Figure 1
From: Experimental violation and reformulation of the Heisenberg's error-disturbance uncertainty relation
Indirect measurement model for A-measurement with detection of B-disturbance.
The probe initialized in the state |ξ〉 is introduced in the apparatus to make an indirect measurement of an observable A in the state |ψ〉 by interacting with the system through a unitary U. The meter observable M in the probe is precisely measured after the interaction to obtain the measurement outcome, which is used for estimating the error 
. Another observable B is also precisely measured after the interaction to obtain the data for estimating the disturbance η(B).
