Zeeshan M, Sherlekar N, Ahmadi A, Williams R L, Reimer M E
Institute for Quantum Computing and Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada.
Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, Waterloo, N2L 3G1, Canada.
Phys Rev Lett. 2019 Jun 7;122(22):227401. doi: 10.1103/PhysRevLett.122.227401.
Entangled photon sources are crucial for quantum optics, quantum sensing, and quantum communication. Semiconductor quantum dots generate on-demand entangled photon pairs via the biexciton-exciton cascade. However, the pair of photons are emitted isotropically in all directions, thus limiting the collection efficiency to a fraction of a percent. Moreover, strain and structural asymmetry in quantum dots lift the degeneracy of the intermediate exciton states in the cascade, thus degrading the measured entanglement fidelity. Here, we propose an approach for generating a pair of entangled photons from a semiconductor quantum dot by application of a quadrupole electrostatic potential. We show that the quadrupole electric field corrects for the spatial asymmetry of the excitonic wave function for any quantum dot dipole orientation and fully erases the fine-structure splitting without compromising the spatial overlap between electrons and holes. Our approach is compatible with nanophotonic structures such as microcavities and nanowires, thus paving the way towards a deterministic source of entangled photons with high fidelity and collection efficiency.
纠缠光子源对于量子光学、量子传感和量子通信至关重要。半导体量子点通过双激子 - 激子级联产生按需纠缠光子对。然而，这对光子在所有方向上各向同性发射，从而将收集效率限制在百分之几的水平。此外，量子点中的应变和结构不对称消除了级联中中间激子态的简并性，从而降低了测量的纠缠保真度。在此，我们提出一种通过施加四极静电势从半导体量子点产生一对纠缠光子的方法。我们表明，四极电场可校正任何量子点偶极取向的激子波函数的空间不对称性，并完全消除精细结构分裂，而不会损害电子与空穴之间的空间重叠。我们的方法与诸如微腔和纳米线等纳米光子结构兼容，从而为实现具有高保真度和收集效率的确定性纠缠光子源铺平了道路。
