- Open Access
Causality, localization, and universality of monitored quantum walks with long-range hopping
Phys. Rev. E 112, 044146 – Published 27 October, 2025
DOI: https://doi.org/10.1103/rbtb-8d27
Abstract
A powerful strategy to accelerate quantum-walk-based search algorithms leverages on resetting protocols, where a detector monitors a target site and the evolution of the walker is restarted if no detection occurs within a fixed time interval. The optimal resetting rate can be extracted from the time evolution of the probability that the detector has not clicked up to time . We analyze for a quantum walk on a one-dimensional lattice when the coupling between sites decays algebraically as with the distance , for . At long times, decays with a universal power-law exponent that is independent of . At short times, exhibits a plethora of phase transitions as a function of . From this, we provide a strategy to determine the optimal resetting rate. We identify two regimes: for , the resetting rate is bounded from below by the velocity with which information propagates causally across the lattice; for , instead, the long-range hopping tends to localize the walker: The optimal resetting rate depends on the size of the lattice and diverges as . Our strategy directly connects local measurement outcomes with the global dynamics encoded in . We derive simple models explaining our numerical results, shedding light on the interplay of long-range coherent dynamics, symmetries, and local quantum measurement processes in determining equilibrium. Our findings offer experimentally testable predictions and provide new physical insights on optimizing quantum search through resetting.
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