Toshiba Research Europe Limited, Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ, UK.
1] Toshiba Research Europe Limited, Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ, UK [2] Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.
Nat Commun. 2014;5:3316. doi: 10.1038/ncomms4316.
Quantum networks can interconnect remote quantum information processors, allowing interaction between different architectures and increasing net computational power. Fibre-optic telecommunications technology offers a practical platform for routing weakly interacting photonic qubits, allowing quantum correlations and entanglement to be established between distant nodes. Although entangled photons have been produced at telecommunications wavelengths using spontaneous parametric downconversion in nonlinear media, as system complexity increases their inherent excess photon generation will become limiting. Here we demonstrate entangled photon pair generation from a semiconductor quantum dot at a telecommunications wavelength. Emitted photons are intrinsically anti-bunched and violate Bell's inequality by 17 standard deviations High-visibility oscillations of the biphoton polarization reveal the time evolution of the emitted state with exceptional clarity, exposing long coherence times. Furthermore, we introduce a method to evaluate the fidelity to a time-evolving Bell state, revealing entanglement between photons emitted up to 5 ns apart, exceeding the exciton lifetime.
量子网络可以将远程量子信息处理器相互连接，允许不同架构之间的交互，并增加网络计算能力。光纤电信技术为路由弱相互作用的光子量子比特提供了一个实用的平台，允许在远程节点之间建立量子相关性和纠缠。尽管使用非线性介质中的自发参量下转换在电信波长处产生了纠缠光子，但随着系统复杂性的增加，其固有的额外光子产生将成为限制因素。在这里，我们展示了在电信波长处从半导体量子点产生的纠缠光子对。发射光子本质上是反聚束的，并通过 17 个标准差违反贝尔不等式。双光子极化的高可见度振荡揭示了发射态的时间演化，具有异常清晰的清晰度，暴露了长相干时间。此外，我们引入了一种评估与时间演化的贝尔态保真度的方法，揭示了相隔长达 5 ns 的光子之间的纠缠，超过了激子寿命。
