Rapid control and measurement of clock-state qubits in Yb and Sr

The optical clock-transitions in Yb and Sr are prime candidates for encoding qubits for quantum information processing applications. Electric dipole one- and two- photon transitions between the extremely long-lived $^1$S$_0$ and $^3$P$_0$ states are dipole and parity forbidden, respectively. Whereas this results in highly desirable low-decoherence rates, it also represents the main problem for fast coherent manipulation and measurement of qubits for quantum information processing. In this work, we determine the feasibility of using a coherent, recoil-free, three- photon transition [1] for fast coherent rotation of qubits followed by ultrafast readout of the $^3$P$_0$ state via photo ionization. Rapid control and measurement of atomic qubits are crucial for high-speed synchronization of quantum information processors. Furthermore, we explore the possibility of loophole free tests of Bell inequalities using spatially separated entangled qubits via fast measurements. [1] T. Hong, C. Cramer, W. Nagourney, E. N. Fortson, Phys. Rev. Lett. 94, 050801 (2005)