2016/06/23 by Ido Schwartz, Dan Cogan, Emma R. Schmidgall +5 · 3 citations
Physics and Astronomy · #quant-ph
paper · pdf · doi:10.1126/science.aah4758
11 pages, 4 figures; supporting material is attached at the end of the main paper
arxiv created 2016/06/23 · arxiv updated 2016/09/09
We use semiconductor quantum dots, "artificial atoms," to implement a scheme for deterministic generation of long strings of entangled photons in a cluster state, an important resource for quantum information processing. We demonstrate a prototype device which produces strings of a few hundred photons in which the entanglement persists over 5 sequential photons. The implementation follows a proposal by Lindner and Rudolph (Phys. Rev. Lett. 2009) which suggested periodic timed excitation of a precessing electron spin as a mechanism for entangling the electron spin with the polarization of the sequentially emitted photons. In our realization, the entangling qubit is a quantum dot confined dark exciton. By performing full quantum process tomography, we obtain the process map which fully characterizes the evolution of the system, containing the dark exciton and n photons after n applications of the periodic excitations. Our implementation may greatly reduce the resources needed for quantum information processing.