Entanglement Steering in Adaptive Circuits with Feedback

Understand

The intensely studied measurement-induced entanglement phase transition has become a hallmark of non-unitary quantum many-body dynamics.

• Usually, such a transition only shows up at the level of each individual quantum trajectory, and is absent for the density matrix averaged over measurement outcomes.
• In this work, we introduce a class of adaptive random circuit models with feedback that exhibit transitions in both settings.
• After each measurement, a unitary operation is either applied or not depending on the measurement outcome, which steers the averaged density matrix towards a unique state above a certain measurement threshold.