Entangling two and more ions with collective laser-ion interactions

Laser-ion interactions that collectively couple the pseudo-spins of a string of trapped ions to one of the string´s vibrational modes have been used by us to entangle a pair of ⁴⁰Ca⁺ ions with very high fidelity. This gate mechanism allows for entangling ions without having recourse to ground state cooling. This opens the way to performing an entangling gate after having applied an operation which does not preserve the ions´ motional state like for example state detection. This paper presents an overview of the gate mechanism and experimental results obtained with two ions. Recent experiments in which the same laser-ion interaction to two or more ions is applied, is discussed . Creating three-particle GHZ states with a fidelity of 98% is achieved.