  Scaling up and effective cooling of ions in surface ion trap are central
challenges in quantum computing and quantum simulation with trapped ions. In
this theoretical study, we propose a versatile surface ion trap. In the
manipulation zone of our trap, a symmetric seven-wire geometry enables innate
principle-axes rotation of two parallel linear ion chains, which facilitates
the cooling of ions along all principle trap axes. To alleviate contaminating
the manipulation zone during ion loading, a symmetric five-wire geometry is
designed as the loading zone. And a "fork junction" connects the loading and
manipulation zones, which also enables the shuttling and reordering of ions. A
multi-objective optimization procedure suitable for arbitrary junction designs
is described in detail, and we present the corresponding optimal results for
the key components of our trap. The proposed versatile trap can be used in the
construction of large-scale ion quantum processors. The trap also can be used
as the multi-ion-mixer or the efficient ion beam splitter, which has the
potential applications in quantum simulation and quantum computing, the
research of 2D dimensional ion crystals and the guides of quantum microscope,
like an electron beam splitter used for quantum matter-wave optics experiments.
Interesting topics involving the spin-spin interactions between two ion chains
can also be simulated in our trap.
