Long-Range Interaction between Charge and Spin Qubits in Quantum Dots

We analyze and give estimates for the long-distance coupling via floating metallic gates between different types of spin qubits in quantum dots made of different commonly used materials. In particular, we consider the hybrid, the singlet-triplet, and the spin-1/2 qubits, and the pairwise coupling between each type of these qubits with another hybrid qubit in GaAs, InAs, Si, and $\mathrm{Si_{0.9}Ge_{0.1}}$. We show that hybrid qubits can be capacitively coupled strongly enough to implement two-qubit gates, as long as the dimensions of the dots and their distance from the metallic gates are small enough. Thus, hybrid qubits are good candidates for scalable implementations of quantum computing in semiconducting nanostructures.