No Arabic abstract
Ghost imaging is the remarkable process where an image can be formed from photons that have not seen the object. Traditionally this phenomenon has required initially correlated but spatially separated photons, e.g., one to interact with the object and the other to form the image, and has been observed in many physical situations, spanning both the quantum and classical regimes. To date, all instances of ghost imaging record an image with the same contrast as the object, i.e., where the object is bright, the image is also bright, and vice versa. Here we observe ghost imaging in a new system - a system based on photons that have never interacted. We utilise entanglement swapping between independent pairs of spatially entangled photons to establish position correlations between two initially independent photons. As a consequence of an anti-symmetric projection in the entanglement swapping process, the recorded image is the contrast reversed version of the object, i.e., where the object is bright, the image is dark, and vice versa. The results highlight the importance of state projection in this ghost imaging process and provides a pathway to teleporting images across a quantum network.
Non-local point-to-point correlations between two photons have been used to produce ghost images without placing the camera towards the object. Here we theoretically demonstrated and analyzed the advantage of non-Gaussian quantum light in improving the image quality of ghost imaging system over traditional Gaussian light source. For any squeezing degree, the signal-to-noise ratio (SNR) of the ghost image can be enhanced by the non-Gaussian operations of photon addition and subtraction on the two-mode squeezed light source. We find striking evidence that using non-Gaussian coherent operations, the SNR can be promoted to a high level even within the extremely weak squeezing regime. The resulting insight provides new experimental recipes of quantum imaging using non-Gaussian light for illumination.
Enhancing optical nonlinearities so that they become appreciable on the single photon level and lead to nonclassical light fields has been a central objective in quantum optics for many years. After this has been achieved in individual micro-cavities representing an effectively zero-dimensional volume, this line of research has shifted its focus towards engineering devices where such strong optical nonlinearities simultaneously occur in extended volumes of multiple nodes of a network. Recent technological progress in several experimental platforms now opens the possibility to employ the systems of strongly interacting photons these give rise to as quantum simulators. Here we review the recent development and current status of this research direction for theory and experiment. Addressing both, optical photons interacting with atoms and microwave photons in networks of superconducting circuits, we focus on analogue quantum simulations in scenarios where effective photon-photon interactions exceed dissipative processes in the considered platforms.
In quantum mechanics, entanglement and correlations are not just a mere sporadic curiosity, but rather common phenomena at the basis of an interacting quantum system. In electron microscopy, such concepts have not been extensively explored yet in all their implications; in particular, inelastic scattering can be reanalyzed in terms of correlation between the electron beam and the sample. While classical inelastic scattering simply implies loss of coherence in the electron beam, performing a joint measurement on the electron beam and the sample excitation could restore the coherence and the lost information. Here, we propose to exploit joint measurement in electron microscopy for a surprising and counter-intuitive application of the concept of ghost imaging. Ghost imaging, first proposed in quantum photonics, can be applied partially in electron microscopy by performing joint measurement between the portion of the transmitted electron beam and a photon emitted from the sample reaching a bucket detector. This would permit us to form a one-dimensional virtual image of an object that even has not interacted with the electron beam directly. This technique is extremely promising for low-dose imaging that requires the minimization of radiation exposure for electron-sensitive materials, because the object interacts with other form of waves, e.g., photons/surface plasmon polaritons, and not the electron beam. We demonstrate this concept theoretically for any inelastic electron-sample interaction in which the electron excites a single quantum of a collective mode, such as a photon, plasmon, phonon, magnon, or any optical polariton.
Plasmonics and metamaterials have recently been shown to allow the control and interaction with non-classical states of light, a rather counterintuitive finding given the high losses typically encountered in these systems. Here, we demonstrate a range of functionalities that are allowed with correlated and entangled photons that are used to illuminate multiple, overlaid patterns on plasmonic metasurfaces. Correlated photons allow to nonlocally determine the pattern that is imaged or, alternatively to un-scramble an image that is otherwise blurred. Entangled photons allow a more important functionality whereby the images imprinted on the metasurface are individually visible only when illuminated with one of the entangled photons. Correlated single photon imaging of functional metasurfaces could therefore promise advances towards the use of nanostructured subwavelength thin devices in quantum information protocols.
High-resolution ghost image and ghost diffraction experiments are performed by using a single source of thermal-like speckle light divided by a beam splitter. Passing from the image to the diffraction result solely relies on changing the optical setup in the reference arm, while leaving untouched the object arm. The product of spatial resolutions of the ghost image and ghost diffraction experiments is shown to overcome a limit which was formerly thought to be achievable only with entangled photons.