Quantum computations and simulations in segemented ion traps rely on the ability to perform gate operations with high fidelity. On the one hand, the quantum optical gate operations for single ions or between two ions need to be performed with high precision and error resilience. On the other hand, the transport operations in the trap need to be performed fast while at the same time a minimum amount of energy is to be transferred to the ion.

Therefore, optimal control theory is an ideal tool to derive fast and robust laser pulses for gate operations [1] and voltage waveforms for transport sequences [2].  Optimal control results can improve existing solutions in two ways: First, approximations that were used for deriving simple solutions (like considering fully harmonic trap potentials for the transport problem) can be dropped. Furthermore, optimal control solutions show an enhance robustness against noise as  the represent extrema in the control space. This has been experimentally demonstrated for single ion gates by the group of Christoph Wunderlich [1]. In our group, we use both classical trajectory    and wavepacket dynamics simulations for the various transport problems. For the quantum gate operations, we numerically solve the complete time evolution of the unitary propagator [3]. more applications of OCT...

[1] N. Timoney et al., quant-ph/0612106 (2006)
[2] S. Schulz et al., Progress of Physics, Wiley  54, No. 8 - 10,  648 (2006)
[3] J. P. Palao et al., Phys. Rev. A 68, 062308 (2003)

We collaborate with several european research groups within the training network Emali.