Nanomechanical systems are high frequency (hundreds of MHz to GHz) mechanical resonators constructed at the sub micron scale and cooled to near their quantum mechanical ground state. They have application to ultrasensitive sensors for single molecules and weak forces. They also provide access to a range of fascinating physics at the quantum-classical boundary. A quartic nonlinear term in the elastic potential energy can make them respond like a Duffing oscillator which can be used to make a sensitive strain sensor. However the small size of nanomechanical resonators makes transduction of their motion difficult. This project will study quantum-limited transducers for nanomechanical systems with a view to feedback control.