title: Universal set of quantum gates for double-dot spin qubits with fixed interdot coupling.
abstract: We propose a set of universal gate operations for the singlet-triplet qubit realized by two-electron spins in a double quantum dot, in the presence of a fixed inhomogeneous magnetic field. All gate operations are achieved by switching the potential offset between the two dots with an electrical bias, and do not require time-dependent control of the tunnel coupling between the dots. We analyze the two-electron dynamics and calculate the effective qubit rotation angle as a function of the applied electric bias. We present explicit gate sequences for single-qubit rotations about two orthogonal axes, and a CNOT gate sequence, completing the universal gate set.
authors.affiliation: Center for Spintronics and Quantum Computation, University of California, Santa Barbara, California 93106, USA.
authors.forename: Ronald
authors.initials: R
authors.lastname: Hanson
authors.forename: Guido
authors.initials: G
authors.lastname: Burkard