Commercially available cameras do not have a low-enough dark noise to directly capture double-slit interference at the single photon level. In this work, camera noise levels are significantly reduced by activating the camera only when the presence of a photon has been detected by the independent detection of a time-correlated photon produced via parametric down-conversion. This triggering scheme provides the improvement required for direct video imaging of Young's double-slit experiment with single photons, allowing clarified versions of this foundational demonstration. We present video data of the evolving interference patterns. Also, we introduce variations on this experiment aimed at promoting discussion of the role spatial coherence plays in such a measurement, emphasizing complementary aspects of single-photon measurement and highlighting the roles of transverse position and momentum correlations between down-converted photons, including examples of “ghost” imaging and diffraction.
Commercially available cameras do not have a low-enough dark noise to directly capture double-slit interference at the single photon level. In this work, camera noise levels are significantly reduced by activating the camera only when the presence of a photon has been detected by the independent detection of a time-correlated photon produced via parametric down-conversion. This triggering scheme provides the improvement required for direct video imaging of Young's double-slit experiment with single photons, allowing clarified versions of this foundational demonstration. We present video data of the evolving interference patterns. Also, we introduce variations on this experiment aimed at promoting discussion of the role spatial coherence plays in such a measurement, emphasizing complementary aspects of single-photon measurement and highlighting the roles of transverse position and momentum correlations between down-converted photons, including examples of “ghost” imaging and diffraction.
The interference of single photons going through a double slit is a compelling demonstration of the wave and particle nature of light in the same experiment. Single photons produced by spontaneous parametric down-conversion can be used for this purpose. However, it is particularly challenging to implement this due to coherency and resolution challenges. In this article, we present a table-top laboratory arrangement suitable for the undergraduate instruction laboratory that overcomes these challenges. The apparatus scans a single detector to produce a plot showing the interference patterns of single photons. We include experimental data obtained using this setup, demonstrating double-slit and single-slit interference as well as quantum erasing through the use of sheet polarizers.
Correlated photon imaging, popularly known as ghost imaging, is a technique whereby an image is formed from light that has never interacted with the object. In ghost imaging experiments, two correlated light fields are produced. One of these fields illuminates the object, and the other field is measured by a spatially resolving detector. In the quantum regime, these correlated light fields are produced by entangled photons created by spontaneous parametric down-conversion. To date, all correlated photon ghost imaging experiments have scanned a single-pixel detector through the field of view to obtain spatial information. However, scanning leads to poor sampling efficiency, which scales inversely with the number of pixels, N , in the image. In this work, we overcome this limitation by using a time-gated camera to record the single-photon events across the full scene. We obtain high-contrast images, 90%, in either the image plane or the far field of the photon pair source, taking advantage of the Einstein–Podolsky–Rosen-like correlations in position and momentum of the photon pairs. Our images contain a large number of modes, >500, creating opportunities in low-light-level imaging and in quantum information processing.
Correlated-photon imaging, popularly known as ghost imaging, is a technique whereby an image is formed from light that has never interacted with the object. In ghost imaging experiments two correlated light fields are produced. One of these fields illuminates the object, and the other field is measured by a spatially resolving detector. In the quantum regime, these correlated light fields are produced by entangled photons created by spontaneous parametric down-conversion. To date, all correlated-photon ghost-imaging experiments have scanned a single-pixel detector through the field of view to obtain the spatial information. However, scanning leads to a poor sampling efficiency, which scales inversely with the number of pixels, N, in the image. In this work we overcome this limitation by using a time-gated camera to record the single-photon events across the full scene. We obtain high-contrast images, 90%, in either the image plane or the far-field of the photon pair source, taking advantage of the EPR-like correlations in position and momentum of the photon pairs. Our images contain a large number of modes, >500, creating opportunities in low-light-level imaging and in quantum information processing.
In this work we discuss topics such as the theory of photon detectors, showing its operation mode, characteristics and types. In addition, we also study the quantum detection theory, how photons interact with the detector's atoms, and how the process of single and coincidences counting mode works. We look into the theory of parametric down conversion in order to create a correlated photon source and a single photon source. We also discuss about ghost imaging theory and experiments, since it shows us in a very clear way a direct appplication for a single photons camera. I present the results obtained so far with the camera we have in our laboratory. We detected the photon's cones generated by the parametric down conversion type I and type II. We recorded interference patterns, multiple slit images, and amplitude masks images with few photons. We used the CCD for photon counting in an experiment where an image of an object is obtained through photons that have not interacted with the object, but is part of one of the beams in the stimulated parametric down conversion. One of the great motivators of working with a camera is performing quantum optics experiments where spatial patterns are detected. In this aspect a camera has a greater robustness than single photon APD since it allows us to observe the whole transverse profile of a beam simultaneously, something that is possible only with a set of detectors APDs.
Double-slit interference experiments using monochromatic hard X-rays with the energy of 25 keV are presented. The experiments were performed at a synchrotron source with a distance of 110 m between the interferometer and the detector to produce an interference pattern with a sufficiently broad period that could be adequately sampled by a photon-counting detector with 75 micrometre pixels. In the single-particle version of the experiment, over one million image frames with a single registered photon in each one were collected. The sum of these frames showed a clear presence of the interference pattern with the expected period. Subsequent analysis provided an objective estimation of the minimal number of detected photons required to determine, in accordance with the Rose criterion, the presence of the photon interference. Apart from a general theoretical interest, these investigations were aimed at exploring the possibility of medical X-ray phase-contrast imaging in photon-counting regime at minimal radiation doses.
This article reports a study on a turbulence-free Young's double-slit interferometer. When the environmental turbulence blurs out the classic Young's double-slit interference completely, a two-photon interference pattern is still observable from the measurement of intensity or photon number fluctuation correlation. This two-photon interferometer always produces a turbulence-free interference pattern, when the double-slit interferometer is utilizing both first-order spatially incoherent light and spatially coherent light. This type of two-photon interferometer establishes new capabilities in optical observations and sensing measurements that require high sensitivity and stability.