Microfabricated ion trap chip with an integrated microwave antenna
An ion trap chip, which may be used for quantum information processing and the like, includes an integrated microwave antenna. The antenna is formed as a radiator connected by one of its ends to the center trace of a microwave transmission line and connected by its other end to a current return path through a ground trace of the microwave transmission line. The radiator includes several parallel, coplanar radiator traces connected in series. The radiator traces are connected such that they all carry electric current in the same direction, so that collectively, they simulate a single, unidirectionally flowing sheet of current. In embodiments, induced currents in underlying metallization planes are suppressed by parallel slots that extend in a direction perpendicular to the radiator traces.
1. Apparatus comprising an ion trap chip, wherein:
the ion trap chip comprises a substrate, a top metallization layer formed over the substrate, and at least one further metallization layer formed between the substrate and the top metallization layer;
a microwave antenna is integrated on the ion trap chip;
the microwave antenna comprises a plurality of parallel radiator traces formed in the top metallization layer; and
the plurality of radiator traces is connected in series such that the direction of current flow is the same in each radiator trace.
2. The apparatus of claim 1 , wherein the series connection between each radiator trace and at least one neighboring radiator trace is made through vertical paths to and from a metallization layer lower than the top metallization layer, and through a horizontal loop-back path in the said lower metallization layer.
3. The apparatus of claim 2 , wherein:
the at least one further metallization layer formed between the substrate and the top metallization layer comprises at least a metallization layer nearest the top metallization layer and a metallization layer next-nearest the top metallization layer;
said nearest layer and said next-nearest layer each are fenestrated by a pattern of parallel slots;
the slots are perpendicular to the radiator traces; and
the slots in the nearest layer are offset from the slots in the next-nearest layer so that there is no overlap between slots in the respective said nearest and next-nearest layers.
4. The apparatus of claim 3 , wherein each of the radiator traces comprises an air bridge over each slot that it crosses in the next-nearest metallization layer.
5. The apparatus of claim 4 , wherein a total of six metallization layers are formed over the substrate, said metallization layers respectfully denominated M 1 , M 2 , M 3 , M 4 , M 5 , and M 6 , M 6 being the top metallization layer, and wherein:
the radiator traces are formed in M 6 ;
M 5 and M 4 are respectfully the said nearest and next-nearest metallization layers; and
the horizontal loop-back paths are formed in M 3 and M 2 .