Residual decoherence and manipulation of protected qubits

par Benoît Douçot (LPTHE)

jeudi 20 janv. 2011, 11:00 → 12:00 Europe/Paris

Auditorium M. Vivargent (LAPTH)

We have shown how to implement protected qubits using some particular Josephson junction networks. The low energy physics of these systems is well described by the Kitaev toric code model, with proper boundary conditions ensuring the two-fold degeneracy of the ground-state. Using a generalized Master equation approach, I will show that the decoherence times of such qubits are expected to grow exponentially with the system length, provided the spectral density of the noise is contained in a frequency interval smaller than the energy gap of the circuit. I will also describe how to implement single qubit rotations. A rather good surprise is that, in spite of the perturbation induced by the manipulation, some features of the topological protection remain effective. For instance, the rotation axis is itself protected with high accuracy against the effect of the environmental noise during the manipulation. A key role in these analyses is played by the non-local symmetries of such systems.

Slides Doucot