Weak monitoring boosts quantum correlations, strong monitoring changes state

Researchers have discovered that a specific type of many-body system exhibits behavior akin to flocking when monitored, a surprising result given such systems typically produce only weak quantum signatures in stable states. Jacob F. Steiner, Felix von Oppen, and Reinhold Egger report finding power-law quantum correlations between spin density and charge current for weak monitoring strengths and ferromagnetic spin interactions, identifying this as a hallmark of the phenomenon. The work demonstrates that monitoring strength has a dual role, generating these quantum correlations when weak but driving a Berezinskii-Kosterlitz-Thouless phase transition to a short-range correlated state at larger strengths. A specific type of quantum system, the spinful Luttinger liquid, demonstrates behavior reminiscent of flocking birds when subjected to observation, even though traditionally such systems yield only faint quantum…