  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.
