Information flow in entangled quantum systems

All information in quantum systems is, notwithstanding Bell's theorem, loca lized. Measuring or otherwise interacting with a quantum system S has no ef fect on distant systems from which S is dynamically isolated, even if they are entangled with S. Using the Heisenberg picture to analyse quantum infor mation processing makes this locality explicit, and reveals that under some circumstances (in particular, in Einstein-Podolsky-Rosen experiments and i n quantum teleportation), quantum information is transmitted through 'class ical' (i.e. decoherent) information channels.