Resolution limits of quantum ghost imaging

Abstract

Quantum ghost imaging uses photon pairs produced from parametric downconversion to enable an alternative method of image acquisition. Information from either one of the photons does not yield an image, but an image can be obtained by harnessing the correlations between them. Here we present an examination of the resolution limits of such ghost imaging systems. In both conventional imaging and quantum ghost imaging the resolution of the image is limited by the point-spread function of the optics associated with the spatially resolving detector. However, whereas in conventional imaging systems the resolution is limited only by this point spread function, in ghost imaging we show that the resolution can be further degraded by reducing the strength of the spatial correlations inherent in the downconversion process.

Imaging with quantum states of light

“…It was, however, later demonstrated that it is possible to perform ghost imaging by using a classical source which is a laser beam, deflected by a variable amount and then passed through a beam splitter [155] or thermal light split in two beams on a beam splitter [156]. Regarding the potential advantages of quantum versus classical ghost imaging, it is now recognized that these methods produce images of a similar resolution [157,158]. The main advantage of quantum light is found at low light levels, where it exhibits greater visibility and a greater signal to noise ratio [157,159].…”

“…These wavelengths have applications in biological, industrial, and security imaging applications in which raster scanning techniques using the aforementioned non-spatially resolved detectors are too slow in the construction of an image [167]. As for the resolution of non-degenerate ghost imaging, theoretical works indicate that the resolution does not lead to improvement over the classical methods [168,169]; also the resolution will still be limited by the point spread function of the imaging system and may be degraded by reducing the strength of correlation between the photon pairs [158]. Finally, quantum correlated sources have been used to perform ghost acquisitions in other domains.…”

Perspectives for Applications of Quantum Imaging

“…Early demonstrations of QGI with degenerate photon pairs seemed to demonstrate an enhanced resolution with respect to classical imaging using the wavelength of the photon pairs . However, theoretical works concluded, that the resolution cannot be better than the one given by the wavelength of the photon pair, and is usually worse due to finite‐sized pump beams and crystal lengths, which was recently shown also experimentally . This can be intuitively understood in the Klyshko representation, where the pumped nonlinear crystal is just another aperture, which can influence the resolution only by degrading it.…”

“…Furthermore, the intensifier can be gated for very short times in the ns range, making these cameras suitable for photon correlation experiments. Hence, ICCDs were already massively harnessed for quantum imaging research; for instance, detection of spatial correlations of SPDC photon pairs, ghost imaging, and few photon imaging . Nevertheless, as the final detection is still based on a comparably slow CCD or CMOS sensor, measurements of the photon arrival time are not possible.…”

Experimental Limits of Ghost Diffraction: Popper’s Thought Experiment

“…Recently we have performed an experimental comparison of the resolution of conventional imaging and ghost imaging 17 . In that work we showed that whilst in the case of conventional imaging the resolution is largely independent of the source characteristics, in the ghost-imaging configuration the resolution of the resulting image is strongly dependent on the transverse extent of the correlations produced by the down-conversion source.…”