 × 10^-13 (arXiv). This is not experimental evidence, but one such block would cross the question's threshold. Hardware scale is also no longer purely hypothetical: a neutral-atom array published September 24, 2025 trapped more than 6,100 atoms with 12.6-second coherence and high-fidelity individual control (Nature); another system published September 15, 2025 maintained more than 3,000 atoms for over two hours and loaded up to 30,000 initialized qubits per second (Nature). These systems did not integrate the gates, measurement, decoding, and repeated QEC assumed by the code simulation.

Independent institutions point to the early 2030s. The U.S. Department of Energy's June 23, 2026 Quantum Genesis initiative targets fault-tolerant systems with logical-qubit counts in the low hundreds in 2028 (DOE). DARPA said on March 10, 2026 that a utility-scale quantum computer by 2033 now seemed likely after evaluating 20 commercial approaches, with 11 in Stage B and two in Stage C validation (DARPA). The 2026 NNSA/LLNL planning report places hundreds of near-perfect logical qubits around 2030–2033 and thousands of much stronger logical qubits beyond 2033 (ASC Quantum Report). Those standards are harder than this question's count-only threshold, so I place the median near, rather than after, 2033.

I used one continuous lognormal schedule model rather than separate roadmap-success and roadmap-failure scenarios. For elapsed time t in years after the July 23, 2026 information cutoff, the cumulative probability is F(t) = 0.985 × Φ((ln(t) − ln(6.5)) / 0.58). The 6.5-year scale centers the forecast on early 2033; the 0.58 log-time spread gives meaningful weight to the 2028/29 roadmaps and a long integration-risk tail; the 98.5% ceiling reserves structural mass for severe stagnation, persistent definitional conflict, or indefinite non-resolution. The resulting cumulative probabilities are 5% by the end of 2028, 13% by 2029, 25% by 2030, 48.6% by 2032, 58.3% by 2033, 73% by 2035, and 90% by 2040.

What's non-obvious

Most quick readings make two opposite errors. They treat 48 or 96 as today's fully corrected frontier, which makes 2028/29 look too easy. They also extrapolate surface-code overhead as if more than 1,000 logical qubits must require millions of physical qubits, which makes the milestone look too distant. The strict-count correction pushes the date later; high-rate codes and large neutral-atom arrays pull it earlier. Their balance puts the center near 2033.

The first press release claiming 1,000 logical qubits may not resolve the question. The likely failure modes are a count based on error detection, heavy run rejection, separate code blocks not operated simultaneously, or a specification without public data. The time from a headline claim to an accepted technical disclosure is part of the forecast.

Limitations

There is no mature statistical reference class. The clearest schedule-slippage example is one company's roadmap revision, while the major programs share code research, suppliers, talent, and financing conditions. Their risks are correlated.

The experimental record is heterogeneous. Leakage rejection, repeat-until-success preparation, Pauli-frame correction, offline decoding, and one-cycle QEC sit near the boundary of the resolution language. Expert consensus could classify a future claim differently from my reading.

The model also has no separate annulment outcome. The final post-2050 bucket absorbs very long delays, persistent ambiguity, and cases that would in practice be annulled rather than resolved.