Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada.
School of Engineering, University of Glasgow, Glasgow, G12 8QQ, Scotland, UK.
Sci Rep. 2017 Jul 19;7(1):5785. doi: 10.1038/s41598-017-06010-8.
Photonic-based qubits and integrated photonic circuits have enabled demonstrations of quantum information processing (QIP) that promises to transform the way in which we compute and communicate. To that end, sources of polarization-entangled photon pair states are an important enabling technology. However, such states are difficult to prepare in an integrated photonic circuit. Scalable semiconductor sources typically rely on nonlinear optical effects where polarization mode dispersion (PMD) degrades entanglement. Here, we directly generate polarization-entangled states in an AlGaAs waveguide, aided by the PMD and without any compensation steps. We perform quantum state tomography and report a raw concurrence as high as 0.91 ± 0.01 observed in a 1,100-nm-wide waveguide. The scheme allows direct Bell state generation with an observed maximum fidelity of 0.90 ± 0.01 from another (800-nm-wide) waveguide. Our demonstration paves the way for sources that allow for the implementation of polarization-encoded protocols in large-scale quantum photonic circuits.
基于光子的量子比特和集成光子电路已经实现了量子信息处理（QIP）的演示，有望改变我们的计算和通信方式。为此，偏振纠缠光子对态的源是一项重要的使能技术。然而，这种状态很难在集成光子电路中制备。可扩展的半导体源通常依赖于非线性光学效应，其中偏振模色散（PMD）会降低纠缠度。在这里，我们在 AlGaAs 波导中直接生成偏振纠缠态，借助 PMD 而无需任何补偿步骤。我们进行了量子态层析成像，并报告了在 1100nm 宽的波导中观察到的高达 0.91±0.01 的原始纠缠度。该方案允许直接生成贝尔态，从另一个（800nm 宽）波导观察到的最大保真度为 0.90±0.01。我们的演示为在大规模量子光子电路中实现偏振编码协议的光源铺平了道路。
