Speaker
Benoit Doucot
(LPTHE, CNRS)
Description
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.
