Observation of entanglement between a quantum dot spin and a single photon

摘要

未来的量子网络将把处于静止状态的量子位rn(如单电子自旋)与“飞行”的量子位(在远距rn离量子位之间转移量子态的光子)理想地结合rn在一起。因此，量子计算和通信领域一个长期rn未能解决的挑战便是，在一个固体平台上将一rn个单电子自旋耦合到一个单光子上。现在，两rn个独立工作的小组通过演示束缚在一个半导体rn“量子点”结构中的一个光子和一个单电子自rn旋之间的纠缠实现了这一目标。该量子点起静rn止节点的作用。这一成果是向最终实现能够进rn行远距离量子通信的量子网络的目标所迈出的rn一小步。%Entanglement has a central role in fundamental tests of quantum mechanics as well as in the burgeoning field of quantum information processing. Particularly in the context of quantum networks and communication, a main challenge is the efficient generation of entanglement between stationary (spin) and propagating (photon) quantum bits. Here we report the observation of quantum entanglement between a semiconductor quantum dot spin and the colour of a propagating optical photon. The demonstration of entanglement relies on the use of fast, single-photon detection, which allows us to project the photon into a superposition of red and blue frequency components. Our results extend the previous demonstrations of single-spin/single-photon entanglement in trapped ions, neutral atoms and nitrogen-vacancy centres to the domain of artificial atoms in semiconductor nanostructures that allow for on-chip integration of electronic and photonic elements. As a result of its fast optical transitions and favourable selection rules, the scheme we implement could in principle generate nearly deterministic entangled spin-photon pairs at a rate determined ultimately by the high spontaneous emission rate. Our observation constitutes a first step towards implementation of a quantum network with nodes consisting of semiconductor spin quantum bits.