  We propose an electromechanical transducer based on a resonant-tunneling
configuration that, with respect to the standard tunneling transducers, allows
larger tunneling currents while using the same bias voltage. The increased
current leads to an increase of the shot noise and an increase of the momentum
noise which determine the quantum limit in the system under monitoring.
Experiments with micromachined masses at 4.2 K could show dominance of the
momentum noise over the Brownian noise, allowing observation of the
quantum-mechanical noise at the mesoscopic scale.
