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We experimentally investigate ghost imaging with bucket detection and point detection in which three types of illuminating sources are applied: (a) pseudo-thermal light source; (b) amplitude modulated true thermal light source; (c) amplitude modulated laser source. Experimental results show that the quality of ghost images reconstructed with true thermal light or laser beam is insensitive to the usage of bucket or point detector, however, the quality of ghost images reconstructed with pseudo-thermal light in bucket detector case is better than that in point detector case. Our theoretical analysis shows that the reason for this is due to the first order transverse coherence of the illuminating source.

We theoretically study the influence of degree of polarization (DOP) of thermal light on the contrast-to-noise ratio (CNR) of the reflective ghost imaging (RGI), which is a novel and indirect imaging modality. An expression for the CNR of RGI with partially polarized thermal light is carefully derived, which suggests a weak dependence of CNR on the DOP, especially when the ratio of the object size to the speckle size of thermal light has a large value. Different from conventional imaging approaches, our work reveals that RGI is much more robust against the DOP of the light source, which thereby has advantages in practical applications, such as remote sensing.

In classical physics, a joint measurement of two compatible observables on an enlarged system–apparatus state usually implies that the joint statistics of the corresponding specific system observables are always separable. In this paper, we show that, for the quantum states with its density operators composed of the Dirac–Pauli matrices, the joint statistics of these specific system observables are entangled and the data inversion of the joint statistical distribution is negative. This nonclassical property, which can be revealed by an experimental scheme based on the homodyne detection, maybe helps us to understand the nonlocal features of the quantum tests of the Bell type. When we consider these Dirac–Pauli states as $$2\times 2$$ bipartite ones, these bipartite states have a nonzero quantum discord although they are separable.

Different from classical Talbot self-imaging, second-order spatial Talbot effect is a kind of second-order imaging, in which the self-imaging of an object is observed through intensity correlation measurement. Here, in terms of space-time duality, we investigate the temporal counterpart of second-order Talbot self-imaging with temporally incoherent light. Our work shows that second-order Talbot effect in the time domain is related to the joint dispersion of light pulse in dispersive medium. Particularly, based on the discrete Fourier transformation, the fractional Talbot self-imaging via intensity correlation doesn't generally possess a definite fractional period, which contradicts some articles' results. Our results may be useful for implementing the repetition-rate-multiplication technique and remotely transmitting the periodic temporal signals robustly.

The influence of detector response speed on the contrast-to-noise ratio (CNR) of reflective ghost imaging (RGI) is studied. To mimic the situation of a slow response detector, the illuminating speckle patterns are replaced with the sum of uncorrelated speckle patterns for each measurement. An expression for the CNR of RGI with added speckle patterns is derived. By employing a light projector to provide spatially incoherent structured illumination in a computational ghost imaging system, we perform computational RGI based on added speckle patterns. The experimental results show that when up to 40 uncorrelated speckle patterns are added together in each measurement, the CNR of computational RGI obtained from 5000 effective measurements remains almost the same as the conventional computational ghost imaging. The reason for this is that the image quality of RGI depends on the kurtosis of intensity fluctuation of speckle field instead of the contrast ratio of speckle pattern. The experimental results agree with the theoretical prediction.

In classical optics, Young’s double-slit experiment with colored coherent light gives rise to individual interference fringes for each light frequency, referring to single-photon interference. However, two-photon double-slit interference has been widely studied only for wavelength-degenerate biphoton, known as subwavelength quantum lithography. In this work, we report double-slit interference experiments with two-color biphoton. Different from the degenerate case, the experimental results depend on the measurement methods. From a two-axis coincidence measurement pattern we can extract complete interference information about two colors. The conceptual model provides an intuitional picture of the in-phase and out-of-phase photon correlations and a complete quantum understanding about the which-path information of two colored photons.

We present theoretical analysis and experimental demonstration of near field and far field spatial correlations of thermal light. Similar to the inequality Δ x − Δ p + 1 for a two-photon entangled source, we obtain an inequality Δ x − Δ p − 1 which also concerns both photon position and transverse wavevector correlations of thermal light. To test this inequality, we carry out an experiment in which ghost diffraction and ghost imaging can be simultaneously observed without the aid of any lenses. Meanwhile, the inequality is examined experimentally.

Lau effect is a self-imaging formed in the far field of a pair of gratings illuminated by spatially incoherent light. We report the experimental demonstration of the second-order Lau effect with incoherently pseudo-thermal light. Spatially periodic structures were nonlocally superposed giving rise to interference patterns in intensity correlation measurement. The experimental results are in agreement with the theoretical analysis. The second-order Lau effect can be well understood by the unfolded version of the experimental setup where the bucket detection can be thought as the incoherent illumination in classical Lau effect.

A wavelength-multiplexing ghost-imaging (WMGI) technique is performed in order to improve long data acquisition time in conventional ghost imaging. In WMGI, a source has more than two colored light beams which are independently modulated and projected onto an object at the same time. Then the reflected light from the object is recorded with wavelength-selected detectors. We analyze the contrast-to-noise ratio (CNR) of the reconstructed images of each single-wavelength ghost imaging and their superposition and demonstrate the validity of the WMGI technique.

We propose a new scheme to achieve sub-Rayleigh resolution of interference pattern with independent laser beams. We perform an experimental observation of a double-slit interference with two orthogonally polarized laser beams. The resolution of the interference pattern measured by a two-photon detection is doubled provided the two beams illuminate the double-slit with certain incident angles. The scheme is simple and can be in favor of both high intensity and perfect visibility.

We report the experimental observation of classical subwavelength double slit interference with a pseudothermal light source. The experimental results are in good agreement with the theoretical simulation using the second order correlation function for the thermal light.

We report an experimental realization of lensless ghost imaging for a phase-only object with pseudo-thermal light, which was proposed by W. Gong and S. Han [Phys. Rev. A 82, 023828 (2010)]. In contrast with conventional ghost imaging, the scheme involves the interference of two correlated fields and the phase information of the object can be retrieved. This imaging technique completes the nonlocally lensless spatial reconstruction of both amplitude and phase distributions in ghost imaging with thermal light.