1306.3596 (Christoph Kloeffel et al.)

Circuit QED with Hole-Spin Qubits in Ge/Si Nanowire Quantum Dots    [PDF]

Christoph Kloeffel, Mircea Trif, Peter Stano, Daniel Loss

We propose a setup for universal and electrically controlled quantum information processing with hole spins in Ge/Si core/shell nanowire quantum dots (NW QDs). Single-qubit gates can be driven through electric-dipole-induced spin resonance, with spin-flip times shorter than 100 ps. Long-distance qubit-qubit coupling can be mediated by the cavity electric field of a superconducting transmission line resonator, where we show that operation times below 20 ns seem feasible for the entangling square-root-of-iSWAP gate. The absence of Dresselhaus spin-orbit interaction (SOI) and the presence of an unusually strong Rashba-type SOI enable precise control over the transverse qubit coupling via an externally applied, perpendicular electric field. The latter serves as an on-off switch for quantum gates and also provides control over the g factor, so that single- and two-qubit gates can be operated independently. Remarkably, we find that idle states are insensitive to charge noise and phonons, and we discuss strategies for enhancing noise-limited gate fidelities.

View original: http://arxiv.org/abs/1306.3596