Implementing a single-photon quantum nondemolition device with only linear optics and projective measurements
Pieter Kok, Hwang Lee, Jonathan P. Dowling · arXiv (Cornell University) · 2002
In this Letter we describe an optical interferometer that signals the presence of a single photon in a particular input state (c0 |0> + c1 |1> + c2 |2>) without destroying it. The interferometer employs two auxiliary single-photon sources and three detectors. The ideal efficiency of this quantum nondemolition (QND) device is 1/7. Furthermore, the interferometer presented is in principle not bound to a specific frequency range.