“Two-Photon” Coincidence Imaging with a Classical Source

Coincidence imaging is a technique that extracts an image of a test system from the statistics of photons transmitted by a reference system when the two systems are illuminated by a source possessing appropriate correlations. It has recently been argued that quantum entangled sources are necessary for the implementation of this technique. We show that this technique does not require entanglement, and we provide an experimental demonstration of coincidence imaging using a classical source. We further find that any kind of coincidence imaging technique which uses a “bucket” detector in the test arm is incapable of imaging phase-only objects, whether a classical or quantum source is employed.

Figure 1

(adapted from 12) Two-photon coincidence imaging. The transfer function of the test system is to be obtained from the joint detection statistics using knowledge of the reference system.

Figure 2

The experimental setup used to perform coincidence imaging with a classically correlated source (shaded box).

Figure 3

The image formed in the reference arm when gated by the detector in the test arm. Such an image corresponds to the marginal probability distribution.