Quantum Computing Hardware
Which correctly describes a trapped-ion quantum computer?
- AIt uses the charge of electrons confined under a silicon MOSFET as qubits
- BIt uses neither a refrigerator nor a vacuum system and holds the ions in room-temperature air with an air flow
- CIt uses electronic energy levels of ions held by electric fields in a vacuum as qubits, and controls them with lasers or microwaves
Show answer and explanation
Answer: C. It uses electronic energy levels of ions held by electric fields in a vacuum as qubits, and controls them with lasers or microwaves
In a trapped-ion system, ions such as ytterbium or calcium are levitated and lined up in a vacuum, for example by radio-frequency electric fields produced by electrodes, and electronic energy levels of the ions serve as qubits. All ions of the same species have identical properties, so there is no fabrication variation, and long coherence times and high gate fidelities are strengths of this approach. The ions share vibrational motion through the Coulomb force, so two-qubit gates can be performed even between ions that are not neighbors. On the other hand, gates are slower than in superconducting systems, and the number of ions that can be lined up in one trap is limited, so handling many ions is a challenge.
- A. This is closer to the approach that confines electrons in silicon quantum dots, not to trapped ions.
- B. The ions are held by electric fields in a vacuum and laser-cooled. In air they could not be held because of collisions with gas molecules.
- C. Correct. The ions are held in a vacuum and controlled with lasers or microwaves.