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On-demand source of entangled photon-pairs using the biexciton-exciton radiative cascade


  Roni Winik[1,2]  ,  D. Cogan[1]  ,  Y. Don[1]  ,  I. Schwartz[1]  ,  L. Gantz[1]  ,  E. R. Schmidgall[1]  ,  N. Livneh[3]  ,  R. Rapaport[3]  ,  E. Buks[1,2]  ,  D. Gershoni[1]  
 [1] The Physics Department and the Solid State Institute, Technion--Israel Institute of Technology, 32000 Haifa, Israel
[2] Andrew and Erna Viterbi Department of Electrical Engineering, Technion, Haifa 32000 Israel
[3] Applied Physics Department, The Benin School of computer sciences and engineering, The Hebrew University, Jerusalem 91904 Israel

The ability to generate entangled photons on-demand is crucial for many future applications in quantum information processing. Devices based on the biexciton-exciton radiative cascade in single semiconductor quantum dots are considered to be the best candidate for these applications [1, 2, 3]. The ability to deterministically excite the biexciton using the two-photon absorption resonance [4] makes this avenue even more promising. A remaining challenge, however, is the excitonic fine structure, which splits the two exciton eigenstates thus providing spectral "which-path" information on the radiative cascade and preventing the pairs of emitted photons from being polarization entangled [2].

We present a novel study of a planar microcavity embedded single semiconductor quantum dot, resonantly excited by a п-area pulse to a biexciton two photon absorption resonance. The resulting pairs of biexciton and exciton photons are detected by two superconducting detectors synchronized to the exciting laser pulse. By performing time resolved polarization tomography of the two emitted photons, we show that they remain polarization entangled during the whole radiative decay. Our measurements provide simple ways for using a single quantum dot with a non-vanishing excitonic fine structure splitting as a reliable on demand source of polarization entangled photon pairs. 

 

[1] Benson et al. "Regulated and entangled photons from a single quantum dot" PRL 84, 2513 (2000)

[2] Akopian et al. "Entangled photon pairs from semiconductor quantum dot" PRL 84 96, 130501 (2006)

[3] Dousse et al. "Ultrabright source of entangled photon pairs." Nature 466, 217 (2010)

[4] Müller, et al. "On-demand generation of indistinguishable polarization-entangled photon pairs." Nature Photonics 8, 224 (2014)