Correlated imaging, quantum and classical

Abstract

We analytically show that it is possible to perform coherent imaging by using the classical correlation of two beams obtained by splitting incoherent thermal radiation. A formal analogy is demonstrated between two such classically correlated beams and two entangled beams produced by parametric down-conversion. Because of this analogy, the classical beams can mimic qualitatively all the imaging properties of the entangled beams, even in ways which up to now were not believed possible. A key feature is that these classical beams are spatially correlated both in the near field and in the far field. Using realistic numerical simulations the performances of a quasithermal and a parametric down-conversion source are shown to be closely similar, both for what concerns the resolution and statistical properties. The results of this paper provide a scenario for the discussion of what role the entanglement plays in correlated imaging

Unified theory of ghost imaging with Gaussian-state light

“…This is why biphoton sources yield background-free ghost images [2,5,6], despite SPDC being a broadband process.…”

“…This arrangement yielded a background-free image that was interpreted as a quantum phenomenon, owing to the entanglement of the source photons [2]. However, subsequent experimental * Electronic address: erkmen@mit.edu [3,4] and theoretical [5,6] considerations demonstrated that ghost imaging can be performed with thermalized laser light, utilizing either photon-counting detectors or CCD detector arrays to obtain ghost images, albeit with a background.…”

Single-pixel digital ghost holography

“…Later it was proved that many features obtained in a ghost imaging experiment could also be reproduced with a pseudothermal classical light source [16]. After two decades of intense debate, we now understand that it can be implemented with either quantum or classical sources, albeit with slightly distinct features [16][17][18][19][20][21]. Leaving aside * torresv@chalmers.se the quantum vs classical debate, the ghost appellative actually offers enormous possibilities for optical imaging hitherto not fully exploited.…”

Odd-order aberration cancellation in correlated-photon imaging

“…The results were similar to those with the entangled source, but with half the visibility. It has since been shown that spatial correlations present in radiation produced using thermal and speckle sources may also lead to ghost imaging ( [4][5][6][7][8][9]). …”

“…It has been a topic of great interest since its discovery using entangled photon pairs [1]. Initially, it was believed that the entanglement was a necessary ingredient for the effect, but it has since been found that most aspects of ghost imaging can be simulated using spatially-correlated classical light [2,3], including thermal and speckle sources [4][5][6][7][8][9].…”