Quantum and Classical Coincidence Imaging

Coincidence, or ghost, imaging is a technique that uses two correlated optical fields to form an image of an object. In this work we identify aspects of coincidence imaging which can be performed with classically correlated light sources and aspects which require quantum entanglement. We find that entangled photons allow high-contrast, high-resolution imaging to be performed at any distance from the light source. We demonstrate this fact by forming ghost images in the near and far fields of an entangled photon source, noting that the product of the resolutions of these images is a factor of 3 better than that which is allowed by classical diffraction theory.

Figure 1

(a) Setup used to perform coincidence diffraction with a classically correlated source. (b) The experimentally obtained diffraction pattern.

Figure 2

Experimental setups used to form coincidence images of a 2-bar mask in the near field (a),(c) and far field (b),(d) of an entangled light source. PBS: polarizing beam splitter; SF: spectral filter.

Figure 3

Experimental setups used to form coincidence images of a 2-bar mask in the near field (a),(c) and far field (b),(d) of a classically correlated light source.