2ioni

2ioni is a term used in theoretical and educational discussions to denote a simple two-ion quantum processor model. In this model, information is stored in the internal states of two trapped ions, while their shared motional mode provides a coupling mechanism for entangling operations. The name derives from the two-ion configuration that forms the basic unit.

In a typical 2ioni setup, each qubit is encoded in two long-lived internal states of an ion. Quantum gates are implemented with laser pulses that drive transitions between these states, enabling universal quantum computation when combined with a two-qubit gate on the pair, such as a Mølmer–Sørensen or Cirac–Zoller–type operation. Readout is performed by state-dependent fluorescence, allowing projective measurement of each ion.

The two-ion module is often described as a minimal, fully functional block for teaching and small-scale experiments. Its advantages include well-characterized coherence properties and high gate fidelities demonstrated in trapped-ion systems. The main challenges concern scaling: assembling many two-ion modules into a larger processor requires reliable interconnects and effective quantum error correction strategies, topics treated in broader trapped-ion architectures.

Etymologically, 2ioni simply reflects the two-ion basis used in the model. In educational literature it is used to contrast simple two-qubit modules with multi-ion or alternative-qubit platforms.