. Usually, however, the entangled and separable state preparation and readout times are assumed to be negligible. We find that a probe in a maximally entangled (GHZ) state can give an advantage over a separable state only if the entangled state preparation and readout times are lower than a certain threshold. When the probe system suffers dephasing, this threshold is much lower (and more difficult to attain) than it is for an isolated probe. Further, we find that in realistic situations the maximally entangled probe gives a precision advantage only up to some finite number of probe particles

{N}_{\text{cutoff}}

that is lower for a dephasing probe than it is for an isolated probe.

DOI: 10.1103/physreva.94.052320

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N

{N}_{\text{cutoff}}

that is lower for a dephasing probe than it is for an isolated probe.

N

{N}_{\text{cutoff}}

that is lower for a dephasing probe than it is for an isolated probe.