Probing vortex beams based on Talbot effect with two overlapping gratings

In a prior report the optical vortex was characterized using the near-field Talbot effect [1, 2]. This near-field technique can resolve both order and charge of the orbital angular momentum state of the vortex beam. We have proposed before that a small open fraction of the grating in the Talbot configuration can improve the image contrast [3]. In this study, we combine these previously reported techniques, i.e. the Talbot effect for probing an optical vortex and overlapping gratings to manipulate the open fraction. Both theoretical simulation and experimental demonstration are presented here. We believe that our technique can be an alternative method for optical vortex imaging, and could be useful in optical applications.

Quantum discord of thermal two-photon orbital angular momentum state: mimicking teleportation to transmit an image

We formulate a density matrix to fully describe two-photon state within a thermal light source in the photon orbital angular momentum (OAM) Hilbert space. We prove the separability, i.e., zero entanglement of the thermal two-photon state. Still, we reveal the hidden quantum correlations in terms of geometric measures of discord. By mimicking the original protocol of quantum teleportation, we demonstrate that the non-zero quantum discord can be utilized to transmit a high-dimensional OAM state at the single-photon level. It is found that albeit the low fidelity of teleportation due to the inherent component of maximally mixed state, the information of all parameters that characterize the original state can still be extracted from the teleported one. Besides, we demonstrate that the multiple repetitions of the protocol, enable the transmission of a complex-amplitude light field, e.g., an optical image, regardless of being accompanied with a featureless background. We also distinguish our scheme of optical image transmission from that of ghost imaging.

Super-Hawking radiation

We discuss modifications to the Hawking spectrum that arise when the asymptotic states are supertranslated or superrotated. For supertranslations we find nontrivial off-diagonal phases in the two-point correlator although the emission spectrum is eventually left unchanged, as previously pointed out in the literature. In contrast, superrotations give rise to modifications which manifest themselves in the emission spectrum and depend nontrivially on the associated conformal factor at future null infinity. We study Lorentz boosts and a class of superrotations whose conformal factors do not depend on the azimuthal angle on the celestial sphere and whose singularities at the north and south poles have been associated to the presence of a cosmic string. In spite of such singularities, superrotations still lead to finite spectral emission rates of particles and energy which display a distinctive power-law behavior at high frequencies for each angular momentum state. The integrated particle emission rate and emitted power, on the contrary, while finite for boosts, do exhibit ultraviolet divergences for superrotations, between logarithmic and quadratic. Such divergences can be ascribed to modes with support along the cosmic string. In the logarithimic case, corresponding to a superrotation which covers the sphere twice, the total power emitted still presents the Stefan-Boltzmann form but with an effective area which diverges logarithmically in the ultraviolet.

Possible dual bubble-like structure predicted by the relativistic Hartree–Bogoliubov model

Experimental observation of [Formula: see text]Si as a proton bubble nuclei has heated up the interest in the study of exotic bubble shaped nuclei. In this work, some of the potential doubly bubble-like (for proton as well as neutron both simultaneously) cases have been explored using relativistic Hartree–Bogoliubov (RHB) in light mass region, specially around N or [Formula: see text]. Further, the role of pairing and the evolution of new shell gaps around [Formula: see text] or [Formula: see text] and 34 have been investigated, as one moves toward drip lines. This study suggests that the occupancies/vacancies of neutron/proton orbitals for lower angular momentum state plays major role in nuclear structure to create bubble-like structure and [Formula: see text]O[Formula: see text], [Formula: see text]Mg8 and [Formula: see text]Si[Formula: see text] may have dual bubble-like structures.