Ghost imaging with engineered quantum states by Hong-Ou-Mandel interference

Traditional ghost imaging experiments exploit position correlations between correlated states of light. These correlations occur directly in spontaneous parametric down-conversion (SPDC), and in such a scenario, the two-photon state used for ghost imaging is symmetric. Here we perform ghost imaging using an anti-symmetric state, engineering the two-photon state symmetry by means of Hong-Ou-Mandel interference. We use both symmetric and anti-symmetric states and show that the ghost imaging setup configuration results in object-image rotations depending on the state selected. Further, the object and imaging arms employ spatial light modulators for the all-digital control of the projections, being able to dynamically change the measuring technique and the spatial properties of the states under study. Finally, we provide a detailed theory that explains the reported observations.Comment: Published version. 19 pages, 5 figure

Near-perfect measuring of full-field transverse-spatial modes of light

Along with the growing interest in using the transverse-spatial modes of light in quantum and classical optics applications, developing an accurate and efficient measurement method has gained importance. Here, we present a technique relying on a unitary mode conversion for measuring any full-field transverse-spatial mode. Our method only requires three consecutive phase modulations followed by a single mode fiber and is, in principle, error-free and lossless. We experimentally test the technique using a single spatial light modulator and achieve an average error of 4.2% for a set of 9 different full-field Laguerre-Gauss and Hermite-Gauss modes with an efficiency of up to 70%. Moreover, as the method can also be used to measure any complex superposition state, we demonstrate its potential in a quantum cryptography protocol and in high-dimensional quantum state tomography.Comment: 7 pages, 4 figure

Spatial structuring of light for undergraduate laboratory

In recent times, spatial light modulators have become a common tool in optics laboratories as well as industrial environment to shape the spatial structure of a beam. Although these devices are often easy to use, they usually come at a high cost such that they are far from being implemented in a lot of undergraduate laboratories. However, over the last years, the progress in developing more cost-effective projectors has led to affordable spatial light modulators in the form of so-called Digital Micromirror Devices (DMD). This reduction in price, as well as their simple usage, make such devices increasingly suitable for undergraduate laboratories to demonstrate optical effects and the shaping of light fields. Here, we show one of the most cost-effective ways to make a DMD available, namely turning a projector evaluation module into a computer-controlled spatial light modulator. We explain the underlying functioning and how this low-cost spatial light modulator can be used in undergraduate laboratories. We further characterize the efficiency of the device for the most commonly used laser wavelengths and demonstrate various exemplary optics experiments suitable for undergraduate laboratories ranging from single and multi-slit diffraction, to optical Fourier transformations. Lastly, we show that using amplitude holography, the device can be used to generate transverse spatial modes, e.g. Laguerre-Gaussian beam, which are one of the most commonly used spatially structured beams.Comment: 12 pages, 8 figure

Violation of Bell's inequality for phase singular beams

We have considered optical beams with phase singularity and experimentally verified that these beams, although being classical, have properties of two mode entanglement in quantum states. We have observed the violation of Bell's inequality for continuous variables using the Wigner distribution function (WDF) proposed by Chowdhury et al. [Phys. Rev. A \textbf{88}, 013830 (2013)]. Our experiment establishes a new form of Bell's inequality in terms of the WDF which can be used for classical as well as quantum systems.Comment: 7 pages, 9 figures and 1 tabl