  The implementation of a functional quantum computer involves entangling and
coherent manipulation of a large number of qubits. For qubits based on electron
spins confined in quantum dots, which are among the most investigated
solid-state qubits at present, architectural challenges are often encountered
in the design of quantum circuits attempting to assemble the qubits within the
very limited space available. Here, we provide a solution to such challenges
based on an approach to realizing entanglement of spin qubits over long
distances. We show that long-range Ruderman-Kittel-Kasuya-Yosida interaction of
confined electron spins can be established by quantum Hall edge states, leading
to an exchange coupling of spin qubits. The coupling is anisotropic and can be
either Ising-type or XY-type, depending on the spin polarization of the edge
state. Such a property, combined with the dependence of the electron spin
susceptibility on the chirality of the edge state, can be utilized to gain
valuable insights into the topological nature of various quantum Hall states.
