Quantum Computing Hardware Approaches Diverge Amid Coherence and Scalability Trade-Offs

Quantum computing hardware approaches vary widely, each making different engineering trade-offs. Six major types of quantum computers are superconducting, trapped-ion, photonic, neutral-atom, topological, and annealing systems.

Superconducting qubits use electrical circuits cooled to extremely low temperatures, around 15 millikelvin. This approach is used by IBM, Google, and Rigetti, and has a potential manufacturing advantage as systems scale due to the compatibility with existing semiconductor manufacturing techniques.

However, superconducting qubits have short coherence times, typically measured in microseconds, which increases engineering challenges around control electronics, wiring, and heat management. In contrast, trapped-ion quantum computers use individual atoms suspended in vacuum chambers using electromagnetic fields, achieving high gate fidelity and low error rates but face the main challenge of scaling.

Topological quantum computing remains experimental and contested, relying on exotic quasiparticles called Majorana zero modes whose existence has been debated. Photonic quantum computers encode information in properties of individual photons, which interact weakly with their environment and are difficult to entangle for two-qubit gate operations.