Institute of Semiconductor and Solid State Physics, Johannes Kepler University , Linz 4040, Austria.
Department of Applied Physics, Royal Institute of Technology , Stockholm 106 91, Sweden.
Nano Lett. 2017 Jul 12;17(7):4090-4095. doi: 10.1021/acs.nanolett.7b00777. Epub 2017 Jun 7.
Photonic quantum technologies are on the verge of finding applications in everyday life with quantum cryptography and quantum simulators on the horizon. Extensive research has been carried out to identify suitable quantum emitters and single epitaxial quantum dots have emerged as near-optimal sources of bright, on-demand, highly indistinguishable single photons and entangled photon-pairs. In order to build up quantum networks, it is essential to interface remote quantum emitters. However, this is still an outstanding challenge, as the quantum states of dissimilar "artificial atoms" have to be prepared on-demand with high fidelity and the generated photons have to be made indistinguishable in all possible degrees of freedom. Here, we overcome this major obstacle and show an unprecedented two-photon interference (visibility of 51 ± 5%) from remote strain-tunable GaAs quantum dots emitting on-demand photon-pairs. We achieve this result by exploiting for the first time the full potential of a novel phonon-assisted two-photon excitation scheme, which allows for the generation of highly indistinguishable (visibility of 71 ± 9%) entangled photon-pairs (fidelity of 90 ± 2%), enables push-button biexciton state preparation (fidelity of 80 ± 2%) and outperforms conventional resonant two-photon excitation schemes in terms of robustness against environmental decoherence. Our results mark an important milestone for the practical realization of quantum repeaters and complex multiphoton entanglement experiments involving dissimilar artificial atoms.
光子量子技术正处于将量子加密和量子模拟器应用于日常生活的边缘。已经进行了广泛的研究来识别合适的量子发射器，并且单外延量子点已经成为明亮、按需、高度可分辨的单光子和纠缠光子对的近乎最佳源。为了建立量子网络，必须接口远程量子发射器。然而，这仍然是一个突出的挑战，因为不同的“人工原子”的量子态必须以高保真度按需制备，并且生成的光子必须在所有可能的自由度中具有不可分辨性。在这里，我们克服了这个主要障碍，并展示了来自远程应变可调 GaAs 量子点的前所未有的双光子干涉（51 ± 5%的可见度），这些量子点按需发射光子对。我们通过首次利用一种新的声子辅助双光子激发方案的全部潜力来实现这一结果，该方案允许生成高度可分辨的（71 ± 9%的可见度）纠缠光子对（90 ± 2%的保真度），能够实现一键式双激子态制备（80 ± 2%的保真度），并且在稳健性方面优于传统的共振双光子激发方案对抗环境退相干。我们的结果标志着实现量子中继器和涉及不同人工原子的复杂多光子纠缠实验的实际应用的重要里程碑。
