Steering nonlocality is the fundamental property of quantum mechanics, which has been widely demonstrated in some systems with qubits. Recently, theoretical works have shown that the high-dimensional (HD) steering effect exhibits novel and important features, such as noise suppression, which appear promising for potential application in quantum information processing (QIP). However, experimental observation of these HD properties remains a great challenge to date. In this work, we demonstrate the HD steering effect by encoding with orbital angular momentum photons for the first time. More importantly, we have quantitatively certified the noise-suppression phenomenon in the HD steering effect by introducing a tunable isotropic noise. We believe our results represent a significant advance of the nonlocal steering study and have direct benefits for QIP applications with superior capacity and reliability.

Quantum walks (QWs) provide a powerful tool as a quantum simulator to study and understand topological phases. Using such a quantum simulator, some topological phenomena have been discussed. However, all the experimental observations on the topological phenomena in QWs have been restricted to evolution in one dimension (1D) so far. The existing 2D experimental platforms cannot be applied to study topological phenomena due to lack of full control in the position space. Thus, some interesting topological phenomena in the 2D QW that do not exist in the 1D case, e.g., the edge-state-enhanced transport, have not been demonstrated experimentally. Here we report the experimental realization of 2D QW using spatial positions and orbital angular momentum of light. Based on our constructed experimental platform, we have observed 2D topological bound states with vanishing Chern numbers and confirmed the robustness of these bound states with respect to perturbations and disorder, which go beyond what has been known in static systems and are unique to periodically driven systems. Our studies not only represent an important advance in the study of topological phases, but also open up an avenue to explore topological properties in multidimensional QWs.

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Recently, the study of non-Hermitian physics has attracted considerable attention. The modified bulk-boundary correspondence has been proposed to understand topological edge states in non-Hermitian static systems. Here we report a new experimental observation of edge states in non-Hermitian periodically driven systems. Some unconventional edge states are found not to be satisfied with the bulk-boundary correspondence when the system belongs to the broken paritytime (PT) symmetric phase. The experiments are performed in our constructed non-Hermitian light quantum walk platform with left and right boundaries, where the beams outside system boundary are blocked subtly at the end of each step. The robust properties of these edge states against to static perturbations and disorder have also been demonstrated experimentally. The finding of robust edge states in broken PT-symmetric phase inspires us to explore a robust transport channel in ubiquitously complex systems with strong dissipation.

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We propose an efficient method to accurately identify two mode indices (p and l) of Laguerre–Gaussian (LG) beams simultaneously with weak value measurement (WVM). Concise relations between the spatial displacements from the WVM and two mode indices of LG beams have been obtained. Compared with the traditional measurements, the advantage of using our method is that LG beams with large p and l can be identified precisely. A joint spatial WVM with a looser approximate condition has been presented, which realizes better identification than the individual spatial WVM with correction terms or strict approximation. Furthermore, the signal-to-noise ratio (SNR) of the spatial WVM is also discussed.

Realization of robust transmission and transformation of entangled states with high fidelity is crucial for the applications in quantum information, computing, and communications. However, it is hard to achieve currently because of scattering loss and disorder. Here, an inverse-design scheme is theoretically proposed and experimentally demonstrated to realize nearly perfect transmission and transformation of entangled photon states. The scheme is based on the determination of the transmission and transformation properties of entangled states, which depends on the overlap integrals among the initial states, eigenmodes of the system and target states. Thus, topologically protected channels are designed according to the requirements for the overlap integrals of these states. As a result, robust transmission and transformation of entangled states are achieved with high fidelity. The proposed scheme has been demonstrated experimentally using the constructed quantum walk platform. This work interconnects topology, quantum physics, and inverse design, and opens up a new avenue for quantum engineering.