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Although its ubiquitous emergence in nature and variety of systems, turbulence possesses spatio-temporal chaotic, intermittent fluctuations, and makes it impossible to be precisely predicted. Persistent attempts for almost a century have been devoted to capture the invariant laws and hidden deeply universality out of the vast disorder and chaotic nature of turbulence. The celebrated Kolmogorov -5/3 law is robust, but not comprehensive to describe the diverse turbulences, especially in the turbulence driven by external volume forces, e.g. thermal convection, electrokinetic turbulence and etc. Here, we reveal that the fluxes of kinetic energy and scalar variance must be highly coupled to establish a universal conservation law and consequently we successfully unify a much diversity of scaling laws. As an example, in a microfluidic electrokinetic turbulence, additional scaling of -5/3, -9/5 and -7/3 are experimentally found in the power spectra of concentration. With this proposed model, a full quad-cascade picture is eventually complete to unify the various scaling laws for the most complicated physical problem of turbulence.

The interference phenomenon of light is a common but most important effect in physics. In this article, we compare and analyse the interference effects of both coherent and incoherent light; in particular, the interference of spatially incoherent light sources is described. Thermal light and a two-photon entangled source may both be regarded as incoherent sources which can generate similar second-order interference effects, but their underlying physics is quite different. First-order interference can be realized with both spatially coherent and incoherent sources in the same well-designed experimental setup, but exhibit different interference patterns; their different interference mechanisms will also be clarified., Comment: 46 pages,31 figures

Electroosmotic flow (EOF) exists widely at the solid-liquid interface in the presence of external electric field. However, the EOF driven by an alternating current (AC) electric field in diverse chemical environments was far from being well understood due to limited experimental investigations. In this investigation, through the high-resolution laser-induced fluorescent photobleaching anemometer (LIFPA), the transient velocity according to the AC EOF on the electric double layer (EDL) far from the electrodes has been experimentally characterized, by means of time series and power spectra. With analyzing the transient velocity, the transition of AC EOF from linear to nonlinear behavior is observed in a broad parameter space, e.g. mean flow velocity, the frequency and intensity of the AC electric field, and the pH value of the bulk fluid. To take all these parameters into account, an electro-inertial velocity has been applied as the characteristic velocity, instead of the commonly applied Helmholtz-Smouluchowski velocity. Then, the transitional electric field intensity $E_{A,C}$ and the corresponding dimensionless parameter $Z_{nlc}$ are systematically studied. A power-law relationship between the linear term coefficient $Z_l$ and $Z_{nlc}$ has been established, with the scaling exponents determined by the pH value of the electrolyte solution. We hope the current investigation can provide a deeper understanding of the transition of AC EOF and the instantaneous response of EOFs in other forms. It also provides a simple model to understand the coupling between electric field and fluid flow, in both linear and nonlinear status.

The crucial zeroth-order light due to the pixelation effect of spatial light modulator (SLM) has been a serious issue in the field of light modulation, especially in applications with a high numerical aperture optical system. In this investigation, we report that by properly adjusting the high-level and low-level pixel voltages of an SLM, the zeroth-order light caused by the pixelation effect of SLM can be significantly eliminated. The method is further validated in an inverted fluorescence microscope. The experimental results show that the zeroth-order light can be inhibited up to 91.3%, accompanied by an improvement of the modulation efficiency from 77.5% to 92.6%., In this version, the mechanism underlined has been corrected. Accompanied, Figure 1 has been replaced

Quantum imagers have won accolades for their quantum characteristics and fruitful applications. Ghost imaging exhibited nonlocality with quantum-entangled photons from the parametric down-conversion process, and later with thermal-light sources. Single-pixel imaging retrieved high-quality images with compressive sensing and singular valued decomposition algorithms. Single-photon sensitive apparatus were conducive to first-photon imaging, light-in-flight imaging, photon-efficient imaging, and super-remote imaging. Photon-limited imaging was investigated in low-light-level ghost imaging and fast first-photon ghost imaging. Here in the single-pixel imager scheme, we present zero-photon imaging in which high-quality negative images are reconstructed by correlating the zero-photon measurements and the modulation signals. Also, images are reconstructed with few-photon-state measurements. By comparison, the image quality in ZPI is much higher. This technique may be of significant benefit to rapid pattern recognition and remote sensing., 7 pages, 4 figures, two columns

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., Comment: 13 pages, 6 figures

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., 4 pages, 2figures

Complementarity is usually considered as a phenomenon of microscopic systems. In this paper we report an experimental observation of complementarity in the correlated double-slit interference with a pseudothermal light source. The thermal light beam is divided into test and reference beams which are correlated with each other. The double-slit is set in the test arm, and the interference pattern can be observed in the intensity correlation between the two arms. The experimental results show that the disappearance of interference fringe depends on whether which-path information is gained through the reference arm. The experiment therefore witnesses the complementarity occurring in a macroscopic system., 6 pages, 4 figures

We perform a nonlocal double-slit interference experiment with pseudothermal light. The experimental result exhibits a typical double-slit interference fringe in the intensity correlation measurement, in agreement with the theoretical analysis by means of the property of the second-order spatial correlation of field., Comment: 2 pages, 2 figures

We show that a thermal light random in transverse direction can perform subwavelength double slit interference in a joint-intensity measurement. This is the classical version of quantum lithography, and it can be explained with the correlation of rays instead of the entanglement of photons., 4 pages, 2 figures

We discuss the geometrical optics of coincidence imaging for two kinds of spatial correlations which are related to a classical thermal light source and a two-photon quantum entangled state., Comment: 4 pages, 5 figures

We show the experimental observation of the classical sub-wavelength double-slit interference with a pseudo-thermal light source. The experimental results are in agreement with the recent theoretical prediction shown in quant-ph/0404078 (to be appeared in Phys. Rev. A)., Comment: 4 pages, 6 figures

We analyze a double $��$ atomic configuration interacting with two signal beams and two control beams. Because of the quantum interference between the two $��$ channels, the four fields are phase-matched in electromagnetically induced transparency. Our numerical simulation shows that this system is able to manipulate synchronous optical signals, such as generation of optical twin signals, data correction, signal transfer and amplification in the atomic storage., 5 pages, 7 figures

We study a general theory on the interference of a two-photon wavepacket in a beam splitter. The theory is carried out in the Schr\"{o}dinger picture so that the quantum nature of the two-photon interference is explicitly presented. We find that the topological symmetry of the probability-amplitude spectrum of the two-photon wavepacket dominates the manners of two-photon interference which are distinguished according to increasing and decreasing the coincidence probability for the absence of interference. However, two-photon entanglement can be witnessed by the interference manner. We demonstrate the necessary and sufficient conditions for the perfect two-photon interference. For a two-photon entangled state with an anti-symmetric spectrum, it passes a 50/50 beam splitter with the perfect transparency. The theory contributes an unified understanding to a variety of the two-photon interference effects., Comment: 21 pages, 12 figures

We study the generalized Young's double-slit interference for the beam produced in the spontaneously parametric down-conversion (SPDC). We find that the sub-wavelength lithography can occur macroscopically in both the two-photon intensity measurement and the single-photon spatial intensity correlation measurement. We show the visibility and the strength of the interference fringe related to the SPDC interaction. It may provide a strong quantum lithography with a moderate visibility in practical application., 6 pages, 5 Postscript figures, uses revtex