Trade-off between information gain and fidelity under weak measurements
Longfei Fan, Wenchao Ge, Hyunchul Nha, Muhammad Suhail Zubairy · Physical Review A · 2015
It is of general interest how a quantum measurement may disturb a quantum system while it gives information on the state of the system. We study a trade-off relation between the information gain and the output fidelity for a quantum nondemolition measurement scheme for photon numbers. Toward this aim, we obtain general expressions for the information gain and the output fidelity for an arbitrary initial state. We particularly investigate how these two quantities vary with measurement strength for some specific classes of states, through a single measurement or successive measurements.