Post-selected quantum metrology in noisy settings

Post-selected quantum metrology allows detectors to operate at lower intensities without reducing the input rate of quantum information. Until now, the effect of noise on such metrology has not been investigated. In my talk I will prove that post-selection can always increase the (Fisher) information per output state, even in the presence of strong depolarising noise. The extent of the possible information compression depends on the strength of the noise. I present analytical formulae pinning down this relation. My derivation holds in the case of multi-parameter quantum metrology and post-selection by a general filter (i.e., POVM). Finally, I design the optimal filter to use in noisy post-selected quantum metrology.