Phys. Rev. Lett. 113, 053001 (2014)

At sufficiently low temperatures, systems of laser-cooled and trapped ions can arrange themselves into Coulomb crystal structures that feature soliton-like properties that could prove useful for storing and manipulating quantum information, including the task of generating entanglement. One of the main challenges in the field is how to approach scaling from one-dimensional ion chains to two-dimensional, planar ion crystals. Now, Haggai Landa and co-workers from Israel, France and Germany have studied the interaction of periodically driven two-dimensional ion crystals with optical forces. The international team considered a system composed of 40Ca+ and 43Ca+ ions, which can form in a quadrupole trap with a ring geometry. In this work, 40Ca+ ions, with a dipole-forbidden transition at 729 nm, serve as bits of quantum information (qubits). Their proposed technique requires Doppler cooling of the crystal and sideband cooling of the soliton's localized mode. Analysis reveals the effects of micromotion of ions in radiofrequency traps inherent to such structures.