Quantum entanglement between particles is expected to allow one to perform
tasks that would otherwise be impossible. In quantum sensing and metrology,
entanglement is often claimed to enable a precision that cannot be attained
with the same number of particles and time, forgoing entanglement. Two distinct
approaches exist: creation of entangled states that either i) respond quicker
to the signal, or ii) are associated with lower noise and uncertainty. The
second class of states are generally called squeezed states. Here we show that
if our definition of success is -- a precision that is impossible to achieve
without entanglement -- then the second approach cannot succeed. In doing so we
show that a single non-separable squeezed state provides fundamentally no
better precision, per unit time, than a single particle