Ghost Imaging with Thermal Light: Comparing Entanglement and Classical Correlation. A. Gatti, E. Brambilla, M. Bache and L. A. Lugiato in Phys. Rev. Lett. 93:093602 (2004). What the paper says!?
This paper makes the quite remarkable observation that substituting entangled light in ghost imaging by thermal light, still works!
This follows some debate on the question:
Currently there is a debate whether quantum entanglement is necessary to perform ghost imaging [3–6].
as well as previous demonstrations of similar downgrade to classical light.[1] Some special status seems to still have been conceded to quantum light in those previous works. However, ere, the authors:
In contrast to this, we will show here that the spatial correlation of the two beams produced by splitting thermal light, although being completely classical, is enough to mimic qualitatively all the features of entangled imaging, even in ways which were not believed possible before.
Their main result—presented as such by them—is
which is contrasted to the PDC counterpart:
For the imaging itself, on the one hand, assuming $z=f$:
and on the other hand, assuming $z=2f$:
to be compared to
In this example the correlation function provides information about the image of the object. A similar result holds for the case of entangled beams [see Eq. (8) of [4] ].
Duality between partial coherence and partial entanglement. B. Saleh, A. Abouraddy, A. Sergienko and M. Teich in Phys. Rev. A 62:043816 (2000).
This paragraph seems to be as important as it is unclear:
and so is the next paragraph on intensities. At high intensities, thermal light is as efficient than PDC one. But is there a higher gain at low photon numbers that thermal light cannot catch up with, or it doesn't matter and it can stay at high intensity and substitute entangled light?
in the small photon number regime, a definite advantage of the quantum configuration is represented by a better visibility.
This has a longer companion[2] which probably is more enlightening, as well as follow-up works.[3]
Particularly interesting are the controversies that followed.[[4],[5]] See also the analysis by Shapiro[6].
- ↑ "Two-Photon" Coincidence Imaging with a Classical Source. R. S. Bennink, S. J. Bentley and R. W. Boyd in Phys. Rev. Lett. 89:113601 (2002).
- ↑ Correlated imaging, quantum and classical. A. Gatti, E. Brambilla, M. Bache and L. Lugiato in Phys. Rev. A 70:013802 (2004).
- ↑ High-Resolution Ghost Image and Ghost Diffraction Experiments with Thermal Light. F. Ferri, D. Magatti, A. Gatti, M. Bache, E. Brambilla and L. Lugiato in Phys. Rev. Lett. 94:183602 (2005).
- ↑ Can Two-Photon Correlation of Chaotic Light Be Considered as Correlation of Intensity Fluctuations?. G. Scarcelli, V. Berardi and Y. Shih in Phys. Rev. Lett. 96:063602 (2006).
- ↑ Comment on “Can Two-Photon Correlation of Chaotic Light Be Considered as Correlation of Intensity Fluctuations?”. A. Gatti, M. Bondani, L. Lugiato, M. Paris and C. Fabre in Phys. Rev. Lett. 98:039301 (2007).
- ↑ Computational ghost imaging. J. Shapiro in Phys. Rev. A 78:061802 (2008).