A strain-engineered graphene qubit in a nanobubble
We propose a controllable qubit in a graphene nanobubble with emergent two-level systems induced by pseudo-magnetic fields. We found that double quantum dots can be created by the strain-induced pseudo-magnetic fields of a nanobubble, and that their quantum states can be manipulated by either local gate potentials or the pseudo-magnetic fields. Graphene qubits clearly exhibit an avoided crossing behavior via electrical detuning, with energy splittings of about a few meV. We also show a remarkable tunability of our device design that allows for the fine control of the Landau--Zener transition probability through strain engineering of the nanobubble, showing half-and-half splitting at the avoided crossing point. Further, we demonstrate that the two-level systems in the nanobubble exhibit Rabi oscillations near the avoided crossing point, resulting in very fast Rabi cycles of a few ps.