Weak-measurement-induced asymmetric dephasing: manifestation of intrinsic measurement chirality

Abstract

Geometrical dephasing is distinct from dynamical dephasing in that it depends on the trajectory traversed, hence it reverses its sign upon flipping the direction in which the path is traced. Here we study sequences of generalized (weak) measurements that steer a system in a closed trajectory. The readout process is marked by fluctuations, giving rise to dephasing. Rather than classifying the latter as "dynamical" and "geometrical", we identify a contribution which is invariant under reversing the sequence ordering and, in analogy with geometrical dephasing, one which flips its sign upon the reversal of the winding direction, possibly resulting in partial suppression of dephasing (i.e., "coherency enhancement"). This dephasing asymmetry (under winding reversal) is a manifestation of intrinsic chirality, which weak measurements can (and generically do) possess. Furthermore, the dephasing diverges at certain protocol parameters, marking topological transitions in the measurement-induced phase factor.