Observable Measurement-Induced Transitions

Understand

One of the main postulates of quantum mechanics is that measurements destroy quantum coherence (wave function collapse).

• Recently it was discovered that in a many-body system dilute local measurements still preserve some coherence across the entire system.
• As the measurement density is increased, a phase transition occurs that is characterized by the disentanglement of different parts of the system.
• Unfortunately, this transition is impossible to observe experimentally for macroscopic systems because it requires an exponentially costly full tomography of the many-body wave function or a comparison with the simulation on an oracle classical computer.