1,472 research outputs found
Imaging with a small number of photons
Low-light-level imaging techniques have application in many diverse fields,
ranging from biological sciences to security. We demonstrate a single-photon
imaging system based on a time-gated inten- sified CCD (ICCD) camera in which
the image of an object can be inferred from very few detected photons. We show
that a ghost-imaging configuration, where the image is obtained from photons
that have never interacted with the object, is a useful approach for obtaining
images with high signal-to-noise ratios. The use of heralded single-photons
ensures that the background counts can be virtually eliminated from the
recorded images. By applying techniques of compressed sensing and associated
image reconstruction, we obtain high-quality images of the object from raw data
comprised of fewer than one detected photon per image pixel.Comment: 9 pages, 4 figure
EPR-based ghost imaging using a single-photon-sensitive camera
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
Increasing the dimension in high-dimensional two-photon orbital angular momentum entanglement
Any practical experiment utilising the innate D-dimensional entanglement of
the orbital angular momentum (OAM) state space of photons is subject to the
modal capacity of the detection system. We show that given such a constraint,
the number of measured, entangled OAM modes in photon pairs generated by
spontaneous parametric down-conversion (SPDC) can be maximised by tuning the
phase-matching conditions in the SPDC process. We demonstrate a factor of 2
increase on the half-width of the OAM-correlation spectrum, from 10 to 20, the
latter implying \approx 50 -dimensional two-photon OAM entanglement. Exploiting
correlations in the conjugate variable, angular position, we measure
concurrence values 0.96 and 0.90 for two phase-matching conditions, indicating
bipartite, D-dimensional entanglement where D is tuneable
Resolution limits of quantum ghost imaging
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
Simultaneous real-time visible and infrared video with single-pixel detectors
Conventional cameras rely upon a pixelated sensor to provide spatial resolution. An alternative approach replaces the sensor with a pixelated transmission mask encoded with a series of binary patterns. Combining knowledge of the series of patterns and the associated filtered intensities, measured by single-pixel detectors, allows an image to be deduced through data inversion. In this work we extend the concept of a ‘single-pixel camera’ to provide continuous real-time video at 10 Hz , simultaneously in the visible and short-wave infrared, using an efficient computer algorithm. We demonstrate our camera for imaging through smoke, through a tinted screen, whilst performing compressive sampling and recovering high-resolution detail by arbitrarily controlling the pixel-binning of the masks. We anticipate real-time single-pixel video cameras to have considerable importance where pixelated sensors are limited, allowing for low-cost, non-visible imaging systems in applications such as night-vision, gas sensing and medical diagnostics
Experimental limits of ghost diffraction: Popper’s thought experiment
Quantum ghost diffraction harnesses quantum correlations to record diffraction or interference features using photons that have never interacted with the diffractive element. By designing an optical system in which the diffraction pattern can be produced by double slits of variable width either through a conventional diffraction scheme or a ghost diffraction scheme, we can explore the transition between the case where ghost diffraction behaves as conventional diffraction and the case where it does not. For conventional diffraction the angular extent increases as the scale of the diffracting object is reduced. By contrast, we show that no matter how small the scale of the diffracting object, the angular extent of the ghost diffraction is limited (by the transverse extent of the spatial correlations between beams). Our study is an experimental realisation of Popper’s thought experiment on the validity of the Copenhagen interpretation of quantum mechanics. We discuss the implication of our results in this context and explain that it is compatible with, but not proof of, the Copenhagen interpretation
Spectroscopic observation of the rotational Doppler effect
We report on the first spectroscopic observation of the rotational Doppler
shift associated with light beams carrying orbital angular momentum. The effect
is evidenced as the broadening of a Hanle/EIT coherence resonance on Rb vapor
when the two incident Laguerre-Gaussian laser beams have opposite topological
charges. The observations closely agree with theoretical predictions.Comment: Submited to Physical Review Lette
Submillimeter Structure of the Disk of the Butterfly Star
We present a spatially resolved 894 micron map of the circumstellar disk of
the Butterfly star in Taurus (IRAS 04302+2247), obtained with the Submillimeter
Array (SMA). The predicted and observed radial brightness profile agree well in
the outer disk region, but differ in the inner region with an outer radius of
~80-120 AU. In particular, we find a local minimum of the radial brightness
distribution at the center, which can be explained by an increasing density /
optical depth combined with the decreasing vertical extent of the disk towards
the center. Our finding indicates that young circumstellar disks can be
optically thick at wavelengths as long as 894 micron. While earlier modeling
lead to general conclusions about the global disk structure and, most
importantly, evidence for grain growth in the disk (Wolf, Padgett, &
Stapelfeldt 2003), the presented SMA observations provide more detailed
constraints for the disk structure and dust grain properties in the inner,
potentially planet-forming region (inside ~80-120 AU) vs. the outer disk region
(~120-300 AU).Comment: 6 pages, emulatepaj, Accepted to ApJ
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