Entangled-photon coincidence imaging is a method to nonlocally image an object by transmitting a pair of entangled photons through the object and a reference optical system respectively. The image of the object can be extracted from the coincidence rate of these two photons. From a classical perspective, the image is proportional to the fourth-order correlation function of the wave field. Using classical statistical optics, we study a particular aspect of coincidence imaging with incoherent sources. As an application, we give a proposal to realize lensless Fourier-transform imaging, and discuss its applicability in X-ray diffraction.
We propose an experimental scheme to create spin-orbit coupling in spin-3 Cr atoms using Raman processes. By employing the linear Zeeman effect and optical Stark shift, two spin states within the ground electronic manifold are selected, which results in a pseudo-spin-1/2 model. We further study the ground state structures of a spin-orbit-coupled Cr condensate. We show that, in addition to the stripe structures induced by the spin-orbit coupling, the magnetic dipole-dipole interaction gives rise to the vortex phase, in which a spontaneous spin vortex is formed.PACS numbers: 37.10. Vz, 03.75.Mn Over the past few years, there has been rapidly growing interest in engineering Abelian and non-Abelian artificial gauge fields in ultracold atomic gases [1][2][3][4][5][6]. Particularly, the non-Abelian gauge field, or more specifically the spin-orbit (SO) coupling, is of fundamental importance in many branches of physics. Fascinating examples include the quantum spin-Hall effect and the topological insulators in condensed matter physics [7]. With the enormous tunability of the interaction and geometry, ultracold atomic gases may offer a tremendous opportunity for studying exotic quantum phenomena in many-body systems with SO coupling [8][9][10][11][12][13][14][15][16].In their pioneer experiments, the NIST group have realized the light-induced vector potentials [17], the synthetic magnetic fields [18], and the electric forces [19] in ultracold Rb gases through Raman processes [4], which differs from most dark-state based theoretical proposals [20] in that the linear Zeeman shift is compensated by the two-photon detuning. More remarkably, they also created a two-component SO-coupled condensate of Rb atoms and observed the phase transition from spatially mixed to separated states [21]. An important ingredient in this experiment is that the quadratic Zeeman shift is employed to separate two desired spin states from the remaining one. Hence, this scheme is inapplicable to atoms without nuclear spin, such as certain isotopes of Cr and Dy, in which the quadratic Zeeman effect is absent.In this Letter, we propose an experimental scheme to create SO coupling in spin-3 52 Cr atoms by selecting two internal states from the J = 3 ground electronic manifold. Similar to the NIST group's scheme, ours also relies on Raman processes. However, we utilize the optical Stark shift to compensate the linear Zeeman shift so that the lowest two levels are near degenerate and well separated from other levels, which leads to a pseudo spin-1/2 model. The proposed scheme has the advantages that only a moderate magnetic field strength is required and it also applies to atoms without nuclear spin.An interesting feature of the Cr atom is that it possesses a large magnetic dipole moment, which makes the scalar Cr condensate an important platform for demon- strating the dipolar effects [22]. Moreover, when an atom's spin degree of freedom becomes available, magnetic dipole-dipole interaction (MDDI) also couples the spin and orbital angular momenta, wh...
Ghost imaging through turbulent atmospheres are theoretically studied. Based on the extended Huygens-Fresnel integral, we obtain an analytical imaging formula. The ghost image can be viewed as the convolution of the original object and a point-spread function (PSF). The imaging quality is determined by the size of the PSF. Increasing the turbulence strength and propagation distance, or decreasing the source size, will increase the size of the PSF, and lead to the degradation of the imaging quality.
The Fourier-Transform ghost imaging of both amplitude-only and pure-phase objects was experimentally observed with classical incoherent light at Fresnel distance by a new lensless scheme. The experimental results are in good agreement with the standard Fourier-transform of the corresponding objects. This scheme provides a new route towards aberration-free diffraction-limited 3D images with classically incoherent thermal light, which have no resolution and depth-of-field limitations of lens-based tomographic systems.
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