Manipulating the Spatial Structure of Second-Order Quantum Coherence Using Entangled Photons

High-order quantum coherence reveals the statistical correlation of quantum particles. Manipulation of quantum coherence of light in the temporal domain enables the production of the single-photon source, which has become one of the most important quantum resources. High-order quantum coherence in the spatial domain plays a crucial role in a variety of applications, such as quantum imaging, holography, and microscopy. However, the active control of second-order spatial quantum coherence remains a challenging task. Here we predict theoretically and demonstrate experimentally the first active manipulation of second-order spatial quantum coherence,which exhibits the capability of switching between bunching and anti-bunching, by mapping the entanglement of spatially structured photons. We also show that signal processing based on quantum coherence exhibits robust resistance to intensity disturbance. Our findings not only enhance existing applications but also pave the way for broader utilization of higher-order spatial quantum coherence.

Future directions:combination of acupuncture with mesenchymal stem cells for Parkinson’s disease

Parkinson’s disease(PD)is a progressive chronic disease currently with no radical cure drugs and means due to the complex pathological mechanisms and limited regenerative capacity of neurons.Acupuncture aids in neuronal regeneration via various signaling routes like ROCK,Wnt,and Notch,safeguarding dopaminergic neurons against inflammation,oxidative stress,and cell death,which in turn enhances the progression of PD progression.Numerous research findings indicate that integrating acupuncture with mesenchymal stem cells(MSCs)transplantation is more effective than using either acupuncture or MSCs infusion alone.The combined treatment improves the survival rate of MSCs,promotes the generation of functional neural networks by stimulating the secretion of neurotrophic factors,and ultimately improves the disease microenvironment.In this review,we state the neuroprotective effects of acupuncture or MSCs treament alone in PD,then summarize the application of acupuncture combined with MSCs therapy in other diseases.Consequently,we anticipate that integrating acupuncture with MSCs transplantation may emerge as a novel and efficient approach for managing PD.This possibility needs to be verified through further basic and clinical research.

Particle transport behavior in air channel flow with multi-group Lagrangian tracking

The particle motions of dispersion and transport in air channel flow are investigated using a large eddy simulation（LES） and Lagrangian trajectory method. The mean and fluctuating velocities of the fluids and particles are obtained,and the results are in good agreement with the data in the literature. Particle clustering is observed in the near-wall and low-speed regions. To reveal the evolution process and mechanism of particle dispersion and transport in the turbulent boundary layer, a multi-group Lagrangian tracking is applied when the two-phase flow has become fully developed： the fluid fields are classified into four sub-regions based on the flow characteristics, and particles in the turbulent region are divided accordingly into four groups when the gas–particle flow is fully developed. The spatiotemporal transport of the four groups of particles is then tracked and analyzed. The detailed relationship between particle dispersion and turbulent motion is investigated and discussed.

Three-dimensional turbulent flow over cube-obstacles

In order to investigate the influence of surface roughness on turbulent flow and examine the wall-similarity hypothesis of Townsend, three-dimensional numerical study of turbulent channel flow over smooth and cube-rough walls with different roughness height has been carried out by using large eddy simulation（LES） coupled with immersed boundary method（IBM）. The effects of surface roughness array on mean and fluctuating velocity profiles, Reynolds shear stress, and typical coherent structures such as quasi-streamwise vortices（QSV） in turbulent channel flow are obtained. The significant influences on turbulent fluctuations and structures are observed in roughness sub-layer（five times of roughness height）.However, no dramatic modification of the log-law of the mean flow velocity and turbulence fluctuations can be found by surface cube roughness in the outer layer. Therefore, the results support the wall-similarity hypothesis. Moreover, the von Karman constant decreases with the increase of roughness height in the present simulation results. Besides, the larger size of QSV and more intense ejections are induced by the roughness elements, which is crucial for heat and mass transfer enhancement.

Iso-propagation vortices with OAM-independent size and divergence toward future faster optical communications

Recognized in the 1990s,vortex beams'ability to carry orbital angular momentum(OAM)has significantly contributed to applications in optical manipulation and high-dimensional classical and quantum information communication.However,inherent diffraction in free space results in the inevitable expansion of beam size and divergence contingent upon the OAM,limiting vortex beams'applicability in areas such as spatial mode multiplexing communication,fiber-optic data transmission,and particle manipulation.These domains necessitate vortex beams with OAM-independent propagation characteristics.We introduce iso-propagation vortices(IPVs),vortex beams characterized by OAM-independent propagation behavior,achieved through precise radial index configuration of Laguerre-Gaussian beams.IPVs display notable transmission dynamics,including a reduced quality factor,resilience post-damage,and decreased and uniform modal scattering under atmospheric turbulence.Their distinctive attributes render IPVs valuable for potential applications in imaging,microscopy,optical communication,metrology,quantum information processing,and light-matter interactions.Notably,within optical communication,the case study suggests that the IPV basis,due to its OAM-independent propagation behavior,provides access to a more extensive spectrum of data channels compared with conventional spatial multiplexing techniques,consequently augmenting information capacity.

Dual-curvilinear beam enabled tunable manipulation of high-and low-refractive-index particles

We present an innovative approach for the simultaneous agile manipulation of high-refractive-index(HRI) and low-refractive-index(LRI) particles. Our method involves introducing a dual-curvilinear optical vortex beam(DC-OVB) generated by superimposing a pair of curved beams: HRI and LRI particles are controlled by the bright curve and the dark channel between the two curves, respectively. The proposed DC-OVB provides customizable motion paths and velocities for both LRI and HRI particles. Each curve of the DC-OVB can support a distinct orbital flow density(OFD), enabling the application of torques to HRI and LRI particles, guiding them to orbit along specified trajectories and prompting them to execute various curvilinear motions simultaneously,including curvilinear movement, revolution, and rotation.

Emergence of classical objectivity of quantum Darwinism in a photonic quantum simulator

Quantum-to-classical transition is a fundamental open question in physics frontier. Quantum decoherence theory points out that the inevitable interaction with environment is a sink carrying away quantum coherence, which is responsible for the suppression of quantum superposition in open quantum system.Recently, quantum Darwinism theory further extends the role of environment, serving as communication channel, to explain the classical objectivity emerging in quantum measurement process. Here, we used a six-photon quantum simulator to investigate classical and quantum information proliferation in quantum Darwinism process. In the simulation, many environmental photons are scattered from an observed quantum system and they are collected and used to infer the system's state. We observed redundancy of system's classical information and suppression of quantum correlation in the fragments of environmental photons. Our results experimentally show that the classical objectivity of quantum system can be established through quantum Darwinism mechanism.

Experimental test of generalized Hardy's paradox

Since the pillars of quantum theory were established, it was already noted that quantum physics may allow certain correlations defying any local realistic picture of nature, as first recognized by Einstein,Podolsky and Rosen. These quantum correlations, now termed quantum nonlocality and tested by violation of Bell's inequality that consists of statistical correlations fulfilling local realism, have found loophole-free experimental confirmation. A more striking way to demonstrate the conflict exists, and can be extended to the multipartite scenario. Here we report experimental confirmation of such a striking way, the multipartite generalized Hardy's paradoxes, in which no inequality is used and the conflict is stronger than that within just two parties. The paradoxes we consider here belong to a general framework [S.-H. Jiang et al., Phys. Rev. Lett. 120(2018) 050403], including previously known multipartite extensions of Hardy's original paradox as special cases. The conflict shown here is stronger than in previous multipartite Hardy's paradox. Thus, the demonstration of Hardy-typed quantum nonlocality becomes sharper than ever.

Curvilinear Poincaré vector beams

We develop a method for completely shaping optical vector beams with controllable amplitude, phase, and polarization gradients along three-dimensional freestyle trajectories. We design theoretically and demonstrate experimentally curvilinear Poincaré vector beams that exhibit high intensity gradients and accurate state of polarization prescribed along the beam trajectory.

Manipulating propagation and evolution of polarization singularities in composite Bessel-like fields

Structured optical fields embedded with polarization singularities(PSs)have attracted extensive attention due to their capability to retain topological invariance during propagation.Many advances in PS research have been made over the past 20 years in the areas of mathematical description,generation and detection technologies,propagation dynamics,and applications.However,one of the most crucial and difficult tasks continues to be manipulating PSs with multiple degrees of freedom,especially in three-dimensional(3D)tailored optical fields.We propose and demonstrate the longitudinal PS lines obtained by superimposing Bessel-like modes with orthogonal polarization states on composite vector optical fields(VOFs).The embedded PSs in the fields can be manipulated to propagate robustly along arbitrary trajectories,or to annihilate,revive,and transform each other at on-demand positions in 3D space,allowing complex PS’topological morphology and intensity patterns to be flexibly customized.Our findings could spur further research into singular optics and help with applications such as micromanipulation,microstructure fabrication,and optical encryption.