Valley splitting in bilayer graphene quantum point contacts

Conductance quantization in steps of 2e^{^2}/h in one-dimensional channels is among the cornerstones of mesoscopic physics. In graphene quantum point contacts, an extra degeneracy is expected due to the valley degree of freedom. We here discuss experimental data in electrostatically induced quantum point contacts in bilayer graphene that display fourfold degeneracy at zero and quantizing magnetic fields and twofold degeneracy at intermediate fields. We argue that by switching on the magnetic field the valley degeneracy is lifted. Our results may be relevant both for valleytronic applications as a way to generate valley polarizations with planar devices and for creating spin qubits in graphene nanostructures.