TrappedIon

Trapped ions are atomic ions confined and manipulated with electromagnetic fields in high-vacuum environments. They form well-isolated quantum systems in which both internal electronic states and shared motional states can be precisely controlled, making them a leading platform for quantum information processing and precision measurements.

The most common traps are radiofrequency Paul traps and Penning traps. Paul traps use rapidly oscillating quadrupole fields to create a time-averaged confining potential, while Penning traps use static magnetic fields combined with electrostatic confinement. Linear Paul traps arrange ions in chains for multi-qubit operations.

Qubits are typically encoded in long-lived internal states, such as hyperfine or Zeeman levels of the ion. Ions are laser cooled to near the motional ground state; quantum gates are implemented with laser-driven interactions (for example, Mølmer–Sørensen or Cirac–Zoller type gates) that couple internal and motional degrees of freedom. Readout is achieved by state-dependent fluorescence detection.

Advances in microfabricated surface-electrode traps enable scalable architectures, including segmented traps and junctions that allow shuttling ions between zones. The quantum CCD approach moves ions to different regions for processing and storage. Cryogenic operation and sympathetic cooling with auxiliary ions help reduce motional heating and error rates.

Trapped-ion systems have demonstrated high-fidelity quantum gates and long coherence times, and are used for quantum computation, quantum simulation, and precision metrology. Ongoing work focuses on scaling, error correction, and integration with photonic interfaces to improve readout and interconnects.