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Physical Review A

Discriminating orthogonal single-photon images

Curtis J. Broadbent, Petros Zerom, Heedeuk Shin, John C. Howell, Robert W. Boyd

Published Mar 4, 2009• 27 citations
Publisher

Abstract

We can encode an image from an orthogonal basis set onto a single photon from a downconverted pair via the use of an amplitude mask. We can then discriminate the image imprinted on the photon from other images in the set using holographic-matched filtering techniques. We demonstrate this procedure experimentally for an image space of two objects, and we discuss the possibility of applying this method to a much larger image space. This process could have important implications for the manipulation of images at the quantum level.

DOI
10.1103/physreva.79.033802

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We can encode an image from an orthogonal basis set onto a single photon from a downconverted pair via the use of an amplitude mask. We can then discriminate the image imprinted on the photon from other images in the set using holographic-matched filtering techniques. We demonstrate this procedure experimentally for an image space of two objects, and we discuss the possibility of applying this method to a much larger image space. This process could have important implications for the manipulation of images at the quantum level.
Ghost imaging can be performed using either quantum or classical states of light that possess strong spatial correlations. In both cases, the image is formed by averaging over many optical events. Here we show that it is possible to distinguish an object from a preestablished basis set of objects by using a small number of position-correlated photon pairs produced by spontaneous parametric down-conversion. The signal photon is incident on one member of a set of spatially nonoverlapping objects. The "ghost" image information is impressed upon the spatially separated idler photon and is extracted by means of holographic filtering and coincidence detection. We were able to distinguish among sets of two and four spatially nonoverlapping objects with confidence levels higher than 87% and 81%, respectively. This method of ghost imaging can be performed in situations requiring extremely low light levels.
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We report the experimental observation of quantum holographic imaging of one-dimensional object with entangled photon pairs, generated in a spontaneous parametric down-conversion process. The signal photons play both roles of “object wave” and “reference wave” in holography but are recorded by a point detector providing only encoding information, while the idler photons travel freely and are locally manipulated with spatial resolution. The holographic image is formed by the two-photon correlation measurement, although both the signal and idler beams are incoherent. Three types of quantum holography schemes are analyzed according to the detection regime of the signal photons.
We outline and experimentally demonstrate a method to image pure phase objects using traditional quantum ghost imaging with single pixel detectors. We provide a theoretical description of the process, showing how phase information is embedded in the correlation measurements of spatially entangled photon pairs in which only one of the pair interacts with the object. Using pairs of digital projective masks, one amplitude-only and one phase-only, we reconstruct two partial phase images of the object. Using both these images, we can retrieve the full detailed phase profile of the object without ambiguity, which we demonstrate on objects exhibiting phase steps and gradients.
Photon-pair correlations in spontaneous parametric down conversion (SPDC) processes are ubiquitous in quantum photonics. In this work, we engineer these correlations by imaging arbitrarily chosen objects in the second order correlations of spatially-entangled photon pairs produced by type-I SPDC in a non-linear crystal. Our approach is effective with both amplitude and phase objects, even when the beam intensity is spatially shaped. Additionally, we show that it is resistant to scattering by applying wavefront shaping techniques. We also find that certain phase patterns can refocus through the scattering medium exclusively with photon pairs, and not with classical coherent light. Consequently, the transmission of an image through the scattering medium is only possible if it is correlation encoded; coherent light alone cannot reconstruct the image. Our approach enables the transmission of complex, high-dimensional information using quantum correlations of photons, offering significant potential for advancing quantum communication and imaging protocols.