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From an abstract qubit to a device
Superconducting circuits, trapped ions, neutral atoms and photons: what each does well.
- Name the four leading qubit platforms and one strength and weakness of each.
- Explain the DiVincenzo criteria in plain words.
| Platform | Qubit | Gate time | Strength | Weakness |
|---|---|---|---|---|
| Superconducting (IBM, Google) | current in a circuit at 15 mK | 20–100 ns | fast gates, mature fabrication | short coherence, fixed 2D topology |
| Trapped ions (Quantinuum, IonQ) | electron levels of a single ion | 10–100 µs | all-to-all connectivity, long coherence, best fidelities | slow gates, hard to scale |
| Neutral atoms (QuEra, Pasqal) | atoms held by laser tweezers | ≈ 1 µs | hundreds to thousands of qubits, reconfigurable layout | atom loss, slower cycles |
| Photonic (PsiQuantum, Xanadu) | single photons in waveguides | — | room temperature, natural networking | probabilistic gates, photon loss |
Whatever the platform, a useful qubit must satisfy the same list (DiVincenzo, 2000): well-defined two-level systems, a way to initialise them, coherence much longer than a gate, a universal gate set, and a reliable measurement. The calibration panels in QubitLab are those criteria turned into numbers for one real IBM machine.
Which platform offers all-to-all connectivity natively?
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Every platform trades speed against coherence and connectivity. The compiler's job, next lesson, is to hide those differences from your circuit.
Up next: Transpilation and basis gates