Microwave entangling quantum logic gate
The group of C. Ospelkaus has recently realized an entangling quantum logic gate in a surface-electrode ion trap using microwave fields that are produced by a custom microwave "antenna" embedded into the chip surface. In the "standard" ion trap quantum logic approach, such gates are realized using tightly focused laser beams that are produced by highly sophisticated laser systems. In our approach, the entire hardware to realize an entangling gate, the most difficult aspect of quantum logic with ions, is realized using this custom chip design and only standard off-the-shelve microwave components. Such microwave technology has widespread use e. g. in cellphones.
The picture shows two-ion population oscillations between the two qubit states following a global rotation; the lowest points of the green curve correspond to the situation where we create the maximally entangled state 1/sqrt(2)(|00>+|11>). We are currently analyzing the error rates, which appear to be only at the few percent level. They are currently dominated by effects which are purely technical, not related to our method and which can be dealt with in a relatively straightforward way. Stay tuned!