  Pushing forward the understanding of general non-unitary dynamics in
controlled quantum platforms has been fueled by the recent discovery of
measurement-induced phases and phase transitions. So far, these transitions
remained largely elusive, since they are masked in standard quantum mechanical
observables due to the randomness of measurement outcomes. Here, we establish a
general scheme -- pre-selection -- to make them observable: The outcome
randomness is broken explicitly by steering the system towards a representative
state, which corresponds to one out of exponentially many possible measurement
outcomes. Remarkably, this steering can be chosen so gently that the basic
properties of the underlying measurement-induced transition, such as
entanglement structure and critical exponents, are not modified. Pre-selection
introduces a unique dark or absorbing state with macroscopic order, replacing
the maximally mixed stationary state of the unconditioned measurement
trajectory ensemble. This creates a link of measurement-induced phase
transitions to new forms of quantum absorbing state transitions, which can be
detected by standard means via a local order parameter. This insight further
enables a quantum simulation strategy, determining the underlying universality
class in state-of-the-art quantum platforms without measurement readout.
