Quantum Disturbance without State Change: Defense of State-Dependent Error-Disturbance Relations

The uncertainty principle states that a measurement inevitably disturbs the system, while it is often supposed that a quantum system is not disturbed without state change. Korzekwa, Jennings, and Rudolph [Phys. Rev. A 89, 052108 (2014)] pointed out a conflict between those two views, and concluded that state-dependent formulations of error-disturbance relations are untenable. Here, we reconcile the conflict by showing that a quantum system is disturbed without state change, in favor of the recently obtained universally valid state-dependent error-disturbance relations.