Go further · Chapter 8 · 8b · A step deeper
How many logical qubits exist today?
The short answer (tap to open)
As of October 2026, the record for fully error-corrected logical qubits running together is 48, on Quantinuum's Helios (November 2025), and 94 with error detection. Google showed in 2024 that bigger codes give fewer errors. Harvard, MIT and QuEra showed every fault-tolerance ingredient together in 2025. Nobody has yet run a long, useful program on many logical qubits.
What are the milestones so far?
Each entry shows whether it's peer reviewed or a company claim.
Last checked: 2 October 2026.
December 2023 · Peer reviewed
Harvard and QuEra (neutral atoms): Programs run on 48 logical qubits.
Logical quantum processor based on reconfigurable atom arrays (Nature 626, 58)
March 2024 · Peer reviewed
IBM: A new code family ("gross" code) needing about ten times fewer physical qubits than the surface code. A design, not yet a full machine.
High-threshold and low-overhead fault-tolerant quantum memory (Nature 627, 778)
April 2024 · Company claim or announcement
Microsoft and Quantinuum (ions): Logical qubits with error rates 800 times lower than the physical ones.
How Microsoft and Quantinuum achieved reliable quantum computing
November 2024 · Company claim or announcement
Microsoft and Atom Computing (atoms): 24 logical qubits entangled.
December 2024 · Peer reviewed
Google Willow (superconducting): The first clear "below threshold" surface code: each step up in size halved the error rate.
Quantum error correction below the surface code threshold (Nature 638, 920)
November 2025 · Company claim or announcement
Quantinuum Helios (ions): 94 logical qubits entangled with error detection; 48 fully error-corrected, using two physical qubits each.
Introducing Helios: the most accurate quantum computer in the world
November 2025 · Company claim or announcement
IBM: Real-time decoding in under half a millionth of a second, and a test chip with all the parts for error correction.
November 2025 · Peer reviewed
Harvard, MIT and QuEra (atoms): Every ingredient of fault-tolerant computing working together on 448 atoms, below threshold.
August 2026 · Company claim or announcement
Quantinuum: Logical error rates near one in a hundred thousand with a new code family.
The milestones, in a list
- December 2023, Harvard and QuEra (neutral atoms): Programs run on 48 logical qubits. (Peer reviewed.)
- March 2024, IBM: A new code family ("gross" code) needing about ten times fewer physical qubits than the surface code. A design, not yet a full machine. (Peer reviewed.)
- April 2024, Microsoft and Quantinuum (ions): Logical qubits with error rates 800 times lower than the physical ones. (Company claim or announcement.)
- November 2024, Microsoft and Atom Computing (atoms): 24 logical qubits entangled. (Company claim or announcement.)
- December 2024, Google Willow (superconducting): The first clear "below threshold" surface code: each step up in size halved the error rate. (Peer reviewed.)
- November 2025, Quantinuum Helios (ions): 94 logical qubits entangled with error detection; 48 fully error-corrected, using two physical qubits each. (Company claim or announcement.)
- November 2025, IBM: Real-time decoding in under half a millionth of a second, and a test chip with all the parts for error correction. (Company claim or announcement.)
- November 2025, Harvard, MIT and QuEra (atoms): Every ingredient of fault-tolerant computing working together on 448 atoms, below threshold. (Peer reviewed.)
- August 2026, Quantinuum: Logical error rates near one in a hundred thousand with a new code family. (Company claim or announcement.)
What should you watch next?
Company roadmaps promise: IBM's Kookaburra module (2026) and Starling, 200 logical qubits (2029); Quantinuum's Sol, 100 logical qubits (2027), and Apollo (2029); QuEra's Libra, 256 logical qubits (2028); Google's "long-lived logical qubit" milestone. Chapter 11 shows how to read these.
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Dozens of logical qubits, not yet hundreds.
The milestones are real; long useful programs are next.