Observation of single-photon azimuthal backflow with weak measurement.

Quantum backflow (QB), a counterintuitive interference phenomenon where particles with positive momentum can propagate backward, is important in applications involving light-matter interactions. To date, experimental demonstrations of backflow have been restricted to classical optical systems using techniques such as slit scanning or Shack-Hartmann wavefront sensing, which suffer from low spatial resolution due to the inherent limitations in slit width and lenslet array density. Here, we report an observation of azimuthal backflow (AB) both theoretically and experimentally by employing the weak measurement technique, which enables the precise extraction of photon momentum at each pixel.

Activation of Einstein-Podolsky-Rosen steering sharing with unsharp nonlocal measurements.

Einstein-Podolsky-Rosen (EPR) steering is commonly shared among multiple observers by utilizing unsharp measurements. Nevertheless, their usage is restricted to local measurements and does not encompass all nonlocal measurement-based cases. In this work, a method for finding beneficial local measurement settings has been expanded to include nonlocal measurement cases.

Experimental recognition of vortex beams in oceanic turbulence combining the Gerchberg-Saxton algorithm and convolutional neural network.

In underwater wireless optical communication (UWOC), vortex beams carrying orbital angular momentum (OAM) can improve channel capacity but are vulnerable to oceanic turbulence (OT), leading to recognition errors. To mitigate this issue, we propose what we believe to be a novel method that combines the Gerchberg-Saxton (GS) algorithm-based recovery with convolutional neural network (CNN)-based recognition (GS-CNN). Our experimental results demonstrate that superposed Laguerre-Gaussian (LG) beams with small topological charge are ideal information carriers, and the GS-CNN remains effective even when OT strength 2 is high up to 10 .

Reliable experimental manipulation of quantum steering direction.

Noise-adding methods have been widely used to manipulate the direction of quantum steering, but all related experimental schemes only worked under the assumption that Gaussian measurements were performed and ideal target states were accurately prepared. Here, we prove, and then experimentally observe, that a class of two-qubit states can be flexibly changed among two-way steerable, one-way steerable and no-way steerable, by adding either phase damping noise or depolarization noise. The steering direction is determined by measuring steering radius and critical radius, each of which represents a necessary and sufficient steering criterion valid for general projective measurements and actually prepared states.

Dynamics of multipartite quantum steering for different types of decoherence channels.

Multipartite quantum steering, a unique resource for asymmetric quantum network information tasks, is very fragile to the inevitable decoherence, which makes it useless for practical purposes. It is thus of importance to understand how it decays in the presence of noise channels. We study the dynamic behaviors of genuine tripartite steering, reduced bipartite steering, and collective steering of a generalized three-qubit W state when only one qubit interacts independently with the amplitude damping channel (ADC), phase damping channel (PDC) or depolarizing channel (DC).

Protecting nonlocal quantum correlations in correlated squeezed generalized amplitude damping channel.

Nonlocal quantum correlations, such as quantum entanglement, quantum steering, and Bell nonlocality, are crucial resources for quantum information tasks. How to protect these quantum resources from decoherence is one of the most urgent problems to be solved. Here, we investigate the evolution of these correlations in the correlated squeezed generalized amplitude damping (SGAD) channel and propose a scheme to protect them with weak measurement (WM) and quantum measurement reversal (QMR).

Investigation of the influence of measurement imperfections on quantum communication complexity superiority for the Clauser-Horne-Shimony-Holt game.

Demonstrating quantum communication complexity superiority non-trivially with currently available experimental systems is of utmost importance in quantum information science. Here, we propose a generalized entanglement-assisted communication complexity reduction protocol and analyze the robustness of its quantum superiority against the measurement imperfections, such as measurement basis deviation and choice probability bias, a common problem rarely studied before. We find that the quantum superiority can be obtained in a specific entangled state in a suitable range of measurement basis and basis choice parameters.

Performance of underwater quantum key distribution with polarization encoding.

Underwater quantum key distribution (QKD) has potential applications in absolutely secure underwater communication. However, the performance of underwater QKD is limited by the optical elements, background light, and dark counts of the detector. In this paper, we propose a modified formula for the quantum bit error rate (QBER), which takes into account the effect of detector efficiency on the QBER caused by the background light.

Effect of oceanic turbulence on the visibility of underwater ghost imaging.

We carry out a detailed study on underwater ghost imaging (GI) in oceanic turbulence. We set up a physical model of GI through oceanic turbulence, which includes light-field transmission, and interaction between light field and oceanic turbulence without considering the effects of water absorption and scattering of light. We obtain theoretical expressions for the impulse response function and the visibility of GI in oceanic turbulence based on the power spectrum of the turbulence and the extended Huygens-Fresnel integral.

Clinical outcome of 30 patients with bone marrow metastases.

Objective: Cancer patients with bone marrow metastases are rare and dismal. The study was to identify the clinical features and prognostic factors in cancer patients with bone marrow metastases.

Patients And Methods: A total of 30 patients with bone marrow metastases were reviewed between September 2007 and September 2013.

Channel analysis for single photon underwater free space quantum key distribution.

We investigate the optical absorption and scattering properties of underwater media pertinent to our underwater free space quantum key distribution (QKD) channel model. With the vector radiative transfer theory and Monte Carlo method, we obtain the attenuation of photons, the fidelity of the scattered photons, the quantum bit error rate, and the sifted key generation rate of underwater quantum communication. It can be observed from our simulations that the most secure single photon underwater free space QKD is feasible in the clearest ocean water.

Generation of three-dimensional entangled state between a single atom and a Bose-Einstein condensate via adiabatic passage.

Inspired by a recently experiment by M. Lettner et al. [Phys.