We report an experimental demonstration of the distribution of time-bin entangled photon pairs over 100 km of optical fiber. In our experiment, 1.5-mum non-degenerated time-bin entangled photon pairs were generated with a periodically poled lithium niobate (PPLN) waveguide by using the parametric down conversion process. Combining this approach with ultra-low-loss filters to eliminate the pump light and separate signal and idler photons, we obtained an efficient entangled photon pair source. To detect the photons, we used single-photon detectors based on frequency up-conversion. These detectors operated in a non-gated mode so that we could use a pulse stream of time correlated entangled photon pairs at a high repetition frequency (1 GHz). Using these elements, we distributed time-bin entangled photon pairs over 100 km of dispersion shifted fiber and performed a two-photon interference experiment. We obtained a coincidence fringe of 81.6% visibility without subtracting any background noise, such as accidental coincidence or dark count, which was good enough to violate Bell's inequality. Thus, we successfully distributed time-bin entangled photon pairs over 100 km.
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http://dx.doi.org/10.1364/oe.15.013957 | DOI Listing |
J Phys Chem A
January 2025
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
Given their molecular properties and electronic structure, graphyne and graphdiyne are promising materials with numerous applications in different fields of material science. Dehydrobenzoannules (DBAs) are candidates that can serve as building blocks for synthesizing and designing new 2D carbon allotropes; however, only a few graphynes have been produced on a practical scale. Herein, we present our investigation of three DBAs, which serve as a model to understand the relationship between the structure and property, contributing to 2D carbon allotropes' rational design and synthetic effort.
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December 2024
QuTech and Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands.
Direct interactions between quantum particles naturally fall off with distance. However, future quantum computing architectures are likely to require interaction mechanisms between qubits across a range of length scales. In this work, we demonstrate a coherent interaction between two semiconductor spin qubits 250 μm apart using a superconducting resonator.
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January 2025
Xanadu Quantum Technologies Inc., Toronto, Ontario, Canada.
Photonics offers a promising platform for quantum computing, owing to the availability of chip integration for mass-manufacturable modules, fibre optics for networking and room-temperature operation of most components. However, experimental demonstrations are needed of complete integrated systems comprising all basic functionalities for universal and fault-tolerant operation. Here we construct a (sub-performant) scale model of a quantum computer using 35 photonic chips to demonstrate its functionality and feasibility.
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National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing 210093, China.
Entangled photon-pair sources are pivotal in various quantum applications. Miniaturizing the quantum devices to meet the requirement in limited space applications drives the search for ultracompact entangled photon-pair sources. The rise of two-dimensional (2D) semiconductors has been demonstrated as ultracompact entangled photon-pair sources.
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January 2025
State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China; Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China. Electronic address:
Hybrid continuous-variable (CV) and discrete-variable (DV) entanglement is an essential quantum resource of hybrid quantum information processing, which enables one to overcome the intrinsic limitations of CV and DV quantum protocols. Besides CV and DV quantum variables, introducing more degrees of freedom provides a feasible approach to increase the information carried by the entangled state. Among all the degrees of freedom of photons, orbital angular momentum (OAM) has potential applications in enhancing the communication capacity of quantum communication and precision of quantum measurement.
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