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We report an experimental demonstration of sub-wavelength interference without correlation. Typically, people can achieve sub-wavelength effect with correlation measurement no matter by using bi-photon or thermal light sources. Here we adopt a thermal light source. And we count the realizations in which the intensities of the definite symmetric points are above or below a certain threshold. The distribution of numbers of these realizations who satisfy the restriction will show a sub-wavelength effect. With proper constrictions, positive and negative interference patterns are demonstrated.

In thermal light ghost imaging, the correlation orders were usually positive integers in previous studies. In this paper, we examine the fractional-order moments, whose correlation order are fractional numbers, between the bucket and reference signals in the ghost imaging system. The crucial step in theory is to determine the precise relation between the bucket signals and reference signals. We deduce the joint probability density function between the bucket and reference signals by regarding the reference signals as an array of independent stochastic variables. In calculating the fractional-order moments, the correlation order for the reference signals must be positive to avoid infinity. While the correlation order for the bucket signals can be positive or negative numbers. Negative (positive) ghost images are obtained with negative (positive) orders of the bucket signals. The visibility degree and signal-to-noise ratio of ghost images from the fractional-order moments are analysed. The experimental results and numerical simulations meet our analysis based on probability theory., Comment: 5 pages, 4 figures

Entangled coherent states are shown to emerge, with high fidelity, when mixing coherent and squeezed vacuum states of light on a beam-splitter. These maximally entangled states, where photons bunch at the exit of a beamsplitter, are measured experimentally by Fock-state projections. Entanglement is examined theoretically using a Bell-type nonlocality test and compared with ideal entangled coherent states. We experimentally show nearly perfect similarity with entangled coherent states for an optimal ratio of coherent and squeezed vacuum light. In our scheme, entangled coherent states are generated deterministically with small amplitudes, which could be beneficial, for example, in deterministic distribution of entanglement over long distances., Comment: 6 pages, 6 figures, comments are welcome

We report the first experimental observation of quantum holographic imaging with entangled photon pairs, generated in a spontaneous parametric down-conversion process. The signal photons play both roles of "object wave" and "reference wave" in holography but are recorded by a point detector providing only encoding information, while the idler photons travel freely and are locally manipulated with spatial resolution. The holographic image is formed by the two-photon correlation measurement, although both the signal and idler beams are incoherent. According to the detection regime of the signal photons, we analyze three types of quantum holography schemes: point detection, coherent detection and bucket detection, which can correspond to classical holography using a point source, a plane-wave coherent source and a spatially incoherent source, respectively. Our experiment demonstrates that the two-photon holography in the point detection regime is equivalent to the one-photon holography using a point source. Physically, the quantum holography experiment verifies that a pair of non-commutable physical quantities, the amplitude and phase components of the field operator, can be nonlocally measured through two-photon entanglement., Comment: 10 pages, 4 figures

We report an experimental observation of quantum Airy disk diffraction pattern using an entangled two-photon source. In contrast to the previous quantum lithography experiments where the subwavelength diffraction patterns were observed in the far field limit, we perform the Fraunhofer diffraction experiment with a convex lens. The experimental result shows that the two-photon Airy disk is provided with the super-resolution spot, which surpasses the classical diffraction limit. In particular, the spot size can be well controlled by the focal length, which adapted to optical super-focusing. Our experiment can promote potential application of quantum lithography., Comment: 4 pages, 2figures