Trapped Ion Qubits: Precision Atoms

Introduction

Trapped ion quantum computing uses individual charged atoms (ions), typically Ytterbium ($Yb^+$) or Calcium ($Ca^+$), suspended in vacuum by electromagnetic fields. Lasers are then used to manipulate their internal electronic states.

The Paul Trap

To isolate the ions, researchers use a Paul Trap (radiofrequency quadrupole trap) which creates a dynamic electric potential that holds a linear chain of ions in place in an ultra-high vacuum chamber.

Advantages

1. Identical Qubits: Unlike synthetic qubits (e.g., superconducting circuits), every atom of a given isotope is perfectly identical by nature.
2. High Coherence: Trapped ions can maintain their quantum coherence for seconds, or even hours in specialized configurations.
3. High Gate Fidelity: Trapped ion systems regularly demonstrate some of the highest single- and two-qubit gate fidelities in the industry.

Gates and Manipulation

Qubits are manipulated by shining focused laser beams on specific ions. Two-qubit gates are mediated by the collective vibrational motion (phonons) of the ion chain, driven by laser forces.