Understanding quantum entanglement: Qubits,rebits and the quaternionic approach

It has been recently pointed out by Caves, Fuchs, and Rungta 1] that real quantum mechanics (that is, quantum mechanics defined over real vector spaces 2–5]) provides an interesting foil theory whose study may shed some light on just which particular aspects of quantum entanglement are unique to standard quantum theory and which are more generic over other physical theories endowed with this phenomenon. Following this work, some entanglement properties of two-rebit systems are discussed and a comparison with the basic properties of two-qubit systems, i.e., the systems described by standard complex quantum mechanics, is made. The use of quaternionic quantum mechanics as applied to the phenomenon of entanglement is also discussed.