  We show that the recently discovered quantum-enhanced measurement protocol of
coherent averaging that is capable of achieving Heisenberg-limited sensitivity
without using entanglement, has a classical analogue. The classical protocol
uses N harmonic oscillators coupled to a central oscillator and one measures
the signal from the latter. We propose an application to the measurement of
very weak interactions, and, in particular, a novel route to measuring the
gravitational constant with enhanced precision.
