Reconfigurable Single Ion Addressing System*

The ability to scale QIP to larger systems relies on the individual control of qubits in a multi-qubit register with small crosstalk. Towards this goal, we have designed a novel single ion addressing scheme that allows reconfigurable and parallel control of single and multi qubit gates across a chain of trapped ions using Raman transitions.  

With this novel excitation scheme, the ion spacing and number can be reconfigured dynamically within an experimental sequence, which is not possible with current multi-channel AOM setups. Additionally, all laser power can be used in any desired configuration and switching speeds between configurations are on the order of 100ns, much faster than gate operations.

We report on the design and optical characterization of such a system, compatible with the HOA 2.1 surface ion trap. In particular, the system is designed to address with low crosstalk up to 30 ions with ion-distances of 7 um. Assuming a numerical aperture of 0.2 and a wavelength of 400 nm, a spot size of approx. 2.5 um can be achieved on the ion position, allowing for the crosstalk (ratio of Rabi frequency of the adjacent ion and the addressed ion) of less than 10^-2.