(\[input\_result\]) and (\[output\_result\]) seems to indicate that a measurement after projection in any basis, the core element of the weak amplification scheme, provides no fundamental metrological advantage. Notice that this result implies that the only relevant factor limiting the sensitivity of detection is the quantum nature of the light used (a [*coherent state*]{} in our case). To obtain this result, we are implicitly assuming that a) we have full access to all relevant characteristics of the output signals; and b) detectors are ideal, and can detect any change, as small as it might be, if enough signal power is used. If this is the case, weak value amplification provides no enhancement of the sensitivity.

However, this can be far from truth in many realistic experimental situations. In the laboratory, the quantum nature of light is an important factor, but not the only one, limiting the capacity to measure tiny changes of variables of interest. On the one hand, most of the times we detect only certain characteristic of the output signals, probably the most relevant, but this is still partial information about the quantum state. On the other hand, detectors are not ideal and noteworthy limitations to its performance can 