Prydeet al.Reply:

In our Letter we proposed a scheme for nondeterministic quantum nondemolition(QND) measurement of the polarization of a single photon--a photonicqubit--using linear optics and photodetection. The scheme works with nonunitprobability, but success is heralded by the detection of a single photon in themeter output. We provided an experimental demonstration of this scheme andintroduced three universally applicable fidelity measures--the measurementfidelity F_M, the quantum state preparation fidelity F_QSP, and the QNDfidelity F_QND--to quantify its performance. The claim of Kok and Munro intheir Comment [quant-ph/0406120] is that one of our fidelity measures F_M isnot appropriate because it relies on coincidence measurements. We show why thisclaim is wrong from both a fundamental and an operational perspective.Comment: 1 page, no figure