EN
In all quantitative sciences, it is common practice
to increase the signal-to-noise ratio of noisy measurements
by measuring identically prepared systems N
times and averaging the measurement results. This leads
to a scaling of the sensitivity as 1/√N, known in quantum
measurement theory as the “standard quantum limit”
(SQL). It is known that if one puts the N systems into an
entangled state, a scaling as 1/N can be achieved, the socalled
“Heisenberg limit” (HL), but decoherence problems
have so far prevented implementation of such protocols
for large N. Here we show that a method of coherent averaging
inspired by a recent entanglement-free quantum
enhanced measurement protocol is capable of achieving a
sensitivity that scales as 1/N in a purely classical setup.
This may substantially improve the measurement of very
weak interactions in the classical realm, and, in particular,
open a novel route to measuring the gravitational constant
with enhanced precision.