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From an abstract qubit to a device
Superconducting circuits, trapped ions, neutral atoms and photons: what each does well.
- 01Name the four leading qubit platforms and one strength and weakness of each.
- 02Explain 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.
Same circuit, two chips
Compile this three-qubit GHZ circuit for fake_sherbrooke, then for fake_torino. Both are superconducting IBM chips, yet their native two-qubit gate differs: the two CNOTs become ECR gates on the older Eagle chip and CZ gates on the newer Heron chip, each wrapped in RZ and SX rotations. Every platform has its own native gate set, and the compiler translates for you.
OPENQASM 3.0;
include "stdgates.inc";
qubit[3] q;
bit[3] c;
h q[0];
cx q[0], q[1];
cx q[1], q[2];
c = measure q;
2 questions · one try each counts
Which platform offers all-to-all connectivity natively?
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Which platform has the fastest gates but the shortest coherence time?
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