Figure 2. Setup for the ring-ring coupling.

Two parallel Gaussian laser beams (G1,G2) are produced by a combination of two polarizing beamsplitter (BS1, BS2). The beam separation D can be controlled by moving mirror M₁. Both beams pass through a lens and interfere to form a lattice in z-direction. The distance between the lattice planes is a function of 1/D²⁶ which can be varied. The resulting one dimensional lattice is combined with vertical beams (LG1, LG2) providing horizontal confinement for trapped atoms (See the Methods section). The inset shows the ring lattice potentials separated by²⁶ d = λ₁f/D. The ring-ring separation is adjustable by varying the distance D. Such an arrangement provides an effective two-level system that can be exploited as a qubit (See text).