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 Si0.9Ge0.1.
We show that hybrid qubits can be capacitively coupled strongly enough to implement two-qubit
gates, as long as the distance of the dots from the metallic gates is small enough. Thus, hybrid
qubits are good candidates for scalable implementations of quantum computing in semiconducting
nanostructures.