A Nuclear Spin Valve: Towards the Read-out of Single Nuclear Spin Qubits

We propose a scheme to read out qubits defined in single nuclear spins—addressing one of the main obstacles on the way to a solid state NMR quantum computer. It is based on a “spin valve” between bulk nuclear spin systems that is highly sensitive to the state of the qubit spin. We suggest a concrete realization of that detector in a Si lattice and show that it can be operated over a broad range of experimental parameters. Transport of spin through the proposed spin valve is analogous to that of charge through an electronic nanostructure, but exhibits distinctive new features.