Qubits from tight knots and bent nano-bars

We propose a novel mechanism for creating a qubit based on a tight knot, that is a nano-quantum wire system so small and so cold as to be quantum coherent with respect to curvature-induced effects. To establish tight knots as legitimate candidates for qubits, we propose an effective curvature-induced potential that produces the two-level system and identify the tunnel coupling between the two local states. We propose also a different design of nano-mechanical qubit based on twisted nano-rods. We describe how both devices can be manipulated. Also we outline possible decoherence channels, detection schemes and experimental setups.