Controllable anisotropic exchange coupling between spin qubits in quantum dots

Abstract: The exchange coupling between quantum dot spin qubits is isotropic, which restricts the types of quantum gates that can be formed. Here, we propose a method for controlling anisotropic interactions between spins arranged in a bus geometry. The symmetry is broken by an external magnetic field, resulting in XXZ-type interactions that can efficiently generate Greenberger-Horne-Zeilinger (GHZ) states or universal gate sets for exchange-only quantum computing. Analysis of the bus ground state provides a link between quantum critical phenomena and the communication capacity.