Shaping global behaviour by local dynamical interventions: Classical and Quantum

by Rupak Majumder (TIFR Mumbai India)

Wednesday 7 Oct 2026, 14:30 → 15:30 Europe/Rome

Many-body systems can exhibit qualitatively distinct phases, and their dynamics may drive them toward a macroscopic state that is not necessarily the one we desire. This raises a natural question: Can we steer a many-body system from an undesired phase or state to a desired one through occasional local dynamical interventions, without modifying the underlying interactions? In classical settings, we explore this question in a variety of spin and nonlinear oscillator models, spanning equilibrium and nonequilibrium systems, mean-field and non-mean-field interactions, and systems with and without quenched disorder. We show that by occasionally resetting a part of the system to a desired configuration, we can control the macroscopic phase transitions of the system. By tuning a few control parameters, namely, the size of the subsystem being reset, the resetting rate, and the configuration to which it is reset, we can not only shift transition points but also alter the nature of the transitions. In quantum settings, the goal is more specific: Can we create a desired quantum state through occasional local interventions? We show that interrupting the dynamics through measurement and postselection, even at a single site, is sufficient to reshape the dynamics and guide the system toward a desired state. Together, these examples illustrate how local interventions can provide a general route to controlling global behaviour in both classical and quantum many-body systems, without directly modifying the underlying interactions.

References:

[1] Physical Review E 109(6), 064137 (2024)
[2] Physical Review Letters 135 (12), 127103 (2025)
[3] Physical Review E 114 (2), 024108 (2026)
[4] To appear