Quantum and Classical Coincidence Imaging

Abstract

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.

Coherent imaging with pseudo-thermal incoherent light

“…In the same spirit, recent experimental works [7,9,10], brilliantly pointed out a momentum-position realization of the Einstein-PodolskyRosen (EPR) paradox using entangled photon pairs produced by PDC. The product of conditional variances in momentum and position was there shown to be below the EPR bound that limits the correlation of any classical (non-entangled) light beam.…”

“…While by now we know this is not true, at that time it was in partial agreement with [4] and [5]. When the Rochester group recently completed the results by showing that also the object diffraction pattern can be reconstructed using classically correlated beams [7], they had indeed to change the setup (the object location, the lens setup as well as the detection protocol).…”

“…As predicted, it was possible to pass from the image by only changing the optical setup in the reference arm, while leaving the object arm untouched. Moreover, the product of spatial resolutions of the ghost image and ghost diffraction experiments was there shown to overcome the EPR bound which was proposed to be achievable only with entangled photons by former literature [7,10]. The origin of the apparent contradiction with the former literature was there identified, by recognizing that the spatial resolution of GI protocols do not coincide in general with the conditional variance, so that the product of the near and far-field resolution is free from any EPR separability bound.…”

“…The product of conditional variances in momentum and position was there shown to be below the EPR bound that limits the correlation of any classical (non-entangled) light beam. Based on these results, the Authors of [7] proposed the same EPR bound as a limit for the product of the resolutions of the images formed in the near and in the far-field of a given classical source, and both [7,10] argued that in ghost imaging schemes entangled photons allow to achieve a better spatial resolution than any classically correlated beams.…”

Quantum Computation-Based Image Representation, Processing Operations and Their Applications

“…For the quantum image processing, a good deal of operations are done by relying on the corresponding processing in classical images, as [21,47]. The flexible representation for quantum images, FRQI [21,26], which is similar to the pixel representation for images on conventional computers, encodes the fundamental information (the colors and the corresponding positions) of an image and, in addition, integrates them into a quantum state, as presented in Equations (7) to (9).…”