Verifying Genuine High-Order Entanglement

High-order entanglement embedded in multipartite multilevel quantum systems (qudits) with many degrees of freedom (DOFs) plays an important role in quantum foundation and quantum engineering. Verifying high-order entanglement without the restriction of system complexity is a critical need in any experiments on general entanglement. Here, we introduce a scheme to efficiently detect genuine high-order entanglement, such as states close to genuine qudit Bell, Greenberger-Horne-Zeilinger, and cluster states as well as multilevel multi-DOF hyperentanglement. All of them can be identified with two local measurement settings per DOF regardless of the qudit or DOF number. The proposed verifications together with further utilities such as fidelity estimation could pave the way for experiments by reducing dramatically the measurement overhead

Efficient and long-lived quantum memory with cold atoms inside a ring cavity

Quantum memories are regarded as one of the fundamental building blocks of linear-optical quantum computation and long-distance quantum communication. A long standing goal to realize scalable quantum information processing is to build a long-lived and efficient quantum memory. There have been significant efforts distributed towards this goal. However, either efficient but short-lived or long-lived but inefficient quantum memories have been demonstrated so far. Here we report a high-performance quantum memory in which long lifetime and high retrieval efficiency meet for the first time. By placing a ring cavity around an atomic ensemble, employing a pair of clock states, creating a long-wavelength spin wave, and arranging the setup in the gravitational direction, we realize a quantum memory with an intrinsic spin wave to photon conversion efficiency of 73(2)% together with a storage lifetime of 3.2(1) ms. This realization provides an essential tool towards scalable linear-optical quantum information processing.Comment: 6 pages, 4 figure

Methods for Characterizing the 3-D Morphology of Polymer Composites

3-dimensional visualization of polymer morphology is of increasing interest in the polymer community because it provides a deeper insight into the arrangement of the phases in heterophasic polymeric materials, for example in composites. Depending on the size of the fillers, an adequate method offering a good compromise between suitable resolution and observable volume must be selected. Different polypropylene composites filled with long glass fibres, mica and talcum particles were investigated. Four methods were applied to account for the different filler sizes. For composites containing fillers larger than several micrometers, i.e. glass fibres and mica particles, X-ray tomography offers a very good combination of visibility and volume. Serial sectioning by polishing in combination with light optical microscopy can be an alternative if no X-ray equipment is available. This combined method has the disadvantage, however, that the imaged volume is smaller and involves more effort, which makes it unsuitable for routine observations. The much smaller talcum particles with thicknesses down to 200 nm were investigated by coupling focused ion beam (FIB) milling and scanning electron microscopy (SEM) and by insitu ultramicrotomy in the SEM. Both methods led to good and comparable results