Quantinuum and Trapped-Ion Quantum Computers: 56 Qubits, 12 Logical Qubits, and Post Quantum Cryptography Context
Why Trapped Ion Matters
Trapped-ion quantum computers trade speed for fidelity. While superconducting qubits run fast but with error rates around 10^-3, trapped ions operate more slowly but with two-qubit gate fidelities exceeding 99.8 percent. For fault-tolerant quantum computing, fidelity matters as much as qubit count. Quantinuum (formed from the merger of Honeywell Quantum Solutions and Cambridge Quantum Computing in 2021) is the global leader in this approach.
H-Series Hardware
The H-series is Quantinuum's commercial trapped-ion line:
- H1 (earlier): 20 qubits, all-to-all connectivity via shuttled ions.
- H2 (upgraded 2024): 56 physical qubits, 99.8 percent two-qubit gate fidelity, all-to-all connectivity.
- H2-1 further upgrades: continuous ongoing improvements in fidelity and cycle time.
All-to-all connectivity means any qubit can be entangled with any other qubit, without the SWAP-gate overhead required on 2D-grid superconducting chips.
Microsoft Partnership: 12 Logical Qubits (September 2024)
In September 2024 Microsoft and Quantinuum announced a breakthrough: 12 logical qubits demonstrated on H2. Using a novel non-local logical qubit encoding, Microsoft was able to error-correct the H2's 56 physical qubits into 12 logical qubits of usable quality. This was the first time a quantum system produced more than a handful of logical qubits.
This is not a CRQC. Running Shor on RSA-2048 requires thousands of logical qubits. But it is a meaningful scaling demonstration and the first step in a multi-year logical-qubit progression.
DARPA QBI Participation
Quantinuum is one of 11 companies advanced to Stage B of DARPA's Quantum Benchmarking Initiative (November 2025). DARPA's stated goal is independent verification of fault-tolerant utility-scale quantum computing by 2033.
Trapped Ion vs Other Technologies
| Technology | Fidelity | Scale | Speed | Connectivity |
|---|---|---|---|---|
| Superconducting (IBM, Google) | ~99.5-99.9% 2Q | Thousands physical | Fast (ns) | 2D neighbors |
| Trapped ion (Quantinuum, IonQ) | >99.8% 2Q | Tens | Slower (microseconds) | All-to-all |
| Photonic (PsiQuantum, Xanadu) | Varies | Photons, not qubits in classical sense | Light-speed | Reconfigurable |
| Neutral atom (Atom Computing, QuEra) | ~99% 2Q | 1000+ | Moderate | Reconfigurable |
Trapped ion's fidelity advantage matters a lot for error correction. Each gate error compounds across thousands of operations in Shor. Higher fidelity means fewer physical qubits per logical qubit, which compresses the resource estimate for CRQC.
Quantinuum's Post Quantum Cryptography Software
Besides hardware, Quantinuum offers Quantum Origin, a service that uses quantum-random-number-generation to feed cryptographic key derivation, and contributes to open-source PQC tooling via collaborations with the Open Quantum Safe project.
Implications
- Trapped-ion scaling is the most promising near-term path to logical qubits, not raw qubit count.
- Watch the Quantinuum+Microsoft partnership for continued logical-qubit scaling.
- The 2033 DARPA QBI timeline depends on hardware like Quantinuum's advancing beyond 12 logical qubits to thousands.
- For your own PQC migration: continue deploying ML-KEM hybrid now, independent of where trapped-ion scaling sits.
Frequently Asked Questions
What is Quantinuum?
A trapped-ion quantum computing company formed in 2021 from the merger of Honeywell Quantum Solutions and Cambridge Quantum Computing. Headquartered in Broomfield, Colorado and Cambridge, UK.
How many qubits does H2 have?
56 physical qubits as of the 2024 upgrade. Two-qubit gate fidelity exceeds 99.8 percent. All-to-all connectivity via ion shuttling.
What happened in September 2024?
Microsoft and Quantinuum announced 12 logical qubits demonstrated on Quantinuum H2, the first multi-logical-qubit demonstration. Using a non-local encoding on the 56-physical-qubit H2.
Is trapped ion faster than superconducting?
No, the opposite. Superconducting gates operate in nanoseconds; trapped ion in microseconds. Trapped ion's advantage is fidelity and all-to-all connectivity, not speed.
Sources
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